the central and northern appalachian basin a frontier region for coalbed methane development abstract the appalachian basin is the world s second largest coalbed methane cbm producing basin it has nearly 4000 wells with 1996 annual production at 147 8 billion cubic feet bcf cumulative cbm production is close to 0 9 trillion cubic feet tcf the black warrior basin of alabama in the southern appalachian basin including a very minor amount from the cahaba coal field accounts for about 75 of this annual production and about 75 of the wells and the remainder comes from the central and northern appalachian basin the southwest virginia coal field accounts for about 95 of the production from the central and northern parts of the appalachian basin production data and trends imply that several of the appalachian basin states except for alabama and virginia are in their infancy with respect to cbm development total in place cbm resources in the central and northern appalachian basin have been variously estimated at 66 to 76 trillion cubic feet tcf of which an estimated 14 55 tcf 20 is technically recoverable according to a 1995 u s geological survey assessment for comparison in the black warrior basin of the 20 tcf in place cbm resources 2 30 tcf 12 is technically recoverable because close to 0 9 tcf of cbm has already been produced from the black warrior basin and the proved reserves are about 0 8 tcf for 1996 energy information administration eia 1997 u s crude oil natural gas and natural gas liquids reserves 1996 annual report u s department of energy doe eia 0216 96 145 pp these data imply that the central and northern appalachian basin could become increasingly important in the appalachian basin cbm picture as cbm resources are depleted in the southern appalachian basin black warrior basin and cahaba coal field cbm development in the appalachian states could decrease the eastern u s a s dependence on coal for electricity cbm is expected to provide over the next few decades a virtually untapped source of unconventional fossil fuel in the appalachian states where the cbm resources are large and the demand for cleaner fossil fuel energy is high

origin of minerals in joint and cleat systems of the pottsville formation black warrior basin alabama implications for coalbed methane generation and production coalbed methane is produced from naturally fractured strata in the lower pennsylvanian pottsville formation in the eastern part of the black warrior basin alabama major fracture systems include orthogonal fractures which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and less commonly cleats in coal joint fill calcite postdates most pyrite and is a weakly ferroan coarse crystalline variety that formed during a period of uplift and erosion late in the burial history pyrite forms fine to coarse euhedral crystals that line joint walls or are complexly intergrown with calcite stable isotope data reveal large variations in the carbon isotope composition of joint and cleat fill calcite 10 3 to 24 3 peedee belemnite pdb but only a relatively narrow range in the oxygen isotope composition of this calcite 16 2 to 4 1 pdb negative carbon values can be attributed to 13c depleted co2 derived from the oxidation of organic matter and moderately to highly positive carbon values can be attributed to bacterial methanogenesis assuming crystallization temperatures of 2050c most joint and cleat fill calcite precipitated from fluids with 18o ratios ranging from about 11 to 2 standard mean ocean water smow uplift and unroofing since the mesozoic led to meteoric recharge of pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned southeastern margin of the basin influxes of fresh water into the basin via faults and coalbeds facilitated late stage bacterial methanogenesis which accounts for the high gas content in coal and the carbonate cementation of joints and cleats diagenetic and epigenetic minerals can affect the transmissivity and storage capacity of joints and cleats and they appear to contribute significantly to interwell heterogeneity in the pottsville formation in highly productive coalbed methane fields joint and cleat fill calcite have strongly positive 13c values whereas calcite fill has lower 13c values in fields that are shut in or abandoned petrographic analysis and stable isotope geochemistry of joint and cleat fill cements provide insight into coalbed methane reservoir quality and the nature and extent of reservoir compartmentalization which are important factors governing methane production

seal evaluation and confinement screening criteria for beneficial carbon dioxide storage with enhanced coal bed methane recovery in the pocahontas basin virginia abstract the geological storage of carbon dioxide in appalachian basin coal seams is one possible sink for sequestration of greenhouse gases with the added benefit of enhanced coal bed methane ecbm recovery the pocahontas basin part of the central appalachian basin of southwestern virginia is a major coal bed methane cbm province with production mostly from coal beds in the lower pennsylvanian pocahontas and new river formations as part of the southeast regional carbon sequestration partnership s phase ii research program a co 2 injection demonstration well was installed into lower pennsylvanian coal bed methane producing strata in southwest virginia samples of siliciclastic lithologies above coal beds in this oakwood field well and from several other cores in the nora field were taken to establish a baseline of the basic confinement properties of overlying strata to test seal competency at local and regional scales strata above cbm producing coal beds in the pocahontas and new river formations consist of dark gray shales silty gray shales heterolithic siltstones sandstones and shales lithic sandstones and quartzose sandstones standard measurements of porosity permeability and petrography were used to evaluate potential leakage hazards and any possible secondary storage potential for typical lithologies both lithic and quartz rich sandstones exhibit only minor porosity with generally low permeability 2 ecbm traps one of the most promising confining intervals above the major coal bed methane producing interval is the hensley shale member analyses of 1500 geophysical logs in southwest virginia indicate that this unit is moderately thick 50 ft 15 m laterally continuous 3000 km 2 and a homogenous shale which coarsens upward into siltstone and sandstone or is truncated by sandstone calculations from two mercury injection capillary porosimetry tests of the shale indicate that a displacement entry pressure of 207 psi 1427 kpa would generate an estimated seal capacity of 1365 ft 416 m of co 2 before buoyant leakage scanning electron microscopy indicates a microfabric of narrow pore throats between quartz grains floating in a clay matrix modeled median pore throat size between micro fabric matrix grains for the shale is estimated at 0 26 m these characteristics indicate that the shale where fractures and joints are limited would be an adequate regional confining interval for deeper co 2 storage with ecbm

volumetric analysis of complex lunar craters implications for basin ring formation the transition in hypervelocity impact structures from complex craters to basins is defined by a transition in uplifted central features from peaks to peak rings volumetric and morphologic analyses of the central peaks in complex lunar craters are combined with subsurface data from terrestrial complex impact structures in an effort to characterize the crater to basin transition central peak volumes in lunar craters with rim diameters drc 80 km central peak volume is relatively reduced and a second power law relationship is defined the relative reduction in peak volume in craters with drc 80 km is associated with a relative decrease in peak height and is accompanied by the development of a concentric zone of enhanced floor roughening studies of terrestrial complex impact structures suggest that the amount of uplifted material as judged from its depth of origin continues to increase with increasing rim diameter this suggests that a redistribution of uplifted material away from a centralized peak may occur in the larger craters the volumetric and morphologic changes described occur over a rim diameter range of 51 80 km far below the previously proposed range for the crater to basin transition drc 140 175 km evidence is presented to support a crater to basin transition beginning at drc 51 80 km characterized by a relative reduction in central peak volume and the development of rings of floor roughening which are suggested to be precursors of peak ring development

magmatism and petroleum exploration in the brazilian paleozoic basins abstract petroleum exploration in the paleozoic sedimentary basins of brazil has proven very challenging for explorationists except for the solimoes basin in which transcurrent tectonism formed prospective structural highs brazilian paleozoic basins lack intense structural deformation and hence the detection and prospecting of place is often difficult magmatic intrusive and associated rocks in all these basins have traditionally been considered heat sources and hydrocarbon traps the role of tholeiitic basic dikes in the generation migration and accumulation of petroleum in the anhembi oil occurrence sao paulo state is discussed herein it follows that similar geological settings in other paleozoic basins can be regarded as promising sites for oil accumulation that warrant investigation via modern geological and geophysical methods

stratigraphy and structure of coalbed methane reservoirs in the united states an overview stratigraphy and geologic structure determine the shape continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane coal in the united states is dominantly of pennsylvanian cretaceous and tertiary age and to date more than 90 of the coalbed methane produced is from pennsylvanian and cretaceous strata of the black warrior and san juan basins investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones coalbed methane production in the united states is mainly from foreland and intermontane basins containing diverse compressional and extensional structures balanced structural models can be used to construct and validate cross sections as well as to quantify layer parallel strain and predict the distribution of fractures folds and faults influence gas and water production in diverse ways however interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict

investigating the transition from central peak to peak ring basins using central feature volume measurements from the global lunar dtm 100 m 1 several theories have been suggested to explain the transition from peak to peak ring crater morphology in order to explore the transition and assess the currently advocated peak ring formation theories we have collected measurements of central feature volumes and heights for relatively fresh lunar impact craters we employed the global lunar dtm 100 m which has the vertical precision and spatial coverage necessary to accurately measure peak and peak ring volumes in more craters than previously possible the similarity in both trend and magnitude of peak and peak ring volumes suggests that peak ring formation is closely related to the development of central peaks as crater size increases our data thus lends support to those peak ring formation theories involving peak collapse

structural control of coalbed methane production in alabama abstract thin skinned structures are distributed throughout the alabama coalbed methane fields and these structures affect the production of gas and water from coal bearing strata extensional structures in deerlick creek and cedar cove fields include normal faults and hanging wall rollovers and area balancing indicates that these structures are detached in the pottsville formation compressional folds in gurnee and oak grove fields by comparison are interpreted to be detachment folds formed above decollements at different stratigraphic levels patterns of gas and water production reflect the structural style of each field and further indicate that folding and faulting have affected the distribution of permeability and the overall success of coalbed methane operations area balancing can be an effective way to characterize coalbed methane reservoirs in structurally complex regions because it constrains structural geometry and can be used to determine the distribution of layer parallel strain comparison of calculated requisite strain and borehole expansion data from calliper logs suggests that strain in coalbed methane reservoirs is predictable and can be expressed as fracturing and small scale faulting however refined methodology is needed to analyze heterogeneous strain distributions in discrete bed segments understanding temporal variation of production patterns in areas where gas and water production are influenced by map scale structure will further facilitate effective management of coalbed methane fields

robust smooth magnetotelluric transfer functions jimmy c larsen randall l mackie 2 adele man e l l a adolfo fiordelisi4 and shirley rieven2 pacific marine environmental laboratory national oceanic and atmospheric administration 7600 sand point way ne seattle wa 981 15 0070 usa wassachusetts institute of technology 42 carleton street cambridge m a 02142 usa cnr international institute for geothermal research piazza soljerino 2 pisa 56126 italy enel esplorazione mineraria via andrea pisano 120 pisa 56122 italy

magnetotellurics as a modeling tool in the extensive magmatic context of parana basin brazil parana basin is a huge oval shaped basin covering the southern portion of brazil and parts of argentina paraguay and uruguay with an area of more than 1 700 000 km2 figure 1 hydrocarbon exploration in parana basin has been a challenge due to the world s second most extensive inshore flood basalt complex overlying the paleozoic sedimentary rocks figure 1 which in turn are extensively intruded by swarms of diabase dikes and sills making seismic imaging a difficult task the basin itself represents approximately one half of the sedimentary rock volume of onshore brazilian basins and is still underexplored no major discovery for oil or gas has been made to date

coalbed methane resources of the appalachian basin eastern usa abstract in 2002 the u s geological survey usgs assessed the technically recoverable undiscovered coalbed gas resources in the appalachian basin and black warrior basin assessment provinces as about 15 5 trillion cubic feet although these resources are almost equally divided between the two areas most of the production occurs within relatively small areas within these provinces where local geological and geochemical attributes have resulted in the generation and retention of large amounts of methane within the coal beds and have enhanced the producibility of the gas from the coal in the appalachian basin coalbed methane cbm tests are commonly commercial where the cumulative coal thickness completed in wells is greater than three meters 10 ft the depth of burial of the coal beds is greater than 100 m 350 ft and the coal is in the thermogenic gas window in addition to the ubiquitous cleating within the coal beds commercial production may be enhanced by secondary fracture porosity related to supplemental fracture systems within the coal beds in order to release the methane from microporus coal matrix most wells are dewatered prior to commercial production of gas two total petroleum systems tps were defined by the usgs during the assessment the pottsville coal bed gas tps in alabama and the carboniferous coal bed gas tps in pennsylvania ohio west virginia eastern kentucky virginia tennessee and alabama these were divided into seven assessment units of which three had sufficient data to be assessed production rates are higher in most horizontal wells drilled into relatively thick coal beds than in vertical wells recovery per unit area is greater and potential adverse environmental impact is decreased

regional magnetotelluric surveys in hydrocarbon exploration parana basin brazil the magnetotelluric geophysical method has been used effectively as a hydrocarbon exploration tool in the intracratonic parana basin of south america the parana basin has an area of about 1 200 000 km2 463 000 mi2 extending over portions of brazil paraguay uruguay argentina and bolivia the paleozoic marine sedimentary rocks in the parana basin are covered by the world s most extensive flood basalt complex making geophysical exploration extremely difficult although modern seismic techniques recently applied are achieving good results in some areas the 1 2 km 3 300 6 600 ft thick surface basalts and buried diabase sills pose no problem for the magnetotelluric method because the natural electromagnetic fields used as the energy source pass easily through the basalt data for the regional study were taken on six profiles with soundings spaced 8 to 15 km 5 to 9 mi apart the magnetotelluric sounding data outline a linear uplift known as the ponta grossa arch this major structural feature cuts across the northeast trending intracratonic basin almost perpendicularly and is injected with numerous diabase dikes although its character is reasonably well known in the shallow eastern parts of the basin it is poorly delineated in the deeper parts of the basin where promising natural gas zones have been tested in several wells in the survey area mt interpretations show that basalts have aggregate thickness of as much as 2 km 6 600 ft and basement may be as much as 6 km 20 000 ft below the surface over most of the basin the basalts are covered by upper cretaceous to holocene continental sediments of a few hundred meters thickness and are underlain by 2 to 4 km 6 600 to 13 100 ft thick paleozoic sediments with possible hydrocarbon potential the ponta grossa arch is interpreted to be the failed arm of a triple rift system that formed during the separation of the african and south american continents shales of the devonian ponta grossa formation are important parana basin source rocks for hydrocarbons as are several permian units significant electrical contrasts occur between the permian sediments and older units so that magnetotelluric measurements can give an indication of the regional thickness of the permian and younger sediments to aid in interpreting hydrocarbon migration patterns and possible trap areas

geochemistry and origin of some natural gases in the plateau province central appalachian basin pennsylvania and ohio the appalachian plateau is a large elongate structural basin in the western part of the central appalachians in western pennsylvania and eastern ohio the plateau is a mostly wet gas mean c sub 2 c sub 5 c sub 1 c sub 5 6 08 district which has produced approximately one third of all the natural gas produced in the entire appalachian basin we sampled gases from 22 wells and 5 cores to determine the possible utility of stable isotope geochemistry for interpreting the origin of the gases and correlating them with their probable sources methane delta sup 13 c and delta c and delta d values range from 55 1 to 27 24 and 303 to 150 respectively corresponding ethane and propane values of selected samples range from 41 79 to 29 61 and 38 21 to 26 71 several gas samples exhibit isotopic reversals amoung the c sub 1 to c sub 3 hydrocarbons the isotope data provide some potential insight into the origin of these gases and the timing and direction of their migration into different reservoirs with few exceptions the gases we analyzed are secondary i e mixtures of gases varying origins or primary gases original gas from a single active source rock which were altered by geological processes most samples originated as associated thermogenic gases generated frommore types i ii kerogens at source rock maturities ranging from early mature to overmature coalbed gases and some upper devonian gases appear to be mixtures of thermogenic and microbial hydrocarbons we interpret several other gases from various cambrian through devonian reservoirs as mixtures of thermogenic gases less

hydrocode simulations of chicxulub crater collapse and peak ring formation we use hydrocode modeling to investigate dynamic models for the collapse of the chicxulub impact crater our aim is to integrate the results from numerical simulations with kinematic models derived from seismic reflection and wide angle velocity data to further our understanding of the formation of large impact craters in our simulations we model the collapse of a 100 km diameter bowlshaped cavity formed in comprehensively fractured crustal material to facilitate wholesale collapse we require that the strength of the target be significantly weakened in the present model we achieve this using acoustic fluidization where strong vibrations produced by the expanding shock wave cause extreme pressure fluctuations in the target at times and positions where the overburden pressure is sufficiently counteracted the frictional resistance is reduced enabling the rock debris to flow our simulations produce a collapsed crater that contains most of the features that we observe in the seismic data at chicxulub in particular we observe a topographic peak ring formed as material that is originally part of the central uplift collapses outward and is thrust over the inwardly collapsing transient crater rim this model for peak ring generation has not been previously demonstrated by numerical simulations and predicts that the peak ring is composed of deeply derived material and that the stratigraphy within the peak ring is overturned c 2002 elsevier science usa

the scaling of complex craters the empirical relation between the transient crater diameter dg and final crater diameter dr of complex craters and basins is estimated using cumulative terrace widths central uplift diameters continuous ejecta radii and transient crater reconstructions determined from lunar and terrestrial impact structures the ratio dg dr is a power law function of dr decreasing uniformly from unity at the diameter of the simple complex crater morphology transition to about 0 5 for large multiring basins like imbrium on the moon the empirical constants in the dg dr relation are interpreted physically to mean that the position of the final rim relative to the transient crater and hence the extent of collapse is controlled or greatly influenced by the properties of the zone of dissociated material produced by the impact shock the continuity of the dg dr relation over the entire spectrum of morphologic types from complex craters to multiring basins implies that the rims of all these structures form in the same tectonic environment despite morphologic differences

a preliminary assessment of in place coalbed methane resources in the virginia portion of the central appalachian basin abstract in the central appalachian basin virginia leads in coalbed methane drilling and production even though it only contains a small fraction of the total coal resources and basin area in 1992 coalbed methane surpassed conventional and shale gas as virginia s largest source of natural gas by the end of 1996 there were 814 wells producing coalbed methane in virginia average daily production per well in 1996 was 114 mcf 3 2 mm 3 cumulative production of coalbed methane from 1988 through 1996 is 121 542 188 mcf 3 445 073 mm 3 factors influencing this trend include the presence of abundant coal in place including coal remaining in ground after mining sufficient overburden high gas content coal beds high gas permeability existing pipeline infrastructure and legislative clarification of uncertain coalbed gas ownership development of coalbed methane in virginia began in late 1988 production is from coal beds in the southwestern virginia coalfield a structurally distinct area along the southeastern margin of the central appalachian basin ten coal beds within the lower pennsylvanian pocahontas and lee formations and the lower pennsylvanian portion of the norton formation have been targeted for production of coalbed methane estimated coal in place for these coal beds is about 14 9 billion short tons estimated gas contents of the coal beds range from 256 ft 3 7 9 m 3 t to 698 ft 3 ton 21 5 m 3 t these data yield an estimated in place coalbed methane resource of 6 7 tcf 0 18 tm 3 for virginia the u s geological survey reported the in place coalbed methane resource for the entire central appalachian basin to be 5 tcf 0 13 tm 3 with 3 07 tcf 0 08 tm 3 technically recoverable an estimated in place coalbed methane of 6 7 tcf 0 18 tm 3 is more compatible with 3 07 tcf of technically recoverable coalbed methane for the central appalachian basin

a scalar audiomagnetotelluric survey across an outcropping dike this work presents a modeling study of the shallow electric signature of an outcropping dike of the guapiara lineament in the parana basin brazil the forward geoelectrical model was constructed on the basis of the response functions obtained with a scalar amt data set along a profile perpendicular to the strike of the dike the objective was to assess the shallow electrical signature of a typical dike in parana basin which is beyond the spatial sampling of a typical long period tensor mt survey the geoelectrical model presented in this paper identified the dike a permian sedimentary sequence and a quaternary alluvial deposit the dike intruded through a normal fault which was characterized by its vertical offset and the identification of the hanging and foot walls the dike is strongly anisotropic with a resistivity value along the strike that is two orders of magnitude smaller than along the perpendicular direction the hypothesis of an anisotropic dike is supported by an independent data set

em modeling of the central northern portion of ponta grossa arch parana basin brazil abstract broadband remote referenced magnetotelluric data were collected at 16 sites along a sw ne profile across one of the main tectonic features of parana basin the ponta grossa arch this major structure was uplifted before the voluminous flood basalt event occurred during the early cretaceous here we present a 2d model for the crustal structure of parana basin traversing the ponta grossa arch the geoelectrical strike is controlled by nw structures that cut through the crust as indicated by groom bailey decomposition several smooth 2d inversions were used as a starting point to a 2d forward modeling exercise where a priori shallow information was used as constraints that modeling strategy allowed the interpretation of two important regional features a crustal scale sub vertical shear zone 200 m in a resistive 1000 m crust and a 30 m lower crustal conductor confined within 25 40 km we have interpreted the enhanced conductivity in these two features as caused by fluids originated in mantle derived material crustal scale shear zones are considered elsewhere to be important conduits for the connection of upper and lower crustal fluids in the studied area the interpreted shear zone can be associated to main lava conduits at the time of the basalt flows the lower crustal conductor is associated to the hydrated material that intruded in the base of the crust during the mesozoic crustal underplating

hydrodynamics of coalbed methane reservoirs in the black warrior basin key to understanding reservoir performance and environmental issues abstract the black warrior basin of the southeastern united states hosts one of the world s most prolific and long lived coalbed methane plays and the wealth of experience in this basin provides insight into the relationships among basin hydrology production performance and environmental issues along the southeast margin of the basin meteoric recharge of reservoir coal beds exposed in an upturned fold limb exerts a strong control on water chemistry reservoir pressure and production performance fresh water plumes containing na hco3 waters with low tds content extend from the structurally upturned basin margin into the interior of the basin northwest of the plumes coal beds contain na cl waters with moderate to high tds content carbon isotope data from produced gas and mineral cements suggest that the fresh water plumes have been the site of significant bacterial activity and that the coalbed methane reservoirs contain a mixture of thermogenic and late stage biogenic gases water produced from the fresh water plumes may be disposed safely at the surface whereas underground injection has been used locally to dispose of highly saline water wells in areas that had normal hydrostatic reservoir pressure prior to development tend to produce large volumes of water and may take up to 4 a to reach peak gas production in contrast wells drilled in naturally underpressured areas distal to the fresh water plumes typically produce little water and achieve peak gas rates during the first year of production environmental debate has focused largely on issues associated with hydrologic communication between deep reservoir coal beds and shallow aquifers in the coalbed methane fields of the black warrior basin a broad range of geologic evidence suggests that flow is effectively confined within coal and that the thick intervals of marine shale separating coal zones limit cross formational flow

structural controls on fractured coal reservoirs in the southern appalachian black warrior foreland basin abstract coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures basin wide controls on the fractured coal reservoirs of the black warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells reservoir behavior depends on distance from the thrust front far from the thrust front normal faults are barriers to fluid migration and compartmentalize the reservoirs close to the thrust front rates are enhanced along some normal faults and a new trend is developed the two trends have the geometry of conjugate strike slip faults with the same 1 direction as the appalachian fold thrust belt and are inferred to be the result of late pure shear deformation of the foreland face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map scale production trend

temperature pressure conditions in coalbed methane reservoirs of the black warrior basin implications for carbon sequestration and enhanced coalbed methane recovery abstract sorption of gas onto coal is sensitive to pressure and temperature and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs more than 5000 wells have been drilled in the coalbed methane fields of the black warrior basin in west central alabama and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal bearing strata reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 f 27 52 c and geothermal gradient ranges from 6 0 to 19 9 f 1000 ft 10 9 36 2 c km geothermal gradient data have a strong central tendency about a mean of 9 0 f 1000 ft 16 4 c km hydrostatic pressure gradients in the coalbed methane fields range from normal 0 43 psi ft to extremely underpressured geothermal gradients within the coalbed methane fields are high enough that reservoirs never cross the gas liquid condensation line for carbon dioxide however reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft 756 m under normally pressured conditions all target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway although mature reservoirs are dewatered and thus are in the carbon dioxide gas window supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment coal can hold large quantities of carbon dioxide under supercritical conditions and supercritical isotherms indicate non langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals hence carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist

tar sandstones in the parana basin of brazil structural and magmatic controls of hydrocarbon charge abstract there are tar accumulations in lower triassic sandstones along the eastern margin of the parana basin the tar was derived from permian source rocks that matured along the basic sills of the serra geral continental flood basalt cover this paper exams the habitat of tar accumulation integrating fieldwork with morphostructural data digital elevation modelling gravity and airborne magnetic data remote sensing and radiometric dates that constrain the timing of maturation and migration the focus of this work is the jacu structural complex a large annular drainage anomaly 20 km in diameter that owes its origin to reactivation of pre existing faults interpretation of the structural framework is based primarily on morphostructural analysis and the distribution of gravity anomalies the jacu structure consists of a central low lying fault block that is surrounded by several structural highs and is attributed to the interaction of ne and nw striking fault zones the principal basement faults that encapsulate this structure were invaded by the dolerite dykes that fed the widespread flood basalt cover during the early cretaceous an 40 ar 39 ar analysis directly dates this episode of magmatism to 134 2 ma tar sandstones are restricted to the lower piramboia formation and are present around the jacu structure especially near the structural highs or close to basic dikes morphostructural interpretation suggests the occurrence of tar sandstones at intermediate positions too between the structural highs and lows the most likely explanation for these tar accumulations relates oil maturation and migration to the intrusion of lower cretaceous serra geral sills into the upper permian black shales of the irati formation and subsequent migration along faults and dyke walls into eolian sandstone reservoirs of the triassic piramboia formation not only did the basic dykes locally facilitate migration but there were also places where they were barriers to lateral migration furthermore the interdune and fluvial facies of the piramboia formation formed local seals and barriers to vertical migration

the transition from complex crater to peak ring basin on the moon new observations from the lunar orbiter laser altimeter lola instrument impact craters on planetary bodies transition with increasing size from simple to complex to peak ring basins and finally to multi ring basins important to understanding the relationship between complex craters with central peaks and multi ring basins is the analysis of protobasins exhibiting a rim crest and interior ring plus a central peak and peak ring basins exhibiting a rim crest and an interior ring new data have permitted improved portrayal and classification of these transitional features on the moon we used new 128 pixel degree gridded topographic data from the lunar orbiter laser altimeter lola instrument onboard the lunar reconnaissance orbiter combined with image mosaics to conduct a survey of craters 50 km in diameter on the moon and to update the existing catalogs of lunar peak ring basins and protobasins our updated catalog includes 17 peak ring basins rim crest diameters range from 207 km to 582 km geometric mean 343 km and 3 protobasins 137 170 km geometric mean 157 km several basins inferred to be multi ring basins in prior studies apollo moscoviense grimaldi freundlich sharonov coulomb sarton and korolev are now classified as peak ring basins due to their similarities with lunar peak ring basin morphologies and absence of definitive topographic ring structures greater than two in number we also include in our catalog 23 craters exhibiting small ring like clusters of peaks 50 205 km geometric mean 81 km one humboldt exhibits a rim crest diameter and an interior morphology that may be uniquely transitional to the process of forming peak rings a power law fit to ring diameters d ring and rim crest diameters dr of peak ring basins on the

coalbed methane resource potential and current prospects in pennsylvania abstract coalbed methane gas content analyses from exploratory coal cores and existing data indicate that gas content generally increases with increasing depth and rank the coal beds studied are from the main bituminous field of pennsylvania which currently contains 24 coalbed methane pools and the northern and southern anthracite coal fields they range from the middle pennsylvanian allegheny group to the late pennsylvanian early permian dunkard group previous us bureau of mines studies revealed gas contents from 0 4 to 13 8 cm 3 g at depths of 99 to 432 m for the bituminous coal beds of the allegheny group more recent core data from the allegheny group yielded gas contents from 2 2 to 8 9 cm 3 g at depths from 167 to 387 m in the anthracite region of eastern pennsylvania the little data that are available show that gas content is anomalously high or low gas yields from test holes in eastern pennsylvania are low with or without artificial stimulation mainly due to the lack of a good cleat system overall estimates of coalbed methane resources indicate there may be 1 7 tm 3 61 tcf of gas in place contained in the northern appalachian coal basin the amount of technically recoverable coalbed methane resources is projected by the us geological survey national oil and gas resource assessment team us geological survey national oil and gas resource assessment team 1996 1995 national assessment of united states oil and gas resources results methodology and supporting data us geological survey digital data series dds 30 cd rom denver co 80 pp and lyons lyons p c 1997 central northern appalachian coalbed methane flow grows oil and gas journal 95 27 76 79 at 0 3 tm 3 11 48 tcf this includes portions of pennsylvania ohio west virginia and a small part of maryland consequently a mapping investigation was conducted to evaluate the regional geology of the bituminous coal bearing intervals in southwestern pennsylvania and its influence on coalbed methane potential phase i of this study involved the entire pennsylvanian coal bearing interval of southwestern pennsylvania phase ii focused on a stratigraphic delineation and evaluation of allegheny group coal beds and associated sandstones several prospective coal beds and associated facies relationships with channel fill sandstones were determined possible non coal scenarios for coalbed methane include erosional contacts between coal beds and overlying channel fill sandstones and areas of stacked channel fill sandstones repetitive sequences of coal accumulation are stacked commonly with shale interburden and are also potential coalbed methane targets additional pennsylvania geological survey drilling coalbed methane sampling occurred in armstrong beaver cambria greene lawrence somerset and washington counties raw coalbed methane desorption data tables graphical displays of gas contents versus depth thickness and time and average composition and heating values from coal beds of the allegheny group to the dunkard group are available at the pennsylvania geological survey further information on cross sections isopleth maps isopach maps raw drillhole data and ownership issues can also be obtained from the same source

peak ring formation in large impact craters geophysical constraints from chicxulub a seismic reflection and three dimensional wide angle tomographic study of the buried v200 km diameter chicxulub impact crater in mexico reveals the kinematics of central structural uplift and peak ring formation during large crater collapse the seismic data show downward and inward radial collapse of the transient cavity in the outer crater and upward and outward collapse within the central structurally uplifted region peak rings are formed by the interference between these two flow regimes and involve significant radial transport of material hydrocode modeling replicates the observed collapse features impact generated melt rocks lie mostly inside the peak ring the melt appears to be clast rich and undifferentiated with a maximum thickness of 3 5 km in the center fl 2000 elsevier science b v all rights reserved

transition from complex craters to multi ringed basins on terrestrial planetary bodies scale dependent role of the expanding melt cavity and progressive interaction with the displaced zone 1 the observed differences between complex craters and multi ringed basins are described and a combined transient cavity displaced zone melt cavity model is explored to account for the observations in this nested melt cavity model the increasing influence of the percentage of the target undergoing impact melting at the sub impact point with increasing size the differential melt scaling of cintala and grieve 1998 causes fundamental changes in the nature of the transient cavity its relationship to the displaced zone and its short term collapse behavior the transition from complex craters to two ring basins involves expansion of the melting front into the displaced zone formation of a two component excavation cavity and a concomitant radial expansion outward of the zone of maximum elastic rebound the short term modification stage is then dominated by the strength differences between the fluid melt in the inner cavity and rocks of the displaced zone the highly shocked rocks at the outer margin of the expanded parabolic melting front rebound to form the expanded peak ring moving upward and laterally inward easily displacing fluid melt filling the inner depression at larger sizes differential melt scaling causes the peak ring diameter to expand relatively more rapidly than the basin rim and upon collapse the increased volume of melt ponds in the rebounded melt cavity inside the expanding peak ring as the transient melt cavity further increases proportionally in size it penetrates through the base of the displaced zone with significant consequences the resulting modification stage now incorporates into the collapse process inward and upward movement along the base of the displaced zone listric failure occurs inward into the fluid melt cavity beginning at the edge of the melt cavity and extending out along the base of the displaced zone up to the base of the rim structural uplift at 1 5 crater radii this forms an additional outer ring and a resulting megaterrace modifying the radial ejecta on the collapsed rim to form a domical facies at multi ring basin scales the significantly deeper penetration that occurs in the expanding melt cavity accounts for the maximum crustal thickness decrease that occurs inside the peak ring in the final basin early onset and higher density of peak ring basins on mercury is predicted by higher mean impact velocity and differential melt scaling