evidence for large scale eddy driven gyres in the north atlantic analysis of a recent climatological database for the north atlantic has detailed an extensive large scale recirculation system in the intermediate waters of the north atlantic basin the pressure fields that define this recirculation coupled with the potential vorticity fields associated with the recirculating flow provide observational evidence for basin scale eddy driven flow in the global ocean the recirculations are intimately tied to the waters carried southward by the deep western boundary current and are therefore likely to affect the distribution of climatic anomalies in the north atlantic

khasib and tannuma oil sources east baghdad oil field iraq this work presents new insights of the generation quality and migration pathways of the hydrocarbons in the east baghdad oil field the khasib and tannuma formations in east baghdad are considered as oil reservoirs according to their high porosity 15 23 and permeability 20 45 md in carbonate rocks the hydrocarbons are trapped by structural anticline closure trending nw se gas chromatography analysis on these oil reservoirshave shown biomarkers of abundant ranges of n alkanes of less than c22 c17 c21 with c19 and c18 peaks this suggests mainly liquid oil constituents of paraffinic hydrocarbons from marine algal source of restricted palaeoenvironments in the reservoir the low non aromatic c15 peaks are indicative for slight degradation and water washing oil biomarkers of pr ph 0 85 c31 c30 1 0 location in triangle of c27 c29 sterane c28 c29 of 0 6 sterane oleanane of 0 01 and cpi 1 0 indicate an anoxic marine environment with carbonate deposits of upper jurassic to early cretaceous age four miospores seven dinoflagellates and one tasmanite species confirm affinity to the upper most jurassic to lower cretaceous chia gara and ratawi formations the recorded palynomorphs from the khasib and tannuma formations are of light brown color of tai 2 8 3 0 and comparable to the mature palynomorphs that belong to the chia gara and the lower part of ratawi formations the chia gara formation generated oil during upper cretaceous to early palaeogene and accumulated in structural traps of cretaceous age such as the khasib and tannuma reservoirs the chia gara formation generated and expelled high quantities of oil hydrocarbons according to their toc wt of 0 5 8 5 with s2 2 5 18 5 mg hc g rock high hydrogen index of the range 150 450 mg hc g rock good petroleum potential of 4 5 23 5 mg hc g rock mature tai 2 8 3 0 and tmax 428 443c kerogen type ii and palynofacies parameters of up to 100 aom amorphous organic matters this includes algae deposits in a dysoxic anoxic to suboxic anoxic environment alternative plays are discussed according to the migration pathways

using a cfc effective age to estimate propagation and storage of climate anomalies in the deep western north atlantic ocean 1 1990s chlorofluorocarbon cfc observations are used to estimate an effective age of 20 years for north atlantic deep water nadw at the equator the effective age is found by subtracting a relic age from pcfc 11 age the effective age is several to 10 years younger at the equator than other methods from the effective age equatorward effective spreading rates of 1 2 cm s are found which are similar for the nadw components effective spreading rates take into account recirculation gyres along equator flow and mixing which slow spreading of climate anomalies from the north atlantic to the southern hemisphere the difference between direct velocities and tracer effective spreading rates suggests that the buffering effect due to storage in the western north atlantic and equatorial region is about 20 years even so warming and freshening due to greenhouse gases will be first felt in the deep waters of the western north atlantic

optical characteristics of amorphous kerogens and the hydrocarbon generating potential of source rocks abstract four recurring types of amorphous kerogen are optically identified in petroleum source rock samples and are related to hydrocarbon generating potential defined here as geochemically interpreted oil prone or gas prone at this time a genetic classification is not possible the different amorphous kerogen types are distinguished on the basis of microscopic textural differences type a chunky compact masses with mottled network or weak polygonal textures type b very small dense elongate oval or rounded individual grains type c clumpswith granular fragmented or globular textures type d thin platy or rectangular individual grains geochemistry defined oil prone samples generally contain types a and or d separately or combined geochemically defined gas prone samples rarely contain type a and vary in amounts of types b c and or d the samples in this study contain dominantly one of the four types of amorphous kerogen so the geochemical analyses of the whole rock or bulk concentrated kerogen samples are assumed to be analyses of the dominant amorphous type the samples were chemically analyzed by several techniques to determine the oil or gas generating potential the establishment of relations between specific optical and chemical properties of kerogen types can make visual kerogen analyses more meaningful in predicting the hydrocarbon generation potential of source rocks

assessments of oil characterization source affinities and hydrocarbon dynamic of east baghdad oil fields central iraq abstract bulk properties stable carbon isotopes whole crude gas chromatography and oil mode ratios of sterane and terpanes data of analyzed samples of oil from the cretaceous formation reservoirs of east baghdad oil field are from five producing wells eb21 eb68 eb92 eb5 and eb31 from reservoirs of zubair khasib and tanuma formations they are discussed with aids of characters hopane tricyclic terpane isotopic c13 saturate aromatics and pristine phytane diagrams the analized oil have indicated light and medium oil in the zubair reservoirs and heavy oil for the khasib and tannuma oil with about 15 asphalt and porpherine range of 16 7 35 1 ni and 68 117 ppm giant reservoirs the oil source environment and lithology are of marine algal type ii and deltaic type ii iii that are non biodegraded deposited in anoxic environments of carbonate and shale source maturation at the time of the oil generation aided by pristine phytane and tmax equivalent from mdr methyldibenzothiophene ratio diagrams are showing mature with tmax 430 435 c while source age assessment are taken from c13 and the calculated c28 c29 sterane ratio to be of middle and upper jurassic as well as lower cretaceous age that could be correlated mainly with the chia gara and zubair formations as well as the middle jurassic sargelu formation source rocks for oil that are accumulated in the reservoirs of zubair khasib and tannumah formations source rocks are mainly upper jurassic lower cretaceous chia gara formation with contribution from the middle jurassic sargelu and lower cretaceous zubair formations the richness of the source rocks mostly due to shale rich in toc and the type of kerogen is mixed type ii iii and type iii the formations have good petroleum potentiality pp and the om reaches the early of hydrocarbon generation oil and gas are the most probable product and the generated hydrocarbons can be expelled at this level of thermal maturity which is confirmed by petromod software basin modeling to suggest migration and accumulation during the upper cretaceous time hydrocarbon dynamic in east baghdad oil field are performed using seismic section logs and porosities model assessments of the hydrocarbon generation migration paths and accumulation sites as well as places of enriched oil are used to assess reservoir location and suggestion for drilling sites

processes of 30 90 days sea surface temperature variability in the northern indian ocean during boreal summer during summer the northern indian ocean exhibits significant atmospheric intraseasonal variability associated with active and break phases of the monsoon in the 30 90 days band in this paper we investigate mechanisms of the sea surface temperature sst signature of this atmospheric variability using a combination of observational datasets and ocean general circulation model sensitivity experiments in addition to the previously reported intraseasonal sst signature in the bay of bengal observations show clear sst signals in the arabian sea related to the active break cycle of the monsoon as the atmospheric intraseasonal oscillation moves northward sst variations appear first at the southern tip of india day 0 then in the somali upwelling region day 10 northern bay of bengal day 19 and finally in the oman upwelling region day 23 the bay of bengal and oman signals are most clearly associated with the monsoon active break index whereas the relationship with signals near somali upwelling and the southern tip of india is weaker in agreement with previous studies we find that heat flux variations drive most of the intraseasonal sst variability in the bay of bengal both in our model regression coefficient 0 9 against 0 25 for wind stress and in observations 0 8 regression coefficient 60 of the heat flux variation is due do shortwave radiation and 40 due to latent heat flux on the other hand both observations and model results indicate a prominent role of dynamical oceanic processes in the arabian sea wind stress variations force about 70 100 of sst intraseasonal variations in the arabian sea through modulation of oceanic processes entrainment mixing ekman pumping lateral advection our 100 km resolution model suggests that internal oceanic variability i e eddies contributes substantially to intraseasonal variability at small scale in the somali upwelling region but does not contribute to large scale intraseasonal sst variability due to its small spatial scale and random phase relation to the active break monsoon cycle the effect of oceanic eddies however remains to be explored at a higher spatial resolution

variations in the sterane carbon number distributions of marine source rock derived crude oils through geological time abstract the analysis of the sterane data of a large set of crude oils 414 derivedfrom marine carbonate 27 and siliciclastic source rocks 14 where influences of terrestrial or lacustrine derived organic matter can reasonably be excluded shows that there are increases in the relative content of c28 steranes and decreases in the relative content of c29 steranes through geological time there are no consistent variations in the relative content of c27 steranes through time with one major exception a proterozoic oil from oman palaeozolic and older crude oils are thus generally characterised by strong predominances of c29 steranes and low relative concentrations of c28 steranes significantly higher proportions of c28 steranes and lower proportions of c29 steranes occur in oils derived from jurassic and upper cretaceous source rocks these changes through time do not appear to reflect the chemical evolution of the sterols of one particular variety of marine organism the increase in c28 steranes may be related to the increased diversification of phytoplantonic assemblages in the jurassic and cretaceous possible sources of the c28 sterols necessary for the observed changes in crude oil steranes includes diatoms coccolithophores and dinoflagellates although the technique does not give an accurate means of determining the age of the source rock of a crude oil it is possible to distinguish younger crudes derived from the upper cretaceous and tertiary from palaeozoic and older crudes

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

deep flow along the western boundary south of the blake bahama outer ridge abstract in june july 1990 hydrographic chlorofluorocarbon cfc and velocity observations were taken along the western boundary of the north atlantic south of the blake bahama outer ridge from 30 to 24 n between the northern bahamas and 71 w the deep flow in the region associated with the deep western boundary current forms a pattern of strong narrow currents and cyclonic gyres close to the continental slope with broad slower southward flow offshore the cfcs reveal that the most recently ventilated water i e having the highest cfc concentrations due to more recent contact with the atmosphere in the northern north atlantic is found along the western boundary in two distinct cores between potential temperatures 4 6 c and 1 9 2 4 c geostrophic transport streamlines were constructed for the deep flow referenced using direct velocity observations at 26 5 n and assuming mass conservation between closed areas bounded by the hydrographic sections the tracers and transports are used together

biomarker signatures of the ediacaran early cambrian origin petroleum from the central sichuan basin south china implications for source rock characteristics abstract hydrocarbons with an ediacaran early cambrian origin from the central sichuan basin south china were investigated for biomarker compositions they were obtained by solvent extraction from the upper ediacaran reservoir core samples which contain abundant solid bitumen the solid bitumen is widely believed to be formed by thermal cracking of early charged oils in the reservoirs which have presumed source rocks of an ediacaran early cambrian age thermal maturity parameters based on phenanthrenes and aromatic steroids suggest a very high thermal maturity for the extracted hydrocarbons which is consistent with the severe maturation undergone by their host reservoirs age diagnostic biomarkers including c30 24 isopropylcholestanes and mid chain monomethyl alkanes support source rocks of an ediacaran early cambrian age the extracted hydrocarbons have very similar biomarker signatures which include high relative abundance of acyclic isoprenoids and pristane phytane 1 and the presence of c26 norcholestanes methyl and ethylsteranes the presence of hopanoids including extended series and methylhopanes indicates contributions from prokaryotic bacteria while the presence of various steroids including regular steranes and methylsteranes indicates contributions from the eukaryotic algae parameters based on tricyclic terpane and hopane dibenzothiophene phenanthrene ratios and c27 diasteranes diasteranes regular steranes ratios suggest a major shale source but a mixed shale carbonate source cannot be completely excluded presence of c30 demethylsteranes low pristane phytane ratios high gammacerane index and presence of 28 30 dinorhopane and 2 methyhopanes indicate that the source rocks were deposited in a stratified anoxic marine depositional environment with enhanced salinity conditions

organic petrological and geochemical appraisal of the upper jurassic naokelekan formation kurdistan iraq abstract upper jurassic naokelekan formation being part of the intercepted strata of the well known miran oilfield in kurdistan region of northern iraq has been previously extensively evaluated as a potential effective source rock mainly by means of organic geochemistry in the present study a total of 60 samples were collected from four naokelekan fm outcrops those of banik galy derash barsarin and dwawa in order to conduct organic petrographical study and organic geochemical assessment including both biomarker and rock eval analyses the average recorded toc content for banik galy derash barsarin and dwawa section is considerable to very high corresponding to values of 27 5 9 0 3 5 and 5 2 wt respectively with the highest values representing the notably organic rich bottom part of the formation known as coal layer according to the petrographical analysis solid migrabitumens comprise the predominant component for all the analysed samples whereas the maceral groups of vitrinite liptinite and or inertinite showcase a minor to trace occurrence in terms of organic geochemistry each of the four sections of interest shows a different biomarker profile nevertheless a number of calculated parameters related to kerogen type and depositional conditions including the isoprenoids n alkanes ratios suggest a mixed terrestrial marine organic matter furthermore as indicated by the ro measurements along with rock eval parameters and the vitrinite reflectance equivalent based on aromatic compounds the maturity level is marginally mature in the cases of banik and galy derash whereas in the cases of dwawa and barsarin sections it is mature to post mature a synthesis of the organic petrography and geochemical appraisal applied in the present study suggests that the reported solid hydrocarbons in naokelekan fm particularly at its basal layers are non indigenous migrated and the precursor organic matter was deposited in a marine environment under oscillating conditions ranging from euxinic to well oxygenated accordingly the organic features of the notably bitumen rich coal bed fit the profile of a reservoir and or migration path

organic geochemistry and petroleum potential of early cretaceous garau formation in central part of lurestan zone northwest of zagros iran abstract deposition of organic rich black shales and dark gray limestones in the berriasian turonian interval has been documented in many parts of the world the early cretaceous garau formation is well exposed in lurestan zone in iran and is composed of organic rich shales and argillaceous limestones the present study focuses on organic matter characterization and source rock potential of the garau formations in central part of lurestan zone a total of 81 core samples from 12 exploratory wells were subjected to detailed geochemical analyses these samples have been investigated to determine the type and origin of the organic matter as well as their petroleum generation potential by using rock eval toc pyrolysis gc and gcms techniques the results showed that toc content ranges from 0 5 to 4 95 percent pi and tmax values are in the range of 0 2 and 0 6 and 437 and 502 c most organic matter is marine in origin with sub ordinary amounts of terrestrial input suggesting kerogen types ii iii and iii measured vitrinite reflectance rrandom values varying between 0 78 and 1 21 indicating that the garau sediments are thermally mature and represent peak to late stage of hydrocarbon generation window hydrocarbon potentiality of this formation is assessed fair to very good capable of generating chiefly gas and some oil biomarker characteristics are used to provide information about source and maturity of organic matter input and depositional environment the relevant data include normal alkane and acyclic isoprenoids distribution of the terpane and sterane aliphatic biomarkers the garau formation is characterized by low pr ph ratio

the interaction of recirculation gyres and a deep boundary current abstractmotivated by the proximity of the northern recirculation gyre and the deep western boundary current in the north atlantic an idealized model is used to investigate how recirculation gyres

petroleum generation characteristics of heterogeneous source rock from chia gara formation in the kurdistan region northern iraq as inferred by bulk and quantitative pyrolysis techniques abstract this study is the rst attempt which provides information regarding the bulk and quantitative pyrolysis results of the chia gara formation from the kurdistan region northern iraq ten representative early mature to mature samples from the chia gara formation were investigated for toc contents rock eval pyrolysis pyrolysis gc and bulk kinetic parameters these analyses were used to characterize the petroleum generated during thermal maturation of the chia gara source rock and to clarify the quantity of the organic matter and its effect on the timing of petroleum generation pyrolysis hi data identi ed two organic facies with di erent petroleum generation characteristics type ii iii kerogen with hi values of 250 mg hc g toc and type iii kerogen with hi values bulk kinetic analysis of the chia gara source rock indicates a heterogeneous organic matter assemblage typical of restricted marine environments in general the activation energy distributions reveal relatively broad and high values ranging from 40 to 64 kcal mol with pre exponential factors varying from 2 2835 e 12 sec to 4 0920 e 13 sec the predicted petroleum formation temperature of onset tr 10 temperatures ranges from 110 to 135 c and peak generation temperatures geological tmax between 137 c and 152 c the peak generation temperatures reach a transformation ratio in the range of 42 50 tr thus the chia gara source rock could have generated and expelled significant quantities of petroleum hydrocarbons in the kurdistan of iraq

wind forced variability of the remote meridional overturning circulation abstractthe mechanisms by which time dependent wind stress anomalies at midlatitudes can force variability in the meridional overturning circulation at low latitudes are explored it is shown that

changes in deep and intermediate water properties in the western north atlantic during marine isotope stages 11 12 evidence from odp leg 172 abstract the interval of time represented by marine isotope stages 11 and 12 360 470 ka contains what may be the most extreme glacial and interglacial climate conditions of the late pleistocene it has been suggested that sea level rose by 160 m at the termination of glacial stage 12 this is 30 greater than the sea level rise that followed the most recent glacial maximum there have been few detailed studies of the unique conditions that existed during the stage 11 12 time period because of the lack of high quality core material this problem has been addressed by the collection of high deposition rate cores from sediment drifts in the western north atlantic during ocean drilling project leg 172 benthic foraminiferal 13 c data from cores collected between 4600 and 1800 m were used to reconstruct bathymetric gradients in deep and intermediate water properties for selected time slices during this glacial interglacial cycle during glacial stage 12 the deep western north atlantic was filled by a water mass that was more nutrient enriched than modern antarctic bottom water above 2000 m a more nutrient depleted water mass existed during this glacial stage such an intermediate water mass has been described for more recent glacial periods and presumably forms in a more proximate region of the north atlantic interglacial stage 11 water mass properties closely resemble those of the present day western north atlantic a nutrient depleted water mass 13 c of 0 75 1 0 similar to modern north atlantic deep water existed between 3500 and 2000 m this was underlain by a water mass with lower 13 c values 13 c change of 0 95 from stage 12 to stage 11 this is twice the whole ocean 13 c change reported for the transition from the last glacial maximum to the holocene

how does the deep western boundary current cross the gulf stream abstract the manner in which the deep western boundary current dwbc crosses the gulf stream is investigated using data from a hydrographic survey conducted in 1990 absolute geostrophic velocity vectors are computed using in situ float data to obtain the reference level three density layers are considered in detail two mid depth layers which together make up the shallowest water mass component of the dwbc 500 1200 m and a deep layer consisting of the norwegian greenland overflow water 2500 3500 m the shallowest layer does not make it through the crossover and is completely entrained by the gulf stream however the resulting drop in equatorward transport is almost completely replenished by offshore entrainment just south of the crossover in the intermediate layer which is denser than the gulf stream coming off the shelf part of the dwbc recirculates to the northeast while the onshoremost portion continues equatorward in the deep layer only a small amount of recirculation occurs the lateral

comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open system pyrolysis this study compares kinetic parameters determined by open system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated but also in the derivation of the kinetic parameters i e isothermal linear regression and non isothermal nonlinear regression results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open system pyrolysis hydrous pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic sulfur content of the original kerogen conversely open system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic sulfur contents comparisons of the kinetic parameters in a hypothetical thermal burial history 2 5 c my show open system kinetic parameters significantly underestimate the extent and timing of oil generation for type iis kerogen and significantly overestimate the extent and timing of petroleum formation for type i kerogen compared to hydrous pyrolysis kinetic parameters these hypothetical differences determined by the kinetic parameters are supported by natural thermal burial histories for the naokelekan source rock type iis kerogen in the zagros basin of iraq and for the green river formation type i kerogen in the uinta basin of utah differences in extent and timing of oil generation determined by open system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions products and mechanisms

geochemical characterization of source rocks and oils from northern iraq insights from biomarker and stable carbon isotope investigations abstract the origin of oil in the cretaceous tertiary reservoirs of northern iraq remains controversial consequently a detailed geochemical study including rock eval pyrolysis gas chromatography mass spectrometry and carbon isotope analysis was conducted on 65 source rock core and cuttings samples from the najmah chia gara and balambo formations northern iraq twenty four crude oils were also analyzed to provide new insights into source organic matter depositional environment and correlations between crude oils and their probable source rocks bulk geochemical analysis of candidate source rock samples indicates that the najmah formation has more petroleum potential than the chia gara and balambo formations these three candidate source rocks were deposited in slightly different environments and have different organic matter types as determined by screening analysis and biomarker data the najmah formation contains organic rich toc up to 4 2 wt oil prone type i ii kerogen deposited under anoxic conditions the chia gara and balambo formations contain mixed type ii iii and type iii kerogens oil and gas prone deposited under less reducing conditions with more terrigenous organic matter input unfortunately most of the rock samples contain less than 2 5 wt toc which likely excludes them as source rocks but more deeply buried equivalents may contain more organic matter biomarker and stable carbon isotope compositions suggest that cretaceous and miocene reservoired oils from the northern iraq basins although predominantly derived from marine carbonate organic matter constitute five genetically distinct oil families based on age specific biomarkers the oils were probably derived from three active petroleum systems in northern iraq jurassic jurassic early cretaceous and early to mid cretaceous biomarker maturity parameters indicate that most of the oils were generated in the early oil window similar to the extracts

discovery of oil bitumen co existing with solid bitumen in the lower cambrian longwangmiao giant gas reservoir sichuan basin southwestern china implications for hydrocarbon accumulation process abstract natural gas in the recently discovered lower cambrian longwangmiao giant gas reservoir of the sichuan basin in southwestern china has been considered to be from oil cracking and sourced from the underlying lower cambrian qiongzhusi shales similar to the underlying neoproterozoic dengying giant gas reservoir however geological considerations and differences in geochemistry between the longwangmiao and dengying gases bitumens imply different scenarios organic petrology geochemistry and trace element analyses of widely occurring bitumen were conducted to evaluate this hypothesis results show the coexistence of solid bitumen and oil bitumen in this reservoir for the first time which implies a new hydrocarbon accumulation process and associated exploration strategies the two types of bitumen were termed type a solid bitumen and type b oil bitumen which were sourced from the lower cambrian qiongzhusi formation shale and the lower silurian longmaxi shale respectively the type a solid bitumen shows little fluorescence and its color under plane polarized light is almost black this indicates that the type a solid bitumen is likely of high maturity it typically occurs in dissolution pores and accounts for approximately 90 of all bitumen in the reservoir in contrast the type b oil bitumen is brown black in color under plane polarized light and yellow green under fluorescence light indicating that it is mature it occurs in the residual spaces of the solid bitumen and represents approximately 10 of the total bitumen content this suggests that type a bitumen charged the reservoir earlier than did the type b bitumen during the indosinian epoch of the triassic oil generated from the mature qiongzhusi formation migrated into the longwangmiao and dengying reservoirs following this the dengying reservoir reached the temperature threshold for oil cracking since the late cretaceous and it is suggested that oil could have started to crack to gas which is the critical moment for the gas formation however the longwangmiao oils had not been cracked at this stage because the reservoir temperature had not reached the threshold later during the himalayan epoch the gas in the dengying reservoir as well as some kerogen cracking gas from the qiongzhusi shales migrated into the longwangmiao reservoir along faults gas gravity drainage and phase separation took place in the longwangmiao reservoir forming the type a solid bitumen and giant gas accumulation later oil generated from the longmaxi shales migrated into the longwangmiao reservoir forming the type b oil bitumen the case here is an example of a multi stage oil and gas accumulation future exploration targets should include middle upper cambrian reservoir rocks

fracture patterns in the zagros fold and thrust belt kurdistan region of iraq abstract fracture data have been collected in the kurdistan region of iraq which is a poorly accessible and unexplored area of the zagros pre to early folding ne sw striking extensional fractures and nw se striking contractive elements represent the older set affecting the exposed multilayer of the area these latter structures are early syn folding and followed by folding related mesostructural assemblages which include elements striking parallel to the axial trend of major folds longitudinal fractures bedding perpendicular joints and veins and extensional faults belonging to this second fracture set are located in the outer arc of exposed anticlines whilst longitudinal reverse faults locate in the inner arcs consistently these elements are associated with syn folding tangential longitudinal strain the younger two sets are related to e w extension and nne ssw to n s shortening frequently displaying reactivation of the older sets the last shortening event which is described along the entire zagros belt probably relates with the onset of n s compression induced by the northward movement of the arabian plate relative to the eurasian plate in comparison between the inferred palaeostrain directions and the kinematics of recent gps measurements we conclude that the n s compression and the partitioning into nw se trending folds and nw to n trending strike slip faults likely remained unchanged throughout the neogene tectonic history of the investigated area

origin of crude oils from oilfields in the zagros fold belt southern iraq relation to organic matter input and paleoenvironmental conditions crude oil samples from cretaceous and tertiary reservoir sections in the zagros fold belt oil fields southern iraq were investigated using non biomarker and biomarker parameters the results of this study have been used to assess source of organic matter and the genetic link between oils and their potential source rocks in the basin the oils are characterized by high sulphur and trace metal ni v contents and relatively low api gravity values 17 4 22 7 api this indicates that these oils are heavy and generated from a marine source rock containing type ii s kerogen this is supported by their biomarker distributions of normal alkanes regular isoprenoids terpanes and steranes and the bulk carbon isotope compositions of their saturated and aromatic hydrocarbons the oils are characterized by low pr ph ratios 1 high values of the c35 homohopane index and c31 22r c30 hopane ratios relatively high c27 sterane concentrations and the predominance of c29 norhopane these biomarkers suggest that the oils were generated predominantly from a marine carbonate source rock deposited under reducing conditions and containing plankton algal and microorganisms source input the presence of gammacerane also suggests water column stratification during source rock deposition the biomarker characteristics of the oils are consistent with those of the middle jurassic sargelu carbonate as the effective source rock in the basin biomarker maturity data indicate that the oils were generated from early maturity source rocks

middle and upper jurassic hydrocarbon potential of the zagross fold belt north iraq abstract structured organic matters of the palynomorphs of mainly dinoflagellate cysts are used in this study for dating the limestone black shale and marl of the middle jurassic bajocian bathonian sargelu formation upper jurassic upper callovian lower oxfordian naokelekan formation upper jurassic kimeridgian and oxfordian gotnia and barsarine formations and upper jurassic lower cretaceous tithonian beriassian chia gara source rock formations while spore species of cyathidites australis and glechenidites senonicus are used for maturation assessments of this succession materials used for this palynological study are 320 core and cutting samples of twelve oil wells and three outcrops in north iraq terpane and sterane biomarker distributions as well as stable isotope values were determined for oils potential source rock extracts of jurassic lower cretaceous strata to determine valid oil to source rock correlations in north iraq two subfamily carbonate oil types one of middle jurassic age sargelu carbonate rock and the other of mixed upper jurassic cretaceous age chia gara with sargelu sources as well as a different oil family related to triassic marls were identified based on multivariate statistical analysis hca pca middle jurassic subfamily a oils from demir dagh oil field correlate well with rich marginally mature sargelu source rocks in well mk 2 near the city of baiji in contrast subfamily b oils have a greater proportion of c 28 c 29 steranes indicating they were generated from upper jurassic lower cretaceous carbonates such as those at gillabat oil field north of mansuriyah lake oils from gillabat field thus indicate a lower degree of correlation with the sargelu source rocks than do oils from demir dagh field palynofacies assessments are performed for this studied succession by ternary kerogen plots of the phytoclast amorphous organic matters and palynomorphs from the diagram of these plots and maturation analysis it could be assessed that the formations of chia gara and sargelu are both deposited in distal suboxic to anoxic basin and can be correlated with kerogens classified microscopically as type a and type b and chemically as type ii the organic matter comprised principally of brazinophyte algae dinoflagellate cysts spores pollen foraminifera test linings and phytoclasts in all these formations and hence affected with upwelling current these deposit contain up to 18 wt total organic matters that are capable to generate hydrocarbons within mature stage of thermal alteration index tai range in stalplin s scale staplin 1969 of 2 7 3 0 for the chia gara formation and 2 9 3 1 for the sargelu formation case study examples of these oil prone strata are one 7 m 23 ft thick section of the sargelu formation averages 44 2 mg hc g s2 and 439 c t max rock eval pyrolysis analyses and 16 wt toc especially in well mk 2 whereas one 8 m 26 ft thick section of the chia gara and 1 m 3 ft section of naokelekan formations average 44 5 mg hc g s2 and 440 c t max and 14 wt toc especially in well aj 8 one dimension petroleum system models of key wells using ies petromod software can confirm their oil generation capability these hydrocarbon type accumulation sites are illustrated in structural cross sections and maps in north iraq

biomarker signatures from neoproterozoic early cambrian oil western india abstract the neoproterozoic early cambrian time is the cradle of multicellular eukaryotic life and thereafter metazoan life started populating the planet biomarkers which record the chronicles of biotic events on earth have been investigated using gas chromatography mass spectrometry from a suite of nine oil samples extracted from oil stained sediments and a crude oil of neoproterozoic early cambrian age from bikaner nagaur basin western india the biomarker distribution is characterized by high concentration of both tricyclic terpanes and pentacyclic hopanes the predominance of c 29 regular sterane over c 27 and c 28 steranes indicates green algal contribution and may imply the prominence and diversification of the same algal group the low pristane phytane ratio and occurrence of substantial quantity of gammacerane monomethyl 2 methyl 2 2 4 8 trimethyltridecyl chroman and 1 1 7 8 tetramethyl 1 2 3 4 tetrahydrophenanthrene are indicative of stratified water column as well as anoxic and enhanced salinity condition of the environment of deposition this paper reports for the first time the presence of methyltrimethyltridecyl chromans mttcs from neoproterozoic early cambrian time putative c 19 norsteranes probably indicative of sponge input are recorded in the studied samples and also reported from other infracambrian oils and sediments normal alkanes n c 17 and n c 18 and isoprenoids pristane and phytane are highly depleted in 13 c the overall biomarker distribution and carbon isotope data of oils from bikaner nagaur basin show similarities with those of other infracambrian oils like huqf oils from oman and baykit high oils from eastern siberia

the distribution and relationship between palynomorphs in aerosols and deep sea sediments off the coast of northwest africa abstract palynomorphs in eolian dust and bottom sediments from the northeastern atlantic off the coast of northwest africa were studied primary examination was for terrestrial plant detritus pollen spores opal phytoliths and freshwater diatoms but observations about marine entities were also made three distinct geographic palynofloras were detected a northern palynoflora consisting of pollen derived primarily from the mediterranean basin a central or saharan palynoflora characterized by pollen derived from desert plants and a southern tropical equatorial palynoflora composed of pollen derived from tropical plants but including up to 50 allochthonous pollen from the drier interior of west africa palynomorph distributions are related closely to both source vegetation and to atmospheric and oceanic transport mechanisms and in many cases distribution patterns in bottom sediments and aerosols are complementary the quantity of pollen and spores per gram of bottom sediment ranges from greater than 2000 off the saharan coast in mauritania to less than 50 in deep ocean basins pollen and spores in mediterranean aerosols may exceed 40 per cubic meter of air during the summer and range between 4 to 6 for tropical aerosols during the winter tropical aerosols and bottom sediments contained the greatest abundance of fungal spores the distribution of opal phytoliths and freshwater diatoms in both aerosols and bottom sediments indicates that dust storms are a major transporting agent for these entities from the interior of west africa to the gulf of guinea these storms are also an important agent for the transport of pollen to the tropical atmosphere distances of transport may exceed 5000 km for mediterranean pollen and even greater distances for palynomorphs in eolian dust from interior west africa the abundance of dinoflagellates and microforaminifera in bottom sediments is directly related to the area of upwelling off the west african coast

charging of elk hills reservoirs as determined by oil geochemistry crude oils from miocene and pliocene reservoirs from the elk hills field in california s san joaquin basin were analyzed for stable carbon isotopes and biomarkers cluster analysis of geochemical variables defines five principal oil families all derived from different organic rich facies of the miocene monterey formation carbon isotope analysis indicates no contribution from the basin s other major source rock the eocene kreyenhagen formation oil families show a strong correspondence to stratigraphic intervals oils from pre monterey reservoirs were probably generated from the lowermost organic rich facies of the monterey and are the most thermally mature upper miocene stevens zone turbidite reservoirs contain oils of various thermal maturity stages but mature light ends are abundant and are likely generated from the floors of the adjacent subbasins located north and south of elk hills the relatively minor presence of low thermal maturity biomarkers that are typically characteristic of monterey oils may indicate that stevens traps did not form until after the source intervals were at a higher level of thermal maturity all oils in stevens porcelanite reservoirs contain a higher concentration of low maturity biomarkers which may indicate derivation from more localized areas on the flanks of the elk hills anticlines the shallow pliocene oils have suffered biodegradation to different degrees and the lowest api gravities occur on the flanks of the anticline the carbon isotopic composition of these oils suggests yet another monterey source facies that charged the pliocene reservoirs and is not simply the result of vertical leakage from the older miocene reservoirs john e zumberge has been vice president and cofounder of geomark research in houston since 1991 he was manager of geochemical and geological research for cities service occidental general manager for ruska laboratories and director of geochemical services for core laboratories he has global experience in petroleum geochemistry focusing on crude oil biomarkers he obtained a b s degree in chemistry from the university of michigan and a ph d in organic geochemistry from the university of arizona judy a russell is a senior geological advisor for occidental and works on worldwide exploration and production with an emphasis on the integration of geochemistry she has extensive experience in many of occidental s projects in latin america far east the united states and the middle east she has a b s degree from phillips university and an m s degree from the new mexico institute of mining and technology stephen anthony reid is a senior geological advisor for occidental and works on international exploration with an emphasis on deep water projects he has extensive experience in california s san joaquin basin including the elk hills field where he conducted studies on stevens turbidite and monterey porcelanite reservoirs he has b s and m s degrees from california state university northridge

eddies of newly formed upper labrador sea water a new type of submesoscale eddy has been observed south of the labrador sea during late winter embedded in equatorward flow along the western boundary the eddy radius is 20 km with a weak dynamic signature swirl speed of 0 5 cm s the center of the eddy is characterized by weak stratification elevated concentrations of oxygen and anthropogenic tracers and low tracer ages all indicative of newly ventilated water strong lateral intrusions distort the shape of the feature the water mass contained in the eddy is not classical labrador sea water from the central labrador sea but is significantly fresher and hence lighter it is of the correct density to be the source of the high chlorofluorocarbon layer of the shallow deep western boundary current observed further south and hence is termed upper labrador sea water using a combination of hydrographic data sets along the western boundary to implement a simple lateral diffusion model it is shown that such eddies decay of the order of several months and are difficult to observe equatorward of the grand banks of newfoundland this is in contrast to deeper lenses of classical labrador sea water which persist further equatorward tracer derived ages of the upper labrador sea water eddy range from 3 to 5 years much older than the lifetime deduced from their lateral diffusion a simple convection model of tracer age shows that this age discrepancy is caused by gas exchange being unable to maintain equilibrium between the deep convecting mixed layer and the atmosphere during formation

the influence of eddies on tracer transport in the abyssal ocean abstract tracer transport mechanisms in a deep western boundary current dwbc are explored using a three layer eddy resolving quasigeostrophic model the model is forced with a steady sinusoidal wind stress the effects of the wind stress coupled with instabilities create an unsteady zonal surface jet at the boundary between the model subtropical and subpolar gyres the bottom layer includes a dwbc created by specifying a mass inflow at the northern boundary and a mass outflow at the southern boundary a numerical tracer is introduced into the dwbc with the mass source at the northern boundary the surface jet creates an effective boundary to tracer transport in the dwbc this barrier to meridional tracer transport causes approximately 70 of the tracer moved out of the northern part of the dwbc to be transported zonally into the interior with only 30 continuing southward in the dwbc in model runs with a flat bottom approximately 20 of the total meridional tracer flux is due to the eddy field w

solid bitumen bituminite and thermal maturity of the upper jurassic lower cretaceous chia gara formation kirkuk oil field zagros fold belt kurdistan iraq abstract the upper jurassic lower cretaceous chia gara formation a proven marine source rock characterised by predominance of amorphous organic matter aom is known from few outcrops in ne iraq and a number of exploration wells in the zagros fold belt this study presents comprehensive organic petrographic and mineralogical investigations of the dispersed organic matter and rock forming minerals of the tithonian berriasian chia gara formation intersected by the kirkuk well k 109 drilled in the giant kirkuk oil field ne iraq the organic petrographic analyses including incident light microscopy and confocal laser scanning microscopy clsm were applied to carbonate source rocks with low to moderate organic carbon contents our data demonstrate the predominance of bituminite and solid bitumen among the examined dispersed organic matter followed by oil exudates and oil globule inclusions as well as the presence of minor contributions of alginite i e tasmanites and leiospheridia liptodetrinite and vitrinite based on optical characteristics and clsm spectral fluorescence measurements examinations of bituminite point towards the presence of bituminite type iii the bituminite type iii encloses dark orange fluorescent amorphous components suggesting a genetic relationship either with liptodetrinite and or with solid bitumen the qualitative assessment of solid bitumen reveals several dissimilar forms identified in the analysed samples the photometric and spectral fluorescence measurements point to distinct reflectance values ranging between 0 19 and 0 43 sbrr and lambda max values extending from 515 nm to 590 nm respectively the corresponding results of the solid bitumen exhibit 1 a lack of a relationship with depth and 2 suggest its poor property as a reliable maturity indicator for the examined samples the presence of oil exudates oil globule inclusions and their association with solid bitumen suggests a genetic relation with the examined residues of liquid hydrocarbon phase the performed thermal maturities assessments of dispersed organic matter point towards early mature to peak mature oil window with vitrinite reflectance values ranging between 0 52 vrr at 2801 m to 0 83 vrr at 3089 m depth mineralogical analyses revealed the predominance of calcite over dolomite in the examined limestone to marl lithofacies e g clear rimmed dolomite with localised intensive dolomitisation in the phyllosilicate rich matrix predominance of calcite and siderite is observed followed by zinc blende and pyrite the composition of organic matter in the examined chia gara formation with predominance of bituminite and solid bitumen makes the major marine source rock of iraq s cretaceous petroleum systems distinctive in terms of hydrocarbon generation and migration at an oil window stage as it provides suitable explanations for its generally low hydrogen index hi with only minor terrestrial input in addition the results presented herein can be helpful for future evaluation of thermal maturities and characterisation of optical appearances of dispersed organic matter in carbonates by incident light microscopy and especially by clsm during hydrocarbon prospecting

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

lagrangian observations of the deep western boundary current in the north atlantic ocean abstract in this study the authors analyze the trajectories of 18 rafos floats launched in the deep western boundary current dwbc between the grand banks and cape hatteras to investigate the kinematics and dynamics in the region where the dwbc crosses under the gulf stream near 36 n the crossover region floats deployed in the chlorofluorocarbon cfc maximum associated with upper labrador sea water depth 800 m illustrate the entrainment process of this water mass into the gulf stream the behavior of the floats and fluid parcels in the crossover region is strongly dependent on the meandering of the gulf stream when the stream is close to its mean position fluid parcels entrained from the upper dwbc travel along the northern edge of the stream when a meander trough is present downstream of the entrainment location dwbc fluid parcels cross the gulf stream and sometimes are expelled on the south side this represents a previously unrecognized mechanism for transporting upper labrador sea w

geochemical characterisation of tithonian berriasian chia gara organic rich rocks in northern iraq with an emphasis on organic matter enrichment and the relationship to the bioproductivity and anoxia conditions abstract tithonian berriasian chia gara organic rich rocks located in kurdistan northern iraq were analysed based on inorganic and organic geochemistry to define the origin type of organic matter and the influencing factors of organic matter om enrichment including the om input and preservation and their relationship to the paleoenvironment conditions the 13 c org values of the chia gara rocks range from 29 99 to 26 93 with average values of approximately 28 8 indicating that the organic matter has a predominantly marine origin enhanced biological productivity within the photic zone of the water column during deposition of the chia gara fm is indicated by consistently high organic carbon content in most samples average 3 wt as well as by bulk geochemical and biomarker characteristics major contributions by aquatic algae and microorganisms with a minor terrigenous organic matter contribution are indicated by the n alkane distribution patterns and the composition of the hopanoids steroids and tricyclic terpenoids strongly reducing bottom water is indicated by low pristane phytane ratios homohopane distribution patterns and the redox sensitive trace elements geochemistry salinity stratification with alkaline bottom waters is indicated by high sr ba ratios and the presence of gammacerane in the analysed chia gara samples these data indicate that om enrichment in the tithonian berriasian chia gara rocks results from the combination of enhanced biological productivity and salinity stratification with anoxic bottom water conditions which favoured om preservation