reflectance of dispersed vitrinite in palaeozoic rocks with and without cleavage implications for burial and thermal history modeling in the devonian of rursee area northern rhenish massif germany abstract vitrinite reflectance is used as coalification parameter in coals and as maturity and palaeotemperature indicator in sedimentary rocks in high grade diagenetic rocks i e rocks at the boundary between diagenesis and metamorphism vitrinites become increasingly anisotropic therefore it has been suggested to study maximum minimum reflectance instead of mean reflectance for rocks which reached this stage in the present study vitrinite reflectance data from a folded sequence of the northern rhenish massif germany are combined with microtectonic study of thin sections in samples in which both bedding and cleavage are present we show that vitrinites in different microtectonic domains cleavage domains and microlithons show significant differences in both maximum vitrinite reflectance and vitrinite reflectance anisotropy this behaviour is due to a strong partitioning of deformation in cleavage domains as compared to microlithons so that vitrinite reflectance is controlled by the thermal and deformation history accordingly estimation of maximum palaeotemperatures during burial should be based on vitrinite reflectance measurements in microlithons unaffected by deformation after maximum burial based on this finding burial and temperature history of the rursee area in the eastern rhenish massif is reconstructed numerical simulations indicate a maximum burial at the siegen ems boundary of about 5000 m and a maximum burial temperature of about 220 c

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

high thermal maturity in the lower saxony basin intrusion or deep burial abstract the lower saxony basin lsb is situated at the southern rim of the northern permian basin the most important hydrocarbon bearing province in europe in its southern part areas of high thermal maturation up to 6 rr occur which were previously explained as being caused by magmatic intrusions of turonian to santonian age that affected carboniferous to lower cretaceous rocks in this area 2d numerical basin modelling was carried out in order to reconstruct the temperature histories along two parallel n s trending seismic sections along these sections new data about maturity distribution and temperature history were obtained by vitrinite reflectance measurements and apatite fission track analysis for the areas with highest maturity values low coalification gradients were established which agree well with earlier published data on wells further towards the west this new information does not support previous hypotheses on high heat flows from magmatic intrusions even if lateral heat transport is taken into account instead comparisons with a recently published map of the subsurface structure of the lsb indicate that maturity distribution may be closely related to major tectonic structures deep burial of individual structures of the lsb which are bordered by deep e w to ese wnw trending faults is further suggested by a rapidly increasing thicknesses of preserved cretaceous strata towards the south and b structural restoration of one of the seismic sections to achieve a fit between measured and calculated palaeo temperature and vitrinite reflectance data deep burial of carboniferous source rocks during cretaceous time has to be assumed due to an inversion phase in the early and middle upper cretaceous major amounts of sediment were removed and further uplift occurred in tertiary times in contrast the northern part of the lsb experienced maximum burial and temperatures during tertiary times

nannofacies analysis as a tool to reconstruct paleoenvironmental changes during the early toarcian anoxic event the black shales of lower toarcian schistes carton in france jet rock in england posidonia shale in germany are sediments formed by fine alternations of millimetric to sub millimetric clear and dark laminae a study of polished core surfaces dotternhausen core sw germany was carried out in sem in order to characterize the micro fabrics of different laminae and their content in nannofossils two main intervals were recognized where fabrics and nannofossil content are significantly different in the clay rich interval characterized by high wt toc and a large negative carbon isotope excursion both in carbonates and organic matter the dominant micro fabrics are well foliated or lumpy giving evidence of the absence or reduction of benthic life nannofossils are scarce and only concentrated in discrete laminae separated by large abiotic intervals assemblages are indicative of a deep nutricline but sporadic nutrient inputs occurred as demonstrated by fluctuation in abundance of specimens of the biscutaceae nutrients were probably delivered to the german basin via riverine influx different sized framboids of pyrite were recognized in this interval the smallest ones 2 m being probably precipitated in an anoxic and sulphidic water column the clay rich interval was likely deposited during low sea level in a restricted basin these conditions were followed by a sea level rise and better water mass circulation within the german basin sedimentation records an increase in carbonate deposition organic matter content decreased and carbon isotopes came back to pre excursion values micro fabrics became less markedly laminated pyrite framboids nearly disappeared and rich and diversified nannofossil assemblages are recorded sea water conditions were probably highly fluctuating as indicated by alternation of intervals dominated in turn by schizosphaerella spp flourishing under generally oligotrophic conditions where nutrients were temporarily available in surface waters due to storms and by crepidolithus spp a deep dweller the results of this work fit well with a silled basin model

the importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs abstract the effect of shale composition and fabric upon pore structure and ch 4 sorption is investigated for potential shale gas reservoirs in the western canadian sedimentary basin wcsb devonian mississippian d m and jurassic shales have complex heterogeneous pore volume distributions as identified by low pressure co 2 and n 2 sorption and high pressure hg porosimetry thermally mature d m shales 1 6 2 5 vro have dubinin radushkevich d r co 2 micropore volumes ranging between 0 3 and 1 2 cc 100 g and n 2 bet surface areas of 5 31 m 2 g jurassic shales which are invariably of lower thermal maturity ranging from 0 9 to 1 3 vro than d m shales have smaller d r co 2 micropore volumes and n 2 bet surface areas typically in the range of 0 23 0 63 cc 100 g co 2 and 1 9 m 2 g n 2 high pressure ch 4 isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon toc content methane sorption in d m shales increases with increasing toc and micropore volume indicating that microporosity associated with the organic fraction is a primary control upon ch 4 sorption sorption capacities for jurassic shales however can be in part unrelated to micropore volume the large sorbed gas capacities of organic rich jurassic shales independent of surface area imply a portion of ch 4 is stored by solution in matrix bituminite solute ch 4 is not an important contributor to gas storage in d m shales structural transformation of d m organic matter has occurred during thermal diagenesis creating and or opening up microporosity onto which gas can sorb as such d m shales sorb more ch 4 per weight percent wt toc than jurassic shales inorganic material influences modal pore size total porosity and sorption characteristics of shales clay minerals are capable of sorbing gas to their internal structure the amount of which is dependent on clay type illite and montmorillonite have co 2 micropore volumes of 0 78 and 0 79 cc 100 g n 2 bet surface areas of 25 and 30 m 2 g and sorb 2 9 and 2 1 cc g of ch 4 respectively dry basis a reflection of microporosity between irregular surfaces of clay platelets and possibly related to the size of the clay crystals themselves mercury porosimetry analyses show that total porosities are larger in clay rich shales compared to silica rich shales due to open porosity associated with the aluminosilicate fraction clay rich sediments low si al ratios have unimodal pore size distributions

hydrocarbon bearing fluid inclusions in calcite filled horizontal fractures from mature posidonia shale hils syncline nw germany abstract hydrocarbon bearing fluid inclusions in calcite filled horizontal fractures from mature posidonia shale 0 88 r o were investigated by microscopic microthermometric and chemical methods the fluid inclusions predominantly contain both a liquid hydrocarbon phase which shows bright uv fluorescence colours yellow brownish light blue and a non fluorescent hydrocarbon gas phase the different uv fluorescence colours probably reflect the different gross chemical compositions of the trapped liquid hydrocarbons the saturated hydrocarbon fraction of the fluid inclusions mostly secondary inclusions predominantly consists of low molecular weight n alkanes c 9 c 12 while c 12 c 22 n alkanes are more abundant in the adjacent rock matrix the molecular composition of the fluid inclusions appears to reflect a mobile hydrocarbon phase which was entrapped within the calcitic fill of the horizontal fractures pressure corrected trapping temperatures were estimated for primary fluid inclusions 123 162 c this temperature range is in agreement with the results from numerical simulation studies which indicate a maximum temperature of 148 c coinciding with the period of fracture formation calcite filling and entrapment of primary fluid inclusions

distribution of brine in grain boundaries during static recrystallization in wet synthetic halite insight from broad ion beam sectioning and sem observation at cryogenic temperature we report observations from room temperature static recrystallization experiments annealing times from minutes to year of cold pressed synthetic coarse grained wet sodium chloride prepared by broad ion beam polishing and sem observations at cryogenic temperature to observe directly the brine in grain boundaries at all stages of annealing the majority of the brine in the samples is connected in 2d sections along grain boundaries another part of the brine is in isolated brine inclusion arrays along grain boundaries and in brine inclusions left behind by migrating brine filled grain boundaries most of these boundaries are mobile because the aggregate is coarsening we interpret that the boundaries without observable brine films 15 nm and brine inclusion arrays are healed and immobile evolution of grain boundary structure involves three major processes first dissolution on one side of the grain boundary and precipitation on the other side result ing in grain boundary migration second the development of facets formed by low index crystallographic planes of the grains bounding the grain boundary brine when both sides of a grain boundary are able to develop low index facets in a thick brine film the resulting impingement boundary is interpreted to be immobile and may prevent the new grain from migrating into a deformed neighbor when one side of a faceted boundary consists of low index crystallographic planes and the other side passively follows this faceted shape along irrational surfaces the boundary is mobile third the healing of grain boundary brine films producing solid solid grain boundaries without resolvable brine films

petroleum source rocks of the tarfaya basin and adjacent areas morocco abstract this work characterizes the source rock potential of the tarfaya basin and enabled us to reconstruct its geochemical history outcrop samples covering different stratigraphic intervals plus the northwestern part of the zag tindouf basin bas draa area were analyzed for total organic carbon corg and total inorganic carbon contents and total sulfur content rock eval analysis and vitrinite reflectance measurements were performed on 56 samples chosen on the basis corg content a set of 45 samples were extracted and non aromatic hydrocarbons were analyzed by way of gas chromatography flame ionization detection gc fid and gc mass spectrometry gc ms non isothermal open system pyrolysis at different heating rates was applied to obtain kinetic parameters for modelling petroleum generation from four different source rocks high quality petroleum source rocks with high corg content and hydrogen index hi values were found for samples of eocene coniacian turonian and cenomanian age most samples were carbonate rich and organic sulfur values were high to moderate various maturity parameters indicated immature or possibly early mature organic matter based on organic geochemical and petrological data the organic matter is of marine aquatic origin cenomanian or a mixture of aquatic and terrigenous material eocene the early cretaceous interval did not contain high quality source rocks but indications of petroleum impregnation were found

source rock evaluation by well log analysis lower toarcian hils syncline abstract the feasibility of conducting petroleum source rock evaluations from well log data was examined using three continuously cored sections immature mature and postmature stages of the lower toarcian posidonia shale northern germany logs depicting natural gamma emission k u th bulk density sonic travel time and resistivity were utilised as was the borehole televiewer for fracture control selected data from these logs were correlated with parameters of source richness hydrocarbon content and maturity the resulting three dimensional cross plot shows at a glance well by well comparison of facies maturity and hydrocarbon content a simple correlation between organic geochemical and petrophysical parameters is of course not perfect since log response is complex and affected by mineralogical and pore fluid properties of the rock as well as by organics however source rock characterization by wireline logging is still a fast and therefore economical method relative quick look comparisons from well to well are possible without calibration to core data and can easily be performed at once at the drill site the present application is limited to clastic source rocks in basins with simple geologic histories

nanoscale porosity in safod core samples san andreas fault article i nfo with transmission electron microscopy tem we observed nanometer sized pores in four ultracataclastic and fractured core samples recovered from different depths of the main bore hole of the san andreas fault observatory at depth safod cutting of foils with a focused ion beam technique fib allowed identifying porosity down to the nm scale between 40 and 50 of all pores could be identified as in situ pores without any damage related to sample preparation the total porosity estimated from tem micrographs 1 5 is comparable to the connected fault rock porosity 2 8 6 7 estimated by pressure induced injection of mercury permeability estimates for cataclastic fault rocks are 10 21 10 19 m 2 and 10 17 m 2 for the fractured fault rock porosity and permeability are independent of sample depth tem images reveal that the porosity is intimately linked to fault rock composition and associated with deformation the tem estimated porosity of the samples increases with increasing clay content the highest porosity was estimated in the vicinity of an active fault trace the largest pores with an equivalent radiusn 200 nm occur around large quartz and feldspar grains or grain fragments while the smallest pores equivalent radiusb 50 nm are typically observed in the extremely fine grained matrix grain sizeb 1 m based on pore morphology we distinguish different pore types varying with fault rock fabric and alteration the pores were probably filled with formation water and or hydrothermal fluids at elevated pore fluid pressure preventing pore collapse the pore geometry derived from tem observations and bet brunauer emmett and teller gas adsorption desorption hysteresis curves indicates pore blocking effects in the fine grained matrix observations of isolated pores in tem micrographs and high pore body to pore throat ratios inferred from mercury injection suggest elevated pore fluid pressure in the low permeability cataclasites reducing shear strength of the fault 2010 elsevier b v all rights reserved

organic matter maturation under the influence of a deep intrusive heat source a natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock toarcian shale northern germany four shallow boreholes were drilled in the hils syncline northern germany in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen type ii bearing source rock the holes penetrated the carbonceous lias shales posidonia shale lower toarcian and part of the adjacent dogger and lias mudstones the maturity of the organic matter in the cores recovered ranges from immature 0 48 r0 to overmature 1 45 r0 due to location of the hils syncline in the vicinity of the vlotho massif which is deep seated intrusive body facies variations of the lias within the short geographical distances in the study area are negligible organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the lias shales kerogen bitumen etc and on the evidence of a uniform initial composition of these sediments in the study area dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations about 50 of the initial kerogen was transformed into oil gas and inorganic compounds during the vitrinite reflectance increase from 0 48 to 0 88 ro and only marginally more during the maturity increase from 0 88 to 1 45 ro only a small portion of the generated material remained in the source rock even at a relatively early stage of generation 0 68 ro expulsion efficiency of oil plus gas reached a value of 86 at the end of the main generation stage 0 88 ro

quantification of loss of calcite pyrite and organic matter due to weathering of toarcian black shales and effects on kerogen and bitumen characteristics abstract comparison of geochemical data on posidonia shale early toarcian from a shallow unweathered core and from adjacent weathered exposures of the same fades was performed results revealed that quantitatively the most affected petrographic constituent is pyrite and that organic matter and carbonate were also altered by weathering due to this process of weathering the bulk composition of organic matter especially the molecular composition of soluble organic matter and the fluorescence colour of organic particles are changed estimates of weathering rates reveal that the annual release of sulphur and organic carbon from black shales may significantly add to anthropogenic pollution

insights into pore scale controls on mudstone permeability through resedimentation experiments at a given porosity mudstone permeability increases by an order of magnitude for clay contents ranging from 57 to 36 2 m this increase in vertical permeability results from a dual porosity system that develops through three mechanisms 1 silt bridging preserves large pore throats 2 stress bridges inhibit clay particle alignment and 3 local clay particle compression within stress bridges alters pore throat size distribution uniaxial consolidation experiments on resedimented clay silt mixtures illuminate how permeability varies as a function of clay fraction during burial backscattered electron microscope images show that silty mixtures have larger pore throats and fewer aligned clay particles than do more clay rich mixtures we describe the permeability of clay silt mixtures with a geometric mean model our method provides a promising framework for modeling of mudstone permeability as a function of clay fraction and porosity how permeability and consolidation evolve during burial affects the ability of mudstones to seal co2 and hydrocarbons in the subsurface how mudstones behave as gas reservoirs and under what conditions mudstones will be overpressured dual porosity systems have fundamentally different transient flow and solute transport behaviors

geochemical evolution of organic rich shales with increasing maturity a stxm and tem study of the posidonia shale lower toarcian northern germany hydrocarbon generation and retention processes occurring within gas shales as a response to increases in thermal maturation are still poorly constrained while efforts have been directed at unravelling the resource potential composition and textures of these economically important unconventional systems their spatial variability in chemistry and structure is still poorly documented at the sub micrometer scale here we have characterized samples of the lower toarcian posidonia shale samples from northern germany at varying stages of thermal maturation using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm we document geochemical and mineralogical heterogeneities down to the nanometer scale within the investigated samples as a function of their level of thermal maturity in particular authigenic albite crystals containing nanometric halite inclusions have been documented within the investigated mature and overmature samples the presence of such tracers of palaeobrine carbonate interactions supports a maturation scenario for the lower toarcian posidonia shale intimately related to ascending brine fluids rather than a maturation scenario solely resulting from high heat flows in addition various types of asphaltene and nso rich bitumen have been detected within the same samples very likely genetically derived from thermally degraded organic precursors furthermore the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by providing in situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen the results reported here constitute an important step towards better constraining hydrocarbon generation processes during natural shale gas maturation

permeability porosity transforms from small sandstone fragments numerical simulation of laboratory experiments on rocks or digital rock physics is an emerging field that may eventually benefit the petroleum industry for numerical experimentation to find its way into the mainstream it must be practical and easily repeatable i e implemented on standard hardware and in real time this condition reduces the size of a digital sample to just a few grains across also small physical fragments of rock such as cuttings may be the only material available to produce digital images will the results be meaningful for a larger rock volume to address this question we use a number of natural and artificial medium to high porosity well sorted sandstones the 3d microtomography volumes are obtained from each physical sample then analogous to making thin sections of drill cuttings we select a large number of small 2d slices from a 3d scan as a result a single physical sample produces hundreds of 2d virtual drill cuttings images corresponding 3d pore space realizati

simulating nonsorted circle development in arctic tundra ecosystems 1 nonsorted circles ubiquitous to the arctic tundra region are patterned ground features with circular semibarren areas surrounded by vegetation these circles are formed and persist as an ecosystem due to complex soil water energy ice plant relationships and dynamics in the arctic in this paper we present the first model that captures the dynamics of the physical and biological components of the nonsorted circle ecosystem in order to understand its formation and persistence especially in a changing climatic environment we have applied a coupled model describing 1 vegetation dynamics arcveg and 2 coupled heat and moisture transport with phase change wit in the active layer of the soil where such circles are initiated and developed we simulated the system behavior during the formation process starting with a random vegetation development the vegetation provided heterogeneous insulation to the soil surface during freezing the noninsulated areas froze first resulting in preferential ice accumulation in those areas the ice prevented the vegetation from developing further in those areas and thus developed and stabilized the nonsorted circle pattern the model produced a nonsorted circle pattern that was well compared to those observed in the field the model also illustrated that the availability of water was critical for the sustenance and stability of the nonsorted circle the effect of climatic variations on the freezing process on the other hand did not seem to affect the formation and sustenance of nonsorted circles

microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in toarcian source rocks of different maturities abstract this study is part of a comprehensive research program on the generation and migration of petroleum from the organic rich posidonia shale lower toarcian jurassic of the hils syncline northern germany four cores of the complete posidonia shale with varying amounts of underlying pliensbachian and overlying aalenian mudstones provided the sample base depending upon their distance from a presumed subjacent heat source the vlotho massif the cores display progressive levels of increasing thermal maturation with r 0 values 0 48 0 68 0 88 and 1 45 which span the limits of the oil generation window primary stratigraphic lithologic and petrographic attributes of the four sections are all very similar each includes a lower marlstone member about 5 m thick overlain by 11 31 m of calcareous clay shale clay minerals calcite pyrite kerogen and quartz are the principal constituents thus there is no evidence that depositional conditions of the posidonia shale varied significantly over the sampled area the omnipresence of framboidal pyrite clearly formed from the activity of sulphate reducing bacteria at or near the depositional interface is strong evidence that uniform reducing anoxic conditions were persistent at all localities this conclusion supports the assumption that initially each section was identical in overall properties and that significant differences observed in geochemistry organic macerals and other properties are directly related to the variable levels of thermal maturation kerogen from the least mature section r o 0 48 is type ii and composed of alginite a alginite b liptodetrinite bituminite and some terrestrial sporinite vitrinite and inertinite macerals with increasing maturation the alginite macerals exhibit a progressive change in morphology and fluorescence properties alginite of the least mature section displays a strong green fluorescence at 0 68 r o alginite macerals exhibit yellow orange fluorescence and are structurally well preserved although geochemical data indicate generation and loss of large amounts of oil at 0 88 r o hydrocarbon generation is almost complete and few primary alginites remain they have been transformed into secondary liptinites designated as metaalginite which have similar fluorescence colours at the highest maturation level 1 45 r o metaalginites are only weakly fluorescent with a shift toward red colours calcite and or bitumen filled bedding plane micro and macrofractures occur exclusively in the organic rich posidonia shale at maturity levels of 0 68 r o and above such features are totally absent in the immature posidonia section and in the adjacent organic poor mudstones this observation indicates that the fractures developed in direct response to overpressuring i e pore pressure exceeding lithologic load related to oil and gas generation in the source rock the fractures undoubtedly provided important expulsion conduits for generated products

characterization of gas shale pore systems by porosimetry pycnometry surface area and field emission scanning electron microscopy transmission electron microscopy image analyses examples from the barnett woodford haynesville marcellus and doig units the nanometer scaled pore systems of gas shale reservoirs were investigated from the barnett marcellus woodford and haynesville gas shales in the united states and the doig formation of northeastern british columbia canada the purpose of this article is to provide awareness of the nature and variability in pore structures within gas shales and not to provide a representative evaluation on the previously mentioned north american reservoirs to understand the pore system of these rocks the total porosity pore size distribution surface area organic geochemistry mineralogy and image analyses by electron microscopy were performed total porosity from helium pycnometry ranges between 2 5 and 6 6 total organic carbon content ranges between 0 7 and 6 8 wt and vitrinite reflectance measured between 1 45 and 2 37 the gas shales in the united states are clay and quartz rich with the doig formation samples being quartz and carbonate rich and clay poor higher porosity samples have higher values because of a greater abundance of mesopores compared with lower porosity samples with decreasing total porosity micropore volumes relatively increase whereas the sum of mesopores and macropore volumes decrease focused ion beam milling field emission scanning electron microscopy and transmission electron microscopy provide high resolution 5 nm images of pore distribution and geometries image analysis provides a visual appreciation of pore systems in gas shale reservoirs but is not a statistically valid method to evaluate gas shale reservoirs macropores and mesopores are observed as either intergranular porosity or are confined to kerogen rich aggregates and show no preferred orientation or align parallel with the laminae of the shale networks of mesopores are observed to connect with the larger macropores within the kerogen rich aggregates

ichnology of prodeltaic hyperpycnite turbidite channel complexes and lobes from the upper cretaceous prairie canyon member of the mancos shale book cliffs utah usa

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