an early permian coastal flora dominated by germaropteris martinsii from basinal sediments in the midland basin west texas abstract fossils found in cores from wells in the midland basin of west texas include several kinds of terrestrial plants and a variety of marine animal remains depositional settings ranged from basin slope to deep water basin floor hence the presence of land plants was unexpected the fossil plant assemblage is depauperate dominated by germaropteris martinsii a permian age peltasperm other specimens include the peltasperm supaia sphenopteris germanica axes of uncertain affinity and incertae sedis remains presumed to be terrestrial plants fossil plants are found predominantly in fine grained siliceous mudrocks between coarser grained calcareous floatstones and wackestones packstones interpreted as debrites and turbidites suggesting that the plants were carried from land by surface currents before sinking to the basin floor and being buried by slowly accumulating hemipelagic sediment specimens were examined from drillcores in 14 wells spanning an interval from the lower wolfcamp through the lower leonard this record of g martinsii in lower permian wolfcamp rocks is among the earliest occurrences of these plants which have been found most abundantly in upper permian strata of western europe

palaeoclimate change recorded in upper cretaceous albian cenomanian kazhdumi formation borehole spectral gamma ray logs south pars gas field persian gulf abstract th u and th k data from spectral gamma ray logs obtained from outcrop successions have been used as a rapid and inexpensive proxy for determining possible episodes of humid arid palaeoclimate change such outcrop based measurements have never been tested using spectral gamma ray data obtained from wireline logs in subsurface boreholes th k and th u ratios have traditionally been used to decipher sequence stratigraphic patterns at outcrop and in borehole the possible influence of palaeoclimate on such ratio changes has yet to be proven especially from borehole data in this work we compare borehole derived th k and to a lesser extent th u to palaeoenvironmental changes inferred from palynology and deduce that both sea level and changing hinterland weathering regimes caused discrete fluctuations observed in the spectral gamma ray logs this is the first time such subsurface information has been used in this way interpretation of wireline logs in terms of palaeoclimate as well as sea level may now be considered and the use of such logs in palaeoclimate reconstruction is strengthened

seismic architecture of a lower cretaceous platform to slope system santa agueda and poza rica fields mexico two three dimensional seismic data sets over the albian western golden lane margin and time equivalent basinal deposits of poza rica field allowed us to investigate the linked architecture of a steep sided carbonate platform el abra formation and a thick accumulation of redeposited carbonate sediment at the toe of the slope and in the basinal area tamabra formation regional seismic cross sections show that the most aggrading albian platform has an eroded platform top a scalloped margin and a channelized slope that are equivalent to a 20 km 12 4 mi wide westward thinning thick toe of slope apron made of chaotic contorted mounded moderate to high amplitude reflections detailed reflection geometries in the albian toe of slope and basinal deposits consist of chaotic to short discontinuous low amplitude reflection at the toe of the slope of the golden lane platform laterally changing to a discontinuous mounded shingling reflection which ultimately turns into high amplitude parallel reflections we interpret this lateral change to reflect the seismic signature of the change from the block and debris flow dominated toe of slope area to debris flow and concentrated density flow deposits in the basin that ultimately grade laterally into pelagic deposits on a flattened seismic slice mounded reflections correspond to lobate to fan shaped seismic events several kilometers wide that are interpreted as a carbonate basin floor fan comparison between core and seismic data shows a dominance of debris flows in the lower two albian sequences albian 1 and albian 2 that grade vertically into more lobate concentrated density flows and turbidites in the upper two albian sequences albian 3 and albian 4 seismic data used in this study combined with core observations do not support the interpretation of the albian tamabra formation being of shallow water origin seismic features identified as basin floor fan channel and debris flow deposits have a shape and size that are similar to those of other redeposited basinal carbonate deposits elsewhere the seismic architecture shows that the poza rica field is a typical example of thick accumulation of grainy porous carbonate deposits in a basinal setting this example shows the potential of a large hydrocarbon accumulation in a tectonically modified stratigraphic trap around shallow water carbonate platforms

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

source rock distribution and maturation in the zagros orogenic belt provenance of the asmari and bangestan reservoir oil accumulations abstract the zagros orogenic belt of iran is one of the most prolific petroliferous areas accounting for approx 12 of proven global reserves correlation techniques reveal that a majority of the oils variously reservoired in asmari oligo miocene and bangestan group upper cretaceous anticlinal structures share a common provenance oils of the n e khuzestan fields are an exception showing a conspicuously different origin candidate source potential for the crucial central zagros embayment and contiguous areas was assessed on field survey and from well materials collected during the decade from 1968 onwards although varying locally in vertical and lateral distribution attractive sources occur throughout the section included were silurian shales the sargelu middle jurassic garau gadvan lower cretaceous kazhdumi albian gurpi upper cretaceous and pabdeh paleogene fms maturation of these source units was essentially controlled by the foredeep subsidence related to the zagros orogeny being a neogene event hydrocarbon generation and migration are very recent and essentially synorogenic consolidation of this information with the real distribution of candidate sources application of carbon isotope based source oil assignments and biomarker results successfully differentiated the provenance of the generic oil groupings over much of khuzestan the kazhdumi was recognised as the major contributor elsewhere the pabdeh fm yields isotopically distinctive oils in n e khuzestan evaluation of this basin allowed identification of prolific source rocks in low energy euxinic argillaceous lime mudstones similarly it provided an early application of pyrolysis techniques carbon isotopic correlations and subsidence history maturation migration modelling approaches now routinely employed in basin evaluation

three dimensional geological and synthetic seismic model of early permian redeposited basinal carbonate deposits victorio canyon west texas the lower permian outcrops of victorio canyon in the sierra diablo mountains in west texas show undisturbed stratigraphy of carbonate toe of slope and basinal deposits these rocks consist of a vertical stack of carbonate debris flow deposits and hyperconcentrated density flow deposits thick skeletal ooid grainstone deposited as basin floor fans various reworked muddy carbonate deposits and fine siliciclastic siltstones this succession was deposited within five sequences that include the upper hueco formation late wolfcampian through the bone spring formation middle leonardian using a ground based light detecting and ranging generated high resolution digital outcrop model dom aged as a template we mapped and digitized the stratigraphy of the toe of slope and basinal deposits on the 5 cm 2 in precision dom on the basis of the digitized stratigraphic contacts several regional surfaces were constructed and a 3 d geocellular model was built facies information within this model is extrapolated from measured section data using both a kriging algorithm and stochastic simulations using impedance values extracted from a subsurface analog a 3 d impedance model was created for both the kriged and the stochastic models both models incorporate fine scale stratigraphic architecture in addition the stochastic impedance model incorporates spatially correlated noise resulting in more realistic synthetic seismograms three dimensional synthetic seismograms were calculated at 20 40 and 80 hz the reservoir prone facies is skeletal ooid grainstone deposited as a 1 5 km 750 m 0 93 mi 2460 ft basin floor fan up to 15 m 49 ft thick this basin floor fan is subtly imaged in vertical seismic section at a frequency below 80 hz it is however better recognized on time slices with peak frequency as low as 20 hz and even better delineated on horizon slices that parallel the stratigraphy

impact of strong easterly trade winds on carbonate petroleum exploration relationships developed from caicos platform southeastern bahamas abstract brisk persistent easterly trade wind influences define holocene patterns of carbonate sedimentation across the caicos platform southeastern bahamas resultant predictive sedimentary facies models based on trade wind influences are more widely applicable to the exploration for subsurface carbonate plays than are existing models based on the northern bahamas facies patterns which are characterized by gentle trade winds and strong platform margin related oceanic processes swells and tidal currents the caicos platform relationships may be more applicable because many ancient shallow carbonate depositional environments were within the trade wind belts and commonly within broad intracratonic seas that were little influenced by oceanic processes the grainstone dominated caicos platform exhibits reservoir potential over much of its surface in contrast to northern bahamian platforms where oceanic tidal currents or swells and gentle easterly trade winds confine higher energy environments with reservoir potential to platform margins strong easterly trade winds across caicos platform promote widespread holocene platform interior oolitic skeletal and grapestone grainstone bodies on this platform orientations of ooid sand bodies vary depending on preexisting topography water depth and bottom energy shallow subtidal ooid sand shoals orient parallel to these winds ooid sands developed along older shorelines orient parallel to the shorelines but prograde perpendicular into these winds deeper platform interior oolitic sands exist as widespread sheet like deposits these trade winds allow reefs and ooids to coexist in many settings permit isolated linear reefs to flourish on certain leeward platform margins and promote effective off bank transport of carbonate sands that create onlapping grainstone wedges these relationships are very applicable to the rock record strong trade wind influences such as seen on caicos platform better explain the occurrence of cretaceous reef and or oolitic grainstone reservoirs developed well in from platform margins fairway field in east texas black lake field in louisiana than do existing northern bahamian models depositional models based on conditions in the northern bahamian models would predict low energy facies in these platform interior settings a trade wind driven depositional model characterized by strong persistent easterlies also better explains the origin of the onlapping wedge of skeletal grainstones at poza rica oilfield in mexico the caicos platform easterly trade wind driven depositional model should generally apply to any ancient shallow carbonate environment that developed 5 22 north or south of the paleoequator whether or not a platform margin was near by future carbonate exploration or exploitation should always factor in not only geological age but also physiographic latitudinal and climatic setting at a global and local scale

palynofacies and geochemical analysis of the triassic yanchang formation ordos basin implications for hydrocarbon generation potential and the paleoenvironment of continental source rocks abstract the petroliferous basins that have formed in china since the mesozoic are characterized by non marine organic matter input a characteristic that is significantly different from that of marine organic sources the triassic yanchang formation in the ordos basin is a suite of typical intra continental lacustrine sediments that comprise the most important source rocks for the triassic oil reservoirs the yanchang formation is divided into ten subsections from top to bottom chan 1 to chan 10 three borehole successions in the southern ordos basin located in the huachi zhidan and yichuan areas cross the chan 4 5 to chan 10 subsections and have been studied using the palynofacies method combined with organic geochemistry data palynofacies analysis indicates that the sediments are rich in amorphous organic matter aom and phytoclasts the aom content in all of the samples positively correlated with the hydrogen index hi in contrast the transparent ligno cellulosic fragments tlf opaque particles op content are negatively correlated with the hi values additionally the gelified particles gp content has no linear correlation with the geochemistry data based on the quantitative composition of the particulate organic matter three palynofacies types are identified reflecting depositional settings in a distal dysoxic anoxic deep basin a shelf to basin transition zone and a proximal suboxic shelf the palynofacies total organic carbon toc and rock eval data together indicate that type i and ii kerogen are abundant in the d48 and w22 wells in the zhidan and yichuan areas respectively these kerogen types are uncommon in the l94 well in the huachi area which suggests low hydrocarbon generation potential in detail the chan 7 and chan 9 subsections of the three wells contain abundant type i and ii kerogen indicating that these layers are likely the two primary source rocks in the southern ordos basin

play analysis and leading edge oil reservoir development methods in the permian basin increased recovery through advanced technologies the permian basin of west texas and southeast new mexico remains an important oil producing province accounting for 17 of united states production 327 million bbl in 2002 with a resource base of such size increased understanding of reservoir geology and improved use of enhanced recovery practices in the basin can have a substantial impact on united states oil production thirty two oil plays covering both the texas and new mexico portions of the permian basin were defined on the basis of reservoir stratigraphy lithology depositional environment and structural and tectonic setting one thousand three hundred and thirty nine significant sized reservoirs cumulative production of 1 million bbl 1 59 105 m3 of oil through 2000 were assigned to a geologic play cumulative production from these reservoirs was 28 9 billion bbl 4 59 109 m3 or 95 of the basin s total examples of successful reservoir development practices are listed by play because methods demonstrated to work well in one reservoir should be applicable to other reservoirs in the play the permian basin is dominantly a carbonate province carbonate reservoirs account for 75 of total oil production clastics 14 mixed clastics and carbonates 8 and chert 3 the plays having the largest cumulative production are the northwest shelf san andres platform carbonate play 4 0 billion bbl 6 31 108 m3 the leonard restricted platform carbonate play 3 3 billion bbl 5 25 108 m3 the pennsylvanian and lower permian horseshoe atoll carbonate play 2 7 billion bbl 4 29 108 m3 and the san andres platform carbonate play 2 2 billion bbl 3 42 108 m3 the permian system dominates production accounting for 73 of cumulative production followed by the pennsylvanian 13 and the ordovician 6 the estimated remaining reserves from that component of the resource base that is already discovered and producing is 3 25 billion bbl 5 17 108 m3

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

inverse magnetic fabric in carbonate bearing rocks abstract the observation of a magnetic susceptibility ellipsoid whose maximum axis corresponds to the minimum axis of petrofabric pole of bedding or schistosity is referred to as an inverse magnetic fabric the investigation of the magnetic properties of some ferroan carbonate monocrystals and paramagnetic limestones demonstrates that c axis preferred orientation of paramagnetic carbonates results in a maximum susceptibility parallel to the flattening direction inverse magnetic fabrics due to magnetite are also encountered in weakly deformed limestones a mineralogical model based on the property of single domain grains to have a zero susceptibility parallel to their long axis is proposed however more complex cases are also encountered

permian wolfcamp limestone reservoirs powell ranch field eastern midland basin deep water carbonate channel reservoirs form important oil reservoirs along the toe of the eastern shelf of the permian basin in west texas in northwestern glasscock county these wolfcamp reservoirs are leonardian early permian in age and define high energy channels incised into surrounding carbonate detritus and basinal shale porous grain flow material filling these channels along with encasing detritus was derived from the shallow shelf located six miles to the east reservoirs are in packstone and grainstone facies and have significant interparticle and moldic porosity relevant exploration began in the 1960s but expanded slowly thereafter due to lack of success caused by complex patterns of channel occurrence results of a three dimensional 3 d seismic survey conducted in 1990 have greatly enhanced the identification and mapping of productive channels in the powell ranch field complex wells in this complex are capable of flowing 400 1200 bbl of oil per day and have reserves ranging from 0 2 to 1 3 mbo the new 3 d data have improved the relevant geologic model and dramatically increased rates of drilling success application of such data to this setting offers a potential model for other parts of the permian basin

permian wolfcamp limestone reservoirs powell ranch field eastern midland basin discussion the open quotes ep however its economic importance and geological complexity and the question of whether his model can be extended to other areas in the permian basin warrant this discussion

magnetic fabric and flow direction in basaltic pahoehoe lava of xitle volcano mexico abstract we sampled five basaltic lava flow units from xitle volcano mexico city to study the variation of anisotropy of magnetic susceptibility within their cooling boundaries we find that the mean maximum susceptibility parallels the geologically inferred flow direction in the units that were emplaced on a steeper slope whereas for those on a negligible slope the mean intermediate susceptibility points in the flow direction we propose however that the maximum susceptibility always points in the direction of local movement and that a change in slope produces a deviation of the local motion from that of the unit as a whole the axis of susceptibility closest to the geologically inferred flow direction usually plunges upflow in the basal part of the flow unit comprising an imbrication which clearly marks the flow azimuth of the lava thus the scenario of emplacement may influence the results in a predictable way we suggest that the degree of anisotropy could bear a direct relationship to either the viscosity of the lava the morphology of the flows or both based on a comparison with lavas from azufre argentina and ko olau o ahu volcanoes also we suggest that the shape of the susceptibility ellipsoid may be related to the degree of internal deformation of the lava flows we also compare the two methods currently available to calculate regions of confidence around the mean principal susceptibilities

tectonic controls on residual oil saturation below the present day fluid contact level in reservoirs of the persian gulf abstract the presence of residual oil below the present day free water level fwl and oil water contact owc is common in many oil fields in the middle east particularly those in the persian gulf this residual oil is seen in both clastic and carbonate reservoirs prior to the start of production the characterisation and modelling of these fields is difficult in practice also these residual oils below the fwl and owc could become classified as reserves if ways to produce them could be found however the first step is to better understand their origin therefore the goal of this study was to investigate the role of geological events on the presence of the residual oil zone roz below the fwl and owc it has been suggested that the presence of residual oil below the present day fwl and owc is related to the geotectonic history of the region from the middle miocene reverse faulting and overfolding propagated over the zagros leading to the amplification of folds and the migration of the zagros orogeny towards its foreland basin persian gulf in response to this additional massive loading on the continental margin the forebulge amplitude was increased its location migrated towards the uplifted zagros mountains and consequently the persian gulf became narrower this exerted a north to north east downward tilting of the entire basin including all the structures and reservoirs previously filled by hydrocarbons this basin tilting changed the equilibrium of the structures and their fluid contents and resulted in the hydrocarbons and water attempting to find a new equilibrium under these conditions the early migrated and accumulated oil was flushed out by water imbibition and a roz was left below the present day fwl and owcs the angle of regional basin tilt has been calculated to be 0 836 based on seismic sections

comprehensive source rock evaluation of the kazhdumi formation in the iranian zagros foldbelt and adjacent offshore abstract the kazhdumi formation is regarded as one of the most prolific hydrocarbon sources in the zagros foldbelt and adjacent offshore rock eval pyrolysis data were collected from 2300 rock samples of the kazhdumi formation in 64 wells core and cutting including 37 oil and gas fields and five outcrops 200 vitrinite reflectance measurements were carried out to calibrate and map thermal maturity over the study area palynofacies analyses and thermal history modeling were applied on the wells located in the study area based on the total organic carbon toc map the kazhdumi formation toc values range from 0 to 11 in the central part of dezful embayment its average value is about 5 while average toc value of the kazhdumi formation is lower than 0 5 in qatar gawbandi paleo high hydrogen index hi values represented types ii and iii kerogen for central part of the dezful embayment and qatar gawbandi paleo high respectively t max ranges from 370 to 455 c in the study area the maximum and minimum values for this parameter are recorded in the central dezful embayment and central persian gulf anticlines respectively vitrinite reflectance vr r map also confirms the concluded results of t max data reconstructed burial history and thermal modeling of three wells are also in full agreement with the results of other maturity evidence t max and vr r palynofacies analyses revealed that this formation in the central persian gulf south pars field clearly represents the dominance of terrigenous elements which were resulted from a close proximity to a fluvio deltaic source however towards the northwest amorphous organic matter aom dominates in central dezful embayment indicating a distal dysoxic anoxic environmental condition

depositional settings and palynofacies assemblages of the upper triassic fluviodeltaic mungaroo formation northern carnarvon basin western australia

evaluating the depositional environment lithofacies variation and diagenetic processes of the wolfcamp b and lower spraberry intervals in the midland basin implications for reservoir quality and distribution detailed facies characterization in the wolfcamp b and lower spraberry intervals of two drill cores in the midland basin has yielded five main lithofacies with distinctive physical chemical and biologic attributes the main attributes for facies identification include lithology and or mineralogy texture and or fabric porosity hydrogen index and total organic carbon content the methodologies are focused on detailed core description thin section petrography quantitative x ray diffraction and field emission scanning electron microscopy sem porosity data are primarily based on gas research institute core laboratories measurements and field emission sem assessment moreover the depositional and diagenetic controls on facies development are addressed to assess the dominant geological processes that govern reservoir quality and distribution a model of five end member facies is proposed to characterize source and reservoir elements through delineating facies tracts the five end member facies are as follows facies 1 silty mudstone optimal source and optimal to fair reservoir facies 2 muddy siltstone optimal source and optimal reservoir facies 3 silty calcareous mudstone good source and good reservoir facies 4 bioclastic wackestone floatstone fair source and fair reservoir and facies 5 packstone grainstone poor source and poor to excellent reservoir the proposed facies scheme aims to provide a more comprehensive approach to capture the high vertical and lateral variability in this mixed carbonate and fine grained clastic succession through this detailed textural compositional sedimentologic and diagenetic approach this facies model can be used to better understand reservoir quality and distribution throughout the midland basin

organic geochemistry and petrography of kazhdumi albian cenomanian and pabdeh paleogene potential source rocks in southern part of the dezful embayment iran there are several source rock units in the zagros basin but the cretaceous kazhdumi and paleogene pabdeh formations probably have produced the majority of the commercial hydrocarbons in this area among the hydrocarbon provinces of iran the dezful embayment which is located southwest of zagros mountains is one of the most prolific regions in the middle east numerous studies have been made in the northern part of the dezful embayment but relatively few have been done in its southern part the present study focuses on organic matter characterization of two potential source rocks kazhdumi and pabdeh formations in southern part of the dezful embayment cuttings samples 114 were collected from 10 wells and evaluated using rock eval pyrolysis and organic petrography in order to characterize the content and type of organic matter and thermal maturity the results showed that the average total organic carbon toc content of kazhdumi and pabdeh formations are 2 48 and 1 62 wt respectively the highest toc contents for both formations are found in the northern compartment and decreased gradually toward the south pyrolysis data reveal that organic matter has a fair to very good hydrocarbon generation potential and are classified as type ii iii and type iii rock eval t max and vitrinite reflectance show that the majority of samples are in the early mature to mature stage of the oil generation window c 2012 elsevier ltd all rights reserved

neogene sediments and modern depositional environments of the zagros foreland basin system a sedimentological investigation of the neogene deposits of the zagros foreland basin in sw iran reveals a continuous and largely gradational passage from supratidal and sabkha sediments at the base represented by the gachsaran formation to carbonates and marine marls mishan formation with basal guri carbonate member followed by coastal plain and meandering river deposits agha jari formation and finally to braided river gravel sheets bakhtyari formation this vertical succession is interpreted to represent the southward migration of foreland basin depozones from distal foredeep and foredeep to distal wedge top and proximal wedge top respectively as the zagros fold thrust belt migrated progressively southward towards the arabian foreland this vertical succession bears a striking similarity to modern depositional environments and sedimentary deposits observed in the zagros region today where one passes from mainly braided rivers in the zagros mountains to meandering rivers close to the coast to shallow marine clastic sediments along the northern part of the persian gulf and finally to carbonate ramp and sabkha deposits along the southeastern coast of the persian gulf this link between the neogene succession and the modern day depositional environments strongly suggests that the major neogene formations of the zagros foreland basin are strongly diachronous as shown recently by others and have active modern day equivalents

early permian deep water allochthonous limestone facies and reservoir west texas conventional cores from six wells in southwest reagan and northern crockett counties texas recovered interbedded limestone conglomerate intraclast and bioclast limestone calcarenite and shale twenty one lithologies are grouped into six lithofacies based on study of slabbed core surfaces lithoclast rudstone floatstone porous bioclast lithoclast rudstone floatstone bioclast wackestone intraclast floatstone rudstone thin bedded grainstone packstone calcarenite and dark gray shale the limestone facies are interpreted on the basis of petrologic characteristics biota regional stratigraphic setting and facies stratigraphy as deep water and allochthonous biotic constituents within the lithoclasts and matrix indicate an early permian wolfcamp age the porous bioclast lithoclast rudstone floatstone facies contains a modest but geologically significant oil reservoir at gunnx field southwest reagan county production is from 10 ft 3 m of perforations in about 42 ft 13 m of pale yellow brown porous limestone with intercrystalline reduced and solution enlarged biomoldic intraskeletal fracture and possible intergranular porosity moldic porosity appears to be mainly within lithoclasts baroque dolomite is rare to common and partly to completely fills former void space in addition to calcite spar and micrite porosity generally ranges 7 18 the producing depth is about 9 450 ft 2 880 m and the trap is stratigraphic the cored sequence at gunnx is interpreted as a basin floor complex of debris flow sheets which contain the reservoir overlain by interbedded thin carbonate turbidites thin debris flow sheets and shale the lowermost debris flow at gunnx was deposited on a thin generally undated shale the lower part of which is late pennsylvanian at west world field the shale is interpreted as representing starved basin floor deposition and abruptly overlies shallow water strawn limestone in core at west world field carbonate detrital components in the limestone at gunnx were probably derived from a wolfcamp platform at least 10 mi 16 km west and were emplaced by various submarine gravity flow processes age and facies determinations from cores in the gunnx area significantly alter earlier stratigraphic interpretations made with wireline logs alone late paleozoic allochthonous carbonate facies may provide significant new reserves in the permian basin

palynology and petroleum potential of the kazhdumi formation cretaceous albian cenomanian in the south pars field northern persian gulf abstract the kazhdumi formation of the bangestan group is a well known source rock that has produced abundant oil in most petroleum fields in the zagros basin which stretches from northwest to southwest iran over hundreds of kilometres the formation reaches a thickness of 230 m at the type section in northwest zagros but thins out to 40 50 m in wells studied from the south pars giant petroleum field where it comprises mainly grey shales with occasional intercalations of marls and sandstones south pars best known as the iranian part of the world s largest non associated gas field contains small quantities of oil above and below the kazhdumi formation palynology has been used to assess the age and palaeoenvironment of the kazhdumi formation and to evaluate its petroleum potential a total of 68 ditch cutting samples recovered from five wells of which four are oil prone have been analyzed an age between late albian and cenomanian is established for the formation based on dinoflagellate cyst biostratigraphy and four palynofacies types have been recognized using the relative proportions of terrestrial elements marine palynomorphs and amorphous organic matter aom the ratio of terrestrial to marine elements is high in most samples indicating a nearshore sedimentary environment twenty two samples from the four oil prone wells were also selected for geochemical analysis using rock eval pyrolysis results show that the kazhdumi formation at south pars in contrast to the zagros basin is gas prone predominantly type iii kerogen thermally immature and poor in terms of hydrocarbon generation it could not have produced the oil in those oil prone wells studied

palynological palynofacies paleoenvironmental and organic geochemical studies on the upper cretaceous succession of the gptsw 7 well north western desert egypt abstract the present study of the abu roash and bahariya formations in well gptsw 7 refines our understanding of the subsurface cretaceous of the north western desert of egypt our investigations are based on the palynological analyses of 71 cuttings samples of which 24 have also been analyzed for geochemistry in addition to 3 sidewall cores analyzed for vitrinite reflectance r o four palynological zones and three subzones in addition to a poorly fossiliferous interval ranging in age from coniacian santonian to early cenomanian are proposed these include a poorly fossiliferous interval coniacian santonian dinogymnium vozzhennikovae interval zone late to middle turonian ephedripites ambiguus ephedripites multicostatus foveotricolpites giganteus foveotricolpites gigantoreticultus assemblage zone early turonian classopollis brasiliensis interval zone late to middle cenomanian and afropollis jardinus interval zone early cenomanian the succeeding subzones are afropollis kahramanensis interval subzone elaterosporites klaszii interval subzone and cretacaeiporites densimurus interval subzone all of early cenomanian age total organic carbon toc and rock eval pyrolysis and palynofacies analyses indicate that the bahariya formation and the abu roash g member are primarily of kerogen iii type and hence gas prone suggesting a strong influence of hydrogen enriched organic matter the abu roash a c e members may also be gas prone type iii kerogen and appear to contain highly oxidized terrestrial organic matter in contrast the abu roash f member has very high toc and hi values and contains a very high proportion of amorphous organic matter aom indicating a highly oil prone facies while this finding is not unexpected for anoxic black shale it contrasts with earlier studies that suggest a gas prone nature r o measurements show that the bahariya formation represents an immature early genesis dry gas phase this is also true for all investigated samples from the abu roash and bahariya formations based on their low thermal alteration index tai quantitative and qualitative analyses of both the palynoflora and palynofacies show that the abu roash a and c members b is missing both of coniacian santonian age represent oxic proximal and distal shelf environment the abu roash d and e members dated as turonian represent oxic proximal shelf whereas the cenomanian abu roash f member was deposited in a distal suboxic anoxic basin the cenomanian abu roash g member and the bahariya formation were deposited in a shallow marine and shallow marine to fluvio deltaic setting respectively the senonian palmae province is recognized in the palynoflora by the presence of proteacidites auriculiidites reticulatus ariadnaesporites gabonisporis vigourouxii on the other hand the albian cenomanian elaterates province is characterized by the presence of steevesipollenites gnetaceaepollenites elaterocolpites elaterosporites elateroplicites senegalosporites sofrepites afropollis and cretacaeiporites

the cretaceous source rocks in the zagros foothills of iran an example of a large size intracratonic basin the zagros orogenic belt of iran is one of the world most prolific petroleum producing area however most of the oil production is originated from a relatively small area the 60 000 km sup 2 wide dezful embayment which contains approximately 12 of the proven oil global reserves the distribution of the oil and gas fields results from the area extent of six identified source rock layers their thermal history and reservoir cap rock and trap availability in this paper the emphasis is three of the layers of cretaceous sources rocks the garau facies was deposited during the neocomian to albian interval over lurestan northeast khuzestan and extends over the extreme northeast part of fars the kazhdumi source rock which deposited over the dezful embayment and eventually the senonian gurpi formation which has marginal source rock characteristics in limited areas of khuzestan and northern fars the deposition environment of these source rock layers corresponds to semipermanent depressions included in an overall shallow water intracratonic basin communicating with the south tethys ocean these depressions became anoxic when climatic oceanographical and geological conditions were adequate i e humid climate high stand water influxes of fine grained clastics and the existence of sills separating the depressionmore from the open sea distribution maps of these source rock layers resulting from extensive field work and well control are also given the maturation history of source rocks is reconstructed from a set of isopachs it was found that the main contributor to the oil reserves is the kazhdumi source rock which is associated with excellent calcareous reservoirs less

calciclastic submarine fans an integrated overview abstract calciclastic submarine fans are rare in the stratigraphic record and no bona fide present day analogue has been described to date possibly because of that and although calciclastic submarine fans have long intrigued deep water carbonate sedimentologists they have largely been overlooked by the academic and industrial communities to fill this gap we have compiled and critically reviewed the existing sedimentological literature on calciclastic submarine fans thus offering an updated view of this type of carbonate slope sedimentary system calciclastic submarine fans range in length from just a few to more than 100 km three different types can be distinguished 1 coarse grained small sized most calciclastic submarine fans were formed on low angle slopes and were sourced from distally steepened carbonate ramps subjected to high energy currents under these conditions shallow water loose grainy sediments were transferred to the ramp slope and eventually funnelled into the submarine fan by sediment gravity flows these conditions seem to have been more easily met on leeward margins in which the formation of reefs was hampered by cool waters nutrient enrichment or oligophoty another circumstance that contributes to the transfer of shallow water sediments to the distal ramp slope is a low sea level forcing the carbonate factory closer to the slope break and destabilizing sediments by increased pore water pressure however the most important factor controlling the development of calciclastic submarine fans was the existence of an efficient funnelling mechanism forcing sediment gravity flows to merge downslope and build up a point sourced sedimentary accumulation in most cases this occurred through a major slope depression associated with tectonic structures an inherited topography or large scale mass failures

the origin of oil in the cretaceous succession from the south pars oil layer of the persian gulf the origin of the oil in barremian hauterivian and albian age source rock samples from two oil wells spo 2 and spo 3 in the south pars oil field has been investigated by analyzing the quantity of total organic carbon toc and thermal maturity of organic matter om the source rocks were found in the interval 1 000 1 044 m for the kazhdumi formation albian and 1 157 1 230 m for the gadvan formation barremian hauterivian elemental analysis was carried out on 36 samples from the source rock candidates gadvan and kazhdumi formations of the cretaceous succession of the south pars oil layer spol this analysis indicated that the om of the barremian hauterivian and albian samples in the spol was composed of kerogen types ii and ii iii respectively the average toc of analyzed samples is less than 1 wt suggesting that the cretaceous source rocks are poor hydrocarbon hc producers thermal maturity and ro values revealed that more than 90 of oil samples are immature the source of the analyzed samples taken from gadvan and kazhdumi formations most likely contained a content high in mixed plant and marine algal om deposited under oxic to suboxic bottom water conditions the pristane nc17 versus phytane nc18 diagram showed type ii iii kerogen of mixture environments for source rock samples from the spol burial history modeling indicates that at the end of the cretaceous time pre permian sediments remained immature in the qatar arch therefore lateral migration of hc from the nearby cretaceous source rock kitchens toward the north and south of the qatar arch is the most probable origin for the significant oils in the spol

how a mud dominated ramp changed to a carbonate clastic oil reservoir sea level fluctuations in cretaceous of the central persian gulf abstract mud dominated facies distribution of barremian turonian succession in the northeastern arabian plate in the central persian gulf represents a shallow ramp platform on the basis of petrographical studies core analysis data and gamma ray logs this succession has been studied for facies analysis defining depositional environment sequence stratigraphy and reservoir properties a total of 6 microfacies and 3 petrofacies types are recognized in this succession lagoonal environment was dominated during the deposition of dariyan kazhdumi and sarvak formations the lagoon rapidly changed to a sand shoal by falling sea level and increasing energy level of the depositional environment sequence stratigraphy of barremian turonian succession shows that mud dominated facies have been deposited in tsts and grain dominated facies in hsts of the sequences although grain dominated facies like packstone to grainstone and algal floatstone were spread during the hsts of sequences the changes in the texture and size of the grains had a negligible effect on reservoir quality during this period barremian turonian two major sea level falls caused considerable environmental changes such as platform emergence incised valley fills and clastic sediments influx into the carbonate platform meteoric diagenesis during the falling sea level had a major effect on the reservoir properties of the reservoirs under the sequence boundaries grains matrix and micrite dissolution and subsequent selective blocky and equant calcite cementation strongly modified the primary reservoir properties local dolomitization also enhance the porosity and permeability of the samples while large pores have been filled by cements microporosities remained unfilled until the late stages of diagenesis and burial