The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Pa...The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.展开更多
Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions...Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.展开更多
Source rocks(shales) exhibit different geometric pore types and considerable anisotropy caused by the preferential orientation of the clay and kerogen layers,which is not accounted for in classical rockphysics models....Source rocks(shales) exhibit different geometric pore types and considerable anisotropy caused by the preferential orientation of the clay and kerogen layers,which is not accounted for in classical rockphysics models.Pore geometry can be effectively studied through the aspect ratio,and in this study,we use the aspect ratio to characterize different pore geometries.Then,we consider a pore connectivity index as well as a lamination index associated with these orientations.An inclusion-based theory(differential effective medium and self-consistent approximation) and the Brown-Korringa equations are used in the modeling approach.The results show that the indices as well as the aspect ratio of the connected pores significantly affect the elastic properties.We propose an inversion method to invert these three parameters simultaneously from experimental vertical P-and S-wave velocities using a global optimization algorithm.The method is applied to well log and seismic data from the Longmaxi shale reservoir in southwest China to verify its pre dictive ability.展开更多
This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source...This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source rocks in the Wucaiwan sag,Junggar Basin,China as proxies(1)for evaluations of hydrocarbon potential,organic matter(OM)composition and thermal maturity of the OM in the source rocks,(2)for reconstruction of paleodepositional environment,and(3)for analysis of controlling factor of organic carbon accumulation.The P_(2)p Formation developed good-excellent source rocks with thermal maturity of OM ranging from low-mature to mature stages.The OM was mainly composed of C_(3)terrestrial higher plants and aquatic organisms including aerobic bacteria,green sulfur bacteria,saltwater and fresh algae,Sphagnum moss species,submerged macrophytes,Nymphaea,and aquatic pollen taxa.The proportion of terrestrial higher plants decreased and that of aquatic organisms increased from margin to center of the sag.The benthic water within reducing environment and brackishwater column were superposed by periodic/occasional fresh-water influx(e.g.,rainfall and river drain),which led to fresh-water conditions and well oxygenating in the water column during overturn process.The whole study area developed lacustrine source rocks without seawater intrusion.During periodic/occasional fresh-water influx periods with plenty of terrestrial plant inputs,the paleoredox conditions of the sag were relatively oxic in the shallow fresh-water which experienced strong oxidation and decomposition of OM,therefore were not conducive for the OM preservation.However,the overall middle primary productivity made up for this deficiency,and was the main controlling factor on the organic carbon accumulation.A suitable supply from terrestrial inputs can promote biotic paleoproductivity,and a relatively high sedimentation rate can reduce oxidation and decomposition times of OM.On the contrary,during the intervals of the fresh-water influxes,relatively reducing conditions are a more important controlling factor on the OM accumulation in the case that the decrease of the terrestrial biotic source.展开更多
Coaly source rocks have attracted considerable attention for their significant hydrocarbon generation potential in recent years. However, limited study is performed on utilizing geochemical data and well log data to e...Coaly source rocks have attracted considerable attention for their significant hydrocarbon generation potential in recent years. However, limited study is performed on utilizing geochemical data and well log data to evaluate coaly hydrocarbon source rocks. In this study, geochemical data and well log data are selected from two key wells to conduct an evaluation of coaly hydrocarbon source rocks of Jurassic Kezilenuer Formation in Kuqa Depression of Tarim Basin. Initially, analysis was focused on geochemical parameters to assess organic matter type, source rock quality, and hydrocarbon generation potential.Lithology types of source rocks include mudstone, carbonaceous mudstone and coal. The predominant organic matter type identified was Type Ⅲ and Type Ⅱ_(2), indicating a favorable hydrocarbon generation potential. Well log data are integrated to predict total organic carbon(TOC) content, and the results indicate that multiple regression method is effective in predicting TOC of carbonaceous mudstone and coal. However, the ΔlgR method exhibited limited predictive capability for mudstone source rock.Additionally, machine learning methods including multilayer perceptron neural network(MLP), random forest(RF), and extreme gradient boosting(XGBoost) techniques are employed to predict TOC of mudstone source rock. The XGBoost performs best in TOC prediction with correlation coefficient(R2) of 0.9517, indicating a close agreement between measured and predicted TOC values. This study provides a reliable prediction method of coaly hydrocarbon source rocks through machine learning methods, and will provide guidance for resource assessment.展开更多
The Upper Triassic successions in the Qiangtang Basin are critical targets for petroleum exploration,yet the key factors controlling OM(organic matter)enrichment in the Bagong Formation source rocks remain unclear.The...The Upper Triassic successions in the Qiangtang Basin are critical targets for petroleum exploration,yet the key factors controlling OM(organic matter)enrichment in the Bagong Formation source rocks remain unclear.The source rock characteristics and sedimentary environments of the Bagong Formation in the Upper Triassic from well QS9 in the eastern North Qiangtang Basin were analysed through organic geochemistry and major and trace element data,and the factors governing OM enrichment were identified.The results reveal that the TOC content ranges from 0.29%to 2.20%(avg.1.13%).Organic matter from land plants and plankton is characterized by typeⅡ_(2)kerogen but is close to typeⅢkerogen.Organic matter is thermally mature to highly mature.The palaeoclimate shifted from hot with intense weathering to warm with humid moderate weathering.The depositional environments were marine and oxic-suboxic water conditions,with oxidation in the lower part and suboxidation in the upper part.OM enrichment is controlled by the evolution of the sedimentary environment(climate,sea level,and clastic input)and local reducing conditions.This conclusion provides a clear scientific basis for petroleum exploration and high-quality source rock prediction of the Bagong Formation source rocks in the study area.展开更多
An integrated study on source rock characterization and hydrocarbon generation potential modeling was conducted for the selected Dingo Claystone,Barrow Sub-basin,Australia.In this study,data were collected solely from...An integrated study on source rock characterization and hydrocarbon generation potential modeling was conducted for the selected Dingo Claystone,Barrow Sub-basin,Australia.In this study,data were collected solely from two wells represented by the Bambra-1 and Bambra-2 wells.The collected data include those from bulk geochemical analyses of cuttings and sidewall cores sampled from the Late Jurassic Dingo Claystone.Geochemical data obtained from Rock-Eval pyrolysis and gas chromatography(GC)of extracted organic matter were integrated for source rock characterization and the construction of burial history and hydrocarbon generation in the Dingo Claystone.To improve the accuracy of thermal maturity estimations,only samples with S2 greater than 1 were considered due to potential issues with peak integration and uncertainties of Tmax determination in samples with lower S2 values.Furthermore,Rock-Eval data from the Bambra wells may be unreliable due to the contamination of cuttings and sidewall core(SWC)samples by drilling mud additives and natural hydrocarbons,which could impact the reliability of the data for determining thermal maturity.This study reveals that the Dingo Claystone Formation has total organic carbon(TOC)contents ranging from 0.66%to 8.31%.A poor to good hydrocarbon generation potential is indicated,with a production yield(PY=S_(1)+S_(2))ranging from 1.37 to 10.44 mg HC/g rock.Hydrogen index values vary between 42 and 226 mg HC/g TOC,confirming that the Dingo Claystone is dominantly kerogen TypeⅢ,with minor contributions from typesⅡ/ⅢandⅣ.Thermal maturity ranges from immature to late mature and is mostly in the oil window.This is indicated by T_(max)values of 398-462℃and vitrinite reflectance(Ro,%)of 0.47-1.99.Some samples show suppressed T_(max)and a higher production index,which is typical for samples affected by drilling fluids during drilling operations.Additionally,gas chromatography(GC)analyses are used to interpret the paleodepositional environment showing mixed input between marine and terrestrial origins of the source rocks.One-dimensional basin modeling for the Bambra-1 and Bambra-2 wells was carried out to evaluate the burial and thermal history of the formation.The transformation ratio suggests that hydrocarbon generation has not reached its peak and is still in an ongoing phase.An indication of hydrocarbon migration can be observed in this formation based on the transformation ratio.The effects of contamination warrant further investigation,as it could significantly impact maturity estimates and data reliability.展开更多
The importance of organic geochemistry and basin modeling is widely recognized and used to understand the source rock potential and hydrocarbon generation history of the Mangahewa Formation,and thereby given the found...The importance of organic geochemistry and basin modeling is widely recognized and used to understand the source rock potential and hydrocarbon generation history of the Mangahewa Formation,and thereby given the foundational role in the petroleum exploration.This study utilized the total organic carbon(TOC)content and hydrogen index(HI)to investigate the dominant kerogen type and hydrogen richness for the significance of petroleum generative potential.The Mangahewa coals and carbonaceous shales exhibit an excellent source rocks,with high total organic content(TOC)of more than 22%.The coals and carbonaceous shales were also characterised by Type Ⅱ‒Ⅲ kerogen with Type Ⅲ kerogen,promising oiland gas-prones.The Mangahewa Formation reached the main oil generation,with vitrinite reflectances between 0.53%and 1.01%.Vitrinite reflectance was also used in developing themal models and reveal the transformation(TR)of 10‒50%kerogen to oil during the Late Miocene.The models also showed that the Mangahewa source rock has a significant oil generation and little expulsion competency,with a TR of up to 54%.These findings support the substantial oil-generating potential in the Taranaki Basin's southern graben and can be used as a guide when developing strategies for an oil exploration program.展开更多
To quantitatively study the location errors induced by deviation of sonic speed, the line and plane location tests were carried out. A broken pencil was simulated as acoustic emission source in the rocks. The line and...To quantitatively study the location errors induced by deviation of sonic speed, the line and plane location tests were carried out. A broken pencil was simulated as acoustic emission source in the rocks. The line and plane location tests were carried out in the granite rod using two sensors and the cube of marble using four sensors, respectively. To compare the position accuracy between line and plane positions, the line poison test was also carried out on the marble surface. The results show that for line positioning, the maximum error of absolute distance is about 0.8 cm. With the speed difference of 200 m/s, the average value of absolute difference from the position error is about 0.4 cm. For the plane positioning, in the case of the sensor array of 30 cm, the absolute positioning distance is up to 8.7 cm. It can be seen that the sonic speed seriously impacts on the plane positioning accuracy. The plane positioning error is lager than the line positioning error, which means that when the line position can satisfy the need in practical engineering, it is better to use the line position instead of the plane location. The plane positioning error with the diagonal speed is the minimum one.展开更多
Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate ...Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths <400 m and totally released at the depths >7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective helium source rock is established. We suggest exploring He resources in hydrocarbon basins with granitic basement(or adjacent to granite bodies), high geothermal field, and young active fractures.展开更多
The exploration conducted in the Bohai Bay basin, eastern China has demonstrated that the abundant petroleum resources have close affinities to the hydrocarbon kitchen with rich organic matter. A number of oil-generat...The exploration conducted in the Bohai Bay basin, eastern China has demonstrated that the abundant petroleum resources have close affinities to the hydrocarbon kitchen with rich organic matter. A number of oil-generating associations with various characteristics of organic geochemistry and assemblages of multiple reservoir facies are developed due to the multi-center sedimentation, multi-source supply and multi-cycle evolution of filling, which have resulted in the formation of multiple oil and gas accumulation zones of various layers and trap styles. Among them the Paleogene Shahejie Formation is the most important hydrocarbon accumulation combination in the Dongying sag. Heretofore, its proved reserve has reached nearly 1.8×109t, which accounts for more than 90% of the total proved reserves of the Dongying sag. Based on previous studies, more than 600 source rock samples and 186 crude oil samples of the Shahejie Formation, collected from 30 oilfields, have been treated with organic geochemical testing. By combining the sedimentary sequence characteristics and geochemical analysis results, the source rocks of the Shahejie Formation can be divided into three genetic types, i.e. the saline lake facies (the upper ES4, brackish water deep lake facies (the lower ES3) and fresh-water lake facies (the middle ES3), which correspond to the under-filling, balanced-filling and over-filling lake types respectively and represent the three most essential genetic models for source rocks of non-marine fault basins in China. Based on a thorough oil-source correlation, the source rocks of the saline lake and brackish deep lake facies are determined to be the most contributive source rocks in the Dongying sag. Furthermore, by probing into the accumulation of organic matter and hydrocarbon migration pattern, it can be inferred that the hydrocarbons, generated from source rocks of the saline lake facies with relatively low maturity, have mainly accumulated in the uplifted parts of the basin's margin via lateral migration and the reservoirs are dominated by the buried hill and stratigraphic types, while hydrocarbons generated from source rocks of the brackish lake facies are mainly distributed in the basin's center via vertical migration and characterized by forming lithologic reservoirs. Also, the reservoirs located in the transitional belts have complex types and mostly controlled by faults, characterized by block (structural-lithologic) reservoirs, and the crude oils mainly come from source beds of Es31 and Es42 respectively.展开更多
There are significant differences in type and distribution between marine source rock and continental source rock. According to the iithology, the Cambrian-Ordovician source rock in the Tarim basin is divided into two...There are significant differences in type and distribution between marine source rock and continental source rock. According to the iithology, the Cambrian-Ordovician source rock in the Tarim basin is divided into two types： the carbonate source rock and the mud source rock. The two sets of source rocks are developed mainly in three sets of formations, Lower-Middle Cambrian carbonate source rock and mud source rock, Lower-Middle Ordovician mud source rock and Upper Ordovician lime mud source rock. The stratigraphic and areal distributions of the source rocks are controlled by the altitude and the sedimentary facies respectively. The mud source rock is developed in slope-semi deep sea environment. The source rock developed in the slope sedimentary environment is related with the anoxic environment and the one developed in semi deep sea has a close relationship with the up-flowing sea water. The carbonate source rock is developed mainly in platform slope of highstand systems tract and it is usually intimately associated with the salt rock. The Lower-Middle Cambrian carbonate source rock is developed mainly in the Bachu, Tazhong, Tangguzibasi and Yingmaili areas. The Lower-Middle Cambrian mud source rock is mainly developed in the areas east of the line of Kunan 1-Tadong 1. The Lower-Middle Ordovician mud source rock is developed mainly in the east slope of the Manjiaer depression. The carbonate source rock of Early Ordovician is developed mainly in the platform slope of highstand systems tract, such as the south margin of Tabei, the north slope of Tazhong, the Bachu area and Keping area.展开更多
Carbonates have been known to act as hydrocarbon source rocks, but their basic geochemical and associated hydrocarbon generation characteristics remain not well understood as they occur with argillaceous source rocks ...Carbonates have been known to act as hydrocarbon source rocks, but their basic geochemical and associated hydrocarbon generation characteristics remain not well understood as they occur with argillaceous source rocks in most cases, and the hydrocarbon generation from each rock type is di cult to distinguish, forming one of puzzling issues within the field of petroleum geology and geochemistry. To improve the understanding of this critical issue, this paper reviews recent advances in this field and provides a summary of key areas that can be studied in future. Results show that carbonate source rocks are generally associated with high-salinity environments with low amounts of terrestrial inputs and low dissolved oxygen contents. Petrographically, these source rocks are dark gray or black, fine-grained, stratified, and contain bacterial and algal bioprecursors along with some other impurities. They generally have low organic matter contents, although these can vary significantly in di erent cases(e.g., the total organic carbon contents of marine and lacustrine carbonate source rocks in China are generally 0.1%–1.0% and 0.4%–4.0%, respectively). These rocks contain type I and type II kerogen, meaning there is a lack of vitrinites. This means that assessment of the maturity of the organic matter in these sediments needs to use non-traditional techniques rather than vitrinite reflectance. In terms of molecular geochemistry, carbonate source rocks have typical characteristics indicative of generally reducing and saline environments and lower organism-dominated bioprecursors of organic matter, e.g., high contents of sulfur compounds, low Pr/Ph ratios, and dominance of n-alkanes. Most of the carbonate source rocks are typically dominated by D-type organic facies in an oxidized shallow water mass, although high-quality source rocks generally contain A-and B-type organic facies in saline lacustrine and marine-reducing environments, respectively. The hydrocarbon generation model for the carbonate source rocks can involve early, middle, and late stages, with a diversity of hydrocarbons within these rocks, which can be aggregated, adsorbed, enclosed within minerals, or present as inclusions. This in turn implies that the large-scale hydrocarbon expulsion from these rocks is reliant on brittle deformation caused by external forces. Finally, a number of aspects of these source rocks remain unclear and need further study, including the e ectiveness of carbonates as hydrocarbon source rocks, bioprecursors, and hydrocarbon generation models of carbonate source rock, and the di erences between marine and lacustrine carbonate source rocks.展开更多
The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to charact...The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.展开更多
The Cretaceous is one of the most important stratigraphic intervals for hydrocarbon source rocks. This article summarizes the distribution, formation, and development characteristics of Cretaceous source rocks and ass...The Cretaceous is one of the most important stratigraphic intervals for hydrocarbon source rocks. This article summarizes the distribution, formation, and development characteristics of Cretaceous source rocks and associated oil and gas resources in the world and China, aiming at improving the understanding of this hydrocarbon enrichment and at broadening domestic exploration. Outside China, these rocks are generally formed in marine or transgressive environments during both the Upper and Lower Cretaceous. The majority of Cretaceous source rocks are located in the Persian Gulf, Mediterranean, and Gulf Coast of the USA. Kerogen types within these source rocks have distinct spatial distribution characteristics, with high-latitude Boreal Realm, Tethyan Realm and South Gondwana Realm source rocks containing type III, II, II-III kerogens, respectively. Cretaceous source rocks in China can be mainly divided into four zones： Eastern, Central, Northwest, and Qinghai-Tibet Plateau zones. The majority of Chinese source rocks formed in the Early Cretaceous, whereas the most productive source rocks are developed in the Upper Cretaceous, such as those within the Songliao Basin. Most of these basins are formed in lacustrine environments, although some may have been influenced by transgressive events： Cretaceous source rocks are formed in four distinctive ways： 1） during Oceanic Anoxic Events and associated global sea-level rises, 2） in Black Sea-type retention basins, 3） during transgression and 4） during periods of significant terrestrial input. Formation of these source rocks is controlled by four factors： paleoclimate, paleotopography, transgression, and Oceanic Anoxic Events. These four major controlling factors indicate that China＇s hydrocarbon exploration within the Cretaceous should focus on two key areas with extremely low exploration levels, the Qinghai-Tibet Plateau and the southeastern coast of China.展开更多
With the analysis of the element geochemistry characteristics, the ancient lake infor- mation evolution history of the argillaceous source rocks in Lucaogou 0~/~＇~） Formation in San- gonghe area is reconstructed. A...With the analysis of the element geochemistry characteristics, the ancient lake infor- mation evolution history of the argillaceous source rocks in Lucaogou 0~/~＇~） Formation in San- gonghe area is reconstructed. According to the ancient lake information and total organic matter （TOC） characteristics of argillaceous source rocks, the study section is divided into 6 Subsec- tions. Subsection I mainly developed low-quality source rocks. This is because of the arid climate, high salinity, low lake productivity, unstable preservation conditions in this Subsection. Subsection II mainly developed high-quality source rocks. This is because of the humid climate, low salinity, high lake productivity, stable preservation conditions in this Subsection. Though the paleoclimate was humid and preservation conditions were stable. Lake productivity and the water salinity changed frequently. So Subsection III mainly developed medium-quality source rocks. Because of the humid climate, high lake productivity, medium sedimentary rate and stable preservation conditions, high-quality source rocks were developed in Subsection IV. The preservation conditions were stable, but other ancient lake information changed frequently. Therefore, the quality of the formed source rocks in Subsection V was different. Subsection VI mainly developed high-quality source rocks be- cause of the humid climate, medium sedimentary rate, high lake productivity, low salinity and good preservation conditions. In summary, the ancient lake information parameters and TOC characteris- tics of each Subsection are different from each other.展开更多
Petroleum was generated from sedimentary rocks. The world＇s oldest oil source rock so far was found in Proterozoic rocks. Since then, 73% to 81% of the earth＇s surface has been covered with sedimentary rocks. Howeve...Petroleum was generated from sedimentary rocks. The world＇s oldest oil source rock so far was found in Proterozoic rocks. Since then, 73% to 81% of the earth＇s surface has been covered with sedimentary rocks. However, only quite a limited area is rich in oil and gas. It is found that source rocks have controlled oil and gas distribution, and they are mainly formed in two systems： （1） river-lake systems and （2） river-gulf systems. Phytoplankton is an important source of kerogen, the blooming of which is strongly dependent on nutrients. Rivers are the major nutrient provider for basins. Rivers around lakes and an undercompensation （where the sedimentation rate is less than the rate of basin subsidence） environment provide favorable conditions for phytoplankton blooming in lakes. Gulfs are usually located at the estuary of big rivers, characterized by restricted current circulation and exchange with the open sea, which benefit maintaining the nutrient density, phytoplankton levels and organic matter preservation. The river-gulf system is the most favorable place for marine source rock development. Most of the world famous marine petroleum-rich provinces are developed from river-gulf systems in geological history, such as the Persian Gulf Basin, Siberian Basin, Caspian Basin, North Sea, Sirte Basin, Nigerian Basin, Kwanza Basin, Gulf of Mexico, Maracaibo Basin and the Eastern Venezuelan Basin.展开更多
Carboniferous source rocks identified by drilling in Santanghu （三塘湖） Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositio...Carboniferous source rocks identified by drilling in Santanghu （三塘湖） Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositional environment of these samples were also determined through biomarker analysis. Most of the Carboniferous source rocks in Santanghu Basin are characterised by high values of total organic carbon （TOC） content and high extractable organic matter content and hydrocarbon yields, indicating that they are organicrich source rocks with high oil generative potential. The organic matter is predominantly Type I and Type II kerogen with a minor contribution of Type III kerogen, as demonstrated by its pyrolysis parameters and carbon isotope values. According to Ro （%） and T max values, most of the studied samples are at earlyto middle-thermal mature stage; only a few of the samples are at a highly mature stage （past peak oil generation）. The biomarker analysis reveals a dominance of algal/bacterial organic matter input, with a minor contribution of land plant material. Pr/Ph ratio supports a suboxic depositional condition, consistent with a neritic or marine-continental alternating environment proposed by predecessor.展开更多
The theory of ＂source rock control＂ has evolved from source-rock-control hydrocarbon accumulation, to effective source-rock-control hydrocarbon accumulation, and to high-quality source- rock-control hydrocarbon accu...The theory of ＂source rock control＂ has evolved from source-rock-control hydrocarbon accumulation, to effective source-rock-control hydrocarbon accumulation, and to high-quality source- rock-control hydrocarbon accumulation. However, there are problems, such as whether high-quality source rocks exist or not？ What high-quality source rocks are, and how to identify them, are yet to be agreed upon. Aimed at this issue of concern to explorationists, and taking the Beier Sag in the Hailaer Basin as an example, this paper defines the high-quality source rocks and the lower limit for evaluation of high-quality source rocks, by using the inflection point on the relationship curve of hydrocarbon （oil） expulsion, which is calculated by the material balance principle, versus total organic carbon （TOC）. The results show that when TOC is low, all source rocks have limited hydrocarbon expulsion and slow growth rate, thus they cannot be high-quality source rocks. However, when TOC rises to some threshold, hydrocarbon expulsion increases significantly with TOC. This inflection point should be the lower limit of high-quality source rocks： those with TOC greater than the inflection-point value are high-quality source rocks. In addition, the lower limit of high-quality source rocks is also related to the type and maturity of organic matters in the source rocks, as well as the mineral components of the source rocks affecting the residual hydrocarbons. Theoretically, the lower limit of high-quality source rocks depends on geological conditions rather than being a constant value. However, for the sake of simplicity and practicability, in this paper TOC=2.0% is regarded as the lower limit of high-quality source rocks. The examination of such standard in the work area indicates that the high-quality source rocks in members K^n2 and K^n~ of the Nantun formation contribute 76% and 82% to oil generation, and 96% and 91% to oil expulsion, respectively. The distribution of high-quality source rocks is also closely related to the distribution of hydrocarbon reservoirs in the region, demonstrating that high-quality source rocks control hydrocarbon accumulation.展开更多
The shale of Yanchang Formation in Upper Triassic is the most important source rock for the Mesozoic petroleum reserviors in Ordos Basin. Chang 7 and Chang 4＋5 members are the major source rock formation. Source rock...The shale of Yanchang Formation in Upper Triassic is the most important source rock for the Mesozoic petroleum reserviors in Ordos Basin. Chang 7 and Chang 4＋5 members are the major source rock formation. Source rock samples, obtained from 22 cored wells in central Ordos Basin, were geochemically analyzed to determine the organic matter abundance, kerogen type and thermal maturity. Total organic carbon values ranged from 0.36% to 19.10%, 8.09% on average, in- dicating a good source rock potential. In this area, the shale is mature, as indicated by vitrinite re- flectance values. RockoEval data revealed that the samples are dominated by type II kerogen. Com- pare the Chang 7 and Chang 4＋5 members, which suggests that the Chang 7 shale has higher TOC, especially the highest lower Chang 7 members. The abundance of organic matter of Chang 4＋5 and Chang 7 members is both richest in southeast basin. The kerogen type of Chang 4＋5 and upper Chang 7 members is type II~, the counterpart of middle and lower Chang 7 member is type I. During the burial history, the total hydrocarbon-generating quantity of Chang 7 member is much more than that of Chang 4＋5 members.展开更多
基金supported by the CNPC Science and Technology Major Project of the Fourteenth Five-Year Plan(2021DJ0101)the National Natural Science Foundation of China(U19B600302,41872148)。
文摘The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.
基金Supported by the Research Project of China National Offshore Oil Corporation(SCKY-2023-HN-3)。
文摘Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.
基金funded by the National Natural Science Foundation of China (No. 42374128)by the Fundamental Research Funds for the Central Universities (No. B240201110)。
文摘Source rocks(shales) exhibit different geometric pore types and considerable anisotropy caused by the preferential orientation of the clay and kerogen layers,which is not accounted for in classical rockphysics models.Pore geometry can be effectively studied through the aspect ratio,and in this study,we use the aspect ratio to characterize different pore geometries.Then,we consider a pore connectivity index as well as a lamination index associated with these orientations.An inclusion-based theory(differential effective medium and self-consistent approximation) and the Brown-Korringa equations are used in the modeling approach.The results show that the indices as well as the aspect ratio of the connected pores significantly affect the elastic properties.We propose an inversion method to invert these three parameters simultaneously from experimental vertical P-and S-wave velocities using a global optimization algorithm.The method is applied to well log and seismic data from the Longmaxi shale reservoir in southwest China to verify its pre dictive ability.
基金financially supported by the National Natural Science Foundation of China(NSFC)(No.42202154)the Science Foundation of China University of Petroleum,Beijing(No.ZX20220074)。
文摘This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source rocks in the Wucaiwan sag,Junggar Basin,China as proxies(1)for evaluations of hydrocarbon potential,organic matter(OM)composition and thermal maturity of the OM in the source rocks,(2)for reconstruction of paleodepositional environment,and(3)for analysis of controlling factor of organic carbon accumulation.The P_(2)p Formation developed good-excellent source rocks with thermal maturity of OM ranging from low-mature to mature stages.The OM was mainly composed of C_(3)terrestrial higher plants and aquatic organisms including aerobic bacteria,green sulfur bacteria,saltwater and fresh algae,Sphagnum moss species,submerged macrophytes,Nymphaea,and aquatic pollen taxa.The proportion of terrestrial higher plants decreased and that of aquatic organisms increased from margin to center of the sag.The benthic water within reducing environment and brackishwater column were superposed by periodic/occasional fresh-water influx(e.g.,rainfall and river drain),which led to fresh-water conditions and well oxygenating in the water column during overturn process.The whole study area developed lacustrine source rocks without seawater intrusion.During periodic/occasional fresh-water influx periods with plenty of terrestrial plant inputs,the paleoredox conditions of the sag were relatively oxic in the shallow fresh-water which experienced strong oxidation and decomposition of OM,therefore were not conducive for the OM preservation.However,the overall middle primary productivity made up for this deficiency,and was the main controlling factor on the organic carbon accumulation.A suitable supply from terrestrial inputs can promote biotic paleoproductivity,and a relatively high sedimentation rate can reduce oxidation and decomposition times of OM.On the contrary,during the intervals of the fresh-water influxes,relatively reducing conditions are a more important controlling factor on the OM accumulation in the case that the decrease of the terrestrial biotic source.
基金supported by Science Foundation of China University of Petroleum(Beijing)(No.2462023QNXZ010).
文摘Coaly source rocks have attracted considerable attention for their significant hydrocarbon generation potential in recent years. However, limited study is performed on utilizing geochemical data and well log data to evaluate coaly hydrocarbon source rocks. In this study, geochemical data and well log data are selected from two key wells to conduct an evaluation of coaly hydrocarbon source rocks of Jurassic Kezilenuer Formation in Kuqa Depression of Tarim Basin. Initially, analysis was focused on geochemical parameters to assess organic matter type, source rock quality, and hydrocarbon generation potential.Lithology types of source rocks include mudstone, carbonaceous mudstone and coal. The predominant organic matter type identified was Type Ⅲ and Type Ⅱ_(2), indicating a favorable hydrocarbon generation potential. Well log data are integrated to predict total organic carbon(TOC) content, and the results indicate that multiple regression method is effective in predicting TOC of carbonaceous mudstone and coal. However, the ΔlgR method exhibited limited predictive capability for mudstone source rock.Additionally, machine learning methods including multilayer perceptron neural network(MLP), random forest(RF), and extreme gradient boosting(XGBoost) techniques are employed to predict TOC of mudstone source rock. The XGBoost performs best in TOC prediction with correlation coefficient(R2) of 0.9517, indicating a close agreement between measured and predicted TOC values. This study provides a reliable prediction method of coaly hydrocarbon source rocks through machine learning methods, and will provide guidance for resource assessment.
基金the Deep Earth probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2025ZD1004600)the National Natural Science Foundation of China(Grant No.42102201)+2 种基金the Chinese Academy of Geological Sciences Basal Research Fund(Grant No.JKYQN202410)the Shaanxi Coal Geology Group Project(Grant No.SMDZ-2022ZD-8)the China Geological Survey Project(Grant No.DD20230200109)。
文摘The Upper Triassic successions in the Qiangtang Basin are critical targets for petroleum exploration,yet the key factors controlling OM(organic matter)enrichment in the Bagong Formation source rocks remain unclear.The source rock characteristics and sedimentary environments of the Bagong Formation in the Upper Triassic from well QS9 in the eastern North Qiangtang Basin were analysed through organic geochemistry and major and trace element data,and the factors governing OM enrichment were identified.The results reveal that the TOC content ranges from 0.29%to 2.20%(avg.1.13%).Organic matter from land plants and plankton is characterized by typeⅡ_(2)kerogen but is close to typeⅢkerogen.Organic matter is thermally mature to highly mature.The palaeoclimate shifted from hot with intense weathering to warm with humid moderate weathering.The depositional environments were marine and oxic-suboxic water conditions,with oxidation in the lower part and suboxidation in the upper part.OM enrichment is controlled by the evolution of the sedimentary environment(climate,sea level,and clastic input)and local reducing conditions.This conclusion provides a clear scientific basis for petroleum exploration and high-quality source rock prediction of the Bagong Formation source rocks in the study area.
文摘An integrated study on source rock characterization and hydrocarbon generation potential modeling was conducted for the selected Dingo Claystone,Barrow Sub-basin,Australia.In this study,data were collected solely from two wells represented by the Bambra-1 and Bambra-2 wells.The collected data include those from bulk geochemical analyses of cuttings and sidewall cores sampled from the Late Jurassic Dingo Claystone.Geochemical data obtained from Rock-Eval pyrolysis and gas chromatography(GC)of extracted organic matter were integrated for source rock characterization and the construction of burial history and hydrocarbon generation in the Dingo Claystone.To improve the accuracy of thermal maturity estimations,only samples with S2 greater than 1 were considered due to potential issues with peak integration and uncertainties of Tmax determination in samples with lower S2 values.Furthermore,Rock-Eval data from the Bambra wells may be unreliable due to the contamination of cuttings and sidewall core(SWC)samples by drilling mud additives and natural hydrocarbons,which could impact the reliability of the data for determining thermal maturity.This study reveals that the Dingo Claystone Formation has total organic carbon(TOC)contents ranging from 0.66%to 8.31%.A poor to good hydrocarbon generation potential is indicated,with a production yield(PY=S_(1)+S_(2))ranging from 1.37 to 10.44 mg HC/g rock.Hydrogen index values vary between 42 and 226 mg HC/g TOC,confirming that the Dingo Claystone is dominantly kerogen TypeⅢ,with minor contributions from typesⅡ/ⅢandⅣ.Thermal maturity ranges from immature to late mature and is mostly in the oil window.This is indicated by T_(max)values of 398-462℃and vitrinite reflectance(Ro,%)of 0.47-1.99.Some samples show suppressed T_(max)and a higher production index,which is typical for samples affected by drilling fluids during drilling operations.Additionally,gas chromatography(GC)analyses are used to interpret the paleodepositional environment showing mixed input between marine and terrestrial origins of the source rocks.One-dimensional basin modeling for the Bambra-1 and Bambra-2 wells was carried out to evaluate the burial and thermal history of the formation.The transformation ratio suggests that hydrocarbon generation has not reached its peak and is still in an ongoing phase.An indication of hydrocarbon migration can be observed in this formation based on the transformation ratio.The effects of contamination warrant further investigation,as it could significantly impact maturity estimates and data reliability.
基金Supporting Project number(RSP2025R92)at King Saud University,Riyadh,Saudi Arabia,for their support.
文摘The importance of organic geochemistry and basin modeling is widely recognized and used to understand the source rock potential and hydrocarbon generation history of the Mangahewa Formation,and thereby given the foundational role in the petroleum exploration.This study utilized the total organic carbon(TOC)content and hydrogen index(HI)to investigate the dominant kerogen type and hydrogen richness for the significance of petroleum generative potential.The Mangahewa coals and carbonaceous shales exhibit an excellent source rocks,with high total organic content(TOC)of more than 22%.The coals and carbonaceous shales were also characterised by Type Ⅱ‒Ⅲ kerogen with Type Ⅲ kerogen,promising oiland gas-prones.The Mangahewa Formation reached the main oil generation,with vitrinite reflectances between 0.53%and 1.01%.Vitrinite reflectance was also used in developing themal models and reveal the transformation(TR)of 10‒50%kerogen to oil during the Late Miocene.The models also showed that the Mangahewa source rock has a significant oil generation and little expulsion competency,with a TR of up to 54%.These findings support the substantial oil-generating potential in the Taranaki Basin's southern graben and can be used as a guide when developing strategies for an oil exploration program.
基金Projects (50934006, 10872218) supported by the National Natural Science Foundation of ChinaProject (2010CB732004) supported by the National Basic Research Program of ChinaProject (kjdb2010-6) supported by Doctoral Candidate Innovation Research Support Program of Science & Technology Review, China
文摘To quantitatively study the location errors induced by deviation of sonic speed, the line and plane location tests were carried out. A broken pencil was simulated as acoustic emission source in the rocks. The line and plane location tests were carried out in the granite rod using two sensors and the cube of marble using four sensors, respectively. To compare the position accuracy between line and plane positions, the line poison test was also carried out on the marble surface. The results show that for line positioning, the maximum error of absolute distance is about 0.8 cm. With the speed difference of 200 m/s, the average value of absolute difference from the position error is about 0.4 cm. For the plane positioning, in the case of the sensor array of 30 cm, the absolute positioning distance is up to 8.7 cm. It can be seen that the sonic speed seriously impacts on the plane positioning accuracy. The plane positioning error is lager than the line positioning error, which means that when the line position can satisfy the need in practical engineering, it is better to use the line position instead of the plane location. The plane positioning error with the diagonal speed is the minimum one.
基金supported by the National Science Foundation of China(NSFC,No.41572131)the China Geology Survey(DD20190103).
文摘Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths <400 m and totally released at the depths >7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective helium source rock is established. We suggest exploring He resources in hydrocarbon basins with granitic basement(or adjacent to granite bodies), high geothermal field, and young active fractures.
文摘The exploration conducted in the Bohai Bay basin, eastern China has demonstrated that the abundant petroleum resources have close affinities to the hydrocarbon kitchen with rich organic matter. A number of oil-generating associations with various characteristics of organic geochemistry and assemblages of multiple reservoir facies are developed due to the multi-center sedimentation, multi-source supply and multi-cycle evolution of filling, which have resulted in the formation of multiple oil and gas accumulation zones of various layers and trap styles. Among them the Paleogene Shahejie Formation is the most important hydrocarbon accumulation combination in the Dongying sag. Heretofore, its proved reserve has reached nearly 1.8×109t, which accounts for more than 90% of the total proved reserves of the Dongying sag. Based on previous studies, more than 600 source rock samples and 186 crude oil samples of the Shahejie Formation, collected from 30 oilfields, have been treated with organic geochemical testing. By combining the sedimentary sequence characteristics and geochemical analysis results, the source rocks of the Shahejie Formation can be divided into three genetic types, i.e. the saline lake facies (the upper ES4, brackish water deep lake facies (the lower ES3) and fresh-water lake facies (the middle ES3), which correspond to the under-filling, balanced-filling and over-filling lake types respectively and represent the three most essential genetic models for source rocks of non-marine fault basins in China. Based on a thorough oil-source correlation, the source rocks of the saline lake and brackish deep lake facies are determined to be the most contributive source rocks in the Dongying sag. Furthermore, by probing into the accumulation of organic matter and hydrocarbon migration pattern, it can be inferred that the hydrocarbons, generated from source rocks of the saline lake facies with relatively low maturity, have mainly accumulated in the uplifted parts of the basin's margin via lateral migration and the reservoirs are dominated by the buried hill and stratigraphic types, while hydrocarbons generated from source rocks of the brackish lake facies are mainly distributed in the basin's center via vertical migration and characterized by forming lithologic reservoirs. Also, the reservoirs located in the transitional belts have complex types and mostly controlled by faults, characterized by block (structural-lithologic) reservoirs, and the crude oils mainly come from source beds of Es31 and Es42 respectively.
文摘There are significant differences in type and distribution between marine source rock and continental source rock. According to the iithology, the Cambrian-Ordovician source rock in the Tarim basin is divided into two types： the carbonate source rock and the mud source rock. The two sets of source rocks are developed mainly in three sets of formations, Lower-Middle Cambrian carbonate source rock and mud source rock, Lower-Middle Ordovician mud source rock and Upper Ordovician lime mud source rock. The stratigraphic and areal distributions of the source rocks are controlled by the altitude and the sedimentary facies respectively. The mud source rock is developed in slope-semi deep sea environment. The source rock developed in the slope sedimentary environment is related with the anoxic environment and the one developed in semi deep sea has a close relationship with the up-flowing sea water. The carbonate source rock is developed mainly in platform slope of highstand systems tract and it is usually intimately associated with the salt rock. The Lower-Middle Cambrian carbonate source rock is developed mainly in the Bachu, Tazhong, Tangguzibasi and Yingmaili areas. The Lower-Middle Cambrian mud source rock is mainly developed in the areas east of the line of Kunan 1-Tadong 1. The Lower-Middle Ordovician mud source rock is developed mainly in the east slope of the Manjiaer depression. The carbonate source rock of Early Ordovician is developed mainly in the platform slope of highstand systems tract, such as the south margin of Tabei, the north slope of Tazhong, the Bachu area and Keping area.
基金jointly funded by the National Science and Technology Major Project of China (Grant No. 2016ZX05003-005)National Natural Science Foundation of China (Grant Nos. 41472100 and 41322017)
文摘Carbonates have been known to act as hydrocarbon source rocks, but their basic geochemical and associated hydrocarbon generation characteristics remain not well understood as they occur with argillaceous source rocks in most cases, and the hydrocarbon generation from each rock type is di cult to distinguish, forming one of puzzling issues within the field of petroleum geology and geochemistry. To improve the understanding of this critical issue, this paper reviews recent advances in this field and provides a summary of key areas that can be studied in future. Results show that carbonate source rocks are generally associated with high-salinity environments with low amounts of terrestrial inputs and low dissolved oxygen contents. Petrographically, these source rocks are dark gray or black, fine-grained, stratified, and contain bacterial and algal bioprecursors along with some other impurities. They generally have low organic matter contents, although these can vary significantly in di erent cases(e.g., the total organic carbon contents of marine and lacustrine carbonate source rocks in China are generally 0.1%–1.0% and 0.4%–4.0%, respectively). These rocks contain type I and type II kerogen, meaning there is a lack of vitrinites. This means that assessment of the maturity of the organic matter in these sediments needs to use non-traditional techniques rather than vitrinite reflectance. In terms of molecular geochemistry, carbonate source rocks have typical characteristics indicative of generally reducing and saline environments and lower organism-dominated bioprecursors of organic matter, e.g., high contents of sulfur compounds, low Pr/Ph ratios, and dominance of n-alkanes. Most of the carbonate source rocks are typically dominated by D-type organic facies in an oxidized shallow water mass, although high-quality source rocks generally contain A-and B-type organic facies in saline lacustrine and marine-reducing environments, respectively. The hydrocarbon generation model for the carbonate source rocks can involve early, middle, and late stages, with a diversity of hydrocarbons within these rocks, which can be aggregated, adsorbed, enclosed within minerals, or present as inclusions. This in turn implies that the large-scale hydrocarbon expulsion from these rocks is reliant on brittle deformation caused by external forces. Finally, a number of aspects of these source rocks remain unclear and need further study, including the e ectiveness of carbonates as hydrocarbon source rocks, bioprecursors, and hydrocarbon generation models of carbonate source rock, and the di erences between marine and lacustrine carbonate source rocks.
基金This study is funded by the Natural Science Research Council of China (973 State Key Research and Development Program 2006CB202308)National Natural Science Foundation of China (Grant No.40973031)
文摘The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.
基金supported by the Major State Basic Research Development Program (973 project, Grant No. 2012CB214803)National Natural Science Foundation of China (Grant No. 41322017)
文摘The Cretaceous is one of the most important stratigraphic intervals for hydrocarbon source rocks. This article summarizes the distribution, formation, and development characteristics of Cretaceous source rocks and associated oil and gas resources in the world and China, aiming at improving the understanding of this hydrocarbon enrichment and at broadening domestic exploration. Outside China, these rocks are generally formed in marine or transgressive environments during both the Upper and Lower Cretaceous. The majority of Cretaceous source rocks are located in the Persian Gulf, Mediterranean, and Gulf Coast of the USA. Kerogen types within these source rocks have distinct spatial distribution characteristics, with high-latitude Boreal Realm, Tethyan Realm and South Gondwana Realm source rocks containing type III, II, II-III kerogens, respectively. Cretaceous source rocks in China can be mainly divided into four zones： Eastern, Central, Northwest, and Qinghai-Tibet Plateau zones. The majority of Chinese source rocks formed in the Early Cretaceous, whereas the most productive source rocks are developed in the Upper Cretaceous, such as those within the Songliao Basin. Most of these basins are formed in lacustrine environments, although some may have been influenced by transgressive events： Cretaceous source rocks are formed in four distinctive ways： 1） during Oceanic Anoxic Events and associated global sea-level rises, 2） in Black Sea-type retention basins, 3） during transgression and 4） during periods of significant terrestrial input. Formation of these source rocks is controlled by four factors： paleoclimate, paleotopography, transgression, and Oceanic Anoxic Events. These four major controlling factors indicate that China＇s hydrocarbon exploration within the Cretaceous should focus on two key areas with extremely low exploration levels, the Qinghai-Tibet Plateau and the southeastern coast of China.
基金supported by the National Natural Science Foundation of China(Nos.40972076 and 41302075)National Technical Key Special Project of China(No.2008ZX05018-001-004)
文摘With the analysis of the element geochemistry characteristics, the ancient lake infor- mation evolution history of the argillaceous source rocks in Lucaogou 0~/~＇~） Formation in San- gonghe area is reconstructed. According to the ancient lake information and total organic matter （TOC） characteristics of argillaceous source rocks, the study section is divided into 6 Subsec- tions. Subsection I mainly developed low-quality source rocks. This is because of the arid climate, high salinity, low lake productivity, unstable preservation conditions in this Subsection. Subsection II mainly developed high-quality source rocks. This is because of the humid climate, low salinity, high lake productivity, stable preservation conditions in this Subsection. Though the paleoclimate was humid and preservation conditions were stable. Lake productivity and the water salinity changed frequently. So Subsection III mainly developed medium-quality source rocks. Because of the humid climate, high lake productivity, medium sedimentary rate and stable preservation conditions, high-quality source rocks were developed in Subsection IV. The preservation conditions were stable, but other ancient lake information changed frequently. Therefore, the quality of the formed source rocks in Subsection V was different. Subsection VI mainly developed high-quality source rocks be- cause of the humid climate, medium sedimentary rate, high lake productivity, low salinity and good preservation conditions. In summary, the ancient lake information parameters and TOC characteris- tics of each Subsection are different from each other.
文摘Petroleum was generated from sedimentary rocks. The world＇s oldest oil source rock so far was found in Proterozoic rocks. Since then, 73% to 81% of the earth＇s surface has been covered with sedimentary rocks. However, only quite a limited area is rich in oil and gas. It is found that source rocks have controlled oil and gas distribution, and they are mainly formed in two systems： （1） river-lake systems and （2） river-gulf systems. Phytoplankton is an important source of kerogen, the blooming of which is strongly dependent on nutrients. Rivers are the major nutrient provider for basins. Rivers around lakes and an undercompensation （where the sedimentation rate is less than the rate of basin subsidence） environment provide favorable conditions for phytoplankton blooming in lakes. Gulfs are usually located at the estuary of big rivers, characterized by restricted current circulation and exchange with the open sea, which benefit maintaining the nutrient density, phytoplankton levels and organic matter preservation. The river-gulf system is the most favorable place for marine source rock development. Most of the world famous marine petroleum-rich provinces are developed from river-gulf systems in geological history, such as the Persian Gulf Basin, Siberian Basin, Caspian Basin, North Sea, Sirte Basin, Nigerian Basin, Kwanza Basin, Gulf of Mexico, Maracaibo Basin and the Eastern Venezuelan Basin.
基金supported by the China Postdoctoral Science Foundation
文摘Carboniferous source rocks identified by drilling in Santanghu （三塘湖） Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositional environment of these samples were also determined through biomarker analysis. Most of the Carboniferous source rocks in Santanghu Basin are characterised by high values of total organic carbon （TOC） content and high extractable organic matter content and hydrocarbon yields, indicating that they are organicrich source rocks with high oil generative potential. The organic matter is predominantly Type I and Type II kerogen with a minor contribution of Type III kerogen, as demonstrated by its pyrolysis parameters and carbon isotope values. According to Ro （%） and T max values, most of the studied samples are at earlyto middle-thermal mature stage; only a few of the samples are at a highly mature stage （past peak oil generation）. The biomarker analysis reveals a dominance of algal/bacterial organic matter input, with a minor contribution of land plant material. Pr/Ph ratio supports a suboxic depositional condition, consistent with a neritic or marine-continental alternating environment proposed by predecessor.
基金funded by the 973 Prophase Special Program of China(NO.2011CB211701)National Natural Science Foundation of China(41172134)CNPC Innovation Foundation (2011D-5006-0101)
文摘The theory of ＂source rock control＂ has evolved from source-rock-control hydrocarbon accumulation, to effective source-rock-control hydrocarbon accumulation, and to high-quality source- rock-control hydrocarbon accumulation. However, there are problems, such as whether high-quality source rocks exist or not？ What high-quality source rocks are, and how to identify them, are yet to be agreed upon. Aimed at this issue of concern to explorationists, and taking the Beier Sag in the Hailaer Basin as an example, this paper defines the high-quality source rocks and the lower limit for evaluation of high-quality source rocks, by using the inflection point on the relationship curve of hydrocarbon （oil） expulsion, which is calculated by the material balance principle, versus total organic carbon （TOC）. The results show that when TOC is low, all source rocks have limited hydrocarbon expulsion and slow growth rate, thus they cannot be high-quality source rocks. However, when TOC rises to some threshold, hydrocarbon expulsion increases significantly with TOC. This inflection point should be the lower limit of high-quality source rocks： those with TOC greater than the inflection-point value are high-quality source rocks. In addition, the lower limit of high-quality source rocks is also related to the type and maturity of organic matters in the source rocks, as well as the mineral components of the source rocks affecting the residual hydrocarbons. Theoretically, the lower limit of high-quality source rocks depends on geological conditions rather than being a constant value. However, for the sake of simplicity and practicability, in this paper TOC=2.0% is regarded as the lower limit of high-quality source rocks. The examination of such standard in the work area indicates that the high-quality source rocks in members K^n2 and K^n~ of the Nantun formation contribute 76% and 82% to oil generation, and 96% and 91% to oil expulsion, respectively. The distribution of high-quality source rocks is also closely related to the distribution of hydrocarbon reservoirs in the region, demonstrating that high-quality source rocks control hydrocarbon accumulation.
基金supported by the National Technological Key Project of China(No.2011ZX05001)
文摘The shale of Yanchang Formation in Upper Triassic is the most important source rock for the Mesozoic petroleum reserviors in Ordos Basin. Chang 7 and Chang 4＋5 members are the major source rock formation. Source rock samples, obtained from 22 cored wells in central Ordos Basin, were geochemically analyzed to determine the organic matter abundance, kerogen type and thermal maturity. Total organic carbon values ranged from 0.36% to 19.10%, 8.09% on average, in- dicating a good source rock potential. In this area, the shale is mature, as indicated by vitrinite re- flectance values. RockoEval data revealed that the samples are dominated by type II kerogen. Com- pare the Chang 7 and Chang 4＋5 members, which suggests that the Chang 7 shale has higher TOC, especially the highest lower Chang 7 members. The abundance of organic matter of Chang 4＋5 and Chang 7 members is both richest in southeast basin. The kerogen type of Chang 4＋5 and upper Chang 7 members is type II~, the counterpart of middle and lower Chang 7 member is type I. During the burial history, the total hydrocarbon-generating quantity of Chang 7 member is much more than that of Chang 4＋5 members.
