Tracing early-charged oils and exploration directions for the Wenchang A sag, western Pearl River Mouth Basin, offshore South China Sea
Tracing early-charged oils and exploration directions for the Wenchang A sag, western Pearl River Mouth Basin, offshore South China Sea
复制标题
南海近海珠江口盆地西部文昌A凹陷早期充注石油溯源及勘探方向
DOI：
10.1016/j.orggeochem.2013.06.003
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发表时间：
2013-08-01
影响因子：
3
通讯作者：
Xiao, X. M.
中科院分区：
文献类型：
--
作者：
Cheng, P.;Tian, H.;Xiao, X. M.
文昌A凹陷是珠江口盆地西部南海海域最大的产油气次级凹陷。始新统文昌组和早渐新统恩平组是该凹陷的两套主要烃源岩。该地区的石油发现主要来自恩平组。如何客观地评价文昌组的含油气性。而追踪文昌原油一直是该地区研究和勘探的重点。本文采用系统的地球化学方法，对储层砂岩中的包裹体油、典型储层油和潜在烃源岩进行了研究。油-油和油-烃源岩对比表明，文昌A凹陷中部和边缘地区包裹体油具有相似的地球化学特征，主要来源于文昌烃源岩。中部地区的储层原油主要来自恩平组烃源岩，而边缘地区则兼有恩平组和文昌组烃源岩的特征。结合构造-沉积演化和生油史，认为文昌A凹陷两套烃源岩均已生油，但中部地区主要生油阶段为文昌组。早于圈闭形成时间，导致大部分早期生成的文昌源油散失。在边缘地区，文昌组的主要生油期为下古生界。文昌原油不仅以流体包裹体的形式被捕获在储层石英颗粒中，而且运移聚集成藏，并与恩平原油混合。文昌A凹陷中部和边缘地区，特别是深沪凸起北方的早期岩性和构造圈闭是该凹陷最具勘探前景的地区。(C)2013爱思唯尔有限公司保留所有权利。
The Wenchang A sag is the largest petroleum producing sub-depression in the western Pearl River Mouth Basin, offshore South China Sea. The Eocene Wenchang Formation and the early Oligocene Enping Formation are the two major source rocks in the sag. The oil discoveries in this region mainly originated from the Enping Fm. How to objectively estimate the petroleum potential of the Wenchang Fm. and trace the Wenchang oils has long been the focus of research and exploration in this region. In this paper, inclusion oils obtained from reservoir sandstones, as well as typical reservoir oils and potential source rocks, were investigated by systematic geochemical methods. Oil-oil and oil-source rock correlations indicate that inclusion oils in the central and marginal areas of the Wenchang A sag had similar geochemical characteristics and mainly originated from the Wenchang source rocks. The reservoir oils in the central area are derived mainly from the Enping source rocks, while in the marginal areas they have mixed characteristics of both the Enping and Wenchang formations. Combining the tectonic-sedimentary evolution and petroleum generation histories, it is concluded that the two source rocks in the Wenchang A sag have generated oils, but in the central areas the main stage of oil generation of the Wenchang Fm. was much earlier than the formation time of the traps, resulting in the dissipation of most of the early generated Wenchang sourced oils. In the marginal areas, the main stage of oil generation of the Wenchang Fm. was later and the Wenchang oils not only could be captured as fluid inclusions in the reservoir quartz grains, but also migrated and accumulated into oil pools in which they mixed with the Enping sourced oils. The early lithological and structural traps in the central and marginal areas of the Wenchang A sag, especially in the northern part of the Shenhu uplift, are the most prospective areas for further exploration of the sag. (C) 2013 Elsevier Ltd. All rights reserved.