geochemical and geological characteristics of the es3l lacustrine shale in the bonan sag bohai bay basin china abstract although extensive studies have been conducted on unconventional shale oil resources in recent years little work has been performed on the resource potential of lacustrine shales the es3l lower sub member of the third member of the eocene shahejie formation shale of the bonan sag a set of thick lacustrine deposited sediments offers a good example for furthering the understanding of these rocks geochemical and mineralogical investigations were carried out on a large sample set from the 220 m thick sequence of well luo69 in total 200 core samples were analyzed for total organic carbon toc and rock eval pyrolysis and 421 core samples were analyzed for mineral compositions the es3l shales have a very high toc content with type i lacustrine oil prone kerogen in the early oil generation stage rock eval tmax suppression is evident in the lower part of the es3l member associated with a rise in pi production index with respect to fracability or brittleness the content of brittle minerals in the es3l shale is generally higher than that of marine shales in the usa with higher calcite mineral averaging 51 82 wt and lower clay content averaging 18 86 wt interparticle pores in minerals grains or clay aggregates intraparticle pores intercrystalline dolomite and pyrite framboid and four types of fractures tectonic fractures abnormal pressure fractures clay shrinkage fractures and inter laminar fractures are developed in the es3l shale organic matter pores are not present in the studied samples probably due to lower maturity tectonic fracture may play an important role in hydrocarbon migration and accumulation the results of this study suggest that the es3l shale in the bonan sag has very good shale oil potential especially in the lower section

the composition and its impact on the methane sorption of lacustrine shales from the upper triassic yanchang formation ordos basin china abstract the organic geochemistry mineralogy and methane sorption of lacustrine shales of the upper triassic yanchang formation collected from the south eastern ordos basin were investigated to characterize them and clarify the effects of shale composition on their sorbed gas capacity these yanchang shales have recently been selected as a target area for shale gas exploration in typical terrestrial strata in china the two main sections of these shales containing type ii organic matters chang 7 and chang 9 have relatively high total organic carbon content toc of 2 10 the two shales also have similar mineralogies mainly comprising quartz clay minerals and feldspars both the chang 7 and chang 9 shales are generally in the oil window chang 9 is slightly more mature than chang 7 higher methane sorption capacity was observed for chang 9 than for chang 7 shales determined on a dried basis at 50 c methane sorption measurements were further performed on three samples from which the residual bitumen had been extracted and their corresponding kerogen fractions to gain insight into the effects of shale composition on methane sorption this was significantly higher in solvent extracted samples than in raw samples indicating that residual bitumen largely restricts methane sorption on such shales a positive correlation between the amount of clay minerals and methane sorption capacity of bulk rocks was evident suggesting that clay mineral content is relevant to methane sorption this result was also supported by the much higher methane sorption capacity of solvent extracted shales compared to the extracted kerogen from those shales when measured sorption data was normalized to toc values the effects of both residual bitumen and clay mineral on the methane sorption of bulk rocks have complicated the evaluation of methane sorption on organic matter in these mature shales

regional warming pliocene 3 ma paleoclimate of europe and the mediterranean the paleoclimate of the middle pliocene ca 3 ma was generally warmer than present particularly at middle to high latitudes it has been suggested that this period may represent an analogue for future climate change mechanisms that have been proposed to account for this warming are enhanced thermohaline circulation and or greater concentrations of co 2 in the atmosphere we present new climate model simulations supported by geological data that suggest that in the european and mediterranean region the climate was warmer by 5 c wetter by 400 1000 mm yr and less seasonal than present modeling results suggest that an intensification of the icelandic low pressure system and the azores high pressure system occurred during the middle pliocene as a direct result of higher annual sea surface temperatures and reduced ice cover in the northern hemisphere this change increased the surface pressure gradient over the region and strengthened annual westerly wind velocity by 4 m s 1 associated increases in wind stress by 20 n m 2 over the north atlantic ocean may have enhanced the flow of surface currents such as the gulf stream and north atlantic current which in turn would have sustained the higher sea surface temperatures these changes to the regional climate system would have driven greater atmospheric and oceanic transport of heat from equatorial regions to the north atlantic ocean particularly during winter such conditions are proposed as a likely cause of the warming indicated for europe and the mediterranean ca 3 ma

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 pressure water pyrolysis of coal to evaluate the role of pressure on hydrocarbon generation and source rock maturation at high maturities under geological conditions this study investigates the effect of water pressure on hydrocarbon generation and source rock maturation at high maturities for a perhydrous tertiary arctic coal svalbard using a 25 ml hastalloy vessel the coal was pyrolysed under low water pressure 230 300 bar and high water pressure 500 700 and 900 bar conditions between 380 c and 420 c for 24 h at 380 c and 420 c gas yields were not affected by pressure up to 700 bar but were reduced slightly at 900 bar at 380 c the expelled oil yield was highest at 230 bar but reduced significantly at 900 bar at 420 c cracking of expelled oil to gas was retarded at 700 and 900 bar as well as direct cracking of the coal the main source of gas generation at high pressure at both 380 c and 420 c is from bitumen trapped in the coal indicating that this is a key mechanism in high pressure geological basins vitrinite reflectance vr was reduced by 0 16 ro at 380 c and by 0 27 ro at 420 c at 900 bar compared to the low pressure runs indicating that source rock maturation will be more retarded at higher maturities in high pressure geological basins

graptolite derived organic matter in the wufeng longmaxi formations upper ordovician lower silurian of southeastern chongqing china implications for gas shale evaluation abstract the organic rich shales of the wufeng longmaxi formations ordovician silurian are one of the most important hydrocarbon source rocks and shale gas exploration targets in china graptolites are abundant in these shales but their contribution to the dispersed organic matter om has been overlooked this lack of attention could seriously affect the evaluation of om type om maturity hydrocarbon generation potential reservoir characteristics and gas content of these shales optical microscope and focused ion beam scanning electron microscope fib sem techniques were employed to describe the optical characteristics and micro nanopores of the graptolites to determine the contribution of the graptolites and to evaluate the thermal maturity of the wufeng longmaxi formations non granular graptolites which show a stronger anisotropy and higher reflectance under polarized light than the granular graptolites were primarily observed in these sediments graptolites account for 20 93 of the dispersed om in the wufeng longmaxi formations and the level of their contribution has been attributed to the radiation of graptolites at the late ordovician kaptian and the recovery of graptolites at the early silurian rhuddanian the bireflectance values of the non granular graptolites fall between 2 22 and 4 32 indicating a behavior similar to biaxial anthracitic vitrinite the equivalent vitrinite reflectance eqvro values of the sediments in the wufeng longmaxi formations calculated from the mean maximum reflectance of non granular graptolite fall in the range of 3 08 4 29 and these values have a precision that is greater than in previous studies on the wufeng longmaxi formations abundant organic pores were observed in the non granular graptolites and they are aligned parallel to the fusellar layers of the graptolites this indicates that the fusellar layers of non granular graptolites controlled the development and distribution of organic pores such abundant organic pores played a significant role in the accumulation of shale gas in the wufeng longmaxi formations of the upper yangtze platform

the progressive intensification of northern hemisphere glaciation as seen from the north pacific ocean drilling project odp site 882 50 22 n 167 36 e provides the first high resolution grape density magnetic susceptibility carbonate opal and foraminifera planktonic and benthic stable isotopes records between 3 2 and 2 4 ma in the northwest pacific we observed a dramatic increase in ice rafting debris at site 882 at 2 75 ma which is coeval with that found in the norwegian sea suggesting that the eurasian arctic and northeast asia were significantly glaciated from 2 75 ma onwards prior to 2 75 ma planktonic foraminifera 18o records indicate a warming or freshening trend of 4 c or 2 over 80 ka if this is interpreted as a warm pre glacial pliocene north pacific it may have provided the additional moisture required to initially build up the northern hemisphere continental ice sheet the dramatic drop in sea surface temperatures sst 7 5 c at 2 75 ma ended this suggested period of enhanced sst and thus the proposed moisture pump moreover at 2 79 and 2 73 ma opal mass accumulation rates mar decrease in two steps by five fold and is accompanied by a more gradual long term decrease in caco3 mars evidence from the southern ocean odp site 704 indicates that just prior to 2 6 ma there is a massive increase in opal mars the opposite to what is found in the north pacific this indicates that the intensification of northern hemisphere glaciation was accompanied by a major reorganisation of global oceanic chemical budget possibly caused by changes in deep ocean circulation the initiation of northern hemisphere glaciation occurred in the late miocene with a significant build up of ice on southern greenland however the progressive intensification did not occur until 3 5 3 ma when the greenland ice sheet expanded to include northern greenland following this stage we suggest that the eurasian arctic and northeast asia glaciated at 2 75 ma approximately 100 ka before the glaciation of alaska 2 65 ma and 200 ka before the glaciation of the north east american continent 2 54 ma

land surface feedbacks and palaeomonsoons in northern africa we ran a sequence of climate model experiments for 6000 years ago with land surface conditions based on a realistic map of palaeovegetation lakes and wetlands to quantify the effects of land surface feedbacks in the saharan region vegetation induced albedo and moisture flux changes produced year round warming forced the monsoon to 17 25 n two months earlier and shifted the precipitation belt 300 km northwards compared to the effects of orbital forcing alone the addition of lakes and wetlands produced localised changes in evaporation and precipitation but caused no further extension of the monsoon belt diagnostic analyses with biome and continental hydrology models showed that the combined land surface feedbacks although substantial could neither maintain grassland as far north as observed 26 n nor maintain lake megachad 330 000 km

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

optical characteristics of graptolite bearing sediments and its implication for thermal maturity assessment abstract graptolite reflectance was thought to be one of the most useful thermal maturity indicators for graptolite bearing sediments however the relationship between graptolite reflectance and vitrinite reflectance is not well established graptolites especially in the wufeng longmaxi formations from the ordovician to silurian of south china have been mistaken for vitrinite like particles or solid bitumen which results in inconsistent data on the thermal maturity in this paper we have employed optical microscope techniques to describe the detailed optical characteristics of graptolites and solid bitumen in the wufeng longmaxi formations laboratory simulation of maturation was used to determine the relationship between graptolite reflectance and vitrinite reflectance the organic constituents in the wufeng longmaxi formations are mainly composed of graptolites and solid bitumen granular and non granular graptolites were observed in the wufeng longmaxi formations with non granular as the most common texture solid bitumen can be distinguished from non granular graptolites by its coarse surface weaker anisotropy and lower random reflectance the combination of non polarized and polarized light is very helpful to distinguish solid bitumen from graptolite for comparison organic material from the early ordovician alum shale formation of sweden and estonia was also studied the macerals of the alum shales are mainly composed of lamalginites mineral bituminous groundmasses graptolites and solid bitumen the major textures of the graptolites in the sweden and estonia sediments are non granular and granular respectively both non granular graptolite and vitrinite reflectances display a systematic increase with the increase of heating temperature and time the granular graptolites in the estonian sample were gradually changed to non granular graptolites following laboratory simulated maturation indicating that granular graptolites can transform into non granular graptolites with maturation solid bitumen in the wufeng longmaxi formations was derived from the solid residue of kerogen and or post oil bitumen the graptolite random reflectance is a better thermal maturity indicator than graptolite maximum reflectance and is more precise due to the smaller standard deviation several equations are proposed to determine the thermal maturity of the graptolite bearing sediments based on graptolite random reflectance graptolite maximum reflectance and solid bitumen random reflectance

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

geochemical constraints on the origin and volume of gas in the new albany shale devonian mississippian eastern illinois basin this study involved analyses of kerogen petrography gas desorption geochemistry microporosity and mesoporosity of the new albany shale devonian mississippian in the eastern part of the illinois basin specifically detailed core analysis from two locations one in owen county indiana and one in pike county indiana has been conducted the gas content in the locations studied was primarily dependent on total organic carbon content and the micropore volume of the shales gas origin was assessed using stable isotope geochemistry measured and modeled vitrinite reflectance values were compared depth of burial and formation water salinity dictated different dominant origins of the gas in place in the two locations studied in detail the shallower owen county location 415 433 m 1362 1421 ft deep contained significant additions of microbial methane whereas the pike county location 832 860 m 2730 2822 ft deep was characterized exclusively by thermogenic gas despite differences in the gas origin the total gas in both locations was similar reaching up to 2 1 cm3 g 66 scf ton lower thermogenic gas content in the shallower location lower maturity and higher loss of gas related to uplift and leakage via relaxed fractures was compensated for by the additional generation of microbial methane which was stimulated by an influx of glacial melt water inducing brine dilution and microbial inoculation the characteristics of the shale of the maquoketa group ordovician in the pike county location are briefly discussed to provide a comparison to the new albany shale

the organic petrology of graptolites and maturity assessment of the wufeng longmaxi formations from chongqing china insights from reflectance cross plot analysis abstract the wufeng longmaxi formations ordovician silurian contain abundant graptolite bearing shales which have proven to be one of the most successful shale gas exploration targets in china and can provide an opportunity to study the organic petrology of graptolites organic petrology analysis has been conducted on these organic rich shales in order to depict the shape of graptolite reflectance indicating surface gris and their organic maturity granular and non granular graptolites have been observed in the studied sediments and non granular graptolites were the major graptolite species the strong positive correlation between the maximum reflectance rmax and bireflectance of graptolites indicates that the graptolites display stronger anisotropy with maturation a linear coalification path of graptolite fragments was observed in the studied sediments a remarkable decrease in the minimum reflectance rmin values of graptolites was observed when rmax exceeds 6 the samples with lower thermal maturity rmax 2 tend to be biaxial neutral whereas higher rank samples display biaxial negative characteristics the gris shape becomes more oblate with maturation the wufeng longmaxi shales from the southeastern chongqing and wuxi areas of the chongqing municipality china are post mature and in the dry gas zone whereas samples from the chengkou area of the chongqing municipality china are still in the oil window their different burial and thermal histories controlled their thermal maturity

breakup between australia and antarctica a brief review in the light of new data abstract the arguments justifying the revised timing of breakup between australia and antarctica cande and mutter 1982 and the reconstruction of broken ridge and kerguelen plateau mutter and cande 1983 are reviewed and considered with respect to new subsidence data the age of breakup was revised from anomaly 22 time 55 my b p to anomaly 34 time 85 my b p the rough topography of the diamantina zone can be attributed to very slow spreading 5 mm yr beginning between the times of anomaly 34 and anomaly 19 the reconstruction of broken ridge and kerguelen plateau at anomaly 34 time shows overlap of these two features but the overlap problem is nearly resolved by anomaly 18 time 42 my b p normal seafloor spreading rates 22 mm yr commenced at anomaly 19 time 43 my b p subsidence patterns calculated from biostratigraphic data from wells drilled along australia s southern margin are interpreted as more consistent with the revised age of australia antarctic breakup subsidence curves systematically show rapid subsidence associated with the rift phase of margin development followed by much slower thermally controlled subsidence during the drift phase the timing of the rift to drift transition is believed to coincide with the age of breakup 60 to 110 my b p in addition the subsidence curves indicate a west to east propagation of breakup along the southern margin magnetic anomaly patterns and stratigraphie observations are consistent with this hypothesis

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

pliocene paleoclimatic interpretation of dsdp site 580 nw pacific using diatoms abstract high resolution quantitative diatom data are tabulated for the early part of the late pliocene 3 25 to 2 08 ma at dsdp site 580 in the northwestern pacific sample spacing averages 11 k y between 3 1 and 2 8 ma but increases to 14 to 19 k y prior to 3 1 ma and after 2 8 ma q mode factor analysis of the middle pliocene assemblage reveals four factors which explain 92 4 of the total variance of the 47 samples studied between 3 25 and 2 55 ma three of the factors are closely related to modern subarctic transitional and subtropical elements while the fourth factor which is dominated bycoscinodiscus marginatus and the extinct pliocene speciesneodenticula kamtschatica appears to correspond to a middle pliocene precursor of the subarctic water mass knowledge of the modern and generalized pliocene paleoclimatic relationships of various diatom taxa is used to generate a paleoclimate curve twt based on the ratio of warm water subtropical to cold water diatoms with warm water transitional taxa thalassionema nitzschioides thalassiosira oestrupii andcoscinodiscus radiatus factored into the equation at an intermediate 0 5 value the twt ratios at more southerly dsdp sites 579 and 578 are consistently higher warmer than those at site 580 throughout the pliocene suggesting the validity of the ratio as a paleoclimatic index diatom paleoclimatic data reveal a middle pliocene 3 1 to 3 0 ma warm interval at site 580 during which paleotemperatures may have exceeded maximum holocene values by 3 5 5 c at least three times this middle pliocene warm interval is also recognized by planktic foraminifers in the north atlantic and it appears to correspond with generalized depleted oxygen isotope values suggesting polar warming the diatom twt curve for site 580 compares fairly well with radiolarian and silicoflagellate paleoclimatic curves for site 580 planktic foraminiferal sea surface temperature estimates for the north atlantic and benthic oxygen isotope curves for late pliocene although higher resolution studies on paired samples are required to test the correspondence of these various paleoclimatic indices

pliocene shallow water paleoceanography of the north atlantic ocean based on marine ostracodes abstract middle pliocene marine ostracodes from coastal and shelf deposits of north and central america and iceland were studied to reconstruct paleotemperatures of shelf waters bordering portions of the western boundary current system including the gulf loop current florida current gulf stream and north atlantic drift factor analytic transfer functions provided pliocene august and february bottom water temperatures of eight regions from the tropics to the subfrigid the results indicate 1 meridional temperature gradients in the western north atlantic were less steep during the pliocene than either today or during late pleistocene isotope stage 5e 2 tropical and subtropical shelf waters during the middle pliocene were as warm as or slightly cooler than today 3 slightly cooler water was on the outer shelf off the southeastern and mid atlantic coast of the u s possibly due to summer upwelling of gulf stream water 4 the shelf north of cape hatteras north carolina may have been influenced by warm water incursions from the western edge of the gulf stream especially in summer 5 the northeast branch of the north atlantic drift brought warm water to northern iceland between 4 and 3 ma evidence from the iceland record indicates that cold east greenland current water did not affect coastal iceland between 4 and 3 ma 6 middle pliocene north atlantic circulation may have been intensified transporting more heat from the tropics to the arctic than it does today

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

tulelake california the last 3 million years abstract the tulelake basin formed by east west extension and faulting during the past several million years contains at least 550 m of lacustrine sediment interdisciplinary studies of a 334 m long cored section from the town of tulelake california near the center of the basin document a 3 m y record of environmental changes the core consists of a thick sequence of diatomaceous clayey silty and marly lacustrine sediments interbedded with numerous tephra layers paleomagnetic study puts the base of the core at about 3 0 ma twelve widespread silicic tephra units provide correlations with other areas and complement age control provided by magnetostratigraphy mafic and silicic tephra units erupted from local sources are also common in the core widespread tephra units include the llao rock pumice tsoyawata 7 ka the trego hot springs bed 23 ka and the rockland 0 40 ma lava creek 0 62 ma and rio dell 1 5 ma ash beds as well as several ash beds also found at summer lake oregon and an ash bed originally recognized in dsdp hole 173 in the northeastern pacific several tephra layers found in the core also occur in lacustrine beds exposed around the margins of the basin and elsewhere in the ancestral lacustrine system diatoms are present throughout the section pollen is present in most of the section but some barren zones are found in the interval between 50 and 140 m the greatest change in behavior of the pollen record takes place just above the top of the olduvai normal polarity subchronozone ostracodes are present only in high carbonate 10 caco3 intervals evolutionary changes are found in the diatom and ostracode records bulk geochemical analyses show significant changes in elemental composition of the sediment through time

north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles variations in the ratio of magnesium to calcium mg ca in fossil ostracodes from deep sea drilling project site 607 in the deep north atlantic show that the change in bottom water temperature during late pliocene 41 000 year obliquity cycles averaged 1 5 c between 3 2 and 2 8 million years ago ma and increased to 2 3 c between 2 8 and 2 3 ma coincidentally with the intensification of northern hemisphere glaciation during the last two 100 000 year glacial to interglacial climatic cycles of the quaternary bottom water temperatures changed by 4 5 c these results show that glacial deepwater cooling has intensified since 3 2 ma most likely as the result of progressively diminished deepwater production in the north atlantic and of the greater influence of antarctic bottom water in the north atlantic during glacial periods the ostracode mg ca data also allow the direct determination of the temperature component of the benthic foraminiferal oxygen isotope record from site 607 as well as derivation of a hypothetical sea level curve for the late pliocene and late quaternary the effects of dissolution on the mg ca ratios of ostracode shells appear to have been minimal

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

fractal characteristics of upper cretaceous lacustrine shale from the songliao basin ne china abstract to improve our understanding of the characteristics of nanopores and their influence on liquid hydrocarbon occurrences in lacustrine shale we carried out fractal analysis on 21 lacustrine shale cores from the upper cretaceous qingshankou formation k2qn in the songliao basin ne northeast china using toc total organic carbon and rock eval analysis xrd x ray diffraction low pressure nitrogen adsorption experiments and the fhh frenkel halsey hill method the relationships between composition of lacustrine shale toc minerals oil content the pore structure parameters bet surface area pore volume pore average diameter and the fractal dimensions were investigated two fractal dimensions d1 and d2 at relative pressures of 0 5 1 and 0 0 5 respectively were obtained with d1 ranging from 2 5055 to 2 8888 and d2 between 2 1026 and 2 733 d1 is greater than d2 indicating that small pores are more homogeneous than larger pores both d1 and d2 increase with increasing bet surface areas and total pore volumes and increase with decreasing average pore diameters the fractal dimensions of lacustrine shale are negatively correlated with the clay content but show no obvious relationship with the quartz content the relationship between fractal dimensions both d1 and d2 and toc content is a u shaped curve with minimum d values at 2 5 3 wt toc fractal dimension d1 can be used to characterize the shale oil content and lacustrine shale samples with a lower fractal dimension have greater free oil therefore considering the influence of toc content on fractal dimension and the relationship between oil content and fractal dimension we conclude that lacustrine shale in the oil generation stage with 2 5 3 0 wt toc is probably the preferred shale oil exploration target in the songliao basin the results indicate that fractal analysis leads to a better understanding of the pore structure and oil storage capacity of lacustrine shale

flow through extraction of oil and gas shales under controlled stress using organic solvents implications for organic matter related porosity and permeability changes with thermal maturity abstract four core plugs from the lower jurassic posidonia shale of the hils syncline in northern germany have been subjected to flow through extraction tests with dichloromethane dcm under controlled stress conditions in a tri axial flow cell the samples represent a maturity sequence from 0 53 to 1 45 vrr the bitumen sequentially extracted from the natural pore space of the shale plugs was analyzed for its geochemical composition changes in rock matrix density porosity and permeability resulting from the removal of soluble organic matter were determined the relative porosity increase of the plugs after extraction ranged from 6 to 13 and correlated with the extract yield klinkenberg corrected permeability coefficients measured with helium increased by a factor of 17 0 for the immature early mature sample and 26 6 for the overmature sample petrographical investigations after extraction indicate that fluid flow occurred predominantly parallel to bedding as evidenced by open fractures and fractures bearing residues that apparently precipitated from the dcm solution compositional variations of the extracts over time are interpreted in terms of the organic geochemical inventory of bitumen associated with the natural pore system and its accessibility at different maturity levels these patterns deviate strongly from the bulk rock extracts of the powdered samples

palaeoenvironmental conditions during deposition of the upper cretaceous oil shale sequences in the songliao basin ne china implications from geochemical analysis abstract excellent hydrocarbon source rocks oil shales containing type i organic matter om were deposited in the continental songliao rift basin during the late cretaceous a major contribution of aquatic organisms dinoflagellates green algae botryococcus and minor input from macrophytes and land plants to om accumulation is indicated by n alkane distribution steroid composition and 13 c values of individual biomarkers microbial communities included heterotrophic bacteria cyanobacteria and chemoautotrophic bacteria as well as purple and green sulfur bacteria the presence of methanotrophic bacteria is indicated by 13 c depleted methyl hopane the sediments were deposited in a eutrophic alkaline palaeolake highly reducing saline bottom water conditions and a stratified water column existed during om accumulation of the qingshankou formation and member 1 of the nenjiang formation this is indicated by low pristane phytane gammacerane index and mttc ratios and the presence of carotane and aryl isoprenoids however an abrupt change in environmental conditions during deposition of member 2 of the nenjiang formation is indicated by significant changes in salinity and redox sensitive biomarker ratios a freshwater environment and suboxic conditions in the deep water prevailed during this period higher input of terrigenous om occurred during deposition of the upper nenjiang formation good oil to source rock correlation was obtained using biomarker fingerprints of oil stained sandstone from the quantou formation and oil shales from the qingshankou formation based on the extent of isomerisation of c 31 hopanes the oil was most probably derived from oil shales of the qingshankou formation in deeper parts of the basin

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

middle pliocene sea surface temperatures a global reconstruction identification and analyses of pliocene marine microfossils from 64 globally distributed stratigraphic sequences have been used to produce a middle pliocene sea surface temperature reconstruction of the earth this reconstruction shows little or no change from current conditions in low latitude regions and significant warming of the ocean surface at mid and higher latitudes of both hemispheres this pattern of warming is consistent with terrestrial records and suggests a combination of enhanced meridional ocean heat transport and enhanced greenhouse effect were responsible for the middle pliocene warmth

enhanced circulation during a warm period the early pliocene is the most recent interval in which equilibrium oceanic conditions can be studied in the context of global warmth relative to today to characterize thermohaline circulation during this warm period 4 4 3 1 ma we combined new benthic foraminiferal isotopic data from the southeast atlantic with published data and reconstructed pacific and atlantic ocean nutrient distributions the data indicate enhanced ventilation of the deep atlantic and intermediate pacific during the early pliocene enhanced ventilation implies that delivery of surface water to high latitudes in western boundary currents of north pacific and atlantic subtropical gyres was probably also enhanced future modeling of this warm period needs to reconcile reduced meridional surface temperature gradients with enhanced subtropical gyre and thermohaline circulation

pore structure evolution of lacustrine shales containing type i organic matter from the upper cretaceous qingshankou formation songliao basin china a study of artificial samples from hydrous pyrolysis experiments abstract to characterize the pore evolution of lacustrine shales containing type i organic matter we performed hydrous pyrolysis experiments on a lacustrine shale sample to make it reach various maturities the samples with various maturities were then extracted using dichloromethane total organic carbon content rock eval pyrolysis and low pressure gas co2 and n2 adsorption analyses were performed on the samples before and after extraction the results showed that the volumes and surface areas of micropores

a benthic foraminiferal record of middle to late pliocene 3 15 2 85 ma deep water change in the north atlantic abstract records of benthic foraminifera from north atlantic dsdp site 607 and hole 610a indicate changes in deep water conditions through the middle to late pliocene 3 15 to 2 85 ma quantitative analyses of modern associations in the north atlantic indicate that seven species fontbotia wuellerstorfi cibicidoides kullenbergi uvigerina peregrina nuttallides umboniferus melonis pompilioides globocassidulina subglobosa and epistominella exigua are useful for paleoenvironmental interpretation the western north atlantic basin site 607 was occupied by north atlantic deep water nadw until 2 88 ma at that time n umboniferus increased indicating an influx of southern ocean water sow the eastern north atlantic basin hole 610a was occupied by a relatively warm water mass possibly northeastern atlantic deep water neadw through 2 94 ma when sow more strongly influenced the site these interpretations are consistent with benthic 18o and 13c records from 607 and 610a raymo et al 1992 the results presented in this paper suggest that the north atlantic was strongly influenced by northern component deep water circulation until 2 90 2 95 ma after that there was a transition toward a glacially driven north atlantic circulation more strongly influenced by sow associated with the onset of northern hemisphere glaciation the circulation change follows the last significant sst and atmospheric warming prior to 2 6 ma

late cenozoic history of the polar north atlantic results from ocean drilling abstract dsdp odp drilling in the northern north atlantic reveals that so far the onset of northern hemisphere cooling deduced from the occurrence of ice rafted debris ird in deep sea sediments can be traced back to the middle miocene the greenland ice sheet has probably the longest history on the northern hemisphere leg 151 site 909 fram strait recovered a unique continuous sediment record dating from early middle miocene the composition of the coarse fraction indicates that the oldest ird pulses are documented around 14 ma in the fram strait site 909 and around 12 6 ma on the voring plateau leg 104 site 642 in the norwegian greenland sea fram strait site 909 indicates a further stepwise increase of northern hemisphere cooling by serveral ird pulses during late miocene between 10 8 and 8 6 ma around 7 2 6 8 and 6 3 ma which ultimately led to a drastic intensification of northern hemisphere glaciation during plio pleistocene the deep sea sediment records show that plio pleistocene strengthening of ird pulses have been observed since approximately 4 0 ma in the westernmost norwegian greenland sea and labrador sea by contrast strengthening of ird pulses are observed at approximately 3 2 2 7 ma on the eastern side of the norwegian greenland sea including the barents sea margin sediment composition and physical properties of the drilled mostly terrigenous sections reveal that orbital parameters have controlled major aspects of shallow and deep water environments with frequency domains related to 41 ka periods of obliquity dominant in the pre glacial miocene pliocene and early quaternary and to 100 ka periods of eccentricity dominant during the past 600 000 700 000 years the stratigraphy of ice rafted material reveals a frequently and rapidly changing history of the dynamics of various segments in ice sheets around the norwegian greenland sea it is particularly evident from the composition of the ice rafted material that the eurasian ice sheets delivered ird to the eastern part of the norwegian greenland sea whereas greenland source areas are represented in the drill sites of the east greenland continental margin and in the labrador sea the stratigraphic sequences on the yermak plateau suggest that the svalbard ice sheet may have extended far to the north prior to oxygen isope stage 16 but not since then invasions of temperate atlantic waters during interglacials can be observed as short lived and rather irregular events it never reached the area off eastern greenland except during the pliocene interval when tundra floras were able to develop on north eastern greenland and planktonic foraminifers suggesting the presence of temperate water masses in the fram strait as been documented in the drill sites from the yermak plateau

geochemical controls on shale microstructure the uptick in hydrocarbon production from shale in the united states has generated interest in metrics of unconventional reservoir quality like permeability we use conventional gas sorption to characterize shale microstructure which provides insight on the features that govern mass transport the gas sorption data are analyzed to determine the surface area a s m2 g and pore volume v p cm3 g of 30 samples from basins across north america with this information we quantify the effect of composition and thermal maturity on shale microstructure in particular we find that the specific surface area of the organic component evolves from 50 m2 g total organic carbon toc in immature shale to 500 m2 g toc for regions that produce dry gas the increase in a s is accompanied by an increase in v p and concomitant decline in average pore size e g r h 4 v p a s we contend that the latter is due to the development of nanometer sized pores in kerogen as it is converted to mobile hydrocarbon which is ultimately expelled this hypothesis is supported by similar measurements on companion samples after bitumen extraction or combustion which underscore the intimate spatial association of petroleum and kerogen coupled with information on accessibility to the porosity garnered by varying the particle size these results establish a clear link between organic matter thermal maturity and reservoir quality in unconventional shale systems

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

pliocene 3 2 2 4 ma ostracode faunal cycles and deep ocean circulation north atlantic ocean ostracode assemblages from deep sea drilling project sites 607 western mid atlantic ridge and 610 southeast rockall plateau show rapid systematic shifts during late pliocene glacial interglacial cycles that reflect deep sea environmental change progressive decreases in north atlantic deep water taxa and increases in southern ocean taxa occur from 3 4 to 2 4 ma and high amplitude faunal cycles begin near 2 8 ma four ostracode assemblages each with a characteristic phase relative to 41 k y obliquity glacial interglacial 18 o cycles characterize the benthic faunal record at site 607 cross spectral analysis shows that the site 607 glacial assemblage has a 41 k y periodicity significant at the 95 level other assemblages show a less significant but still obvious concentration of variance at 41 k y faunal patterns suggest climatically controlled reorganization of deep sea benthic communities during glacial interglacial cycles due to oscillating deep sea environments

high resolution geochemical analysis of organic matter accumulation in the qingshankou formation upper cretaceous songliao basin ne china abstract in the well known continental songliao basin the oil shale successions of the cretaceous qingshankou formation are excellent source rocks for oil the oil shale layers with high toc total organic carbon contents developed at the bottom of the formation they are divided into the lower oil shale toc up to 18 3 and the upper oil shale layer toc up to 14 4 the oil shale layers and accompanying mudstones are investigated by high resolution analyses of drill cores by pyrolysis organic petrology organic and inorganic geochemistry the results demonstrate the predominance of type i kerogen derived from algal microbial mats i e lamalginite however increased proportions of plant derived organic matter are indicated by rock eval parameters and the presence of vitrinite in the upper oil shale as evidenced from lower concentrations of hopanes higher sinking rates of organic matter om are suggested to have been responsible for a lower extent of microbial degradation during accumulation of the lower oil shale unit the environmental conditions are characterized by anoxic saline bottom water overlain by an extended zone of freshwater favorable for om production and preservation under these preconditions oil shale thickness and quality are governed by primary productivity related to accommodation space and nutrient supply redox conditions within the water column are the key factor controlling organic matter preservation

early pliocene climate a perspective from the western equatorial atlantic warm pool high resolution 3 4 kyr planktonic stable isotope stratigraphies from site 925 drilled on ceara rise ocean drilling program leg 154 are used to investigate the role of the western equatorial atlantic sea surface hydrography in early pliocene 3 2 4 7 ma climate change oxygen isotope results from globigerinoides sacculifer a mixed layer dweller suggest that equatorial sea surface temperatures were cooler than today by 2 3 c consistent with relatively strong northward advection of heat away from the equator oxygen isotope results from neogloboquadrina dutertrei suggest that over the long term this thermocline dweller tracks global ice volume fluctuations stable isotope gradients between the two planktonic species throughout the entire interval imply a stable warm pool in the western equatorial atlantic we observe a rapid 3 4 kyr decrease in g sacculifer and the n dutertrei 18o values at 4 36 ma that may reflect a freshening of the sea surface a direct response to a southward displacement of the intertropical convergence zone and perhaps an indirect response to restricted flow through the central american seaway

astronomical solutions for paleoclimate studies over the last 3 million years three solutions numerical qtd90 semi analytical la90 and analytical ber90 for the planetary and precessional elements of the earth have recently become available they allow the computation of the fundamental astroclimatic parameters eccentricity climatic precession and obliquity the agreement between these different solutions is remarkably good reflecting their accuracy in such a way that they can be considered reliable enough for paleoclimate studies over at least 3 myr the difference between these solutions in eccentricity is less than 0 005 over this time interval while the differences in obliquity and climatic precession are larger but mainly due to phase lag between the solutions at 3 myr bp ber90 leads la90 by 6 x 10 3 yrs and qtd90 by 9 x 10 3 yrs for the obliquity and it leads la90 by 2 x 10 3 yrs and qtd90 by 4 x 10 3 yrs for the climatic precession

mid pliocene warmth stronger greenhouse and stronger conveyor abstract three million years ago prior to the onset of northern hemisphere glaciation global mean temperatures may have been as much as 3 5 c warmer than at present we present evidence based on the carbon isotopic composition of marine organic matter that atmospheric co2 levels at this time were on average only about 35 higher than the preindustrial value of 280 ppm we also present carbon isotopic evidence for stronger thermohaline circulation in the atlantic ocean during the warmest intervals and propose that the north atlantic conveyor belt may act as a positive feedback to global warming by enhancing sea ice retreat and decreasing high latitude albedo based on our results it seems unlikely that the mid pliocene warm period was a doubled co2 world

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

middle pliocene vegetation reconstructions paleoclimatic inferences and boundary conditions for climate modeling abstract the general characteristics of global vegetation during the middle pliocene warm period can be reconstructed from fossil pollen and plant megafossil data the largest differences between pliocene vegetation and that of today occurred at high latitudes in both hemispheres where warming was pronounced relative to today in the northern hemisphere coniferous forests lived in the modern tundra and polar desert regions whereas in the southern hemisphere southern beech apparently grew in coastal areas of antarctica pliocene middle latitude vegetation differed less although moister than modern conditions supported forest and woodland growth in some regions now covered by steppe or grassland pliocene tropical vegetation reflects essentially modem conditions in some regions and slightly cooler than or warmer than modern climates in other areas changes in topography induced by tectonics may be responsible for many of the climatic changes since the pliocene in both middle and lower latitudes however the overall latitudinal progression of climatic conditions on land parallels that seen in the reconstruction of middle pliocene sea surface temperatures pliocene paleovegetational data was employed to construct a 2 2 global grid of estimated mid pliocene vegetational cover for use as boundary conditions for numerical general circulation model simulations of middle pliocene climates continental outlines and topography were first modified to represent the pliocene landscape on the 2 2 grid a modern 1 1 vegetation grid was simplified and mapped on this pliocene grid and then modified following general geographic trends evident in the pliocene paleovegetation data set

impact of hydrocarbon expulsion efficiency of continental shale upon shale oil accumulations in eastern china abstract core samples were taken from two formations the qingshankou formation in northern songliao basin and the third member of the shahejie formation of zhanhua sag to carry out a study of impact of hydrocarbon expulsion from continental shale upon shale oil accumulations in eastern china total organic carbon toc and pyrolysis data of these samples were used to establish an evaluation criterion with absolute and relative oil content indexes for determining oil potential of shale as a result a correspondence relationship between shale oil content and organic types was established factors that may affect oil content of shale were discussed through study of fractures pore development minerals and lithological assemblage of the samples the results show that oil content of mature petroleum source rocks is firstly controlled by fracture growth and secondly by pore development they played both negative and positive roles in hydrocarbon flow and accumulation in shale overpressure caused by hydrocarbon generation and existence of organic acid corrosion are two important factors affecting the formation of fractures and pores in shale respectively intervals with type i organic matter are not favorable shale oil exploration targets because they contain little oil shale with type i organic matter tends to generate large amount of hydrocarbon but these hydrocarbon will escape with a high efficiency through over pressurized fractures caused by hydrocarbon generation and lack of pore space which in turn is the result of absence of oxygen that is essential for forming organic acid to create secondary pores in shale on the contrary intervals with type ii organic matters are potential shale oil exploration targets for that they offered just right conditions for oil to stay inside higher content of oxygen that is helpful in forming organic acid moderate hydrocarbon generation capacity that will not cause over pressurized fractures in shale with secondary pores while intervals with type iii organic matter bear no exploration significance due to the fact that this type of kerogen produces less oil because of low hydrocarbon generation capacity and unfavorable molecular configuration shale intervals with thin sandstone interbeds provide favorable passageways for dissolved carbonate by organic acid to flow out avoiding secondary precipitation the pores left behind can be excellent space for generated hydrocarbon to linger around these interbeds are also favorable for later reservoir stimulation measures such as hydraulic fracturing shale oil exploration shall be focused on finding sweet spots with greater pores which are the main reservoir space

pliocene pleistocene evolution of eastern tropical pacific surface water circulation and thermocline depth we evaluated the response of eastern equatorial pacific upper water column hydrography to the panama seaway closure and the initiation of large scale northern hemisphere glaciation the 18o gradient between globorotalia tumida and globigerinoides sacculifer indicates a general shoaling of the thermocline between 4 2 and 3 0 ma which may be related to a recorded decrease in southeast trade wind strength the 13c gradients suggest that surface water nutrient concentrations have increased during the last 5 myr and that upwelling intermediate waters began to change sources at 3 2 ma changes in the trans pacific east west temperature and nutrient gradients at 4 0 and 1 5 ma are coincident with the seaway closure and a major phase of northern hemisphere glaciation changes in the sensitivity of surface circulation to milankovitch forcing 18o records linearly related to orbital variations only after 3 2 ma are associated with the seaway closure pleistocene initiation of 100 and 41 kyr cycles in the thermocline depth proxy may suggest that the hydrographic response to milankovitch forcing is enhanced by air sea interactions which maintain the relatively steep pleistocene trans pacific gradients the 13c records are dominated by the 41 kyr period and are usually coherent with high latitude climate suggesting that associated changes in the global carbon reservoir dominate the tropical 13c signals

the organic matter distribution and methane capacity of the lower cretaceous strata of northeastern british columbia canada abstract the methane sorption capacity of a succession of sandstone siltstone shale and coal from the lower cretaceous fort st john group of northeastern british columbia was investigated average organic matter om content for all formations is 2 3 wt with a minimum of 0 6 wt and maximum of 10 1 wt the methane sorption capacity ranges between 0 19 and 2 74 cm3 g at 6 mpa and at 30 c total gas capacity free and sorbed gas ranges between 2 2 and 16 6 cm3 g at 6 mpa micropore volumes range between 0 43 and 1 69 cm3 100 g a positive correlation exists between the om content micropore volume and the methane capacity of shales shales with high methane capacities have either high contents of inertodetrinite or vitrinite moisture content shows a positive relationship with om content micropore volume and methane capacity the negative relationship between moisture and surface area derived from n2 adsorption suggests the moisture is located within the microporosity of the om and also explains the positive relationship between methane capacity and moisture the high inertodetrinite and vitrinite contents correlate with sea level regressions that delivered terrestrial om from coastal plains located south of the study area into the basin

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

high eustatic sea level during the middle pliocene evidence from the southeastern u s atlantic coastal plain the middle pliocene approximately 3 5 2 5 ma was a period of global warmth preceding the growth of major northern hemisphere ice sheets the authors report on eustatic sea level for the middle pliocene based on microspaleontologic study of marine deposits of the duplin formation of south carolina and north carolina the duplin was deposited during a middle pliocene marine transgression that formed the orangeburg scarp a prominent wave cut geomorphic paleoshoreline of the southeastern u s atlantic coastal plain they concluded that 1 the scarp in south carolina was formed mostly during the middle pliocene 3 5 3 0 ma 2 eustatic sea level was about 35 plus minus 18 m higher than modern sea level the scarp has been uplifted about 50 65 m since the middle pliocene and 3 ocean water temperatures along eastern north america were warmer when the scarp was formed that they are at present

magnitude of climate variability during middle pliocene warmth a palaeoclimate modelling study abstract the nature and magnitude of climatic variability during the period of middle pliocene warmth ca 3 29 2 97 ma is poorly understood we present a suite of palaeoclimate modelling experiments incorporating an advanced atmospheric general circulation model gcm coupled to a q flux ocean model for 3 29 3 12 and 2 97 ma bp astronomical solutions for the periods in question were derived from the berger and loutre bl2 astronomical solution boundary conditions excluding sea surface temperatures ssts which were predicted by the slab ocean model were provided from the usgs prism2 2 2 digital data set the model results indicate that little annual variation 0 5 c in ssts relative to a control experiment occurred during the middle pliocene in response to the altered orbital configurations annual surface air temperatures also displayed little variation seasonally surface air temperatures displayed a trend of cooler temperatures during december january and february and warmer temperatures during june july and august this pattern is consistent with altered seasonality resulting from the prescribed orbital configurations precipitation changes follow the seasonal trend observed for surface air temperature compared to present day surface wind strength and wind stress over the north atlantic north pacific and southern ocean remained greater in each of the pliocene experiments this suggests that wind driven gyral circulation may have been consistently greater during the middle pliocene the trend of climatic variability predicted by the gcm for the middle pliocene accords with geological data however it is unclear if the model correctly simulates the magnitude of the variation this uncertainty is derived from a the relative insensitivity of the gcm to perturbation in the imposed boundary conditions b a lack of detailed time series data concerning changes to terrestrial ice cover and greenhouse gas concentrations for the middle pliocene and c difficulties in representing the effects of climatic history in snap shot gcm experiments

southeast atlantic marine and terrestrial response to middle pliocene climate change abstract analysis of planktic foraminifers and pollen from deep sea drilling project site 532 located on the continental margin of southwest africa provides information on the link between pliocene paleoceanographic conditions and paleoenvironments of southwest africa increased upwelling at site 532 correlates with southward migration of onshore vegetation regions both terrestrial and marine changes can be explained by changes in the southern hemisphere surface temperature gradient which affected the paleo position of subtropical high pressure cells and productivity of water masses during the pliocene when the subtropical high pressure cells were further south southern ocean waters were warmer contained less sea ice southern ocean diatom productivity was high and nutrient depleted water upwelled off southwest africa when the subtropical high pressure cells were in a configuration similar to the present southern ocean waters were cooler and contained more sea ice the aerial extent of southern ocean diatom productivity was limited and nutrient rich waters upwelled off southwest africa as the benguela upwelling system migrated closer to the position of site 532

modeling pliocene warmth modeling studies relevant to the question of pliocene warmth are reviewed although significant regional climate variations may be due to pliocene changes in orography and ocean circulation these changes do not appear sufficient to explain inferred globally increased warmth climate modeling studies for a doubling of co2 suggest high latitude temperature increases approximately comparable to inferred warming during the pliocene i suggest that such a co2 increase may be primarily responsible for the pliocene temperature increase downdraw of co2 since the pliocene is consistent with some geochemical indications of enhanced weathering in the pleistocene however additional proxy testing of this hypothesis is required the co2 models also predict tropical sea surface warming of 2 3 c and winter temperature warming in central eurasia 50 70 n of 4 10 c predictions that distinguish co2 from some other mechanisms enhanced scrutiny of pliocene records from the above regions may prove a valuable test of the co2 hypothesis finally although a co2 increase may be responsible for pliocene warmth this time interval should not be cited as a direct analog for a future greenhouse warming as the future climate will have a significant nonequilibrium response because of the rapid rate of change of forcing despite these limitations enhanced study of pliocene climates may be very valuable as an independent source of validation of co2 doubling simulations

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

abrupt change of pore system in lacustrine shales at oil and gas maturity during catagenesis abstract one of the biggest challenges in evaluating the transport and storage properties of shales is understanding how the pore structure and network evolve in the same stratigraphic shale during catagenesis using a combination of co2 adsorption mercury intrusion porosimetry as well as scanning electron microscopy we have described the evolution and the abrupt changes jump of pore characteristics in lacustrine shale at oil and gas maturation with an increase maturity our sample set exhibited abrupt changes in porosity related characteristics porosity and surface areas presented a decline and then an increase and a jump occurred due to hydrocarbon generation with the minimum value in late maturity i e vitrinite reflectance of 1 3 these changes were accompanied by corresponding changes in pore size distributions surface area percentage and multi scale pores volumes the trends in porosity variation were related to different organic matter and mineral contents in our samples to some extent with the degree of maturation being the dominant influence we found that inorganic pores were the main contributor to the porosity of less mature shales while porosity in gas mature shales was dominated by organic matter pores in this work we showed that organic matter transformation was a centric component of pore evolution our findings may fill significant gaps in understanding and predicting pore development with respect to the maturity of lacustrine shales

pore types in the barnett and woodford gas shales contribution to understanding gas storage and migration pathways in fine grained rocks the identification of organoporosity microscale and nanoscale pores within organic matter in shales its importance to storage and perhaps transfer of gas molecules through shales and methods for gathering three dimensional images of the pores such as by argon ion milling and or field emission scanning electron microscopy have all been well documented and discussed for unconventional gas shales however other types of pores exist within shales that can be important to storage and migration of gas and oil and other technologies are available for their identification and imaging the different pore types found in the barnett and woodford shales are described and classified in this article scanning electron microscopy revealed the presence of porous floccules in both the barnett and woodford shales which appear similar to laboratory produced floccules and to those in other ancient shales published experimental and observational studies indicate that floccules are hydraulically equivalent to coarser grains and are transported by traction processes current induced microsedimentary structures and textures within the barnett and woodford shales as well as the preserved floccules suggest such processes were active during transport and deposition pore spaces between the floccules are open and can provide storage space as well as permeability pathways for gas molecules through the shales pores are also found within organic matter that occurs both as discrete particles and as adsorbed coatings around clay grains in the shale they are referred to here as organopores porous fecal pellets are also common in the barnett shale preserved fossil fragments such as organic walled spores and inorganic sponge spicules have hollow central chambers which may remain partially or completely open even after burial intraparticle pores occur between grains of various minerals e g pyrite framboids microchannels within shale matrix which may be the bounding surfaces of scours or microsedimentary structures may also provide permeability pathways for hydrocarbon migration mircrofractures are also common and their initiation might be related to mineral crystal structure when present in sufficient quantity these pore types offer potential gas and oil molecule storage spaces and permeability pathways through the shales

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

pacific ocean intermediate and deep water circulation during the pliocene abstract new benthic foraminiferal stable isotopic records of northeast pacific intermediate water odp site 1014 1177 m and mid depth water odp site 1018 2476 m were compared to isotopic records of deep water in the tropical pacific odp site 849 3851 m for the reconstruction of vertical profiles of nutrient and physical properties from the early pliocene to the early pleistocene approx 5 1 4 ma our data indicate that for the entire interval there was enhanced north pacific intermediate water ventilation relative to today and a similar to modern circulation pattern with northward flowing pacific bottom water pbw beneath its southward flowing return flow however the core of maximally aged return flow resided as deep as 2500 m as compared to 1500 m today probably due to the strengthened intermediate water flow less apparent aging of deep water along its path before 2 7 ma indicates that thermohaline overturning may have been more rapid in the warm period of the early pliocene in addition prior to 2 7 ma foraminiferal oxygen isotopic values at mid depth sites are higher than at deep sites a reversed vertical gradient relative to today in both the atlantic and pacific oceans we suggest that nadw was warmer and more saline than today and that it influenced mid depth waters throughout the atlantic and pacific oceans enhanced pliocene formation of warmer saltier intermediate water in the north pacific and deep water in the north atlantic may have been a result of higher than modern high mid latitude sea surface temperatures evaporation and salinity

the effect of analytical particle size on gas adsorption porosimetry of shale abstract gas storage capacity and gas producibility of shale gas reservoirs are critically limited by shale porosity in spite of its importance porosimetric characterization of shale remains challenging due to highly heterogeneous structures small average pore sizes and wide pore size distributions this study utilizes low pressure n 2 and co 2 gas adsorption porosimetry to investigate the evolution of micro and mesopores in a suite of 11 new albany shale samples across a wide range of thermal maturity corresponding to vitrinite reflection r o values from 0 35 to 1 41 mesopore volumes follow a nonlinear evolutionary path starting with a maximum in immature shale sample 472 1 subsequent intermittent minima in mesopore volumes during early and late maturity are consistent with the transformation of kerogen during the early mature stage sample 554 2 and secondary cracking of bitumen oil at the late mature stage sample il2 respectively micropore volumes display a varying trend throughout thermal maturation and are significantly controlled by total organic carbon contents both meso and micropore volumes are positively correlated with clay content and tend to decrease with an increase in feldspar content a reduction in grain size of shale samples for gas adsorption porosimetry prominently enhances mesopore volumes whereas the effects on micropore volumes are variable these findings may be associated with the fact that smaller particles are able to attain complete adsorption equilibrium quickly which in turn reduces experimental artefacts during gas adsorption porosimetry crushing of shale not only alters the shape of gas adsorption hysteresis loops but also tends to tighten the openings of hysteresis loops by enhancing the connectivity of pores and reducing the likelihood of gas being trapped during desorption

role of water in hydrocarbon generation from type i kerogen in mahogany oil shale of the green river formation abstract hydrous and anhydrous closed system pyrolysis experiments were conducted on a sample of mahogany oil shale eocene green river formation containing type i kerogen to determine whether the role of water had the same effect on petroleum generation as reported for type ii kerogen in the woodford shale the experiments were conducted at 330 and 350 c for 72 h to determine the effects of water during kerogen decomposition to polar rich bitumen and subsequent bitumen decomposition to hydrocarbon rich oil the results showed that the role of water was more significant in bitumen decomposition to oil at 350 c than in kerogen decomposition to bitumen at 330 c at 350 c the hydrous experiment generated 29 more total hydrocarbon product and 33 more c 15 hydrocarbons than the anhydrous experiment this is attributed to water dissolved in the bitumen serving as a source of hydrogen to enhance thermal cracking and facilitate the expulsion of immiscible oil in the absence of water cross linking is enhanced in the confines of the rock resulting in formation of pyrobitumen and molecular hydrogen these differences are also reflected in the color and texture of the recovered rock despite confining liquid water pressure being 7 9 times greater in the hydrous experiments than the confining vapor pressure in the anhydrous experiments recovered rock from the former had a lighter color and expansion fractures parallel to the bedding fabric of the rock the absence of these open tensile fractures in the recovered rock from the anhydrous experiments indicates that water promotes net volume increase reactions like thermal cracking over net volume decrease reactions like cross linking which results in pyrobitumen the results indicate the role of water in hydrocarbon and petroleum formation from type i kerogen is significant as reported for type ii kerogen

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

controls of organic and inorganic compositions on pore structure of lacustrine shales of chang 7 member from triassic yanchang formation in the ordos basin china abstract to quantify the contributions of organic and inorganic compositions to pore volumes of chang 7 shales sub critical gas adsorption experiments were performed on a suite of shale and organic matter samples the parameters of pore structure were then calculated from the gas adsorption data the grain densities of the studied samples were also measured based on the total organic carbon toc contents and pore volumes of shale and organic matter samples the contributions of organic matter and inorganic compositions to pore volumes were estimated the results showed that the adsorbed gas volumes pore volumes surface areas and pore size distribution lines of organic matter samples were all higher than those of shale samples it indicated that organic matter was more porous than other fractions in the studied samples the average contributions of organic matter to the volumes of micropore mesopore and macropore are 45 98 27 20 and 33 27 respectively the contributions of organic matter to pore volume increased with the maturity which can be attributed to the formation of organic matter pores during maturation the contributions of organic matter to mesopore and macropore volumes correlated positively with toc content which suggested that toc content is another controlling factor of the contributions of organic matter to pore volume

a comparison of experimental methods for describing shale pore features a case study in the bohai bay basin of eastern china abstract to compare experimental methods for describing shale pore features we performed a series of parallel experiments on typical continental shales from the bohai bay basin of eastern china including scanning electronic microscopy sem focused ion beam scanning field emission scanning electron microscopy fib fe sem low temperature nitrogen adsorption desorption ltna mercury intrusion porosimetry mip and nuclear magnetic resonance nmr techniques the results show that artificial peaks located at 3 to 5 nm affected by the tensile strength effect tse are clearly seen in the bjh pore size distributions psds calculated using the low temperature nitrogen desorption curve of shale with narrow neck pores e g ink bottle pores although the ltna technique cannot completely reveal large pores the adsorption desorption curve and the psd acquired from it can still indicate the relatively high or low extent of development of large pores in different shales shale within the oil window primarily contains inorganic pores as organic nanopores are generally formed during the high or over mature stage of organic matter during the mercury intrusion high pressures forcing liquid mercury to enter small pores less than 40 to 70 nm will cause pores in the samples to crack especially for shale with slit shaped and wedge shaped pores unlike ltna mip measures only pore throats and does not detect pore bodies therefore the effective pore size revealed by the ltna method may be up to 300 nm instead of only 50 nm when ltna is combined with mip to reveal the psd of shales with narrow necked pores nmr and ltan can be complemented by each other and the psd results revealed by them are anastomotic which suggests that the combination of nmr and ltan is an ideal method for revealing the psd of shale

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