Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analys...Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analysis of the 20 crude oils and 40 source rocks from the Turpan Basin, some data have been obtained as follows： carbon preference index and methylphenanthrene index of the Jurassic oils are 1.16-1.45 and 0.28-0.80, and the ααα C29 sterane 20S/（20S＋20R） and C29 sterane ββ/（ββ＋αα） are 0.44-0.51 and 0.4-0.54 respectively, which show the normal maturity of oils; the vitrinite reflectance of the source rocks from the Xishanyao to Badaowan Formations range from 0.47% to 0.97%, which indicate immature to mature thermal evolutionary stage and sufficient conditions for generating mass mature oil. The effect of hydrocarbon expulsion should be considered when studying the source of coal-derived oil by using Biomarkers. Biomarkers in the Jurassic oils from the basin are similar to those in the coals and carbonaceous mudstones, with a strong predominant content of pristane, relatively high ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of low carbon number tricyclic terpanes and C 24 tetracyclic terpane, little gammacerane and C 29 Ts detected, an absolute predominant content of C29 sterane and a relatively high content of diasterane. However, the opposite characteristics are shown in mudstones, with an approximately equal content of pristane and phytane, relatively low ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of high carbon number tricyclic terpanes and a low content of C 24 tetracyclic terpane, peaks of gammacerane and C29 Ts detected obviously and an increasing C27 sterane content. All of these characteristics identify the coals and carbonaceous mudstones as the possible major oil source rocks in this area, and they were formed in the stronger oxidizing environment with shallower water than mudstones.展开更多
The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source ...The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source rocks are widely distributed in the depression, with semi-deep lake and fan delta as the main sedimentary facies, brown oil shale and black gray-dark gray mudstone as the main rocks, and a total thickness of 270-1450 m. The kerogens are mainly of the types I and IIA, and partly of the type IIB and least of the type III. The Ro values range from 0.4%-0.8%, indicating an evolution stage from immature to mature. The maturity of Es4 source rocks is rela-tively high, reaching the early mature stage, but their distribution and thickness are lower than those of Es3. Besides, according to biomarker analysis, it is thought that the source rocks of Es3 and Es4 are characterized by mixed input, and most of the source rocks were formed in the brackish water-saline and strongly oxygen-free environment. Fur-thermore, the Qingshui, Niuxintuo and Chenjia sags are believed to possess greater potential for hydrocarbon gen-eration and expulsion, for they are source rocks with a larger thickness, have higher organic carbon contents, belong to better organic matter types and possess higher maturities.展开更多
So far there has been no common opinion on oil source of the Chepaizi swell in the Junggar Basin. Therefore, it is difficult to determine the pathway system and trend of hydrocarbon migration, and this resulted in dif...So far there has been no common opinion on oil source of the Chepaizi swell in the Junggar Basin. Therefore, it is difficult to determine the pathway system and trend of hydrocarbon migration, and this resulted in difficulties in study of oil-gas accumulation patterns. In this paper, study of nitrogen compounds distribution in oils from Chepaizi was carried out in order to classify source rocks of oils stored in different reservoirs in the study area. Then, migration characteristics of oils from the same source were investigated by using nitrogen compounds parameters. The results of nitrogen compounds in a group of oil/oil sand samples from the same source indicate that the oils trapped in the Chepaizi swell experienced an obvious vertical migration. With increasing migration distance, amounts and indices of carbazoles have a regular changing pattern （in a fine linear relationship）. By using nitrogen compounds techniques, the analyzed oil/oil sand samples of Chepaizi can be classified into two groups. One is the samples stored in reservoir beds of the Cretaceous and Tertiary, and these oils came from mainly Jurassic source rock with a small amount of Cretaceous rock; the other is those stored in the Jurassic, Permian and Carboniferous beds, and they originated from the Permian source. In addition, a sample of oil from an upper Jurassic reservoir （Well Ka 6）, which was generated from Jurassic coal source rock, has a totally different nitrogen compound distribution from those of the above-mentioned two groups of samples, which were generated from mudstone sources. Because of influence from fractionation of oil migration, amounts and ratios of nitrogen compounds with different structures and polarities change regularly with increasing migrating distance, and as a result the samples with the same source follow a good linear relationship in content and ratio, while the oil samples of different sources have obviously different nitrogen compound distribution owing to different organic matter types of their source rocks. These conclusions of oil source study are identical with those obtained by other geochemical bio-markers. Therefore, nitrogen compounds are of great significance in oil type classification and oil/source correlation.展开更多
The Boxing Sag is located in the southwest of Dongying Depression, southern Bohai Bay Basin of East China. It is one of the main petroliferous sags in the Dongying Depression, and has two major source rocks, namely th...The Boxing Sag is located in the southwest of Dongying Depression, southern Bohai Bay Basin of East China. It is one of the main petroliferous sags in the Dongying Depression, and has two major source rocks, namely the upper 4th Member （Es4u） and lower 3rd Member （Es31） shales of Eocene Shahejie Formation, which are the new exploration targets in recent years. In this study, 16 core samples were collected from Es4u and Es31 shales in the Boxing Sag, and the saturate hydrocarbons were analyzed by gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS）, respectively. The results show that Es4u shale has obvious phytane and gammacerane predominance, higher concentration of tricyclic terpanes and regular steranes, and very low concentration of 4- methly steranes; Es31 shale has pristane predominance, lower concentration of tricyclic terpanes, gammacerane and regular steranes, and higher concentration of 4-methly steranes. The Es4u shale can be further divided into two types based on the distribution of n-alkanes in gas chromatograms： normal distribution and double peak pattern. The biomarker characteristics and sedimentary facies distribution show that Es4u shale was deposited in the saline-hypersaline semi-deep （Type A Es4u shale, sag center） to shallow （Type B Es4u shale, sag edge） lacustrine environments, Es31 shale was deposited in the freshwater-brackish semi-deep-deep lacustrine environments, and the former sedimentary facies maps of Es4u and Es31 in the Boxing Sag are further modified.展开更多
The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the central Yangtze area of southern China has a good prospect of shale gas exploration.So far,however,its complicated geological cond...The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the central Yangtze area of southern China has a good prospect of shale gas exploration.So far,however,its complicated geological conditions and shale gas exploration and development potentials have not been understood completely,which affects its exploration achievements.In order to determine the main factors controlling shale gas enrichment in the WufengeLongmaxi Fms in this area,this paper studied the key shale gas enrichment conditions in the black shale there(e.g.sedimentary environments,reservoir development characteristics and preservation conditions)based on single-well comprehensive reservoir evaluation,combined with drilling,logging,core,outcrop and test data.In addition,it was comparedwith the main shale gas blocks in the Sichuan Basin,such as Jiaoshiba and Changning.And the following research results are obtained.First,the organic-rich shale section in this areawas formed during the sedimentation fromWufeng Formation to the third submember of the first member of Longmaxi Formation.It is the deposit of deepwater continental facies,and its thickness is in a range of 15-39 m,presenting a trend of increasing from south to north.Second,the reservoir rocks in the high-quality shale sections are dominated by siliceous shale,and the reservoir porosity is in a range of 1.60-7.44%.The reservoir spaces are dominated by organic pores with good connectivity and high total organic carbon(TOC)content.The organic matter is of a sapropel-sapropel prone hybrid type,with a high thermal evolution degree,better gas bearing property and good fracturability.Third,the Dangyang synclinorium is characterized by better strata preservation,rock occurrence flat,less developed faults and thick and stable roofs and floors,so its shale gas preservation conditions are better.Fourth,different from the Changning and Jiaoshiba Blocks,the central Yangtze area is characterized by great burial depth,large bidirectional stress difference,and low formation pressure coefficient.In conclusion,the WufengeLongmaxi Fms is better in shale gas enrichment conditions and has a potential of further exploration.However,its commercial shale gas development and scale production increase in the future face challenges due to its large stress difference,great burial depth,and lower pressure coefficient.展开更多
基金supported by the National Science and Technology Major Project of China (NO: 2011ZX05007-001-01)
文摘Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analysis of the 20 crude oils and 40 source rocks from the Turpan Basin, some data have been obtained as follows： carbon preference index and methylphenanthrene index of the Jurassic oils are 1.16-1.45 and 0.28-0.80, and the ααα C29 sterane 20S/（20S＋20R） and C29 sterane ββ/（ββ＋αα） are 0.44-0.51 and 0.4-0.54 respectively, which show the normal maturity of oils; the vitrinite reflectance of the source rocks from the Xishanyao to Badaowan Formations range from 0.47% to 0.97%, which indicate immature to mature thermal evolutionary stage and sufficient conditions for generating mass mature oil. The effect of hydrocarbon expulsion should be considered when studying the source of coal-derived oil by using Biomarkers. Biomarkers in the Jurassic oils from the basin are similar to those in the coals and carbonaceous mudstones, with a strong predominant content of pristane, relatively high ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of low carbon number tricyclic terpanes and C 24 tetracyclic terpane, little gammacerane and C 29 Ts detected, an absolute predominant content of C29 sterane and a relatively high content of diasterane. However, the opposite characteristics are shown in mudstones, with an approximately equal content of pristane and phytane, relatively low ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of high carbon number tricyclic terpanes and a low content of C 24 tetracyclic terpane, peaks of gammacerane and C29 Ts detected obviously and an increasing C27 sterane content. All of these characteristics identify the coals and carbonaceous mudstones as the possible major oil source rocks in this area, and they were formed in the stronger oxidizing environment with shallower water than mudstones.
基金supported by the Science and Technology Program of Oil and Gas Exploration,PetroChina Company Ltd.(Grant No.07-01c-01-04)
文摘The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source rocks are widely distributed in the depression, with semi-deep lake and fan delta as the main sedimentary facies, brown oil shale and black gray-dark gray mudstone as the main rocks, and a total thickness of 270-1450 m. The kerogens are mainly of the types I and IIA, and partly of the type IIB and least of the type III. The Ro values range from 0.4%-0.8%, indicating an evolution stage from immature to mature. The maturity of Es4 source rocks is rela-tively high, reaching the early mature stage, but their distribution and thickness are lower than those of Es3. Besides, according to biomarker analysis, it is thought that the source rocks of Es3 and Es4 are characterized by mixed input, and most of the source rocks were formed in the brackish water-saline and strongly oxygen-free environment. Fur-thermore, the Qingshui, Niuxintuo and Chenjia sags are believed to possess greater potential for hydrocarbon gen-eration and expulsion, for they are source rocks with a larger thickness, have higher organic carbon contents, belong to better organic matter types and possess higher maturities.
基金supported by the State 973 Funds(No. 2006CB202308)
文摘So far there has been no common opinion on oil source of the Chepaizi swell in the Junggar Basin. Therefore, it is difficult to determine the pathway system and trend of hydrocarbon migration, and this resulted in difficulties in study of oil-gas accumulation patterns. In this paper, study of nitrogen compounds distribution in oils from Chepaizi was carried out in order to classify source rocks of oils stored in different reservoirs in the study area. Then, migration characteristics of oils from the same source were investigated by using nitrogen compounds parameters. The results of nitrogen compounds in a group of oil/oil sand samples from the same source indicate that the oils trapped in the Chepaizi swell experienced an obvious vertical migration. With increasing migration distance, amounts and indices of carbazoles have a regular changing pattern （in a fine linear relationship）. By using nitrogen compounds techniques, the analyzed oil/oil sand samples of Chepaizi can be classified into two groups. One is the samples stored in reservoir beds of the Cretaceous and Tertiary, and these oils came from mainly Jurassic source rock with a small amount of Cretaceous rock; the other is those stored in the Jurassic, Permian and Carboniferous beds, and they originated from the Permian source. In addition, a sample of oil from an upper Jurassic reservoir （Well Ka 6）, which was generated from Jurassic coal source rock, has a totally different nitrogen compound distribution from those of the above-mentioned two groups of samples, which were generated from mudstone sources. Because of influence from fractionation of oil migration, amounts and ratios of nitrogen compounds with different structures and polarities change regularly with increasing migrating distance, and as a result the samples with the same source follow a good linear relationship in content and ratio, while the oil samples of different sources have obviously different nitrogen compound distribution owing to different organic matter types of their source rocks. These conclusions of oil source study are identical with those obtained by other geochemical bio-markers. Therefore, nitrogen compounds are of great significance in oil type classification and oil/source correlation.
基金financially supported by the Research Institute of Geological Science of Shengli Oilfield Company Limited and by the State Key Laboratory of Petroleum Resources and Prospecting (No. prp2009-02)
文摘The Boxing Sag is located in the southwest of Dongying Depression, southern Bohai Bay Basin of East China. It is one of the main petroliferous sags in the Dongying Depression, and has two major source rocks, namely the upper 4th Member （Es4u） and lower 3rd Member （Es31） shales of Eocene Shahejie Formation, which are the new exploration targets in recent years. In this study, 16 core samples were collected from Es4u and Es31 shales in the Boxing Sag, and the saturate hydrocarbons were analyzed by gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS）, respectively. The results show that Es4u shale has obvious phytane and gammacerane predominance, higher concentration of tricyclic terpanes and regular steranes, and very low concentration of 4- methly steranes; Es31 shale has pristane predominance, lower concentration of tricyclic terpanes, gammacerane and regular steranes, and higher concentration of 4-methly steranes. The Es4u shale can be further divided into two types based on the distribution of n-alkanes in gas chromatograms： normal distribution and double peak pattern. The biomarker characteristics and sedimentary facies distribution show that Es4u shale was deposited in the saline-hypersaline semi-deep （Type A Es4u shale, sag center） to shallow （Type B Es4u shale, sag edge） lacustrine environments, Es31 shale was deposited in the freshwater-brackish semi-deep-deep lacustrine environments, and the former sedimentary facies maps of Es4u and Es31 in the Boxing Sag are further modified.
基金supported by the National Science and Technology Major Project“Shale Gas Enrichment Law and Key Target Evaluation in Sichuan Basin and Periphery”(No.2017ZX05035-001)Hubei Province Colleges and Universities Excellent Young and Middle-aged Science and Technology Innovation Team Project“Shale Gas Formation Mechanism and Reservoir Evaluation”(No.T201905)+1 种基金Hubei Provincial Natural Science Foundation project“Study on the temporal and spatial distribution and paleogeography of organic-rich shale in the Wufeng-Longmaxi Formation in Western Hubei”(No.2018CFB330)“Research on the Lower Paleozoic High in Southwest Hubei-Development and evolution of organic pores in overmature marine shale”(No.2016CFB601).
文摘The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the central Yangtze area of southern China has a good prospect of shale gas exploration.So far,however,its complicated geological conditions and shale gas exploration and development potentials have not been understood completely,which affects its exploration achievements.In order to determine the main factors controlling shale gas enrichment in the WufengeLongmaxi Fms in this area,this paper studied the key shale gas enrichment conditions in the black shale there(e.g.sedimentary environments,reservoir development characteristics and preservation conditions)based on single-well comprehensive reservoir evaluation,combined with drilling,logging,core,outcrop and test data.In addition,it was comparedwith the main shale gas blocks in the Sichuan Basin,such as Jiaoshiba and Changning.And the following research results are obtained.First,the organic-rich shale section in this areawas formed during the sedimentation fromWufeng Formation to the third submember of the first member of Longmaxi Formation.It is the deposit of deepwater continental facies,and its thickness is in a range of 15-39 m,presenting a trend of increasing from south to north.Second,the reservoir rocks in the high-quality shale sections are dominated by siliceous shale,and the reservoir porosity is in a range of 1.60-7.44%.The reservoir spaces are dominated by organic pores with good connectivity and high total organic carbon(TOC)content.The organic matter is of a sapropel-sapropel prone hybrid type,with a high thermal evolution degree,better gas bearing property and good fracturability.Third,the Dangyang synclinorium is characterized by better strata preservation,rock occurrence flat,less developed faults and thick and stable roofs and floors,so its shale gas preservation conditions are better.Fourth,different from the Changning and Jiaoshiba Blocks,the central Yangtze area is characterized by great burial depth,large bidirectional stress difference,and low formation pressure coefficient.In conclusion,the WufengeLongmaxi Fms is better in shale gas enrichment conditions and has a potential of further exploration.However,its commercial shale gas development and scale production increase in the future face challenges due to its large stress difference,great burial depth,and lower pressure coefficient.
