thermal maturation potential source rocks and hydrocarbon generation in mesozoic rocks lougheed island area central canadian arctic archipelago abstract significant oil and gas accumulations occur in and around lougheed island arctic canada where hydrocarbon prospectivity is controlled by potential source rock distribution and composition the middle to upper triassic rocks of the schei point group e g murray harbour and hoyle bay formations contain a mixture of types i and ii organic matter tasmanales marine algae amorphous fluorescing bituminite these source rocks are within the oil generation zone and have hi values up to 600 mg hc g corg the younger source rocks of the lower jurassic jameson bay and the upper jurassic ringnes formations contain mainly gas prone type ii iii organic matter and are marginally mature vitrinite reflectance profiles suggest an effective geothermal gradient essentially similar to the present day gradient 20 to 30 c km maturation gradients are low ranging from 0 125 to 0 185 log ro km increases in subsidence rate in the early cretaceous suggest that the actual heat flow history was variable and has probably diminished from that time the high deposition rates of the christopher formation shales coincide with the main phase of rifting in aptian albian times uplift and increased sediment supply in the maastrichtian resulted in a new sedimentary and tectonic regime which culminated in the final phase of the eurekan orogeny burial history models indicate that hydrocarbon generation in the schei point group took place during rifting in early cretaceous long before any eurekan deformation

the albian oceanic anoxic events record in central and northern tunisia geochemical data and paleotectonic controls the albian organic rich successions of the lower part of the fahdene formation albian to cenomanian tunisia were studied using sedimentology analysis of carbonate contents and observation of thin sections bulk organic geochemistry rock eval pyrolysis and molecular biomarker distributions the selected outcrops cover different structural domains from western central tunisia jebel hamra to the diapir zone or the tunisian trough koudiat berkouchia jebel ghazouan and ain asker from the southwest to the northeast respectively total organic carbon values between 0 17 and 3 43 evidenced the record of the albian oceanic anoxic events oae1b and oae1c in this southern tethys margin rock eval data and molecular biomarkers n alkanes steranes and terpanes revealed thermally mature organic matter om consisting of a mixed type ii iii om marine planktonic and continental origins the abundant tricyclic terpanes c30 17 h diahopanes and the regular decrease of homohopanes c31 to c35 in the terpane series were also indicative of a high contribution of bacterial om that had been developed under stagnant dysoxic anoxic environments

distribution and structure of hydrocarbons in four organic rich ordovician rocks abstract organic matter in four north american rocks of ordovician age has been analysed using geochemical and optical techniques including reflected light and fluorescence microscopy rock eval pyrolysis elemental analysis of isolated kerogens gas chromatography gc and gas chromatography mass spectrometry gc ms of hydrocarbons in the solvent extracted bitumens the samples analysed were guttenberg oil rock and black shales from the vinini womble and big fork formations in the united states the origin of some of the biomarkers found in the bitumen and the vitrinite particles observed in reflected light are discussed briefly with reference to possible algal and bacterial precursors the results indicate that the four samples are potentially excellent oil source rocks although the guttenberg oil rock is too immature to have generated a substantial quantity of hydrocarbons

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

regional thermal maturity in the franklinian mobile belt melville island arctic canada abstract the thermal maturity and source rock potential of the palaeozoic sediments in the franklinian mobile belt melville island arctic canada have been studied using reflected light microscopy of approximately 400 polished whole rock samples organic matter in the palaeozoic strata of the franklinian mobile belt is represented mainly by bitumen in the ordovician and silurian and a combination of liptinite and vitrinite in the devonian different bitumen types have been identified depending on their morphology reflectance range and association to the enclosing mineral matrix thermal maturity of the palaeozoic strata based on vitrinite equivalent reflectance calculated from bitumen reflectance is high an indication that the strata are in the overmature stage of hydrocarbon generation and that only dry gas should be expected the presence of numerous types of bitumen indicates that hydrocarbons have been generated and migrated through the sediments regional variations in the thermal maturity of palaeozoic sediments in the franklinian mobile belt are mostly a function of depth of burial which is affected by subsidence folding and amount of erosion

unusual biomarker maturation ratio changes through the oil window a consequence of varied thermal history abstract saturated and aromatic biomarker ratios continue to change systematically through the oil window and into the gas condensate window to high vitrinite reflectances r o 1 16 in mature marine and lacustrine mesozoic clastic samples from a south african basin two of the ratios reverse above r o 0 9 these unusual maturation effects result from isolated periods of high rates of maturation increase the basin cooled regionally after the break up of gondwana but high heating rates prevailed during the late cretaceous early tertiary as africa moved across a hotspot and again in the late tertiary as a result of a possible hotspot and hydrothermal event

surface topographic effects at arrays and three component stations abstract a unified method of slowness analysis has been applied to the noress and arcess arrays and to the three component stations within these arrays with the following results 1 there is a relatively large scatter in the three component solutions for events from the same source region and 2 there are significant differences between the solutions at the different three component stations evidence is presented that a uniform half space model is inadequate to derive slowness solutions from three component data layering of the crust and upper mantle affect the surface response at long periods and surface topography and near surface structure perturb the surface particle motion and slowness solutions especially at short periods topographic effects are evaluated by means of numerical simulations based on a newly developed multiple scattering method the theoretical results explain up to about half of the observed anomalies in the three component solutions on the other hand the array solutions based on vertical component phase delays are relatively stable since the nongeometrical phase perturbations are negligible

organic petrology and rockeval analysis of the lower carboniferous emma fiord formation in sverdrup basin canadian arctic archipelago abstract samples of the lower carboniferous emma fiord formation from two localities in the sverdrup basin of arctic canada were examined using reflected white and fluorescent light the samples from kleybolte peninsula on ellesmere island show a relatively high level of thermal maturity in contrast those from grinnell peninsula on devon island are immature to marginally mature and include subbituminous coals and oil shales two types of oil shales are distinguished on the basis of liptinite content mineral matrix rockeval pyrolysis analysis and concentration of boron one is characterized by a liptinite rich clay carbonate matrix with a relatively high hydrogen index and boron content and the other by a liptinite poor carbonate matrix with a relatively low hydrogen index and boron content hydrogen rich components of these shales consist of alginite matrix bituminite and minor amounts of exsudatinite and sporinite kerogen types iii and iv comprise only minor components of the organic matter thermal maturity of the grinnell peninsula oil shales increases with depth matrix bituminite in these oil shales has seeped into cavities and microfractures in the kerogen types iii and iv forming exsudatinite the distribution and character of the organic constituents and also the concentration of boron in these samples indicate a fresh to brackish water environment

comparison of source rock geochemistry of selected rocks from the schei point group and ringnes formation sverdrup basin arctic canada abstract organic rich from the schei point group middle to late triassic in age and the ringnes formation late jurassic from the sverdrup basin of the canadian arctic archipelago have been geochemically evaluated for source rock characterization most samples from the schei point group are organic rich 2 toc and are considered as immature to mature oil prone source rocks kerogen types i i ii iia and ii iia these kerogen types contain abundant aom1 aom2 and alginite tasmanales nostocopsis leiosphaeridia acritarch and dinoflagellate with variable amounts of vitrinite inertinite and exinite samples from the ringnes formation contain dominant vitrinite and inertinite with partially oxidized aom2 alginite and exinite forming mostly immature to mature condensate and gas prone source rocks kerogen type ii iii iib iii and a few ii iia schei point samples contain higher bitumen extract saturate hydrocarbons and saturate aromatic ratio than the ringnes samples triterpane and sterane dominant c 30 distribution patterns and stable carbon isotope of bitumen and kerogen suggest that the analyzed samples from the schei point group are at the onset of oil generation and contain a mixture of sapropelic algal and minor terrestrial humic organic matter sterane carbon number distributions in the ringnes formation also suggest a mixed algal and terrestrial organic matter type there are some variations in hopane carbon number distributions but these are apparently a function of thermal maturity rather than significant genetic differences among samples pyrolysis gas chromatography mass spectrometry of the two samples with similar maturity shows that the schei point sample generates three times more pyrolyzate than the ringnes sample both samples have a dominant aliphatic character although the ringnes sample contains phenol and an aromaticity that is higher than that of the schei point sample

immature oil and condensate modification of hydrocarbon generation model for terrestrial organic matter petroleum has been found in canadian frontier basins in reservoirs which have undergone low levels of thermal alteration vitrinite reflectance 0 6 ro paraffin indices stable carbon and hydrogen isotope contents pristane to nc17 ratios and diterpenoid biologic markers have been used to assess the level of maturity of the hydrocarbons in the reservoir independently of the level of maturity of the reservoir itself and of the surrounding shale units in the tertiary of the beaufort mackenzie basin naphthenic oils and condensates have been generated from terrestrially derived organic matter in source rocks juxtaposed with the reservoir at reflectance levels of 0 4 to 0 6 ro however condensates discovered in reservoirs which are th rmally immature on the labrador shelf have undergone extensive vertical migration and can be classed as conventional mature to overmature condensates hydrocarbons discovered in the lower cretaceous of the beaufort mackenzie basin and also those of the scotian shelf are more or less in place in that they are at a level of thermal alteration about equivalent to that of the reservoirs in which they are trapped the source for the early oils and condensates is considered to be resinite occurring dispersed in coal fragments the proportion of resinite liptinite and vitrinite in the organic matter of terrestrial source rocks strongly controls both the level of thermal alteration necessary for the section to function as an effective source rock and the ultimate product gas oil or condensate which will be generated

regional maturity as determined by organic petrography and geochemistry of the schei point group triassic in the western sverdrup basin canadian arctic archipelago abstract maturity and source rock potential of organic rich beds in the triassic schei point group in the sverdrup basin arctic canada have been investigated using reflected light microscopy and the results are compared with other maturity parameters determined geochemically i e rock eval and biomarker maturation parameters the samples evaluated belong to the eden bay member of the hoyle bay formation and contain a predominance of marine algal material in the form of tasmanales and dinoflagellates along with mixed terrestrial organics the rock matrix is dominantly carbonate with some shaly input indicating that the rocks were deposited in an iron poor highly euxinic environment with few exceptions there is good agreement between parameters determined using microscopy namely r o max and r gq and geochemical parameters t max hi dia c 27 dia c 27 reg c 27 steranes s s r c 29 steranes the ternary diagram showing the abundance of normalized c 27 c 28 and c 29 regular steranes indicates a mostly marine depositional environment for the schei point source rock this is confirmed by the abundance of marine fauna and flora in these samples analytical results from several different techniques indicate that the source rocks become more mature from the margin towards the axis of the sverdrup basin this is due in part to the increase in overburden of sediments in the axis of the basin also the high thermal conductivity of salt has strongly influenced the maturity of schei point source rocks over the crest of the salt cored structures i e well hazen f 54 and the proximity of salt has enhanced maturation levels at well rock point j 43 the sections investigated were also considered to have an excellent gas potential due to their higher than average toc content

correlation of the canol formation source rock with oil from norman wells abstract the source of the oil at norman wells has long been assumed to have been the canol formation and or the bluefish member of the hare indian formation these two units are stratigraphically above and below the kee scarp formation reservoir unit respectively and are both bituminous shales a wide range of analytical techniques including rock eval pyrolysis solvent extraction and fractionation capillary gas chromatography gas chromatography mass spectrometry and white light and fluorescence microscopy has been used to characterize core samples of these two units and two samples of crude oil from the norman wells field most of the analytical techniques were insufficiently refined to either differentiate the extracts from each other or to make a definitive oil source rock correlation collision activated decomposition coupled with multiple ion detection mass spectrometry gc ms ms did provide sufficient chemical compositional detail of the oils and the two potential sources to demonstrate that the canol formation has been the effective source of the norman wells oil whereas the bluefish member has not petrological analysis of the organic fractions also indicates that although the bulk organic composition of both units may be classified as type ii organic matter significant differences exist between them the bluefish member contains substantial amounts of megaspores whereas the organic matter in the canol formation is largely phytoplankton debris the level of thermal maturity of the core samples ranges from immature to moderately mature in the vicinity of the norman wells field to overmature for the samples obtained to the west and north of the field the level of thermal maturity of the oil was observed to be somewhat higher than that of the samples of the source formation directly above the field it was thus inferred that some lateral migration from more mature areas has occurred but the extent of this migration was not necessarily more than a few to tens of kilometers

geological risk mapping and prospect evaluation using multivariate and bayesian statistical methods western sverdrup basin of canada the current practice of geological risk evaluation at the play level involves substantial subjectivity and rarely considers the spatial correlations among the identified prospects a quantitative procedure using multivariate and bayesian statistical methods is proposed which treats exploration risk evaluation as a two group classification to provide a more objective and reproducible result the spatial correlation among the identified prospects is considered because the proposed approach is applied to the entire evaluation area the exploration risk evaluation of the upper triassic lower jurassic heiberg group structural gas play in western sverdrup basin arctic canada illustrates the method

organic petrology of hat creek coal deposit no 1 british columbia abstract the upper eocene hat creek coal deposits of british columbia canada are one of the thickest lignite to subbituminous coal deposits of the world and comprise 350 550 m of coal samples of sedimentary organic material were taken from a 560 m interval of interbedded shale siltstone and carbonate that was penetrated by corehole 75 106 in the centre of the coal basin and the reflectances of huminite eu ulminite from coal and kerogen from the organic material were determined and petrographical analyses were made the coal deposit contains many leaf and resinite rich horizons and the reflectance of huminite in these horizons in lower than in corresponding horizons containing less liptinite when compared with huminite in adjacent coal beds the reflectance of huminite in shale is lower that in siltstone is similar and huminite associated with carbonate rocks has slightly higher reflectance values the petrological variation in the coal is mainly within the huminite group of macerals the coal at the top of the deposits is lignite r o 0 38 and becomes subbituminous c r o 0 50 at the base the inertinite content is very low indicating a low level of peat fire or oxidation the early stages of transformation of gelinite to macrinite are described the paleoenvironment appeared to be lacustrine as determined by organic petrological analysis of coals and interbedded sediments four major zones each containing many subzones were found paleoenvironments were similar for the a and c zones and also for the b and d zones

organic geochemistry and elements distribution in dahuangshan oil shale southern junggar basin origin of organic matter and depositional environment abstract the dahuangshan oil shale located in the northern bogda mountain on the southern margin of the junggar basin was deposited in a late permian lacustrine environment a combined investigation of element and organic geochemistry was performed to define the source rock potential the paleoenvironment and source of the organic matter thick sequences of oil shales with an average thickness of 638 m were deposited in lucaogou formation which mainly consists of oil shale argillaceous dolomite silty claystone tuff limestone and dolomitic marl a spot of plant stem fossils and abundance of pyrite crystals fishtail and fish skeleton can also be found there analyzed oil shale samples from dahuangshan area are characterized by high total organic carbon toc contents 5 6 34 75 s2 22 65 199 25 mg hc g rock hydrogen index hi 359 1068 mg hc g toc and oil yield 4 9 26 6 indicating the oil shales have excellent source rock potential tmax values 433 453 c show an early to medium maturation stage of organic matter which is supported by organic geochemical maturation parameters all of the obtained kerogen types are types ii and i with oil prone source rock potential dahuangshan oil shale samples are rich in sio2 68 59 followed by al2o3 10 18 and fe2o3 5 43 compared with average shale and north american shale composite nasc analyzed oil shale samples are obviously enriched in p 0 71 there is a significant correlation between al2o3 and fe2o3 mgo k2o mno cu ba co and ni for their association with clay minerals besides the significant correlations between fe2o3 and mno co and ni are considered to result from their similarity on geochemical behavior all selected oil shales are characterized by distinctly sloping light rare earth elements lree trends lan smn 2 70 5 95 accompanied by flat heavy rare earth elements hree trends with distinct eu negative anomalies 0 60 0 73 two slightly different patterns of rees in the oil shale samples are distinguished by the difference in ce depletion and nd anomaly in addition dahuangshan oil shale samples are characterized by short to middle chain n alkanes low carbon preference index cpi values 0 93 1 24 single peak composed of nc20 or nc22 low pr ph 0 41 0 91 relatively high homohop index 0 061 0 99 and high concentrations of c27 sterane indicating reducing deep water and moderate saline environment with prevalent contribution of algae and microorganisms to organic matter accumulation

calculation of organic maturation levels for offshore eastern canada implications for general application of lopatin s method recorded maximum bottom hole temperatures may vary significantly from true formation temperatures because of the effects of drilling fluid circulation a theoretical temperature correction technique was applied to log heading data to compute 191 static temperatures for 64 wells on the scotian shelf a linear regression performed on 140 computed temperatures produced an average geothermal gradient of 2 66 c 100 m correlation coefficient 0 97 a geothermal gradient map constructed from the corrected data shows that areas of thicker sediment accumulation are marked by high geothermal gradients e g abenaki sable subbasins whereas areas of shallow basement coincide with low gradients e g lahave platform canso ridge it is proposed that the major control on the distribution of scotian shelf geothermal gradients is the thermal conductivity of the sediments radiogenic heat production within the sediments and subsurface fluid movement probably contribute to a lesser extent within the basins higher

composition and syngeneity of molecular fossils from the 2 78 to 2 45 billion year old mount bruce supergroup pilbara craton western australia shales of very low metamorphic grade from the 2 78 to 2 45 billion year old ga mount bruce supergroup pilbara craton western australia were analyzed for solvent extractable hydrocarbons samples were collected from ten drill cores and two mines in a sampling area centered in the hamersley basin near wittenoom and ranging 200 km to the southeast 100 km to the southwest and 70 km to the northwest almost all analyzed kerogenous sedimentary rocks yielded solvent extractable organic matter concentrations of total saturated hydrocarbons were commonly in the range of 1 to 20 ppm g g rock but reached maximum values of 1000 ppm the abundance of aromatic hydrocarbons was 1 to 30 ppm analysis of the extracts by gas chromatography mass spectrometry gc ms and gc ms metastable reaction monitoring mrm revealed the presence of n alkanes mid and end branched monomethylalkanes cyclohexylalkanes acyclic isopre noids diamondoids tri to pentacyclic terpanes steranes aromatic steroids and polyaromatic hydrocarbons neither plant biomarkers nor hydrocarbon distributions indicative of phanerozoic contamination were de tected the host kerogens of the hydrocarbons were depleted in 13 c by 2 to 21 relative to n alkanes a pattern typical of although more extreme than other precambrian samples acyclic isoprenoids showed carbon isotopic depletion relative to n alkanes and concentrations of 2 methylhopanes were relatively high features rarely observed in the phanerozoic but characteristic of many other precambrian bitumens molecular parameters including sterane and hopane ratios at their apparent thermal maxima condensate like alkane profiles high mono and triaromatic steroid maturity parameters high methyladamantane and methyldiaman tane indices and high methylphenanthrene maturity ratios indicate thermal maturities in the wet gas gener ation zone additionally extracts from shales associated with iron ore deposits at tom price and newman have unusual polyaromatic hydrocarbon patterns indicative of pyrolytic dealkylation the saturated hydrocarbons and biomarkers in bitumens from the fortescue and hamersley groups are characterized as probably syngenetic with their archean host rock based on their typical precambrian molecular and isotopic composition extreme maturities that appear consistent with the thermal history of the host sediments the absence of biomarkers diagnostic of phanerozoic age the absence of younger petroleum source rocks in the basin and the wide geographic distribution of the samples aromatic hydrocarbons detected in shales associated with iron ore deposits at mt tom price and mt whaleback are characterized as clearly archean based on their hypermature composition and covalent bonding to kerogen copyright 2003 elsevier ltd

the occurence of unusual c27 and c29 sterane predominances in two types of oman crude oil abstract two types of oman crude oils reveal unusual sterane distributions type a which is the more common 74 examples is characterised by a predominance of c 29 iso and normal steranes and generally none or only very low relative concentrations of rearranged steranes the triterpanes are characterised by the predominance of the c 29 17 h 21 h norhopane over the c 30 17 h 21 h hopane and non predominant c 20 c 30 tricyclic terpanes the c 29 steranes of this type of crude were not derived from the c 29 sterols of land plant origin frequently proposed as the source of c 29 steranes since there is good geological evidence that these crudes were generated from a pre cambrian source rock a geological period when land plants did not exist the type b crude oil 11 known examples is characterised by a strong predominance of c 27 iso normal and rearranged steranes relatively lower concentrations of 17 h 21 h hopanes and relatively high concentrations of c 20 c 30 tricyclic terpanes the remarkably different biomarker characteristics of these crude oils imply that the organisms active in the depositional environment of the respective source rocks were significantly different

hubble space telescope observations of the 1990 equatorial disturbance on saturn zonal winds and central meridian albedos abstract two sets of hubble space telescope hst data obtained in august 1990 and november 1990 are compared with voyager 1 and 2 data acquired in 1980 and 1981 a rare disturbance developed in the equatorial region of saturn in late september 1990 due to the large equatorial wind shear this disturbance generated inhomogeneous bright cloud structures in the equatorial region that extended to 25 north latitude in november 1990 meridional albedo scans and wind measurements from the voyager northern spring equinox and the hst northern summer observations are compared differences in average zonal winds in the images obtained with the green f547m and the methane f889n filters are interpreted as evidence of vertical shear in the zonal winds longitudinal variations in the equatorial zonal winds are interpreted as evidence of interaction between the storm nucleus generated during the disturbance and the local wind field

optical properties of organic matter in relation to thermal gradients and structural deformation the general response of macerals to the coalification process the effectiveness of organic geochemical and petrological parameters as estimators of coalification and the applicability of different microscopical parameters in the assessment of rank are reviewed the central role of vitrinite reflectance as the most widely used estimator of coalification from brown coals to the low grade metamorphic zone is established on the basis of its relatively uniform variation with rank specificity ease and rapidity of measurement and cheapness factors influencing the optical properties ofvitrinites are considered temperature has the dominant influence in modifying optical properties with rank but time static pressure and stress can all have significant influences upon the course of optical properties depending upon particular geological conditions static pressure has a retarding effect on the coalification process but it is also responsible for creating increasing anisotropy within the condensing aromatic structures as rank rises hydrostatic pressures and pore pressures can contribute to the overpressuring of sediments thus affecting their thermal conductivities and consequently the rate of coalification stress is responsible for the development of biaxicity in the reflectance indicatrix fast and high levels of heating from igneous bodies cause textural effects on vitrinites as a result of carbonization that are quite different from those of coalification recognizing these different influences upon the optical properties of vitrinites examples are given of the use and application of vitrinite reflectance in the preparation of rank maps in the burial histories of basins in the timing of coalification in relation to orogenesis and igneous activity and in the zones of anchimetamorphism and low grade metamorphism consideration is also given to the problem of provincialism in correlations between chemical and physical parameters and to the future development of optical studies in organic petrology and their relation to organic geochemical investigations

basin induced love waves observed using the strong motion array at fuchu japan phases have been observed in the s wave coda of local earthquakes recorded at the fuchu strong motion array located in the kanto basin in the western suburbs of tokyo japan these phases are often larger than the direct s wave at a period of 1 sec because these phases are observed only on horizontal components at surface sites and are weakly observed at only the shallowest 150 m of a number of borehole sites they are interpreted as love waves particle motions indicate significantly off azimuth travel directions the fuchu array is too sparse to allow the application of standard array analysis to determine the origin of these phases instead we use a combination of three component polarization enveloping and slant stack techniques that allows propagation directions to be reasonably well determined 10 however group slownesses are more difficult to obtain precisely 1 to 2 sec km using these results and assuming that the love waves are generated by the scattering of s waves at the earth s surface we estimate locations of scattering points we find that the scattering occurs along a short segment of the kanto basin boundary for widely distributed earthquake source locations we believe that this segment is important because it is the closest part of the basin boundary to the observation sites the existence of these basin induced love waves violates backscattering models for the generation of the coda of local earthquakes this must be kept in mind when applying coda techniques to sediment basin sites at periods of 1 sec or more

source rock lithology prediction based on oil diacholestane abundance in the siliceous clastic akita sedimentary basin japan in an effort to predict the source rock lithology from oil biomarkers in the akita basin the relationship of diacholestane abundance to clay mineral content thermal maturation and the oxic anoxic depositional conditions of representative mudstone samples has been investigated the relative diacholestane abundance of samples with similar maturity levels increases with increasing clay mineral content the oxic anoxic depositional conditions of the samples estimated by c35 homohopane index are less influential for diacholestane formation in the case of the yabase oil field samples a crossplot of the diacholestane abundance versus ethylcholestanes 20s 20s 20r and clay mineral content was applied to evaluate the source rock lithology of the yabase oils the source of this oil is consequently predicted to be the clay poor siliceous rocks of the miocene onnagawa formation although this study did not achieve quantitative clay content prediction the results demonstrate that this approach is useful for the characterization of source rock lithology especially for moderately mature oils

thermal maturity and hydrocarbon potential of the sedimentary succession from the hecla field in sverdrup basin arctic canada abstract the thermal maturity and source rock potential of the upper palaeozoic and mesozoic sediments in the hecla field melville island arctic canada have been studied using reflected light microscopy and rock eval pyrolysis approximately 250 polished whole rock samples were examined and their reflectance r 0 random measured in addition approximately 100 samples were subjected to rock eval toc analyses hydrogen rich organic matter in the schei point group sediments is dominated by alginite tasmanales dinoflagellate cysts with minor amounts of sporinite cutinite resinite and liptodetrinite in an amorphous fluorescing matrix vitrinite reflectance in cretaceous sediments ranges from 0 41 to 0 54 in jurassic sediments it ranges from 0 43 to 0 64 and in triassic sediments from 0 50 to 0 65 the triassic schei point group calcareous shales and marlstones contain organic matter mainly of marine origin whereas the predominantly terrestially derived organic matter present in the jameson bay lower jurassic and in the upper jurassic to lower cretaceous deer bay formations have ower toc only the ringnes formation has a toc content of equivalent to or greater than schei point source rocks within the schei point group the cape richards and eden bay members of the hoyle bay formation are slightly richer in toc than the murray harbour formation cape caledonia member higher average toc contents 3 0 have been reported in the cape richards and eden bay members in almost all hecla drillholes variations in the level of thermal maturity of mesozoic sediments in the hecla field are a function of burial depth the stratigraphic succession thickens towards the main sverdrup basin depocentre located in a n ne direction the pattern of the isoreflectance contours at the top of the triassic barrow formation is similar to that of formation boundary lines of the same formations an indication that present day maturation levels are largely controlled by basin subsidence

variation of maturity indicators optical and rock eval with respect to organic matter type and matrix lithology an example from melville island canadian arctic archipelago abstract the variation of maturity indicators with respect to mineral matrix and organic matter types was examined from the mesozoic succession of melville island arctic canada the t max values of non marine deltaic samples show a much greater degree of scattering with respect to vitrinite reflectance whereas the marine samples show a narrow distribution this behaviour is most likely to be a consequence of the differences in the chemical properties of terrestrial versus marine organic matter which is a function of the organic matter type and of the depositional environment the non marine deltaic samples also show higher t max values than their marine counterparts an indication either of the higher degree of oxidation of the non marine deltaic samples or of the fact that type iii organic matter has intrinsically higher t max values than types i and ii organic matter at the same maturity level based on the relationship between hydrogen index hi and vitrinite reflectance ro it appears that marine organic matter is more sensitive high negative correlation to thermal maturity changes than non marine deltaic organic matter no clear correlation between s 2 hydrocarbon yield and ro maturity could be seen in the suite of samples both fluorescence parameters max and r g quotient increase with maturity but the trends have different slopes for the various macerals a function of their marine or non marine origin

evaluation of organic maturity and hydrocarbon source potential of the ringnes formation sverdrup basin arctic canada abstract organic rich shales are common in the ringens formation member an oxfordian kimmeridgian argillaceous unit which is widespread in the sverdrup basin of the canadian arctic archipelago the shales and siltstones of the ringnes are laminated to burrowed and are interpreted to have been deposited under sub oxic conditions in a mid to outer shelf setting the organic matter om which is up to 11 wt has relatively low h1 and oi values rock eval toc data organic petrography and the environment of deposition of the ringnes are interpreted to infer that the organic matter in basin margin samples is mainly of terrestrial origin with a variable but minor marine component in the axial region of the basin the om appears to be of a mixed marine and terrestrial origin and has been partially oxidized the high organic content is attributed to sedimentation rates high enough to bury the organic rich sediments before complete destruction by aerobic bacteria and benthic scavengers the organic content and hi values increase towards the axis of the basin the thermal maturity of the ringnes shales varies from immature on the basin margins to mature along the basin axis in the eastern and central portions of the basin however the ringnes shales are overmature at many localities due to the presence of diabase sills and dykes which were intruded in early cretaceous by contrast the maturity of the ringnes is anomalously low over the crests of large salt cored structures rock eval toc data and petrographic evidence indicate that the ringnes shales have potential to generate significant amounts of thermogenic gas at low levels of thermal maturity

scattering of regional pn by moho topography the often observed relatively large amplitudes in the later part of the pn signal cannot be explained with the traditional interpretation of pn in 1 d crust mantle models to determine the cause of these characteristics we have analyzed in some detail the noress array records of pn from a suite of quarry blasts in s w norway application of wide band frequency wavenumber analysis to these records confirms that there is a slowness and azimuth anomaly associated with the dominant part of the wavetrain and that it is confined to a particular frequency range moreover the scattering source of the anomaly is determined to be at moho depth which is consistent with the concept of scattering by topographic relief we demonstrate the viability of this concept by means of numerical experiments showing that for realistic models of topography the energy flux of scattered p can dominate the specular flux i e the flux in the direction defined by the ray crossing a plane interface for incidence angles approaching the critical angle of pn since the effects appear to be systematic we have the possibility to calibrate the pn parameters for event location and velocity determination purposes

fluorescence properties of palaeozoic oil prone alginite in relation to hydrocarbon generation williston basin saskatchewan canada abstract alginite macerals the oil prone microscopic components of hydrocarbon source rocks fluoresce in the visible region when irradiated with ultraviolet light the fluorescence properties max and red green quotient of coccoidal unicellular and filamentous alginite macerals were investigated in palaeozoic potential hydrocarbon source rocks northern williston basin saskatchewan canada this study documents the variation in fluorescence properties of alginite during thermal maturation and the onset of petroleum generation values of max nm of disseminated coccoidal gloeocapsomorpha alginite from upper cambrian siliciclastics and upper ordovician carbonates show different magnitudes of red shift with increasing thermal maturity gloeocapsomorpha prisca disseminated alginite and g prisca stromatolitic alginite from upper ordovician kukersites exhibit unique fluorescence properties with increasing thermal maturity the former undergoes a greater red shift in fluorescence than the latter over an 1800 m change in depth of burial devonian and mississippian unicellular prasinophyte leiosphaeridia and tasmanites alginite show a minimal change in fluorescence properties max 450 500 nm between vitrinite reflectance values of 0 35 and 0 65 ro beyond 0 65 ro vitrinite reflectance prasinophyte alginites show a marked red shift to a max of 560 600 nm this phenomenon is coincident with peak hydrocarbon generation from a type ii filamentous alginite bituminite kerogen within middle devonian carbonate source rocks a comparison of the fluorescence properties of palaeozoic prasinophytes with the fluorescence properties of mesozoic prasinophytes reveals that the latter undergo a substantially greater red shift in max with increasing thermal maturity relative to the former this conspicuous difference is interpreted as a reflection of the well documented distinct difference in species and abundance of leiosphaeridia and tasmanites alginite between the geological eras

investigation of azimuth residuals observed at stations of the gsett 3 alpha network the gsett 3 experiment was conducted for more than two years and the international data center idc reported more than 20 000 events for 1995 in the reviewed event bulletins reb we have used this data base to investigate the location bias of arrays and selected three component stations in the alpha network for which the recorded data is automatically processed to determine earthquake locations in near real time the alpha network which consists of 14 arrays provides estimates of event azimuths determined by f k processing we selected 19 three component stations that were operated all or most of 1995 and for which event azimuth was estimated by polarization analysis only events with epicentral distances of less than 100 were considered in order to exclude phases with steep incidence angles associated with unreliable azimuth estimates teleseismic p phases and the major regional and local phases were examined only data for which a signal to noise ratio was given were included in this analysis the signal to noise ratios were used as a weighting factor for the statistical parameters and the graphical representation of the azimuth residuals the preliminary analysis of azimuth residuals identified some arrays that give significantly erroneous azimuths in some cases the error is systematic in other cases it is random one array with systematic azimuthal bias is cmar this array shows positive residuals for event paths from the south while phases for events with paths from the north show negative residuals similar patterns which strongly suggest azimuthal bias are observed for pdar txar and spits in the case of mjar the large azimuthal errors observed particularly for regional and local distances are not a function of direction the scatter in the azimuth residuals is much larger for 3 c stations than for the arrays clear systematic errors were identified for schq and cpup which show constant offsets and at vnda which has negative residuals for events to the north and positive residuals for events from the south the most significant azimuth bias was observed for pdy where the azimuth residuals change from about 90 to more than 90 at backazimuths near 120 meaning that all rays appear from the northwest

saturate biomarkers and aromatic sulfur compounds in oils and condensates from different source rock lithologies of kazakhstan japan and russia abstract representative petroleums from the seven basins of kazakhstan russia and japan were analyzed using gas chromatography with dual fid fpd and gc ms the present study has shown that the deviation in relative concentrations of aromatic sulfur compounds in petroleums could be related to the type of source rock all oil samples were classified into three groups on the basis of the relative abundance of aromatic sulfur compounds biomarker distribution and lithology of source rock the first group of oils derived from carbonate source rocks is rich in aromatic sulfur compounds such as methylbenzothiophenes mbt and methyldibenzothiophenes mdbt and poor in dibenzothiophene dbt compared to methylated homologs the second group derived from siliceous and siliceous carbonate source rocks contains various types of benzothiophenes and dibenzothiophenes including dbt the third group originating from argillaceous rocks has lower concentrations of aromatic sulfur compounds and especially of methylated benzothiophenes

an object based model for predicting the locations of undiscovered oil and gas resources western sverdrup basin canada a petroleum pool that has a common petroleum water contact and a distinctive pressure regime is a fundamental unit of petroleum accumulation and can be treated as a natural object the prediction of the undiscovered petroleum pool locations can be performed employing a method similar to that used to predict sand channels in a clastic reservoir formation this paper presents an example for the prediction of possible locations of undiscovered petroleum pools in the western sverdrup basin arctic canada using an object based model this model simultaneously considers the information from the basic geological conditions for the formation of petroleum pools and the spatial correlation among the pools the simulated results indicate that the object based model improves predictions of petroleum occurrences by incorporating spatial correlation information into the model and by checking the consistency of the model with geological constraints

maturity studies and source rock potential in the southern sverdrup basin arctic canada abstract the purpose of the study is to better understand the relationship between organic matter optical properties and the presence of potentially large oil and gas accumulations in arctic canada the type and thermal maturity of the dispersed organic matter of the mesozoic formations in the southern sverdrup basin melville island have been studied using organic petrology and rock eval pyrolysis all types of organic matter are present in the strata of mesozoic age hydrogen rich liptinite is dominated by alginite botryococcus and tasmanites dinoflagellate cysts and amorphous fluorescing matrix sporinite cutinite resinite and liptodetrinite made up the lesser hydrogen rich exinite vitrinite reflectance in cretaceous sediments ranges from 0 36 to 0 65 ro in jurassic sediments it ranges from 0 40 to 1 0 ro and in the triassic from 0 45 to 1 30 ro showing an overall increase with depth of burial cretaceous sediments of the deer bay formation are thermally immature and contain organic matter of terrestrial origin the upper jurassic shales of the ringnes formation contain predominantly organic matter of liptinitic and exinitic origin with a considerable vitrinitic input at optimum maturation levels potential source beds of this formation would have a good hydrocarbon generating potential the hydrocarbon potential however would be limited to the generation of gases due to the leanness of the source rocks parts of the lower jurassic jameson bay formation are organic rich and contain a mixed exinitic vitrinitic organic matter botryococcus colonial algae but visible organic matter is dominated by high plant remains mainly spores the schei point group shales and siltstones contain organic matter of almost purely marine origin whereas the predominantly higher plant derived organic matter found in the deer bay jameson bay and partly in the ringnes formations have higher toc among the schei point group samples the cape richards and eden bay members of the hoyle bay formation are richer in toc 2 0 than the murray harbour formation cape caledonia member this may reflect differences in the level of maturity or in the depositional environment more anoxic conditions for the former regional variations in the level of thermal maturity of mesozoic sediments in sverdrup basin appear to be a function of burial depth the mesozoic formations thicken towards the basin centre nne direction reflecting the general pattern of increasing thermal maturity north of sabine peninsula however the regional thermal maturation pattern of the mesozoic is not solely a reflection of the present day geothermal gradient which indicates that anomalous zones of high geothermal gradient may have existed in the past at least since when the mesozoic sediments attained maximum burial depth the contour pattern of the regional variation of maturity at the base of numerous triassic formations is similar to that of the structural contours of the sverdrup basin indicating that present day maturation levels are largely controlled by basin subsidence

wavefield decomposition using ml probabilities in modelling single site 3 component records summary this paper presents a new approach to the analysis of three component digital seismograms earlier approaches used techniques such as principal components to estimate particlemotion using models of p and s waves in this paper the maximum likelihood ml estimator is preferred because this allows the use of x2 probabilities to test whether energy of a specific wave type p s love or rayleigh is present in addition this analysis allows the joint estimation of azimuth of approach and in cases of p and sv waves also apparent angle of incidence and hence information on apparent velocity for a single three component seismogram the covariance matrix provides only six independent observations thus restricting analysis to rather simple wave models the technique works satisfactorily for p waves whereas shear and surface wave models sometimes prove cumbersome to handle due to correlation between radial and transverse components reflecting complex propagation characteristics in inhomogeneous media this technique has been tested on synthetic data and in such cases works perfectly for all wave types an important aspect of this work has been the visual display of the probability and velocity information as functions of time and azimuth displaying the data in this form provides information on the ray path in a manner similar to analysis performed by seismic arrays practical examples on a variety of siesmic data are given to illustrate the viability of the technique the data cover a broad spectrum of frequencies and applications from broad band teleseismic data 1 hz regional seismic data 10 40 hz seismic profiling data 125 hz and vsp 500 hz recordings