首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 109 毫秒
1.
The origin of the fourteen major oil fields in the Bozhong sub-basin, Bohai Bay basin was studied based on the results of Rock-Eval pyrolysis on more than 700 samples and biomarker analysis on 61 source rock samples and 87 oil samples. The three possible source rock intervals have different biomarker assemblages and were deposited in different environments. The third member of the Oligocene Dongying Formation (E3d3, 32.8–30.3 Ma in age) is characterized mainly by high C19/C23 tricyclic terpane (>0.75), high C24 tetracyclic terpane/C26 tricyclic terpane (>2.5), low gammacerane/αβ C30 hopane (<0.15) and low 4-methyl steranes/ΣC29 steranes (<0.15) ratios, and was deposited in sub-oxic to anoxic environments with significant terrigenous organic matter input. The first (E2s1, 35.8–32.8 Ma) and third (E2s3, 43.0–38.0 Ma) members of the Eocene Shahejie Formation have low C19/C23 tricyclic terpane and low C24 tetracyclic terpane/C26 tricyclic terpane ratios and were deposited in anoxic environments with minor terrestrial organic matter input, but have different abundances of 4-methyl steranes and gammacerane. The hydrocarbon-generating potential and biomarker associations of these three source rock intervals were controlled by tectonic evolution of the sub-basin and climate changes. Three oil families derived from E2s3, E2s1 and E3d, respectively, and three types of mixed oils have been identified. All large oil fields in the Bozhong sub-basin display considerable heterogeneities in biomarker compositions and originated from more than one source rock interval, which suggests that mixing of oils derived from multiple source rock intervals or multiple generative kitchens, and/or focusing of oils originated from a large area of a generative kitchen, is essential for the formation of large oil fields in the Bozhong sub-basin. E2s3- and E2s1-derived oils experienced relatively long-distance lateral migration and accumulated in traps away from the generative kitchen. E3d3-derived oils had migrated short distances and accumulated in traps closer to the generative kitchen. Such a petroleum distribution pattern has important implications for future exploration. There is considerable exploration potential for Dongying-derived oils in the Bozhong sub-basin, and traps close to or within the generative kitchens have better chance to contain oils generated from the Dongying Formation.  相似文献   

2.
Sixty crude oils from the Termit Basin (Eastern Niger) were analysed using biomarker distributions and bulk stable carbon isotopic compositions. Comprehensive oil-to-oil correlation indicates that there are two distinct families in the Termit Basin. The majority of the oils are geochemically similar and characterized by low Pr/Ph (pristane to phytane ratios) and high gammacerane/C30 hopane ratios, small amounts of C24 tetracyclic terpanes but abundant C23 tricyclic terpane, and lower δ13C values for saturated and aromatic hydrocarbon fractions. All of these geochemical characteristics indicate possible marine sources with saline and reducing depositional environments. In contrast, oils from well DD-1 have different geochemical features. They are characterized by relatively higher Pr/Ph and lower gammacerane/C30 hopane ratios, higher amounts of C24 tetracyclic terpane but a low content of C23 tricyclic terpane, and relatively higher δ13C values for saturated and aromatic hydrocarbon fractions. These geochemical signatures indicate possible lacustrine sources deposited under freshwater, suboxic-oxic conditions. This oil family also has a unique biomarker signature in that there are large amounts of C30 4α-methylsteranes indicating a freshwater lacustrine depositional environment.The maturity of the Termit oils is assessed using a number of maturity indicators based on biomarkers, alkyl naphthalenes, alkyl phenanthrenes and alkyl dibenzothiophenes. All parameters indicate that all of the oils are generated by source rocks within the main phase of the oil generation stage with equivalent vitrinite reflectance of 0.58%–0.87%.  相似文献   

3.
Shixi Bulge of the central Junggar Basin in western China is a unique region that provides insight into the geological and geochemical characteristics of large-scale petroleum reservoirs in volcanic rocks of the western Central Asian Orogenic Belt. Carboniferous volcanic rocks in the Shixi Bulge mainly consist of striped lava and agglomerate, as well as breccia lava and tight tuff. Volcanic rocks differ in porosity and permeability. Striped lava exhibits the highest porosity (average: 14.2%) but the lowest permeability (average: 0.67 × 10−15 m) among the rock types. Primary gas pores are widely developed and mostly filled. Secondary dissolution pores and fractures are two major reservoir storage spaces. Capillary pressure curves suggest the existence of four pore structure types of reservoir rocks. Several factors, namely, lithology, pore structure, and various diagenesis, govern the physical properties of volcanic rocks. The oil is characterized by a high concentration of tricyclic terpane, a terpane distribution of C23 < C21 > C20, and sterane distributions of C27 < C28 < C29 and C27 > C28 < C29. Oil and gas geochemistry revealed that the oil is a mixture derived primarily from P2w source rock and secondarily from P1j source rock in the sag west of Pen-1 Well. The gases are likely gas mixtures of humic and sapropelic organic origins, with the sapropelic gas type dominant in the mixture. The gas mixture is most likely cracked from kerogen rather than oils. The Carboniferous volcanic reservoirs in Shixi Bulge share some unique characteristics that may provide useful insights into the various roles of different volcanic reservoir types in old volcanic provinces. The presence of these reservoirs will undoubtedly encourage future petroleum exploration in volcanic rocks up to the deep parts of sedimentary basins.  相似文献   

4.
Oil samples from Lower Cretaceous to Eocene reservoirs in southwest Iran were analyzed using gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry for genetic classification of oil families and determining their maturity. The Studied oil samples are non-biodegraded and their gravity range from 18.3 to 37° API. The slight even/odd n-alkane predominance, coupled with low Pr/Ph values, suggests their likely source rocks with a predominance of algal organic matter, type IIS kerogen deposited under strongly reducing marine environments. The biomarker distribution of investigated oils is characterized by high concentration of both C29 and C30 hopanes and ratios of C29/C30H are generally greater than unity. There is a marked predominance of C29 regular sterane over C27 and C28 homologs in our studied oils. High sterane/hopane values and cross plot of the δ13C sat versus δ13C aro show contribution of marine organic matter. Medium value of gammacerane index and other salinity indices show water density stratification and high salinity conditions of the environment of deposition. It can be concluded that the studied reservoirs, due to their variable maturity have different API gravity and contain two oil families (types A and B) with latter being deeper and comprising more mature oils.  相似文献   

5.
Interest in factors controlling lacustrine source rock deposition has increased over the last few decades because this type of deposits contain significant petroleum resources. Generally, tectonic subsidence and climate are the two root causes as they control the accommodation potential, water column properties and sources of organic matter. In this study, coupling organic geochemical and elemental geochemical data, two potential source rocks, i.e., the Eocene Wenchang Formation (E2w) and Oligocene Enping Formation (E3e) were investigated. Two models were finally raised to explain deposition of the two set of source rocks according to their paleoclimatic and tectonic properties. The source rock potential shows a strong heterogeneity. The second member of the Eocene Wenchang Formation (E2w2) is characterized by high organic matter content and oil-prone kerogen type. In contrast, the first member of the Eocene Wenchang Formation (E2w1) and the Oligocene Enping formation (E3e) are characterized by low organic matter content and gas-prone kerogen type. The primary productivity and depositional environment exhibit notable differences between the two potential source rocks horizons and show an obvious variation from the depocenter to the slope and can be best explained by the coevolution of tectonic subsidence and climate. During the E2w depositional stage, low sediment supply led to mudstone deposited in deep lacustrine environment and resulted in underfilled lake basin. The low water inflow provided little terrigenous organic matter (low bicadinane, perylene and floranthene contents) and oxygen. Besides, the low area/depth ratio impeded the water circulation, thus resulted in shallow thermocline and anoxic-suboxic bottom environment (abundant dibenzothiophene and high C35/C3122S hopane ratios). Therefore abundant algae, which contributed to the high amorphous organic matter (AOM) content, can be preserved. The warm and wet climate (high Mn/Mg ratios) gave birth to autochthonous organism, such as dinoflagellates and Pavlova gyrans (abundant 4-methyl sterane). During the E3e depositional stage, the sufficient sedimentary supply resulted in expanding, shallow lacustrine and swamp environment. The higher area/depth ratio and high sediment supply made environment unstable and can be strongly influenced by external environment (broader range of Mn/Mg ratios). Enough terrigenous organic matter (TOM) was transported to the slope but little to the depocenter. The slightly hot and dry climate (low Mn/Mg ratios) led to decreasing autochthonous organism and evaporation environment. The shallow water depth and relative dry climate resulted in saline, suboxic-dysoxic acid bottom environment. The co-variation of organic and inorganic indexes indicates the combination is a valid method in reconstructing source rock depositional models.  相似文献   

6.
Three bitumen fractions were obtained and systematically analysed for the terpane and sterane composition from 30 Paleozoic source rocks and 64 bitumen-containing reservoir rocks within the Upper Sinian, Lower Cambrian, Lower Silurian, Middle Carboniferous, Upper Permian and Lower Triassic strata in the Sichuan Basin and neighbouring areas, China. These bitumen fractions include extractable oils (bitumen I), oil-bearing fluid inclusions and/or closely associated components with the kerogen or pyrobitumen/mineral matrix, released during kerogen or pyrobitumen isolation and demineralization (bitumen II), and bound compounds within the kerogen or pyrobitumen released by confined pyrolysis (bitumen III). In addition, atomic H/C and O/C ratios and carbon isotopic compositions of kerogen and pyrobitumen from some of the samples were measured. Geochemical results and geological information suggest that: (1) in the Central Sichuan Basin, hydrocarbon gases in reservoirs within the fourth section of the Upper Sinian Dengying Formation were derived from both the Lower Cambrian and Upper Sinian source rocks; and (2) in the Eastern Sichuan Basin, hydrocarbon gases in Middle Carboniferous Huanglong Formation reservoirs were mainly derived from Lower Silurian source rocks, while those in Upper Permian and Lower Triassic reservoirs were mainly derived from both Upper Permian and Lower Silurian marine source rocks. For both the source and reservoir rocks, bitumen III fractions generally show relatively lower maturity near the peak oil generation stage, while the other two bitumen fractions show very high maturities based on terpane and sterane distributions. Tricyclic terpanes evolved from the distribution pattern C20 < C21 < C23, through C20 < C21 > C23, finally to C20 > C21 > C23 during severe thermal stress. The concentration of C30 diahopane in bitumen III (the bound components released from confined pyrolysis) is substantially lower than in the other two bitumen fractions for four terrigenous Upper Permian source rocks, demonstrating that this compound originated from free hopanoid precursors, rather than hopanoids bound to the kerogen.  相似文献   

7.
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.  相似文献   

8.
The Cuu Long Basin (Mekong Basin) is a rift basin off southern Vietnam, and the most important petroleum producing basin in the country. However, information on petroleum type and characteristics has hitherto been largely unavailable to the public. This paper presents petroleum geochemical data on nine oil samples from four different producing fields in the Cuu Long Basin: the Dragon (Rong), Black Lion (Sutu-Den), Sunrise (Rang ?ong) and White Tiger (Bach Ho) Fields. The oils are highly paraffinic with bimodal normal alkane distributions and show moderate pristane to phytane ratios and a conspicuous hyperbolic decrease in abundance with increasing carbon number of hopane homologues from C30 to C35. The TPP-index of Holba et al. (Holba, A.G., Dzou, L.I., Wood, G.D., Ellis, L., Adam, P., Schaeffer, P., Albrecht, P., Greene, T., Hughes, W.B., 2003. Application of tetracyclic polyprenoids as indicators of input from fresh–brackish water environments. Organic Geochemistry 34, 441–469) is equal to 1 in all samples which in combination with tricyclic triperpane T26/T25 ratios >1 and the n-alkane and hopane distributions mentioned above provide a strong indication of an origin from lacustrine source rocks. This is supported by the absence of marine C30 desmethyl steranes (i.e. 24-n-propylcholestanes) and marine diatom-derived norcholestanes. Based on the overall biological marker distributions, the lakes probably belonged to the overfilled or balanced-fill types defined by Bohacs et al. (Bohacs, K.M., Carroll, A.R., Neal, J.E., Mankiewicz, P.J., 2000. Lake-basin type, source potential, and hydrocarbon character. An integrated sequence-stratigraphic–geochemical framework. AAPG Studies in Geology 46, 3–34). The oils were generated from source rocks at early- to mid-oil-window maturity, presumably Oligocene lacustrine shales that are present in the syn-rift succession. Oils from individual fields may, however, be distinguished by a combination of biological marker parameters, such as the oleanane index, the gammacerane index, the relative abundance of tricyclic terpanes, the proportions of diasteranes and 28-norspergulane, complemented by other parameters. The oils of the Cuu Long Basin show an overall similarity to the B-10 oil from the Song Hong Basin off northern Vietnam, but are markedly different from the seepage oils known from Dam Thi Nai on the coast of central Vietnam.  相似文献   

9.
This study aims at investigating hydrocarbon generation potential and biological organic source for the Tertiary coal-bearing source rocks of Pinghu Formation (middle-upper Eocene) in Xihu depression, East China Sea shelf basin. Another goal is to differentiate coal and mudstone with respect to their geochemical properties. The coal-bearing sequence has a variable organofacies and is mainly gas-prone. The coals and carbonaceous mudstones, in comparison with mudstones, have a higher liquid hydrocarbon generation potential, as reflected by evidently higher HI values (averaging 286 mg HC/g C) and H/C atomic ratios (round 0.9). The molecular composition in the coal-bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes, dominant C29 sterane over C27 and C28 homologues and high amount of terrigenous-related aromatic biomarkers such as retene, cadalene and 1, 7-dimethylphenanthrene, indicating a predominantly terrigenous organic source. The source rocks show high Pr/Ph ratios ranging mostly from 3.5 to 8.5 and low MDBTs/MDBFs ratios (<1.0), indicating deposition in an oxic swamp-lacustrine environment. The coals and carbonaceous mudstones could be differentiated from the grey mudstones by facies-dependent biomarker parameters such as relative sterane concentration and gammacerane index and carbon isotope composition. Isotope and biomarker analysis indicate the genetic correlation between the Pinghu source rocks and the oils found in Xihu depression. Moreover, most oils seem to be derived from the coal as well as carbonaceous mudstone.  相似文献   

10.
The Shijiutuo uplift is an oil enriched uplift in the offshore Bohai Bay Basin. Petroleum migration is a key factor for oil enrichment in Neogene reservoirs far away from the hydrocarbon kitchen. In this article, an integration of geological, geophysical and geochemical analyses are employed to investigate the petroleum migration and accumulation on the Shijiutuo uplift. Hydrocarbons in the QHD32-6 and QHD33 oilfields are mainly originated from the third (E2s3) and first (E2s1) member of the Shahejie Formation. The shallow traps have significant contributions of late-stage E2s1-derived oil. Lateral petroleum migration is a major mechanism forming large oilfields on the Shijiutuo uplift. The large oilfields have multiple hydrocarbon kitchens, multiple source rocks, and numerous preferential petroleum migration pathways (PPMPs). Once petroleum arrives at the structural highs on the Shijiutuo uplift through the Guantao Formation (N1g) carrier-beds, neotectonic faults cutting through Guantao (N1g) and Minghuazhen (N1mL) formations could serve as effective conduits for vertical petroleum migration. Neotectonic faults have experienced polycyclic fault activities. Fluid inclusions indicate episodic hydrocarbon charging. Crude oils display duplex properties of biodegradation and non-biodegradation, which is strong evidence for multiple and episodic oil charging on the Shijiutuo uplift. Finally, episodic petroleum charging along polycyclic neotectonic faults causes the late-stage E2s1-derived oils to occur in the shallow reservoirs.  相似文献   

11.
Shales of the Silurian Dadaş Formation exposed in the southeast Anatolia were investigated by organic geochemical methods. The TOC contents range from 0.24 to 1.48 wt% for the Hazro samples and 0.19 to 3.58 wt% for the Korudağ samples. Tmax values between 438 and 440 °C in the Hazro samples indicate thermal maturity; Tmax values ranging from 456 to 541 °C in the Korudağ samples indicate late to over-maturity. Based on the calculated vitrinite reflectance and measured vitrinite equivalent reflectance values, the Korudağ samples have a maximum of 1.91%R(g-v), in the gas generation window, while a maximum value of 0.79%R(amor-v) of one sample from the Hazro section is in the oil generation window. Illite crystallinity (IC) values of all samples are consistent with maturity results.Pr/Ph ratios ranging from 1.32 to 2.28 and C29/C30 hopane ratios > 1.0 indicate an anoxic to sub-oxic marine-carbonate depositional environment.The Hazro shales do not have any shale oil or shale gas potential because of their low oil saturation index values and early to moderate thermal maturation. At first glance, the Korudağ shales can be considered a shale gas formation because of their organic richness, thickness and thermal over-maturity. However, the low silica content and brittle index values of these shales are preventing their suitability as shale gas resource systems.  相似文献   

12.
Geochemical as well as multivariate statistical analyses (PCA) were carried out on 20 crude oil samples from ‘Middle’ Pliocene Production Series (MPPS) of Guneshli-Chirag-Azeri (GCA), Bahar, and Gum Adasi fields in the western South Caspian Basin (SCB). PCA analysis employed to source-specific biomarkers distinguishes the oils into two types one being divided into two sub-types; Type 1 (GCA oils), Type 2A (Bahar field oils) and Type 2B (Gum Adasi field oils). Indirect oil-to-source rock correlations to available source rock data from previous studies suggest that Type 1 oils, located in the Apsheron-Balkhans uplift area, are derived from basinal shales of the Oligocene-Lower Miocene Middle Maikop Formation. Type 2A and 2B oils, located in the Gum-deniz-Bahar-Shakh-deniz trend area, are more likely derived from shelf-edge shales of the Upper Maikop Formation and the Middle-Upper Miocene Diatom Suite, respectively.Biomarker maturity study reveals that Type 1 oils (mean %Rc=0.78) are more mature than Type 2 oils (mean %Rc=0.71). Source rocks, which generated these oils, were at generation depth interval between 5200 m (112 °C) and 7500 m (153 °C) at the time of expulsion. This indicates that the western SCB oils experienced significant long-range vertical migration along the deep-seated faults to accumulate in the MPPS reservoirs. Post-accumulation biodegradation process was only observed in the Guneshli field where bacterial alteration (level 4) began between 4.2 and 2.6 mybp and stopped with the deposition of the overlying impermeable Upper Pliocene Akchagyl Formation. Subsequent light hydrocarbon (C1–C16) charge into the Guneshli fields caused precipitation of asphaltenes, which is evidenced by high resin to asphaltene ratios for the present-day Guneshli oils. Evaporative-fractionation examined using the scheme of [Thompson, 1987] showed high correlations of the ‘aromaticity’ B parameter (=toluene/n-C7) and ‘parafinicity’ F parameter (=n-C7/MCH with the %Rc (maturity) and C27/C29 sterane ratio (organic matter type). This implies that Thompson's approach should be used with caution in the SCB. Among the several mechanisms, rapid and thick deposition of Pliocene sediments and subsequent high heating rate on the Maikop Formation and Diatom Suite is probably the most plausible way of explaining the origin of light hydrocarbons in the Guneshli and Bahar fields.  相似文献   

13.
The petroleum charge history of the Barrandian basin was investigated by analysing quartz and calcite and organic phases that occur in veins and fractures cutting dolerite sills within the Liteň Formation (Silurian). The geochemical characteristics of fluid inclusions trapped in vein quartz and calcite, vein bitumens and adjacent potential source rocks when combined with burial and thermal history data reflect the presence of at least three separate hydrocarbon charge episodes. Solid highly reflecting (Rmax = 0.92–1.49%) bitumen provides information on the first and oldest episode of oil migration. The precursor oil was probably derived relatively early during diagenesis from nearby organic-rich sediments and was subsequently thermally altered to form the solid bitumen.  相似文献   

14.
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.  相似文献   

15.
Fluctuations in lacustrine sedimentary environments significantly affect distributions of organic matter (OM), uranium, and other elements in shales. In this study a high-resolution geochemical record of fluctuations in the paleo-depositional environment of a terrestrial lake basin is provided on the basis of extensive samples collected from the Member 3 of the Paleogene Shahejie Formation (Es3) of the Niu-38 well in the Dongying Depression, Eastern China. These samples were tested for total organic carbon (TOC), element concentrations, and biomarkers to study the evolution and fluctuation in the depositional environments of an ancient lake basin and associated geochemical response. The evolution and fluctuation of the sedimentary environment from a deep lake to a semi-deep lake and then to a shallow lake delta were indicated by geochemical response. During this evolution, the values of TOC, S1, S2, Sr, and Ts/(Ts + Tm) remarkably decreased, whereas those of Co, Ni, Rb, Na, Fe/Mn, Fe/(Ca + Mg), and C29 mortane/C29 hopane significantly increased. The deep lake basin shows depositional fluctuations, as indicated by rock lithofacies and their geochemical parameters. A close interrelationship was observed among U concentration, TOC content, and inorganic element content. Uranium concentrations are positively correlated with TOC contents, Ca and Sr concentrations, and Sr/Ba and Ca/Mg ratios but negatively with K, Na, Ba, and Rb contents and Fe/(Ca + Mg) and Fe/Mn ratios. The observed increase in U concentration in the lower Es3 section is closely related to surface adsorption by clay minerals and OM, together with some replacements of Ca and Sr by U in the shales.  相似文献   

16.
Cretaceous sedimentary rocks of the Mukalla, Harshiyat and Qishn formations from three wells in the Jiza sub-basin were studied to describe source rock characteristics, providing information on organic matter type, paleoenvironment of deposition and hydrocarbon generation potential. This study is based on organic geochemical and petrographic analyses performed on cuttings samples. The results were then incorporated into basin models in order to understand the burial and thermal histories and timing of hydrocarbon generation and expulsion.The bulk geochemical results show that the Cretaceous rocks are highly variable with respect to their genetic petroleum generation potential. The total organic carbon (TOC) contents and petroleum potential yield (S1 + S2) of the Cretaceous source rocks range from 0.43 to 6.11% and 0.58–31.14 mg HC/g rock, respectively indicating non-source to very good source rock potential. Hydrogen index values for the Early to Late Cretaceous Harshiyat and Qishn formations vary between 77 and 695 mg HC/g TOC, consistent with Type I/II, II-III and III kerogens, indicating oil and gas generation potential. In contrast, the Late Cretaceous Mukalla Formation is dominated by Type III kerogen (HI < 200 mg HC/g TOC), and is thus considered to be gas-prone. The analysed Cretaceous source rock samples have vitrinite reflectance values in the range of 0.37–0.95 Ro% (immature to peak-maturity for oil generation).A variety of biomarkers including n-alkanes, regular isoprenoids, terpanes and steranes suggest that the Cretaceous source rocks were deposited in marine to deltaic environments. The biomarkers also indicate that the Cretaceous source rocks contain a mixture of aquatic organic matter (planktonic/bacterial) and terrigenous organic matter, with increasing terrigenous influence in the Late Cretaceous (Mukalla Formation).The burial and thermal history models indicate that the Mukalla and Harshiyat formations are immature to early mature. The models also indicate that the onset of oil-generation in the Qishn source rock began during the Late Cretaceous at 83 Ma and peak-oil generation was reached during the Late Cretaceous to Miocene (65–21 Ma). The modeled hydrocarbon expulsion evolution suggests that the timing of oil expulsion from the Qishn source rock began during the Miocene (>21 Ma) and persisted to present-day. Therefore, the Qishn Formation can act as an effective oil-source but only limited quantities of oil can be expected to have been generated and expelled in the Jiza sub-basin.  相似文献   

17.
The discovery of the giant Daqing oil field in the Songliao Basin led to the realisation of the significant petroleum potential of non-marine basins. In order to reconstruct the basin evolution and oil formation, an integrated organic geochemical-basin modelling study along a regional transect across the Songliao Basin was conducted. It provided a regional heat flow evolution model, and revealed post-orogenic or late syn-orogenic maturation in the Central Depression and pre-orogenic maturation in the Southeast Uplift Zone. Kinetic parameters of petroleum generation for the lacustrine source formations are the basis for the simulation of oil generation and migration in the Songliao Basin. Using the principle activation energy peaking at 54 kcal/mol and a pre-exponential factor of about 4.2·1027 Ma−1, the simulation obtained a relatively good match with the measured transformation ratios. The Qingshankou Formation in the West and East Central Depressions constituted the major source in the basin. Major oil generation, migration and accumulation occurred during the Early Tertiary. In the West Central Depression, the generated oils migrated upwards into the Yaojia Formation followed by the updip migration into the Daqing Anticline and towards the local structural high along the West Slope. In contrast, the oil migration in the East Central Depression was dominated by the downward movement from the lower member of the Qingshankou Formation followed by the updip migration towards the Caoyang Anticline. The simulated oil accumulations are in good agreement with discovered oil fields, implying a potential application of the model for prediction and evaluation of new exploration targets in the basin.  相似文献   

18.
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 C28/C29 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 Tmax (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 Tmax 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.  相似文献   

19.
The sedimentary system of Kalimantan has undergone significant development since the Oligocene. Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks. Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences bet...  相似文献   

20.
In recent years, new oil reservoirs have been discovered in the Eocene tight sandstone of the Huilu area, northern part of the Pearl River Mouth basin, South China Sea, indicating good prospects for tight oil exploration in the area. Exploration has shown that the Huilu area contains two main sets of source rocks: the Eocene Wenchang (E2w) and Enping (E2e) formations. To satisfy the requirements for further exploration in the Huilu area, particularly for tight oil in Eocene sand reservoirs, it is necessary to re-examine and analyze the hydrocarbon generation and expulsion characteristics. Based on mass balance, this study investigated the hydrocarbon generation and expulsion characteristics as well as the tight oil resource potential using geological and geochemical data and a modified conceptual model for generation and expulsion. The results show that the threshold and peak expulsion of the E2w source rocks are at 0.6% vitrinite reflectance and 0.9% vitrinite reflectance, respectively. There were five hydrocarbon expulsion centers, located in the western, eastern, and northern Huizhou Sag and the southern and northern Lufeng Sag. The hydrocarbon yields attributed to E2w source rocks are 2.4 × 1011 tons and 1.6 × 1011 tons, respectively, with an expulsion efficiency of 65%. The E2e source rock threshold and peak expulsion are at 0.65% vitrinite reflectance and 0.93% vitrinite reflectance, respectively, with hydrocarbon expulsion centers located in the centers of the Huizhou and Lufeng sags. The yields attributed to E2e source rocks are 1.1 × 1011 tons and 0.2 × 1011 tons, respectively, with an expulsion efficiency of 20%. Using an accumulation coefficient of 7%–13%, the Eocene tight reservoirs could contain approximately 1.3 × 1010 tons to 2.3 × 1010 tons, with an average of 1.8 × 1010 tons, of in-place tight oil resources (highest recoverable coefficient can reach 17–18%), indicating that there is significant tight oil potential in the Eocene strata of the Huilu area.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号