【作者】 徐言岗；

【导师】 彭大钧；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2010， 博士

【摘要】 中国南方古生界历经半个多世纪的油气勘探,已在四川盆地及其周缘的中组合(D-T2)发现了普光、元坝等大型天然气田,油气勘探已取得了的重大突破,但除此之外的南方广大地区却一直处于徘徊状态,尤其是中国南方下组合(Z-S)的油气勘探,除威远气田外,未能获得有工业价值的勘探成果。中国南方古生界众多的油气显示,无疑证明了中国南方古生界具有良好的生烃条件,并在地质历史时期有过大规模的成藏过程。因此,具体分析中国南方古生界的古油气藏成因,探索中国南方古生界油气的成藏规律,将为寻找新的油气勘探领域和方向提供一些启示和借鉴。中国南方系统的古油气藏研究始于上世纪70年代末期,随着麻江特大型古油气藏的发现,众多石油地质工作者开始了古油气藏的成因探索。古油气藏泛指已经破坏了的但可以进行圈闭恢复的油气藏,其原生油气藏形成时期相对较早,中国南方多形成于古生代。中国南方古生界的古油气藏主要分布于江南-雪峰隆起以西至四川盆地的广大地区,现今残存物为沥青、油苗和井下天然气,在海相砂岩与碳酸盐岩的孔隙、裂缝、晶洞、溶孔、溶洞中产出,尤以裂缝中最为发育。下古生界以沥青显示为主,奥陶系有少量油苗显示,主要显示于雪峰隆起西侧及黔中隆起周缘;上古生界以油苗和井下天然气显示为主,主要显示于古隆起周缘及湘中坳陷。古油气藏在平面上的分布受控于古隆起的位置及深大断裂的走向,主体沿北东方向于深大断裂附近产出。中国南方巨厚的古生代沉积为古油气藏的形成奠定了雄厚的物质基础。早古生代沉积了被动陆缘-宽缓斜坡沉积层;晚古生代由台盆-克拉通内海相沉积层组成。下古生界的斜坡及深海盆地相区,广泛发育下寒武统黑色碳质页岩,为古油气藏的提供了良好的烃源,台地及上斜坡相区发育的白云岩、砂岩为油气的储集提供了良好的空间,下寒武统泥岩及下志留统泥岩为古油气藏提供了保存条件,共同构成了中国南方的下古生界的含油气组合(z-s下组合)。都匀运动、广西运动不仅为下古生界古油气藏的形成提供了规模聚集的场所,也为古油气藏的聚积提供了油气运移的动力,下古生界古油藏初始形成于加里东期的大型正向构造之中。加里东运动之后,扬子板块与华夏板块拼合,形成统一的华南板块,中泥盆世-中三叠世,中国南方接受了广泛的厚度巨大的海相沉积,使得下组合油藏向气藏转化;印支运动的大规模抬升和燕山运动的挤压、推覆加剧了古油气藏的破坏。中国南方古生界典型古油气藏解剖表明:古油气藏是多期构造运动改造与叠加的综合产物,古油气藏一般经历了油藏-气藏-残留的演化过程,其中,加里东运动、印支-燕山运动对古油气藏的形成与演化起着至关重要的作用,古油气藏被改造、破坏的根本原因是后期地层的抬升、剥蚀幅度过大。中国南方典型古油气藏成因分析表明:中国南方古生界仍然是我国油气勘探的一个重要领域。但是,在今后的勘探中,应特别重视古油气藏与今油气藏的差异:古油气藏的最终结果是被破坏与逸散;而今油气藏需要被保存与聚集。二者的成藏机理有着本质的区别:古油气藏的源来自于烃源岩,而下古生代的烃源岩现今都已进入的过成熟期,不可能为有效烃源岩,其早期生成的烃类必须以特殊的方式方能保存下来,成为有效次级源,为后期的晚期成藏提高足够的物质补给。威远气田的水溶气出溶成藏模式对中国南方寻找古老油气藏具有普遍的指导意义,就中国南方而言,形成古老油气藏至少须满足2个条件:(1)较好的后期保存条件;(2)早期深埋和后期大幅抬升。现今缺乏保存条件的地区或埋藏深度过大的地区都不可能取得下古生代的油气勘探突破。依据上述分析,雪峰隆起西南缘的武陵坳陷、黔南坳陷、湘鄂西地区的秭归复向斜和雪峰隆起东南缘的湘中、桂中坳陷、四川盆地古隆起区乃是今后下古生代油气勘探的重点地区。更多还原

【Abstract】 Oil & gas exploration in Paleozoic in southern China have undergone for more than half a century. Huge natural gas fields such as Puguang and Yuanba have been found in Sichuan Basin and its margin and great breaks have been gotten in oil & gas exploration, but except for these, vast areas in southern China can not get commercial exploration results. Many oil & gas shows in Paleozoic in south China prove that Paleozoic in south China possesses favorable hydrocarbon generating conditions and it has undergone great reservoir formation process in geological history. Therefore, to analyze the factors for forming palaeo-reservoirs in Paleozoic in south China and probe the rules of forming palaeo-reservoirs in south China will provide some revelations and references for finding new areas and direction for oil & gas exploration.The study on palaeo-reservoir system in southern China starts from the end of the 1970s. With the discovery of the huge Majiang Palaeo-Reservoir, a great deal of petroleum geologists then began to study the origin of palaeo-reservoirs. Palaeo-reservoirs are the reservoirs that had been destructed but can be resumed, the original/primary reservoirs were formed in relatively early times and many palaeo-reservoirs in southern China were formed in Paleozoic. The palaeo-reservoirs in southern China are distributed widely from western part of Jiangnan-Xuefeng Uplift to vast area of Sichuan Basin, the bitumen, oil shows and well natural gas remained are discovered in pores, fractures, cavities, leach holes and corroded hollows, specially in the fractures. Oil and gas shows in Lower Paleozoic are dominated by bitumen and Ordovician by a spot of oil shows, which are mainly showed in the western side of Xuefeng Uplift and margins of Qianzhong Uplifts. Oil & Gas shows in Upper Paleozoic are dominated by oil shows and downhole gas shows, which are mainly showed in margins of palaeo-uplifts and Central Hunan Depression. The planar distribution of palaeo-reservoirs is controlled by location of uplifts and trend of great deep faults, its main part is distributed in great deep fault in east-northern direction.Great Paleozoic sediments in southern China have set great material base for formation of Palaeo-reservoirs. In early Paleozoic there deposited passive continental margin—wide gentle slope sedimentary layers and late Paleozoic are consisted of platform basin-intracratonic marine sedimentary layers. There widely develop black carbonic shale of lower Cambrian in slope and deep sea basin of lower Paleozoic, which is dominated by ascending oceanic current and provide abundant hydrocarbon source base for formation of palaeo-reservoirs. The dolomites and sandstones in platform and upper slope provide favorable storage space for oil & gas, the mudstones of lower Cambrian and lower Silurian provides preservation conditions for palaeo-reservoirs. All these form the petroliferous combination (z-s Lower Combine) of lower Paleozoic in southern China. Duyun Structural Movement and Guangxi Structural Movement not only provide accumulating places in large scale for formation of palaeo-reserviors of lower Paleozoic in southern China, but also provide motivate force to accumulate oil & gas for palaeo-reservoirs. The palaeo-reservoirs of lower Paleozoic were initially formed in great positive structures. After Caledonian Structure Movement, Yangtze Plate and Cathaysian Plate jointed to form an uniform plate named Southern China Plate. From mid Devonian to mid Triassic, southern China accepted marine deposits with great thickness, on one side it made the oil reservoirs of lower combination(Z-S) transform to gas reservoirs, on the other side new petroliferous combinations came into being in Devonian, Carboniferous and mid Triassic(D-T Combinations).Analyses on typical palaeo-reservoirs of Paleozoic in southern China show: palaeo-reservoirs are comprehensive products from multiple structural movements and their superimpositions and generally the palaeo-reservoirs underwent the evolution course of oil reservoir—gas reservoir-residual in which Caledonian movement and indo-China—Yanshanian movement play key role in paleo-reservoirs farmation and their evolution. The basic reasons for reform and destruction of palaeo-reservoirs are the great elevation and erosion of strata in the later period.According to the analyses above, Paleozoic in south China is still an important field for oil & gas exploration in China. Our exploration works in future should attach more attention to the difference between paleao-reservoirs and present reservoirs. The paleao-reservoirs were nearly destructed finally while the present reservoirs need to be preserved. The forming mechanism of paleao-reservoirs are essentially different. Hydrocarbon resources of paleao-reservoirs come from source rocks. However, the lower Paleozoic source rocks can never be effective source rocks due to their overly thermal maturities. Therefore, hydrocarbons that generated in early times must be preserved in special way and then become effective secondary sources as the substantial supply to the latter reservoir forming. The water-solution gas reservoir forming model of Weiyuan field has set a guidence for discovery of paleo-reservoirs in south China. As for south China area, two conditions must be satisfied for the paleo-reservoirs formation, one is favorable later preserving conditions and the other is that the deeply buried reservoirs in early stage must be considerably uplifted later. Exploration breakthrough will never attained in areas with on preserving conditions or overly buried depth. According to these above analyses, Wuling Depression, Qiannan Depression in south-western edge of Xuefeng Uplift, Zigui Synclinorium, Guizhong Depression in the areas of Western part of Hunan and Huabei Province are considered to be the major exploration area in future.更多还原