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| 1 | Isotopic evidence of TSR origin for natural gas bearing high H_2S contents within the Feixianguan Formation of the northeastern Sichuan Basin, southwestern China显示文摘The northeastern area of Sichuan Basin, southwestern China, is the area with the maximal reserve of natural gas containing higher hydrogen sulphide (H2S) that has been found among the petroliferous basins of China, with the proven and controlled gas reserve of more than 200 billion cubic meters. These gas pools, with higher H2S contents averaging 9%, some 17%, are mainly distributed on structural belts of Dukouhe, Tieshanpo, Luojiazhai, Puguang, etc., while the oolitic-shoal dolomite of the Triassic Feixianguan Fm. (T1f) is the reservoir. Although many scholars regard the plentiful accumulation of H2S within the deep carbonate reservoir as the re-sult of Thermochemical Sulfate Reduction (TSR), however, the process of TSR as well as its residual geological and geochemical evidence is still not quite clear. Based on the carbon iso-topic analysis of carbonate strata and secondary calcite, etc., together with the analysis of sulfur isotopes within H2S, sulphur, gypsum, iron pyrites, etc., as well as other aspects including the natural gas composition, carbon isotopes of hydrocarbons reservoir petrology, etc., it has been proved that the above natural gas is a product of TSR. The H2S, sulphur and calcite result from the participation of TSR reactions by hydrocarbon gas. During the process for hydrocarbons be-ing consumed due to TSR, the carbons within the hydrocarbon gas participate in the reactions and finally are transferred into the secondary calcite, and become the carbon source of secon-dary calcite, consequently causing the carbon isotopes of the secondary calcite to be lower (?18.2‰). As for both the intermediate product of TSR, i.e. sulfur, and its final products, i.e. H2S and iron pyrites, their sulfur elements are all sourced from the sulfate within the Feixianguan Fm. During the fractional processes of sulfur isotopes, the bond energy leads to the 32S being re-leased firstly, and the earlier it is released, the lower δ 34S values for the generated sulphide (H2S) or sulfur will be. However, for the anhydrite that participates in reactions, the higher the reaction degree, the more 32S is released, while the less 32S remains and the more δ 34S is increased. The testing results have proved the process of the dynamic fractionation of sulfur isotopes. | ZHU Guangyou ZHANG Shuichang LIANG Yingbo DAI Jinxing LI Jian | 2005 | Science China Earth Sciences2005,48,11: | 58 |
| 2 | Discussion of gas enrichment mechanism and natural gas origin in marine sedimentary basin,China显示文摘There are abundant natural gas resources in Chinese marine sedimentary basin. The exploration hot shots of natural gas are the Palaeozoic marine strata here in recent years, and several large scale gas fields have been discovered. Chinese Palaeozoic high-post matured and coal measure hydrocarbon source rocks are mainly prone to gas generation in the present. This research considered that gas source rocks and TSR are the key cause of gas enrichment of marine strata. High-quality argillaceous and coal measure hydrocarbon rocks are distributed widely in the Palaeozoic marine strata, which have been in highly matured phase in the present. The argillaceous source rock generally contains various sulfates that could accelerate crude oil cracking to gas for TSR occurrence, and coal measure source rock mainly generates gas, so Chinese marine basin gives priority to accumulating gas. Marine strata have not founded oil reservoirs in the Sichuan Basin and Ordos Basin, and they consist mainly of dry gas. Marine natural gases are the mixed gases of oil cracking gas and coal-formed gas in a general way, oil cracking gases contain usually some H2S and CO2. Hydrocarbon carbon isotopes are very complicated, and methane and ethane isotopic values bear apparent reversal caused by thermal evolution and mixing among different genetic types of natural gas. Coal-formed gases are the main component of Chinese marine natural gas. The Upper Permian of the Sichuan Basin and the Carboniferous-Permian of the Ordos Basin coal measure hydrocarbon source rock present large hydrocarbon generation potential, which are the prospecting highlight of marine natural gas hereafter. Oil cracking gas exploration will be paid much attention to in the Tarim Basin because of the lack of coal measure hydrocarbon source rock. | ZHU GuangYou ZHAO WenZhi ZHANG ShuiChang LIANG YingBo WANG ZhengJun | 2007 | Chinese Science Bulletin2007,52,A01: | 41 |
| 3 | Origins of High H_2S-bearing Natural Gas in China显示文摘Natural gas containing hydrogen sulphide (H2S) has been found in several petroliferous basins in China, such as the Sichuan Basin, Bohai Bay Basin, Ordos Basin, Tarim Basin, etc. Natural gas with higher H2S contents (H2S >5 % mol.) is mostly distributed in both the gas reservoirs of Dukouhe, Luojiazhai, Puguang and Tieshanpo, which belong to the Triassic Feixianguan Formation in the northeastern Sichuan Basin and those of the Kongdian-Shahejie formations in the northeastern Jinxian Sag of the Jizhong Depression, Bohai Bay Basin. In the Sichuan Basin, the H2S contents of natural gas average over 9% and some can be 17 %, while those of the Bohai Bay Basin range from 40 % to 92 %, being then one of the gas reservoirs with the highest H2S contents in the world. Based on detailed observation and sample analysis results of a total 5000 m of core from over 70 wells in the above-mentioned two basins, especially sulfur isotopic analysis of gypsum, brimstone, pyrite and natural gas, also with integrated study of the geochemical characteristics of hydrocarbons, it is thought that the natural gas with high H2S contents resulted from thermochemical sulfate reduction (TSR) reactions. Among them, the natural gas in the Feixianguan Formation resulted from TSR reactions participated by hydrocarbon gas, while that in the Zhaolanzhuang of the Jinxian Sag being the product of TSR participated by crude oil. During the consumption process of hydrocarbons due to TSR, the heavy hydrocarbons were apt to react with sulfate, which accordingly resulted in the dry coefficient of natural gas increasing and the carbon isotopes becoming heavier. | ZHU Guangyou ZHANG Shuichang LIANG Yingbo DAI Jinxing LI Jian | 2005 | Acta Geologica Sinica(English Edition)2005,79,5: | 36 |
| 4 | Hydrocarbon sources and stages of reservoir formation in Kuqa depression, Tarim Basin显示文摘Kuqa depression bears not only plenty ofnatural gas, but also a large amount of condensate and smallquantity of crude oil. Based on the geochemical correlationbetween the Jurassic and Triassic terrestrial hydrocarbonsource rock, this paper confirms that the natural gas in Kuqadepression belongs to coal-type gas and the main gas sourcerock is attributed to the middle to lower Jurassic coal seriesformation, while the main oil source rock is the upper Tri-assic lacustrine mudstone. The authors indicated that Kuqadepression was slowly subsided in Mesozoic, but rapidlywent down in Late Tertiary, which made the Jurassic andTriassic source rock suddenly deep-buried and rapidlyevolved to high and over-mature phase since 5 Ma. TheTriassic source rock is postponed to the Early Miocene dur-ing 23-12 Ma when entering the oil-generating peak, whilethe Jurassic is suspended to the latest 5 Ma, especially since2.5 Ma to the dry gas-generating period, which is one of thecharacteristics of the source rock thermal evolution in Kuqadepression. This paper presents a two-stage trapping andlate gas trapping model in Kuqa depression whose charac-teristics are: The main oil and gas reservoirs have differentsources. The oil reservoir is formed early while the gas res-ervoir is formed lately. During the early stage, it, mainly asoil, takes long distance lateral migration, while in the laterstage, it, mainly as gas, takes the vertical migration and alsohas lateral migration. The trap formed in different time onthe south and north sides of the depression and evolved intoa distributional pattern with oil in the south part and gas inthe north, also oil on the outer ring and gas on the inner ring.This paper points out that the late trapping of the naturalgas in Kuqa depression is favorable for the preservation oflarge gas fields. | LIANG Digang ZHANG Shuichang ZHAO Mengjun WANG Feiyu | 2002 | Chinese Science Bulletin2002,47,S1: | 34 |
| 5 | Relationship between the later strong gas-charging and the improvement of the reservoir capacity in deep Ordovician carbonate reservoir in Tazhong area, Tarim Basin显示文摘Some large-scale oil-gas fields have recently been discovered in marine carbonate in China, especially the significant discoveries in deep reservoir that reveals a favorable exploration prospect. Tazhong area is the first-order tectonic unit in Tarim Basin, where there are nearly trillion cubic meters of natural gas resources in the Ordovician limestone reef flat complex in Lianglitage Formation. The reservoir is shelf edge reef flat complex, characterized by ultra-low porosity, low permeability and strong heterogeneous, with a current burial depth of 4500―6500 m. Studies find that the formation and distribution of deep reservoir of the Lianglitage Formation were controlled not only by the early high-energy sedimentary facies and corrosion, but the fracture network formed by the strong gas-charging process since the Himalayan epoch, which played an important role in optimizing and improving reservoir properties. This paper discusses the relationship between the strong later gas-charging and the improvement of the reservoir capacity in deep Ordovician carbonate reservoir, and also builts the corresponding mechanisms and modes, which is favorable for the prediction and evaluation of the advantageous exploration targets. | ZHAO WenZhi ZHU GuangYou ZHANG ShuiChang ZHAO XueFeng SUN YuShan WANG HongJun YANG HaiJun HAN JianFa | 2009 | Chinese Science Bulletin2009,54,17: | 31 |
| 6 | Molecular fossils and oil-source rock correlations in Tarim Basin, NW China显示文摘The distribution of 'molecular fossils' (bio-markers) of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed andare used as the fingerprints for the oil-source rock correla-tion. Having been affected by maturation, migration, phasefractionation and biodegradation, not any molecular fossilsrelated to source and environment can be used as the finger-prints for oil-source rock correlation. Some special bio-markers widely existed in the extracts from Cambrian andOrdovician rocks in the Tarim Basin and showed obviousdifference in each stratum, including dinosteranes (C30),4-methyl-24-ethyl-cholestanes (C30) and their aromatizedsteroids, C24-norcholestanes and C28 steranes originated fromdinoflagellates and diatom. Few oils such as the heavy oildrilled in the Cambrian reservoir from Tadong 2 well (TD2)correlated well with the extracts from the Cambrian. Theamazing similarity of the relative contents of these com-pounds between the marine oils produced in Tazhong andTabei uplifts and the extracts from the Upper Ordoviciansuggests that the Middle-Upper Ordovician is the very likelymain source for the marine oils. | ZHANG Shuichang LIANG Digang LI Maowen XIAO Zhongyao HE Zhonghua | 2002 | Chinese Science Bulletin2002,47,S1: | 25 |
| 7 | Fundamental geological elements for the occurrence of Chinese marine oil and gas accumulations显示文摘The Paleozoic strata in the Tarim Basin, Sichuan Basin and Ordos Basin are the major targets for marine petroleum exploration, with developed high quality hydrocarbon, mainly argillite. The deep burial of these source rocks suggests that they mainly develop gas instead of oil. But different maturities of organic matter may lead to different hydrocarbon facies. Through thermochemical sulfate reduction (TSR), the hydrocarbon in the carbonate rocks may undergo a process of pyrolytic cracking and be catalyzed into gases. The marine reservoirs mainly consist of carbonate and clastic rocks, and the former is controlled by sedimentary facies, dolomitization, solution, TSR and cracking. The multiphase tectonic cycling develops multiple source-reservoir-cap combinations and diversified types of traps and reservoirs, featuring multiphase reservoir formation, mainly late-phase formation or consolidation. Palaeo-uplifts play a controlling role in hydrocarbon accumulation. Differences in major source rocks in the three basins lead to different locations of oil-gas accumulation layers, different types and patterns of reservoirs and different features of reservoir formation. | ZHANG ShuiChang LIANG DiGang ZHU GuangYou ZHANG XingYang ZHANG BaoMin CHEN JianPing ZHANG Bin | 2007 | Chinese Science Bulletin2007,52,A01: | 22 |
| 8 | Natural gas origins of large and medium-scale gas fields in China sedimentary basins显示文摘China sedimentary basins present abundant natural gas resource thanks to its unique geological settings.Marine highly-matured hydrocarbon source rocks,widespread coal-measure strata and low temperature Quaternary saline strata,etc.,indicate the wide foreground of China natural gas resources. Up to now,most of the petroliferous basins have been discovered to have wholesale natural gas accumulation from Precambrian,Paleozoic,Mesozoic to Cenozoic in the east,the central,the west and the coast of China.These large and medium-scale gas reservoirs are mainly composed of hydrocarbon gas with big dry coefficient,tiny non-hydrocarbon,wide carbon isotope distribution and varying origin types,the hydrocarbon gas includes coal-formed gas,oil-formed gas,biogenic gas and inorganic gas, etc.Coal-formed gas is the main type of China natural gas resources,in particular several explored large-scale gas fields(>100 billion cubic meter)of Kela 2,Sulige and Daniudi,etc.,they all belong to coal-formed gas fields or the gas fields consisting mostly of coal-formed gas.Oil-formed gas is also abundant in China marine basins,for example marine natural gas of Sichuan Basin generated from crude oil cracking gas.Primary and secondary biogenic gas fields were discovered respectively in the Qaidam Basin and Western Slope of Songliao Basin.In addition,inorganic gases are mainly distributed in the eastern China,in particular the Songliao Basin with abundant carbon dioxide accumulation,indicating that the eastern China present large exploration potential of inorganic gas. | ZHANG ShuiChang &ZHU GuangYou Research Center of Research Institutes of PetroChina Exploration and Development,Beijing 100083,China | 2008 | Science China Earth Sciences2008,51,S1: | 21 |
| 9 | Oil cracking: An important way for highly efficient gen- eration of gas from marine source rock kitchen显示文摘The potentials of gas generation by kerogen in the late period and by crude oil cracking are closely related to the origin of natural gas in the high- to over mature ma- rine area and their exploration perspectives. The carbon structure of kerogens, with different types and at different evolution stages, have been experimentally studied using the high magnetic field solid 13C nuclear magnetic resonance technique in order to determine the oil and gas potential of kerogens. Results show that the contents of gas potential carbon(GPC) of types I, II, III kerogens at the high- to over mature stage are very low, indicating their weak gas-generating capacity and limited gas production; however, the content of oil potential carbon(OPC) of the low mature type I kerogen is much higher, implying that a large amount of crude oil generated during the oil-generating period will be the material for later gas generation by oil cracking. The kinetic experiment of gas generation by crude oil cracking shows that, when the temperature is about 160℃(Ro=1.6%), the crude oil will start to produce large amounts of gas; the temperature range for major gas generation of crude oil is higher than that of the kerogens, and the gas production is 2 to 4 times higher than that of kerogens. The natural gas de- rived from oil cracking (called oil-cracked gas) is much abundant in methyl hexamethylene, which is quite different from the natural gas produced by thermal degradation of kerogens (named kerogen degradation gas) at high- to over mature stage. | ZHAO Wenzhi WANG Zhaoyun ZHANG Shuichang WANG Hongjun WANG Yunpeng | 2005 | Chinese Science Bulletin2005,50,22: | 18 |
| 10 | TSR promotes the formation of oil-cracking gases: Evidence from simulation experiments显示文摘TSR is an interaction between sulfate and hydrocarbons, occurring widely in carbonate reservoirs. Because this process can produce a large amount of noxious acidic gases like H2S, it has drawn seri- ous concern recently. This paper reports an experiment that simulated an interaction between different minerals and hydrocarbon fluids under different temperature and time using a confined gold-tube system. The results showed that the main mineral that initiates TSR is MgSO4, and adding a certain amount of NaCl into the reactive system can also promote TSR and yield more H2S. The H2S produced in TSR is an important incentive for the continuous oxidative degradation of crude oils. For instance, the yield of oil-cracking gases affected by TSR was twice of that not affected by TSR while the yield of TSR-affected methane was even higher, up to three times of that unaffected by TSR. The carbon iso- topes of wet gases also became heavier. All of the above illustrated that TSR obviously motivates the oxidative degradation of crude oils, which makes the gaseous hydrocarbon generation sooner and increases the gas dryness as well. The study on this process is important for understanding the TSR mechanism and the mechanism of natural gas generation in marine strata. | ZHANG ShuiChang SHUAI YanHua ZHU GuangYou | 2008 | Science China Earth Sciences2008,51,3: | 18 |
| 11 | Discrimination of abiogenic and biogenic alkane gases显示文摘We have combined the analytical data of the carbon isotope distribution pattern, R/Ra and CH4/3He values of abiogenic and biogenic (referring to the thermogenic and bacterial or microbial) alkane gases in China with those of alkane gases from USA, Russia, Germany, Australia and other countries. Four discrimination criteria are derived from this comparative study: 1) Carbon isotopic composition is generally greater than -30‰ for abiogenic methane and less than -30‰ for biogenic methane; 2) Abiogenic alkane gases have a carbon isotopic reversal trend (δ 13C1> δ 13C2> δ 13C3> δ 13C4) with δ 13C1>-30‰ in general; 3) Gases with R/Ra >0.5 and δ 13C11 δ 13C2>0 are of abiogenic origin; 4) Gases (meth- ane) with CH4/3He≤106 are of abiogenic origin, whereas gases with CH4/3He≥1011 are of biogenic origin. | DAI JinXing ZOU CaiNeng ZHANG ShuiChang LI Jian NI YunYan HU GuoYi LUO Xia TAO ShiZhen ZHU GuangYou MI JingKui LI ZhiSheng HU AnPing YANG Chun ZHOU QingHua SHUAI YanHua ZHANG Ying MA ChengHua | 2008 | Science China Earth Sciences2008,51,12: | 17 |
| 12 | The controlling factors and distribution prediction of H_2S formation in marine carbonate gas reservoir,China显示文摘Generally, there are some anhydrites in carbonate reservoir, as H2S is also familiar in carbonate oil and gas reservoirs. Nowadays, natural gas with high H2S concentration is usually considered as TSR origin, so there is close relationship between H2S and anhydrite. On the contrary, some carbonate rocks with anhydrite do not contain H2S. Recently, researches show that H2S is only a necessary condition of H2S formation. The reservoir porosity, sulfate ion content within formation water, reservoir temperature, oil/gas and water interface, hydrocarbon and some elements of reservoir rock have great controlling effects on the TSR occurrence. TSR deoxidizes hydrocarbon into the acidic gas such as H2S and CO2, and the H2S formation is controlled by TSR occurrence, so the relationship among reaction room, the contact chance of sulfate ion and hydrocarbon, the reservoir temperature has great influence on the TSR reaction. H2S has relatively active chemical quality, so it is still controlled by the content of heavy metal ion. Good conditions of TSR reaction and H2S preservation are the prerequisite of H2S distribution prediction. This paper builds a predictive model based on the characteristic of natural gas reservoir with high H2S-bearing. In the porosity reservoir with anhydrite, the formation water is rich in sulfate and poor in heavy metal ion. Oil and gas fill and accumulate in the gas reservoir with good preservation conditions, and they suffered high temperature later, which indicates the profitable area of natural gas with high H2S-bearing. | ZHU GuangYou ZHANG ShuiChang LIANG YingBo | 2007 | Chinese Science Bulletin2007,52,A01: | 17 |
| 13 | Formation Mechanism and Controlling Factors of Natural Gas Reservoirs of the Jialingjiang Formation in the East Sichuan Basin显示文摘The Lower Triassic Jialingjiang Formation reservoirs are distributed widely in the East Sichuan Basin,which are composed mainly of fractured reservoirs.However,natural gas with high concentration of H_2S,ranging from 4% to 7%,was discovered in the Woionghe Gas pool consisting primarily of porous reservoirs,while the other over 20 fractured gas reservoirs have comparatively low,tiny and even no H_2S within natural gases.Researches have proved the H_2S of the above reservoirs are all from the TSR origin.Most of the Jialingjiang Formation natural gases are mainly generated from Lower Permian carbonate rocks,the Wolonghe gas pool's natural gases are from the Upper Permian Longtan Formation,and the natural gases of the Huangcaoxia and Fuchengzhai gas pools are all from Lower Silurian mudstone.The formation of H_2S is controlled by the characteristics and temperature of reservoirs,and is not necessarily related with gas sources.The Jialingjiang Formation in East Sichuan is buried deeply and its reservoir temperature has ever attained the condition of the TSR reaction.Due to poor reservoir potential,most of the gas pools do not have enough room for hydrocarbon reaction except for the Wolonghe gas pool,and thus natural gases with high H_2S concentration are difficult to be generated abundantly.The south part of East Sichuan did not generate natural gases with high H_2S concentration because the reservoir was buried relatively shallow,and did not suffer high temperature.Hence,while predicting the distribution of H_2S,the characteristics and temperature of reservoirs are the necessary factors to be considerd besides the existence of anhydrite. | ZHU Guangyou ZHANG Shuichang LIANG Yingbo ZHOU Guoyuan WANG Zhengjun | 2007 | Acta Geologica Sinica(English Edition)2007,81,5: | 16 |
| 14 | The genesis of H_2S in the Weiyuan Gas Field, Sichuan Basin and its evidence显示文摘The Sinian Dengying Formation gas pool in Weiyuan is the oldest large-scale sulfur-bearing gas field in China, which has a H2S content ranging from 0.8% to 1.4%. The Cambrian Xixiangchi Formation gas pool discovered recently above the Dengying Formation contains gas geochemical behaviors similar to those of Dengying Formation but different in sulfur isotopes of H2S. Investigations show that though these two Sinian and Cambrian gas pools are separate ones, they share the same Cambrian source rock. The higher dry coefficient, heavier carbon isotopes, sulfur isotopes of sulfide, lower filling of gas pools, formation water characteristics, reservoir properties and H2S distribution, indicate that H2S in both the Sinian and Cambrian gas pools originates from TSR. The sulfur isotopes of sulfates have shown that H2S was formed in respective pools, namely hydrocarbons charged into the pools reacted with the Dengying Formation and the Xixiangchi Formation gypsum (TSR), respectively, to form H2S. Compared with sulfur isotopes of sulfates in each pool, δ34S values of H2S are 8‰ lighter for the Dengying Formation pool and 12‰ lighter for the Xixiangchi Formation pool, respectively, which is attributed to the difference in temperatures of TSR occurrence. The reservoir temperature of the Xixiangchi Formation pool is about 40℃ lower than that of the Dengying Formation pool. Temperature plays a controlling role in both the sulfur isotopic fractionation and amounts of H2S generation during TSR. | ZHU GuangYou ZHANG ShuiChang LIANG YingBo LI QiRong | 2007 | Chinese Science Bulletin2007,52,10: | 13 |
| 15 | Analysis on forming conditions of deep marine reservoirs and their concentration belts in superimposed basins in China显示文摘By taking the Tarim Basin, Sichuan Basin and Ordos Basin as examples, the conditions for deep marine reservoir formation were illustrated in three aspects listed below: late-stage superimposition style, burial history and structural deformation of the marine stratigraphic system. The burial history of marine source rocks can be divided into three types, i.e., type I, type II and type III, which are obviously different from the case with present hydrocarbon phases in terms of hydrocarbon generation and petroleum-reservoir formation. Based on evolution history, the structural belts in the marine stratigraphic sequence can also be divided into four types, i.e. earlier normal fault-later fault-fold type, earlier uplift-later fault-fold type, earlier uplift-later flattened slope type, and earlier depression-later thrust type. In this paper, a successive gas generation model was proposed, and it was particularly pointed out that coupling of geothermal field annealing evolution and tectonic subsidence and late gas generation from dispersed liquid hydrocarbon in highly matured to over-matured source rocks are key factors for formation of marine petroleum reservoirs. The geological conditions for formation of high-grade reservoirs in deep marine system, covering early hydrocarbon injection, deep denudation and buried dolomitization, were summarized. It was finally concluded that three major structural belts, i.e. paleo-uplift belt characterized by composite hydrocarbon accumulation, paleo-fault belt and high-energy sedimentary facies belt, were involved in marine hydrocarbon accumulation. | ZHAO WenZhi WANG ZeCheng ZHANG ShuiChang WANG HongJun | 2007 | Chinese Science Bulletin2007,52,A01: | 13 |
| 16 | A discussion on gas sources of the Feixianguan Formation H_2S-rich giant gas fields in the northeastern Sichuan Basin显示文摘In recent years several H2S-rich oolite giant gas pools have been discovered in the Lower Triassic Feixianguan Formation of the northeastern Sichuan basin, and their explored gas reserves have been over 5000×108 m3. However, gas sources remain unsolved due to multiple source horizons with high maturity in this area and TSR alterations. By integrating analytical data of natural gas samples with conprehensive investigations on many factors, such as oil-gas geology, distribution and evolution of source rocks, charging and adjustment of gas pools, mixture of natural gases and secondery alterations, the present study concluded that the dominant source for the Feixianguan Fr. gas pools is the Permian Longtan Fr. source rock and secondly the Silurian Longmaxi Fr. source rock. Natural gases from the various gas pools differ genetically due to the matching diversity of seal configurations with phases of hydrocarbon generation and expulsion by different source rocks, among which natural gases in Puguang Gasfield are dominated by the trapped gas generated from the Longtan Fr. source rock and commingled with the gas cracked from the Silurian crude oil, while those in Dukouhe, Tieshangpo and Luojiazhai Gasfields are composed mainly of the Silurian oil-cracking gas and commingled with the natural gas derived from the Longtan Fr. source rock. | ZHANG ShuiChang ZHU GuangYou CHEN JianPing LIANG YingBo | 2007 | Chinese Science Bulletin2007,52,A01: | 12 |
| 17 | The Xiamaling oil shale generated through Rhodophyta over 800 Ma ago显示文摘A suit of oil shales, predominated by black argillaceous silicalite and finely laminated black-brown shale, has been discovered in a set of carbonaceous-siliceous mudstone formations (350 m in thickness) in the third member of Xiamaling Formation of the Upper Proterozoic Qingbaikou Series (900―873 MaBP), Xiahuayuan, Hebei Province, China. The oil shale, combustible with strong bitumen odour, has su- per-high TOC contents ranging from 21.4% to 22.9%, bitumen “A” contents from 0.58% to 0.88% and oil length from 5.29% to 10.57%. The ultrathin section observation of the shale and the identification of its kerogen demonstrate that its hydrocarbon-generative parent material is mainly benthonic Rhodophyta whose specific tetrasporangia are legible and abundant. It is rarely reported in the literature that such a hydrocarbon-generative parent material, composed mainly of Rhodophyta and with extraordinarily high contents of TOC and bitumen “A”, developed into a set of high-quality source rocks. The extracts of the oil shale are characteristic of richness in 17α(H)-diahopanes and n-alkyl tricyclic terpenoids but low in steranes. Such a biomarker feature is obviously different from that of the extracts from other Proterozoic marine carbonate source rocks of the studied area. Since the biological constitution of this oil shale is rather simple, it is clear that these biomarkers most likely represent to certain extent the specific mo- lecular constitutions of the benthonic Rhodophyta identified in the ultrathin sections of the samples. Studies on its lithologic association and depositional sequences suggest that this suit of the carbona- ceous-siliceous mudstone formation, which contains oil shales, was probably developed in an under- compensation deep-bay environment when a maximum transgression occurred during the formation of the third member of Xiamaling Formation. The high concentration of SiO2 in this organic-rich rock and the positive correlation between TOC and some trace elements such as P, Cu, Ni, W and Mo indicate that this suit of rocks was affected by activities of bottom thermal currents as deposited. | ZHANG ShuiChang ZHANG BaoMin BIAN LiZeng JIN ZhiJun WANG DaRui CHEN JianFa | 2007 | Science China Earth Sciences2007,50,4: | 12 |
| 18 | Geochemical features and genesis of the natural gas and bitumen in paleo-oil reservoirs of Nanpanjiang Basin, China显示文摘Bitumen from the Nanpanjiang Basin occurs mainly in the Middle Devonian and Upper Permian reef limestone paleo-oil reservoirs and reserves primarily in holes and fractures and secondarily in minor matrix pores and bio-cavities. N2 is the main component of the natural gas and is often associated with pyrobitumen in paleo-oil reservoirs. The present study shows that the bitumen in paleo-oil reservoirs was sourced from the Middle Devonian argillaceous source rock and belongs to pyrobitumen by crude oil cracking under high temperature and pressure. But the natural gas with high content of N2 is neither an oil-cracked gas nor a coal-formed gas generated from the Upper Permian Longtan Formation source rock, instead it is a kerogen-cracked gas generated at the late stage from the Middle Devonian argilla- ceous source rock. The crude oil in paleo-oil reservoirs completely cracked into pyrobitumen and methane gas by the agency of hugely thick Triassic deposits. After that, the abnormal high pressure of methane gas reservoirs was completely destroyed due to the erosion of 2000--4500-m-thick Triassic strata. But the kerogen-cracked gas with normal pressure was preserved under the relatively sealed condition and became the main body of the gas shows. | ZHAO MengJun ZHANG ShuiChang ZHAO Lin DA Jiang | 2007 | Science China Earth Sciences2007,50,5: | 11 |
| 19 | Molecular geochemical characteristics of gas source rocks from the Upper Triassic Xujiahe Formation indicate transgression events in the Sichuan Basin显示文摘The geochemical characteristics of saturated and aromatic hydrocarbons from different formations and lithologies provide ob-vious evidence for transgressions that occurred during Upper Triassic Xujiahe stage in Sichuan Basin with a great impact on the source input and depositional environment.A clear dual peak distribution for normal alkanes and obvious abundant com-pounds sourced from bacteria and algae in whole oil gas chromatogram indicates the abundance of lower organisms input.The ratio of Pr/Ph is low,ranging from 0.33 to 0.86 with an average of 0.60,quite different from Pr/Ph >2.0 for coal measures in swamp environment,representing source rocks from saline lake or marine facies.In the gas source rocks extracts,abundant β-carotane,-carotane,and their degradated series were detected in the whole oil chromatogram,indicating a reducing envi-ronment.The concentrations of methyl steranes and dinosteranes are high.The content of polycyclic aromatic sulfur heterocy-cles(PASH) is relatively higher in aromatic fraction and the assemblage of fluorene,dibenzofuran,and dibenzothiophene is different from the typical saline lake and the regular swamp facies source rocks,manifesting the transgression effects on gas source rocks. | ZHANG Min HUANG GuangHui LI HongBo HU GuoYi ZHANG ShuiChang | 2012 | Science China Earth Sciences2012,55,8: | 10 |
| 20 | The distribution of the oil derived from Cambrian source rocks in Lunnan area,the Tarim Basin,China显示文摘There are great differences in biomarks between Cambrian oil and Middle-Upper Ordovician oil. In this stuty, the authors analyzed 40 oils found in Lunnan area by GC-MS and calculated the content of Cambrian oil in the 40 oils according to the steroid indexes of typical oil mixture and match experiment. The results show that it is a general phenomenon in Ordovician reservoir that the oil derived from Cambrian source rock mixed with the oil derived from Middle-Upper Ordovician source rock in Lunnan area, the mixture degree of the two oils is lower in Carboniferous reservoir than in Ordovician reservoir, and the oils kept in Triassic reservoir have single source, Middle-Upper Ordovician source rock. The mixture oils mainly composed of Cambrian oil (>50%) distributed in Sangtamu fault zone, and the oils found in Lunnan fault zone are Middle-Upper Ordovician oil. This distribution of oils in Lunnan area is owing to that Lunnan fault zone is located in anticline axis part, Lunnan fault zone underwent serious erosion, and the oils from Cambrian source rock accumulated in Lunnan fault zone were degraded completely during Caledonian-Hercynian movement. But the Cambrian oil accumulated in Sangtamu fault zone was not degraded completely and some of them were left for the location of Sangtamu fault zone is lower than Lunnan fault zone. Later, the oil derived from Middle-Upper Ordovician source rock mixed with the remained Cambrian oil, and the mixture oil formed in Sangtamu fault zone. | MI JingKui ZHANG ShuiChang CHEN JianPing TANG LiPing HE ZhongHua | 2007 | Chinese Science Bulletin2007,52,A01: | 10 |