spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

the puguang gas field new giant discovery in the mature sichuan basin southwest china the giant puguang gas field with a proven original in place gas volume of 350 109 m3 12 36 tcfg was discovered in 2003 in the eastern sichuan fold thrust belt of the mature sichuan basin southwest china the field is a combination structural stratigraphic trap closed by lateral depositional change and fault closure the trap evolved from a paleo oil reservoir originating in the triassic jurassic the entrapment of thermal gas which was derived from lower middle silurian and permian source rocks occurred during deep burial in the jurassic cretaceous tertiary quaternary compression transformed the paleotrap into the present gas reservoir gas is contained in the lower triassic feixianguan and the upper permian changxing reservoirs which consist predominantly of dolomitized oolites deposited in shelf and platform margin shoal and backreef environments reservoir quality is characterized by porosity of 1 29 and permeability of 0 01 9664 md with buried depth greater than 5000 m 16 400 ft the discovery of the puguang field exemplifies the successful application of a new play concept and new technology in a mature basin the discovery resulted from a shift in exploration strategy from structures to stratigraphic traps in reef and shoal dolomites and benefited from advanced high resolution seismic techniques the discovery will not only broaden the exploration scope in the sichuan basin but also provide an excellent analog for exploration in other fold thrust belts worldwide

characteristics of a crater glacier at ushkovsky volcano kamchatka russia as revealed by the physical properties of ice cores and borehole thermometry a glacier at the summit of ushkovsky volcano kamchatka peninsula russia was studied in order to obtain information about the physical characteristics of a glacier that fills a volcanic crater the glacier has a gentle surface and a concave basal profile with a maximum measured depth of 240 m at site k2 the annual accumulation rate was 0 54 m a 1 w e and the 10 m depth temperature was 15 8 c a 211 70 m long ice core drilled at k2 indicates that 1 the site is categorized as a percolation zone 2 the stress field in the glacier changes at 180 m depth from vertical and longitudinal compression with transversal extension which is divergent flow to a shear dominated stress field and 3 the frequent occurrence of ash layers can be a good tool for dating the ice core the borehole temperature profiles were considered to be non stationary but the linear profile made it possible to estimate the basal temperature and the geothermal heat flux at k2 assuming constant surface and the basal boundary conditions we constructed two depth age relationships at k2 these predicted that the bottom ages of the ice core were about 511 or 603 years

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

oil retention and porosity evolution in organic rich shales petroleum is retained in shales either in a sorbed state or in a free form within pores and fractures in shales with oil resource potential organic matter properties i e richness quality and thermal maturity control oil retention in general in gas shales organic pores govern gas occurrence although some pores may originate via secondary cracking reactions it is still largely unclear as to how these pores originate here we present case histories mainly for two classic shales the mississippian barnett shale texas and the toarcian posidonia shale lower saxony germany in both cases shale intervals enriched in free oil or bitumen are not necessarily associated with the layers richest in organic matter but are instead associated with porous biogenic matrices however for the vast bulk of the shale hydrocarbon retention and porosity evolution are strongly related to changes in kerogen density brought about by swelling and shrinkage as a function of thermal maturation secondary organic pores can form only after the maximum kerogen retention swelling ability is exceeded at tmax the temperature at maximum rate of petroleum generation by rock eval pyrolysis around 445 c 833 f approximately 0 8 vitrinite reflectance shrinkage of kerogen itself leads to the formation of organic nanopores and associated porosity increase in the gas window

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

experimental investigation of changes in methane adsorption of bitumen free woodford shale with thermal maturation induced by hydrous pyrolysis this study quantifies the effects of organic matter om thermal maturity on methane ch4 sorption on the basis of five samples that were artificially matured through hydrous pyrolysis achieved by heating samples of immature woodford shale under five different time temperature conditions ch4 sorption isotherms at 35 degrees c 50 degrees c and 65 degrees c and pressures up to 14 mpa on dry solvent extracted samples of the artificially matured woodford shale were measured the results showed that ch4 sorption capacity normalized to toc varied with thermal maturity following1 the trend maximum oil 367 degrees c oil cracking 400 degrees c maximum bitumen early oil 333 degrees c early bitumen 300 degrees c immature stage 130 degrees c the langmuir constants for the samples at maximum oil and oil cracking stages are larger than the values for the bitumen forming stages the total pore volume determined by n 2 physisorption at 77 k increases with increased maturation mesopores 2 50 nm in width were created during the thermal conversion of organic matter and a dramatic increase in porosity appeared when maximum bitumen and maximum oil generation stages were reached a linear relationship between thermal maturity and brunauer emmett teller bet surface area suggests that the observed increase in ch4 sorption capacity may be the result of mesopores produced during om conversion no obvious difference is observed in pore size distribution and pore volume for samples with pores 2 0 nm with the increase of thermal maturity based on co2 physisorption at 273 k the isosteric heat of adsorption and the standard entropy for artificially matured samples ranged from 17 9 kj mol 1 to 21 9 kj mol 1 and from 85 4 j mol 1 k 1 to 101 8 j mol 1 k 1 respectively these values are similar to the values of immature woodford kerogen concentrate previously observed but are larger than naturally matured organic rich shales high temperature hydrous pyrolysis might have induced lewis acid sites on both organic and mineral surfaces resulting to some extent in chemical interactions between the adsorption site and the methane c h bonds the formation of abundant mesopores 2 50 nm within organic matter during organic matter thermal maturation makes a great contribution to the increase in both bet surface area and pore volume and a significant increase in 2 6 nm pores occurs at maximum oil generation and oil cracking to gas ultimately controlling the methane adsorption capacity therefore consideration of pore size effects and thermal maturity is very important for gas in place gip prediction in organic rich shales c 2014 elsevier ltd all rights reserved

diagenetic thermal evolution of organic matter by raman spectroscopy abstract vitrinite reflectance is considered one of the most reliable indicators of thermal maturity in sedimentary basins and is widely used to calibrate numerical models that assess hydrocarbon generation expulsion from source rocks nevertheless ambiguities in vitrinite reflectance can occur from variations in composition and preservation state of organic facies temperature pressure conditions and the abundance of organic matter resulting in incorrect or uncertain assessments of petroleum systems this study presents an original application of raman spectroscopy to assess the diagenesis catagenesis of kerogen between the immature and mid mature stages of hydrocarbon generation kerogens were isolated from 33 intervals of drill cuttings from a 5 km thick oligocene miocene siliciclastic section of the malembo formation lower congo basin angola their raman spectra were obtained and derived parameters were compared to depth and to previously reported equivalent vitrinite reflectance values the best correlations between thermal maturity and raman parameters were found for d g band distance fwhm of the g band d g area ratio ra2 ratio calculated as s dl d dr gl g band ratio and the d g width ratio the raman parameters were not influenced by varying kerogen composition mixed type ii iii the technique offers the potential to reduce the risk of source rock thermal maturity assessment even when organic facies rich in amorphous organic matter are present

structural evolution of organic matter and implications for graphitization in over mature marine shales south china abstract to characterize the degree of organic matter graphitization in the over mature lower paleozoic marine shales from south china a suite of kerogen samples covering different maturity ro ranging from 1 2 to 4 2 were analyzed by laser raman microprobe lrm transmission electron microscope tem and fourier transform infrared spectroscopy ftir techniques chemical structures and related major changes caused by thermal evolution history were systematically discussed the results indicate that with the thermal maturity increasing the aliphatic side chains fall off gradually and the aromatic rings increase continuously the ordered structure of shales continues to enhance leading to the increasing of graphitization degree the parameters of lrm i e position of g and d bands peak position difference rbs full width at half maximum fwhm and intensity ratio id ig highlight the turning point at maturity level around rmcro 3 5 which represents the chemical structure jump of the kerogen this chemical structure jump can be characterized by the continuous decreasing of amorphous carbon before the rmcro exceeded 3 5 and the sharp increasing degree of aromatic conjugation after that point tem analysis indicates that the carbon layers of shale samples with rmcro exceeds 3 5 show better ordering and continuity than that of low maturity shale samples the ftir analysis suggests that there are relatively high aromatics c c chains and very few aromatic c h chains in the high maturity samples this critical chemical structure jump at rmcro 3 5 could be interpreted as the structure of organic matter begins to transform from amorphous carbon to crystalline graphite in shales due to the increasing degree of graphitization graphitized shale is characterized by stable chemical structure condensed and orderly carbon layer constructure and ultra low resistivity

thermal maturity of the barnett shale determined from well log analysis intensive development with large scale fracturing treatments has made the barnett shale play newark east field in the fort worth basin the largest shale gas field in the world the mississippian barnett shale is an organic rich self sourced reservoir rock thermal maturity thickness and total organic carbon are the most important geological factors for commercial gas production from this shale formation the log derived thermal maturity index mi has been developed in an effort to better understand and predict hydrocarbon phases across the basin maturity index was calculated using three types of open hole logs neutron porosity deep resistivity and density porosity or bulk density the derivation of mi is based on the hypotheses that shale gas is generated and stored locally without apparent migration from outside sources and that the water saturation and the density of generated hydrocarbons decrease with an increase in thermal maturity maturity index correlates well with initial gas oil ratios gor from well production data based on this correlation an empirical relationship has been demonstrated for the fort worth basin this method is useful in understanding the thermal maturity levels of barnett shale source rock in the gas generation window mapping mi gor and gas heating value from hundreds of wells identifies the various maturity stages and areas of barnett shale that generate oil condensate wet gas or dry gas in the fort worth basin

experimental investigations on the geometry and connectivity of pore space in organic rich wufeng and longmaxi shales abstract the nano scale pore systems of organic rich shale reservoirs were investigated from upper ordovician wufeng and lower silurian longmaxi formations in southeast sichuan basin these two formations are the most important target plays of shale gas development in china the purpose of this article is to assess the geometry and connectivity of multi scale pore systems and to reveal the nature and complexity of pore structure for these over mature gas shales to achieve these objective total organic carbon mineralogy image analyses by focused ion beam sem low pressure nitrogen adsorption mercury injection capillary pressure micp and spontaneous fluid deionized di water and n decane imbibition were performed most of the visible pores from sem work in wufeng and longmaxi shales are within nm and m size regimes and belong to organic matter om pores the shapes of om pore in longmaxi samples are elliptical bubble like irregular or rounded wufeng pores are mainly irregular linear and faveolated even though two shales have small depth difference as well as similar thermal maturity kerogen type and toc content nano scale pores in longmaxi are mainly associated with narrow platelike or slitlike pores with pore size of 3 50 nm while inkbottle pores are dominant in wufeng samples and over 88 of the pore volume is contributed by pores with diameter

graphitization of organic matter and fluid deposited graphite in palaeoproterozoic birimian black shales of the kaya goren greenstone belt burkina faso west africa palaeoproterozoic black shales form an essential part of the birimian volcanosedimentary belt in burkina faso west africa the mean rmax values and the atomic h c values of the bulk carbonaceous matter bcm together with rock structures and mineral assemblages indicate that these carbon rich rocks were metamorphosed to sub greenschist and low grade greenschist facies x ray diffraction reveals that the 002 graphite peak width in half maximum fwhm ranges from 0 43 to 0 71 2 in sub greenschist facies and from 0 27 to 0 41 2 in greenschist facies rocks but the d 002 values in both groups of rocks are approximately the same 3 35 a the bcm of individual samples is composed of particles with very variable shape reflectance and raman spectra type i particles that predominate in sub greenschist facies are fine grained irregular or elongate bodies 1 to 3 m in size their maximum reflectance rmax ranges between 2 5 and 8 2 and raman parameters r1 and r2 range from 0 5 to 1 4 and 0 5 to 0 8 respectively type ii particles are lath shaped up to 40 m large bodies commonly arranged parallel to white mica flakes the number of these particles increases from sub greenschist to greenschist facies maximum reflectance varies between 6 and 11 2 and r1 and r2 raman parameters range from 0 05 to 0 7 and from 0 1 to 0 5 respectively type iii particles occur in hydrothermally altered and sheared rocks these are nodular aggregates composed of grains up to 10 m in size this type of particles has very high reflectance rmax 11 15 and its raman spectra indicate a very high degree of structural ordering corresponding to well ordered graphite type i particles represent original organic matter in the metasediments type ii particles are believed to have been formed either in situ by solid state transformation of type i particles or by crystallization from metamorphic fluids gradual graphitization of the type i organic particles and the growth of lath shaped type ii particles from a fluid phase is assumed to have taken place under the peak metamorphic conditions associated with the burial of birimian sediments during thrust tectonism progressive tectonic accretion and crustal thickening during the d1 event of the eburnean orogeny the growth of equant high reflectance postkinematic nodular aggregates of type iii particles is ascribed to the reduction of co2 rich fluids during a hydrothermal event associated with late eburnean d2 exhumation and strike slip movements type i carbonaceous particles were only slightly affected by high temperature low pressure contact metamorphism during intrusion of late eburnean magmatic bodies whereas formation of type ii or iii particles was not recorded in contact metamorphosed rocks at all

water in skeletal carbonates abstract studies of a wide variety of modern and fossil skeletal carbonates indicate they all contain water in amounts ranging from a few tenths of one percent to as much as three percent by weight the word water is used as a general term to include all inorganic liquid and bound h2o and oh reflectance spectroscopy in the visible and near infrared 0 60 to 2 55 m reveals major differences among skeletal carbonates in the amount of water present phases in which it occurs and relative proportions of these phases liquid h2o is present in all skeletal material studied in the form of fluid inclusions in some cases most notably the molluscs h2o is also associated with an organic matrix a hydrated caco3 phase occurs in so e biogenic low mg calcites lmcs and aragonites and two hydrated mgco3 phases with differing bond energies occur in high mg calcites hmcs many hmcs contain mg oh 2 and h2o bound to caco3 as well and some biogenic aragonites contain ca oh 2 water content varies with skeletal mineralogy taxonomic group and in the case of the molluscs with skeletal structure alteration of aragonites and hmcs to lmcs is accompanied by order of magnitude changes in total water content hmcs lose bound h2o and oh during alteration to lmcs ca oh 2 and h2o bound to caco3may also be lost from biogenic aragonites even in the absence of changes in bulk mineralogy lmcs also lose h2o bound to caco3 during diagenesis fluid inclusions are lost during neomorphic alteration of aragonites and lmcs however skeletal material that retains its original bulk skeletal mineralogy and or original microstructure as seen in thin section also retains the bulk of its original fluid inclusion content water content can be used as a criterion for monitoring diagenetic alteration in carbonates water present in fluid inclusions can serve as a medium for diagenetic reactions bound h2o lost on heating could take part in diagenetic reactions during deep burial as well

pore structure wettability and tracer migration in four leading shale formations in the middle yangtze platform china abstract deposited in different sedimentary settings four leading shale formations late ordovician wufeng early silurian longmaxi late permian dalong and early jurassic dongyuemiao shales are currently the most promising zones for shale gas development in the middle yangtze platform of south china based on complementary tests low pressure gas physisorption mercury injection capillary pressure micp contact angle measurement fluid imbibition into initially dry shale and tracer diffusion into initially fluid saturated shale followed by tracer mapping with laser ablation inductively coupled plasma mass spectrometry la icp ms this work investigates their pore structure both geometry and connectivity and wettability characteristics as well as the coupled effects of these characteristics on fluid flow and tracer migration pores

organic matter hosted pore system in the wufeng longmaxi o3w s11 shale jiaoshiba area eastern sichuan basin china abstract the first commercial shale gas with the capability to produce 203 000 cubic meters per day were discovered in the wufeng longmaxi o 3 w s 1 l shale namely the upper ordovician wufeng shale o 3 w and the lower silurian longmaxi shale s 1 l of well jy1 jiaoshiba area eastern sichuan basin china in this study fe sem co 2 and n 2 sorption and micp were used to characterize the pore morphology type size and specific surface area of the wufeng longmaxi shale we focused our research on well jy1 to establish a standard well cross section to allow comparison with well studied gas shales such as barnett marcellus kimmeridge clay and others fe sem visible mineral pore sizes range from 4 nm to 3416 nm with an average of 118 nm within the wufeng longmaxi shale om hosted pore sizes vary from 5 nm to 1021 nm with an average of 68 nm within the wufeng longmaxi shale micropore volumes vary from 0 0048 cm 3 g to 0 0078 cm 3 g with an average of 0 0059 cm 3 g mesopore volumes range from 0 0108 cm 3 g to 0 0166 cm 3 g with an average of 0 0139 cm 3 g macropore volumes range from 0 00005 cm 3 g to 0 00274 cm 3 g with an average of 0 00108 cm 3 g and surface areas range from 22 05 m 2 g to 36 37 m 2 g with an average of 27 68 m 2 g the average pore diameters of wufeng longmaxi shales range from 5 31 nm to 7 40 nm toc has a significant effect on bulk shale porosity porosity measured by fe sem ranges from 0 46 to 1 54 but covers only a small fraction of the shale total porosity as the fe sem detection limit is in a m range the majority of shale pore space pores 2 and n 2 adsorption and have an obvious relationship with the toc therefore the wufeng longmaxi shale has a predominantly organic matter pore system

thermal maturity evaluation from inertinites by raman spectroscopy the ramm technique abstract a new thermal maturity evaluation tool ramm raman maturity method enables determination of equivalent vitrinite reflectance from raman spectra of inertinite except for the avoidance of liptinites the method does not require identification of maceral type measured assemblages ranging from all inertinite to all vitrinite are suitable the method uses five parameters derived from the first order vibrational spectrum of carbon data from about a dozen humic grains are averaged although a reasonable estimate of thermal maturity can be obtained from a single inertinite grain ramm yields equivalent vitrinite reflectance ramm eqvr values based on a multilinear regression equation derived from data on 163 macerals from ten reference coals having vitrinite reflectances ranging from 0 4 to 1 2 cross calibration on the reference coals and application to a suite of 14 other coals spanning this rank range agree well with measured vr values limited data on isometamorphic coals suggest that ramm eqvr can solve the problems caused by vitrinites with high h c atomic ratios and consequent suppressed vitrinite reflectance this is accomplished by deriving normal reflectance values in a similar way as inertinites with low h c are referred back to their equivalent vitrinite reflectance values the ramm method is affected by post sampling maceral oxidation but to what degree is uncertain at present the methodology and calibration have been established and future work will demonstrate applications to dispersed organic matter in samples from petroleum exploration wells especially where vitrinite is absent or rare

facies patterns and geography of the yangtze region south china through the ordovician and silurian transition abstract lithofacies and biofacies changes through the ordovician and silurian transition on the yangtze platform are coincident with stepwise mass extinctions recovery events global sea level changes and regional palaeogeographic configurations facies patterns through three intervals the late mid ashgill hirnantian and early rhuddanian indicate that black shale occupied most of the yangtze platform region during the late mid ashgill and early rhuddanian while the hirnantian possesses more diverse facies types the black shale was replaced by carbonate facies during the hirnantian coincident with a global sea level low stand biofacies changes from the late mid ashgill graptolitic to the hirnantian shelly facies were apparently signalled by gradual and diachronous existence of a mixed facies the manosia facies in the yangtze region however the biofacies change was abrupt from the hirnantian to the early rhuddanian when graptolitic facies occupied most areas on the yangtze platform leaving only a very narrow limited belt of shelly facies along the southern margin of the platform in northern guizhou the early rhuddanian unified biofacies pattern is a result of a global sea level rise which may be synchronized with a recovery bioevent of graptolites after hirnantian mass extinction

raman spectrum of carbonaceous material a possible metamorphic grade indicator for low grade metamorphic rocks raman spectral analyses of carbonaceous material cm extracted from pelitic samples along two sections traversing the metamorphic belt of taiwan were carried out in the present study the results show similar spectral variations of cm with metamorphic grade as those documented in the literature however continuous sampling from zeolite facies through prehnite pumpellyite facies to greenschist facies metamorphic rocks in the present study does reveal some interesting features on the raman spectra of cm that were not noted before both the raman d disordered o ordered peak area i e integrated intensity ratio and the d o peak width i e full width at half maximum fwhm ratio of the cm decrease with progressive metamorphism but the most prominent change in the d o peak area ratio occurs in samples of lower greenschist facies metamorphic grade while the most significant decrease in the d o peak width ratio occurs in samples near the boundary of prehnite pumpellyite facies and greenschist facies this phenomenon is interpreted as a result of the decoupling of the changing rates of in plane crystallite size and degree of defects of cm with progressive metamorphism it is postulated that the raman spectrum of cm can serve as a metamorphic grade indicator to distinguish samples of prehnite pumpellyite facies metamorphic grade from those of greenschist facies metamorphic grade

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

confocal laser scanning microscopy and raman imagery of ancient microscopic fossils abstract among all problems confronting the study of ancient permineralized petrified microscopic fossils two stand out the need for 1 accurate documentation of their three dimensional morphology and 2 direct analysis of their chemical composition and that of their surrounding mineral matrices to address these problems we demonstrate the use of two techniques that we have recently introduced to precambrian paleobiology confocal laser scanning microscopy and raman imagery these techniques both of which are non intrusive and non destructive can provide data by which to characterize in situ and at micron scale resolution the cellular and organismal morphology of thin section embedded organic walled fossils in addition raman imagery provides direct analyses of the molecular structural composition of the kerogenous components of such fossils and of their surrounding matrices and a means to assess quantitatively the geochemical maturity of the preserved organics use of these techniques for studies of ancient microscopic fossils can provide information in three dimensions at high spatial resolution about their morphology and cellular anatomy taphonomy and fidelity of preservation composition and mode of preservation and their biogenicity and syngenetic origin with the rocks in which they occur

the effects of shale composition and pore structure on gas adsorption potential in highly mature marine shales lower paleozoic central yangtze china the ordovician wufeng formation and silurian longmaxi formation are two of the most organic rich and gas prospective shale formations in the central yangtze area china in this study we investigate the controls exerted by shale composition and pore structure on methane sorption of these highly matured marine shales ro ranges from 2 0 to 4 0 samples were analyzed by sem pore imaging of ar ion milled samples high pressure methane adsorption and low temperature nitrogen adsorption in the high toc wufeng and lower longmaxi formations numerous organic matter pores are present a positive correlation exists between toc bet surface area and ch4 sorption capacity indicating that porosity associated with organic matter is the key factor controlling methane sorption capacity of shale samples in the organic lean upper longmaxi formation pores within clay particles and carbonate minerals are the major pore types organic lean shale samples from the upper longmaxi formation have higher clay content lo

nanoscale pore characteristics of the lower cambrian niutitang formation shale a case study from well yuke 1 in the southeast of chongqing china the lower cambrian niutitang formation shale is one of the most important shales being studied for unconventional development in china in this work we focused on 21 core samples of niutitang shale from well yuke 1 in the southeast of chongqing to better understand their vertical reservoir characteristics and pore evolution using complementary approaches of x ray diffraction n2 and co2 adsorption petrology microscope and field emission scanning electron microscopy we conducted a series of analyses for pore volume pore size distribution surface area fractal characterization organic geochemistry petrology and mineralogy results indicate that most micropores 50 nm are composed of organic pores and inorganic pores meso macropore volume per unit of total organic carbon toc content dramatically decreases with an increase of maturity and extent of diagenesis meanwhile the toc normalized micropore volume also rapidly declines after maturity ro values were higher than 3 13 the surface fractal dimension d1 for relative n2 pressure p p0 0 5 with capillary condensation and surface fractal dimension d2 for p p0 0 5 with mono and multi layer adsorption derived from n2 sorption isotherms can be used to indicate the pore characteristics d1 is controlled by the percentages of micropore volume d2 seems to be affected by the clay mineral contents and thermal maturity

geochemistry characteristics and significance of two petroleum systems near top overpressured surface in central junggar basin nw china abstract most hydrocarbons discovered in the central junggar basin are endowed in limited areas below and above top overpressured surface by studying geochemical and distribution characteristics of hydrocarbons in reservoirs near top overpressured surface it was found that the lacustrine dark mudstone in middle lower permian and coal measures in jurassic are the major source rocks crude oils from these two sets of source rocks have apparently different geochemical indexes their maturity values are 0 7 1 0 higher in permian the natural gas is mainly coal derived wet gas from jurassic formation with general maturity of 0 9 1 0 hydrocarbons in tectonic units have different distribution features depending on sources crude oil above top overpressured surface in western well pen 1 sag is from both middle and lower permian while crude oil in overpressure compartment is mainly from middle permian and natural gas is from hybrid sources crude oil near top overpressured surface in western changji sag is mainly from middle permian including some oil from hybrid sources the natural gas is mainly coal derived wet gas hydrocarbons in northern dongdaohaizi sag and eastern changji sag are mainly coal derived oil and gas in overpressure compartment hydrocarbons in the central junggar basin underwent two stages of accumulation and experienced two large scale chargings at the later stage to summarize geochemical and distribution characteristics of hydrocarbons in reservoirs near top overpressured surface in the central junggar basin can provide reference for understanding hydrocarbon accumulation regularity and predicting favorable exploration targets near top overpressured surface in this region and similar high overpressure and hydrocarbon generation basins

porosity characteristics of the devonian horn river shale canada insights from lithofacies classification and shale composition abstract this study evaluates pore systems of the horn river shale in western canada sedimentary basin from lithofacies classification of core samples to micro scale pore structure investigation samples from the middle and upper devonian horn river shale sequence were examined by core description porosity measurement sem and tem imaging of ion milled samples and nitrogen adsorption analysis in order to develop a better understanding of the controls of organic and inorganic rock constituents on porosity development and pore microstructure five primary shale lithofacies were identified by hand core and thin section analyses massive mudstones massive mudstones with pyrite streaks laminated mudstones bioturbated mudstones and carbonates porosity ranges from 0 62 to 12 04 and shows wide variation between different lithofacies massive mudstones and pyritic mudstones with high total organic carbon toc content have the highest porosity whereas bioturbated mudstones and carbonates with low toc content have the lowest porosity sem and tem images suggest that several kinds of sites for porosity development are present including organic matter pyrite framboids clay platelets quartz rims carbonate grains and microfractures a general positive relationship between toc and porosity indicates that a large proportion of pores are developed in organic matter results from the nitrogen adsorption analysis suggest that samples with more organic matter tend to develop smaller pores thus while porosity development is a combined function of organic matter mineral components fabric and fractures it is most affected by organic matter concentration the muskwa formation and the evie member have more gas storage capacity as they primarily consist of massive mudstones and pyrite rich mudstones showing the best porosity the otter park member has lower porosity which may relate to the fact that its lithofacies mainly consists of laminated mudstones and bioturbated mudstones

bib sem study of the pore space morphology in early mature posidonia shale from the hils area germany abstract this contribution reports on the study of the pore space morphology in two early mature vr r 0 59 and 0 61 samples of posidonia shale from the hils syncline in germany using broad ion beam bib polishing and high resolution scanning electron microscopy sem this allows imaging pores with resolution down to 10 nm in equivalent diameter d eq and quantitative estimation of porosity using a combination of bse and se detectors and semi automatic segmentation of the gigapixel images the representative elementary area of the samples on the scale of a few mm is inferred to be about 140 140 m 2 pore morphologies and pore sizes are clearly related to the mineral fabric with large differences very large typically several microns pores with internal faceted crystal morphology in recrystallized calcite clasts and smaller pores d eq cf schizosphaerella nanofossils typically 200 nm pores are less common in organic material and in pyrite aggregates pore characteristics are very similar for both samples and porosity resolvable by bib sem is 2 75 and 2 74 pore size distribution can be described by a power law with an exponent about 2 0 and 2 2 respectively for the pore population excluding the fossils pores in the carbonate fossils show dual power law distribution with power law exponents of about 1 and 3 by extrapolating the power law distribution for each sample total porosity is estimated to be 4 8 0 9 1 7 and 6 5 2 7 7 2 respectively this estimate can be compared with 3 4 3 7 and 3 3 3 6 as measured by mercury injection porosimetry we interpret this difference to reflect the unconnected for mercury part of the porosity comparison of imaged pores and mercury injection porosimetry suggest a very high pore body to pore throat ratio this results in a pore model where large pores represented mainly by pores in fossils and calcite grains are connected via a low porous and low permeable clay rich matrix with pore throats below 10 nm in both samples

microstructural investigation of gas shales in two and three dimensions using nanometer scale resolution imaging the microstructure of gas shale samples from nine different formations has been investigated using a combination of focused ion beam fib milling and scanning electron microscopy sem backscattered electron bse images of fib cross sectioned shale surfaces show a complex microstructure with variations observed among the formations energy dispersive spectroscopy of the shale cross sections indicates that clay carbonate quartz pyrite and kerogen are the most prevalent components in the bse images areas of kerogen are observed interspersed with the inorganic grains pores are observed in both the kerogen and inorganic matrix with the size shape and number of pores varying among the shale samples by using fib milling and sem imaging sequentially and repetitively three dimensional 3 d data sets of sem images have been generated for each of the shale samples three dimensional volumes of the shales are reconstructed from these images by setting thresholds on the gray scale the kerogen and pore networks are segmented out and visualized in the reconstructed shale volumes estimates of kerogen and pore volume percentages of the reconstructed shale volumes have been made and range from 0 to 90 0 for the kerogen and 0 2 to 2 3 for pores estimates of pore size distributions suggest that although pores with radii of approximately 3 nm dominate in number they do not necessarily dominate in total volumetric contribution scanning electron microscopy images and 3 d reconstructions reinforce the facts that shales are quite different and that their microstructures are highly variable and complex