Discussion of gas enrichment mechanism and natural gas origin in marine sedimentary basin,China

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.     

Identification of the Kukersite-type source rocks in the Ordovician Stratigraphy from the Tarim Basin, NW China

Due to the importance of the Gloeocapsomorpha Prisca （G. prisca）-enriched source rocks, which belong to Kukersite-type source rocks in the Lower Paleozoic Ordovician strata, it has received great attentions during the petroleum exploration as to whether there are the Kukersite-type source rocks developed in the major hydrocarbon source strata of the Upper and Middle Ordovician in the Tarim Basin. Using pyrolysis-gas chromatography-mass spectrography to analyse kerogens from source rocks in the lime- mud mound with moderate maturity, study reveals that there are the Kukersite-type source rocks in the Ordovician strata of the Tarim Basin. The pyrolysis products showed a low content of 〉n-C19 normal alkanes with a significant odd-even predominance between n-C13 and n-Cl7, long-chain alky substituted alkylbenzene and alkylthiophene isomers and distinctive distribution of 5-N- alkyl-1, 3-Benzenediol and its homologous. Based on the geographic environment characteristics of G. Prisca, the molecular dis- tributions of crude oil from the Lower Paleozoic petroleum systems in the Tarim Basin and characteristics of kerogen pyrolysis products from the Middle and Upper Ordovician source rocks, the results suggested that it is less possible to develop the G. Pris- ca-enriched Kukersite-type source rocks in the major hydrocarbon source rocks in the Middle and Upper Ordovician strata in the Tarim Basin. However, the benthic macroalga and planktonic algae-enriched source rocks are the main contributors.     

鄂尔多斯盆地西南缘三叠系烃源岩评价及油源对比

应用有机岩石学和分子地球化学的手段和方法,对鄂尔多斯盆地西南缘三叠系延长组长7段暗色泥岩和长8油层组原油,进行地球化学精细定量分析,研究了长7段暗色泥岩地质地球化学特征,评价了西南缘三叠系延长组长7烃源岩生烃潜力,并对长8油层组原油展开精细油源对比分析.结果表明:鄂尔多斯盆地西南缘三叠系延长组长7段暗色泥岩有机质丰度高、类型好、成熟度高,与盆地本部长7优质烃源岩具相近似的电性、岩性和地球化学特征,为一套优质的烃源岩.长8油层组原油在母源性质、沉积环境、成熟度等方而与长7段烃源岩有相近似的特征,二者具有较好的亲缘关系,长8原油来自长7段烃源岩.     

准噶尔盆地滴南地区原油地球化学特征及油源

对准噶尔盆地东道海子凹陷滴南地区的滴南1、滴南7、滴南8等井原油与烃源岩地球化学特征分析,探论该区油源关系。通过对原油的族组成、碳同位素、饱和烃色谱、甾萜烷化合物及轻烃参数、烃源岩的生物标志化合物的研究,结果表明：东道海子凹陷二叠系平地泉组烃源岩处于低成熟－成熟阶段,三环萜烷含量高,Ts＜Tm,γ蜡烷含量低,甾烷中 C27、C28、C29呈反“L”形分布。滴南地区二叠系原油和储层抽提物地球化学参数及甾萜烷特征与平地泉组烃源岩相似,具有亲缘关系。侏罗系原油具有侏罗系烃源岩来源的特征。     

Main controlling factors for hydrocarbon reservoir formation and petroleum distribution in Cratonic Area of Tarim Basin

The Cratonic Area of the Tarim Basin is lo-cated in the central part of the basin, developing primarilywith Cambrian marine source rocks and secondly Middle toUpper Ordovician marine and Carboniferous-Permiantransitional facies source rocks. The source rocks werematured in the changeable period and space, formingmultiple hydrocarbon generating centers during the periods.The Cratonic Area experienced multiple tectonic orogenies,forming several palaeouplifts. The matching conditionbetween effective hydrocarbon generating centers and thepalaeouplifts in various periods is the main control factor forthe formation and distribution of hydrocarbon reservoirs.The palaeouplifts have experienced multiple hydrocar-bon-filling phases, several periods of modifications and evenbreakdown. The palaeouplifts and the adjacent slopesaround the effective hydrocarbon generating center composethe most favorable places for hydrocarbon accumulation.The hydrocarbon phase is related with the evolution of thehydrocarbon generating center. In the Tarim Basin'sCratonic Area, reservoirs were mostly formed during lateHercynian. The originally formed hydrocarbon reservoirswhich are adjacent to source kitchens and in the goodpreservation condition are the most favorable prospectingtargets. Hydrocarbon is richly accumulated under theregional caprock, surrounding the faulted trends, and overand below the unconformity surfaces. Reservoirs in theCarboniferous sandstone, Ordovician karstic weatheredcrust and carbonate rock inside the buried hill compose themain intervals for hydrocarbon accumulation. Carboni-ferous and Silurian sandstone pinchout reservoirs andcarbonate lithologic reservoirs with rich fractures and poresare the main targets for further prospecting.     

Discussion of gas enrichment mechanism and natural gas origin in marine sedimentary basin, China

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 po- tential, 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.     

塔里木盆地石油地质基本特征

全面系统地总结并提出塔里木盆地１０大石油地质基本特征：（１）塔里木盆地为一古生界克拉通盆地与中新生界前陆盆地组成的大型叠合复合型盆地；（２）塔里木盆地经历了多期构造运动及多个演化发展阶段；（３）塔里木盆地主要有寒武—奥陶系、石炭—二叠系，三叠—侏罗系３套烃源岩；（４）塔里木盆地发育多套深埋优质储层及５套良好储盖组合；（５）塔里木盆地油气水性质复杂、油气藏类型丰富多样；（６）塔里木盆地富油又富气，天然气藏以凝析气藏为主；（７）塔里木盆地既有陆相油气，又有海相油气，已发现的石油以海相成因为主，天然气以陆相成因为主；（８）塔里木盆地已发现的油气藏以中小型为主，具有埋深大、丰度低、产能高的特点；（９）塔里木盆地具有多个成油气系统、多期成藏及油气多次运移再分配的特点；（１０）塔里木盆地油气分布十分复杂，油气聚集受多重因素制约     

川东北地区三叠-侏罗系陆相烃源岩评价及油源对比

通过系统的有机地球化学分析, 对川东北陆相地层主力烃源岩进行了系统评价, 对油、源进行了精细对比, 查明了非常规油气的成藏特征。分析认为陆相地层须家河组、自流井组和千佛崖组发育大量有效烃源岩甚至优质烃源岩, 有机质丰度较高, 各地区各层系TOC平均值介于0.41%~2.99%之间, 有机质类型主要为Ⅱ, Ⅲ型, 处于成熟?过成熟阶段(Ro介于 1.3%~2.0%之间), 具有良好的生烃潜力, 可成为该区中、下侏罗统 非常规油气的主力烃源岩。经油源对比及成藏特征分析, 发现中、下侏罗统陆相非常规油气来源于陆相烃源岩, 未显示海相油气来源, 说明由于陆相储层异常致密, 导致油气运移困难而源内或近源成藏。其中, 元坝?阆中地区千佛崖组的油气来自于自流井组烃源岩, 自流井组的油气来自于自流井组及须家河组两套烃源岩。宣汉?达县地区的油气来自于须家河组烃源岩。下侏罗统泥页岩具备页岩气形成的条件, 中、下侏罗统致密砂岩具备致密砂岩油形成的条件。     

盐城凹陷天然气和凝析油的成因及烃源岩研究

通过地质、地球化学和分析实验等先进方法和技术 ,分析了天然气和凝析油轻烃指纹参数组成特征、单体烃碳同位素分布系列、生物标志物组成特征、相关原油或油花的生标分析、下扬子地区中古生界海相源岩评价及海相原油生标组成特征等多种资料 ,利用多种方法 ,详细探讨了凝析油中轻质组分与重质组分特征以及它们与天然气之间的关系 ,认真解剖了天然气的成熟度 ,对比剖析了可能的气源岩 ,界定了气源岩母质类型 ,并进行了气源对比探讨 .研究结果表明 ,盐城天然气属于高成熟演化阶段的产物 ,成因上归属于以古生界海相腐泥型气为主 ,混有少许泰二段腐殖型气 ,从而使得对于盐城天然气从成熟演化、成因类型、气源追溯等方面都理顺了关系     

江汉盐湖盆地油气形成与运聚特征

为厘清陆相盐湖盆地油气形成和运聚特征，以江汉盆地潜江凹陷潜江组为研究对象，通过岩芯分析的古生物、地球化学测试数据等，恢复盐湖古环境，分析盐湖沉积特征，厘定烃源岩发育及其演化特征，探讨油气排烃及运聚特征。研究结果表明，盐湖干湿交替周期变化的古气候，造成了湖盆咸淡交替，形成了碎屑岩、碳酸盐岩、蒸发岩有规律地韵律沉积，沉积岩性为成分复杂的混积岩；盐湖优质烃源岩发育在咸淡转化期，盐湖烃源岩演化相对滞后，发育未熟低熟油演化阶段；特殊的盐湖沉积特征导致了烃源岩排烃效率低，形成了规模巨大的烃源岩油藏；油气主要沿侧向运移，常规砂岩油藏具有顺层、近源、砂控、源控的特点。陆相盐湖盆地的沉积、油气形成与运聚特征与海相或淡水湖盆具有明显差异性，在勘探中应当引起重视。     

渤海湾盆地南堡凹陷原油地球化学特征及油源对比

在原油地球化学特征精细剖析和对比的基础上,划分了南堡凹陷原油的成因类型,并根据生物标志物组合特征对原油和烃源岩进行了对比研究.结果表明:不同构造带或同一构造带不同层位原油的地球化学特征均存在一定的差别,据此可将原油划分为6类,其中第Ⅰ类主要分布于柳赞油田和高尚堡油田、老爷庙油田浅层明化镇组和馆陶组油层,第Ⅱ类主要分布在高尚堡(高柳断层以南)、老爷庙和北堡油田东营组油层,第Ⅲ类主要分布在柳赞油田及高尚堡油田(高柳断层以北)沙河街组油层,第Ⅳ类主要分布于滩海区东一段油层,第Ⅴ、Ⅵ类主要分布在滩海区奥陶系油层中;古近系3套烃源岩对不同构造带的油气聚集有不同的贡献,其中高柳构造带高柳断层以北地区的原油主要来源于沙三段烃源岩,断层以南的主要来自于沙一段和东三段烃源岩,部分混有沙三段烃源岩的贡献,老爷庙和北堡构造的原油主要来源于东三段和沙一段烃源岩,混有部分沙三段烃源岩生成的原油,滩海区原油主要来自于沙一段和沙三段烃源岩.     

沾化凹陷三合村洼陷油气多期成藏过程研究

利用钻井、测井以及分析化验等资料,基于沉积埋藏史和生烃史研究,结合油气来源,分析沾化凹陷三合村洼陷油气成藏过程。结果显示:三合村洼陷存在3种原油类型,油气主要来自于渤南洼陷,油气成藏经历了东营组成藏期、馆陶组成藏期和明化镇组成藏期3期成藏;东营组成藏期形成的油藏原油源于沙四上亚段成熟烃源岩,此时垦西低凸起还未成型,来自渤南洼陷的油气以断裂侧向-不整合型二元输导体系沿斜坡带运移至三合村洼陷沙三段及以下地层中成藏,并在后期由于硫化作用和生物降解作用发生稠化;馆陶组成藏期形成的油藏原油源于沙四上亚段和沙三段烃源岩,此时垦西低凸起已成型,来自渤南洼陷的油气主要以网毯模式运移至沙三段以上地层中,在后期发生生物降解作用而稠化;明化镇组成藏期形成的油藏原油源于沙三段成熟烃源岩,同样以网毯模式运移至三合村洼陷,主要在新近系成藏。     

Late Yanshan-Himalayan hydrocarbon reservoir adjustment and hydrotherrnal fluid activity in the central Tarim Basin

The adjustment of primary hydrocarbon reservoirs in marine formations is an important feature of the oil pools in the Tarim Basin. Large-scale hydrocarbon adjustment is related to the strong regional tectonic movements, which is always accompanied by extensive migration of basin fluids including diagenetic and mineralizing fluids. Organic fluid inclusions are well developed in hydrothermal minerals, such as fluorite, which have been found in the dissolution-enlarged fractures or karstification caves in the Ordovician in the central Tarim Basin. Proved by well drilling, the fluorite deposit is good reservoir for oil and gas. So the peculiar accompanied or superimposed relationship between fluorite hydrothermal fluid mineralization and hydrocarbon migration and accumulation exists in the Ordovician in the central Tarim Basin. Considering regional tectonic setting and mineralization condition,through different kinds of analytic methods including electron spin resonance dating, fluid inclusion laser Raman and colonial inclusions hydrocarbon fossil analysis, we proposed that extensive mineralizing fluids and hydrocarbon migration occurred in late Yanshan-Himalayan (110.4-30.8 Ma) period, and Himalayan, especially, is an important period for hydrocarbon accumulation from 34.3 Ma to present.     

Discussion on marine source rocks thermal evolvement patterns in the Tarim Basin and Sichuan Basin, west China

Taking marine source rocks of lower Paleozoic in the Tarim Basin and Paleozoic ones in the Sichuan Basin as examples, their sedimentation process could be classified into four styles continuous subsldence with deep sedimentation in early stage, continuous subsidence with deep sedimentation in later stage, that deeply buried-uplift-shallowly buried, and that shallowly buried-uplift-deeply buried.Unlike that in East China, the marine source rocks evolvement patterns did not accord with sedimentation styles one by one in superimposed basins in west China. Taking local geothermal field into account, four types of source rock evolvement patterns were built that evolved fast in early stage,evolved fast in middle stage, evolved continuously and evolved in multistage. Among them, the 1st pattern contributed little to the present industrial oil pools directly, but paleo-oil reservoirs and gases cracked from crude oils were main exploration targets. Although some gases were found in the 2nd pattern, the scale was not big enough. For the 3rd and 4th patterns, the hydrocarbon potential depended on organic matters maturity in early stage. For relatively low mature rocks, it was possible to generate some oils in later stage; otherwise the main products were gases. Paleo-oil reservoirs remained fairly well in the Sichuan Basin, and most source rocks underwent kerogen-oil-gas processes,which was useful reference to gas exploration in the Tarim Basin.     

东濮凹陷西部斜坡带混合原油地球化学特征

东濮凹陷西部斜坡带原油地球化学特征同凹陷内其他地区原油明显不同,而研究程度相对较低.系统分析了原油饱和烃、芳烃组成及生物标志物,研究结果表明:原油生油母质类型较好,以低等水生生物为主,陆源高等植物占次要地位;原油中伽玛蜡烷含量高,类异戊二烯烃呈植烷优势,表明源岩沉积环境为强还原的半咸化-咸化湖相;原油成熟度参数具有不一致性,表明原油并非是低熟油,应为混合原油,其主要来源于沙三段成熟烃源岩.     

Discussion on marine source rocks thermal evolvement patterns in the Tarim Basin and Sichuan Basin,west China

Taking marine source rocks of lower Paleozoic in the Tarim Basin and Paleozoic ones in the Sichuan Basin as examples, their sedimentation process could be classified into four styles: continuous subsidence with deep sedimentation in early stage, continuous subsidence with deep sedimentation in later stage, that deeply buried-uplift-shallowly buried, and that shallowly buried-uplift-deeply buried. Unlike that in East China, the marine source rocks evolvement patterns did not accord with sedimentation styles one by one in superimposed basins in west China. Taking local geothermal field into account, four types of source rock evolvement patterns were built: that evolved fast in early stage, evolved fast in middle stage, evolved continuously and evolved in multistage. Among them, the 1st pattern contributed little to the present industrial oil pools directly, but paleo-oil reservoirs and gases cracked from crude oils were main exploration targets. Although some gases were found in the 2nd pattern, the scale was not big enough. For the 3rd and 4th patterns, the hydrocarbon potential depended on organic matters maturity in early stage. For relatively low mature rocks, it was possible to generate some oils in later stage; otherwise the main products were gases. Paleo-oil reservoirs remained fairly well in the Sichuan Basin, and most source rocks underwent kerogen-oil-gas processes, which was useful reference to gas exploration in the Tarim Basin.     

下刚果盆地西北部深水区Albian阶Sendji组原油地球化学特征、成因及分布规律

针对下刚果盆地西北部深水区Albian阶Sendji组原油的特征、成因、来源及分布规律等问题,通过对该区7口钻井15个原油样品的物性参数、稳定碳同位素、生物标志化合物等方面的研究,结果表明,Sendji组原油总体为轻质原油,向陆一侧的3个油田中Sendji组原油具有湖相原油的特征,可能来源于盐下湖相烃源岩;向海一侧超深水区MOHO油田Sendji组原油具有海相原油的特征,可能来源于Likouala组上部海相烃源岩。下刚果盆地海域的湖相原油主要分布在近陆一侧的浅水和部分深水区,而海相原油主要分布在向海一侧的深水及超深水区,中间过渡带分布湖相和海相的混合原油。     

北部湾盆地涠西南凹陷原油成因类型及分布特征

在大量采集涠西南凹陷烃源岩和原油饱和烃色谱、色谱-质谱、碳同位素等资料基础上，对涠西南凹陷烃源岩特征进行分析，根据地球化学特征差异划分为A、B、C等3类烃源岩。系统分析原油有机地球化学特征差异性，对不同层系原油物性进行统计梳理，依据甾、萜烷、饱和烃组成等进行原油成因类型划分，将涠西南凹陷原油分为A、B1、B2、C1和C2等3大类5亚类。通过油源精细对比和原油空间分布特征分析，A类原油来源于A类源岩，主要分布在1号、2号和3号断裂附近及东南部的斜坡部位；B1和B2类原油来源于B类源岩，其中B1类原油主要分布在2号断裂附近，B2类原油主要在3号断裂附近；C1和C2类原油来源于C类源岩，C1类原油分布在与B1类原油相近的区域，C2类原油主要集中分布在2号断裂与3号断裂接近交互的部位。     

Observation of hydrocarbon generation and migration of highly-matured carbonates by means of laser-induced fluorescence microscopy

Some important information on hydrocarbon generation, inclusion and migration in highly-matured carbonates of lower Palaeozoic age from the Ordos Basin and Tarim Basin hasbeen analyzed by a newly-combined laser-induced fluorescence microscope (LFM) designed by our laboratory. The following information has been obtained from the lower Ordovician lamellar carbonates with equivalent vitrinite reflectance (Ro) as high as 1.6%-1.7% and residual TOC of 0.14%-0.35% from the Ordos Basin: wide occurrences of oil and source macerals with strong fluorescence, including G. Prisca alginite, lamalginite, telalginite and algae-detrinite; fluorescing asphalt among mineral crystals; some groundmass and spheroid-like reservoir bitumen with high maturation levels in the pores of dolomites. Various kinds of fluorescing organic inclusions and asphalt have been found in the carbonates, calcareous shales and silt-shales with high maturation levels from the Cambrian-Ordovician strata in the Tarim Basin. All this helps us find and evaluate significant and excellent source rocks for large-and middle-scale gas fields. The net and micro-net systems for hydrocarbon generation, expulsion and migration in carbonates have been revealed by the highly-powered laser-induced fluorescence microscopy.     

松辽盆地长岭断陷烃源岩特征与油源对比

长岭断陷层烃源岩和原油样品的地球化学特征分析表明,火石岭—营城组是主要烃源岩,丰度较低、成熟度较高,以Ⅲ型干酪根为主。饱和烃参数、芳烃三芴系列组成特点均表明烃源岩主要形成于微咸－半咸水湖泊的弱氧化－还原环境中,物源以陆源高等植物输入为主,其次为低等水生生物。烃源岩及原油族组分、碳同位素特征、三环萜烷和四环萜烷系列、藿烷系列、芳烃系列分布特征与对比均表明,油源与营城组烃源岩具有较好的亲缘关系。