carbonate source rock with low total organic carbon content and high maturity as effective source rock in china a review abstract carbonate rocks with high maturity and low total organic carbon content are widely distributed in china whether they can be effective source rocks remains controversial but they have great significance for the evaluation of hydrocarbon generation potential and exploration prospects of carbonate rocks dataset reveals that as the depth or maturity increases total organic carbon toc content atomic h c ratio and hydrocarbon generation potential of carbonate source rocks with low total organic carbon csrltoc all decrease because of hydrocarbon expulsion moreover some pyrolysis experiments also indicate that the csrltoc are able to generate and expel a quantity of hydrocarbons the above studies indicate that csrltoc can be effective source rocks for oil gas pools the unique features of carbonate rocks and csrltoc demonstrate that they are easier to expel hydrocarbons and contribute to oil gas reservoirs than shale and thus the lower limit of toc lltoc of effective carbonate source rocks could be smaller than shale 0 5 the lltocs of effective carbonate source rocks with type i ii1 kerogen mainly sapropelic group at the levels of immaturity and low maturity maturity high maturity and over maturity are toc 0 5 0 5 0 3 0 3 0 2 and 0 2 0 1 respectively if the carbonate source rocks are at the high over mature stage we could take 0 2 as the lltoc the present organic poor source rocks with high maturity are possibly moderate or good source rocks at the low mature level in the geological periods especially carbonate source rocks if type i ii1 kerogen some typical oil and gas fields in china derive partly or mostly from the csrltoc proving that csrltoc could be effective source rock in china

geochemical relationships of petroleum in mesozoic reservoirs to carbonate source rocks of jurassic smackover formation southwestern alabama algal carbonate mudstones of the jurassic smackover formation are the main source rocks for oil and condensate in mesozoic reservoir rocks in southwestern alabama this interpretation is based on geochemical analyses of oils condensates and organic matter in selected samples of shale norphlet formation haynesville formation trinity group tuscaloosa group and carbonate smackover formation rocks potential and probable oil source rocks are present in the tuscaloosa group and smackover formation respectively extractable organic matter from smackover carbonates has molecular and isotopic similarities to jurassic oil although the jurassic oils and condensates in southwestern alabama have genetic similarities they show significant compositional variations due to differences in thermal maturity and organic facies lithofacies organic facies reflect different depositional conditions for source rocks in the various basins the mississippi interior salt basin was characterized by more continuous marine to hypersaline conditions whereas the manila and conecuh embayments periodically had lower salinity and greater input of clastic debris and terrestrial organic matter petroleum and organic matter in jurassic rocks of southwestern alabama show a range of thermal transformations the gas content of hydrocarbons in reservoirs increases with increasing depth and temperature in some reservoirs where the temperature is above 266 f 130 c gas condensate is enriched in isotopically heavy sulfur apparently derived from thermochemical reduction of jurassic evaporite sulfate this process also results in increased h2s and co2 in the gas and depletion of saturated hydrocarbons in the condensate liquids thermochemical sulfate reduction probably depends on the mineralogic composition of the reservoir rock as well as temperature because some deep 18 000 ft or 5 5 km and hot 320 f or 160 c smackover and norphlet reservoirs contain low sulfur petroleum

mesozoic upper jurassic lower cretaceous deep gas reservoir play central and eastern gulf coastal plain the mesozoic upper jurassic lower cretaceous deeply buried gas reservoir play in the central and eastern gulf coastal plain of the united states has high potential for significant gas resources sequence stratigraphic study petroleum system analysis and resource assessment were used to characterize this developing play and to identify areas in the north louisiana and mississippi interior salt basins with potential for deeply buried gas reservoirs these reservoir facies accumulated in upper jurassic to lower cretaceous norphlet haynesville cotton valley and hosston continental coastal and marine siliciclastic environments and smackover and sligo nearshore marine shelf ramp and reef carbonate environments these mesozoic strata are associated with transgressive and regressive systems tracts in the north louisiana salt basin the estimate of secondary nonassociated thermogenic gas generated from thermal cracking of oil to gas in the upper jurassic smackover source rocks from depths below 3658 m 12 000 ft is 4800 tcf of gas as determined using software applications assuming a gas expulsion migration and trapping efficiency of 2 3 96 144 tcf of gas is potentially available in this basin with some 29 tcf of gas being produced from the north louisiana salt basin 67 115 tcf of in place gas remains assuming a gas recovery factor of 65 44 75 tcf of gas is potentially recoverable the expelled thermogenic gas migrated laterally and vertically from the southern part of this basin to the updip northern part into shallower reservoirs to depths of up to 610 m 2000 ft

structural control of jurassic sedimentation in alabama and florida the extent and thickness of jurassic strata in alabama and florida were mapped as part of a u s geological survey regional geohydrologic study rocks equivalent to the werner louann norphlet smackover haynesville and cotton valley sequences of mississippi and arkansas have been recognized and except for the werner equivalent are herein extended into panhandle florida the predominantly fluvial jurassic sequence in alabama and florida was interrupted at least twice by barred basin conditions that resulted in the deposition of extensive evaporite deposits and at least once during deposition of the smackover formation by a major marine transgression the updip limits and isopach map trends of the jurassic units mapped appear to have been controlled by a major nort west trending right lateral wrench fault the dominant master shear in a regional wrench fault system active throughout jurassic time

robust rock properties through pp ps processing and interpretation marcellus shale the estimation of reservoir properties from seismic amplitude is generally an underdetermined problem which can result in ambiguous estimation of the sought for properties although seismic reflectivity is dependent upon formation p and s wave velocities and density it is common practice to estimate only two attributes from prestack p wave data because of data limitations at far offsets and instabilities of inversion on the other hand the number of petrophysical properties that determine reservoir storability and production are four in the simplest of cases porosity lithology pore fluids type and amount and permeability ambiguity and risk reduction require the inclusion of additional robust information into the estimation of reservoir properties this is particularly true in formations where reservoir storability and production depend on additional petrophysical properties as would be the case of unconventional plays where brittleness and vertical fracture density and orientation are fact

north slope alaska source rock distribution richness thermal maturity and petroleum charge four key marine petroleum source rock units were identified characterized and mapped in the subsurface to better understand the origin and distribution of petroleum on the north slope of alaska these marine source rocks from oldest to youngest include four intervals 1 middle upper triassic shublik formation 2 basal condensed section in the jurassic lower cretaceous kingak shale 3 cretaceous pebble shale unit and 4 cretaceous hue shale well logs for more than 60 wells and total organic carbon toc and rock eval pyrolysis analyses for 1183 samples in 125 well penetrations of the source rocks were used to map the present day thickness of each source rock and the quantity toc quality hydrogen index and thermal maturity tmax of the organic matter based on assumptions related to carbon mass balance and regional distributions of toc the present day source rock quantity and quality maps were used to determine the extent of fractional conversion of the kerogen to petroleum and to map the original toc toco and the original hydrogen index hio prior to thermal maturation the quantity and quality of oil prone organic matter in shublik formation source rock generally exceeded that of the other units prior to thermal maturation commonly toco 4 wt and hio 600 mg hydrocarbon g toc although all are likely sources for at least some petroleum on the north slope we used rock eval and hydrous pyrolysis methods to calculate expulsion factors and petroleum charge for each of the four source rocks in the study area without attempting to identify the correct methods we conclude that calculations based on rock eval pyrolysis overestimate expulsion factors and petroleum charge because low pressure and rapid removal of thermally cracked products by the carrier gas retards cross linking and pyrobitumen formation that is otherwise favored by natural burial maturation expulsion factors and petroleum charge based on hydrous pyrolysis may also be high compared to nature for a similar reason

how tides and river flows determine estuarine bathymetries abstract for strongly tidal funnel shaped estuaries we examine how tides and river flows determine size and shape we also consider how long it takes for bathymetric adjustment both to determine whether present day bathymetry reflects prevailing forcing and how rapidly changes might occur under future forcing scenarios starting with the assumption of a synchronous estuary i e where the sea surface slope resulting from the axial gradient in phase of tidal elevation significantly exceeds the gradient in tidal amplitude an expression is derived for the slope of the sea bed thence by integration we derive expressions for the axial depth profile and estuarine length l as a function of and d the prescribed depth at the mouth calculated values of l are broadly consistent with observations the synchronous estuary approach enables a number of dynamical parameters to be directly calculated and conveniently illustrated as functions of and d namely current amplitude u ratio of friction to inertia terms estuarine length stratification saline intrusion length flushing time mean suspended sediment concentration and sediment in fill times four separate derivations for the length of saline intrusion li all indicate a dependency on d 2 f u u o uo is the residual river flow velocity and f is the bed friction coefficient likely bathymetries for mixed estuaries can be delineated by mapping against and d the conditions li l however the length of saline intrusion in a funnel shaped estuary is also sensitive to axial location observations suggest that this location corresponds to a minimum in landward intrusion of salt by combining the derived expressions for l and li with this latter criterion an expression is derived relating di the depth at the centre of the intrusion to the corresponding value of uo this expression indicates uo is always close to 1 cm s 1 as commonly observed converting from uo to river flow q provides a morphological expression linking estuarine depth to q with a small dependence on side slope gradients these dynamical solutions are coupled with further generalised theory related to depth and time mean suspended sediment concentrations as functions of and d then by assuming the transport of fine marine sediments approximates that of a dissolved tracer the rate of estuarine supply can be determined by combining these derived mean concentrations with estimates of flushing time ft based on li by further assuming that all such sediments are deposited minimum times for these deposition rates to in fill estuaries are determined these times range from a decade for the shortest shallowest estuaries to upwards of millennia in longer deeper estuaries with smaller tidal ranges

joint sets that enhance production from middle and upper devonian gas shales of the appalachian basin the marine middle and upper devonian section of the appalachian basin includes several black shale units that carry two regional joint sets j1 and j2 sets as observed in outcrop core and borehole images these joints formed close to or at peak burial depth as natural hydraulic fractures induced by abnormal fluid pressures generated during thermal maturation of organic matter when present together earlier j1 joints are crosscut by later j2 joints in outcrops of black shale on the foreland northwest side of the appalachian basin the east northeast trending j1 set is more closely spaced than the northwest striking j2 set however j2 joints are far more pervasive throughout the exposed devonian marine clastic section on both sides of the basin by geological coincidence the j1 set is nearly parallel the maximum compressive normal stress of the contemporary tectonic stress field shmax because the contemporary tectonic stress field favors the propagation of hydraulic fracture completions to the east northeast fracture stimulation from vertical wells intersects and drains j2 joints horizontal drilling and subsequent stimulation benefit from both joint sets by drilling in the north northwest south southeast directions horizontal wells cross and drain j1 joints whenever present then staged hydraulic fracture stimulations if necessary run east northeast i e parallel to the j1 set under the influence of the contemporary tectonic stress field thereby crosscutting and draining j2 joints

new typologies for estuarine morphology new theories to explain how tides and river flow determine estuarine bathymetries have been developed the range of validity of these theories has been subsequently assessed against a recently available observational data set success in reproducing the evolution of estuarine bathymetries that has occurred over the last 10 000 years provides the basis for the translation here of these theories into new typologies these then provide reference frameworks to enhance our perspective on existing morphologies and identify anomalous estuaries further refinement of these new theories requires analyses of causal factors responsible for such anomalies drawing on classical morphological experience these frameworks can also be used for calculating likely future bathymetric adjustments for prescribed changes in mean sea level tidal amplitudes river flow and sediment supply

lower tertiary and upper cretaceous source rocks in louisiana and mississippi implications to gulf of mexico crude oil the lower tertiary sparta formation wilcox group and the midway group in southern louisiana include organic rich source facies that generate crude oil at relatively high thermal maturities the wilcox group is an important source of wilcox crude oil and regional kerogen variations explain two crude oil subfamilies wilcox crude oils in downdip areas of southern louisiana migrated short distances but long range lateral migration about 150 km best explains wilcox crude oils far updip from mature source rocks crude oils in oligocene and younger reservoirs in southern louisiana migrated vertically from deep lower tertiary source rocks some crude oils in upper cretaceous tuscaloosa reservoirs were emplaced by long range lateral migration from tuscaloosa source rocks g ven little evidence of upper tertiary source rocks and the overmaturity problems of mesozoic source rocks most crude oils in upper tertiary and pleistocene reservoirs of the gulf continental shelf are best explained by vertical migration from deep lower tertiary source rocks even so it is simplistic to assume an exclusive lower tertiary origin many tertiary and pleistocene crude oils of this study probably include an overprint of high maturity hydrocarbons from mesozoic sources

multiple stage migration and accumulation of permian lacustrine mixed oils in the central junggar basin nw china abstract the permian lacustrine petroleum system in the central junggar basin northwest china has recently obtained exploration success these accumulations are characterized by mixed oils and multiple stage migration and accumulation this process however has not been well constrained limiting the understanding of the general laws of hydrocarbon migration and accumulation and making it difficult to define exploration strategies here we reconstruct this process mainly based on oil bearing fluid inclusion analyses including petrography homogenization temperature and sequential extraction inclusion petrography shows that petroleum inclusions dominantly display yellow fluorescence while intergranular free oils mostly display strong blue green fluorescence this implies that the reservoirs seem to have experienced at least two stages of hydrocarbon charge from different sources and or maturities the sources maturities are determined through reservoir sequential extraction analyses the free oils are mixed and sourced from the lower permian fengcheng formation p1f and the middle permian lower wuerhe formation p2w while the inclusion oils are also mixed and derived mainly from the p1f source both oils are characterized by moderate maturity homogenization temperature measurements of oil bearing fluid inclusions combined with reconstruction of reservoir burial and thermal history not only further verify multiple hydrocarbon charging events but also characterize the timing which indicates a three stage petroleum charging model during the first stage of the late triassic carboniferous reservoirs were charged by p1f sourced oils which were dysmigrated or remigrated to jurassic reservoirs during the second stage i e the early cretaceous in contrast the third stage from the late cretaceous represents another hydrocarbon charge event that is the primary oil accumulation sourced from the p2w rocks according to this model both primary and secondary oil accumulations contribute to the current region s exploration success and provide future exploration targets

estuaries are not so unique 1 the applicability of recent theories relating tides and river flow to estuarine bathymetry has been assessed against observations from uk estuaries these theories combined with observations show that variations between estuaries are limited by how tides and river flow control sediments and bathymetry typical ages were determined from differences between theoretical and observed depths for rias 11000 years coastal plain 15000 years and bar built 100 years estuaries the theories can explain the estuarine bathymetry without needing to account for the sediments suggesting that it is the bathymetry which determines the sediment regime within the estuary

morphological change in the pearl river delta china morphological changes in the pearl river delta prd have been investigated using bathymetric charts underwater digital elevation models remote sensing data and geographic information systems water depths were extracted from digitized charts to explore the accretion erosion characteristics of three estuarine environments and to provide quantitative estimates of changes in sediment volumes multi temporal satellite images have been used in combination with topographical data to analyze the coastline changes prd has gained an abundant amount of sediment of almost 9 45 105 km3 above the 10 m isobath in the period roughly between 1970 and 2010 the average sedimentation rate was 3 15 104 km3 yr between 1976 and 2006 the coastline extended seaward by 579 2 m on average with a mean net extension rate of 19 3 m yr the results suggest that the prd experienced a major phase of accretion with net erosion only in some local zones coastline extension associated with major morphological changes has accelerated in recent decades changes in boundary conditions such as sea level rise seem to have relatively minor impacts on the dramatic changes in the morphology of the estuaries the seaward extension of the coastlines shows an increasing trend whereas the sediment supply from the delta displays a decreasing trend a detailed comparative analysis demonstrates that land reclamation in the prd is the most significant factor that progressively alters the delta morphology overwhelming the effects of subsidence and sediment supply

sequence stratigraphic analysis of jurassic and cretaceous strata and petroleum exploration in the central and eastern gulf coastal plain united states the formulation of an integrated sequence stratigraphic and biostratigraphic framework is fundamental in the design of an effective strategy for petroleum exploration in a sedimentary basin for the interior salt basins of the gulf coastal plain of the united states that are filled primarily with mesozoic postrift nonmarine to marine siliciclastic and carbonate deposits a sequence stratigraphic approach using transgressive regressive t r sequences and integrated with biostratigraphic information has utility as a method for establishing such a framework the sequence stratigraphy established for upper jurassic and cretaceous strata is used to categorize petroleum reservoirs in the central and eastern gulf coastal plain transgressive aggrading eolian fluvial and coastal sandstone facies of the t r sequences include highly productive hydrocarbon reservoirs in the eastern gulf coastal plain productive reservoirs in the central and eastern gulf coastal plain include regressive infilling fluvial to nearshore marine sandstone facies and nearshore marine shelf ramp and reef carbonate facies transgressive backstepping nearshore marine facies include highly productive reservoirs in the central gulf coastal plain these transgressive and regressive facies are recognized by their wireline log patterns and seismic reflection configurations knowledge of the diagnostic wireline log signatures and seismic reflection characteristics assists in the detection of exploration targets

haynesville and bossier mudrocks a facies and sequence stratigraphic investigation east texas and louisiana usa abstract upper jurassic haynesville and bossier shale gas plays of the northwestern gulf of mexico gom basin produce from organic rich marine transgressive to highstand mudrocks within mixed carbonate clastic depositional systems modern wireline log suites from 200 deep wells were used for detailed correlations and 10 cores throughout the upper kimmeridgian to lower tithonian basin were incorporated into detailed facies stratigraphic and lithologic analyses the haynesville shale lies within a 2nd order transgressive systems tract tst that encompasses back stepping ramp carbonates proximal and marine shales distal below a maximum flooding surface mfs this shale onlaps retrogradational carbonates and basement highs and is capped by the 2nd order mfs bossier shales and local sandstones prograde basinward above the haynesville shale and downlap the 2nd order mfs they grade upward and updip into the thick highstand systems tract hst fluvio deltaic sandstones of the cotton valley group distally organic rich facies developed in restricted bossier environments creating another productive gas shale opportunity several preexisting basement highs in the south and carbonate platforms in the northwest and west restrict and partition the basin thus influencing deposition of highly organic versus nonorganic and siliciclastic dominated versus carbonate dominated lithologies haynesville and bossier shales each compose three upward coarsening cycles that probably represent 3rd order sequences within the larger 2nd order tst and early hst respectively most of the three bossier 3rd order cycles are dominated by varying amounts of siliciclastics deposition of the haynesville mudrocks occurred below storm wave base under mostly dysoxic conditionsm allowing settlement of benthic bivalve communities and bioturbating organisms and oscillating periodically to more anoxic conditions on the seafloor however most of the sparse faunae found in these mudrocks are of planktonic origin bossier mudrocks exhibited more oxygenated and clastic rich lithologies related to progradation of the clastic shoreline and sea level highstand knowledge of lithologic stratigraphic geochemical and faunal variations across mudrock basins needs to be detailed so that shale gas basins might be successfully explored

bathymetric evolution of the mersey estuary uk 1906 1997 causes and effects this paper examines how a continuous series of measurements and model studies have developed our understanding of the evolving interactions between tidal dynamics sediment regime and bathymetry of the mersey estuary among the most intensively monitored worldwide this includes familiar assessments of the capabilities of fine resolution 3 d models but is here extended to examine historical changes in tides sediments and estuarine bathymetries a century of bathymetric surveys indicates a net loss of estuarine volume of about 0 1 or 1 million cubic metres per year in contrast sea level rise of 1 2 mm a 1 represents only a 0 02 annual increase this relative stability persists in a highly dynamic regime with suspended sediment concentrations exceeding 2000 mg l 1 and spring tide fluxes of order 200 000 t detailed analyses of the bathymetric sequences indicate most significant changes occur in the upper estuary and in inter tidal zones a long period up to 63 years of tidal elevation records in the lower estuary shows almost no changes to the predominant m2 and s2 constituents the 3 d numerical model accurately reproduces both these elevation constituents and corresponding cross sectional distributions of currents simulation accuracies reduce upstream due to cumulative errors associated with relatively unstable bathymetries and increasing sensitivities to the bed stress coefficients impacts from increases in river flows of up to two or three times the long term mean value can only be detected in the upper estuary a detailed examination of sediment fluxes utilised a numerical simulation of conditions over a cross section in the narrows the 10 km by 1 5 km prismatic entrance channel the limited mobility of coarse sediments was contrasted with the near continuously suspended nature of the finest clay a sensible match between the net sedimentation rates indicated by the model and the net observed deposition rate was found to occur for silty sand corresponding directly with evidence from dredging records and from direct sampling while the model indicated sedimentation rates might increase by up to a factor of ten for much finer particles such occurrences are likely to be restricted by the limited availability of such material in the adjacent coastal zone the controlling mechanism for this import of fine sediments is via tidal pumping the nature of which depends critically on the phase lead of tidal currents relative to elevation however since this phase lead is determined by the large scale tidal energy balance of the estuary the conclusion is that stability of the overall tidal dynamics the associated sediment regime and bathymetry are likely to co exist and evolve slowly as indicated by the observed annual decrease in net volume suggestions are included for monitoring strategies in other estuaries to provide insight into such dynamics sediment bathymetry inter relationships

dynamical controls on estuarine bathymetry assessment against uk database abstract new theories for estuarine bathymetry provide formulations for 1 depth at the mouth d versus river flow q 2 tidal intrusion length l versus d and z tidal amplitude and 3 a zone of morphological existence delineated on a framework of z versus d here these theories are assessed against a database for 80 uk estuaries overall there is good agreement between theory and observations for the sizes and shapes of estuaries classified as either coastal plain or bar built likewise most estuaries are shown to lie within the theoretical zone of bathymetric existence these encouraging agreements enable the theories to be used to 1 enhance our understanding of existing morphologies 2 identify anomalous estuaries and 3 make future predictions regarding likely impacts from global climate change and related management scenarios subsequent examination of regional historical patterns of morphological evolution introducing detailed local knowledge should help to explain these anomalies and refine the new theories by 2100 we anticipate changes in uk estuaries due to precautionary projected 25 changes in river flow of order 0 5 5 km in lengths and order 50 250 m in breadths corresponding changes due to a projected sea level rise of 50 cm are increases in both lengths of order 1 2 5 km and breadths of order 70 100 m in both cases the bigger changes will occur in larger estuaries

impacts of topography change on saltwater intrusion over the past decade in the changjiang estuary abstract saltwater intrusion in estuaries is mainly controlled by tides and river discharge as well as by topography and other factors the changjiang estuary has been seen a significant change in its topography from the data obtained in 2007 and 2017 in this study a well validated 3d numerical model was used to simulate and analyze the residual water and salt transport water diversion ratio wdr in bifurcated channels and water resources in the changjiang estuary in 2007 and 2017 the comparisons of the model results showed that due to the north branch becoming much shallower and narrower over the period from 2007 to 2017 the overall salinity in the north branch decreased and the intensity of saltwater spillover sso from the north branch into the south branch weakened in the north channel the simulated residual or net transection water flux ntwf and wdr decreased during spring tides resulting in increased saltwater intrusion during neap tides the saltwater intrusion was weakened despite the decreased ntwf and wdr because the water depth at the river mouth became shallower the changes of topography during that period also resulted in changes of dwr ntwf salt transport across the tidal flats and dykes in the north passage south passage and the south channel as well as overall dynamic mechanism the results indicated that the salinity at the water intakes of the three reservoirs in the estuary slightly decreased indicating that the time that reservoirs can take water from the estuary become longer in dry seasons in the scenario of complete silt up of the north branch the saltwater intrusion was weakened in the south branch because of the disappearance of the sso which was favorable for the utilization of freshwater resources but enhanced in the north channel north and south passages the overall influence from the topographic change over the period is that the saltwater intrusion is weakened in the north branch and enhanced during spring tides and weakened during neap tides in the north channel north and south passages sediment accretion in the north branch is favorable for utilization of freshwater resources

geologic analysis of the upper jurassic haynesville shale in east texas and west louisiana the upper jurassic haynesville shale is currently regarded as one of the most prolific emerging shale gas plays in the continental united states it has estimated play resources of several hundred trillion cubic feet and per well reserves estimated as much as 7 5 bcf the reservoir spans more than 16 counties along the boundary of eastern texas and western louisiana although this basin has a long history of exploration and analysis of its mesozoic section a comprehensive subsurface study characterizing the haynesville shale has not been conducted this article is the first to address the structural setting stratigraphy depositional environment and facies fracturing and production challenges of the haynesville shale gas play basement structures and salt movement influenced carbonate and siliciclastic sedimentation associated with the opening of the gulf of mexico the haynesville shale is an organic and carbonate rich mudrock that was deposited in a deep partly euxinic and anoxic basin during the kimmeridgian to the early tithonian related to a second order transgression that deposited organic rich black shales worldwide the haynesville basin was surrounded by carbonate shelves of the smackover and haynesville lime louark sequence in the north and west several rivers supplied sand and mud from the northwest north and northeast into the basin haynesville mudrocks contain a spectrum of facies ranging from bioturbated calcareous mudstone laminated calcareous mudstone and silty peloidal siliceous mudstone to unlaminated siliceous organic rich mudstone framboidal to colloidal pyrite is variably present in the form of concretions laminae and individual framboids and replaces calcite cement and mollusk shells haynesville reservoirs are characterized by overpressuring porosity averaging 8 to 12 sw of 20 to 30 nanodarcy permeabilities reservoir thickness of 200 to 300 ft 70 to100 m and initial production of as much as 30 mmcf day reservoir depth ranges from 9000 to 14 000 ft 3000 to 4700 m and lateral drilling distances are 3000 to 5000 ft 1000 to 1700 m typical haynesville wells exhibit a steeper decline curve 80 in the first year than other shale gas plays which is attributed to a very high overpressure

framework of hydrocarbon generation and destruction in eastern smackover trend laminated lime mudstones of the lower member of the jurassic smackover formation are significant source rocks for crude oil across mississippi alabama and florida the source facies was deposited in an anoxic and perhaps hypersaline environment that preserved algal derived kerogen the distribution of kerogen along laminations of depositional origin and along stylolites of diagenetic origin resulted in efficient expulsion of crude oil with increasing thermal maturity crude oil initially emplaced in reservoirs was cracked to yield gas condensate and then methane rich in nonhydrocarbon gases such as hydrogen sulfide carbon dioxide and nitrogen early destruction of methane was driven by thermochemical sulfate reduction the thermal maturity framework of the smackover rend explains the distribution of hydrocarbon discoveries and suggests areas previously overlooked by exploration

applications for vector coordinate systems of 3 d converted wave data recently 3 d four component marine ocean bottom cable obc data has come into broad use for a variety of applications however understanding how these new components and their associated acquisition and processing coordinate systems are related to the vector wavefield has become a challenging task for the exploration industry the compressional wavefield p wave is obtained from the pressure response of the hydrophone plus the particle motion response from the vertical geophone a converted p wave to shear wavefield ps wave is obtained from two horizontal geophone components oriented in an acquisition coordinate system of in line and cross line particle motion

hydrocarbon transfer pathways from smackover source rocks to younger reservoir traps in the monroe gas field ne louisiana abstract the monroe gas field originally contained more than 7 trillion cubic feet of gas much of the gas reserve has been produced through wells penetrating the upper cretaceous monroe gas rock formation reservoir secondary reservoirs in the field area have included those from the eocene wilcox group upper cretaceous arkadelphia nacatoch and ozan formations lower cretaceous hosston formation and jurassic schuler and smackover formations together all secondary reservoirs have contributed a minor amount of gas to the field the source of most of the field s gas appears to have been in the lower smackover source rock maturity was enhanced by igneous activity wrench faults and unconformity surfaces served as migration conduits through the pre paleocene section hydrocarbon transfer pathways appear to be more vertically direct and exhibit a less complex pattern in the jurassic and lower cretaceous than in the upper cretaceous section

the framework of hydrocarbon generation and migration gulf of mexico continental slope abstract the occurrence of large volumes of crude oil and thermogenic gas in plio pleistocene reservoirs and holocene seeps of the gulf of mexico slope argues that the process of hydrocarbon generation and migration continues at the present time calculated thermal maturity models based on deep seismic stratigraphy indicate that cretaceous and possibly early tertiary sediments are presently within the thermal maturity range for generation and expulsion of crude oil the cretaceous and early tertiary sediments are suggested as possible source rocks because younger sediments are thermally immature for crude oil generation and older sediments are thermally overmature for crude oil preservation the calculated thermal maturity profile for the slope indicates that some generation of crude oil could occur as shallow as 6 km and that liquid hydrocarbons could be preserved as deep as 9 km thermogenic gas is stable at even greater depths migration with a strong vertical component must be invoked to explain thermogenic hydrocarbons in shallow reservoirs and seeps of the slope the great depth at which liquid hydrocarbons and dry gas can be preserved in reservoirs of the gulf of mexico salt basin indicates that huge volumes of prospective section remain essentially unexplored

distribution of hydrocarbon source potential in the jurassic smackover formation abstract there are regionally consistent differences in source potential between the upper and lower members of the smackover formation measurements of total organic carbon and visual kerogen assessments indicate that the lower smackover has source potential for crude oil from texas to florida source potential is largely restricted to the laminated lime mudstone facies of the lower smackover where deposition occurred in a subtidal environment that was anoxic and probably hypersaline algal derived amorphous kerogen is concentrated in laminations of depositional origin carbonate diagenesis during burial enhanced source potential by further concentrating kerogen along stylolites we suggest that the efficiency of hydrocarbon expulsion has been enhanced by depositional and diagenetic factors that concentrate source rock kerogen along conduits for fluid movement the upper smackover serves mainly as a reservoir rock and other jurassic formations lack source potential

burial diagenesis and porosity evolution upper jurassic smackover arkansas and louisiana the jurassic upper smackover ooid lime grainstone of the central gulf coast has been a major hydrocarbon exploration target for nearly half a century study of the geologic and sedimentologic framework petrography two phase fluid inclusions and trace element and stable isotope chemistry indicates the following diagenetic history the upper smackover is a blanket ooid grainstone ranging in thickness from 300 to 400 ft 91 to 122 m and covering at least 4 000 sq mi 10 400 sq km in the northern part of the arkansas shelf a regional meteoric water system was established in the grainstone shortly after deposition and prior to significant burial this meteoric water system gave way to conditions which were increasingly more marine toward the south near the louisiana arkansas state line the fresh to marine hydrologic gradient is responsible for the strong precompaction regional diagenetic overprint that eventually controlled available diagenetic pathways for the unit during burial three diagenetic zones are present 1 a northern zone dominated by oomoldic porosity and preburial spar cementation 2 a sou hern zone characterized by compaction effects late subsurface cement primary porosity preservation and late secondary subsurface porosity generation and 3 a transitional zone having characteristics common to both the northern and southern zones during the shallow burial phase compaction became increasingly more important to the south in zones dominated by marine connate fluid whereas rock integrity and a secondary oomoldic porosity system had already been established in the northern zone as burial increased brine originating in the underlying louann salt reached the shelf grainstone and began to displace the original connate fluid the brine triggered the inversion to calcite of remaining grains and cement composed of unstable mineralogy when the louann brine had displaced the original connate fluid caso4 replacement as gypsum and anhydrite was common across all three diagenetic zones also precompaction fine cement associated with oomoldic porosity was recrystallized and reequilibrated with the concentrate brine localized replacement dolomitization may well have developed throughout the burial history of the sequence but was most commonly postcompactional postcompaction poikilitic calcite cement and baroque dolomite were precipitated from the louann brine under conditions of elevated temperature and pressure as subsidence continued organic material from the basinward equivalents of the upper smackover lime grainstone arrived on the shelf and catalyzed so4 reduction resulting in pyrite and galena replacement in the southern and transitional zones as hydrocarbon maturation continued in the fine grained equivalents of the upper smackover h2s and co2 by products of these processes began to increase in the brine of the southern and transitional zones ultimately causing regional dissolution of existing carbonate and significantly enhancing preserved porosity porosity in the northern zone was established early and preserved through moderate burial although porosity is well developed permeability has been largely destroyed by recrystallization dolomitization is a prerequisite for economic reservoir development in the northern zone porosity in the southern zone is solution enhanced preserved primary intergranular porosity compaction is the most important porosity destruction process compaction in the absence of an early diagenetic overprint is affected primarily by grain type and secondarily by size and sorting pellets and oncolites compact easily yet destroy porosity during burial ooids and rhodolites resist compaction during burial therefore are related to porosity preservation grain type distribution as well as size and sorting are controlled by depositional environment processes with the most favorable areas for porosity development concentrations of ooids and rhodolites associated with early salt related structural movement porosity distribution in the southern zone therefore can be outli ed with the aid of geophysical end page 597 techniques porosity in the transitional zone is early secondary or preserved primary intergranular or a combination porosity in this zone therefore is highly unpredictable and a strong potential exists for diagenetic traps unrelated to structure or original depositional environment documentation of significant deep subsurface secondary porosity possibly associated with hydrocarbon maturation opens the potential for hydrocarbon exploration in deeply buried carbonate dominated basins this would include carbonate rocks heretofore thought to be well below the depth of carbonate porosity maintenance because of lithostatic load

organic petrology of the aptian age section in the downdip mississippi interior salt basin mississippi usa observations and preliminary implications for thermal maturation history abstract this study identifies a thermal maturity anomaly within the downdip mississippi interior salt basin misb of southern mississippi usa through examination of bitumen reflectance data from aptian age strata sligo formation pine island shale james limestone and rodessa formation u s geological survey usgs reconnaissance investigations conducted in 2011 2012 examined aptian age thermal maturity trends across the onshore northern gulf of mexico region and indicated that the section in the downdip misb is approaching the wet gas condensate window ro 1 2 a focused study in 2012 2013 used 6 whole core one sidewall core and 49 high graded cutting samples depth range of 13 000 16 500 ft 3962 4 5029 2 m below surface collected from 15 downdip misb wells for mineralogy fluid inclusion organic geochemistry and organic petrographic analysis based on native solid bitumen reflectance ro generally 0 8 interpreted to be post oil indigenous bitumens matured in situ ro values increase regionally across the misb from the southeast to the northwest thermal maturity in the eastern half of the basin ro range 1 0 to 1 25 appears to be related to present day burial depth and shows a gradual increase with respect to depth to the west thermal maturity continues to increase even as the aptian section shallows structurally on the adams county high ro range 1 4 to 1 8 after evaluating the possible thermal agents responsible for increasing maturity at shallower depths i e igneous activity proximity to salt variations in regional heat flux and uplift we tentatively propose that either greater paleoheat flow or deeper burial coupled with uplift in the western part of the misb could be responsible for the thermal maturity anomaly further research and additional data are needed to determine the cause s of the thermal anomaly

early evolution of salt structures in the north louisiana salt basin abstract several salt diapirs and pillows in southern and central north louisiana have been studied utilizing approximately 355 miles 570 km of seismic reflection data and information from 57 deep well holes the use of seismic profiles coupled with deep well hole data is the most advantageous method to document regional salt tectonism through time three stages pillow diapir and post diapir stages are required to explain salt stock growth through time in the north louisiana salt basin the pillow stage and its associated primary peripheral sinks exhibit 11 34 thinning over pillow crests and 12 50 overthickening in the primary peripheral sinks in the basin thinning values as great as 87 and overthickening values as high as 400 are inferred for pre diapiric juvenile salt pillows the diapir stage and its associated secondary peripheral sinks exhibit 50 250 overthickening this stage is characterized by piercement diapirisin and the withdrawal of large volumes of salt from the flanks of the pillow the post diapir stage and its associated peripheral sinks exhibit less than 45 overthickening moreover in some instances dome growth is in a steady state with sedimentation growth stages are generally confined to the following stratigraphic units smackover to knowles pillow stage calvin diapir stage and winn and younger sediments post diapir stage the above considerations lead to the following conclusions on diapirism in the north louisiana salt basin 1 onset of the diapiric event was early late jurassic in the southern and central portion of the basin and later early cretaceous in the northern portion 2 the initial diapiric event is much more rapid and intense in the southern and central diapirs when compared with the later diapiric event in the northern diapirs 3 regional depocenter shifting relative sea level local erosion with salt extrusion and rapid depositional loading of sediments are the major controls on diapirism in the basin

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

estimation of thermal maturity in the bakken source rock from a combination of well logs north dakota usa abstract numerous attempts have been conducted to construct a reliable model to relate petrophysical and geomechanical characteristics of shale to geochemical properties in this study continuous logs were built to predict the thermal maturity of the bakken formation from a set of petrophysical logs first dynamic modulus ed was created from shear and compressional sonic and density logs and then converted to ei nanoindentation based young s modulus using the existing experimental relationship between ed and ei next continuous toc logs were generated for the bakken shales based on an empirical relationship between well log derived ei and toc contents that were measured in the lab there was found an acceptable difference between estimated log based toc and measured values in three separate wells solid bitumen reflectance as a reliable indicator of thermal maturity was measured on all samples from the same wells in the scarcity absence of vitrinite maceral the relationships between gr nphi rhoz wireline logs versus solid bitumen reflectance bro as the maturity index was then investigated in twelve wells based on the strength or weight of the relationship between each log and bro a new parameter was defined to represent thermal maturity from well logs a good agreement between parameter and bro values was observed which provided an empirical equation to make the estimation of bro values for the whole length of the shale members possible ultimately the continuity of bro values would enable us to establish a relationship between bro and measured tmax values to generate continuous tmax logs for the bakken shale members using these newly developed well logs it would become possible to make a 3d property models for bro and tmax the thermal maturity property cube for an accurate petroleum system evaluation based on gr nphi rhoz logs

atomic h c ratio of kerogen as an estimate of thermal maturity and organic matter conversion in recent years the atomic h c hydrogen to carbon ratio of kerogen as a way to assess the quality of organic matter in source rocks has been overlooked in favor of the more easily determined rock eval hydrogen index rock eval pyrolysis provides fast inexpensive quantitative mg hc g rock data without requiring kerogen isolation from the rock because of the general scatter in the data many source rock interpreters consider rock eval pyrolysis to be a screening analysis in this paper i describe the benefits of using h c ratios in source rock evaluations and present new correlations between atomic h c ratios and thermal maturity organic matter conversion and expulsion volumetrics atomic h c ratios of pyrolyzed kerogens have been correlated to the extent of thermal conversion of organic matter for both type i and type ii kerogens the excellent agreement between stoichiometric calculated hydrogen and carbon loss to observed losses from hydrous pyrolysis maturation experiments suggests that kerogen h c ratios are excellent indicators of thermal maturity for end member kerogen types these data also offer a method to estimate percent organic matter conversion provided that both the initial and present h c ratios of the kerogen are known present h c ratios can be measured and initial h c ratios can be reasonably estimated from microscopic organic analysis of kerogen for oil prone source rocks typical immature type i kerogens have h c ratios of 1 35 1 50 whereas type ii kerogens have h c ratios of 1 20 1 35 correlations of the amount of expelled oil in hydrous pyrolysis experiments to atomic h c ratio of the spent kerogen offer exploration geologists a quick estimate of oil expulsion volumes based on hydrous pyrolysis experiments measured h c ratios and calculated original toc total organic carbon values first order volumetric approximations were made on three basins containing mature source rocks results compared favorably with published approximate oil in place estimates for the williston basin bakken shale los angeles basin nodular shale and the illinois basin new albany shale

seismic characterization of multiple fracture sets at rulison field colorado conventional fracture characterization methods assume the presence of a single set of aligned vertical cracks in the subsur face we relax this assumption and demonstrate the feasibility of seismic characterization of multiple fracture sets our technique relies on recent numerical findings indicating that multiple differently oriented possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic or orthotropic effective medium here the governing parameters of crack induced orthotropy are estimated from 3d wide azimuth multicomponent seismic reflection data acquired over the tight gas rulison field in colorado we translate strong azimuthal variations of the normal moveout velocities intointerval crack densities fracture orientations type of fluid infill and velocities of p and s waves in an unfractured rock our inversion procedure identifies a set of cracks aligned in approximately west northwest east southeast direction in the western part

sediment trapping turbidity maxima and bathymetric stability in macrotidal estuaries 1 this paper examines how fine marine sediments are trapped in macrotidal estuaries and what processes coexist to maintain bathymetric stability an analytical emulator is constructed integrating explicit formulations for tidal and residual current structures together with sediment erosion suspension and deposition the emulator estimates suspended concentrations and net sediment fluxes and indicates the nature of their functional dependencies and corresponding sensitivities to tidal elevation amplitude or tidal current channel depth d bed friction coefficient f sediment size specifically settling velocity ws and river flow velocity ur associated scaling analyses reveal the relative impacts of terms representing tidal nonlinearities gravitational circulation and delayed settling using the emulator to determine conditions consistent with zero net flux of sediments or bathymetric stability we deduce ws f overall finer sediments are imported and coarser ones are exported with more imports extending to a coarser fraction on spring tides than on neaps the emulator indicates that the spring neap shifting of this coarse fine boundary corresponds to particle diameters between 30 and 50 m this constitutes selective sorting maintaining a widely distributed source of continuously resuspended material in a size range commonly observed by illustrating the acute sensitivity of sediment fluxes to the bed friction coefficient we anticipate feedback adjustments between suspended and surficial sediments factors governing the generation location and characteristics of turbidity maxima are indicated including dependence on d a direct link is shown between parameters that control sediment flux at a specific cross section and net upstream tidal energy dissipation

mo ni and organic carbon isotope signatures of the mid late mesoproterozoic oxygenation abstract this study performed a redox sensitive trace element rste and organic carbon isotope investigation on the shallow section of 1 2 ga bijaigarh shale kaimur group vindhyan supergroup the results demonstrate that unlike the coeval deeper section in which mo and ni concentrations are several folds higher compared to the upper continental crust ucc the shallow section contains mo and ni equivalent to the upper continental crust ucc this spatially heterogeneous burial of mo and ni is very similar to the modern stratified basins i e black sea and cariaco basin where ni and mo composition of the sediments underlying a shallow oxic water column is comparable to the ucc however the deeper sediments underlying the anoxic euxinic contains several folds higher mo and ni compared to the ucc bulk precipitation of mo in a hydrosphere is mainly controlled by sulphide present in the anoxic euxinic layers of the water column on the other hand ni precipitation is generally controlled by oxygenic primary productivity though the shallow section of the bijaigarh shale is depleted in ni a significant correlation between ni and toc is still relevant and indicates an oxygen rich surface water layer for the respective palaeohydrosphere furthermore 13c org values between 32 0 and 30 4 from the shallow section suggests that the organic carbon exported into the sediments during the bijaigarh shale deposition was primarily derived from oxygenic photosynthesis in the concurrent surface water layers

relationships between tidal dynamics and bathymetry in strongly convergent estuaries abstract localized analytical solutions are derived for the propagation of a single predominant tidal constituent in estuaries with strongly convergent triangular cross sections the advective term is neglected and the friction term is linearized the solutions apply at any locality where the cross sectional shape remains sensibly congruent and the spatial gradient of tidal elevation amplitude is small i e synchronous then for specified tidal elevation amplitude and water depth d these solutions indicate values of tidal current amplitude u ratio of friction to inertial terms slope of the estuarine bed rate of energy dissipation and phase difference between and u illustrations of these results over a range of and d provide reference frameworks to assess observed conditions at any position in any estuary satisfying the criteria cited they may also indicate the range of parameters likely to be consistent with bathymetric equilibrium in dynamic sedimentary regimes the ratio of fr

paleogeographic evolution of early deep water gulf of mexico and margins jurassic to middle cretaceous comanchean the paleobathymetric configuration of the early gulf of mexico is inferred from 1 cretaceous carbonate shelf margins interpreted from seismic profiles and other stratigraphic data 2 distribution of jurassic and cretaceous platform and basinal facies and 3 hindcasting of subsidence history in the central basin substantial paleogeographic ambiguity results from uncertainty about 1 kinematics and timing of late triassic to jurassic extensional opening of the gulf basin which probably involved major strike slip faulting 2 the magnitude of subsequent compressive deformation on the western and southern basin margins and 3 possible accretion of allochthonous terranes the initial sub sea level topographic depression created by crustal extension is manifested by the distribution of callovian pre marine salt and oxfordian basinal marine facies late jurassic sea floor spreading split the main salt body and created a central deep water 1 km trough from the oxfordian to early neocomian ramp like platform margins generally underwent net retreat except in the northern gulf where major clastic progradation took place carbonate platform margins with sufficient paleorelief for geometric expression on seismic profiles developed early in the cretaceous these cretaceous carbonate margins exhibit a variety of architectural styles including 1 in the northwestern gulf two cycles of progradation coahuilan and comanchean terminated by drowning events 2 in the southwestern gulf a single cycle of progradation 3 continuous aggradation along the florida and campeche escarpments paleobathymetric relief across cretaceous carbonate margins ranges from high and steep to low relief to ramplike the close of comanchean drowning event greatly and permanently reduced the extent of circum gulf carbonate platforms and especially rimmed margins locations of cretaceous carbonate margins were influenced by basement hinge zones and paleohighs developed on attenuated continental crust by the distribution of salt and by clastic progradation eustacy is commonly invoked to explain behavior and architecture of carbonate margins in the gulf but other paleoenvironmental variables such as nutrient abundance are probably important as well

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