changes in optical properties chemistry and micropore and mesopore characteristics of bituminous coal at the contact with dikes in the illinois basin abstract changes in high volatile bituminous coal pennsylvanian near contacts with two volcanic intrusions in illinois were investigated with respect to optical properties coal chemistry and coal pore structure vitrinite reflectance ro increases from 0 62 to 5 03 within a distance of 5 5 m from the larger dike and from 0 63 to 3 71 within 3 3 m from the small dike elemental chemistry of the coal shows distinct reductions in hydrogen and nitrogen content close to the intrusions no trend was observed for total sulfur content but decreases in sulfate content towards the dikes indicate thermochemical sulfate reduction tsr contact metamorphism has a dramatic effect on coal porosity and microporosity in particular around the large dike the micropore volume after a slight initial increase progressively decreases from 0 0417 cm3 g in coal situated 4 7 m from the intrusive contact to 0 0126 cm3 g at the contact strongly decreasing mesopore and micropore volumes in the altered zone together with frequent cleat and fracture filling by calcite indicate deteriorating conditions for both coalbed gas sorption and gas transmissibility

insights from rock eval analysis on the influence of sample weight on hydrocarbon generation from lower permian organic matter rich rocks west bokaro basin india abstract among the different rock eval parameters the hydrocarbons released under the s2 peak of rock eval is of significance as it indicates the residual hydrocarbon content of the rock further through its relationship with total organic carbon toc content it helps in calculating hydrogen indices hi which helps in understanding the type of organic matter present in a rock hi s2 toc 100 the present study documents the role of sample weight amount used for analysis on the rock eval s2 parameter for unconventional source rock characterization for the purpose of this study a vitrain band sample type manually isolated from a coal a high toc shale sample type and a carbonaceous shale sample type were analyzed at two different particle sizes viz 1 mm 500 m and 212 75 m and different sample weights 5 15 mg for organic matter rich rocks and 30 60 mg for shale using a rock eval basic cycle heating rate at 25 c min although s2 is reported as mg hydrocarbon hc g rock with increase in sample weight an increase in hydrocarbons released under the s2 peak of rock eval was observed for all three sample types for both the particle sizes the observations were further validated using a norwegian geochemical standard jr 1 further all samples were reanalyzed by conducting pyrolysis experiments at a lower heating rate of 5 c min the impact of sample weight on s2 and hi was observed to be more pronounced for the jr 1 standard higher hydrocarbon yield than the van krevelen types iii iv organic matter bearing rocks it thus calls for interpreters to be aware of the influence of mass of organic matter on hydrocarbon generation and to monitor the maximum s2 values of organic matter bearing rocks within the flame ionization detector fid detection limits further it is recommended that for type iii organic matter bearing rocks with toc content 20 wt elemental analysis should be used to derive atomic h c and o c ratios for van krevelen diagram based kerogen typing

mercury as a proxy for volcanic emissions in the geologic record abstract large igneous province lip eruptions are increasingly considered to have driven mass extinction events throughout the phanerozoic however uncertainties in radiometric age dating of lip materials along with difficulty in accurate age dating of sedimentary rocks that record the environmental and biological history of our planet create inherent uncertainties in any linkage as such there is interest in using geochemical proxies to fingerprint periods of major volcanism in the sedimentary record termed here lip marks the use of sedimentary mercury hg contents has been suggested to be the best tool to accomplish this goal and recent work is reviewed here studies to date show that most extinction events ocean anoxic events and other environmental crises through the phanerozoic have an associated sedimentary hg anomaly it remains unclear though if each hg anomaly is truly a signature of massive volcanism or if it is controlled by local or regional processes as hg has a strong affinity to organic matter om normalisation with total organic carbon toc has been used to assess anomalies the measurement of toc has been fraught with error throughout many studies leaving some claimed hg toc anomalies questionable normalisation by other elements that can affect hg sequestration such as al and s are less common but warrant further investigation stable isotope systematics of hg have helped to further clarify the origin of hg spikes and clearly show that not all hg anomalies are directly related to volcanism although a promising tool the hg proxy requires more refinement to accurately understand the nuances of an hg anomaly in the rock record

graptolites as indicators of the temperature histories of rocks a pilot study of the optical properties of graptolite skeletal materials shows progressive changes of reflectance bireflectance refractive index and absorptive index produced by temperature changes related to depth of burial samples of lower ordovician to upper silurian graptolites were selected from across canada from locations where the conodont alteration indices of adjacent conodont collections provide a control index of temperature the reaction to temperature of graptolite skeletal material appears to be similar to that of bitumen but somewhat different to that of the vitrinite and liptinite maceral components of coal maximum reflectance in oil and bireflectance appear to be the characteristics most diagnostic of maximum temperature and both show progressively higher rates of increase at higher temperatures these factors show potential for more sensitive discrimination of temperatures at high levels of conodont alteration indices the optical properties of graptolites may perhaps provide a useful tool for unravelling the post depositional histories of lower palaeozoic rocks in deformed belts

the silurian qusaiba hot shales of saudi arabia an integrated assessment of thermal maturity abstract the lower silurian qusaiba hot shales qhs are proven source rocks for oil within the paleozoic and possibly some of the mesozoic reservoirs in saudi arabia moreover these shales have oil shale potential where they are immature and shallow enough for mining as well as unconventional shale oil and shale gas potential in areas where they are within oil maturity and gas maturity levels respectively the qhs were deposited in relatively shallow marine environments under anoxic water conditions resulting in accumulation of amorphous kerogen organic walled graptolites and acritarchs across the arabian basin organic matter quality does not show much variation for the qhs but the maturity varies greatly as a result of varying burial history thermal maturity assessment of shale source rocks that lack vitrinite such as the qusaiba hot shales continues to be challenging especially where conflicting measurements are obtained from different sources this paper presents an integrated assessment of qhs thermal maturity parameters based on cores from 13 carefully selected boreholes that based on regional basin models are believed to cover a wide maturity range ca 0 5 to 2 0 ro we conducted some analyses on kerogen maceral petrography graptolite reflectance uv fluorescence whole rock pyrolysis raman spectroscopy of graptolite and other analyses on bitumen extracts gc and gc ms of saturate and aromatic fractions and ftir spectroscopy of the asphaltene fraction we show that using many thermal maturity parameters reduces uncertainty significantly and we therefore recommend that graptolite reflectance analyses should be conducted in support of other maturity indicators proper reflectivity measurements of the graptolites set the reference for comparison of other maturity parameters obtained from petrographic geochemical and spectroscopic techniques our work provides a template by which qusaiba thermal maturity can be more accurately estimated when only a limited set of maturity parameters is available

a new approach to interpreting rock eval s2 and toc data for kerogen quality assessment abstract a simple method for application in source potential mapping is used to assess the original oil and gas potentials in source rock horizons based upon rock eval potential s 2 and total organic carbon toc values the method assumes that kerogens consist of mixtures of end members with assigned hydrogen index values based on suggested algorithms the average amounts of oil prone gas prone and inert organic material over source rock intervals are determined in toc units the method uses regression lines from plots of remaining hydrocarbon potentials s 2 versus total organic carbon toc and quick look transparent overlays are used to read the appropriate kerogen mixture mineral matrix effects during pyrolysis when strong can cause erroneous results this effect which occurs for oil prone kerogens and adsorptive minerals can cause problems particularly for lean samples s 2 0 3 mg hc g rock whilst the errors for richer samples are less the method is applied on three sections of upper jurassic organic rich rocks from the danish north sea sector which are at different maturity stages one of these sections is dominated by gas prone material one is dominated by oil prone material and the third section contains a mixture of oil and gas prone material the method has been compared with other methods that split kerogens in oil and gas generating potential and has given reasonable results experience using the method and a presented example suggest that sedimentological system tract information may be derived from s 2 to toc cross plots a constructed modelling example suggests that the end member concept used in this approach may be used in forward type source rock prediction models when combined with sedimentological models the resulting s 2 toc plots can be used in order to check the forward modelling results against observed values

characterization of geochemical properties and microstructures of the bakken shale in north dakota abstract research on unconventional shale reservoirs has increased dramatically due to the decline of production from conventional reserves geochemical properties and pore microstructures are known to be important factors that affect the storage capacity and nano mechanical properties of self sourced organic rich shales in this study eleven shale samples were collected from the upper and lower members of the bakken formation for the analysis of mineralogy geochemical properties and pore structure bulk pyrolysis analysis was conducted using the default method and two modified methods namely the reservoir and the shale reservoir methods although all three methods showed the bakken samples to be organic rich and to have considerable remaining hydrocarbon generating potential it was the shale reservoir method that gave the highest hydrocarbons yield because it captured most of the lighter thermo vaporizable hydrocarbons thus the shale method is considered to be more appropriate for the geochemical analysis of the bakken samples this method also showed that most of the remaining potential is due to the cracking of heavy hydrocarbons nso compounds resins asphaltenes and kerogen the organic matter in the samples is mixed ii iii type oil and gas prone is thermally mature and plots at the peak of the oil window the vro eq values based on solid bitumen ro measurements and conversion ranged from 0 85 to 0 98 the pore structures obtained from the image analysis method showed that total surface porosity of the samples ranged from 3 89 to 11 56 and that organic porosity is not the main contributor of total porosity for the samples analyzed the pore structures of the samples are heterogeneous due to differences in lacunarity values results of the impact of mineralogical composition on pore structures demonstrate that clay minerals and feldspar have a positive influence on porosity while quartz pyrite and that toc has a negative impact

characteristics of type iii kerogen in coal bearing strata from the pennsylvanian upper carboniferous in the ruhr basin western germany comparison of coals dispersed organic matter kerogen concentrates and coal mineral mixtures abstract quality quantity and maturity of coal and dispersed terrigenous organic matter were studied on six coal bearing intervals in duckmantian strata pennsylvanian upper carboniferous of the ruhr basin western germany between 10 and 40 samples were collected from fresh drill cores of each interval typically consisting of a coal seam as well as clastic roof and floor strata sandstone siltstone claystone coal seams constitute about 8 vol of the succession studied the samples were analysed by organic petrological methods and rock eval pyrolysis maturity expressed in terms of vitrinite reflectance is between 0 75 and 1 0 for the six successions studied the total amount of dispersed organic matter in clastic rocks is about half of that stored in coal seams both containing predominantly vitrinite significant differences between rock eval parameters determined on whole rock samples and kerogen concentrates were observed especially with respect to hydrogen index hi values thus the hi of the coal is about twice as high as that of the dispersed organic matter although the maceral composition is similar the effects of minerals were further examined by rock eval pyrolysis of artificial mixtures of coal lignite powder and different minerals reduced hi values are partly explained by the retention of generated hydrocarbons on mineral surfaces and partly by reactions of generated fluids with pyrite in kerogen concentrates

standardization of reflectance measurements in dispersed organic matter results of an exercise to improve interlaboratory agreement vitrinite reflectance generally is considered the most robust thermal maturity parameter available for application to hydrocarbon exploration and petroleum system evaluation however until 2011 there was no standardized methodology available to provide guidelines for vitrinite reflectance measurements in shale efforts to correct this deficiency resulted in publication of astm d7708 standard test method for microscopical determination of the reflectance of vitrinite dispersed in sedimentary rocks i n 2012e2013 an interlaboratory exercise was conducted to establish precision limits for the d7708 measurement

change in the magnetic properties of bituminous coal intruded by an igneous dike dutch creek mine pitkin county colorado abstract magnetization measurements have been made on natural coke coal samples collected at various distances from a felsic porphyry dike in a coal seam in dutch creek mine colorado to help characterize the nature and distribution of the iron bearing phases the magnetization passes through a maximum at the coke to coal transition about 31 cm from the dike contact the magnetic measurements support the geochemical data indicating that magmatic fluids along with a high temperature gas pulse moved into the coal bed interaction of the magmatic fluids with the coal diminished the reducing power of the thermal gas pulse from the dike to a point about 24 cm into the coal the hot reducing gas penetrated further and produced a high temperature 400 525 c zone at about 31 cm just ahead of the magmatic fluids metallic iron found in this zone is the principal cause of the observed high magnetization beyond this zone the temperature was too low to alter the coal significantly

a revised method for reconstructing the hydrocarbon generation and expulsion history and evaluating the hydrocarbon resource potential example from the first member of the qingshankou formation in the northern songliao basin northeast china abstract reconstructing the hydrocarbon generation and expulsion history of source rocks is an essential part of evaluating the hydrocarbon resource potential by genetic method the hydrocarbon generation potential method is an efficient tool for quantifying the hydrocarbon generation and expulsion characteristics of source rock and evaluating the hydrocarbon resource potential based on rock eval data although various revised versions of the method are publicly available the following problems remain to be resolved a the method is subjective b implicit limitations are observed and c rock mass loss is not considered which may result in unacceptable errors in this study we propose a revised hydrocarbon generation potential method expressions for calculating the original rock mass go original total organic carbon toco transformation ratio tr hydrocarbon expulsion ratio er and hydrocarbon expulsion efficiency f were developed and incorporated into the hydrocarbon generation and expulsion history reconstruction and hydrocarbon resource potential evaluation and these expressions combined conventional and unconventional resource evaluations systematically with objective and accurate results the first member of the qingshankou formation k2qn1 in the northern songliao basin northeast china was used as an example to demonstrate the application of the proposed method the results have been compared with the unrevised method using the same rock eval data sets and verified with previous reports to demonstrate its reliability the results also indicate that the hydrocarbon generation threshold hgt and hydrocarbon expulsion threshold het of k2qn1 are ro 0 4 and ro 0 6 respectively three hydrocarbon generation and expulsion peak stages were identified k2n 81 74 ma k2m 74 66 ma and n2t 66 0 ma the hydrocarbon generation and expulsion centers of k2qn1 are mainly the qijia gulong sag and sanzhao sag the resource potentials of conventional oil unconventional tight oil and shale oil associated with k2qn1 source rocks in the northern songliao basin are 8 15 108 t 22 97 108 t and 62 1 108 t respectively

influence of petrographical composition on coking behavior of inertinite rich coals abstract medium rank inertinite rich coal samples were collected for study from limnic and paralic facies in the upper silesian coal basin of poland the microlithotypes seem to control the content of the mosaic textures it also appears that carbominerites favor the formation of pyrolytic carbons the coke obtained from poorly pyrofusinitized homogeneous limnic coal has higher mechanical strength with larger and thicker cell walls and is less porous than those derived from highly pyrofusinitized heterogenous paralic ones the microstructure of the cokes appears to be controlled by different amounts of fibers and coarse mosaics

hydrocarbon potential and depositional paleoenvironment of a middle jurassic succession in the falak 21 well shushan basin egypt integrated palynological geochemical and organic petrographic approach abstract the topmost lower and middle jurassic formations of organic rich clastics with minor carbonate deposits were recognized as very significant source reservoir rocks in the north western desert of egypt although several studies are devoted to their source rock characteristics and petroleum potential the depositional paleoenvironment and paleoredox conditions are still poorly understood in the current study these sediments were assessed in terms of their organic matter richness hydrocarbon generative potential and thermal maturity total sulfur ts contents and organic petrographic characteristics depositional paleoenvironment was investigated using dinoflagellate cysts dinocysts and the composition of particulate organic matter along with organic petrographic characteristics redox conditions were assessed based on ts total organic carbon toc relationship and type of kerogen that was derived mainly from palynofacies analysis toc contents show fair to excellent generative potential of hydrocarbons mainly of kerogen type iii gas prone the thermal maturity based on tmax and rr indicates mature stage of oil window palynological analysis yielded poor to rich intervals of moderately preserved biostratigraphically useful dinocysts in the upper part of the khatatba formation an assemblage of 81 species belonging to 54 genera of moderately diverse dinocysts spores and pollen grains was identified freshwater algae acritarchs and microforaminiferal test linings are sporadically documented within the studied interval based on the first downhole appearance fda of the recovered marker dinocyts the upper part of the khatatba formation was palynologically dated as late bathonian callovian the depositional environment was interpreted and three environments were deduced the lower interval representing the topmost ras qattara and yakout red shale member was deposited in a fluvial lacustrine environment where oxic conditions prevailed as deduced from the color of reddish brown sandstone and red shale the middle interval spans unit iib kabrit and unit iii which accumulated in a deltaic to shallow marine environment under dysoxic suboxic settings the upper interval covers unit i and unit iia that have been deposited in a fluvio deltaic to shallow marine with high paleoproductivity under suboxic conditions one sample in the upper interval in unit iia reflected anoxic setting

guidelines for assessing the petroleum potential of coaly source rocks using rock eval pyrolysis abstract coaly source rocks are sufficiently different from marine and lacustrine source rocks in their organic matter characteristics to warrant separate guidelines for their assessment using rock eval pyrolysis the rank threshold for oil generation is indicated by the increase in bi s1 toc at rank sr 9 10 tmax 420 430 c ro 0 55 0 6 and the threshold for oil expulsion is indicated by the peak in qi s1 s2 toc at rank sr 11 12 5 tmax 430 440 c ro 0 65 0 85 the pronounced rank related increase in hi s2 toc prior to oil expulsion renders the use of immature samples inappropriate for source rock characterisation a more realistic indication of the petroleum generative potential and oil expulsion efficiency of coaly source rocks can be gained from samples near the onset of expulsion alternatively effective hi values i e his near the onset of expulsion can be estimated by translating the measured his of immature samples along the maturation pathway defined by the new zealand or other defined coal band coaly source rocks comprise a continuum of coaly lithologies including coals shaly coals and coaly mudstones determination of the total genetic potential of coaly source rock sequences is best made using lithology based samples near the onset of expulsion

rock eval tmax suppression documentation and amelioration the rock eval thermal maturation parameter tmax may occasionally be suppressed relative to surrounding rock units this is commonly assumed to result from either a bitumen contribution to the s2 peak or the presence of sulfur rich and hence thermally labile kerogen the phenomenon is frequently coincident with a high natural gamma ray signature and elevated rock eval hydrogen index hi and total organic carbon toc contents determination of thermal maturity of such units relies either on the interpolation of tmax from surrounding units or the direct estimation of the extent of suppression on a given sample the latter may be required if the available samples are restricted to conventional or sidewall core material representative of imited stratigraphic intervals the second white speckled shale part of the cretaceous colorado group in the alberta basin displays tmax suppression over part of its thickness a consistent relationship emerges from calculating a linear regression of tmax as a function of either toc or hi for several wells at different levels of thermal maturity below values of about 453 c late oil window tmax is suppressed by about 1 c for every increase in hi of 50 mg hydrocarbon g toc thus tmax suppression in the second white speckled shale can be corrected by extrapolating all tmax values to a constant hi of 100 to 150 mg hydrocarbon g toc values typical of type iii kerogen

geochemical truths in large data sets i geochemical screening data abstract organic geochemistry especially when undertaken on a well by well or outcrop by outcrop basis arguably lacks statistically significant numbers of analyses to establish reliable trends can a reliable vitrinite reflectance vs depth trend be established from say 12 analysed samples when the number of analysed samples are in the hundreds or even thousands much clearer general trends are established and anomalous measurements more readily recognised interpretation of anomalies is itself highly instructive but forms another paper in this paper a global data set of some 5000 source rock samples is assembled from the open literature and released data e g open file reports and the results discussed to produce practical oil industry interpretations from basic screening data a complex conclusion can be extracted from simple data sets and are supported by mass balance and kinetic theory it is concluded that interpretation always falls back on a comparison of new data with pre existing knowledge in the form of tables and plots total organic carbon toc values are generally log normally distributed so that using mean standard deviation values will under estimate the upside potential when fed into risked probabilistic hydrocarbon charge prediction models kerogen type is initially best determined using plots of rock eval s 2 vs toc rather than the hydrogen index hi s 2 toc vs oxygen index oi s 3 toc or pseudo van krevelen plot the intercept of the s 2 vs toc plot predicts the average dead carbon inertinite content of the source rock set with the slope corresponding to the hydrogen index of the labile component hi l maturity trends of the hydrogen index vs t max or r o show reversals at high maturities as supported by the kinetics of the thermal breakdown of the three standard kerogen types at elevated maturities type iii kerogens have higher hydrogen indices than types i and ii kerogens a feature that must be taken into account when correcting mature kerogens to their original hi values hi o the reduction in hydrogen index is a measure of generation with the corresponding increase in production index pi s 1 s 1 s 2 being effectively a measure of hydrocarbon retention a cross plot of hi vs pi can be interpreted in terms of expulsion efficiencies expelled generated minus retained hydrocarbon measured data support a pore saturation and or generation pressure driven process for expulsion and indicate a limiting pore saturation equivalent to a production index of 0 6 for rich 2 toc source rocks

thermal maturity source rock potential and kinetics of hydrocarbon generation in permian shales from the damodar valley basin eastern india abstract this study investigates the source rock characteristics of permian shales from the jharia sub basin of damodar valley in eastern india borehole shales from the raniganj barren measure and barakar formations were subjected to bulk and quantitative pyrolysis carbon isotope measurements mineral identification and organic petrography the results obtained were used to predict the abundance source and maturity of kerogen along with kinetic parameters for its thermal breakdown into simpler hydrocarbons the shales are characterized by a high toc 3 4 mature to post mature heterogeneous type ii iii kerogen raniganj and barren measure shales are in mature late oil generation stage rr raniganj 0 99 1 22 rr barren measure 1 1 1 41 vitrinite is the dominant maceral in these shales barakar shows a post mature kerogen in gas generation stage rr barakar 1 11 2 0 and consist mainly of inertinite and vitrinite the 13corg value of kerogen concentrate from barren measure shale indicates a lacustrine marine origin 24 6 30 84 vs vpdb and that of raniganj and barakar 22 72 25 03 vs vpdb show the organic provenance to be continental the 13c ratio of thermo labile hydrocarbons c1 c3 in barren measure suggests a thermogenic source discrete bulk kinetic parameters indicate that raniganj has lower activation energies e 42 62 kcal mol compared to barren measure and barakar e 44 68 kcal mol temperature for onset 10 middle 50 and end 90 of kerogen transformation is least for raniganj followed by barren measure and barakar mineral content is dominated by quartz 42 63 siderite 9 15 and clay 14 29 permian shales in particular the barren measure as inferred from the results of our study demonstrate excellent properties of a potential shale gas system

evaluation of source rock potential matrix effect and applicability of gas oil ratio potential factor in paleocene eocene bituminous shales of camalan formation nallihan turkey abstract in order to improve the reliability and accuracy of source rock evaluation a total of 102 shale samples of camalan formation were collected analyzed and re characterized with taking matrix retention effect into account results from rock eval and visual kerogen analyses indicate 1 an excellent source rock with an average toc of 6 39 wt 2 an assemblage of amorphous i e alginite type i organic matter as a major organic constituent with an excellent potential for generating oil 3 shale samples from camalan formation are in immature early intermediate stage of maturity based on tmax avg 440 c and spore color index sci 2 5 4 also no amount of camalan generated oils are migrated out of shale based on s1 vs toc plot i e transformation ratio tr 0 samples of this study show a significant mineral matrix effect after correction of mineral matrix effect the average hydrogen index hi of the camalan formation increased by more than 60 mg hc g toc and reached to an average of 811 mg hc g toc gas oil ratio potential gorp factor were used in order to split up the toc and s2 into oil prone and gas prone and also to investigate the level of consistency between the results of gorp factor and those of visual kerogen studies based on obtained gorp factor more than 90 of toc live is composed from oil prone materials which is in acceptable agreement with petrographic assessments

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

direct evidence for organic carbon preservation as clay organic nanocomposites in a devonian black shale from deposition to diagenesis abstract the burial of marine sourced organic carbon oc in continental margin sediments is most commonly linked to oceanographic regulation of bottom water oxygenation anoxia and or biological productivity here we show an additional influence in the devonian woodford shale in which oc occurs as nanometer intercalations with specific phyllosilicate minerals mixed layer illite smectite that we term organo mineral nanocomposites high resolution transmission electron microscopic hrtem images provide direct evidence of this nano scale relationship while discrete micron scale organic particles such as tasmanites algal cysts are present in some lamina a strong relation between total organic carbon toc and mineral surface area msa over a range of 15 toc indicate that the dominant association of organic carbon is with mineral surfaces and not as discrete pelagic grains consistent with hrtem images of nanocomposites where periods of oxygenation are indicated by bioturbation this relationship is modified by a shift to lower oc loading on mineral surfaces and reduced msa variability likely resulting from biological mixing and homogenization of the sediment oxidative burn down of oc and or stripping of oc from minerals in animal guts the toc msa relationship extends across a range of burial depths and thermal maturities into the oil window and persists through partial illitization where illitization occurs the loss of mineral surface area associated with the collapse of smectite interlayer space results in a systematic increase in toc msa and reorganization of organic carbon and clays into nano scale aggregates while the woodford shale is representative of black shale deposits commonly thought to record heightened marine productivity and or anoxia our results point to the importance of high surface area clay minerals for oc enrichment given that the vast majority of these clay minerals are formed in soils before being transported to continental margin settings their mineralogy and attendant preservative potential is primarily a function of continental climate and provenance making these deposits a sensitive recorder of land as well as oceanographic change

organic geochemistry of dsdp site 467 offshore california middle miocene to lower pliocene strata abstract results of the analyses of twenty three samples from the middle miocene to lower pliocene strata from dsdp site 467 offshore california are presented the analyses were performed with the aim of determining the origin of the organic matter the stratigraphic section s hydrocarbon generation potential and extent of organic diagenesis organic carbon contents are an order of magnitude greater than those typically found in deep sea sediments suggesting an anoxic depositional environment and elevated levels of primary productivity hydrocarbon generation potentials are above average for most samples the results of elemental analyses indicate that the kerogens are primarily composed of type ii organic matter and are thermally immature analysis of the bitumen fractions confirms that the samples are immature in cores from 541 to 614 meters the gas chromatograms of the c 15 non aromatic hydrocarbon fractions are dominated by a single peak which was identified as 17 h 18 h 21 h 28 30 bisnorhopane this interval is the same area in which the highest degrees of anoxia are observed as reflected by the lowest pristane phytane ratios this correlation may have some implications with regard to the origin of the bisnorhopane and its possible use as an indicator of anoxic depositional conditions within thermally immature sediments

petrographic and geochemical characterization of organic rich mississippian black shales in the north of spain vegamian formation cantabrian zone abstract black shales 1 60 m thick with minor cherts radiolarites and phosphate nodules of mississippian age middle upper tournaisian vegamian formation occur in the fold and thrust belt of the cantabrian zone n spain at the base of the carboniferous succession which is infilling the variscan foreland basin the vegamian formation was accumulated in a similar sedimentary and paleogeographic context to the upper devonian carboniferous black shales of the appalachian arkoma fort worth western canada and antler foreland basins north america and to the variscan foreland basin in belgium and germany five stratigraphic sections were investigated in the southern branch of the cantabrian zone corresponding to the shallower sectors of the passive margin of the variscan foreland basin in n spain where this stratigraphic unit reaches a thickness of generally the organic matter is dominated by bitumen found either as diffuse masses or concentrated in spaces and cavities often parallel to the bedding planes or filling voids within calcite veins and fractures generally the bitumen masses are homogeneous without secondary porosity but occasionally they show mosaic optical texture indicating thermal transformation anastomosing structures likely related to bituminite are also common and exhibit a large range of reflectances autochthonous organic matter algae bacteria is seen as scarce tasmanites and liptodetrinite whereas allochthonous components vitrinite inertinite are also scarce except in the olleros section the range of reflectances of vitrinite like particles is similar to that of bitumen but the identification is uncertain and therefore the reflectance of bitumen brr has been used for thermal maturity assessment a gaussian like distribution of bitumen reflectances was found for la brana section brr 0 70 whereas a bimodal distribution was observed in olleros brr 0 70 and vegamian sections brr 0 95 and large scatter of readings in millaro brr 1 55 the vitrinite reflectance equivalent estimated from aromatic compounds indicates that most of the existing correlations between vitrinite and bitumen reflectances underestimate the maturity of the lowest reflecting sections and overestimate it in the highest reflecting one ts toc ratios the geochemistry of organic matter and spectral gamma ray measurements suggest a normal marine to dysoxic environment of deposition with only local anoxia at the base of the vegamian formation

integrated palynological organic geochemical and sequence stratigraphic analyses of the middle to upper cenomanian hydrocarbon reservoir source abu roash g member a depositional model in northwestern egypt abstract the current investigation provides further insight into the petroliferous characteristics of the abu roash g member which is regarded as an important rock unit for the egyptian oil industry forty seven samples covering the g member were selected from the bed 14 1 and bed 2 4 wells in the abu gharadig basin and from the abu tunis 1x well in the matruh basin both of which are located in the north western desert an independent dating of the g rocks of bed 2 4 by benthic foraminifera and ostracods in addition to palynological dating suggests a middle late cenomanian age and provides the biochronostratigraphic framework for the sequence stratigraphic analysis analysis of the vertical distribution of particulate organic matter defines three palynofacies types pf pf 1 represents the basal g where shales of the bed wells and calcareous shale of abu tunis 1x were deposited during a relative sea level rise in an outer middle shelf environment that experienced a notable high primary productivity prevailing reducing suboxic anoxic conditions supported preservation of very high amounts of amorphous organic matter aom in pf 1 pf 2 is equated to shales of the middle g of bed 14 1 and bed 2 4 and to calcareous shales and limestone of the upper g in abu tunis 1x pf 2 was deposited during a relative sea level fall in an inner middle shelf setting under better developed suboxic anoxic conditions pf 3 corresponds to the upper g of bed 14 1 and bed 2 4 and represents the shallowest setting where sandy and silty shales were deposited during a pronounced sea level fall in an inner shelf environment the same suboxic anoxic conditions were prevailing during deposition of pf 3 three bioevents were recorded which could be of palaeoecological and or biostratigraphic significance these are senegalinium aenigmaticum dinopterygium cladoides peak dinopterygium cladoides dinopterygium alatum peak and an acme of classopollis brasiliensis sequence stratigraphy of a transect of the four studied sections was carried out to understand the response of the particulate organic matter distribution and depositional system to the sea level changes three third order depositional genetic sequences were recognized and correlated with the global sea level curve kce 2 kce 3 and kce 4 the early highstand systems tract ehst of the genetically related kce 3 in all wells is characterized by relatively rich organic matter where combined remarkably low water circulation and insignificant dilution of organic matter with coarse terrigenous material probably supported good preservation of organic matter spatial distribution of the g rocks shows lateral facies changes this was inferred from sedimentation of an organic poor avg 0 8 toc wt coarse clastic sandy shales facies in the studied area in abu gharadig basin sedimentation changes laterally into a northeast and northwest organic rich finer clastic shale calcareous shales and argillaceous limestone facies in the western matruh basin the robust anoxic conditions and very low dilution of organic matter by terrigenous influx enhanced the organic richness avg 2 4 toc wt of these rocks which resulted in the formation of promising hydrocarbon source rocks thus for a successful hydrocarbon exploration in the north western desert the promising source section of the g member would be associated with shales calcareous shales and argillaceous limestone lithologies its depositional environment is mainly confined to outer middle and inner middle shelf settings that have widespread suboxic anoxic conditions and show ehst pattern in contrast the regressive intervals that are denoted by the lowstand systems tract lst and or the late hst lhst typify the relatively coarse clastics as good quality reservoir rocks that are characterized by poor organic richness due to dilution with terrigenous influx

palaeoenvironmental conditions for the preservation of organic matter during the late hauterivian in the neuquen basin western argentina abstract the agua de la mula member of the agrio formation comprises marine deposits accumulated in a mixed carbonate siliciclastic outer ramp during the late hauterivian an innovative multi proxy study that includes sedimentological geochemical and paleobiological data from the el porton section were combined in order to constrain the environmental context two major sedimentary cycles have been recognised tst hst reflecting the position of both distal and proximal sediments within the depositional system the distal outer ramp deposits fa1 are predominantly characterised by carbonate bearing mudstones with toc content up to 4 43 wt toc average 1 62 wt and type ii marine derived amorphous organic matter the high toc could be reflecting enhanced bioproductivity during periods of decreased salinity as mirrored by peaks of micrantholithus and reduced dilution by siliciclastic material in a distal setting conversely the proximal outer ramp succession fa2 shows a higher siliciclastic pattern along with the terrestrial organic matter signal type ii iii kerogen and toc content around 1 wt average 1 05 wt in this interval primary production is associated with more stable conditions and stratified water as reflected in peaks of nannoconus these conditions allowed a greater diversity and high abundances of calcareous nannofossil assemblages

palynomorph optical analyses for thermal maturity assessment of upper ordovician katian hirnantian rocks from southern estonia abstract application of integrated multi proxy optical analytical techniques for the assessment of thermal maturity of organic matter was tested in katian to hirnantian upper ordovician sediments from a subsurface succession in southern estonia the investigated valga 10 drill core section consists of a biostratigraphically well constrained succession deposited in the outer part of a carbonate shelf livonian basin the diverse and well preserved palynological assemblages permitted the analysis of thermally induced modifications of optical properties of small and large acanthomorph acritarchs qualitative methods such as uv fluorescence and acritarch alteration index aai were calibrated against the quantitative palynomorph darkness index pdi the occurrence of vitrinite like organoclasts allowed reflectance measurements in some of the investigated samples the strong fluorescence and pale to yellow colour of acritarchs combined with low pdi and organoclast reflectance values suggest thermally immature kerogen and a limited burial diagenesis in the study area moreover pdi showed a good correlation with uv fluorescence allowing a calibration of these two techniques and proving the reliability of pdi for thermal maturity estimation in sedimentary rocks unsuitable for rock eval pyrolysis and vitrinite reflectance furthermore the applied methodologies permitted the differentiation of reworked from in situ organic matter and highlighted the potential of the former for sequence stratigraphic investigations

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

organic petrography and geochemical characterization of the upper cretaceous second white specks and upper belle fourche alloformations west central alberta analysis of local maturity anomalies abstract the second white specks is an enigmatic unconventional shale play in the western canada foreland basin wcfb this play has an inconsistent production performance that has impacted exploration and production risk preventing extensive development in this contribution geochemical properties are studied with the purpose to identify possible geochemical factors that could contribute to the production variability of this unconventional petroleum system the studied succession consists of the second white specks sws and upper belle fourche ubf alloformations which are part of the sws shale play organic petrology and rock eval pyrolysis were combined to characterize the organic matter om and assess om richness thermal maturity and hydrocarbon generation potential in the foredeep section of the basin the results show that the om richness and hydrocarbon generation potential in this area is good and comparison with other studies show that they do not exhibit major lateral variations the kerogen is marine type ii and is dominated by liptinite vitrinite inertinite macerals and solid bitumen alginite and bituminite are the most abundant macerals altered bituminite provides evidence of anaerobic bacteria degradation there is a modest contribution of inertinite that may be responsible for a dilution effect of the pyrolyzable carbon the thermal maturity indicators in this study such as vitrinite reflectance tmax and alginite uv fluorescence color indicate that the controls on thermal maturity and hydrocarbon generation are not well understood there are lateral short scale variations or maturity anomalies that require further investigation to reduce the exploration risk

testing reproducibility of vitrinite and solid bitumen reflectance measurements in north american unconventional source rock reservoir petroleum systems abstract an interlaboratory study ils was conducted to test reproducibility of vitrinite and solid bitumen reflectance measurements in six mudrock samples from united states unconventional source rock reservoir petroleum systems samples selected from the marcellus haynesville eagle ford barnett bakken and woodford are representative of resource plays currently under exploitation in north america all samples are from marine depositional environments are thermally mature tmax 445 c and have moderate to high organic matter content 2 9 11 6 wt toc their organic matter is dominated by solid bitumen which contains intraparticle nano porosity visual evaluation of organic nano porosity pore sizes 1 0 produced lowest r values generally 0 5 absolute reflectance similar to a prior ils for similar samples other traditional approaches to outlier removal outside mean 1 5 interquartile range and outside f10 to f90 percentile range also produced similar r values standard deviation values

reevaluation of thermal maturity and stages of petroleum formation of the mississippian barnett shale fort worth basin texas new data including measured reflectance ro programmed open system pyrolysis data and kerogen elemental analyses obtained on the mississippian barnett shale in the fort worth basin texas indicate that secondary gas generation starts at 1 5 ro and not at the previously prescribed 1 1 ro oil cracking kinetic parameters derived from pyrolysis experiments in the presence and absence of water indicate that secondary gas generation will not occur at a thermal maturity as low as 1 1 ro and requires a minimum thermal maturity of 1 5 ro this difference is especially important in using the barnett shale as an analog for evaluating other possible shale gas plays the new reflectance measurements have a good relationship with hydrogen indices his and compare well with other published data sets however the relationship does not compare well with the previously published data used to prescribe 1 1 ro as the start of secondary gas generation in the barnett shale this discrepancy is attributed to differences in measured ro values and not attributed to differences in the hi values lack of publicly available information on the previously reported ro values makes it difficult to ascertain the reason for their lower values these lower ro values also have impact on the previously prescribed relationship for estimating ro from the temperature at maximum yield by programmed open system pyrolysis tmax as a result the new data do not agree with a previously described relationship and the considerable scatter makes the new relationship unreliable however the relationship between the hi and ro has less scatter which indicates that hi offers a better proxy in calculating ro than tmax for the barnett shale comparison of various programmed open system pyrolysis methods i e rock eval ii rock eval 6 source rock analyzer and hawk indicates that variations in hi are within 10 of one another an hi of at least 44 mg g total organic carbon is prescribed as a more certain limit for the start of secondary gas generation and prospective in situ gas shale accumulations

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

identifying the characteristics of groundwater flow in the classical karst area slovenia italy by means of tracer tests tracer tests are a widely used research method in karst hydrology in the classical karst area on the border between slovenia and italy they have a long history and for the most part they have been used to research the underground flow in the main karst conduits between the ponors and the springs the results of the tracer test from 2013 presented in the article revealed new knowledge about the central part of the aquifer less well researched to date where the density of caves and the level of karstification are lower two tracers uranine and amidorhodamine g were used at two injection points a research borehole in the central part of the aquifer and the karst surface at a distance of 2 5 km from a drinking water pumping station and six springs a pumping station three boreholes and four karst caves were observed for tracer breakthrough for a full year after injection the results were compared with findings from three other selected older tracer tests in which uranine was likewise used as a tracer but where hydrological conditions varied very low low and medium water levels as did the methods of injecting tracer in a sinking stream in a fracture on the karst surface the comparison showed how different modes of aquifer recharge and the heterogeneity of aquifer structure affect the characteristics of water flow and solute transport in complex karst aquifers

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

influence of geochemical organo petrographical and palynofacies assemblages on hydrocarbon generation a study from upper oligocene coal and shale of the makum coal basin assam india abstract the makum coal basin of northeast india comprises important coal and shale reserves of upper oligocene age a total of twenty samples were collected to evaluate the kerogen type hydrocarbon generation potential and thermal maturity through geochemically organo petrographically and palynofacies analyses the samples are characterized by high toc total organic carbon and large s2 remaining heavier hydrocarbons meet the required standards as good to excellent generation potential the coal and shale are marked by mixed type iii ii kerogen with minor occurrence of type i kerogen moderate to high hydrogen index hi values and are considered to generate thermogenic gas with some condensate oil the reflectance values indicate samples are mostly immature and close to the oil birth line the amount of vt60 grains also suggests that the samples can produce some condensate oil along with thermogenic gas the rock eval pyrolysis rep data stands with the interpretation through petrographic palynofacies and fourier transform infrared spectroscopy ftir in determining kerogen type and generation potential the generation potential is also controlled by the degree of organic matters reactivity the estimated reactivity indicates that besides vitrinite and liptinite up to 70 vol of the inertinite macerals have the potential to generate hydrocarbon the occurrence of a substantial amount of reactive macerals i e collotelinite vitrodetrinite collodetrinte corpogelinite alginite resinite and bituminite within the samples makes them more potential to generate hydrocarbons the diagram proposed based on our data of macerals and palynofacies assemblages may also be a convenient tool in detecting kerogen type s and nature of hydrocarbons

geological and geochemical characteristics of marine continental transitional shale from the upper permian longtan formation northwestern guizhou china abstract organic rich shale deposited in a marine continental transitional facies was well developed in the upper yangtze area during the late permian it is considered to contain a large amount of shale hydrocarbon resources this paper takes the upper permian longtan shale in the central guizhou uplift as an example to characterize the transitional shale reservoir based on organic geochemistry data x ray diffraction xrd analysis and scanning electron microscopy sem observation the geochemical characteristics of this transitional shale were systematically studied and the shale gas potential was investigated the results indicate that the longtan shale has fair to good hydrocarbon potential with high total organic carbon toc and contains type iii gas prone organic matter its high thermal maturity favors the generation of gas ro 1 10 2 74 xrd analyses show that the mineral components of the transitional shale are dominated by high clay content 58 7 wt the clay minerals are dominated by illite 44 and mixed illite smectite 43 sem observation shows that intra particle pores inter particle pores and microfracture were well developed in the longtan shale which can provide reservoir space for the accumulation of shale gas organic matter pores appear rare due to its organic type in summary the longtan shale has high organic content high maturation and high gas content all of which demonstrate its great potential as a shale gas resource but the high clay content of the longtan shale may be a challenge to shale gas production

solute transport processes in a karst vadose zone characterized by long term tracer tests the cave system of postojnska jama slovenia summary the processes influencing the solute transport in the karst vadose zone were studied by long term tracer tests with artificial tracers the results of three successive tracer tests with different modes of injection were compared tracer breakthrough curves were monitored at three drips of different hydrological types inside one of the cave galleries of the system of postojnska jama over several years comparison of the results indicates the highly significant influence of preceding hydrological conditions dry vs wet injection mode artificial flushing vs natural infiltration by subsequent rainfall and on a bare rock vs on an overlying layer and geologic heterogeneities within the vadose zone on solute transport in the karst vadose zone injection with artificial flushing resulted in rapid infiltration and the tracer traversed almost one hundred meters of bedrock in hours however the majority of tracer can be stored within less permeable parts of the vadose zone and then gradually flushed out after additional abundant and intensive precipitation in the period of several years long continued sampling in each of the tests proved to be important for reliable characterization of the long term solute transport dynamics

temporal organic facies variations of upper jurassic lowermost cretaceous source rocks in the danish central graben north sea abstract the upper jurassic lowermost cretaceous marine mudstones of the farsund formation constitute the principal source rocks in the danish north sea sector with the uppermost bo member considered most prolific however the areal distribution of the bo member is limited and since it is thermally immature over large areas it is unlikely that this interval has generated sufficient quantities of petroleum to fill the reservoirs in the danish sector in search for additional source rocks potential we have investigated the lower part of the farsund formation using a sequence stratigraphic framework organic geochemical screening and petrographic analyses of core and cuttings samples have been performed to define the source potential and map the regional distribution of organic rich sequences in the upper jurassic succession the study outlines variations of both maturity source rock quality and kerogen quality at sequence level with an upward improvement from poor gas prone type ii kerogen in the kimm 1 and kimm 3 sequences to highly oil prone type ii kerogen in the volg 1 volg 4 and ryaz 1 sequences the kerogen is dominated by fluorescent aom and liptinite and structural alginite in form of leiosphaerida and tasmanites type telalginites throughout the entire succession with vertical and regional variations in the amount of larger tasmanites the study shows that the shales in volg 1 and 3 sequences are organic rich and oil prone with toc 4 wt and hi 340 mg hc g toc particularly the volg 1 sequence being the thickest and laterally most widespread forms a significant supplementary source for oil in the danish sector

simple kinetic models of petroleum formation part ii oil gas cracking kinetic schemes describing oil gas cracking are a required component of models which predict the masses compositions and phases of petroleum expelled from source rocks an additional application is in predicting the temperature zone over which reservoired oil deposits will be degraded to gas this simple first order kinetic model calibrated on closed system laboratory pyrolysis of 16 different source rock samples describes the bulk conversion of oil c6 molecular range to gas c1 5 molecular range cracking rates vary markedly between samples depending on the saturate to aromatic ratio of the generated oil the initial hydrogen index hl0 of the sample taken as an indirect measure of the saturate to aromatic ratio of the oil it generates correlates strongly with optimized rate constants for oil cracking in individual samples thus cracking rates are predictable using a simple routinely performed geochemical screening measurement source rocks with high hl0 tend to generate saturate rich oils with a high mean activation energy and a tight distribution of bond energies which crack relatively slowly over a high but relatively narrow temperature range source rocks with low hl0 generate aromatic rich oils with a low mean activation energy and a broad distribution of bond energies which crack relatively rapidly over a lower but relatively wide temperature range this is an important contributing factor in the observed gas proneness of type iii source rocks with low hl0 the projected cracking window defined limits at 10 90 of initial oil degraded reference heating rate 2 c ma 1 varies from 155 to 205 c in very high quality source rocks hl0 600 mg g c 1 to 115 205 c in very poor quality source rocks hl0 50 mg g c 1 an order of magnitude increase decrease in heating rate elevates depresses these temperature windows by ca 15 c the extrapolations to the geological subsurface are subject to a confidence limit no better than 7 c extrapolation to the reservoir environment requires caution because kerogen an important potential catalyst and hydrogen donor allowing 100 cracking efficiency in the source rock is absent furthermore fractionation during expulsion causes saturate enrichment of expelled ultimately reservoired oils thus in reservoir cracking should be at least as slow as cracking in good quality source rocks and coke or pyrobitumen formation is needed to conserve the hydrogen balance a case history based on deep petroleum pools of the uk central north sea confirms these projections demonstrating no positive evidence of significant in reservoir cracking at temperatures as least as high as 174 c and perhaps even 195 c previous studies have overestimated the importance of in reservoir cracking future studies aiming to predict petroleum composition in traps should concentrate on understanding the charge composition expelled from the kitchen

geochemical characteristics of black shales from triassic turbidites peninsular malaysia implications for their origin and tectonic setting abstract field observations indicate that shale intervals of triassic turbidites from the semanggol and semantan formations in the peninsular malaysia occur as thick bedded dark grey to black shales overlying conglomerate pebbly sandstone thick bedded sandstone and sandstone shale interbeds this sequence characterises a submarine fan depositional setting where the conglomerate sand and sand shale intercalations represent an inner and middle fan setting in a shallow marine environment whereas the black shales were deposited in a deeper marine environment of the outer fan the redox sensitive trace metal inventory v ni cr of the black shales is dominated by clastic input and the depositional environment is likely oxic suboxic toc values are highly variable 3 2 3 3 wt and derive from washed in allochthonous organic material the semantan formation black shales have features of a felsic source rock while black shales from the semanggol formation were inherited from more intermediate rocks as constrained by their al2o3 tio2 ratios similar al2o3 sio2 ratios as well as cia values suggest wet paleoclimatic conditions and intensive weathering of source rocks during the late triassic deposition of both shales the tectonic setting deduced from immobile trace metal ratios is a passive margin for the semanggol black shales and a fore arc basin setting for the semantan black shales the inconsistency between the interpreted geological and geochemical tectonic settings particularly for the semanggol black shales is due to the recycled nature of the sediment sources that were deposited in a different tectonic setting the clay fractions of both formations comprise of abundant illite and kaolinite with some smectite in few samples from the semantan formation based on illite contents 38 68 and ic values 0 45 0 62 2 the studied black shales are in the late diagenesis stage the organic matter in the semanggol and semantan black shales is characterized by kerogen type iii proposing a terrestrial origin of the organic matter which was transported along with the clastic sediments by turbidity currents

a new thermal extraction protocol to evaluate liquid rich unconventional oil in place and in situ fluid chemistry abstract assessing oil in place and the proportion of oil that is producible are two critical measurements in evaluating liquid rich unconventional well and play economics current methodologies to evaluate oil in place oip include log calculated estimates petroleum systems charge modeling and direct geochemical measurements the standard open system programmed pyrolysis method has been modified to remove a broader range of thermally extracted free and adsorbed hydrocarbons and non hydrocarbons in liquid rich unconventional plays the added isotherms with a relatively low temperature start results in additional free hydrocarbon s1 peaks the extra s1 peaks are used to assist in evaluating in situ hydrocarbon quality examination of as received and post solvent extracted programmed pyrolysis data from replicate samples indicates a significant amount of solvent extractable free hydrocarbon is not captured in the s1 and rolls over into the s2 peak this observation suggests the s1 peak may not represent total oil in place less evaporative losses this paper examines a new multi step high resolution on column thermal extraction system to provide an inexpensive screening tool to map zones of higher in place oil and evaluate chemical characteristics which can be used to assist in estimating productivity the thermal extraction unit is coupled to a flame ionization detector fid by a short uncoated capillary column to generate a high resolution thermal extraction profile thermogram with four temperature fractions the area under each thermal peak provides direct measurements of volatized hydrocarbon and non hydrocarbon compounds examination of individual compounds within each thermal fraction demonstrates multi step thermal extraction is not a simple fractional distillation but also is impacted by inorganic and organic interactions if we assume each thermal fraction represents oil compounds with increased complexity then one can use peak area ratios to estimate in situ fluid make up and the proportion of in situ oil that can be considered producible with completions enhancement

insights into the effects of matrix retention and inert carbon on the petroleum generation potential of indian gondwana shales abstract the rock eval pyrolysis and total organic carbon toc analysis technique is widely used for organic geochemistry screening of source rocks and potential unconventional petroleum reservoirs the rock eval derived parameters the hydrogen index hi which is the ratio between hydrocarbons released under the s2 curve hydrocarbon formed by thermal pyrolysis s2 is an indicator of petroleum generation potential and total organic carbon toc can be used to infer the type of organic matter present in a rock however hi is often under estimated due to retention of some hydrocarbons included under the s2 curve by the rock matrix and the presence of inert carbon within the rock here we describe and correct the matrix retention and inert carbon effects on hydrocarbon generation from a suite of shale samples from indian gondwana shale reservoirs removal of the petrographically identified inert carbon component from the samples tested leads to less scatter in the toc s2 relationship obtained the ratio of volume percentage of organic matter identified through optical microscopy to toc is calculated and that ratio was least in the one heat affected sample but higher in low toc shales 12 5 with decreasing toc content in the sample set analyzed the corrected hi values calculated using the s2 toc intercept increase significantly this correction can therefore lead to false indications about the type of organic matter present a key novel finding of this work is the need while correcting hi for matrix retention effects to consider samples with a specific range of toc contents and to match them to the kerogen types present e g types iii and iv in the samples analyzed filters should also be applied to adjust for the degree of thermal maturity and organic facies

critical considerations when assessing hydrocarbon plays using rock eval pyrolysis and organic petrology data data quality revisited abstract the dramatic increase in exploration for unconventional hydrocarbon resources has inherently fuelled the need for new source rock geochemical data the need for new data comes along with an increasing number of new users many of whom do not possess the background to interpret accurately and evaluate the quality of data sets generated by different geochemical screening techniques e g rock eval pyrolysis vitrinite reflectance here datasets from rock eval pyrolysis vitrinite reflectance and leco toc analyses are scrutinized and compared to show how failing to recognize good vs bad datasets can dramatically change interpretations during prospect or play appraisals detector saturation contamination of the sample with drilling fluid and suppression of both tmax and vitrinite reflectance are examples of complications that could compromise the validity of the results and the play or prospect reviews derived from them in addition misconceptions such as leco toc is better than rock eval 6 toc expressed by many users are a consequence of the lack of understanding of how different screening techniques and instrumentation work a solid understanding of these pitfalls and limitations can provide inexperienced geoscientists and engineers with the required support to improve risk maps for hydrocarbon charge analysis and source rock evaluations when using classic guidelines for interpreting results

molecular structure and origin of solid bitumen from northern sichuan basin abstract four natural solid bitumen samples were collected from the guangyuan area northwest sichuan basin southwest china to characterize their structure samples were ground to power 120 mesh purified by znbr2 solution to remove mineral and soluble impurities and analyzed using rock eval pyrolysis elemental analysis raman spectroscopy solid bitumen reflectance and solid state 13c nuclear magnetic resonance to determine the maturity degree of samples and obtain structural information results showed that guangyuan solid bitumen samples are in low maturity and three solid bitumen maturity detection methods are compared in this research with respect to the solid bitumen molecular structure less than 10 carbon atoms were determined in aliphatic chains and the solid bitumen aromatic clusters ranged from two to four rings which indicates that the solid bitumen comprises complex geological organic matter such as kerogen four molecular models were established in this research to reflect the basic molecular configuration of natural solid bitumen samples were classified into two types based on the structural information and models and the results imply that the solid bitumen samples may have been derived via different evolutionary processes this phenomenon indicates that structural studies could play an important role in the research of oxidation and carbon isotope changes in solid bitumen in summary this investigation provides an understanding of the evolutionary stages of guangyuan bitumen establishes associated molecular structure models and researches the role of structural information in bitumen source studies as the focus of this study the four molecular models were used to restore the structural characteristics of natural solid bitumen as possible and this study tried to find out the relationship between the solid bitumen structure information and it geology evolution as the carbon isotope may not accurately determine the source of solid bitumen because of oxidation molecular information could be used to research the solid bitumen source and associated evolution

hydrogeological implications of the resistivity distribution inferred from electrical prospecting data from the apulian carbonate platform abstract electrical and magnetotelluric surveys have been performed on the apulian carbonate platform to study the deep coastal karst aquifer the surveys extend to a depth of about 7 km to give a complete hydrogeological understanding of the area the problems of interpreting regional geophysical data in highly heterogeneous carbonate rocks are extensively analyzed this study suggests that the aquifer is generally confined at both the top and the bottom by more compact carbonate rocks and has a maximum depth of about 2 km also seawater invasion is both areally and vertically limited the possibility that dolomite rocks present in the 2 5 km depth range could also hold low salinity waters is discussed all the hydrogeological features of the investigated area are found to be mainly dependent on the tectonic evolution of the carbonate platform

influence of refractory organic matter on source rock hydrocarbon potential a case study from the second white specks and belle fourche formations alberta canada abstract dilution by inert refractory organic carbon can have a significant impact on the hydrocarbon potential of source rocks in this study a correction of total organic carbon based on petrographic observations is proposed to give a better indication of hydrocarbon generation potential this correction shows that although the second white specks formation is an excellent hydrocarbon source rock hydrogen index and total organic carbon are influenced by dilution from refractory organic carbon of various sources the results show that a higher degree of dilution occurs within the belle fourche formation than the second white specks formation this dilution can have a significant impact on the hydrocarbon potential of the rock volumetric calculation of the inert carbon fraction using organic petrographic methods provides a semi quantitative method to correct total organic carbon values for the refractory organic carbon dilution effect incorporation of the dilution corrected organic carbon value in hydrogen index calculations allows a greater understanding of source rock hydrocarbon potential this method provides better differentiation of the small scale variation between micro facies and formation as observed in the second white specks and belle fourche formations than traditional bulk geochemical methodologies and previously proposed correction methodologies degree of dilution either through transport of recycled allochthonous or autochthonous reworking of organic matter in situ is highly variable and represents a significant challenge in the characterization of heterogeneous source rocks this study investigates the organic petrology and geochemistry of a sediment core from the thermally immature area of the upper cretaceous second white specks formation and belle fourche formation reflectance and relative abundance of three maceral groups bituminite alginite and refractory organic carbon macerals showed significant organic matter compositional differences between micro facies in the second white specks formation a change is also observed in organic matter composition from the upper part of the belle fourche formation to the second white specks formation these compositional changes represent shifts in sediment source sea floor oxygen levels and depositional energy levels these changes can be episodic as observed between micro facies or longer time scale trends as observed between the studied formations

comparative organic petrology of interlayered sandstones siltstones mudstones and coals in the upper carboniferous ruhr basin northwest germany and their thermal history and methane generation in the coal mining ruhr area upper carboniferous rocks ca 4000 m consist of interlayered sandstones siltstones mudstones and coals they were deposited in a tropical paralic environment where alternating fluvial sedimentation occasional marine ingressions and swamp growth resulted in an irregular cyclic succession the total sedimentary package contains on an average 6 vol of organic matter about 70 vol of the organic matter occurs in coal seams the rest as dispersed organic matter in clastic rocks the organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones it consists of about 70 vitrinite 20 inertinite and 10 liptinite the overall maceral group composition is the same for coals and dispersed organic matter this surprising similarity is caused by a nearly exclusive input of land plant derived organic matter to swamps and fluvial systems and a similar degree of preservation highest average liptinite contents of total macerals were found in unrooted mudstones highest average inertinite contents in coarse grained siltstones and highest average vitrinite percentages in sandstones

multi proxy approach to screen the hydrocarbon potential of the jurassic succession in the matruh basin north western desert egypt abstract this paper discusses the hydrocarbon potential of the jurassic succession in a mature basin in egypt as an important element of a larger petroleum system study prior to any organic petrographic and organic geochemical analyses a palynological age dating of the originally undifferentiated jurassic sequence was carried out to identify different formations under investigation this was based on key bioevents of some recovered dinoflagellate cysts and the identified lithology palynological toc rock eval pyrolysis including modified rock eval methods and vitrinite reflectance vro data from a total of 14 samples taken from the uppermost lower upper jurassic sequence represented by the wadi natrun toarcian aalenian khatatba late bathonian callovian and masajid oxfordian formations in the abu tunis 1 well are presented in addition two samples from the abu tunis 1 well and the proximal 32 km to the east siqueifa 1 well having the highest remaining hydrocarbon potential s2 yields were analyzed and their results were compared using modified pyrolysis programs although the data showed a good correlation between the tai of the palynomorph assemblage vitrinite reflectance and tmax from rock eval pyrolysis in the shallower intervals the correlation between vro and tmax was poor in the lower half of the studied succession middle khatatba and wadi natrun formations the very low tmax values indicate immature om while vro and tai indicated middle stage of oil window to past peak oil generation the reason for this discrepancy is that the deeper samples are reservoir rocks not source rocks and the majority of the organic matter is not composed of reactive kerogen but consists of migrated hydrocarbons and nso compounds contamination due to oil based mud obm was eliminated because the abu tunis 1 well was drilled in 1969 prior to the extensive use of obm in drilling this study showed that a multi proxy approach is the best way to screen the hydrocarbon potential in a thick succession that contains interbedded source and reservoir rocks

laboratory and field studies of the application of electromagnetic prospecting for groundwater on marajo island brazil on marajo island para brazil many cattle die due to lack of potable water since a majority of the shallow groundwater is brackish two types of fresh water aquifers were delineated using resistivity methods 1 a deep aquifer at about 100 m depth and 2 shallow buried stream channels filled with sand and gravel 40 m and embedded in clay and sand beds with brackish water 0 8 m 5 m for the demarcation of the shallow buried stream channel aquifers inductive electromagnetic moving source receiver methods were tested to replace the cumbersome galvanic resistivity methods in order to verify the applicability of em survey techniques for groundwater exploration in hydrogeologic conditions typical of marajo island analog model studies were carried out the groundwater bearing channels buried in the clays or in the sediments with brackish water represent geoelectrically a less conducting body in a more conducting environment the buried channel guajara mirim on marajo island wa

reflectance measurements of zooclasts and solid bitumen in lower paleozoic shales southern scandinavia correlation to vitrinite reflectance abstract reflectance measurements have been carried out on zooclasts graptolites chitinozoans and vase shaped microfossils and other organic particles vitrinite like particles porous granular vitrinite like particles and solid bitumen in middle cambrian to upper silurian shales from central and southern sweden and the danish island of bornholm baltic sea the most abundant organic components in all the shales are fragments of graptolites and vitrinite like particles the reflectance distribution of these two types of components is largely identical and it is suggested that the vitrinite like particles are fragments of graptolites without any recognizable morphology reflectance measurements of graptolites and vitrinite like particles yield well defined reflectance populations in samples with average r graptolite and average r vitrinite like of 0 75 r o the reflectance distributions are bimodal because of increasing bireflectance and the average reflectance value of the well defined lower reflecting population is arbitrarily used as maturity indicator our results suggest that with increasing thermal maturity the reflectance of graptolites increases faster than the predicted vitrinite reflectance the relationship between graptolite reflectance and equivalent vitrinite reflectance can be expressed by the equation vr eqv 0 73 r graptolite vitrinite like low 0 16 the gas generation window which normally is considered to begin at a vitrinite reflectance of 1 3 r o in post lower paleozoic rocks containing vitrinite starts accordingly at 1 56 r o graptolite reflectance porous granular vitrinite like particles occur in minor amounts and they may represent graptolite fragments with a non smooth surface they generally yield slightly higher reflectance than non granular vitrinite like particles and graptolite fragments the middle cambrian to furongian upper cambrian shales may contain sparse fragments of vase shaped microfossils vsm that seem to follow the maturation trend of chitinozoans in the present sample set the reflectance of chitinozoans and vsm is comparable to that of graptolites at the same level of maturity reflectance measurements of solid bitumen are a poor maturity indicator probably because bitumen can have various origins and morphologies and it may not be indigenous to the host rock

upper jurassic lowermost cretaceous marine shale source rocks farsund formation north sea kerogen composition and quality and the adverse effect of oil based mud contamination on organic geochemical analyses abstract the jude 1 well is located in the central part of the danish central graben north sea and was drilled into immature black shales of the upper jurassic lowermost farsund formation a world class marine source rock the well was drilled with oil based drilling mud obm the lithofacies consists of argillaceous shale calcareous shale and dolomite stringers as confirmed by cuttings and core a core was taken in the upper part of the formation at the beginning of a hot argillaceous shale interval characterized by elevated toc and hi values cuttings and core samples were investigated to unravel kerogen composition source rock quality and the contamination effect of obm on organic geochemical analyses the organic facies of the source rocks corresponds to type ii kerogen or organofacies b sensu pepper and corvi 1995 considerable fluctuations in hi values through the farsund formation reflect pronounced variations in source rock quality although a faint lamination of the shales and overall high toc contents testify to prevailing oxygen deficient depositional conditions preventing significant bioturbation and reworking of the sediment and organic matter petrography of core samples reveals a relatively homogenous sapropelic kerogen composition dominated by a groundmass of yellowish fluorescing amorphous organic matter and liptodetrinite intimately associated with the mineral matrix telalginite is less abundant but tasmanites and in particular leiosphaerida type telalginites were observed minor but varying amounts of detrital terrigenous macerals suggest a considerable distance to land areas and thus limited supply of land plant derived organic matter the argillaceous shale lithofacies generally is more oil prone and organic rich than the more gas prone calcareous shale facies the uppermost section includes the hot argillaceous shales which together with two deeper argillaceous shale intervals are highly organic rich and oil prone average toc of the hot argillaceous shales is 7 wt and hi reaches 500 mg hc g toc the total ultimate expulsion potential uep of the over 853 m 2799 ft thick farsund formation is 142 mmboe km2 results from non contaminated samples are thus consistent with the farsund formation being a world class highly oil prone marine source rock the predicted oil composition corresponds to paraffinic low wax oils the adverse effect of obm contamination on geochemical analyses is demonstrated by rock eval data and measured bulk kinetics of contaminated core samples the measured kinetics has a considerable proportion of low activation energies related to obm contamination which is also supported by high production indices further gas chromatograms of the saturated fraction of extracts from contaminated cores clearly show evidence of obm in the nc11 nc14 range rock eval s2 peaks have a shoulder showing that the low ea peaks result from carry over from the s1 peak caused by the obm contamination as a consequence hydrogen index values are increased

comparative rock eval pyrolysis as an improved tool for sedimentary organic matter analysis an improved rock eval pyrolysis method is described for the global and exhaustive characterization of kerogen and bitumen in rock samples comparative pyrolysis is derived from the original rock eval method of espitalie et al it overcomes some of its inadequacies and allows a better exploitation of the pyrolysis data this new pyrolysis method is proposed mainly for routine analysis of bitumen in rock samples using a double analysis of each sample on whole rock and extracted rock the difference between these two pyrolysis curves corresponds to the bitumen pyrolysis curve and is used for estimating the total bitumen content the bitumen yield obtained in comparative pryolysis as a good correlation with the bitumen yield obtained by the standard solvent extraction method with however some limitations due to the mineral matrix effect the bitumen pyrolysis curve is further subdivided into three fractions which allow a quick and easy typing of bitumen products this method has been successfully applied to basin analysis

determination of the total organic carbon toc based on conventional well logs using artificial neural network abstract total organic carbon toc is the measure of the amount of carbon available in an organic compound and is often used as an essential factor for unconventional shale resources evaluation previous models for toc determination based on density log data considered the presence of organic matter is proportional to the formation bulk density also model those based on resistivity log sonic or density logs as well as the formation level of maturity lom were used to determine the toc these models assumed linear relation between resistivity and porosity logs previous correlations showed very low coefficient of determination of the estimated toc compared to the actual laboratory data the objective of this paper is to develop an empirical correlation to determine the toc for barnett and devonian shale formations based on conventional logs using artificial neural network ann core toc data 442 data points and well logs resistivity gamma ray sonic transit time and bulk density from barnett shale were used to develop the ann model for the first time an empirical correlation for toc was developed based on the weights and biases of the ann model the developed correlation was then applied to estimate toc for devonian shale the developed ann model predicted the toc based on conventional well log data with high accuracy the average absolute deviation aad and coefficient of determination r2 for the predicted toc compared with the measured toc for barnett shale are 0 91 wt and 0 93 respectively the developed model outperformed the previous available models in estimating toc for devonian shale as well with aad of 0 99 wt and r2 of 0 89 compared to aad of 1 16 wt or more and r2 of 0 65 or less for the available correlations the developed empirical correlation was used to estimate the toc with high accuracy for barnett shale and devonian shale formations the developed correlation will help the geological and reservoir engineers predict the toc using well logs without the need to measure toc in the laboratory

thermal maturity of lower paleozoic sedimentary successions in arctic canada mean maximum graptolite reflectance values from numerous sections in arctic canada range from 0 6 in cornwallis island and northwestern devon island to 4 7 in ellesmere island we attribute this great lateral reflectance variation to differing burial depths of the graptolite bearing strata beneath thick synorogenic siliciclastic covers we attribute the low maturity of rocks in northern cornwallis and eastern bathurst islands to a maximum burial of about 2 km elsewhere we used the paleogeographic location and proximity to the ellesmerian overthrust wedge to interpret the measured reflectance values in northern ellesmere island where the highest graptolite reflectance values 4 7 occur as much as 9 6 km of synorogenic siliciclastics accumulated on a tectonically loaded carbonate shelf initial synorogenic siliciclastics encountered substantial submarine to basin relief and thus about 2 km of sediment were deposited prior to the initiation of deposition on the adjacent drowned shelf also the deep water sequence probably was underlain by attenuated continental crust adjacent to the southeastward advancing ellesmerian overthrust wedge together these factors caused deposition of as much as 7 6 km of sediment in western melville island and as much as 9 6 km in northeastern ellesmere island on the drowned shelf synorogenic stratal thicknesses were less a feature we attribu e to a thicker more rigid crustal sequence and greater distance from the ellesmerian tectonic loading we expect liquid hydrocarbons to be generated from the organic matter in the shales in areas with a graptolite r0 maximum gr0 max of less than 1 7 the presence of two types of solid bitumens having different reflectances morphologies and optical textures suggests that hydrocarbons were generated and migrated through the graptolite bearing strata we expect only gaseous hydrocarbons in areas where gr0 max exceeds 2 0 r0

correlating rock eval tmax with bitumen reflectance from organic petrology in the bakken formation abstract the bakken formation is a major unconventional shale play in north america which lacks an independent calibration for accurately correlate thermal maturity from programmed pyrolysis via temperature of maximum pyrolysis yield tmax with optical methods e g bitumen reflectance in the present study several samples from the upper and lower members of the bakken formation in north dakota were analyzed by detailed organic petrography bitumen reflectance and rock eval 6 pyrolysis organic petrography showed that the organic matter consists of various types of bitumen amorphous matrix bituminite liptodetrinite acanthomorphic acritarch marine alginite granular micrinite and inertinite macerals fluorescence color under uv light of macerals from the liptinite group was used to confirm the thermal maturity level due to the scarcity absence of primary vitrinite ro measurements on solid bitumen particles were converted to equivalent vitrinite reflectance vro eq using a published correlation equation from the coeval new albany shale overall geochemical analysis from rock eval pyrolysis reveals almost similar trends for the upper and lower members which allowed proposing a single correlation for vro eq to tmax for the bakken shale comparing the observed relationship for the bakken shale with the previously established models for the devonian duvernay shale canada and the mississippian barnett shale united states shows discrepancies results confirmed the necessity of developing a specific equation for the bakken shale members to relate vitrinite and solid bitumen reflectance data to tmax from rock eval pyrolysis furthermore the outcome of this study indicated that linear trends cannot accurately represent the relationship between these two parameters considering the kerogen kinetics and non linear relationship between transformation ratio tr and tmax therefore a polynomial correlation a better fit to the data was proposed to more accurately represent the nature of this relationship

model assisted rock eval data interpretation for source rock evaluation examples from producing and potential shale gas resource plays abstract rock eval pyrolysis has been widely accepted by the petroleum industry as a useful technique for a quick easy and cost effective source rock evaluation however there are misconceptions and misuse of some of the existing rock eval parameters due to implicit underlying assumptions or poor understanding of the limitations which could lead to erroneous conclusions data interpretation from a perspective of hydrocarbon generation kinetics may facilitate better interpretation of the hydrocarbon generation capacity of a source rock from its thermal stability and transformational behaviors we present a model assisted approach for data interpretation from which data scatters can be viewed not only for the remaining petroleum generation potential of individual samples but also for data specific thermal decomposition path as a whole to verify whether the data come from a single kerogen population with similar kinetics and associated generation potentials moreover we propose a concept of dimensionless toc and s2 variables that effectively removes the thermal maturity overprint in the traditional toc vs s2 plot used for the determination of the kerogen type the dimensionless variables are defined by rescaling the parameters against their original values before thermal decomposition on a dimensionless plot data points from the same genetic population of source rocks align on a single line regardless of their thermal maturation levels this article demonstrates the methods and the proposed approaches for studying oil generation kinetics and resource potential using traditional rock eval data through examples from selected producing and potential shale gas plays in canadian sedimentary basins and elsewhere

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

paleoredox reconstruction of bituminous shales from the miocene hancili formation cankiri corum basin turkey evaluating the role of anoxia in accumulation of organic rich shales abstract the early middle miocene succession in the cankiri corum basin ccb represents a potentially large bituminous shale resource in turkey in order to elucidate paleoredox conditions during deposition of the hancili formation and to evaluate the role of anoxia in accumulation of the organic rich shales a total of 70 samples were collected using channel profile sampling strategy rock eval pyrolysis data indicates that the majority of the samples have excellent generative potential total organic carbon toc content of the hancili ranges from 0 61 to 13 91 wt 5 59 wt on average pyrolysis data as well as microscopic and isotopic studies of the samples indicate that the organic matter in the hancili bituminous shales is immature to early mature predominantly oil prone types i and ii and algal in origin moreover the isotopic 13corg and geochemical studies suggest that the studied samples were deposited in a lacustrine setting which is consistent with the previous sedimentological inferences based on average enrichment factors ef of redox sensitive elements ni 2 18 v 1 58 cu 1 47 and mo 1 1 are only slightly enriched relative to the average shale whereas u 0 76 pb 0 71 and zn 0 73 are depleted such an enrichment pattern for redox sensitive trace elements reflects an environment with an oxic dysoxic water column well known redox sensitive geochemical ratios e g v v ni ni co also show small scale fluctuations in redox conditions during deposition of the hancili formation toc s fe relationships suggest that the hancili formation were deposited under oxic dysoxic water conditions however high toc and hi along with low oi values of the samples suggest that the samples have not weathered under oxic dysoxic regime to investigate the role of anoxia in accumulation of the hancili organic rich shales toc content of 41 samples were plotted against the paleoredox ratios lack of correlation between the toc content and redox indicators suggests that the redox conditions were not a controlling factor in accumulation of the organic rich shales of the hancili formation other factors such as high sedimentation rate and periodic eutrophication e g algal bloom may have influenced accumulation of organic matter om and compensated for the lack of preservative anoxic conditions

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

three common source rock evaluation errors made by geologists during prospect or play appraisals geologists are frequently called on to evaluate the source rocks associated with their exploration prospects or plays the three most common questions asked and answered about the source rock during project reviews are what s the total organic carbon toc what kerogen type does rock eval indicate and what maturity level does the vitrinite reflectance data point to the answers to these seemingly innocuous questions may in fact be providing a false sense of security about the source rock in question understanding how this line of questioning can lead you astray and make you the victim of the toc myth if i have high toc i have a good source rock the rock eval fallacy the rock eval data tell me what kind of kerogen is in my source rock and the vitrinite reflectance deficiency vitrinite reflectance will tell me if my source rock is generating is important some of the solutions to these problems include fully integrating toc and rock eval data supplementing rock eval data with pyrolysis gas chromatography and using burial history diagrams to help interpret vitrinite reflectance harry dembicki jr is a senior geological advisor for geochemistry in the geological technology group at anadarko petroleum corporation where he provides technical support to both exploration and development teams he holds a b s degree 1973 in geology from the state university college of new york at new paltz and a ph d 1977 in geology with emphasis in organic geochemistry from indiana university he previously worked as an organic geochemist for conoco and marathon

organofacies study of the bakken source rock in north dakota usa based on organic petrology and geochemistry abstract samples taken from the upper and lower members of the bakken formation in four wells that were drilled in a northeast southwest trend along the eastern margin of the williston basin in central western north dakota were investigated in order to present an overview of source rock quality and depositional environment conditions for the main purpose of establishing an organofacies model several techniques such as rock eval 6 pyrolysis x ray fluorescence elemental analysis vitrinite reflectance organic petrography and visual kerogen assessment using reflected and transmitted white light and uv light microscopy on whole rock pellets were combined to draw the best possible conclusions the results indicate that kerogen is mainly marine type ii with increasing in maturity towards the central and sw portions of the basin detailed organic petrography of the samples showed that solid bitumen amorphous matrix bituminite granular bitumen alginite acritarchs and liptodetrinite are the most abundant macerals in order to properly determine the bakken organofacies the original hydrogen index hio was restored using various mathematical models and empirical methods the mathematically restored hio from thermally mature samples hio calculated was then compared to the hi values from thermally immature samples tmax

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

organic facies and hydrocarbon potential of the early middle albian kharita formation in the abu gharadig basin egypt as demonstrated by palynology organic petrology and geochemistry abstract during the past decades exploration activities carried out in the western desert of egypt by several oil companies revealed the oversimplified approach to the study of sedimentary basins in this region the current study evaluates and discusses the palynology and palynofacies of the clastic succession of the kharita formation albian in one of the most petroliferous deep seated fault controlled basins in the western desert of egypt the abu gharadig basin although the focus is on the palynofacies association the hydrocarbon potential of the kharita formation will also be addressed by means of organic petrology and rock eval pyrolysis marine cretaceous source rocks have generated substantial quantities of oil and gas in the abu gharadig rift basin moreover abu gharadig basin is characterized by containing not only oil gas generating source rocks but also reservoir rocks with appreciable porosities and permeabilities palynological toc rock eval pyrolysis and vitrinite reflectance vro data from 26 cuttings samples recovered from the kharita formation in the bed 2 1 well are presented the palynological age dating al 2 palynozone confirmed early to middle albian age based on the first downhole appearance of the marker concavisimisporites punctatus the optical and visual characterization of the palynofacies associations showed two distinct palynofacies associations that alternated with each other kerogen type iii to iii ii was recorded based on the dominance of phytoclasts and opaque organics some intervals showed a slight dominance of amorphous organic matter aom thermal alteration index tai values of 2 3 measured on the psilate trilete spores in combination with vitrinite reflectance vro values in the range from 0 51 to 0 62 and the yellow to dull yellow colors of the liptinite macerals exhibited under uv light excitation indicate immature to the early stage of the oil window tmax values from rock eval pyrolysis range from 426 to 438 c also confirm the low maturity of the organic matter thin coal stringers were recorded within the kharita formation having slightly higher vro ran values 0 64 to 0 76 which is possibly the result of differences in mineral matrix variations within the kharita formation based on the low toc avg 0 71 wt s2 avg 0 97 mg hc g rock and hi avg 149 mg hc g toc values from pyrolysis the hydrocarbon potential of the kharita formation in the studied well is considered to be low

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

a quick analytical approach to estimate both free versus sorbed hydrocarbon contents in liquid rich source rocks free and sorbed low to medium molecular weight thermovaporized hydrocarbons c20 are the main organic compounds released at the temperature range corresponding to the rock eval shale playtmsh0 parameter 100 c 200 c whereas medium and high molecular weight thermovaporized compounds c30 are the predominant components that are thermal released in the temperature range corresponding to the shale play sh1 parameter 200 c 350 c now an analytical methodology is proposed here to predict the quantity of free versus sorbed hydrocarbons still present in any liquid rich sedimentary rock the method compares shale play parameters sh0 and sh1 obtained from both whole rock samples and their corresponding organic matter om concentrates isolated by standard nonoxidizing acid treatments and drying procedures the hydrocarbon content obtained from whole rock hctotal rock is mainly considered as the total amount of free liquid hydrocarbons hcfree and sorbed liquid hydrocarbons hcsorbed om still contained in the investigated rock sample the hydrocarbon content obtained from om concentrates however only reflects the sorbed liquid hydrocarbons in these equations tocrock is the total organic carbon of the rock sample tocom corresponds to the toc content of the om concentrate sample massrock is the initial mass of the rock sample massom is the initial mass of the om concentrate sample fidsignalrocksh0 sh1 is the flame ionization detection fid signal that corresponds to the global surface area under each thermal peak sh0 and sh1 generated by the rock eval fid fidsignalomsh0 sh1 corresponds to the global surface area under each thermal peak sh0 and sh1 measured by the rock eval fid between 100 c and 350 c after the themovaporization of the om concentrate sample free liquid hydrocarbons are finally calculated as the difference between these last two values hcfree e hctotal rock hcsorbed om this paper illustrates the application of this methodology on rock samples derived from the vaca muerta formation argentina along the selected vertical profile the lower rock interval contains approximately 60 of sorbed liquid hydrocarbons whereas the upper sample contains more than 90 free liquid hydrocarbons the parameters freehcsh0 and freehcsh0 sh1 could be used to identify potential producible free liquid hydrocarbons intervals in early exploration campaigns

source rock evaluation of the cenomanian raha formation bakr oil field gulf of suez egypt observations from palynofacies rgb based sporomorph microscopy and organic geochemistry abstract the gulf of suez area in eastern egypt is one of the most prospective and promising hydrocarbon provinces all over the world sixty drill cuttings samples of the upper cretaceous raha formation 70 120 m have earlier been processed for their palynomorph and palynofacies contents including 36 geochemically screened samples for their source rock potential using toc rock eval 6 turbo the new rock eval 7s instrument along with one of its latest modules the cleansim method the combination between visual palynofacies and rgb based sporomorph color image analysis along with the geochemical results are presented as part of a detailed assessment of the organic matter om types om richness and thermal maturity levels palynofacies analysis defined three associations of om types the first and third associations consist of kerogen type ii the former is dominated by a moderate abundance of amorphous organic matter aom and phytoclasts whilst the latter is dominated by high aom content conversely the second association is dominated by terrigenous fragments of gas prone type iii kerogen the application of rgb analysis indicated a thermally immature to mature stage for some intervals in one of the three studied wells the b 109 geochemical screening results led to divide the raha formation into three distinctive groups which are characterized by varied om qualities and quantities hydrocarbon potential and thermal maturity levels varied thermal maturity levels was related directly to the late cretaceous tectonics like the effect of syrian arc system and the oligocene miocene syn rift activity that led to the opening of the gulf of suez differences in kerogen types were observed between geochemical and palynofacies analyses microscopic investigations of palynofacies dominated aom suggested that most aom particles were of terrigenous origin due to the effect of biodegradation and gradual transformation of phytoclasts into aom reflecting a kerogen type iii instead of kerogen type ii that was indicated by palynofacies analysis ternary plots

depositional environment and characteristics of late eocene carbonaceous swampy tidal flat facies in the fayoum basin egypt abstract this study addresses the stratigraphic and sedimentological characteristics of the late eocene carbonaceous shale bearing qasr el sagha formation in the fayoum basin egypt the qasr el sagha succession is comprised of four facies types coastal mudflat tidal flat swamp and storm affected tidal channels the swamp facies contain the fayoum carbonaceous shale facies which have not been studied in the past the present study reports the first publicly available sedimentological palynological and geochemical results for the fayoum facies eight samples of the sequence were taken from a freshly exposed road cut and analyzed petrographically geochemically and palynologically in order to determine the paleoenvironment of deposition and prevailing conditions the palynomorph assemblages show that the lower part of the sequence was deposited in a lowland riparian environment with continued freshwater influx the depositional regime in the upper part of the sequence was swampy and dominated by fresh water mixed angiosperms and pteridophytes dominated the woody forest vegetation and were the source for the formation of the fayoum carbonaceous shale facies the recovered palynomorph assemblage points to the prevalence of a tropical to a sub tropical warm humid climate with heavy precipitation in the lowland swampy areas that were in close proximity to the freshwater influx the water table was above the fen surface preventing oxidation of the vegetation intermittent flooding or fluctuation in paleo water levels likely occurred in the peat paleo mire the fayoum samples have ro ran values of 0 40 0 50 which is in very good agreement with the tmax from rock eval pyrolysis although a few of the samples have elevated s2 15 24 mg hc g rock and hi values 125 140 mg hc g toc they do not have any hydrocarbon generating potential in the sampled location as a result of their immaturity petrographically the analyzed samples are dominated by huminite group macerals up to 77 with telohuminite eu eulminite b being dominant liptinite content is up to 3 5 whereas inertinite content is up to 6 dominated by fungal sclerotia funginite the toc of the facies samples does not exceed 40 wt

monitoring soil contaminations using a contactless conductivity probe1 in order to investigate the possibility of using low frequency electromagnetic waves to detect and monitor oil contamination of soils a series of laboratory measurements were performed a new measurement system to monitor the resistivities of soil and sand samples while samples are being contaminated by diesel oil is presented the frequency used in measurements is 100 khz since the measurement system is composed of coil type transmitters and receivers there is no need for electrodes to be in contact with samples the contamination process is simulated using diesel oil dripping on top of soil and sand samples the conductivity distributions in samples along the sample length are recorded as a function of time water wet sand and soil samples were measured during diesel oil contamination the measured data show that the conductivities of soil and sand samples change during the contamination process the change in resistivity for measured samples before and after diesel oil contamination is in the range of 20 to 50 giving a reflection coefficient change in the low frequency limit of 4 7 to 7 this amount of change in the reflection coefficient makes it very challenging to detect and monitor oil contamination based on em reflection from the contaminants the results suggest that em methods based on propagation and induction such as tomography and borehole induction could be used for this purpose

atomic h c ratio of kerogen as an estimate of thermal maturity and organic matter conversion in recent years the atomic h c hydrogen to carbon ratio of kerogen as a way to assess the quality of organic matter in source rocks has been overlooked in favor of the more easily determined rock eval hydrogen index rock eval pyrolysis provides fast inexpensive quantitative mg hc g rock data without requiring kerogen isolation from the rock because of the general scatter in the data many source rock interpreters consider rock eval pyrolysis to be a screening analysis in this paper i describe the benefits of using h c ratios in source rock evaluations and present new correlations between atomic h c ratios and thermal maturity organic matter conversion and expulsion volumetrics atomic h c ratios of pyrolyzed kerogens have been correlated to the extent of thermal conversion of organic matter for both type i and type ii kerogens the excellent agreement between stoichiometric calculated hydrogen and carbon loss to observed losses from hydrous pyrolysis maturation experiments suggests that kerogen h c ratios are excellent indicators of thermal maturity for end member kerogen types these data also offer a method to estimate percent organic matter conversion provided that both the initial and present h c ratios of the kerogen are known present h c ratios can be measured and initial h c ratios can be reasonably estimated from microscopic organic analysis of kerogen for oil prone source rocks typical immature type i kerogens have h c ratios of 1 35 1 50 whereas type ii kerogens have h c ratios of 1 20 1 35 correlations of the amount of expelled oil in hydrous pyrolysis experiments to atomic h c ratio of the spent kerogen offer exploration geologists a quick estimate of oil expulsion volumes based on hydrous pyrolysis experiments measured h c ratios and calculated original toc total organic carbon values first order volumetric approximations were made on three basins containing mature source rocks results compared favorably with published approximate oil in place estimates for the williston basin bakken shale los angeles basin nodular shale and the illinois basin new albany shale

assessment of organic richness and hydrocarbon generation potential of raniganj basin shales west bengal india abstract high energy prices and severe energy shortage has led shale gas to become the focus of study and exploration in many countries india like many other countries around the world with shale gas potential recognizes the strategic importance of developing its shale gas resources for the purpose of shale gas assessment the authors have selected sixty six borehole shale samples of different formations from different parts of raniganj basin west bengal india rock eval pyrolysis and total organic carbon toc analysis and petrographic characterization of the shales were carried out shales from barakar lower permian barren measures upper permian and raniganj formation upper permian are marked by good to excellent toc content input of type iii organic matter and are capable of generating oil and thermogenic gas upon thermal cracking igneous intrusives dykes and sills in the formations occurring in and around the areas of sitarampur si and kulti ku in western part of the basin might have resulted in cooking of the shales increasing their maturities estimated vitrinite reflectance vro as indicated by the barren measures shales of shallow depths from the above mentioned areas majority of the samples are marked by low oxygen index oi values

geochemical petrographic and petrophysical characterization of the lower bakken shale divide county north dakota abstract the lower bakken shale is a key member of the bakken petroleum system which is a prolific unconventional accumulation in north america unconventional accumulations have unpredictable lateral variations in hydrocarbon production due to a variety of factors including porosity permeability and other rock properties therefore understanding the geochemical source rock potential petrological and petrophysical properties of these units is essential in evaluating the hydrocarbon potential for the lower bakken shale this study utilized cores from four wells within three fields in divide county north dakota with samples collected for rock eval pyrolysis organic petrology petrographic thin section studies xrd sem porosity pore size and pore fluid distribution helium porosimetry and nmr t2 porosity techniques were used to estimate porosity and also to check the quality of the results and avoid discrepancies results showed that maturity in the study area varies from immature to early mature using tmax and solid bitumen reflectance organic petrology showed the dominance of solid bitumen and marine alginites which confirms the type ii kerogen identified from pyrolysis and marine depositional environment in the study area major organic matter types identified from sem studies involve stringy om om mineral admixture particulate om and pure om which host the majority of the organic matter pores furthermore pore types identified from sem include mineral matrix pores organic matter pores and microfracture pores porosity values based on both helium and nmr varies but the difference was nominal and attributed to the presence of abundant clay minerals pore sizes are distributed within micropores mesopores and macropores with thermal maturity toc and clay mineral proportion having a major influence on pore distribution clay bound water was identified to be the dominant fluid within the shale samples using the t2 cutoff values and supporting evidence from the abundance of clay matrix porosity

hydraulics of epiphreatic flow of a karst aquifer abstract the nature of epiphreatic flow remains an important research challenge in karst hydrology this study focuses on the flood propagation along the epiphreatic system of reka timavo system kras carso plateau slovenia italy it is based on long term monitoring of basic physical parameters pressure level temperature specific electric conductivity of ground water in six active caves belonging to the flow system the system vigorously responds to flood events with stage rising 100 m in some of the caves besides presenting the response of the system to flood events of different scales the work focuses on the interpretation of recorded hydrographs in view of the known distribution and size of conduits and basic hydraulic relations furthermore the hydrographs were used to infer the unknown geometry between the observation points this way the main flow restrictors overflow passages and large epiphreatic storages were identified the assumptions were tested with a hydraulic model where the inversion procedure was used for an additional parameter optimisation time series of temperature and specific electric conductivity were used to assess the apparent velocities of flow between consecutive points

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

the influence of extractable organic matter on vitrinite reflectance suppression a survey of kerogen and coal types abstract the vitrinite reflectance suppression literature shows that while bitumen impregnation of the vitrinite group is often invoked as a significant contributor to suppression its existence is not often supported by petrological evidence this study examines bitumen impregnation as a factor in vitrinite suppression by comparing the vitrinite reflectance of source rock and coal samples before and after solvent extraction bitumen often defined as organic matter soluble or extractable in certain organic solvents should be removed by soxhlet method solvent extraction using chloroform removing the extractable bitumen should restore the suppressed reflectance to its true higher value however the solvent extracted samples averaged 0 014 r v less than that of the unextracted samples we conclude from these results and from other published data that reflectance suppression by bitumen impregnation in the vitrinite maceral group above the huminite stage of gelification is seemingly a rare phenomenon and whose effect on suppressing vitrinite reflectance is typically negligible

cadalenes and norcadalenes in organic rich shales of the permian irati formation parana basin brazil tracers for terrestrial input or also indicators of temperature controlled organic inorganic interactions abstract cadalene isocadalene and a series of norcadalenes were identified in black shales of the permian irati formation in the northeastern and central eastern parana basin brazil the origin of their isomers with an isopropyl substituent is potentially related to higher plants and likely reflects the spreading of pteridophytes and gymnosperms after the glaciation of southern gondwana a general increase in the relative abundance of isocadalene 1 6 dimethyl 3 isopropylnaphthalene the isomer co occurs in with increasing thermal maturity at the base of the amaral machado quarry northeastern basin and refers to the acid catalyzed rearrangement of cadalene 1 6 dimethyl 4 isopropylnaphthalene the isomer due to the presence of montmorillonite via an organic inorganic interaction this localized and incipient maturation can be related to diabase sills of the serra geral formation similar maturation due to heating also affected the distribution of the norcadalenes by thermally stabilizing their isomers with an isopropyl substituent in addition to the formation of related compounds with an ethyl substituent based on this a norcadalene ratio is proposed which is the sum of the 1 6 dimethyl 4 ethylnaphthalene and 1 6 dimethyl 3 ethylnaphthalene over the sum of the 1 isopropyl 4 methylnaphthalene and 1 isopropyl 7 methylnaphthalene the results of this ratio and the established cadalene ratio resemble each other whereas samples from the sao mateus do sul quarry central eastern basin were not affected by thermal maturation and are characterized by a uniform distribution of the cadalenes and norcadalenes

geochemical and petrographic analyses of new petroleum source rocks from the onshore upper jurassic and lower cretaceous of lebanon abstract the recent interest in the lebanese petroleum potential led to new studies mainly concerning marine petroleum source rocks without taking in consideration the dysodiles and other associated facies from the upper jurassic and the lower cretaceous these organic rich outcrops of metric thickness max 3 m are of limited lateral extension and often found next to volcanic deposits sixty three samples were collected from 25 different localities and were subdivided into three facies that are presented in this paper i dysodiles formed by the superposition of millimetric layers that are easy to separate ii dysodiles like with distinct but more compacted layers iii non dysodiles where the layering is not visible the aim of this work is to assess the origin of these organic rich rocks and to evaluate their source rock potential we used herein rock eval pyrolysis elemental analysis palynofacies observation organic petrography and molecular geochemical analyses rock eval pyrolysis reveals a very good to excellent source rock potential for all above cited rock types with average total organic carbon toc of 14 7 for the dysodiles 19 12 for the dysodiles like and 13 9 for the non dysodiles hydrogen index hi and oxygen index oi values indicate a type i to ii kerogen for the dysodiles average hi 649 162 mg hc g toc type i to ii kerogen for the dysodiles like average hi 340 182 mg hc g toc and type iii kerogen for the non dysodiles average hi 145 42 mg hc g toc the dominance of fluorescent amorphous organic matter aom and alginite macerals confirm an algal bacterial source of organic matter for the dysodiles the presence of opaque aom phytoclasts sporinites and cutinites macerals suggests a variable terrestrial organic matter input for the dysodiles like and non dysodiles maturity parameters such as tmax values on average 428 7 c for dysodiles 429 6 c for dysodiles like and 424 10 c for non dysodiles vitrinite reflectance 1 indicate that the organic matter is still thermally immature the present study sheds light on the long forgotten dysodile shales and similar material and their importance as potential source rocks or oil shales a comparison with local and regional source rocks is provided in order to emphasize the specific character of the dysodile deposits

geochemical screening of source rocks and reservoirs the importance of using the proper analytical program abstract geochemical screening is routinely integrated into larger exploration and sometimes development programs that also include assessments of the geological setting petrophysics mechanical properties of the rock etc the rock eval analytical equipment and its classical basic bulk rock method have been developed mainly to characterize potential source rock intervals in petroleum systems however with the increasing interest in unconventional plays it has been recently demonstrated that the use of modified pyrolysis temperature regimes improves the quantification of hydrocarbons still present in oil impregnated samples in spite of their availability the use of such modified pyrolysis temperature regimes still remains scarce among users of pyrolysis data e g exploration geologists and geochemists reservoir engineers petrophysicists and other geoscientists several cases were selected to portray how different analytical programs are necessary to obtain less biased and more accurate answers to critical questions during prospect and play evaluations and appraisals samples originating from conventional and unconventional plays in the greater permian basin of west texas wolfcamp spraberry formations the dj basin in colorado niobrara formation the williston basin lower bakken shale and source rock reservoirs in the middle east were analysed each using three known different pyrolysis methods namely the institut fran ais du petrole s basic bulk rock reservoir and shale play the shale play and reservoir pyrolysis methods yield oil in place estimates 20 42 higher than those yielded by the basic bulk rock method on the same sample e g for the niobrara formation 87 bbl oil ac ft bulk method 118 bbl oil ac ft reservoir method 119 bbl ac ft shale method for the lower bakken 194 bbl oil ac ft bulk method 246 bbl oil ac ft shale method in addition a mature source rock interval believed to contain gas prone organic matter type iii based solely on toc and pyrolysis data was re interpreted as composed mainly of amorphous oil prone kerogen following a multi component study which included transmitted and reflected light organic petrography these results present unequivocal evidence that underestimating the importance of selecting the proper analytical program can change interpretations dramatically