pore structure gas storage and matrix transport characteristics of lacustrine newark shale abstract shale gas production in the u s fuelled research activities in unconventional reservoir rock characterization most studies focused on organic rich shales of marine origin while disregarding lacustrine sequences in this study thirteen lacustrine shale samples from the newark basin nj usa are comprehensively characterised in terms of pore structure gas storage and matrix transport characteristics these thermally overmature vrr 1 4 2 7 shales have a na rich heterogeneous mineralogy with toc contents of up to 3 6 methane sorption capacity and pore structure parameters as identified with low pressure n2 physisorption microporosity bet surface area are neither interrelated with each other nor with any shale components e g clay content toc in contrast porosity shows a positive correlation with toc content which is also typical for many thermally overmature marine shale sequences correspondingly porosity and toc positively correlate to bedding parallel matrix permeability coefficients between 2 and 80 nd at 40 mpa effective stress in contrast permeability coefficients perpendicular to bedding are two to three orders of magnitude lower compared to previous studies on marine lithotypes newark shales have rather poor gas storage properties with average he porosities of 2 3 and average methane sorption capacities of 0 047 mmol g 1

the palos verdes anticlinorium along the los angeles california coast implications for underlying thrust faulting 1 the palos verdes anticlinorium pva is a 70 km wide nw trending pliocene quaternary transpressional high that separates the onshore los angeles basin from the offshore san pedro basin the pva southwest limb underlies a 70 km long sw facing seafloor escarpment this escarpment is separated into two segments by a 6 km right step it overlies two levels of ne dipping low angle thrust faults these faults project beneath los angeles toward known sw verging blind thrust faults and may be the same regional faults these conclusions are based on a detailed geometric representation constructed from a regional analysis of 5000 km of multichannel seismic reflection profiles logs and paleontology from 19 wells published seafloor geology and multibeam bathymetric data patterns of sedimentation and erosion indicate that folding of pva initiated during pliocene time and propagated southward with folding of part of the southern pva occurring during the quaternary structural relief continues to grow with regional long term rock uplift of the pva crest and ongoing subsidence in the adjacent basins the low angle ne dipping faults beneath the pva must be late quaternary active in order to maintain hanging wall rock uplift above subsiding footwalls structural geometry requires that the underlying faults have slipped at 1 1 1 6 mm yr over quaternary time

logging evaluation of free gas saturation and volume content in wufeng longmaxi organic rich shales in the upper yangtze platform china abstract the wufeng longmaxi shale is the most important target for the exploration and production of shale gas in china there are two important parameters of great importance to shale gas evaluation free gas saturation and content however current models that have been proposed based on the use of sandstone are not applicable to this shale gas reservoir due to differences in conductivity mechanisms between these two types of reservoirs in this study after the pore volume of gas shale had been classified into three phases those being the adsorbed phase pore free phase pore and bound water pore we proposed a method to calculate the free gas saturation and content from well logging data based on the pore volume model our method utilizes the following procedures 1 determining the total porosity on the basis of the matrix value of dry clay 2 establishing a quantitative correlation of the bound water content to the clay content and then determining the bound water porosity 3 calculating the absorbed gas content by langmuir formula 4 calculating the adsorbed phase porosity according to the principle of mass conservation after determining the underground density of the adsorbed phase in the range of 0 4 1 2 g cm3 and 5 determining the free gas saturation and free gas content field examples show that the predicted shale porosity free gas and adsorbed gas contents calculated by using our proposed model accurately coordinate with the core derived results which verified that the proposed method was valuable to evaluating the wufeng longmaxi shale gas reservoir

tectonic influences on the preservation of marine terraces old and new evidence from santa catalina island california abstract the california channel islands contain some of the best geologic records of past climate and sea level changes recorded in uplifted fossil bearing marine terrace deposits among the eight california channel islands and the nearby palos verdes hills only santa catalina island does not exhibit prominent emergent marine terraces though the same terrace forming processes that acted on the other channel islands must also have occurred on santa catalina we re evaluated previous researchers field evidence and examined new topographic bathymetric and stream profile data in order to find possible explanations for the lack of obvious marine terrace landforms or deposits on the island today the most likely explanation is associated with the island s unresolved tectonic history with evidence for both recent uplift and subsidence being offered by different researchers bathymetric and seismic reflection data indicate the presence of submerged terrace like landforms from a few meters below present sea level to depths far exceeding that of the lowest glacial lowstand suggesting that the catalina island block may have subsided submerging marine terraces that would have formed in the late quaternary similar submerged marine terrace landforms exist offshore of all of the other california channel islands including some at anomalously great depths but late quaternary uplift is well documented on those islands therefore such submarine features must be more thoroughly investigated and adequately explained before they can be accepted as definitive evidence of subsidence nevertheless the striking similarity of the terrace like features around santa catalina island to those surrounding the other uplifting channel islands prompted us to investigate other lines of evidence of tectonic activity such as stream profile data recent uplift is suggested by disequilibrium stream profiles on the western side of the island including nickpoints and profile convexities rapid uplift is also indicated by the island s highly dissected steep topography and abundant landslides a likely cause of uplift is a restraining bend in the offshore catalina strike slip fault our analysis suggests that santa catalina island has recently experienced and may still be experiencing relatively rapid uplift causing intense landscape rejuvenation that removed nearly all traces of marine terraces by erosion a similar research approach incorporating submarine as well as subaerial geomorphic data could be applied to many tectonically active coastlines in which a marine terrace record appears to be missing

extension of the parana basin to offshore brazil implications for coalbed methane evaluation abstract coalbed methane cbm is a worldwide exploration target of the petroleum industry in brazil the most important coal bearing succession is associated with the permian rio bonito formation of the parana basin the gas prone areas are located at the southeastern margin of the parana basin and possibly in the offshore region of the northern part of the pelotas basin coalfields end abruptly at the present day shoreline a result of rifting of gondwana and the evolution of the south atlantic ocean all geologic indicators suggest that in pre rift times the coal seams extended further eastwards probably now lying deeply buried below the sedimentary succession of the pelotas basin the present paper discusses structural stratigraphic seismic and aeromagenetic data that support the preservation of continental crust beneath ocean sediment if the coal beds had similar lateral extent to known onshore coals and coal beds extended across the projected extension of the parana basin and there was a conservative 5 m of cumulative coal thickness then a potential methane volume can be estimated for this newly inferred resource average onshore coal gas content is 32 scf ton 1 00 m 3 ton if this is similar in the offshore coal deposits then the hypothetical methane volume in the offshore area could be in excess of 1 9 10 12 scf 56 10 9 m 3 metamorphism from dikes associated with rifting are potential complicating factors in these deposits and since no borehole reaching the deep lying strata in the offshore area are available this is a hypothetical gas resource with a certain level of uncertainty which should be tested in the future by drilling a deep borehole

high pressure methane and carbon dioxide sorption on coal and shale samples from the parana basin brazil abstract an experimental study has been conducted to assess the potential for coalbed methane production and carbon dioxide storage in coals carbonaceous shales and source rocks in the parana basin in brazil high pressure sorption tests with methane and carbon dioxide were performed on coal and carbonaceous shales from the santa terezinha coalfield and samples from two principal petroleum source rocks measured excess sorption capacities ranged from 0 03 to 0 47 mmol g for methane and 0 14 to 0 81 mmol g for carbon dioxide showing a decrease with decreasing organic matter content linear regression lines for methane sorption capacity vs toc extrapolated to approximately zero whereas for carbon dioxide the intercept of the regression line indicated a residual sorption capacity of 0 2 mmol g on the mineral matter present day gas contents of coals collected from the first cbm well in the santa terezinha coalfield correspond to 13 38 of the measured maximum sorption capacities carbon dioxide sorption capacities exceed methane sorption capacities by a factor of 1 9 to 6 9 for these coals free sorption capacities of the under saturated coals in combination with preferential sorption of carbon dioxide could favour co 2 enhanced methane recovery and co 2 storage in coals and shales of the study area based upon the calculated coal reserves gas contents and measured sorption capacities a total storage potential of 15 4 gt co 2 was estimated for an area of 20 40 km 2 in the santa terezinha coal field assuming a combined co 2 enhanced coalbed methane ecbm production and co 2 storage operation to fully evaluate the potential for carbon dioxide storage and coalbed methane production further studies are required to assess producibility of methane and efficiency of long term co 2 storage in the study area

production of gas from coal seams in the upper silesian coal basin in poland in the post injection period of an ecbm pilot site a pilot site for co2 storage in coal seams was set up in the upper silesian coal basin in poland in the scope of the recopol project funded by the european commission about 760 tons co2 were injected into the reservoir from august 2004 to june 2005 breakthrough of the injected co2 was established which resulted in the production of about 10 of the injected co2 in this period this paper reports on activities performed under the european commission project movecbm that aimed at the assessment of the storage performance of the reservoir in the follow up period i e whether the injected co2 was adsorbed onto the coal or whether it was still present as free gas in the pore space the injection well was used for this purpose as the production well had to be abandoned for permitting reasons several operational periods can be defined between the last injection in june 2005 and the abandonment of the well in october 2007 in the first period the well was shut in to observe the pressure fall off from about 15 0 mpa at the wellhead after the last injection until about 4 5 mpa at the end of 2005 this pressure fall off curve showed that the reservoir permeability was very low this seemed to confirm the observed swelling of the coal during the injection period in the first months of 2006 the pressure at the wellhead was decreased by releasing gas in a controlled way the amount and composition of the gas were measured as a result of the pressure reduction the well flooded with water a production pump was placed on the former injection well enabling active production from the coal from march to september 2007 results of these operations showed that whereas the gas production rates were as expected based on the experience with the production well the water production was remarkably low this could be related to permeability issues or alternatively indicate a drying effect of the co2 in the reservoir further the gas composition showed a predominance of co2 over ch4 during the gas release that changed gradually into a predominance of ch4 over co2 during the production phase although stabilization was not reached within the given production period the composition approached a 60 methane 40 co2 ratio this indicates that the exchange of these gases is more complex than often envisaged after removal of the pump the well was filled with water which ceased the gas release this indicates that the pressure in the reservoir was back to its original hydrostatic state as the total volume of co2 produced was only a fraction of the amount that was injected it can be concluded that the co2 was taken up by the coal and is currently adsorbed this gives confidence in the long term stability of the injected co2 2008 elsevier b v all rights reserved

integrated model of the crustal structure in the gulf of california extensional province abstract a method of constructing 3d earth models from a suite of 1d profiles is demonstrated using delaunay triangulation accurate crustal models are required to correct for crustal contamination in seismic tomography of the mantle and can be used as starting points for higher resolution tomography of the lithosphere and asthenosphere using a simple input data set 1d vertical profiles provides for rapid prototyping model building and modification any structural length scale in the final 3d model is possible using this method through precise placement of 1d profiles and triangulation collections of layers within the 1d profiles are grouped and identified by keys called superlayers allowing for 3d discontinuities and variations along these important interfaces the method was applied to the gulf extensional province and baja california regions to account for the laterally discontinuous crustal variations during a tomographic inversion for mantle structure use of the 3d model and appropriate regional crustal wave speeds minimizes wave speed variations in the tomographic model and assists interpretation of the final model

estimation of marine shale methane adsorption capacity based on experimental investigations of lower silurian longmaxi formation in the upper yangtze platform south china abstract methane adsorption experiments were performed on eight lower silurian longmaxi moisture equilibrated shale samples from the upper yangtze platform south china at pressures up to 12 mpa at 20 c 40 c 60 c 80 c and 100 c to investigate the effects upon methane adsorption capacity and to estimate the variation of methane adsorption capacity as a function of depth and burial history the methane adsorption capacity of the longmaxi shale shows a significant positive correlation with total organic carbon toc content which is accompanied by an increase in bet brunauer emmett teller surface area and total pore volume a quadratic relationship was observed between clay content and methane adsorption capacity there is a threshold clay content 42 3 44 4 in this trend methane adsorption capacity declines with increasing clay content below the threshold and later increases with increasing clay content the langmuir pressure decreases exponentially with the reciprocal of temperature and the langmuir volume decreases linearly with temperature the isosteric heat of adsorption and standard entropy for the longmaxi shale ranges from 10 34 to 11 67 kj mol and from 57 04 to 61 32 j mol k respectively which are clustered around kerogen type i using these relationships a computational scheme was developed to calculate methane adsorption capacity as a function of toc content temperature and pressure based on the langmuir equation this algorithm was applied to estimate methane adsorption capacity of the longmaxi shale as a function of depth due to the dominating effect of pressure methane adsorption capacity increases initially with depth through a maximum and then decreases as a result of increasing temperature at a greater depth the maximum gas adsorption capacity is typically located at a depth range between 800 and 1350 m with toc content increasing the curves shift continuously towards higher adsorption capacity furthermore the maximum methane adsorption capacity moves higher and shifts to a deeper depth as toc content increases ultimately four principal dynamic evolutionary stages of methane adsorption capacity of the longmaxi shale over geologic time as a function of burial history were reconstructed

high resolution mapping of two large scale transpressional fault zones in the california continental borderland santa cruz catalina ridge and ferrelo faults new mapping of two active transpressional fault zones in the california continental borderland the santa cruz catalina ridge fault and the ferrelo fault was carried out to characterize their geometries using over 4500 line km of new multibeam bathymetry data collected in 2010 combined with existing data faults identified from seafloor morphology were verified in the subsurface using existing seismic reflection data including single channel and multichannel seismic profiles compiled over the past three decades the two fault systems are parallel and are capable of large lateral offsets and reverse slip during earthquakes the geometry of the fault systems shows evidence of multiple segments that could experience throughgoing rupture over distances exceeding 100 km published earthquake hypocenters from regional seismicity studies further define the lateral and depth extent of the historic fault ruptures historical and recent focal mechanisms obtained from first motion and moment tensor studies confirm regional strain partitioning dominated by right slip on major throughgoing faults with reverse oblique mechanisms on adjacent structures transpression on west and northwest trending structures persists as far as 270 km south of the transverse ranges extension persists in the southern borderland a logjam model describes the tectonic evolution of crustal blocks bounded by strike slip and reverse faults which are restrained from northwest displacement by the transverse ranges and the southern san andreas fault big bend because of their potential for dip slip rupture the faults may also be capable of generating local tsunamis that would impact southern california coastlines including populated regions in the channel islands

adsorption of methane carbon dioxide and their binary mixtures on jurassic shale from the qaidam basin in china abstract co 2 enhanced shale gas recovery which plays a crucial role in energy resource development involves the adsorption of binary mixtures of ch 4 and co 2 on shale while numerous previous studies have provided useful insight into ch 4 co 2 sorption characteristics on shale few studies have been conducted on binary mixtures absorption on shale to get better understanding in this field we carried out an experimental study using shale samples from the qaidam basin in china to investigate the adsorption mechanism of ch 4 and co 2 and their binary mixtures on shales and to evaluate the shale co 2 enhanced gas recovery potential in more details the results indicate that the co 2 sorption capacity exceeds that of the methane sorption by a factor of 4 for these shales the study also shows that in the adsorption system of the mixtures co 2 plays an advantageous role in the competitive adsorption process the shale exhibits various behaviors of preferential adsorption of co 2 which can be related to the shale pore structure maximum values of isosteric heat of adsorption for co 2 and ch 4 are found to be 17 7 kj mol and 12 6 kj mol respectively in addition our work denoted that the isosteric heat of adsorption for co 2 on shale samples increases with increasing adsorption capacity the study suggests that the co 2 enhanced gas recovery pattern can be feasible for shales in the qaidam basin

petrology and chemistry of permian coals from the parana basin 1 santa terezinha leao butia and candiota coalfields rio grande do sul brazil the current paper presents results on petrological and geochemical coal seam characterization in permian coal bearing strata from the parana basin southern brazil sequence stratigraphic analysis shows that peat accumulation in permian time was closely linked to transgressive regressive cycles with peat accumulation occurring in a predominantly back barrier lagoonal setting coal petrographic analysis indicates subbituminous coals at candiota and leao butia and high volatile bituminous coals at santa terezinha where locally the coal seams are thermally altered by volcanic intrusions petrographic composition is highly variable with seams at candiota and santa terezinha frequently enriched in inertinite chemical analyses indicate that all coals are mineral matter rich mean 49 09 wt with sio2 and al2o3 dominating as determined by icp aes quartz is also the predominant mineral detected by x ray diffraction where it is associated with feldspar kaolinite and hematite and iron rich carbonates the results from scanning electron microscopy are broadly consistent with the bulk chemical and mineralogical analysis quartz and clays are common in all samples analyzed other minerals observed were amongst others carbonates calcite siderite ankerite pyrite monazite kaolinite barite sphalerite rutile and quartz of volcanic origin the distribution of trace elements is well within the range typical for coal basins of other areas despite the fact that the parana basin coals are very high in ash yields the average concentrations for elements of environmental concern as b be cd co cr cu hg li mn mo ni pb sb se tl u v zn are similar to or less than the mean values for u s coal however considered on an equal energy basis parana basin coals will produce in combustion 5 to 10 times the amount of most elements compared to an equal weight us coal concentrations of major and trace elements such as fe b and s appear to be controlled by depositional setting with increasing values in coal seams overlain by brackish marine strata hierarchical cluster analysis identified three groups of major minerals and seven groups of trace elements based on similarity levels on a regional scale the coalfields can be separated by the differences in rank candiota and leao butia versus santa terezinha and by applying discriminant analysis based on 4 trace elements li as sr sb highest rb and sr values occur at candiota and are linked to syngenetic volcanism of the area whereas high y and sr values at santa terezinha can be related to the frequent diabase intrusions in that area

mercury and silver rich ferromanganese oxides southern california borderland deposit model and environmental implications mercury and silver enriched ferromanganese oxide crusts were recovered at water depths of 1 750 to1 300 m from la victoria knoll located about 72 km off the coast of northern baja california no other ferromanganese precipitate found so far in the modern ocean basins is similarly enriched in hg and ag the precipitates consist of submetallic gray brecciated mn oxide layers overlain by brown earthy laminated fe mn oxide crusts both oxide types are rich in hg to 10 ppm and ag to 5 5 ppm the mn rich layers are composed of mno 2 with lesser amounts of 10a and 7a manganates whereas the mn phase in the fe mn crusts is solely mno 2 the fe phase in both layers is x ray amorphous established criteria for distinguishing hydrothermal versus hydrogenetic crusts indicate that the mn rich layers are predominantly of low temperature hydrothermal origin whereas the fe mn crusts are hydrogenetic although there is some overlap in the source of chemical components in both types la victoria knoll is uplifted continental basement rock with basalt andesite and schist cropping out at the surface the knoll may have an intrusive core the hg and ag were derived from leaching by hydrothermal fluids of organic matter rich sediments in basins adjacent to la victoria knoll and to a lesser extent from continental basement rocks underlying the knoll and adjacent basins both rock types are notably enriched in ag and hg faults were the main fluid transport pathway and hydrothermal circulation was driven by high heat flow associated with thinned crust other elements derived from the hydrothermal fluids include tl cd cr and li the main host for hg and ag is feooh although mno 2 likely hosts some of the ag minor sulfide and barite also may contain small amounts of these metals possible analogs in the geologic record for this deposit type are found in the basin and range province of the western united states and mexico the discovery highlights the fact that fluids circulating along faults in the offshore california borderland are transporting potentially toxic metals hg ag tl as cd cr pb and ni and depositing them on and just below the ocean floor

quantitative evaluation of toc organic porosity and gas retention distribution in a gas shale play using petroleum system modeling application to the mississippian barnett shale abstract shale reservoirs have not benefited from advanced modeling tools to the extent of conventional resources thus an approach is proposed to integrate key parameters such as total organic carbon toc content methane adsorption and organic porosity in a basin simulator original toc has an impact on both gas generated volume and gas retention within source rocks the conversion of organic matter into hydrocarbons also creates additional intraparticle kerogen porosity in which oil and gas can be stored in this work a method is proposed to calculate the evolution of toc organic porosity and gas retention capacity free versus adsorbed through time in shale gas by means of petroleum system modeling gas adsorption potential on organic material is calculated using a langmuir model which accounts for pressure temperature and remaining solid toc organic porosity is calculated as the result of the change of the organic matter from solid immature kerogen to less dense fluid hydrocarbons during thermal maturation the method is tested on a 3d basin model of the mississippian barnett shale in texas usa the computed organic porosity varies from 0 in immature zones to a maximum of 4 of rock volume in organic rich and mature zones computed retained methane in the lower barnett shale ranges between 20 and 60 scf t from 1 to nearly 3 kg m3 and is mainly concentrated in mature areas of the basin simulated results are consistent with available barnett shale data possible effects of assumptions made in the approach and perspectives are discussed

investigation of methane sorption of overmature wufeng longmaxi shale in the jiaoshiba area eastern sichuan basin china abstract in china shale gas of production capacity 203 000 m3 per day has been identified in well jy1 in the upper ordovician wufeng formation shale o3w and the lower silurian longmaxi formation shale s1l jiaoshiba area sichuan basin however the adsorbed gas capacity and the relative ratio between free gas and adsorbed gas are unknown in the jiaoshiba area and this is important for further shale gas exploration and development and different adsorption models need to be calibrated very well to praise the sorption capacity the samples were obtained from the well jy1 sorption isotherm experiments were performed at a range of pressures up to 17 mpa and temperatures up to 90 c to determine the effects of toc moisture and clay minerals on methane adsorption capacity the methane maxima adsorbed capacity values have a clear positive relationship with toc clay content displays a weak correlation with methane adsorbed amounts normalized to toc indicating that clay minerals are a minor contributor to shale adsorption capacity moisture reduces methane sorption capacity by around 20 both the supercritical dubinin radushkevich sdr based and the langmuir based excess adsorption models are used to fit measured adsorption isotherms most of the methane adsorption phase density values fitted by both models are greater than the density of liquid phase methane at its boiling points 424 mg cm3 for the langmuir based model a fixed adsorption density of 424 or 373 mg cm3 was used in fitting the experimental data which will result in higher maximum adsorbed capacity values for the sdr based model maxima adsorbed capacity values remain stable and have nothing to do with sorption phase density

comparison of high pressure co2 sorption isotherms on central appalachian and san juan basin coals accurate estimation of carbon dioxide co2 sorption capacity of coal is important for planning the co2 sequestration efforts in this work we investigated sorption and swelling behavior of several eastern and western us coal samples from the central appalachian basin and from san juan basin the co2 sorption isotherms have been completed at 55 c for as received and dried samples the role of mineral components in coal the coal swelling the effects of temperature and moisture and the error propagation have been analyzed changes in void volume due to dewatering and other factors such as temporary caging of carbon dioxide molecules in coal matrix were identified among the main factors affecting accuracy of the carbon dioxide sorption isotherms the helium void volume in the sample cells was measured before and after the sorption isotherm experiments and was used to build the volume corrected data plots

upper crustal structure and neogene tectonic development of the california continental borderland multichannel seismic reflection data sonobuoy seismic refraction data and regional geology are used to define the upper crustal structure of the southern california continental borderland and to delineate the characteristics of the main lithotectonic belts of the region the catalina schist belt is separated on its west side from the gently deformed nicolas forearc belt by faults that have steep west dips and pronounced normal separations on its east side the schist belt is bounded by a large detachment fault that dips gently to the east beneath the west edge of the peninsular ranges belt at the coastline near oceanside the catalina schist was uplifted from middle crustal depths and exposed during a major event of extensional tectonism that started in early miocene time in conjunction with about 10 of clockwise rotation of the western transverse ranges belt part of the uplift of the catalina schist could have occurred on the detachment fault but it is thought to have mostly occurred on the steep faults that bound the west edge of the schist belt a large amount of uplift is required and it probably involved strong footwall flexural deformation in the wake of the translating and rotating western transverse ranges and nicolas forearc belts extension accompanied by probable large amounts of right slip continued in the borderland region during and after middle miocene time the later stage of extension was accompanied by rapid clockwise rotation of the western transverse ranges of at least 90 most of the borderland including the belt of schist that was uplifted in early miocene time was further deformed into numerous basins and ridges during this stage of oblique extension the primary driving force for the deformation is thought to have been derived from the rapid northwest motion of the pacific plate after it had become coupled to the farallon plate system which had previously been subducted beneath the borderland

co2 sequestration potential of charqueadas coal field in brazil abstract although coal is not the primary source of energy in brazil there is growing interest to evaluate the potential of coal from the south of the country for various activities the i2b coal seam in the charqueadas coal field has been considered a target for enhanced coal bed methane production and co 2 sequestration a detailed experimental study of the samples from this seam was conducted at the netl with assistance from the pontificia universidade catolica do rio grande do sul such properties as sorption capacity internal structure of the samples porosity and permeability were of primary interest in this characterization study the samples used were low rank coals high volatile bituminous and sub bituminous obtained from the i2b seam it was observed that the temperature effect on adsorption capacity correlates negatively with as received water and mineral content langmuir co 2 adsorption capacity of the coal samples ranged 0 61 2 09 mmol g the upper i2b seam appears to be overall more heterogeneous and less permeable than the lower i2b seam the lower seam coal appears to have a large amount of micro fractures that do not close even at 11 mpa of confining pressure

three dimensional seismo tectonic imaging an example from the southern california transverse ranges abstract we present a new technique to image deformation 3d seismo tectonic imaging which juxtaposes instantaneous and accumulated deformation by combining earthquake and structural geology data we test the technique using three independent data sets we find concordance between the predicted finite deformation field and related instantaneous deformation surfaces inferred from aftershock and background seismicity data as well as structure imaged by seismic reflection data these results indicate that 1 the 1994 northridge event ruptured a transverse high angle reverse fault linking two ew striking listric thrust systems the pico and oak ridge the rupture terminated on the thrusts and was capped by a north dipping forward breaking imbricate of the santa susana fault 2 the los angeles seismic zone is a region of thrusting associated with the development of a new mountain front forming south of the present one represented by the santa monica anticline the thrust is rooted on a mid crustal ramp forming beneath the los angeles basin we conclude that seismo tectonic imaging by linking earthquake data to an empirically based quantitative description of the finite deformation field provides a new and fruitful method for integrating geological and seismological data

biogenic methane and carbon dioxide generation in organic rich shales from southeastern brazil abstract brazilian shale formations are potential biogenic gas systems that are still poorly understood organic rich shales from ponta grossa devonian parana basin irati permian parana basin and tremembe paleogene taubate basin formations were analyzed in order to evaluate their biogenic methane ch 4 generation potential and to constrain environmental and geological conditions that may affect methanogenic metabolism additionally the generation potential of carbon dioxide co 2 was evaluated in combination with ch 4 to constrain brazilian organic rich shales as sources of greenhouse gas to the atmosphere twenty four shale samples were used for batch incubations in dry and wet conditions and after headspace refilling and acetic acid addition during one year physico chemical parameters such as total organic carbon toc specific surface area and pore volume were characterized in order to understand general geologic controls on ch 4 and co 2 production biogenic gas generation rates in dry tests reached up to 3 17 ml t d milliliter per ton of shale per day for ch 4 and 2 45 10 3 ml t d for co 2 during the first 30 days with wet samples producing about 54 more ch 4 and 151 more co 2 than dry samples headspace refilling did not demonstrate significant changes on production rates while acetic acid addition restarted or increased ch 4 and co 2 production rates in several microcosms shales from the irati formation showed the highest methane production rates for both dry and wet tests with unusual ranges of 13 c ch4 and 13 c co2 that may be linked to hydrocarbon biodegradation the studied shale formations have different pore volume and specific surface area but without significant influence over biogenic methane generation

unified structural representation of the southern california crust and upper mantle we present a new 3d description of crust and upper mantle velocity structure in southern california implemented as a unified structural representation usr the usr is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity vp vs measurements and incorporates the locations and displacement of major fault zones that influence basin structure these basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure which were subsequently iterated and improved using 3d waveform adjoint tomography a geotechnical layer gtl based on vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component the resulting model provides a detailed description of the structure of the southern california crust and upper mantle that reflects the complex tectonic history of the region the crust thickens eastward as moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust deep sedimentary basins and underlying areas of thin crust reflect neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late pliocene to illustrate the impact of this complex structure on strong ground motion forecasting we simulate rupture of a proposed m 7 9 earthquake source in the western transverse ranges the results show distinct basin amplification and focusing of energy that reflects crustal structure described by the usr that is not captured by simpler velocity descriptions we anticipate that the usr will be useful for a broad range of simulation and modeling efforts including strong ground motion forecasting dynamic rupture simulations and fault system modeling the usr is available through the southern california earthquake center scec website http www scec org

the influence of petrological properties and burial history on coal seam methane reservoir characterisation sydney basin australia abstract gas content of coals continuously change throughout their burial histories as a result of the changing state of equilibrium of the coal gas system caused by variations in p t conditions and coal rank to fully evaluate the prospectivity of a coalbed methane resource numerous coal properties burial history p t conditions hydrology and the likelihood of secondary biogenic gas generation need to be considered with respect to gas sorption capacity gas contents and permeability previous studies have given differing interpretations on relationships between rank and maceral composition with sorption capacity the maximum gas storing capacities for sydney basin coals is inversely related to rank up to medium volatile bituminous but a coked contact metamorphosed coal has an elevated capacity comparison of sorption capacities of coals having similar ranks and variable maceral group composition indicate that rank has a dominating effect over any effects of organic matter type for the sydney basin coals the in situ gas contents on average increase with depth up to about 600 m and with further increases in depth to 900 m the gas contents tend to plateau or even decrease such a trend probably is consistent with the combined effects of pressure and temperature on the gas sorption capacity during the geological history r mode cluster analyses of the coal and gas properties yield a positive correlation between gas contents and inertinite abundance this is related to undersaturation of the vitrinite rich coals possibly due to higher permeability and consequent leakage of more gas from vitrinite rich coals than from inertinite rich coals although a large amount of methane and other hydrocarbon gases would have been generated in the sydney basin at maximum burial during the early cretaceous a large proportion of the gas might not have been sorbed within the coal due to limited gas sorption capacities and enhanced diffusivity at high temperatures upon uplift gas that migrated from deeper in the sequence or from shallower biological activity may have been sorbed into the coals without secondary gas replenishment however many of these coals remain significantly undersaturated the areas that contain considerable amounts of secondary biogenic gas are highly prospective for coalbed methane production partly because of the higher gas contents but also because of the higher permeability which is required for access of the microbes and nutrients in meteoric waters to fully evaluate prospectivity of coalbed methane resources numerous coal properties burial history geologic setting and the likelihood of secondary biogenic gas generation need to be considered with respect to gas sorption capacity gas contents and permeability

upper crustal structure of the inner continental borderland near long beach california a new p wave velocity structural model for the inner continental borderland icb region was developed for the area near long beach california it combines controlled source seismic reflection and refraction data collected during the 1994 los angeles region seismic experiment larse multichannel seismic reflection data collected by the u s geological survey 1998 2000 and nearshore borehole stratigraphy based on lateral velocity contrasts and stratigraphic variation determined from borehole data we are able to locate major faults such as the cabrillo palos verdes thums huntington beach and newport inglewood fault zones along with minor faults such as the slope fault avalon knoll and several other yet unnamed faults catalog seismicity 1975 2002 plotted on our preferred velocity structural model shows recent seismicity is located on 16 out of our 24 faults providing evidence for continuing concern with respect to the existing seismic hazard estimates forward modeling of p wave arrival times on the larse line 1 resulted in a four layer model that better resolves the stratigraphy and geologic structures of the icb and also provides tighter constraints on the upper crustal velocity structure than previous modeling of the larse data there is a correlation between the structural horizons identified in the reflection data with the velocity interfaces determined from forward modeling of refraction data the strongest correlation is between the base of velocity layer 1 of the refraction model and the base of the planar sediment beneath the shelf and slope determined by the reflection model layers 2 and 3 of the velocity model loosely correlate with the diffractive crust layer locally interpreted as catalina schist

methane adsorption characteristics of overmature lower cambrian shales of deepwater shelf facies in southwest china abstract the lower cambrian shales of deepwater shelf facies comprise an important part of the marine black shales in southern china in this study twenty four lower cambrian shale samples from southwest china were subjected to analysis of geochemistry pore structure and methane adsorption capacity the samples have total organic carbon toc contents ranging from 0 25 to 11 3 and equivalent vitrinite reflectance eqvro values in the range of 2 51 4 23 specific surface areas determined from n2 adsorption at 77 4 k and specific micropore volumes from co2 adsorption at 273 15 k are in the range of 3 0 38 6 m2 g rock and 2 5 11 4 cm3 kg rock respectively and both of them have positive relationships with toc values the langmuir volumes of these samples at 60 c range from 0 47 cm3 g rock to 5 96 cm3 g rock and are positively correlated with toc values which on the one hand confirms the toc control on methane adsorption capacity and on the other hand also suggests a weak control of thermal maturity on methane adsorption capacity at overmature stages although both specific surface area and specific micropore volume are positively correlated with methane adsorption capacity the latter seems to have a stronger effect and the specific micropore volume determined from subcritical co2 adsorption may be considered as a proxy for the volume of adsorbed methane in dry shales for the extrapolation of measured methane excess adsorption isotherms to geological conditions the use of a constant or varying langmuir volume makes no significant difference with respect to the methane storage capacity of shales when the density of the adsorbed methane is allowed to change with temperature however the absolute methane adsorption quantity at subsurface is obviously dependent on the use of a constant or varying langmuir volume which subsequently affects the estimation of the relative percentages of adsorbed and free methane

the wilmington blind thrust fault an active concealed earthquake source beneath los angeles californiathe wilmington blind thrust fault an active concealed earthquake source beneath los angeles california

earthquake locations in the inner continental borderland offshore southern california the inner continental borderland region offshore southern california is tectonically active and contains several faults that are potential seismic hazards to nearby cities however fault geometries in this complex region are often poorly constrained due to a lack of surface observations and uncertainties in earthquake locations and focal mechanisms to improve the accuracy of event locations in this area we apply new location methods to 4312 offshore seismic events that occurred between 1981 and 1997 in seven different regions within the borderland the regions are defined by either temporal or spatial clustering of seismic activity in the southern california seismic network scsn catalog obtaining accurate locations for these events is difficult due to the lack of nearby stations the limited azimuthal coverage and uncertainties in the velocity structure for this area our location procedure is based on the l 1 norm grid search waveform cross correlation method of shearer 1997 except that we use a nearest neighbor approach astiz et al 2000 to identify suitable event pairs for waveform cross correlation and we explore the effect of different velocity models on the locations and associated station terms in general our relocated events have small estimated relative location errors and the events are more clustered than the scsn catalog locations a quarry on the south tip of catalina island provides a test of our location accuracy and suggests that under ideal conditions offshore events can be located to within 1 to 2 km of their true locations our final locations for most clusters are well correlated with known local tectonic features we relate the 1981 santa barbara island m l 5 3 earthquake with the santa cruz fault the 13 july 1986 oceanside m l 5 3 sequence with the san diego trough fault zone and events near san clemente island with the known trace of the san clemente fault zone over 3000 of the offshore events during this time period are associated with the 1986 oceanside earthquake and its extended aftershock sequence our locations define a northeast dipping fault plane for the oceanside sequence but in cross section the events are scattered over a broad zone about 4 km thick this could either be an expression of fault complexity or location errors due to unaccounted for variations in the velocity structure events that occur near coronado bank in the scsn catalog are relocated closer to the san diego coast and suggest a shallow angle northeast dipping fault plane at 10 to 15 km depth manuscript received 12 february 1999

pore characteristics of wilcox group coal u s gulf coast region implications for the occurrence of coalbed gas abstract pore characteristics of 27 subbituminous coal samples 16 mesh splits from the paleocene eocene wilcox group of north louisiana ouachita and caldwell parishes and south texas zavala county were examined in relation to desorbed gas content coal gas of the wilcox group is primarily biogenic in origin thermogenic gas also may be present in some areas on an as received basis desorbed gas contents range from 0 59 to 1 28 m 3 t for ouachita parish samples 0 37 to 5 19 m 3 t for the caldwell parish samples and 0 02 to 0 06 m 3 t for the zavala county samples for louisiana coal samples micropore surface area and volume are correlated to the desorbed gas content of the wilcox group coal correlations r 0 50 and 0 47 respectively suggesting that micropore surface area and volume are important in terms of gas holding capacity adsorption by micropores appears to be the primary form of gas storage for the louisiana coal samples micropore surface area and volumes also are strongly correlated with the carbon ash yield ratio r 0 97 and 0 94 respectively indicating that gas sorption occurs primarily on organic matter mineral matter appears to reduce the sorption capacity of the coal micropore width decreases with depth r 0 63 probably as the result of increasing pressure and coal rank with depth for the louisiana coal samples mesopore surface area is negatively correlated with the carbon ash yield ratio r 0 70 suggesting that mesopores are preferentially associated with mineral matter average mesopore size is correlated with desorbed gas r 0 80 for the relatively shallow ouachita parish samples average depth 441 m 1446 ft these results suggest that the permeability of the wilcox coal is greater in the shallow stratigraphic intervals compared to deeper intervals additionally mesopore size decreases with depth r 0 80 for ouachita parish coal samples negative correlations of gas with mesopore surface area r 0 74 and mesopore volume r 0 56 strongly suggest that gas is not adsorbed in mesopores and that free gas may be present in larger mesopores macropores or fractures of the wilcox coal results also suggest that moisture in ouachita parish samples is present in mesopores moisture in mesopores may have blocked gas adsorption the low gas south texas samples average depth 313 m 1026 ft are markedly different from the louisiana samples specifically micropore surface area and micropore volume are negatively correlated with desorbed gas for the texas samples r 0 21 and 0 36 respectively geologic or environmental conditions probably were not conducive to the generation or storage of microbial gas in the zavala county coals the geologic settings i e salinity of formation water groundwater recharge permeability of coal of each study area are important factors that need to be considered in relation to the potential for generation or storage of microbial gas in south texas tectonic stress may have led to a reduction in permeability in the wilcox group coal creating an unfavorable environment for the generation or preservation of microbial gas the subbituminous rank of the zavala coals is also too low for significant thermogenic gas generation to have occurred

seafloor fluid seeps on kimki ridge offshore southern california links to active strike slip faulting abstract the kimki ridge fluid seeps are located in western catalina basin about 60 km southwest of the southern california mainland and at a water depth of approximately 1100 m multichannel seismic reflection profiles collected by the u s geological survey usgs in 2014 show acoustic transparency within the kimki ridge suggesting the possibility of fluid seeps and possible sub seafloor fluid pathways subsequent multibeam bathymetric and backscatter intensity data collected during a cooperative university of washington usgs cruise in early 2016 show subtle seafloor buildups with high acoustic backscatter reflectivity in three places along kimki ridge supporting the existence of fluid seepage a remotely operated vehicle rov dive conducted as part of the nautilus exploration program took place in august 2016 to confirm the presence of these previously unknown seeps and document their characteristics as well as those of any associated biological communities two of the three seeps were explored by rov and showed abundant evidence of fluid seepage including characteristic algal mats chemosynthetic clams and authigenic carbonate formation the seeps are comprised of carbonate buildups 1 3 m thick and 300 500 m across within these areas we interpret broad crater like depressions 30 50 m across and 1 2 m deep to be individual seep vents the seep areas appear to be broad zones of diffuse seepage that support chemosynthetic biologic communities however active venting was not observed geochemical analyses of rock samples collected from the seeps indicate microbially driven anaerobic oxidation of methane at or near the sediment water interface seismic reflection profiles show chimney like fluid pathways along the limbs and in the axis of the fold forming kimki ridge and evidence of methane in shallow sediments can be traced into the adjacent catalina basin a system of closely spaced faults located at the axis of the kimki ridge anticline may serve as pathways to allow fluid flow to the seafloor our data are consistent with other studies that suggest that transpression is an important component in the formation and localization of fluid seeps in a strike slip setting implying that seep formation may be a common occurrence at fault stepovers or transpressional bends in strike slip systems

the role of the residual bitumen in the gas storage capacity of mature lacustrine shale a case study of the triassic yanchang shale ordos basin china abstract the role of the residual bitumen in the shale gas storage capacity is investigated for potential terrestrial shale gas reservoirs in the yanchang area southern ordos basin china the upper triassic organic rich yanchang shales comprise of thermally mature chang 7 shale average toc 5 12 wt type i ii1 kerogen tmax 443 458 c ro 0 83 1 02 and relatively mature chang 9 shale average toc 4 40 wt type i ii1 kerogen tmax 443 476 c ro 0 88 1 10 the mineralogy of yanchang shales is dominated by clay minerals average 48 85 and quarts average 31 7 a series of low pressure nitrogen adsorption desorption and high pressure methane sorption experiments were conducted on pretreated fresh drilling cores including three groups of core samples one original group one group extracted by dichloromethane and the other group extracted by trichloromethane selected from yanchang shales to demonstrate the role of the residual bitumen in the shale gas potential low pressure nitrogen sorption method was used to elucidate the effect of the residual bitumen on the pore structure of yanchang shales the results show that the specific surface area and pore volume and pore surface area of shale samples after the extraction greatly increase and their growth was closely related with pores of 30 nm and

meso and microporosity characteristics of miocene lignite and subbituminous coals in the kinik coalfield soma basin w turkey abstract three miocene age coal seams a lower seam km2 subbituminous a middle seam km3 subbituminous and an upper seam kp1 lignite in the kinik coalfield located in the southwesternmost part of the soma basin in western turkey and factors controlling mesoporosity and microporosity characteristics were investigated using low pressure n2 and co2 adsorption techniques respectively in addition this study is also aimed to compare controlling factors on meso and microporosity characteristics of soma basin and late carboniferous zonguldak and late miocene pliocene dombayova basins it is found that distinct differences with regard to meso and microporosity exist among the three seams km2 km3 and kp1 investigated in the kinik coalfield specifically samples from kp1 have greater mesopore surface areas and volumes than those from km3 in addition samples from the upper part of km2 have significantly lower mesopore surface area and volume than from the lower part of this seam and from km3 and kp1 samples from the lower part of km2 have higher meso and micropore surface area and volume values than km3 and kp1 samples the increase in mesopore surface area and volume along with the increase in ash yield toward the lower part of km2 suggests that mesoporosity characteristics in this seam appear to be controlled mainly by mineral matter content the results of this study show that meso and micropore surface area and volume of miocene subbituminous coal km2 in kinik and eynez coalfields of the soma basin have higher values than lignite from the dombayova basin and bituminous coal from the zonguldak basin the differences in mesopore characteristics between the soma and the zonguldak basins could be related to differences in rank in addition the mesoporosity of coal seams in the dombayova basin is more similar to seams in the zonguldak basin these conflicting data suggest that rank might not be a controlling factor on the meso and micropore characteristics of the basins investigated in this paper nevertheless the common presence of structured huminite macerals in the soma basin seems to have caused relatively higher microporosity surface area and volume values whereas the common presence of illite particularly in the lower parts of km2 resulted in higher values of mesopore surface area and volume in the soma basin samples consequently maceral and mineralogical compositions of the studied turkish coals seem to exert major controls on meso and micropore characteristics

records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated auv and rov data offshore palos verdes southern california borderland abstract variations in seabed gradient are widely acknowledged to influence deep water deposition but are often difficult to measure in sufficient detail from both modern and ancient examples on the continental slope offshore los angeles california autonomous underwater vehicle remotely operated vehicle and shipboard methods were used to collect a dense grid of high resolution multibeam bathymetry chirp sub bottom profiles and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation depositional environment grain size of deposits and seafloor morphology in this setting restraining and releasing bends along the active right lateral palos verdes fault create and maintain variations in seafloor gradient holocene down slope flows appear to have been generated by slope failure primarily on the uppermost slope 100 200 m water depth turbidity currents created a low relief

catastrophic floods as a possible cause of organic matter accumulation giving rise to coal parana basin brazil abstract gondwana coals of the rio bonito formation parana basin in southern brazil have generally large ash yields so they could be better called coaly siltstones than coal in addition hummocky cross stratification hcs was found in several coal beds of the rio bonito formation throughout the basin in this formation the frequent and close relationship between facies involving rocks generated by subaqueous gravity flows diamictites and coal itself provides an excellent depositional model based on resedimentary processes acting during deposition as well as a stratigraphic rearrangement of the present units in the state of rio grande do sul southern part of parana basin coals are actually prodelta deposits related to delta front diamictite and conglomeratic sandstone with sigmoidal bedding coal forming organic sediments would come from trees plucked by the floods as indicated by the wood logs floating in the diamictite and reworking of previous peat accumulations every coal layer is covered generally by paleosoil siltstones which represent colonization at the top of the catastrophic flood deposit ending a sedimentary cycle in case of brazilian coal settings several authors recognized deltas fan deltas or braid deltas here is particularly considered the general environment as a salted interior sea lago mare hsu et al sense the present study will refer to three important lithostratigraphic units in the carboniferous early triassic cycle the itarare group the rio bonito formation and the palermo formation although the preferential mode of occurrence of hcs in shallow marine environments indicates a genesis attributed to storm action other causes such as catastrophic flooding have been advanced mutti et al mem sci geol 48 1996 233 described flood dominated deltaic systems with thick conglomerate sandstone and pelitic deposits derived from small to medium scale fluvial systems and mountain bordered drainage basins adjacent to the sea in such settings seaward sediment flow can increase dramatically when weather conditions can supply water in such amounts to produce catastrophic floods thick and laterally extensive sandstone lobes with hcs are the fundamental depositional elements of fan deltas and other river dominated delta systems diamictites and coal together could be a result from jokullhlaups an icelandic term for glacial outburst flood in case of catastrophic floods coming from a melting mountain glacier similar to the columbia river valley scablands 15 000 bp and in modern iceland examples

gas saturation and co2 enhancement potential of coalbed methane reservoirs as a function of depth the influence of moisture temperature coal rank and differential enthalpy on the methane ch4 and carbon dioxide co2 sorption capacity of coals of different rank has been investigated by using high pressure sorption isotherms at 303 318 and 333 k ch4 and 318 333 and 348 k co2 respectively the variation of sorption capacity was studied as a function of burial depth of coal seams using the corresponding langmuir parameters in combination with a geothermal gradient of 0 03 k m and a normal hydrostatic pressure gradient taking the gas content corresponding to 100 gas saturation at maximum burial depth as a reference value the theoretical ch4 saturation after the uplift of the coal seam was computed as a function of depth according to these calculations the change in sorption capacity caused by changing pressure temperature conditions during uplift will lead consistently to high saturation values therefore the commonly observed undersaturation of coal seams is most likely related to dismigration losses into adjacent formations and atmosphere finally we attempt to identify sweet spots for co2 enhanced coalbed methane co2 ecbm production the co2 ecbm is expected to become less effective with increasing depth because the co2 to ch4 sorption capacity ratio decreases with increasing temperature and pressure furthermore co2 ecbm efficiency will decrease with increasing maturity because of the highest sorption capacity ratio and affinity difference between co2 and ch4 for low mature coals

methane and carbon dioxide adsorption diffusion experiments on coal upscaling and modeling numerical modelling of the processes of co2 storage in coal and enhanced coalbed methane ecbm production requires information on the kinetics of adsorption and desorption processes in order to address this issue the sorption kinetics of co2 and ch4 were studied on a high volatile bituminous pennsylvanian upper carboniferous coal vrr 0 68 from the upper silesian basin of poland in the dry and moisture equilibrated states the experiments were conducted on six different grain size fractions ranging from 0 063 to f3 mm at temperatures of 45 and 32 jc using a volumetric experimental setup co2 sorption was consistently faster than ch4 sorption under all experimental conditions for moist coals sorption rates of both gases were reduced by a factor of more than 2 with respect to dry coals and the sorption rate was found to be positively correlated with temperature generally adsorption rates decreased with increasing grain size for all experimental conditions based on the experimental results simple bidisperse modelling approaches are proposed for the sorption kinetics of co2 and ch4 that may be readily implemented into reservoir simulators these approaches consider the combination of two first order reactions and provide in contrast to the unipore model a perfect fit of the experimental pressure decay curves the results of this modeling approach show that the experimental data can be interpreted in terms of a fast and a slow sorption process half life sorption times as well as the percentage of sorption capacity attributed to each of the two individual steps have been calculated further it was shown that an upscaling of the experimental and modelling results for co2 and ch4 can be achieved by performing experiments on different grain size fractions under the same experimental conditions in addition to the sorption kinetics sorption isotherms of the samples with different grain size fractions have been related to the variations in ash and maceral composition of the different grain size fractions d 2004 elsevier b v all rights reserved

the eo permian coal seams of the parana basin in southernmost brazil an analysis of the depositional conditions using sequence stratigraphy concepts the eo permian of the parana basin is studied using sequence stratigraphy the study was based on data acquired from 92 entirely cored and geophysically logged boreholes the study is an applicability test of the conceptual and methodological framework of sequence stratigraphy in the examination of the coal seams of the eo permian rio bonito formation the coal seams were predominantly deposited in a lagoon barrier system linked with a third order transgressive systems tract subdivided into four parasequence sets each set represents a major transgressive pulse in the sedimentary history of the basin

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

a quick analytical approach to estimate both free versus sorbed hydrocarbon contents in liquid rich source rocks free and sorbed low to medium molecular weight thermovaporized hydrocarbons c20 are the main organic compounds released at the temperature range corresponding to the rock eval shale playtmsh0 parameter 100 c 200 c whereas medium and high molecular weight thermovaporized compounds c30 are the predominant components that are thermal released in the temperature range corresponding to the shale play sh1 parameter 200 c 350 c now an analytical methodology is proposed here to predict the quantity of free versus sorbed hydrocarbons still present in any liquid rich sedimentary rock the method compares shale play parameters sh0 and sh1 obtained from both whole rock samples and their corresponding organic matter om concentrates isolated by standard nonoxidizing acid treatments and drying procedures the hydrocarbon content obtained from whole rock hctotal rock is mainly considered as the total amount of free liquid hydrocarbons hcfree and sorbed liquid hydrocarbons hcsorbed om still contained in the investigated rock sample the hydrocarbon content obtained from om concentrates however only reflects the sorbed liquid hydrocarbons in these equations tocrock is the total organic carbon of the rock sample tocom corresponds to the toc content of the om concentrate sample massrock is the initial mass of the rock sample massom is the initial mass of the om concentrate sample fidsignalrocksh0 sh1 is the flame ionization detection fid signal that corresponds to the global surface area under each thermal peak sh0 and sh1 generated by the rock eval fid fidsignalomsh0 sh1 corresponds to the global surface area under each thermal peak sh0 and sh1 measured by the rock eval fid between 100 c and 350 c after the themovaporization of the om concentrate sample free liquid hydrocarbons are finally calculated as the difference between these last two values hcfree e hctotal rock hcsorbed om this paper illustrates the application of this methodology on rock samples derived from the vaca muerta formation argentina along the selected vertical profile the lower rock interval contains approximately 60 of sorbed liquid hydrocarbons whereas the upper sample contains more than 90 free liquid hydrocarbons the parameters freehcsh0 and freehcsh0 sh1 could be used to identify potential producible free liquid hydrocarbons intervals in early exploration campaigns

on the effects of petrographic composition on coalbed methane sorption abstract the effect of petrographic composition on the methane sorption capacity has been determined for a suite of coals and organic rich shales subbituminous and bituminous coals were separated into bright and dull lithotypes by hand picking the methane sorption capacities range between 0 5 and 23 9 cm 3 g at a pressure of 6 mpa the low volatile bituminous canmore coal and the anthracite sample have the highest capacities with the natural coke having the lowest for low rank coals there is no significant difference between bright and dull samples except for one coal with the dull sample having a greater sorption capacity than its bright equivalent for higher rank coals the bright samples have a greater methane capacity than the dull samples and the difference between sample pairs increases with rank the boghead coal samples have the highest sorption capacities in the liptinite rich coals suite and are higher than subbituminous to medium volatile bituminous samples pore size distribution indicates that methane is held as solution gas in liptinite rich coals and by physical sorption in micropores in liptinite poor coals these contrasting processes illustrate that liptinite rich samples need to be independently assessed the positive relationship between reactive inertinite content and methane sorption capacity occurs within the subbituminous to medium volatile bituminous coals because the reactive inertinite is structurally similar to vitrinite and have a higher microporosity than non reactive inertinite reactivity of inertinite should be assessed in cbm studies of dull coals to provide a better understanding of petrographic composition effects on methane capacity

the effect of moisture on the methane adsorption capacity of shales a study case in the eastern qaidam basin in china this study investigated the effects of moisture on high pressure methane adsorption in carboniferous shales from the qaidam basin china the shale characteristics including the organic inorganic compositions and pore structure volume and surface distribution were obtained using various techniques gibbs adsorption measurements were performed over a pressure range up to 6 mpa and temperatures of 308 15 k on dry samples and moisture equilibrated samples to analyze the correlations between organic inorganic matter pore structure and moisture content on the methane sorption capacity compared to dry samples the sorption capacity of wet samples 0 44 2 52 of water content is reduced from 19 7 5 3 to 36 1 6 1 langmuir fitting is conducted to investigate moisture dependent variations of adsorbed methane density langmuir pressure and volume by combining the pore volume and surface distribution analyses our observations suggested that the main competition sites for ch4 h2o covered pores of approximately 2 7 nm whereas the effective sites for methane and water were predominantly distributed within smaller 10 nm respectively regarding the compositional correlations the impact of moisture on the amount of adsorbed methane shows a roughly linearly decreasing trend with increasing toc content ranging from 0 62 to 2 88 whereas the correlation between the moisture effect and various inorganic components is more complicated further fitting results indicate that illite smectite mixed formations are closely related to the methane capacity whereas the illite content show an evident connection to the pore structural volume and surface variations in the presence of moisture

characterization of methane adsorption on overmature lower silurian upper ordovician shales in sichuan basin southwest china experimental results and geological implications abstract a series of methane adsorption isotherms were measured at 35 4 c 50 6 c and 65 4 c at pressures up to 15 0 mpa for eight dried overmature lower silurian upper ordovician shale samples collected from the sichuan basin with toc values in the range of 1 87 5 74 the measured maxima of excess adsorption capacity of methane range from 1 25 to 2 50 cm 3 g rock at 65 4 c the maxima are slightly enhanced at 35 4 c but all are positively correlated with total organic carbon toc both the supercritical dubinin radushkevich sdr and langmuir based excess adsorption models were found to represent the experimental excess adsorption isotherms equally well within the experimental range the temperature dependent densities of adsorbed methane resulting from the parameter fit of the sdr based excess adsorption model are in the range of 297 415 mg cm 3 for the langmuir based excess adsorption model the adjusted densities range from 386 mg cm 3 to 1027 mg cm 3 and most of them are much larger than the liquid density of methane at its boiling point 424 mg cm 3 nevertheless the maxima of absolute methane adsorption capacity fitted by both models are not significantly different and are linearly correlated one of the contributors to the uncertainty of the gas in place estimation in geological conditions is the inconsistent utilization of experimental excess sorption data as absolute sorption values particularly at high pressures however the choice of adsorption model itself langmuir or sdr based and the fitting procedure assuming either constant or temperature dependent adsorbed phase density and maximum sorption capacity do not significantly affect the estimated gips for the geological system studied here with depths of less than 4000 m

large enigmatic crater structures offshore southern california summary digital mosaics of swath and conventional bathymetry data reveal large distinct near circular crater structures in the inner continental borderland offshore southern california two have maximum crater diameters that exceed 30 km and a third has a crater diameter of approximately 12 km all three features exhibit the morphology of large complex craters raised outer rim ring moat and central uplift yet their exact origin remains a mystery preliminary analyses of available seismic gravity and magnetic data over these structures reveal both similarities and distinct differences in geometry structure and geophysical signature to known impact sites all three crater structures however occur within the catalina terrane a highly extended volcanic and metamorphic province floored by catalina schist basement a likely alternative origin may thus involve explosive volcanism caldera collapse and resurgent magmatism and or possibly plutonism and schist remobilization associated with the catalina terrane no single model for crater formation whether impact caldera or pluton fully accounts for all of the present observations regarding the morphology internal structure and known geology of these near circular features timing of crater formation post dates the initial rifting and rotation of the western transverse ranges and appears to predate major right slip along the san clemente and san diego trough fault systems or approximately 18 to 16 ma regardless of their origin these complex craters represent some of the largest structures of their kind in western north america and provide a unique opportunity to better understand the development of unusual crater structures in a submarine environment

geological controls on coalbed methane reservoir capacity and gas content the influence of coal composition and rank on coalbed methane reservoir capacity gas content and gas saturation have been investigated for a series of australian canadian and united states coals globally there is no or little correlation between coal rank and methane adsorption capacity as commonly assumed although in particular basins there are general trends with rank and composition micropore1 capacity and surface area determined from low pressure carbon dioxide adsorption isotherms 0 c decrease and then increase with rank passing through a minimum in the high volatile bituminous coal rank there is no consistent variation in modal micropore size or size distribution with rank for suites of isorank coals there is a poor permian bulli and wongawilli seams australia to good positive correlation gates formation coal seams lower cretaceous canada between vitrinite content and methane adsorption capacity dry ash free and as received bases for each isorank coal suite there is a good correlation between micropore capacity and abundance of vitrinite and high pressure methane adsorption capacity comparison of coals of similar composition but from different isorank suites indicates however that the coals with the highest methane adsorption capacity do not necessarily have the highest micropore capacity such results are counterintuitive most pore volume available for methane adsorption is generally assumed to be microporosity it is suspected that moisture prevents methane from accessing some microporosity or competes with methane for adsorption space carbon dioxide micropore capacity which is performed on a dry basis may thus not reflect the microporosity available for gas adsorption in moisture equilibrated coals alternatively because of differing physical and chemical properties of carbon dioxide and methane apparent microporosity available to carbon dioxide due to greater energy of adsorption may not be available to methane total desorbed gas from canister analyses of sydney basin australian coals suggests that most coals are under saturated for a small data set the degree of saturation is negatively correlated with permeability r 0 78 suggesting preferential gas leakage from the higher permeability coals which are vitrite rich some degree of under saturation is probably the result of increased reservoir capacity as a consequence of uplift of the coal seams and thus lower temperatures following gas generation rates of desorption are correlated with total gas content r 0 79 but do not correlate with rank or any compositional parameter

mineralogy and leaching characteristics of beneficiated coal products from santa catarina brazil abstract petrographic mineralogical and geochemical studies have been carried out on beneficiated coal products from mines and preparation plants in the santa catarina basin southern brazil to investigate the range of characteristics exhibited by the materials and the potential impact of their stockpiling and storage on the environment the coals contain varying proportions of vitrinite and inertinite macerals and have vitrinite reflectance values ranging from 0 44 to 1 38 with the exception of one material blended with peat from an external source they have relatively high percentages of ash 30 58 and mineral matter 36 66 the mineral matter consists mainly of clay minerals kaolinite illite and illite smectite together with 15 25 quartz up to 10 feldspar up to 5 calcite and or dolomite and up to 5 pyrite and around 1 anatase and or rutile bassanite is also present in low temperature ash derived from the coals mainly derived from interaction of ca and s associated with the organic matter jarosite is formed by pyrite oxidation in coals that have been exposed in stockpiles for extended periods most of the trace elements in most of the coals have higher concentrations than average values for world coals generally probably due to the relatively high mineral matter content a lower ash product representing a blend of coal and peat has similar to lower concentrations of most elements but higher concentrations of b ba be cd ge and mn which may be associated with the peat component interaction of relatively fresh coals with water in laboratory tests produces leachates with near neutral to mildly acid ph values but leaching of oxidized jarosite bearing coal produces a strongly acid leachate with higher concentrations of cd co cu ni and zn leachates derived from coals in which the pyrite has been oxidized during storage would thus be expected to have a more adverse environmental impact than leachates derived from coals in which such oxidation has not had an opportunity to develop

experimental study of swelling of organic rich shale in methane abstract gas is stored in shale mainly in free and adsorbed phases since a significant amount of gas in the shale is adsorbed to the organic matter and or clay minerals it is possible that gas adsorption will induce shale swelling which may then has an impact on the gas flow behavior in the shale thus its gas production in this work strain behavior was studied in two gases helium and methane at different pore pressures under constant hydrostatic pressure at 20 mpa on two shale samples the results show that porosity and volumetric strain are functions of gas pressure and the strain is larger in methane than helium demonstrating gas adsorption induced swelling for the shale samples the calculated methane adsorption induced swelling strain is at a magnitude of 0 1 volumetrically with pressure at 10 mpa for the shale samples studied the adsorption induced shale swelling strain shows a langmuir like relationship with pressure and is proportional to the amount of methane adsorbed the results also show slight anisotropic strain behavior between the two directions of parallel and perpendicular to the bedding and strain hysteresis with methane in and out of the shale the gas adsorption induced swelling may influence gas flow in gas shale thus more research in this topic is warranted

miocene rifting in the los angeles basin evidence from the puente hills half graben volcanic rocks and p wave tomography formation of the puente hills half graben in the northeastern los angeles basin and eruption of the glendora and el modeno volcanics 16 14 ma help to define the timing of extension in the basin normal faulting on the proto whittier fault ca 14 ma established the puente hills half graben in which sedimentary strata accumulated between ca 14 and 10 ma and into which diabase sills intruded north south contraction began to invert the puente hills half graben ca 7 ma leading to formation of the puente hills anticline and the whittier fault our high resolution three dimensional p wave velocity model shows two anomalous higher velocity 6 63 km s bodies at depths between 9 and 18 km which we attribute to dioritic plutons named here for whittier narrows and el modeno the stocklike whittier narrows pluton could have been a source for the glendora volcanics and the diabase sills in the puente hills half graben the sill shaped el modeno pluton was a likely source for the el modeno volcanics the northwesterly alignment of the plutons may mark the location of the northeastern los angeles basin rift boundary which is associated with the clockwise rotation of the western transverse ranges three active faults the elysian park blind thrust the puente hills blind thrust and the whittier fault converge on the whittier narrows pluton which may have played a role in their location and segmentation

crustal structure of the borderland continent transition zone of southern california adjacent to los angeles we use data from the onshore offshore component of los angeles region seismic experiment larse to model the broad scale features of the midcrust to upper mantle beneath a north south transect that spans the continental borderland in the los angeles california region we have developed an analysis method for wide angle seismic data that consists primarily of refractions lacks near offset recordings and contains wide gaps in coverage although the data restrict the analysis to the modeling of broad scale structure the technique allows one to explore the limits of the data and determine the resolving power of the data set the resulting composite velocity model constrains the crustal thickness and location and width of the continent borderland transition zone we find that the mid to lower crust layer velocities of the inner borderland are slightly lower than the corresponding layers in the average southern california crust model while the upper mantle velocity is significantly higher the data require the moho to deepen significantly to the north we constrain the transition zone to initiate between the offshore slope and the southwest los angeles basin if the inner borderland crust is 22 km thick then the transition zone is constrained to initiate within a 2 km wide region beneath the southwest los angeles basin and have a width of 20 25 km the strong coherent and continuous pn phase suggests the moho is coherent and laterally continuous beneath the inner borderland and transition zone the inner california borderland seems to be modified and thickened oceanic crust with the oceanic upper mantle intact beneath it

geophysical evidence for miocene extension and mafic magmatic addition in the california continental borderland the california continental borderland is a key region for understanding the effect on crustal structure of tectonic processes associated with the initiation and elongation of the san andreas transform system because the borderland lies near the point where the pacific farallon spreading system first encountered the north american plate margin whereas the central and northern california margins have been extensively investigated by geophysical surveys in recent years the crustal structure of the borderland particularly the outer borderland has received relatively little attention this paper presents three gravity models that stretch from the pacific ocean floor to shore they provide new evidence that the crust of the entire california continental borderland has been extended and infiltrated by mafic melt since early miocene time the gravity models were constructed from interpretations of nearly 750 km of seismic reflection data seismic refraction studies and geologic maps thus minimizing the nonuniqueness of the method the evidence for extension in the models is that the crust of the accretionary complex and forearc basin that make up the borderland is only 22 km thick 35 thinner than comparable crustal sections in central and northern california extension could well have been accommodated by eastward flow of accretionary complex material during middle miocene formation of a metamorphic core complex in the inner borderland the gravity models also show that the accretionary complex is 100 200 kg m 3 more dense than commonly observed to the north this density difference may result from influx of basaltic melts due to mantle upwelling at the rivera triple junction and beneath the highly extended inner borderland the borderland models permit the occurrence of a discrete mafic layer that forms the base of the crust as is seen along the central and northern california coast but do not require such a layer9s presence anywhere except immediately inland of the shelf slope break

geochemical characterization and methane adsorption capacity of overmature organic rich lower cambrian shales in northeast guizhou region southwest china abstract the niutitang shale lower cambrian is another set of organic rich shale in addition to the lower silurian longmaxi shale in southwest china in this study methane adsorption capacities of both whole rock and organic matter were investigated based on adsorption isotherms measured at various temperatures 40 120 c and pressures up to 35 0 mpa for eleven niutitang shale samples collected from northeast guizhou province the investigated samples cover a wide range of toc contents varying from 1 8 to 11 3 with an average equivalent vitrinite reflectance eqvro value of approximately 4 0 their bet specific surface areas and micropore volumes range from 11 1 to 26 2 m2 g rock and between 4 3 and 11 2 cm3 kg rock respectively both of which are positively correlated to toc content model fitted methane maximum absolute adsorption capacities n range from 1 80 to 5 85 cm3 g rock at 60 c and are found to largely increase with increasing toc this suggests that the toc control on methane adsorption capacity obtained by other authors for other shales with relative low thermal maturity levels may be extended to a very high thermal maturity level e g eqvro 4 0 the methane adsorption capacity of organic matter om in our shale samples however is somehow reduced as compared to the lower silurian longmaxi shale and other shales that display eqvro values smaller than 3 0 indicating thermal maturity may adversely affect methane adsorption capacity of shales when it evolves to be eqvro 4 0 nevertheless this reduction in adsorption capacity may be compensated by the very enrichment of om in the niutitang shale in addition a higher thermal maturity level results in a lower langmuir pressure value which makes it more difficult for methane desorption at reservoirs conditions the temperature dependency of adsorption parameters was also investigated which could be used to predict the changes of methane adsorption with burial depth under geological conditions beyond experimental temperature and pressure ranges

integrated monitoring of mountain glaciers as key indicators of global climate change the european alps the internationally recommended multi level strategy for monitoring mountain glaciers is illustrated using the example of the european alps where especially dense information has been available through historical times this strategy combines in situ measurements mass balance length change with remote sensing inventories and numerical modelling it helps to bridge the gap between detailed local process oriented studies and global coverage since the 1980s mass balances have become increasingly negative with values close to 1 m w e a 1 during the first 5 years of the 21st century the hot dry summer of 2003 alone caused a record mean loss of 2 45 m w e roughly 50 above the previous record loss in 1998 more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long term averages since the end of the little ice age and other extended periods of glacier shrinkage during the past 2000 years it can be estimated that glaciers in the european alps lost about half their total volume roughly 0 5 a 1 between 1850 and around 1975 another 25 or 1 a 1 of the remaining amount between 1975 and 2000 and an additional 10 15 or 2 3 a 1 in the first 5 years of this century

natural fracture cleat and strong adsorption impact on low oil and condensate retention in the carboniferous shales and coals of the western black sea basin of turkey total organic carbon toc values of the carboniferous shales and coals of the western black sea basin of turkey range from 0 72 to 71 52 wt with an average of 32 3 wt and generation potential chance from 0 33 to 184 64 with an average of 82 47 mg hc g rock hydrogen index hi values of the shales and coals range from 24 to 384 mg hc g toc the hi versus pyrolysis temperature at the maximum rate of kerogen conversion plot indicates that the organic matter is type ii iii the calculated vitrinite reflectance equivalent values of the shales and coals range from 0 63 to 1 32 thus the shales and coals of the carboniferous formations are represented by immature effective oil and condensate generation windows the shales and coals of the alacaagzi formation contain high quartz and lower clay oil saturation index osi values of the shales and coals have been calculated as being 0 7 and 12 mg hc g toc indicating possible lack of producible oil and condensate the osi values are lower than those of other coal bearing and marine shales of the world first strong adsorption capacity may be a cause of the lower oil and condensate retention second faults natural fractures and cleats related fluid flows may be important factors in these lower osi ratios the extensional collisional and inverse tectonic stages and diagenetic processes of coalification formed multiple interconnected faults natural opening mode fractures and cleats in the shales and coals thus 15 coalbed methane exploration wells failed to produce any economical coalbed methane

oceanside and thirtymile bank blind thrusts implications for earthquake hazards in coastal southern california we define an active blind thrust system in offshore southern california that extends from los angeles south to the united states mexico international border these blind thrusts formed by tectonic inversion of miocene extensional detachments we attribute the 1986 oceanside ml 5 3 earthquake local uplift of marine terraces seafloor fold scarps and observed geodetic convergence to motion on these faults single and multisegment fault rupture scenarios suggest the potential for large m 7 1 7 6 but infrequent earthquakes that would affect the los angeles and san diego metropolitan areas

geological models of gas in place of the longmaxi shale in southeast chongqing south china abstract gas in place gip is one of the primary controlling factors in shale gas production but studies examining gip have been lacking for the lower silurian longmaxi shale in south china in the present study a suite of longmaxi shale samples was collected from an exploratory well in southeast chongqing south china and the adsorption parameters were fitted using a supercritical dubinin radushkevich sdr model based on the high pressure methane adsorption experiment data for the samples the results show that the adsorbed phase density and the adsorbed gas capacity of the samples have a positive correlation with the content of total organic carbon toc but a negative correlation with temperature combined with the geological characteristics of the longmaxi shale in southeast chongqing gip models were constructed under three different fluid pressure conditions the absolute adsorbed amount of the samples increases and later decreases with increasing depth with a maximum corresponding to depths between 800 and 1200 m the fluid pressure coefficient has no obvious effect on the absolute adsorbed amount when burial depth is over 2000 m but controls the free gas content overpressure primarily increases the free gas content and thus increases the total gas content the free gas content of the longmaxi shale in the pengshui block is reduced to 47 58 of that in the fuling block which is the main reason for its low gas production further exploration of the longmaxi formation should be expanded to deeper burial shales in the eastern area of southeast chongqing