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

specific surface area and pore size distribution in clays and shales one of the biggest challenges in estimating the elastic transport and storage properties of shales has been a lack of understanding of their complete pore structure the shale matrix is predominantly composed of micropores pores less than 2 nm diameter and mesopores pores with 2 50 nm diameter these small pores in the shale matrix are mainly associated with clay minerals and organic matter and comprehending the controls of these clays and organic matter on the pore size distribution is critical to understand the shale pore network historically mercury intrusion techniques are used for pore size analysis of conventional reservoirs however for unconventional shale reservoirs very high pressures 414 mpa 60 000 psi would be required for mercury to access the full pore structure which has potential pitfalls current instrumental limitations do not allow reliable measurement of significant portions of the total pore volume in shales nitrogen gas adsorption techniques can be used to characterize materials dominated by micro and mesopores 2 50 nm a limitation of this technique is that it fails to measure large pores diameter 200 nm we use a nitrogen gas adsorption technique to study the micro and mesopores in shales and clays and compare the results from conventional mercury porosimetry techniques our results on pure clay minerals and natural shales show that i they have a multiscale pore structure at different dimensions ii fine mesopores with a characteristic 3 nm pore size obtained with n2 gas adsorption are associated with an illite smectite group of clays but not with kaolinite iii compaction results in a decrease of pore volume and a reduction of pore size in the inter aggregate macropores of the illitesmectite clays while the fine intra tachoid mesopores are shielded from compaction iv for natural shales mineralogy controls the pore size distributions for shales and the presence of micropores and fine mesopores in natural shales can be correlated with the dominance of the illite smectite type of clays in the rock our assessment of incompressible 3 nm sized pores associated with illite smectite clays provides an important building block for their mineral modulus

organic matter rich shales of china abstract organic matter rich shales are the main target rocks for unconventional oil and gas exploration and development across the world in china shale gas geological resources are estimated as approximately 110 1012 m3 with recoverable gas reserves of ca 20 1012 m3 recoverable shale oil reserves are estimated as ca 5 109 t a total 35 important organic matter rich shale units have been recognized from mesoproterozoic to cenozoic strata across the entire china these shales are categorized according to their origin under marine marine nonmarine transitional and lacustrine conditions shales of marine origin with ca 9 1012 m3 recoverable resources dominate china s potential in terms of total volume of organic carbon currently the most favorable marine shales for oil and gas exploration are found in the sichuan basin within the lower cambrian qiongzhusi formation and in the wufeng longmaxi formations of uppermost ordovician through lower silurian a fortuitous combination of of sea level variations of paleo productivity of tectonic activity causing development and migration of partially closed deep basin depocenters and of sediment accumulation rates controlled the extensive deposition and distribution of organic matter rich shales in these wufeng and longmaxi formations organic matter rich shales in marine nonmarine transitional facies associated with coal measures occur in north china within the carboniferous and permian and in south china within the permian these carboniferous permian organic matter rich shales are important source rocks for the gas fields in the ordos and sichuan basins abundant organic rich shales are also widely distributed within coal bearing clastics and coal measure shales of fluvial lacustrine and swamp facies in upper triassic to middle jurassic successions of many basins lacustrine organic rich shales were deposited during the permian through neogene in various freshwater to saline lake settings lacustrine organic matter rich shales are the main oil source rocks in the songliao bohai bay ordos and junggar basins lacustrine algae contributed to the rain of organic matter and the preservation of organic matter and distribution of organic rich shale was controlled by lake currents water depth and oxygen poor conditions with enhanced preservation when buried by turbidity currents algal blooms were partly induced by trace nutrients from volcanic ash falls in all of these lacustrine basins seawater intrusion into the freshwater lake of the songliao basin promoted some episodes of black shales saline lacustrine basins such as middle permian junggar basin contain organic rich dolomite mudstone that mainly formed during hot climate conditions when the lakes had high salinity and stratified water columns that deprived the bottom waters of oxygen thereby preserving massive amounts of organic matter laminated calcite rich mudstone in the saline lacustrine settings formed in more brackish waters under stable warm conditions and weak biological activity the modeling of the factors controlling the distribution of organic matter rich shales within china s basins is important for the exploration and development of unconventional oil and gas resources

focused ion beam fib combined with sem and tem advanced analytical tools for studies of chemical composition microstructure and crystal structure in geomaterials on a nanometre scale abstract in order to make meaningful interpretations of trace element and isotopic information from geomaterials prior characterization of the material of interest with respect to structural and chemical homogeneity radiation damage and microstructure is often required transmission electron microscopy tem is a powerful analytical tool that may be used to fully characterise a wide range of synthetic and natural materials the focused ion beam technique fib is an ideal tool for tem sample preparation that allows for the fabrication of electron transparent foils with typical dimensions of 15 10 0 150 m from any region of interest i e site specific and in virtually any material fib sample preparation consumes only a small volume of material approximately 2300 m 3 for a standard foil with the dimensions 15 10 0 150 m leaving most of the material essentially unaffected by the sampling process modern tem facilitates the measurement of chemical composition with unsurpassed spatial resolution e g nanometer scale high resolution imaging and electron diffraction provide important complimentary structural information it is the combination of crystal structure information and chemical composition that allows for the complete characterization of the volume of interest high resolution elemental mapping or line scans may be used to acquire complete energy dispersive x ray analysis edx spectra of a material pixel by pixel subsequent evaluation of the data allows for the correlation of the edx spectrum with the respective elemental map or line scan with an image thus illustrating spatially resolved chemical composition variations at the 0 5 1 0 wt level frequently minerals enclose sub micrometer or even nanometre sized inclusions of minerals fluids or silicate melt which are of great interest to geoscientists nanoinclusions e g in diamond or olivine are of particular interest because they may have preserved their original crystal structure thus providing a geobarometer recording the pressure conditions at the time of formation of the inclusion fib tem are appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the nanometre scale the combination of fib with an sem allows for 3d information to be obtained from samples including 3d imaging e g phase distribution and volume of the individual phases in symplectites 3d distribution of elements in a specific volume 3d elemental maps and three dimensional texture analysis using electron backscatter diffraction ebsd

renyi dimensions of soil pore size distribution abstract the existence of fractal scaling for pore volume size distribution has been empirically shown and several fractal models have been constructed to replicate it deriving also other important physical properties one step forward may be given by using multifractal analysis which achieves a better characterization of a distribution by means of a singularity spectrum whenever suitable scaling properties are present renyi dimensions are a classical tool to characterize complex distributions that are closely related to the multifractal singularity spectrum but having an easier handling and interpretation in this article renyi dimensions of pore size distributions are computed from data obtained by 2 d image analysis of soil samples analyzed samples show suitable scaling properties the renyi dimensions d q appear defined with r 2 greater than 0 95 within a significative range of q s the variation of d q with respect to q and the shape of the renyi spectrum reveal that pore size distributions have properties close to multifractal self similar measures these results show that renyi dimensional analysis is an appropriate tool for characterizing soil pore size distribution and thus may be used as indicator of soil structure as well as for deriving important soil physical properties moreover this characterization opens the possibility of simulating the real distributions by adequate self similar models of fractal geometry as iterated function systems and related ones with the corresponding benefits for prediction purposes

assessment of sediment delivery from successive erosion on stream coupled hillslopes via a time series of topographic surveys in the central high mountain range of taiwan abstract landslides play an important role in the evolution of mountain topography and are a major source of sediment in tectonically active mountain belts for the active orogeny of taiwan erosion rates have been assessed by various methods the discrepancies observed between erosion rates integrated over modern and quaternary time scales may result from various effects related to surface processes more process oriented research on the spatio temporal distribution of hillslope processes and coupling relationships with the fluvial system is needed to reconcile the temporally heterogeneous data in the future this paper assesses and describes the processes of subsequent erosion on hillslopes via a time series of topographic surveys of hillslopes after the initial failure in order to better understand the temporal and spatial variability of landslide erosion sediment fluxes and storage of landslide sediment within channels the results demonstrate that hillslope channel coupling is controlled by the relative frequency of erosive flooding events and the magnitude of rainfall driven hillslope processes the latter is assumed to be disproportionately high on larger failures in periods with less rainfall mass wasting may only affect part of the total failure s area volumes of eroded sediment from gullies on the landslide scar may be as high as the volume estimated for the initial failure the geometry of the sliding masses eroded after the initial failure appears to be uniform and their depths average 6 1 2 2 m

pore structure and fractal characteristics of organic rich shales a case study of the lower silurian longmaxi shales in the sichuan basin sw china abstract shales from the lower silurian longmaxi formation in the sichuan basin are among the most important shale gas reservoirs in china and have been investigated because of their great shale gas potential to understand the pore structure and fractal characteristics of the shales a series of experiments was conducted on core samples from the lower silurian longmaxi formation in the sichuan basin of china including x ray diffraction xrd total organic carbon toc content and vitrinite reflectance ro analysis field emission environmental scanning electron microscope fe esem observation and low pressure n 2 adsorption desorption experiments frenkel halsey hill fhh method was applied to calculate fractal dimensions in addition the pore genesis the relationships between composition and thermal maturity the pore structure parameters and the fractal dimensions are discussed fe esem observation results show that the longmaxi formation shales are dominated by organic matter om pores along with interparticle interp pores intraparticle intrap pores and fracture pores this study identified the fractal dimensions at relative pressures of 0 0 45 and 0 45 1 as d 1 and d 2 respectively d 1 ranged from 2 60 to 2 71 and d 2 ranged from 2 71 to 2 82 d 1 was typically smaller than d 2 indicating that the smaller pores in shales were more homogeneous than the larger ones the formation of these om pores is owing to kerogen deformation during the thermal maturation which results in a large number of nanopores the pore structure of the longmaxi formation shales is primarily controlled by toc content and thermal maturity toc content is a controlling factor on the fractal dimensions as it exhibited positive correlations with d 1 and d 2 fractal dimensions are useful for the characterization of the pore structures complexity of the longmaxi formation shales because d 1 and d 2 correlate well with pore structure parameters as they both increase with the increase of surface area and the decrease of average pore diameter

enrichment and distribution of shale oil in the cretaceous qingshankou formation songliao basin northeast china abstract the songliao basin is a large scale petroliferous basin in china with a gradual decline in conventional oil production the exploration and development of replacement resources in the basin is becoming increasingly important previous studies have shown that the cretaceous qingshankou formation k2qn has favorable geological conditions for the formation of shale oil thus shale oil in the qingshankou formation represents a promising and practical replacement resource for conventional oil in this study geological field surveys core observation sample tests and the analysis of well logs were applied to study the geochemical and reservoir characteristics of shales identify shale oil beds build shale oil enrichment models and classify favorable exploration areas of shale oil from the cretaceous qingshankou formation the organic matter content is high in shales from the first member of the cretaceous qingshankou formation k2qn1 with average total organic carbon toc content exceeding 2 the organic matter is mainly derived from lower aquatic organisms in a reducing brackish to fresh water environment resulting in mostly type i kerogen the vitrinite reflectance ro and the temperature at which the maximum is release of hydrocarbons from cracking of kerogen occurred during pyrolysis tmax respectively range from 0 5 to 1 1 and from 430 c to 450 c indicating that the k2qn1 shales are in the low mature to mature stage ro ranges from 0 5 to 1 2 and currently generating a large amount of oil the favorable depth for oil generation and expulsion is 1800 2200 m and 1900 2500 m respectively as determined by basin modeling the reserving space of the k2qn1 shale oil includes micropores and mircofractures the micropore reservoirs are developed in shales interbedded with siltstones exhibiting high gamma ray gr high resistivity rt low density den and slightly abnormal spontaneous potential sp in the well logging curves the microfracture reservoirs are mainly thick shales with high rt high ac acoustic transit time high gr low den and abnormal sp based on the shale distribution geochemical characteristics reservoir types fracture development and the process of shale oil generation and enrichment the southern taikang and northern da an are classified as two favorable shale oil exploration areas in the songliao basin

organic matter clay mineral intergranular pores in the lower cambrian lujiaping shale in the north eastern part of the upper yangtze area china a possible microscopic mechanism for gas preservation abstract gas shales with a high gas content were encountered in the lower cambrian lujiaping formation in the northeast part of the upper yangtze area china in this area the tectonic condition is complex and the organic matter is over matured so conventional oil and gas exploration have not previously been considered during a recent shale gas exploration canister desorbed gas contents of more than 1 m 3 t were detected from 490 to 825 m depth with a maximum value of 3 18 m 3 t at 762 m hence to understand the mechanism of preservation of the gas is important the gas shales have a total organic carbon toc content of between 0 44 and 6 91 and vitrinite like macerals reflectance r o between 3 3 and 4 3 with type ii kerogen the porosity of 22 gas shale samples ranges between 0 4 and 2 29 and their permeability is between 6 9 10 5 and 3 8 10 1 md to investigate the shale s pore structure and its relation to gas storage behavior we studied the microscopic mechanism of gas preservation using a combination of pore characterization techniques including focused ion beam scanning electron microscope fib sem imaging and comparison of gas sorption and free gas storage capacity folding thrusting and subsequent rapid uplifting movements occurred after most of the dry gas had been originally generated and the present gas is a mixture originated from the cracking of liquid hydrocarbons at high maturity and kerogen pyrolysis in the early hydrocarbon generation phase sem observations combined with low temperature gas adsorption and mercury injection capillary pressure analyses show that pores within the organic matter or the mineral particles in the lujiaping shale are rare while the nanometer sized pores 1 4 nm between organic matter and clay mineral particles especially in cleavage domains are greatly developed thus the gas in these shales is mainly adsorbed gas due to the limited free gas storage space this is unlike most other shale gas reservoirs pores within the organic matter and pores between or within mineral particles are dominant moreover the desorbed gas content correlates well with toc content and the microporous and mesoporous specific surface area determined by low temperature co 2 and n 2 respectively suggesting that the nanometer sized pores associated with the organic matter make up the fundamental storage space for this shale the calculations based on fib sem observation showed that the nanometer sized intergranular pores have large specific surface areas with their small pore throat diameters resulting in high capillary pressure these characteristics have contributed to the preservation of shale gas in this complex tectonic area

shale oil potential and thermal maturity of the lower toarcian posidonia shale in nw europe a suite of drilling cores and outcrop samples of the lower toarcian posidonia shale ps were collected from multiple locations including the swabian alb and franconian alb of southwest germany runswick bay of uk and loon op zand well loz 1 of the west netherlands basin in order to assess the thermal maturity and quantify the petroleum generation potential of the rocks elemental analysis rock eval pyrolysis organic petrographic investigations and molecular hydrocarbon analyses were performed available literature data of the posidonia shale from luxembourg and northwest germany were used for comparison in the discussion the lower toarcian shale is more carbonate rich about 30 on average in sw germany nw germany and luxembourg and is instead more silicate rich in uk and nl with carbonate contents of about 15 on average this coincides with the relative distances of the depositional settings to the clastic source areas on the continents during the early jurassic however hi values are similar approx 500 700 mg hc g toc on average at all sampling localities exhibiting typical type ii kerogen with excellent hydrocarbon generation potential differences in relative abundance of terrigenous organic matter input are deduced from molecular indicators rock eval data and organic petrography the highest abundance of terrigenous organic matter is evident for runswick bay uk samples from outcrops of the lower toarcian shale from runswick bay uk have reached the early stage of the oil window with quite uniform t max values 425 438 c avg 433 c and a narrow range of pi production index values 0 10 0 19 substantiated by mature fluorescing characteristics of telalginite and lamalginite and vitrinite reflectance values of 0 6 0 7 wider ranges of t max values 421 443 c avg 427 c vitrinite reflectance 0 4 0 8 and production indices 0 06 0 29 suggest more variable thermal maturation ranging from immature to almost peak oil generation at the loz 1 well nl although only some intervals indicate advanced thermal maturity there in contrast the lower toarcian marlstones from the swabian and franconian alb of sw germany are clearly immature similar to the samples from luxembourg in nw germany the posidonia shale covers a wide spectrum of maturity ranging from immature to overmature source potential index spi indicates the highest value in the loz 1 nl followed by wickensen nw germany and esch sur alzette lu mainly due to differences in thickness of the studied sections the lowest value was observed in sw germany the lower toarcian jet rock in runswick bay uk is assumed to have a high shale oil potential because of its advanced thermal maturity although its spi is not high due to the limited thickness of the section studied the ps in sw germany has low shale oil potential due to low thermal maturity and limited thickness 2015 elsevier b v

fractal measurements of sandstones shales and carbonates measurements were made of the fractal properties of sandstones shales and carbonates using a statistical analysis of structural features on fracture surfaces fractal behavior is associated with power law behavior for the number of features as a function of the feature size on the pore rock interface only one sedimentary rock a novaculite was found not to have a fractal structure the fractal dimensions range from 2 27 to 2 89 and the long length limits to the fractal regime range from 2 m to over 50 m in all cases the fractal behavior extends to less than 0 2 m which is the measurement resolution the porosity associated with the fractal pore rock interface can be calculated from the fractal parameters some of the samples have additional porosity not associated with power law behavior photographs and other evidence are used to show that the fractal structures are the result of diagenesis fractal diagenetic structures include euhedral quartz overgrowths druse quartz calcite dolomite clays and chert

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

microfracturing and microporosity in shales shales are ubiquitous rocks in sedimentary basins where their low permeability makes them efficient seals for conventional oil and gas reservoirs and underground waste storage repositories waste waters co2 nuclear fuels moreover when they contain organic matter they form source rocks for hydrocarbons that may escape towards a more porous reservoir during burial a process referred to as primary migration and when the hydrocarbons cannot escape these rocks can be exploited as oil or shale gas reservoirs while the presence of fractures at the outcrop scale has been described the existence of fractures at smaller scales their link with microporosity the mechanisms that created them their persistence over geological times and their effect on the petrophysical properties of shales represent scientific challenges for which drillings in various sedimentary basins over the past decades may hold timely key data here we review and synthetize the current knowledge on how microfractures and micropores in shales can be imaged and characterized and how they control their anisotropic mechanical properties and permeability one question is whether such microfractures when observed in outcrops or in drilled core samples extracted from boreholes are related to decompaction and do not exist at depth another question is whether veins observed in shales represent microfractures that were open long enough to have acted as flow paths across the formation the mechanisms of microfracture development are described some have an internal origin fracturing by maturation of organic matter dehydration of clays while others are caused by external factors tectonic loading importantly the amount of microfracturing in shales is shown to depend strongly on the content in 1 organic matter and 2 strong minerals the nucleation of microfractures depends on the existence of mechanical heterogeneities down to the nanometer scale their propagation and linkage to create a percolating network will depend on the presence of heterogeneities at the meso to macro scales such percolating microfracture networks could control both the long term sealing capabilities of cap rocks and the further propagation of hydraulic fracturing cracks finally possible areas of research for describing the mechanism of microfracture formation in greater detail and how this impacts the transport and mechanical properties of shales are also discussed

characterization of pore systems in seal rocks using nitrogen gas adsorption combined with mercury injection capillary pressure techniques abstract porous microstructure parameters of seal rock samples originating from different depths within brazilian geological formations were correlated to empirical models which predict the intrinsic permeability mercury injection capillary pressure micp and nitrogen gas adsorption n 2 ga were applied in combination as complementary techniques micp to obtain the porosity values and the size distribution of meso and macropores and n 2 ga associated with the brunauer emmett and teller bet theory to determine the specific surface area s o the barret joyner and hallenda bjh theory was applied to find the size distribution of the micro and mesopores the combination of the micp and n 2 ga curves showed that the samples analyzed present a polymodal pore size distribution psd and a total porosity ranging from 0 33 to 10 44 the s o values measured by n 2 ga were higher than those calculated by micp due to the majority of the samples having a mean pore size of 20 1000 a the intrinsic permeability could also be predicted applying the measured parameters s o psd curves and total porosity in the carman kozeny and series parallel models the ranges of permeability values obtained were 4 09 10 24 4 96 10 21 m 2 and 9 48 10 27 9 14 10 22 m 2 respectively these results were compared with values reported in the related literature and those obtained for four samples submitted to pressure pulse decay permeability pdp tests

lithofacies and depositional setting of a highly prospective lacustrine shale oil succession from the upper cretaceous qingshankou formation in the gulong sag northern songliao basin northeast china the lacustrine shale of the upper cretaceous qingshankou formation is the principal prospective unconventional target lithology acting as source reservoir and seal lithofacies and associated storage capacity are two significant factors in shale oil prospectivity this paper describes an investigation of the lower qingshankou formation lacustrine shale based on detailed description and analysis of cores shale lithofacies characteristics depositional setting and stacking patterns seven lithofacies are recognized based on organic matter content sedimentary structure and mineralogy all exhibiting rapid vertical and lateral changes controlled by the depositional setting and basin evolution an overall trend from shallow water to deep water depositional environments is interpreted from the characteristics of the infilling sequences characterized by increasing total organic carbon toc and total clay content and decreasing layer thickness i e from bedded to laminated then to massive sedimentary structures periods of deposition during shallowing cycles show a reverse trend in the sedimentary characteristics described above the sedimentary rocks in the studied interval show three complete short term cycles each one containing progressive and regressive system tracts massive siliceous mudstones with both high and moderate toc are considered to have the best hydrocarbon generation potential laminated siliceous mudstones bedded siltstones and calcareous mudstones with moderate and low toc could have the same high hydrocarbon saturations as the high toc massive siliceous mudstones but these lithologies contain more brittle minerals than the massive mudstones several siltstone samples show low or zero saturation of in situ hydrocarbons this is considered to be related to a combination of fair to poor hydrocarbon generation potential and extremely low permeability limiting migration moderate toc laminated siliceous mudstones were also observed to have connective pore fracture networks it can be demonstrated that successive thick sequences of moderate toc laminated siliceous mudstones showing high volumes of hydrocarbon in situ a high mineral brittleness index and good permeability combine to form shale oil exploration sweet spots

shale characteristics in the southeastern ordos basin china implications for hydrocarbon accumulation conditions and the potential of continental shales abstract continental shales in china are generally characterised by low thermal maturity and high clay content characteristics that are significantly different from those of marine shales documented in the usa and elsewhere whether such continental shales have commercial hydrocarbon potential as marine shale in the usa is a question for the china petroleum industry recently vertical drills in the lacustrine shales in the yanchang formation produced an average of two to five tons of oil and 1000 3000 m3 of gas per day by reservoir hydraulic fracturing which demonstrates that the continental shales can also achieve viable hydrocarbon production shale and gas samples collected from the chang 7 c7 and chang 9 c9 members yanchang formation in the southeastern ordos basin were examined for geochemical petrologic and gas content analysis the results show that the c7 and c9 members developed a huge volume of organic rich shales with 2 4 wt toc in the deep or semideep lacustrine characterised primarily by type ii kerogen with a relatively low thermal maturity and a vitrinite reflectance ranging from 0 5 to 1 5 ro which decreases from west to east the hydrocarbon product varies with the thermal maturity in the southwestern corner the gas content measured by canister desorption equals 1 15 3 49 m3 t rock and the gas absorption capacity ranges from 3 to 5 m3 t rock whereas in the eastern part the gas content is low and oil production is 1 4 m3 day on average nanometre scale pores and micro fractures are well developed all of this indicates that the continental shales in the southeastern ordos basin might have huge shale hydrocarbon resources however the clay content of the continental shales of c7 and c9 ranging from 40 to 60 of the bulk mineral content are much higher than for gas produced in marine shales which might lead to significant challenges for successful development

pore throat sizes in sandstones tight sandstones and shales pore throat sizes in siliciclastic rocks form a continuum from the submillimeter to the nanometer scale that continuum is documented in this article using previously published data on the pore and pore throat sizes of conventional reservoir rocks tight gas sandstones and shales for measures of central tendency mean mode median pore throatsizes diameters are generally greater than2 mm in conventionalreservoir rocks range from about 2 to 0 03 mm in tight gas sandstones and rangefrom0 1to0 005 mminshales hydrocarbonmolecules asphaltenes ring structures paraffins and methane form another continuum ranging from 100 a 0 01 mm for asphaltenes to 3 8 a 0 00038 mm for methane the pore throat size continuum provides a useful perspective for considering 1 the emplacement of petroleum in consolidated siliciclastics and 2 fluid flow through fine grained source rocks now being exploited as reservoirs

qualitative and quantitative prediction of diagenetic facies via well logs abstract drilled cores thin section petrography x ray diffraction xrd scanning electron microscopy sem routine core analysis rca and mercury injection capillary pressure micp tests were used to establish a predictable model for diagenetic facies and reservoir quality using well logs in sandstones of the paleogene dongying formation in nanpu sag bohai bay basin eastern china the results show that the sandstones are texturally and compositionally immature and have primary intergranular pores secondary intergranular and intragranular pores moldic pores and micro pores associated with diagenetic clay minerals the sandstones have undergone low to moderate mechanical compaction but a high degree of framework grain dissolution diagenetic minerals are dominantly of carbonates calcite dolomite and fe dolomite and clay minerals illite mixed layer illite smectite and kaolinite four types of diagentic facies are recognized tightly compacted carbonate cemented clay mineral filling and dissolution facies porosity permeability and oil saturation ranges among these diagenetic facies were determined from routine core analyses the diagenetic facies were then translated to conventional well logs by core log calibration and the well log expressions in terms of natural gamma ray neutron porosity bulk density sonic transit time and resistivity logs of various diagenetic facies were summarized the mineralogical composition obtained from the elemental capture spectroscopy ecs logs was then used for the diagenetic facies prediction the diagenetic facies predicted with the comprehensive conventional log analyses were combined with the ecs log profile and were calibrated with the xrd sem analysis and logging interpretation results for wells without ecs log the diagenetic facies can be quantitatively predicted by the mathematical calculations of reservoir quality index rqi via the gr ac and den log curves reservoir quality or oil bearing properties can be evaluated and predicted by translating the diagenetic facies to well logs

multifractal analysis of discretized x ray ct images for the characterization of soil macropore structures a correct statistical model of soil pore structure can be critical for understanding flow and transport processes in soils and creating synthetic soil pore spaces for hypothetical and model testing and evaluating similarity of pore spaces of different soils advanced visualization techniques such as x ray computed tomography ct offer new opportunities of exploring heterogeneity of soil properties at horizon or aggregate scales simple fractal models such as fractional brownian motion that have been proposed to capture the complex behavior of soil spatial variation at field scale rarely simulate irregularity patterns displayed by spatial series of soil properties the objective of this work was to use ct data to test the hypothesis that soil pore structure at the horizon scale may be represented by multifractal models x ray ct scans of twelve water saturated 20 cm long soil columns with diameters of 7 5 cm were analyzed a reconstruction algorithm was applied to convert the x ray ct data into a stack of 1480 grayscale digital images with a voxel resolution of 110 microns and a cross sectional size of 690 690 pixels the images were binarized and the spatial series of the percentage of void space vs depth was analyzed to evaluate the applicability of the multifractal model the series of depth dependent macroporosity values exhibited a well defined multifractal structure that was revealed by singularity and renyi spectra the long range dependencies in these series were parameterized by the hurst exponent values of the hurst exponent close to one were observed indicating the strong persistence in variations of porosity with depth the multifractal modeling of soil macropore structure can be an efficient method for parameterizing and simulating the vertical spatial heterogeneity of soil pore space

fractal analysis of tight shaly sandstones using nuclear magnetic resonance measurements assessing quantitatively the microscopic pore structures of porous rocks including irregularities of pore shapes and pore size distributions is becoming one of the most challenging efforts nuclear magnetic resonance nmr measurements were used to provide insights into the pore geometry pore size and shape and pore connectivity of the chang 7 tight shaly sandstones in situ permeability 0 1 md in ordos basin the incremental transverse relaxation time t2 distributions for the 100 brine saturated samples display unimodal and bimodal behaviors presenting a geometrical arrangement composed of small to large pore size domains the nmr parameters such as bulk volume irreducible bvi capillary and clay bound water free fluid index ffi movable water the value of t2 separating the bvi from ffi the amplitude weighted mean on a logarithmic scale t2gm and the value of t2 that shows the highest frequency on the t2 spectrum t2peak for each sample were determined then the fractal theory was adopted to quantitatively express the complexity and heterogeneity of the sandstones the results show that only minor primary intergranular porosity remains and variable amounts of micropores and secondary intragranular porosity with poor connectivity occur in the chang 7 tight shaly sandstones assuming spherical pores a new model to calculate the fractal dimension of pore structure from the nmr t2 distributions is proposed the fractal dimensions of all the samples are calculated and the accuracy of the proposed model is verified by the regression coefficients the microscopic pore structures are heterogeneous in these tight sandstones according to the high value of fractal dimensions micropores are the primary causes of heterogeneity in tight sandstones and samples with unimodal t2 distribution behaviors and high content of short components have the highest fractal dimension and heterogeneity the calculated fractal dimension is strongly correlated with t2peak and t2gm therefore the fractal model proposed in this study can be used to calculate the fractal dimensions and evaluate the heterogeneities of the porous rocks satisfactorily the fractal model proposed in this study helps to quantitatively assess the pore structures of tight sandstones using nmr measurements

exploration breakthroughs and geological characteristics of continental shale oil a case study of the kongdian formation in the cangdong sag china abstract petroleum geology and deposition features of the fine grain phase region in the second member of the kongdian formation were investigated using traditional petroleum geology and sedimentary petrology new theories for shale oil and gas formation based on data from 500 m continuous coring systematic analysis of over ten thousand core samples and logging data in the center of the lake basin in the cangdong sag bohai bay basin china were developed to determine the distribution of shale oil and provide a basis for shale oil exploration deployment results showed that a wide distribution of semi deep to deep lake sub facies fine grained sediment shale was deposited in the study area during the largest lake flooding period this sediment consists of felsic shale mixed shale and dolomites but no clay shale the shale features multiple rock components with few dominant minerals high clastic mineral content and low clay mineral content rich analcite and lean pyrite rich brittle minerals with lean quartz diverse rock types with limited shale oil more tight reservoirs and fewer reservoirs with no fractures more high quality source rock with less non hydrocarbon source rock and more high frequency cycles with fewer monolithic deposits results indicate that dolomites are located in strips on the plane and are locally enriched contradicting the understanding that only hydrocarbon source rock and no reservoirs develop in the middle of a continental closed lake basin the study region demonstrates good conditions for shale oil formation a favorable configuration of source rock and reservoirs and 260 km2 of sweet spots indicating high exploration value several prospecting wells have obtained industrial oil flow with guidance based on geological knowledge and engineering technology support

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

nanoscale pore structure and fractal characteristics of a marine continental transitional shale a case study from the lower permian shanxi shale in the southeastern ordos basin china abstract shale samples collected from seven wells in the southeastern ordos basin were tested to investigate quantitatively the pore structure and fractal characteristics of the lower permian shanxi shale which was deposited in a marine continental transitional hereinafter referred to as the transitional environment low pressure nitrogen adsorption data show that the shanxi shale exhibits considerably much lower surface area sa and pore volume pv in the range of 0 6 1 3 m 2 g and 0 25 0 9 ml 100 g respectively type iii kerogen abundant in the transitional shanxi shale were observed to be poorly developed in the organic pores in spite of being highly mature which resulted in a small contribution of organic matter om to the sa and pv instead i s illite smectite mixed clay together with illite jointly contributed mostly to the sa and pv as a result of the large amount of inter layer pores associated with them which were evident in broad ion beam bib imaging and statistical analysis additionally the shanxi shale has fractal geometries of both pore surface and pore structure with the pore surface fractal dimension d1 ranging from 2 16 to 2 42 and the pore structure fractal dimension d2 ranging from 2 49 to 2 68 respectively the d1 values denote a pore surface irregularity increase with an increase in i s and illite content attributed to their more irregular pore surface compared with other mineralogical compositions and om the fractal dimension d2 characterizing the pore structure complexity is closely related to the pore arrangement and connectivity and i s and illite decrease the d2 when their contents increase due to the incremental ordering degree and connectivity of i s or illite hosted pores meanwhile other shale constituents including kaolinite chlorite and om that possess few pores can significantly increase the pore structure complexity by way of pore blocking

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

relationship between pore type and pore size of marine shale an example from the sinian cambrian formation upper yangtze region south china abstract to clarify the size distribution of different types of shale pores nine sinian cambrian shale samples from south china were examined using ion milling fe sem nitrogen adsorption and mercury intrusion image based point counting data indicated that nanopores are predominant whereas pores larger than 1 m are absent organic matter hosted pores dominate below 130 nm whereas intraparticle pores within carbonate probably caused by dissolution constitute most pores larger than 400 nm the small amount of residual intraparticle and interparticle pores associated with rigid minerals mostly range from 50 nm to 250 nm a positive relationship was found between the toc and total pore volume measured by nitrogen and mercury the mercury volume of pores larger than 300 nm increased with increasing dolomite and decreasing clay mineral content the statistics from image analysis and the relationship between pore volume and shale components were in good agreement indicating that different types of pores have their own relative restricted size range generally intrap pores are larger than pores associated with rigid minerals whereas the om pores and interp pores associated with om or clay are the smallest through a comparison with other less matured shale formations the highly matured equivalent vitrinite reflectance above 3 sinian cambrian shale in south china was characterized in this study as those with smaller interp pores which is probably due to a stronger compacting effect

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

the topographic and gravitational expression of density anomalies due to melt extraction in the uppermost oceanic mantle abstract evidence suggests that basaltic extrusion can decrease the density of the depleted source region by up to 2 for 20 partial melting this hypothesis is tested by calculating the effect of the density anomaly between the depleted and undepleted mantle on the topography gravity and geoid fields and comparing the anomalies to the observed topography gravity and geoid anomalies over volcanic features in the oceans if the source region lies at the base of the lithosphere we find that the gravity and geoid anomalies are proportionally more sensitive to the density contrast than the topography anomaly this effect is most pronounced for wavelengths less than 1000 km since mid ocean ridge volcanism the largest source of volcanism in the oceanic plates is fairly uniform along the ridge the depleted material in the oceanic plates and the corresponding topography and gravity anomalies should also be somewhat uniform in extent any long wavelength anomalies will be obscured in the topography and geoid fields by other anomalies at similar wavelengths such as slab and deep mantle anomalies however at mid plate swells and seamounts if the density contrast is greater than 0 4 the topography gravity and geoid anomalies are measurable to be consistent with the wavelengths represented in the geoid and topography data at hawaii the depleted material must be spread into a thin layer by convective flow at mid plate swells even in the thin layer model the topography and geoid anomalies due to the depleted material would still be as large as 200 m and 2 m respectively after the convective flow producing the bulk of the swell is removed the anomaly due to the depleted material would remain and would be apparent in the geoid and topography fields at seamounts if the source region is near the base of the plate then the presence of depleted material should be distinguishable in the geoid field but be somewhat obscured by flexural effects therefore although a topographic or geoid anomaly due to depletion has not been observed the density anomaly cannot be discounted because only careful scrutiny and modelling of mid plate swells and seamounts would distinguish its effect

clarifying pore diameter pore width and their relationship through pressure measurements a critical study abstract understanding geometrical and topological properties of the pore space in permeable media is of paramount importance particularly in oil and gas production pore space characteristics such as pore sizes and their probability distributions as well as pore s connectivity are main factors in the modeling of fluid flow and chemical transport in soils and rocks a common method to determine the pore size is to convert an implemented pressure via either the young laplace or kelvin equation by assuming a specific pore shape simple geometries such as cylindrical and slit shaped have been frequently used in the literature particularly to represent pores and to derive theoretical models estimating permeability from pore throat size distribution in this study we clarify the relationship between pore diameter d and pore width w two terms interchangeably used in the literature the former corresponds to a cylindrical pore while the latter to a slit shaped one we emphasize that d 2w in contrast to previously published studies claiming that the diameter of a cylindrical pore is equal to the distance between sides of a slit shaped pore i e d w in addition we discuss that comparing combining pore size distribution derived from mercury intrusion porosimetry and that determined from nitrogen adsorption isotherm is not supported unless the effect of hysteresis is trivial as most probably the former represents pore throat while the latter pore body size distributions

a preliminary study on the pore characterization of lower silurian black shales in the chuandong thrust fold belt southwestern china using low pressure n2 adsorption and fe sem methods although lower silurian black shales within and around the sichuan basin have received renewed attention during the past few years because of their potential prospectivity for shale gas studies associated with shale gas reservoir evaluation are still rare in this study eight black shale core samples were collected from a well drilled recently in the chuandong thrust fold belt southwestern china and their geochemistry and pore structures were investigated using low pressure n2 adsorption analysis and field emission scanning electron microscopy fe sem observations the results show that the black shales have total organic carbon toc values ranging from 1 01 to 3 98 and their equivalent vitrinite reflectance values are in the range of 2 84 3 05 both mineral matrix and organic matter pores are well developed with pore sizes ranging from several to several hundred nanometers the total porosity for the eight samples ranges from 2 60 to 4 74 and the percentages of organic matter pores are estimated to be in the range of 31 62 the total surface area ranges from 5 06 m2 g to 19 32 m2 g and the micropore 2 nm surface area estimated by the t plot method ranges from 3 13 m2 g to 9 27 m2 g the toc values have positive relationships with the total porosity total surface area and the micropore 2 nm volume and surface area indicating toc may be an effective parameter for shale gas reservoir evaluation in the studied area

investigation on the pore structure and multifractal characteristics of tight oil reservoirs using nmr measurements permian lucaogou formation in jimusaer sag junggar basin abstract pore structure is a critical parameter to estimate the reservoir quality and evaluate the resource potential however the pore structure and heterogeneity of the unconventional tight oil reservoirs of permian lucaogou formation of jimusaer sag junggar basin are not studied well in this paper the multifractal analysis based on the nmr t 2 distributions was applied to investigate the pore structure and heterogeneity the reservoir quality index rqi and flow zone indicator fzi were calculated using porosity and permeability two parameters t 35 and t 50 were newly defined as relaxation times corresponding to the 35 and 50 saturation on the t 2 reverse accumulative curve respectively the results showed that the rqi and fzi values were extremely low and that the nmr t 2 distributions of water saturated samples had much short relaxation components with no or little long relaxation components indicating a complex and poor microscopic pore structure of tight oil rocks the typical multifractal characteristics such as the large values of singularity strength range revealed that the pore structures of samples were strongly heterogeneous it was also found that the clay contents have an obvious influence on the multifractal parameters and the fzi and new defined t 35 are two good indicators for heterogeneity of pore structure in addition the feasibility and applicability of calculating the multifractal parameters from nmr and other well logs were discussed

density and size distribution of seamounts in the eastern pacific inferred from wide beam sounding data theoretical expressions relating the distribution of apparent seamount heights per unit length of ship track to the distribution of actual seamount heights per unit area of seafloor are derived for both narrow beam and wide beam echo sounders the shapes of seamounts are approximated as truncated right circular cones of constant slope e height to radius ratio and flatness f i e a seamount of basal radius r has a height h r a flat top of radius fr and a slope angle of arctan e the set of all seamounts in a given physiographic province is assumed to be a poissonian ensemble specified by a function v r the average number of seamounts per unit area for which r r a simple choice for the size distribution of seamounts and one shown to be consistent with data in the eastern pacific is to specify that it decays exponentially with r v r vo exp r in the case of a profile of length l taken in water of depth d with a wide beam echo sounder half beam width the shallow slope deep water approximation e 1 e d yields that the expected number of seamounts with apparent heights h h is n h l 2 1 ed 2 fh lv0e h we apply this sampling theory to apparent height data measured from 44 020 km of wide beam profiles on pacific crust of post mesozoic age although the spatial distribution of seamounts in the eastern pacific is certainly not poissonian the abundance statistics do not involve spatial correlations and we show they are robust with respect to deviations from the poisson model provided the statistics are interpreted as averages over the area actually sampled by the track lines the observed falloff of apparent heights in the eastern pacific is very nearly exponential justifying our use of an exponential model of seamount size distribution the shape parameters are estimated from multibeam surveys of pacific seamounts an analysis of 30 features in the height range 200 4000 m yields 0 21 0 011 and f 0 21 0 028 using these parameters we obtain vo 4 0 1 1 10 9 m 2 and 6 3 0 8 10 4 m 1 these values imply that per 106 km2 in the eastern pacific there are 1600 400 seamounts with summit heights greater than 300 m and 200 60 greater than 1000 m integrated over the entire size distribution seamounts occupy about 6 of the seafloor area and constitute about 0 4 of the oceanic crustal volume our estimates of seamount abundance are appreciably greater than those of most other authors a discrepancy we attribute primarily to the sampling bias of previous studies which generally used uncorrected map counts this hypothesis is corroborated by a comparison of our statistics with map count data for seamounts of heights exceeding 2000 m compiled for the eastern central pacific from the scripps charts above 3000 m the map counts are consistent with the predictions of the exponential model but below this height they are biased to low values

origin and formation mechanisms of low oil saturation reservoirs in nanpu sag bohai bay basin china abstract low oil saturation reservoirs are increasingly encountered in superimposed sedimentary basins however the uncertainty about the origin of the low oil saturation becomes a major factor impeding further hydrocarbon exploration routine core analysis fluorescence thin section scanning electron microscope sem and nuclear magnetic resonance nmr measurements were used to understand the characteristics and formation mechanisms of the low oil saturation reservoirs in the paleogene dongying formation in the nanpu sag bohai bay basin east china irreducible water saturation was determined from sealed coring oil saturation testing and nmr logs wide ranges of porosity and permeability were observed and the samples with moderate reservoir quality have the best oil bearing property low oil saturation oil layers are characterized by low oil saturation 40 with only oil being produced whereas no water or only minor amounts of water being produced the low oil saturation oil water reservoirs refer to the low oil saturation layers in which both oil and water will be produced during oil testing irreducible water saturation increases with total clay content with the authigenic clays kaolinite illite and mixed layer illite smectite blocking pore spaces and resulting in high irreducible water saturations fluorescence thin sections combined with nmr measurements show that the nmr t2 transversal relaxation time distribution is uni modal with large intergranular pores being rare almost the entire pore size range is oil bearing for the low oil saturation oil reservoirs the large intergranular pores are fluorescence free while the intragranular dissolution pores and micropores emit fluorescence in the low oil saturation oil water reservoirs the nmr t2 distribution of low oil saturation oil water reservoirs is bi modal and right skewed and the main oil bearing nmr pore size distribution ranges from 0 1 to 100 ms high irreducible water content was encountered in the low oil saturation oil reservoirs and low oil saturation oil water reservoirs and only part of the large intergranular pores are oil saturated and in some cases only the intragranular pores are saturated with oils forming low oil saturation oil reservoirs the results help improve the knowledge of characteristics and formation of the low oil saturation oil layers and could provide insights in enhancing oil recovery

insights in the pore structure fluid mobility and oiliness in oil shales of paleogene funing formation in subei basin china abstract pore structure is an important factor influencing reservoir properties of oil shales routine core analysis thin section scanning electron microscope sem mercury injection capillary pressure micp tests nuclear magnetic resonance nmr and computed tomography ct were used to provide insights into the pore throat distribution in oil shales of member 2 of paleogene funing formation e1f2 in subei basin china with the special aim to unravel the effect of pore structure on fluid mobility and oiliness the relationships between nmr parameters petrophysical property and capillary parameters are investigated the results show that rock composition in the oil shales consist of quartz feldspar carbonate particles clay minerals and organic matters pore systems consist of large scale interparticle pores intragranular dissolution pores and small scale micropores within clay minerals and the organic matter pores four types of pore structure type type type and type are divided according to the patterns of capillary curves capillary parameters nmr t2 transverse relaxation time spectrum and bvi bulk volume of immovable fluid values from type to type pore structure the maximum mercury saturation shgmax and mercury extrusion efficiency are decreasing and the shgmax are less than 50 averagely indicating the oil shales are characterized by very poor pore connectivity the t2 spectrum changes from bi modal behavior to uni modal and the right peaks become lower or even disappearing from type to type pore structure fluid mobility is not primarily controlled by pore size but dependent on the content of short t2 components pore structure controlled fluid mobility and determined the microscopic oiliness and macroscopic oil bearing property or hydrocarbon productivity the comprehensive study above gains insights into the microscopic pore structure and their controls on fluid mobility and oiliness in shale oil reservoirs and this may have implications for resource potential evaluation and effective exploitation of oil shales

the heterogeneity of pore structure in lacustrine shales insights from multifractal analysis using n2 adsorption and mercury intrusion abstract a series of parameters from a variety of techniques such as pore size distribution surface area pore volume etc have been used to characterize the pore structure of unconventional shale reservoirs however the investigation on the quantification of pore structure heterogeneity is still scarce in this aspect a multifractal theory combined with n2 adsorption and mercury intrusion was used to obtain pore structure characteristics and quantify the heterogeneity of pore size distribution of nine lacustrine shale samples from the second member of kongdian formation ek2 in cangdong sag bohai bay basin china the results show that the ek2 shale contains complex pore network and pores with small pore size predominate in pore system both n2 adsorption branches and pore throat size distributions from mercury intrusion demonstrate multifractal nature the width of singularity spectra from multifractal analysis is used to quantitatively characterize the heterogeneity degree of pore size distribution and shows good consistency with pore size distributions derived from n2 adsorption and mercury intrusion the pore structure from mercury intrusion is much heterogeneous than that from n2 adsorption indicating that an increased number of large pores will increase the heterogeneity of pore size distributions compared with other rock compositions toc has an obvious impact on the heterogeneity of pore structure in small pore size range

pore characteristics of longmaxi shale gas reservoir in the northwest of guizhou china investigations using small angle neutron scattering sans helium pycnometry and gas sorption isotherm abstract small angle neutron scattering sans helium pycnometry and low pressure gas sorption isotherm experiments were used to investigate the pore characteristics of longmaxi shale the leading producing formation in china this work is the first microstructural study of chinese marine shales by neutron scattering technique the polydisperse spheres model pdsp was used for sans data analysis to obtain porosity and pore size distribution psd and the results were compared with those from gas co2 n2 adsorption and helium pycnometry by evaluating the difference of porosities determined from these methods the closed fraction of shale pores are derived and discussed moreover the porosity has a positive correlation with total organic carbon toc in longmaxi shale samples the fractal dimension of shale samples was derived and results indicated that longmaxi shale is a mass fractal a lower mass fractal dimension means less closed pores with correspondingly more open structures

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

typical geological characteristics and exploration practices of lacustrine shale oil a case study of the kong 2 member strata of the cangdong sag in the bohai bay basin abstract successful development of marine shale oil in north america has advanced the researches on lacustrine shale oil in china however there remains no unified understanding of certain issues such as the exploration prospects of lacustrine shale oil to determine the typical geological characteristics and exploration potential of lacustrine shale oil in china the shale strata of the kong 2 member in the cangdong sag was selected as a study system the geologic setting characteristics and distribution of sweet spots as well as the exploration prospects of lacustrine shale oil were analyzed using 635 8 m cores and the analytical data for 12 000 core samples from three wells g108 8 gd12 and gd14 oil testing and production testing data from multiple wells were also evaluated results show that the shale oil developed in a slightly reductive and tectonically stable sedimentary environment the shale strata are composed of various minerals including mainly quartz feldspar and dolomite with abundant laminae samples with total organic carbon toc values 1 account for 75 of the shales which are primarily type i and type ii 1 kerogen with thermal maturities between 0 5 and 1 1 and formed during the oil window these lacustrine shales have multiple types of reservoir spaces including organic pores intercrystalline pores intergranular pores microfractures and laminar fractures with an average all averages are arithmetic means osi index pyrolysis s1 100 toc of 147 1 mg oil g toc and an average brittleness index 50 the reexamination of old wells and horizontal well exploration aimed at the sweet spots of type ia and ib oils have achieved promising results well kn9 had a daily oil production of 29 6 m3 after fracturing and horizontal well gd1701h exhibited its highest daily oil production at 75 9 m3 and currently produces 21 24m3consistently well gd1702h had a maximum daily oil production of 61 m3 and stably produces 20 25 m3 at present the resources of the ek21sq sequence calculated using amass oil content method were 208 million tons confirming the extensive exploration potential of shale oil in this lacustrine lake basin