石油学报 ›› 2013, Vol. 34 ›› Issue (4): 611-627.DOI: 10.7623/syxb201304001

• 地质勘探 •    下一篇

中国南海含油气盆地构造类型及勘探潜力

张功成1, 谢晓军1, 王万银2, 刘世翔1, 王一博1, 董伟1, 沈怀磊1   

  1. 1. 中海油研究总院 北京 100027;
    2. 长安大学地质工程与测绘学院 陕西 西安 710054
  • 收稿日期:2012-12-07 修回日期:2013-03-01 出版日期:2013-07-25 发布日期:2013-07-04
  • 通讯作者: 张功成
  • 作者简介:张功成,男,1966年1月生,1988年获西北大学学士学位,1994年获中国地质大学(北京)博士学位,现任中国海洋石油总公司勘探专家、中海油研究总院勘探研究院总地质师、教授级高级工程师,从事石油天然气地质综合研究及油气勘探管理工作。Email:zhanggch@cnooc.com.cn
  • 基金资助:

    国家重点基础研究发展计划(973)项目"南海深水盆地油气资源形成与分布"(2009CB219400);国家重大科技专项"海洋深水区油气勘探关键技术"(2008ZX05025、2011ZX05025)及国土资源部全国油气资源战略选区调查与评价项目(XQ-2004-05、XQ-2007-05)资助。

Tectonic types of petroliferous basins and its exploration potential in the South China Sea

ZHANG Gongcheng1, XIE Xiaojun1, WANG Wanyin2, LIU Shixiang1, WANG Yibo1, DONG Wei1, SHEN Huailei1   

  1. 1. CNOOC Research Institute, Beijing 100027, China;
    2. College of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, China
  • Received:2012-12-07 Revised:2013-03-01 Online:2013-07-25 Published:2013-07-04

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摘要：

中生代末期以来,中国南海区域经历古南海裂开—萎缩、新南海裂开—萎缩两大边缘海旋回,形成了南海北部大陆边缘、新南海洋盆、南沙地块、古南海残余洋盆、古南海南部大陆边缘、南海西部大陆边缘和南海东部大陆边缘等构造单元。由于古、新南海洋盆位置的不同,古南海裂开形成的构造格局在后期受到不同的截切、改造,并且形成新的构造格局。两大旋回构造叠加控制了不同单元的性质及其上叠盆地的类型与油气地质条件。南海北部大陆边缘在两大旋回中均表现为被动大陆边缘特征,但早期旋回的大陆边缘规模大(包括新南海旋回被裂离出去的南沙地块),现今残余的早期旋回仅是其陆内陆相裂谷部分, 与晚期旋回陆缘海陆过渡—海相裂谷区叠加,形成拉张盆地。早期烃源岩以中—深湖相地层为主,晚期烃源岩为海陆过渡相三角洲和海相泥岩;早期旋回烃源岩近岸分布,晚期旋回烃源岩远岸分布;早期主要呈陆生陆储或陆生海储,晚期则呈海生海储。南沙地块早期为古南海北部边缘裂陷盆地,发育海相烃源岩;中期向南飘移数千公里,夹持于古、新洋盆之间,沉积欠补偿;晚期被挤压改造,盆地沉积以早期旋回为主,呈现海生海储。古南海南部大陆边缘在早期为被动大陆边缘,晚期被改造成活动大陆边缘;早期的伸展盆地上叠挤压盆地,早期旋回地层被深埋处于变质状态,晚期旋回地层以大型三角洲群和海相泥岩为主,油气兼生,海生海储。南海西部大陆边缘早期为陆内环境,晚期被改造成转换型大陆边缘,张扭盆地发育,早期发育局限的陆相地层,晚期以海陆过渡三角洲相地层为主,该区域热流值高,以生气为主,发育底辟、潜山、生物礁等油气藏。南海东部大陆边缘正在俯冲,发育增生楔盆地。两期旋回不同的叠加关系,导致不同区域油气潜力差异巨大。古南海南部大陆边缘早期拉张、晚期挤压,盆地规模大,烃源岩丰富,均达到成熟状态,油气资源非常丰富。南海北部、西部裂陷盆地发育两套烃源岩,油气很丰富。南沙地块区早期处于古南海北部被动大陆边缘,晚期挟持于古南海残余洋盆与新南海洋盆之间,遭受区域性挤压,构造圈闭非常发育,油气潜力大。南海目前浅水区构造圈闭和生 物礁勘探程度较高,其他非构造圈闭勘探程度很低;深水区和超深水区已有重要发现,但尚处于勘探早期阶段,南海未来勘探潜力依然可观。

关键词: 大陆边缘, 盆地类型, 地质条件, 构造格局, 边缘海旋回, 烃源岩, 南海

Abstract:

Since Late Mesozoic, the united South China Sea region has experienced at least two tectonic cycles of marginal seas, i.e. the cleavage to convergence of the paleao-South China Sea, and the cleavage to convergence of the neo-South China Sea, which formed a couple of structural units, such as the northern continental margin of the South China Sea, the oceanic basin of the neo-South China Sea, the Nansha block, the residual oceanic basin of the palaeo-South China Sea, the northern continental margin of Borneo, and the western and eastern continental margins of the South China Sea. The tectoic framework developed in the cleavage of the palaeo-South China Sea was afterwards truncated and reworked to form a new tectoic framework because of the difference in locations of the palaeo-South China Sea and the neo-South China Sea. The superimposition of these two cycles controls properties of these different units, types of overlying basins and geological conditions of hydrocarbons. The northern continental margin of the South China Sea was of a passive continental margin in both the cycles though its scale (including the Nansha block parting away during the second cycle) was larger in the first cycle than the present residual part of the first cycle, which, only as an intracontinental rift part, was superimposed by the transitional marine rift developed in the late cycle to form tensional basins. Source rocks of the early cycle dominated by semi-deep lake strata, are distributed offshore and mainly generate oil that accumulate in nonmarine or marine facies, while those of the late cycle, composed of mainly transitional deltaic deposits and marine mudstones, are distributed infralittorally and generate oil that are reservoired in marine facies. The Nansha block used to be a rift basin that developed marine source rocks and was located at the northern continental margin of the South China Sea in the early cycle, afterwards it drifted southward for thousand kiometers and lay between the palaeo- and neo-oceanic basins, remaining in an under compensation status. During the late cycle it was compressed and reworked, its deposits are dominated by marine facies of the early cycle, with occurrences of marine source rocks and reservoirs. The southern continental margin of the palaeo-South China Sea used to be a passive continental margin during the early cycle but was reworked into an active continental margin during the late cycle. Stretched basins formed in the early cycle are superimposed by compressional basins developed in the late cycle, and strata of the early cycle are deeply buried and of metamorphism, while strata deposited in the late cycle consist mainly of large-scale deltas and marine mudstones, with occurrences of both oil and gas in marine facies. The western continental margin of the South China Sea was formed in an intracontinental environment during the early cycle, and then reworked into a transformational continental margin during the late cycle, where tenso-shear basins developed with restricted terrestrial strata deposited in the early cycle and transitional deltaic strata deposited mainly in the late cycle. This area has a high value of heat flow and is apt to generate gas. Oil-gas reservoirs such as diapirs, buried hills and reefs are well developed in this area. Presently the eastern continental margin of the South China Sea is subducting with the development of accretionary wedge basins. The superimposition of the two different cycles leads to a great difference in exploration potential of different areas. The southern continental margin of the palaeo-South China Sea experienced extension and compression in the early and late cycles, respectively, resulting in the formation of large-scale basins, the richness of mature source rocks and enormous resources of hydrocarbons. Two suits of source rocks are well developed in rift basins of the northern and western South China Sea and they have generated an abundance of hydrocarbons. The Nansha block was located at the northern passive margin of the palaeo-South China Sea in the early cycle and restrained between the remnant oceanic basin of the palaeo-South China Sea and the oceanic basin of the neo-South China Sea. It contains well-developed structural straps due to regional compression and shows a great potential in petroleum resources. Presently, the degree of petroleum exploration is high in shallow water areas of the South China Sea, especially for structural traps and organic reefs, with the exception of non-structural traps. However, the petroleum exploration in deepwater and ultra-deepwater areas of the South China Sea remains yet at an infant stage though some significant discoveries have been made. Hence, the exploration potential of the South China Sea is still considerably great in the future.

Key words: continental margin, basin type, geological condition, tectoic framework, cycle of marginal sea, hydrocarbon resource, South China Sea

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