the landslide hazard in the himalayas geological control and human action abstract mountains are high energy environments characterised by instability and variability much of this instability is the result of a variety of landsliding processes mudflows rockfalls and debris slides avalanches being especially important this landsliding constitutes a major hazard in the himalayas early work has suggested that certain rock types are more predisposed to failure than others it also seems possible that specific types of failure are related to certain rock types and properties this analysis suggests that these relationships can be employed in a hazard assessment phyllite rocks are the most susceptible to landsliding followed by shales schists poorly cemented sandstones gneiss granites and quartzite this order is also appropriate for slope failures within weathered material although weathered gneiss appears to be more susceptible to rill and gully erosion clearly rock type exerts a major influence on landsliding but assessing the role of rock type in comparison to the effect of human activity is difficult human activity is often influenced by the nature of slopes including the type and depth of material on the slopes as these are affected by rock type it is difficult to differentiate the contributing factors because of this it would be dangerous to assume that landsliding in the himalayas can be completely explained and predicted by the nature of the rock type

possible pore structure deformation effects on the shale gas enrichment an example from the lower cambrian shales of the eastern upper yangtze platform south china abstract shale gas reservoir performance and canister desorption experiments of the lower cambrian organic rich shales in the eastern upper yangtze platform reveal a significant difference in shale gas content between the dabashan arc like fold thrust belt in northeastern chongqing deformed zone and the slightly folded area in southeastern chong non deformed zone integrated pore characterization methods including scanning electron microscopy sem low temperature n2 and co2 adsorption and mercury injection capillary pressure micp analyses were comparatively conducted in both areas in order to examine shale gas reservoir pore size variations and thus the possible microscopic pore structure controls on shale gas enrichment the lower cambrian shales in both deformed zone dz and non deformed zone ndz were deposited in the deep water shelf and show similar organic matter richness and thermal maturity the majority of organic matter om hosted pores in dz samples are in nanoscale size range with the dominance of micro fractures within the om or at the interface of om and minerals in contrast om hosted meso 2 50 nm to macropores 50 nm are the dominant pore types in the ndz samples om hosted micropores the dabashan arc like fold thrust belt took place by the end of the late triassic while the lower cambrian shales have reached thermal maturity peak om hosted meso 2 50 nm to macropores 50 nm in dz samples are most probably collapsed during structural deformation related to tectonic compression while micropores due to their smaller size survived the tectonic stress the om hosted micropores are the main storage space for adsorbed gas in the dz area the dominance of micro pores in dz and lack of connection between those pores and matrix pores led to higher gas content in dz samples on the contrary the well connected om hosted pore network in ndz allows easier gas flow in the rock matrix that eventually led to significant gas leakage during uplift and exhumation and lower gas content in this zone the results of this study suggest that structural deformation can potentially change the pore structure of shales and thus shale gas content which has major significance for shale gas exploration and development in south china where had experienced complex tectonic movements

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

the characteristics and formation mechanism of a regional fault in shale strata insights from the middle upper yangtze china abstract shale is a type of fracture prone rock but few regional faults are observed in shale strata here we investigate a regional detachment fault in the middle upper yangtze muy to understand the formation mechanism of a special regional fault in shale strata based on a lithological mineralogical and mechanical study as well as semi quantitative model of displacement we found that the formation of this detachment fault is closely related to the lithological association and flexural slip processes the lithological association of this detachment fault is characterized by two thick competent layers separated by a thin weak interlayer at both the macroscopic and microscopic scales when these layers are folded the detachment fault zone is commonly present in a thin weak interlayer namely the wufeng formation at the macroscopic scale and primarily along interfaces in laminar siliceous shales lss and secondarily in k bentonite interlayers within the lss at the microscopic scale the regional fault zone is characterized by parallel to strata surfaces and abrupt contacts with the protolith the fabric of the fault core is obviously controlled by the flexural slip intensity and the number of slip events as well as their direction and structural position the natural shale gas obtained from well hd 1 has proven that this regional detachment fault in shale strata is not only a migration pathway for hydrocarbons but also acts as an adsorption state reservoir for free gas from other areas this regional detachment fault in shale strata is likely to advance the shale gas industry and to expand the exploration of conventional gas

evaluation of possible gas microseepage mechanisms petroleum microseepage anomalies over petroleum accumulations are commonly explained by rapid vertical migration of colloidal gas bubbles through fracture networks this article is a theoretical anal ysis of this mechanism and of continuous gas phase flow in frac tures the gas bubble ascent mechanism is much slower than re ported microseepage velocities so it cannot account for observed microseepage in contrast continuous gas phase flow through frac tures can equal or exceed reported microseepage velocity while maintaining total flux low enough so that petroleum accumulations can exist for geological lengths of time fracture entry pressure for bubbles is more than twice that of a continuous gas phase so con tinuous gas phase migration also requires a lower pressure threshold before initiating seepage vertical microseepage is therefore best explained by the same mechanism interpreted for macroseepage although this article provides a theoretically justified mecha nism for microseepage it also shows why interpretation of surface microseepage signals is problematic fracture geometry controls seepage velocity and flux so geochemical anomalies may indicate an increase in fracture aperture as well as possible subsurface ac cumulations larger fractures require very low gas capillary entry pressures so in some settings surface seepage could result from fractures over stratal migration pathways as well as over petroleum accumulations

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

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

landslide susceptibility analysis using gis and artificial neural network the purpose of this study is to develop landslide susceptibility analysis techniques using an arti cial neural network and to apply the newly developed techniques to the study area of yongin in korea landslide locations were identi ed in the study area from interpretation of aerial photographs eld survey data and a spatial database of the topography soil type and timber cover the landslide related factors slope curvature soil texture soil drainage soil effective thickness timber age and timber diameter were extracted from the spatial database using those factors landslide susceptibility was analysed by arti cial neural network methods the landslide susceptibility index was calculated by the back propagation method which is a type of arti cial neural network method and the susceptibility map was made with a geographic information system gis program the results of the landslide susceptibility analysis were veri ed using landslide location data the validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location a gis was used to ef ciently analyse the vast amount of data and an arti cial neural network to be an effective tool to maintain precision and accuracy the results can be used to reduce hazards associated with landslides and to plan land use and construction copyright 2003 john wiley sons ltd

pore structure of the graptolite derived om in the longmaxi shale southeastern upper yangtze region china abstract the lower silurian longmaxi shale in the southeastern upper yangtze region which has been the main target for shale gas exploration and production in china is black marine organic rich shale and rich in graptolites graptolites usually only periderms preserved in shales are important organic component of the longmaxi shale however the pore structure of graptolite periderms and its contribution to gas storage has not yet been studied before a combination of optical microscopy for identification and mark of graptolite and scanning electron microscope sem for pore observations were conducted for the longamxi shale samples results show that pores are anisotropic developed in the longmaxi graptolite periderms and greatly associated with their fine structure micrometer sized fractures and spindle shaped pores between cortical fibrils in the cortical bandage are greatly developed at section parallel to the bedding while they are rare at section perpendicular to the bedding besides numerous sapropel detritus rich in nanometer sized pores are discretely distributed in the shale though graptolite periderms are low porosity from sem image analysis microfractures and elongated pores along the graptolite periderm wall may still make the graptolite an interconnected system together with the discrete porous sapropel detritus in shale these graptolite derived organic matter om may form an interconnected organic pore system in the shale the difference of pore development observed in graptolite periderms and sapropel detritus also give us new insight for the organic pore heterogeneity study the om composition their fine structure and orientation in the rock may be important factors controlling om pore development the combination of identifying om type under optical microscopy and pores observation under sem for may be an effective method to study the om pore development especially in shale that contain more om

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

gis based susceptibility mapping of karst depression in gypsum a case study from sivas basin turkey a method is presented for mapping of collapse susceptibility using geographical information system gis collapses in karst terrains are very serious geological hazards and can damage engineering structures and cause groundwater contamination preparation of collapse susceptibility maps will serve to successful urban planning in karst terrains susceptibility of collapses and the effects of collapse related factors such as geological and hydrological lithology tectonic activity drainage systems springs topographical slope angle slope aspect elevation land use distance from roads and settlement areas and vegetation cover were evaluated using gis field observations and remote sensing data of landsat thematic mapper tm satellite images a susceptibility map was constructed using the frequency ratio techniques as a result all factors had a relatively positive effect on the susceptibility map in the study area the validation of the susceptibility map was checked by considering actual collapses for this purpose degree of fit df was calculated and the values obtained indicated the high quality of map

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

analyzing the evolution of the tessina landslide using aerial photographs and digital elevation models abstract evolution of the tessina landslide near belluno italy from 1954 to the present situation has been documented using multitemporal landslide maps the maps were produced through the interpretation of sequential aerial photographs and direct field mapping of the landslide in 1998 and 1999 the interpretations were converted to large scale multitemporal topographical maps and digitized resulting in detailed geomorphological maps of the tessina landslide for the following periods 1954 1961 1969 1980 1991 1993 1998 and 1999 a quantitative volumetric analysis was also carried out using a series of digital elevation models derived from the available 1 5000 scale digital contour maps with 5 m contour interval for 1948 1964 1980 1991 and 1993 the total volume of material removed and accumulated was calculated for the entire tessina landslide for the different time steps available results indicate that the tessina landslide existed prior to its main reactivation in 1960 after which the landslide reduced in activity from 1991 however very large reactivations have taken place and the landslide continues to be active although the landslide has reached the lateral boundaries of the old pre 1960 landslide it is now expanding upslope where it may still mobilize large amounts of material

use of an artificial neural network for analysis of the susceptibility to landslides at boun korea the purpose of this study was to develop landslide susceptibility analysis techniques using artificial neural networks and to apply the resulting techniques to the study area of boun in korea landslide locations were identified in the study area from interpretation of aerial photographs and field survey data a spatial database of the topography soil type timber cover geology and land cover was constructed and the landslide related factors were extracted from the spatial database using these factors the susceptibility to landslides was analyzed by artificial neural network methods the results of the landslide susceptibility maps were compared and verified using known landslide locations at another area yongin in korea a geographic information system gis was used to analyze efficiently the vast amount of data and an artificial neural network turned out to be an effective tool to analyze the landslide susceptibility

statistical models for slope instability classification abstract statistical models for reliable hazard assessment of landslides in a given area are presented the models are based on information theory and regression analysis information theory is a branch of probability in which the most significant feature is unpredictability and regression analysis is based on simple statistical theory both methods of statistical prediction have been applied to slope instability to provide cross validation of the results a fortran 77 program for computer aided assessment of the landslide hazard has been developed the program considers the factors affecting the slope instability and history of past landslides of the area as its input the program also calculates the information and regression value in a given area and classifies the area into different grades of instability a case study of landslide hazard assessment of a 66 km2 area in parts of the alkananda valley the gharwal himalaya is presented the factors considered in the analysis are angle and height of the slope rock type and geological structures such as faults and thrusts the results obtained are illustrated in the form of landslide hazard maps the predicted results are compared by the above methods

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

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

pore characteristics differences between clay rich and clay poor shales of the lower cambrian niutitang formation in the northern guizhou area and insights into shale gas storage mechanisms abstract to study organic matter and pore characteristics of the lower cambrian niutitang organic rich shales 166 shale samples from the niutitang formation were collected from the studied well drilled in kaiyang county in the northern guizhou area upper yangtze region all of the 166 shale cores were analysed for total organic carbon toc total sulfur ts and the stable carbon isotope of kerogen 13 c org shale samples with varying toc values were chosen for mineral composition analysis helium porosity measurement and low pressure nitrogen adsorption measurement the lower cambrian niutitang formation features high organic matter content type i oil prone organic matter ultra thick organic rich shales and an abundance of brittle minerals exhibiting favourable characteristics for the lower cambrian shale gas exploration in the upper yangtze region helium porosity measurement and low pressure nitrogen adsorption measurements were performed on selected shale samples with varying toc content in order to analyse and characterize pore characteristics significant differences in mineral composition and pore characteristics were found between clay rich and clay poor niutitang shales quartz weakly correlated with toc content in clay rich shales which contained minor biogenically contributed quartz and performed better in terms of reservoir properties than clay poor shales and exhibited higher porosity maximum nitrogen quantity adsorbed pore volume and specific surface area in clay rich shales the maximum nitrogen quantity adsorbed total pore volume and specific surface area positively correlated with toc content r 2 0 77 0 79 and 0 75 respectively the pore volume of clay rich shales was dominated by mesopores and both micropore and mesopore volume of clay rich shales correlated significantly with toc content in clay poor shales quartz positively correlated with toc content indicating biogenic contribution to quartz micropore volume and mesopore volume of clay poor shales were weakly positively correlated with toc content pore volume especially mesopore volume may be affected by the recrystallization of biogenic silica exhibiting identical micropore volume with clay rich shales but lower mesopore volume

landslide susceptibility maps comparing frequency ratio and artificial neural networks a case study from the nepal himalaya this study considers landslide susceptibility mapping by means of frequency ratio and artificial neural network approaches using geographic information system gis techniques as a basic analysis tool the selected study area was that of the panchthar district nepal gis was used for the management and manipulation of spatial data landslide locations were identified from field survey and aerial photographic interpretation was used for location of lineaments ten factors in total are related to the occurrence of landslides based on the same set of factors landslide susceptibility maps were produced from frequency ratio and neural network models and were then compared and evaluated the weights of each factor were determined using the back propagation training method landslide susceptibility maps were produced from frequency ratio and neural network models and they were then compared by means of their checking the landslide location data were used for checking the results with the landslide susceptibility maps the accuracy of the landslide susceptibility maps produced by the frequency ratio and neural networks is 82 21 and 78 25 respectively

mapping landslide hazards in forest watersheds a physically realistic methodology is presented for estimating and mapping landslide hazards for watersheds this methodology also considers the variability of the controlling factors a demonstration of this methodology on an area in southeast alaska is described

a comparison of the gis based landslide susceptibility assessment methods multivariate versus bivariate the purpose of this study is to evaluate and to compare the results of multivariate logical regression and bivariate landslide susceptibility methods in geographical information system gis based landslide susceptibility assessment procedures in order to achieve this goal the asarsuyu catchment in nw turkey was selected as a test zone because of its well known landslide occurrences interfering with the e 5 highway mountain pass

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

mesozoic sedimentary evolution of the northwest sichuan basin implication for continued clockwise rotation of the south china block we present new sedimentary data integrated into a regional mesozoic stratigraphic framework to provide a detailed picture of spatio temporal variations in deposition and depocenter migration of the northwest sichuan basin the mesozoic sedimentary evolution is utilized to interpret basin subsidence history and to unravel coeval basin margin tectonics the northwest sichuan basin together with the songpan ganzi terrane behaved as a passive margin south of the qinling paleo tethys from late paleozoic to early middle triassic times and then evolved into a peripheral foreland basin in response to collision of the north and south china blocks since the late middle triassic coeval with strong north south contraction of the songpan ganzi terrane in the late triassic sinistral transpressional deformation of the longmen shan belt led to flexural subsidence of the adjacent western sichuan basin renewed basin margin fold thrust activity triggered recurrence of flexural subsidence of the northwest sichuan basin since the middle jurassic with the depocenter eventually shifting to the northwestern corner of the basin in the early cretaceous sedimentary evolution of the northwest sichuan basin and the basin margin deformation imply that the south china block had been rotating clockwise relative to the north china block throughout the mesozoic with an interim period of early jurassic tectonic quiescence a model is advanced that invokes clockwise rotation of the south china block as a driver for tectonic evolution of both the basin and adjoining structural belts and provides an explanation for several salient features that are otherwise puzzling

do all fractions of organic matter contribute equally in shale porosity a case study from upper ordovician utica shale southern quebec canada abstract in many unconventional hydrocarbon systems organic matter om substantially contributes to total porosity of the rock that led to a positive correlation between total organic carbon toc and porosity while organic porosity is an important reservoir property of unconventional hydrocarbon systems toc of these rocks consists of different macerals or petrographic fractions these toc fractions can be geochemically divided and quantified by the revised extended slow heating esh rock eval analysis this study discusses the contribution of different fractions of om on porosity variation in the mature to overmature utica shale in southern quebec using esh rock eval analysis helium pycnometery scanning electron microscopy sem and x ray diffraction xrd mineralogy selected samples from three wells at depths of 400 700 and 2000 m covering a range of thermal maturity from late peak oil window vroeqv 1 to dry gas zone vroeqv 2 1 were analyzed in this study the predominant om constituents are solid bitumen chitinozoans and minor graptolites with mean toc of 1 1 0 4 wt the mean porosity for oil and gas window samples decreases with depth from 3 9 0 9 to 2 6 0 5 respectively the sem images reveal that organic porosity is limited to pores developed in solid bitumen while regardless of thermal maturity chitinozoans have a non porous structure throughout the oil to dry gas window this observation suggests that the impact of thermal maturity on porosity is different for different om fractions i e macerals leading to different contribution of om fractions to total porosity the latter conclusion is further supported by the improved correlation observed between the solid bitumen fraction and porosity compared to toc porosity correlation for oil window samples our entire data set suggests that om i e bitumen fraction especially in the dry gas window is not the major controlling factor on the total porosity in the utica shale whereas intergranular porosity has the dominant control on total porosity this observation suggests that the hydrocarbon storage potential may largely reside in inorganic pores rather than organic pores in the analyzed intervals of the utica shale the decrease in total porosity observed from shallower samples i e oil window to deeper samples i e dry gas window also suggests that intergranular porosity is the dominant porosity component which decreases with burial

extraction of potential debris source areas by logistic regression technique a case study from barla besparmak and kapi mountains nw taurids turkey debris flow is one of the most destructive mass movements sometimes regional debris flow susceptibility or hazard assessments can be more difficult than the other mass movements determination of debris accumulation zones and debris source areas which is one of the most crucial stages in debris flow investigations can be too difficult because of morphological restrictions the main goal of the present study is to extract debris source areas by logistic regression analyses based on the data from the slopes of the barla besparmak and kapi mountains in the sw part of the taurids mountain belt of turkey where formation of debris material are clearly evident and common in this study in order to achieve this goal extensive field observations to identify the areal extent of debris source areas and debris material air photo studies to determine the debris source areas and also desk studies including geographical information system gis applications and statistical assessments were performed to justify the training data used in logistic regression analyses as representative a random sampling procedure was applied by using the results of the logistic regression analysis the debris source area probability map of the region is produced however according to the field experiences of the authors the produced map yielded over predicted results the main source of the over prediction is structural relation between the bedding planes and slope aspects on the basis of the field observations for the generation of debris the dip of the bedding planes must be taken into consideration regarding the slope face in order to eliminate this problem in this study an approach has been developed using probability distribution of the aspect values with the application of structural adjustment the final adjusted debris source area probability map is obtained for the study area the field observations revealed that the actual debris source areas in the field coincide with the areas having high probability values on this final map

geomorphological and historical data in assessing landslide hazard traditionally earth scientists assess landslide occurrence on the basis of geomorphological investigations carried out through aerial photograph interpretation and eldwork conversely local administrators primarily evaluate the impact of natural catastrophes such as landsliding on the basis of historical records and data owing to the substantial difference in the structure and spatial density of these two types of information it is dif cult to compare them directly and few investigators have attempted this we compared landslide information derived from geomorphological mapping and historical data in a pilot area the staffora river basin northern italy to do this we generated two multivariate statistical models where the dependent variable was either the mapped landslide deposits geomorphological model or the historical sites affected by landslide induced damage historical model by quantitatively comparing these two model maps we demonstrate that the geomorphological model performs better in terms of percentage of terrain units correctly predicted as stable or unstable the historical model underestimates landslide hazard mainly where human structures are lacking however it highlights slopes where landslide movements take place with a high frequency at the temporal scale of human life hence the joint use of these two models may facilitate the knowledge of the overall instability conditions of a given region and the identi cation of the landslides that are most frequently reactivated copyright 2003 john wiley sons ltd

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

probabilistic landslide susceptibility and factor effect analysis the susceptibility of landslides and the effect of landslide related factors at penang in malaysia using the geographic information system gis and remote sensing data have been evaluated landslide locations were identified in the study area from interpretation of aerial photographs and from field surveys topographical and geological data and satellite images were collected processed and constructed into a spatial database using gis and image processing the factors chosen that influence landslide occurrence were topographic slope topographic aspect topographic curvature and distance from drainage all from the topographic database lithology and distance from lineament taken from the geologic database land use from landsat thermatic mapper tm satellite images and the vegetation index value from spot hrv high resolution visible satellite images landslide hazardous areas were analyzed and mapped using the landslide occurrence factors employing the probability frequency ratio method using the all factors to assess the effect of these factors each factor was excluded from the analysis and its effect verified using the landslide location data as a result all factors had relatively positive effects except lithology on the landslide susceptibility maps in the study area

landslide susceptibility analysis and verification using the bayesian probability model the bayesian probability model using the weight of evidence method was applied to the task of evaluating landslide susceptibility using gis data the location chosen for the study was the janghung area in korea which suffered substantial landslide damage following heavy rain in 1998 using the location of the landslides as well as topographic factors such as soil forest and land use the weight of evidence method was used to calculate each factor s rating tests of conditional independence were performed for the selection of the factors allowing the large number of combinations of factors to be analyzed for each factor rating the contrast values w and w were overlaid for landslide susceptibility mapping the results of the analysis were verified using the observed landslide locations and among the combinations the slope aspect curvature soil material and wood types show the best results

carbonate porosity creation by mesogenetic dissolution reality or illusion many authors have proposed that significant volumes of porosity are created by deep burial dissolution in carbonate reservoirs we argue however that this model is unsupported by empirical data and violates important chemical constraints on mass transport because of the ubiquitous presence and rapid kinetics of dissolution of carbonate minerals the mesogenetic pore waters in sedimentary basins can be expected to be always saturated and buffered by carbonates providing little opportunity for the preservation of significantly undersaturated water chemistry during upward flow even if the initial generation of such undersaturated pore water could occur a review of the literature where this model has been advanced reveals a consistent lack of quantitative treatment in consequence the presumption of mesogenetic dissolution producing a net increase in secondary porosity should not be used in the prediction of carbonate reservoir quality

doline probability map using logistic regression and gis technology in the central ebro basin spain in the surroundings of zaragoza karstification processes are especially intense in covered karst areas where fluvial terraces lie directly on tertiary evaporites since the beginning of quaternary these processes have lead to the development of collapse and subsidence dolines with a wide range of sizes which have significant economic impacts to reduce economic impact and increase safety a regional analysis of this phenomenon is needed for spatial management therefore a probability map of dolines was developed using logistic regression and geographic information system gis techniques this paper covers the selection of input data manipulation of data using the gis technology and the use of logistic regression to generate a doline probability map the primary variable in the doline development in this area is geomorphology represented by the location of endorheic areas and different terrace levels secondary variables are the presence of irrigation and the water table gradient

pore structure characterization for the longmaxi and niutitang shales in the upper yangtze platform south china evidence from focused ion beam he ion microscopy nano computerized tomography and gas adsorption analysis abstract pore structure is of great importance in the occurrence of shale gas in this study pores in shale samples from the lower silurian longmaxi and lower cambrian niutitang shales in chongqing in the upper yangtze platform south china were examined using focused ion beam he ion microscopy fib him nano computerized tomography nano ct and gas adsorption analysis the results show that most pores in measured samples of the niutitang shale are mineral matrix pores and have poor connectivity including both intraparticle and interparticle pores organic matter pores in measured samples of the niutitang shale are rare and have small diameters in measured samples of the longmaxi shale om pores mostly macropores and large mesopores are the most abundant the nano ct results revealed that the abundance of om pores led to good pore connectivity in the longmaxi shale samples whereas the prevalence of mineral matrix pores resulted in poor connectivity in the niutitang shale samples n2 and co2 adsorption analyses showed that the mean value of micropore mesopore volumes in the niutitang and longmaxi shales samples are 0 0332 ml g and 0 0261 ml g respectively the mean values of micropores mesopores surface area in the niutitang and longmaxi shales samples are 33 84 m2 g and 32 46 m2 g respectively thus there is little difference between measured samples of the longmaxi and niutitang shales in terms of volume and surface area of micropores mesopores the equal vitrinite reflectance equal ro values of measured samples of the longmaxi shale are lower than those of the niutitang shale samples over maturity equal ro 3 resulted in a reduction of the number of pores in organic matter small pore size and poor connectivity in measured samples of the niutitang shale relatively low maturity 2

origin and characterization of eagle ford pore networks in the south texas upper cretaceous shelf abstract recent studies have shown that the loss of primary pores and the development of secondary pores in mudrocks are primarily controlled by burial diagenesis of the mineral matrix and thermal maturation of organic matter om however the lack of quantitative data on nanometer to micrometer scale rock properties has limited the ability to define and predict petrophysical properties and fluid flow in these fine grained rocks to upscale these rock properties quantitative data are needed at multiple scales representative eagle ford group samples were collected from continuous cores taken from two adjacent oil producing wells in karnes county texas to investigate small scale variations in mineralogy diagenesis and pore type point count and pore tracing methods were used to systematically quantify pore types and determine the size and shape of the identified pores the two cores from the eagle ford are dominated by modified mineral pores although secondary om pores in migrated petroleum bitumen are also important the mineral pore network includes 1 primary mineral pores originally saturated with formation water and 2 modified mineral pores containing migrated petroleum bitumen and or residual oil the om pore network includes 1 primary om pores and 2 secondary om pores including relatively large less abundant om bubble pores and relatively small more abundant om spongy pores the abundance of om spongy pores correlates positively with total organic carbon toc content and that of mineral pores weakly correlates with the volume of quartz plus feldspar studied samples have similar thermal maturities although samples from one deeper core are slightly more mature than the other except for thermal maturation the strong micrometer scale heterogeneity of rock components and properties texture fabric mineralogy and toc impacts the abundance distribution and type of pores this micrometer scale heterogeneity in porosity and pore networks would in turn significantly impact matrix permeability

solid bitumen as a determinant of reservoir quality in an unconventional tight gas siltstone play abstract in this study of the triassic montney tight gas siltstone play in the western canadian sedimentary basin petrophysical measurements of drill core samples porosity pore throat size water saturation and grain size are integrated with rock eval toc data organic petrography observations and sem imaging to show that reservoir quality in the gas window is strongly influenced by the pervasive presence of pore occluding solid bitumen and pyrobitumen at higher thermal maturity the solid bitumen formed as a pore filling liquid oil phase that was diagenetically and thermally degraded with further burial and increase in temperature the proportion of solid bitumen filling the intergranular paleopore network can be expressed as bitumen saturation and this attribute is found to be the dominant control on pore throat size and absolute permeability the samples with low bitumen saturation and large pore throat radius 0 01 m have water saturations that generally increase as pore throat size diminishes a relationship consistent with capillary theory for conventional water wet conditions the samples with high bitumen saturation and small pore throat radius

mechanics of low relief detachment folding in the bajiaochang field sichuan basin china using three dimensional 3 d seismic reflection data we apply new methods of two dimensional 2 d and 3 d structural restoration based on mechanical constraints to gain insights into the development of the bajiaochang anticline sichuan basin china this structure forms the trap for the bajiaochang field which is reported to contain substantial gas reserves within thick upper triassic delta front and lakeshore facies siliciclastics the basal detachment lies in a middle triassic evaporite unit above which layers are folded and faulted to various intensities based on their mechanical strengths the new restoration methods enable us to test a variety of fault displacement directions and to resolve that the bajiaochang structure grew primarily by dip slip and contractional folding moreover we quantify the styles and amounts of shortening within various tectonic levels of the structure large amounts of shortening and ductile thickening at the basal detachment level are consistent with general detachment fold models however we demonstrate that slip on the basal detachment is much larger than would be predicted by these models implying that substantial slip on the basal detachment extends beyond the structure into the foreland moreover structural thickening in the core of the fold is localized by a series of small ramps in the basal detachment that produce structural imbrication this implies that the bajiaochang detachment fold grew by a mechanism akin to duplexes which has important implications for the manner in which shortening and strain are partitioned within different mechanical layers of the fold

maceral controls on porosity characteristics of lithotypes of pennsylvanian high volatile bituminous coal example from the illinois basin abstract porosity characteristics of vitrain clarain durain and fusain lithotypes of the springfield coal member of the petersburg formation and the danville and hymera coal members of the dugger formation from the illinois basin were investigated with a special emphasis on the control of coal macerals on pore size distribution these pennsylvanian coals are of high volatile bituminous rank and have vitrinite reflectance ranging from 0 51 to 0 60 the lithotypes studied show decreasing values of brunauer emmett teller surface area and micro and mesopore volumes from vitrain through clarain and durain to fusain within the mesopore size range vitrain and clarain are dominated by pore size widths of 4 to 10 nm whereas durain and fusain have more volume for pores larger than 20 nm in contrast to mesopores micropore sizes are very similar for all lithotypes averaging 1 37 to 1 39 nm in addition to differences among lithotypes there are significant differences in pore characteristics among the three coals studied with largest surface areas and pore volumes documented for the hymera followed by the danville and the springfield a strong relationship exists between surface area mesoporosity and microporosity and maceral composition with vitrinite having a very strong positive correlation liptinite having a weak positive correlation and inertinite having a strong negative correlation negative correlations of total porosity with vitrinite and liptinite and positive correlations with inertinite suggest that among the maceral groups pores in inertinite contribute most to the total porosity the fourier transform infrared spectrometry technique demonstrates that fusains from the three coals studied have higher aromaticity and a higher degree of aromatic ring condensation and lower hydrocarbon potential than the other lithotypes whereas chemical differences between vitrain clarain and durain are less distinct in addition there is a relationship between aromaticity of the lithotypes and surface area and mesopore and micropore volumes

solid bitumen in the montney formation diagnostic petrographic characteristics and significance for hydrocarbon migration abstract the petrographic study of organic matter om in fine grained shale and tight rocks can be complicated by ambiguities in distinguishing primary kerogen deposited om from secondary solid bitumen migrated and solidified petroleum in this study complementary thin section field emission scanning electron microscopy fesem and organic petrology methods are used to examine core samples acquired from petroleum wells drilled into the triassic montney formation in western canada the results show that om in the medium to coarse grained siltstones of the montney tight gas and hydrocarbon liquids fairway is composed almost entirely of pore filling solid bitumen pyrobitumen here we document a range of petrographic characteristics that are diagnostic of the solid bitumen and its origin as migrated liquid petroleum these solid bitumen characteristics include 1 void filling habit 2 enclosure of earlier authigenic minerals 3 margins with smoothly curved meniscate form 4 internal flow structure 5 entrained and aligned clay minerals 6 isopachous rims along inorganic pore walls 7 globular granular aggregates and 8 fracture filling habit the petrographic results also show that the migration and flow of original oil through the thick montney formation up to 340 m was controlled at the micro scale by sedimentary ichnological diagenetic and structural features these features combined to form highly complex pathways and baffles for hydrocarbon migration petrographic recognition of om as secondary migrated solid bitumen rather than primary deposited kerogen has vital significance for assessing unconventional shale and tight hydrocarbon plays including om typing from rock eval pyrolysis interpreting depositional facies and environments and evaluating reservoir quality

pore and pore network evolution of upper cretaceous boquillas eagle ford equivalent mudrocks results from gold tube pyrolysis experiments low maturity boquillas formation eagle ford formation equivalent organic lean calcareous mudrock samples collected from outcrop were heated in gold tubes under confining pressure to investigate the evolution of organic matter om pores and mineral pores the majority of om in the boquillas samples was migrated petroleum bitumen based on evidence from geochemical analyses solvent extraction and scanning electron microscopy sem petrography the sem images showed several diagenetic events including framboidal pyrite precipitation and euhedral calcite quartz kaolinite and chlorite cementation that were all interpreted to have occurred prior to petroleum expulsion and pore scale to bed scale petroleum bitumen migration two major pore types were present prior to heating primary mineral pores and modified mineral pores with migrated relic om from heating experiments pores were found to be associated with stages of om maturation during the bitumen generation stage modified mineral pores were dominant and primary interparticle and intraparticle pores were present during the oil generation stage modified mineral pores with isopachous om rim were observed to be the most abundant pore type during the gas generation stage both modified mineral pores and nanometer sized spongy om pores were predominant we interpreted the occurrence of modified mineral pores to be the result of 1 oil and gas filled or partially filled voids that developed during petroleum migration and water expulsion 2 voids after removing of oil gas and water during sample preparation and 3 trapping of water molecules the formation of these nanopores was interpreted to be related to gas generation and structural rearrangement of om

structural and geomorphological aspects of the kat landslides tokat turkey and susceptibility mapping by means of gis kat county which is located in a slope of hilly region and constructed in the side of a mountain along the north anatolian fault zone is frequently subject to landslides the slides occur during periods of heavy rainfall and these events cause destruction to property roads agricultural lands and buildings in the last few decades a lot of houses and buildings have been damaged and destroyed settlement areas have remained evacuated for a long time the slope instabilities in the study area are a complex landslide extending from north to south containing a lot of landslides field investigations interpretation of aerial photography analyses of geological data and laboratory tests suggest that some factors have acted together on the slopes to cause the sliding in the wet season the slopes became saturated as the saturation of the earth material on the slope causesa rise in water pressure the shear strength resisting forces decreases and the weight driving forces increases thus the net effect was to lower the safety factor previous failures have affected the rock mass leading to the presence of already sheared surfaces at residual strengths the relation between the joint planes and the instability of the slope in the study area was discussed and it was found that the potential slope instabilities are mainly in the directions of nw se ne sw and n s the landslide susceptibility map obtained by using the geographical information system showed that a large area is susceptible and prone to landslides in the northern part of the study area

effects of smectite on the oil expulsion efficiency of the kreyenhagen shale san joaquin basin california based on hydrous pyrolysis experiments the amount of oil that maturing source rocks expel is expressed as their expulsion efficiency which is usually stated in milligrams of expelled oil per gram of original total organic carbon oil expulsion efficiency can be determined by heating thermally immature source rocks in the presence of liquid water i e hydrous pyrolysis at temperatures between 350 c and 365 c for 72 hr this pyrolysis method generates oil that is compositionally similar to natural crude oil and expels it by processes operative in the subsurface consequently hydrous pyrolysis provides a means to determine oil expulsion efficiencies and the rock properties that influence them smectite in source rocks has previously been considered to promote oil generation and expulsion and is the focus of this hydrous pyrolysis study involving a representative sample of smectite rich source rock from the eocene kreyenhagen shale in the san joaquin basin of california smectite is the major clay mineral 31 wt in this thermally immature sample which contains 9 4 wt total organic carbon toc comprised of type ii kerogen compared to other immature source rocks that lack smectite as their major clay mineral the expulsion efficiency of the kreyenhagen shale was significantly lower the expulsion efficiency of the kreyenhagen whole rock was reduced 88 compared to that of its isolated kerogen this significant reduction is attributed to bitumen impregnating the smectite interlayers in addition to the rock matrix within the interlayers much of the bitumen is converted to pyrobitumen through crosslinking instead of oil through thermal cracking as a result smectite does not promote oil generation but inhibits it bitumen impregnation of the rock matrix and smectite interlayers results in the rock pore system changing from water wet to bitumen wet this change prevents potassium ion transfer and dissolution and precipitation reactions needed for the conversion of smectite to illite as a result illitization only reaches 35 to 40 at 310 c for 72 hr and remains unchanged to 365 c for 72 hr bitumen generation before or during early illitization in these experiments emphasizes the importance of knowing when and to what degree illitization occurs in natural maturation of a smectite rich source rock to determine its expulsion efficiency complete illitization prior to bitumen generation is common for paleozoic source rocks e g woodford shale and retort phosphatic shale member of the phosphoria formation and expulsion efficiencies can be determined on immature samples by hydrous pyrolysis conversely smectite is more common in cenozoic source rocks like the kreyenhagen shale and expulsion efficiencies determined by hydrous pyrolysis need to be made on samples that reflect the level of illitization at or near bitumen generation in the subsurface

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

physical properties of petroleum formed during maturation of lower cambrian shale in the upper yangtze platform south china as inferred from phasekinetics modelling abstract lower cambrian shale in the upper yangtze platform uyp south china is an important source rock of many conventional petroleum fields and was recently recognized as a promising unconventional shale reservoir in this paper hydrocarbon generation kinetics and petroleum physical properties were investigated using the phasekinetics approach di primio and horsfield 2006 and a cambrian shale sample from the georgina basin north territory australia nta as similar paleogeological and sedimentary environments in cambrian are found for the uyp and nta the source rock comprises type ii kerogen and belongs to an organofacies generating paraffinic naphthenic aromatic low wax oil bulk petroleum generation can be described by a single frequency factor a 8 43e 14 1 s and a dominant activation energy at 56 kcal mol which is characteristic for sulphur poor organic matter deposited in an anoxic marine environment onset transformation ratio tr 10 and end tr 90 of bulk hydrocarbon generation was calculated to take place at 120 c and 165 c respectively for an assumed average geological heating rate of 1 5 c ma based on the thermal history of a local model well onset temperature was not reached until the middle triassic 241 ma when sediments were buried more than 2000 m and basalt eruptions caused enhanced heat flows the main generation stage of primary petroleum took place during the middle late triassic and ended in the early jurassic 187 ma for burial depths exceeding 4000 m tr 90 165 c temperatures increased to more than 200 c in the middle late jurassic leading to secondary cracking of primary products hydrocarbons formed at the onset tr 10 of petroleum generation can be characterized by a gas oil ratio gor of 63 sm3 sm3 a saturation pressure psat of 101 bar and a formation volume factor bo of 1 2 m3 sm3 those parameters stay low during primary petroleum generation before 203 ma at temperatures 10 000 sm3 sm3 psat 250 bar and bo 2 0 m3 sm3 during secondary cracking starting roughly at 200 ma 152 c and 3500 m burial assuming zero expulsion the shale reservoir position within the sedimentary basin indicates that bubble point pressure was always below reservoir pressure and fluids in the shale reservoir occurred only as a single undersaturated phase throughout maturation history black oil and volatile oil phases dominated during the primary cracking period whereas wet gas and dry gas phases dominated during the secondary cracking period

mechanisms of shale gas storage implications for shale gas exploration in china this article reviews the mechanisms of shale gas storage and discusses the major risks or uncertainties for shale gas exploration in china at a given temperature and pressure the gas sorption capacities of organic rich shales are primarily controlled by the organic matter richness but may be significantly influenced by the type and maturity of the organic matter mineral composition especially clay content moisture content pore volume and structure resulting in different ratios of gas sorption capacity gsc to total organic carbon content for different shales in laboratory experiments the gsc of organic rich shales increases with increasing pressure and decreases with increasing temperature under geologic conditions assuming hydrostatic pressure gradient and constant thermal gradient the gsc increases initially with depth due to the predominating effect of pressure passes through a maximum and then decreases because of the influence of increasing temperature at greater depth this pattern of variation is quite similar to that observed for coals and is of great significance for understanding the changes in gsc of organic rich shales over geologic time as a function of burial history at an elevated temperature and pressure and with the presence of moisture the gas sorption capacities of organic rich shales are quite low as a result adsorption alone cannot protect sufficient gas for high maturity organic rich shales to be commercial gas reservoirs two models are proposed to predict the variation of gsc and total gas content over geologic time as a function of burial history high contents of free gas in organic rich shales can be preserved in relatively closed systems loss of free gas during postgeneration uplift and erosion may result in undersaturation the total gas contents lower than the sorption capacity and is the major risk for gas exploration in marine organic rich shales in china

a multidisciplinary approach in determining the maceral kerogen type and mineralogical composition of upper cretaceous eagle ford formation impact on pore development and pore size distribution abstract maceral kerogen or organic matter type and mineralogical composition with the associated porosity of the upper cretaceous eagle ford formation karnes county texas was investigated in karnes county the calcareous mudstone of the eagle ford formation was deposited in an open marine outer shelf to upper slope environment to adequately characterise all components of this mudrock a multidisciplinary approach was implemented to analyse 26 core samples from a single producing well that completed within the eagle ford formation analyses included organic petrology organic geochemistry light and electron microscopy and spectroscopy pore size distribution analyses and x ray diffraction the bitumen reflectance ranges between 1 94 and 2 08 calculated vr o 1 60 1 69 indicating the mudrock is in the condensate rich gas window the toc content ranges between 1 7 and 7 2 with an average of 3 9 mineral composition is dominated in descending order by calcite clay quartz and plagioclase calcite varies between 32 and 87 with an average of 57 porosity measured by helium pycnometry ranges between 3 5 and 10 3 with an average of 7 5 organic petrology coupled with backscattered and field emission scanning electron microscopy indicates matrix bitumen as the most significant contributor to the toc content and porosity matrix bitumen contains significant meso and microporosity and is enhanced by the secondary cracking of the bitumen an increase in bioclastic mostly foraminifera and siliciclastic components correlates with lower toc content due to the lower volume of organic rich matrix peloids fecal pellets are calcareous organic rich and lack terrigenous sediment indicating a zooplankton source pelagic deposition of peloids is interpreted as a primary mechanism of amorphinite deposition which is converted to hydrocarbons and matrix bitumen the mixed siliciclastic calcareous matrix that surrounds the peloids is comprised of matrix bitumen and dispersed organics from land plants vitrinite fusinite and inertodetrinite the siliciclastic component increases in the middle of the eagle ford and marks the boundary maximum flooding surface between the lower tst and upper hst section of the formation the inorganic and organic components suggest a mixed terrigenous and marine source with both inorganic and organic sediments being derived from the proximal ouachita thrust belt and from pelagic organisms within the overlying water column the lower tst eagle ford formation contains more micro and mesopores than the upper hst eagle ford formation due to higher toc content in the lower eagle formation these results illustrate that a multidisciplinary approach is necessary to identify how pore network are distributed within mudrocks and how this distribution is controlled by organic inorganic deposition and hydrocarbon generation processes

evolution of porosity and pore types in organic rich calcareous lower toarcian posidonia shale low and high resolution petrographic studies have been combined with mineralogical toc rockeval and porosity data to investigate controls on the evolution of porosity in stratigraphically equivalent immature oil window and gas window samples from the lower toarcian posidonia shale formation a series of 26 samples from three boreholes wickensen harderode and haddessen in the hils syncline was investigated the main primary components of the shales are microfossiferous calcite 30 50 clay minerals 20 30 and type ii organic matter toc 7 15 hi 630 720 mg gc in immature samples characteristic sub centimetric light and dark lamination reflects rapid changes in the relative supply of these components total porosities decrease from 10 to 14 at ro 0 5 to 3 5 at ro 0 9 and then increase to 9 12 at ro 1 45 these maturity related porosity changes can be explained by a the primary composition of the shales b carbonate diagenesis c compaction and d the maturation micro migration local trapping and gasification of heterogeneous organic phases calcite undergoes dissolution and reprecipitation reactions throughout the maturation sequence pores quantifiable in sem ca 50 nm account for 14 25 of total porosity at ro 0 5 sem visible macropores1 are associated mainly with biogenic calcite at this maturity clays and organic matter are not visibly porous but nevertheless hold most of the shale porosity porosity loss into the oil window reflects a compaction b carbonate cementation and c perhaps the swelling of kerogen by retained oil in addition porosity is occluded by a range of bituminous phases especially in microfossil macropores and microfractures in the gas window mineral hosted porosity is still the primary form of macroporosity most commonly observed at the organic inorganic interface increasing porosity into the gas window also coincides with the formation of isolated spongy and complex meso and macropores within organic particles related to thermal cracking and gas generation this intraorganic porosity is highly heterogeneous point counted macroporosity of individual organic particles ranges from 0 to 40 with 65 of organic particles containing no macropores we suggest that this reflects the physicochemical heterogeneity of the organic phases plus the variable mechanical protection afforded by the mineral matrix to allow macroporosity to be retained the development of organic macroporosity cannot alone account for the porosity increase observed from oil to gas window major contributions also come from the increased volume of organic micro and meso porosity and perhaps by kerogen shrinkage

rupture characteristics of clustered microearthquakes and variations in fault properties in the new madrid seismic zone seismic waveforms from the portable array for numerical data acquisition panda network were used to relocate 45 events occurring in four spatial clusters in the northern new madrid seismic zone nmsz source time functions of the larger ml 2 5 events were obtained and yield estimates of rupture radii between 130 and 175 m and static stress drops at or below the megapascal level there is a tendency for closely located events within 200 m from one another to occur within short time intervals of minutes to days available focal mechanism solutions reveal that some of the clustered events have diverse slip directions indicating that the ruptures occur on adjacent fault patches rather than being repetitive over the same patch on the basis of this and a previous study of events farther south we infer that the properties of the faulting system in the nmsz are laterally heterogeneous and are subject to effects of some temporally and spatially localized processes that drive the faults toward seismic failure comparison of this observation with that in the san andreas fault near parkfield reveals that event clustering occurs in both fault systems on similarly short spatial and temporal scales the inferred localized processes may occur in both fault systems despite their different tectonic environment far field loading rate and geometric style of deformation on the other hand in the nmsz we have not observed any quasiperiodic and repetitive ruptures that have been observed near parkfield this is consistent with a slower or absent aseismic creeping in the nmsz

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

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

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

influence of differential structural deformation on shale reservoirs a case study of the lower silurian longmaxi shale in north guizhou southern china

mass movement in the himalaya new insights and research directions abstract ongoing studies that relate tectonics to the processes at the surface of earth show that many more sources of information about agents of shallow denudation such as mass movement are required to comprehend the long term erosion that leads to deep denudation over geologic time mass movement in the himalaya is scale dependent from the massive extension of whole mountain ranges gravity tectonics through the sackung failure of single peaks to the smallest slope failures generally denudation of the himalayan orogen begins with slope failure onto glaciers and into river valleys and continues by glacial and fluvial transport the maximum size of stable slopes and mean angles of slope that are produced by these failures are complex and controlled by a variety of factors including mass strength of the rocks stress fields angles of internal friction controlled by rock type cohesion that includes the control of rock temperature bulk unit weight of rock and discontinuities the processes of mass movement in the himalaya have been described many times for the past two centuries recently developments in a variety of fields have been introduced to assess the character of mass movement geomorphometry remote sensing digital elevation models and geographic information system technology are revolutionizing the study of mass movement in the himalaya

application of logistic regression for landslide susceptibility zoning of cekmece area istanbul turkey as a result of industrialization throughout the world cities have been growing rapidly for the last century one typical example of these growing cities is istanbul the population of which is over 10 million due to rapid urbanization new areas suitable for settlement and engineering structures are necessary the cekmece area located west of the istanbul metropolitan area is studied because the landslide activity is extensive in this area the purpose of this study is to develop a model that can be used to characterize landslide susceptibility in map form using logistic regression analysis of an extensive landslide database a database of landslide activity was constructed using both aerial photography and field studies about 19 2 of the selected study area is covered by deep seated landslides the landslides that occur in the area are primarily located in sandstones with interbedded permeable and impermeable layers such as claystone siltstone and mudstone about 31 95 of the total landslide area is located at this unit to apply logistic regression analyses a data matrix including 37 variables was constructed the variables used in the forwards stepwise analyses are different measures of slope aspect elevation stream power index spi plan curvature profile curvature geology geomorphology and relative permeability of lithological units a total of 25 variables were identified as exerting strong influence on landslide occurrence and included by the logistic regression equation wald statistics values indicate that lithology spi and slope are more important than the other parameters in the equation beta coefficients of the 25 variables included the logistic regression equation provide a model for landslide susceptibility in the cekmece area this model is used to generate a landslide susceptibility map that correctly classified 83 8 of the landslide prone areas

statistical analysis of landslide susceptibility at yongin korea the aim of this study is to evaluate the susceptibility of landslides at yongin korea using a geographic information system gis landslide locations were identified in the yongin area from interpretation of aerial photographs field surveys and maps of the topography soil type timber cover and geology these data were collected and constructed into a spatial database using gis the factors that influence landslide occurrence such as slope aspect and curvature of topography were calculated from the topographic database texture material drainage and effective soil thickness were extracted from the soil database and type age diameter and density of timber were extracted from the forest database lithology was extracted from the geological database and land use was classified from the landsat tm satellite image landslide susceptibility was analyzed using the landslide occurrence factors by probability and logistic regression methods the results of the analysis were verified using the landslide location data the validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location the gis was used to analyze the vast amount of data efficiently and statistical programs were used to maintain specificity and accuracy the results can be used to reduce associated hazards and to plan land use and construction

imaging pores in sedimentary rocks foundation of porosity prediction abstract this review examines the history and current practice of technologies for imaging of pores in sedimentary rocks pores are that portion of the rock volume occupied by components of relative mobility such as water of various salinities microbial life petroleum liquids gases and supercritical fluids through a rock s history the contained pores evolve as the primary detrital assemblage responds chemically and mechanically to changing conditions in the subsurface description and classification of pores based upon their paragenesis depends upon inspection by imaging that allows the pores to be seen and interpreted in the context of historical processes responsible for formation of the pore walls since the late 1960s sample preparation and imaging methodologies that clarified our understanding of pores in their correct historical context have been at the root of important advances in prediction of porosity and related bulk properties in the subsurface these older approaches are now joined by new technologies that serve current efforts to extend predictive capabilities to nm scale pores in the fine grained low permeability rocks that dominate in the deeper parts of sedimentary basins and indeed in the sedimentary record as a whole placing the smallest pores into their proper paragenetic context presents a challenge in the quest to develop predictive models for porosity evolution in fine grained rocks

origin properties and implications of solid bitumen in source rock reservoirs a review abstract this paper reviews the significance of solid bitumen with emphasis on source rock reservoirs we discuss difficulties and discrepancies with terminology especially those terms related to the origin of solid bitumen and its physical and chemical properties various definitions of solid bitumen have their own justifications and can be used provided there is clarity about which defining criteria are being considered difficulties in conforming to chemical solubility or origin related definitions lead us to suggest adapting the reflectance of solid hydrocarbon as a practical choice for placing the boundary between solid bitumen and pyrobitumen and 1 50 is proposed as the boundary value it has to be noted that this boundary may be shifted down to 1 3 for sulfur rich kerogen recently much progress has been made by combining imaging and physical adsorption techniques in porosity studies and so the porosity of solid bitumen is given special emphasis comparing pore characteristics obtained from sem versus those generated by gas adsorption mercury intrusion or neutron scattering techniques indicates that the sem pore inventory fails to account for the smallest pores we review the implications of the abundance of solid bitumen on reservoir quality porosity permeability and producibility based on examples of selected sequences one of the difficulties in predicting the influence of solid bitumen bearing horizons on reservoir quality arises from the problems with detecting organic phases using various logging techniques the use of specialized techniques such as nmr logging that allows two dimensional t1 and t2 measurements should be expanded and other potential techniques need to be further researched and tested certain aspects of the properties of solid bitumen that are not as well understood such as its hydrocarbon generation potential or its role in hydrocarbon migration are also discussed with the aim of identifying further research that could lead to a better understanding of the role that solid bitumen plays in unconventional reservoirs

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

landslide susceptibility mapping in the damrei romel area cambodia using frequency ratio and logistic regression models this study applied tested and compared a probability model a frequency ratio and statistical model a logistic regression to damre romel area cambodia using a geographic information system for landslide susceptibility mapping landslide locations were identified in the study area from interpretation of aerial photographs and field surveys and a spatial database was constructed from topographic maps geology and land cover the factors that influence landslide occurrence such as slope aspect curvature and distance from drainage were calculated from the topographic database lithology and distance from lineament were extracted and calculated from the geology database land cover was classified from landsat tm satellite imagery the relationship between the factors and the landslides was calculated using frequency ratio and logistic regression models the relationships frequency ratio and logistic regression coefficient were overlaid to make landslide susceptibility map then the landslide susceptibility map was compared with known landslide locations and tested as the result the frequency ratio model 86 97 and the logistic regression 86 37 had high and similar prediction accuracy the landslide susceptibility map can be used to reduce hazards associated with landslides and to land cover planning

a super large landslide in tibet in 2000 background occurrence disaster and origin on april 9 2000 a super large landslide 3 x 10 8 m 3 occurred along zhamu creek southeast tibet as a result a landslide dam formed and the yigong river was blocked a channelized diversion was constructed for prevention of overtopping two months later on june 10 a catastrophic flood resulting from the failure of the landslide dam caused a serious loss of property this is the second of landslide occasion dam formation and flooding occurrence at the same site since 1900

shale gas desorption behavior and carbon isotopic variations of gases from canister desorption of two sets of gas shales in south china abstract four shale samples from the lower silurian longmaxi formation and the lower cambrian shuijingtuo formation in the eastern part of chongqing sw china were subjected to canister desorption experiments at reservoir and elevated temperatures up to 90 c to investigate shale gas release behaviors and their variations in chemical and isotopic compositions of desorbed gases both the ratios of gas released at reservoir temperature to the total desorbed gas at reservoir and elevated temperatures and the desorption rates suggest that the longmaxi shale gas is more easily released than the shuijingtuo shale gas scanning electron microscope sem observation along with low temperature co2 and n2 adsorption results suggests that organic matter hosted pores with diameters of 2 100 nm are rich in the longmaxi shales whereas well developed micropores