中国东南海域中生界油气地质条件与勘探前景

中国东南海域中生代地处欧亚板块东南缘, 夹持于欧亚板块、太平洋板块与印度澳大利亚板块之间。以往对于该区域的油气勘探多集中于新生代。笔者在前人研究的基础之上, 结合新近获得的地震资料, 开展了中国东南海域及周缘油气地质条件研究。结果表明:中国东南海域中生界分布广, 东海南部、台湾岛以及台西南盆地发育中生界深海相硅质岩, 可能与冲绳缝合带和菲律宾巴拉望缝合带形成有关;南海北部及周缘陆区发育上三叠统下侏罗统海相和海陆交互相碎屑岩及上侏罗统白垩系陆相碎屑岩, 可能与印支期缝合带的形成有关。从海域钻井及周缘陆区沉积层序资料推断, 中国东南海域有两套发育良好的烃源岩, 具有较强的生烃潜力:上三叠统下侏罗统海相泥页岩, 有机碳质量分数为0.28%~14.96%, 干酪根类型主要以Ⅱ₂型和Ⅲ型为主;下白垩统海相泥页岩, 有机碳质量分数为0.60%~2.00%, 干酪根类型以偏Ⅱ₂Ⅲ型为主。该海域发育两套生储盖组合:一套以上三叠统下侏罗统泥页岩为烃源岩, 中、上侏罗统砂岩为储层, 下白垩统泥页岩为盖层;另一套以下白垩统泥页岩为烃源岩, 白垩系砂岩为储层, 上白垩统泥页岩为盖层。它们相互可以形成"古生新储"、"自生自储"油气藏组合。因此, 中国东南海域中生界是值得关注的油气勘探新领域。

Petroleum Geological Conditions and Exploration Prospect of the Mesozoic in Southeast China Sea Area

Southeast China Sea area is located in the southeast margin of the Eurasian plate, surrounded by the Pacific plate and Indian plate in the Mesozoic stage.The petroleum explorations in the past are more concentrated on the Tertiary in this area.Based on previous studies ,We propose the Mesozoic is a noteworthy exploration through the analysis of petroleum geological conditions in the Southeast China Sea and its periphery.The results of our studies have shown that the Mesozoic strata widely distributes in Southeast China Sea.The distributions of Mesozoic in the southern East China Sea,the Taiwan Island and the southwest Taiwan basin were related to Okinawa suture zone and the Philippines Palawan suture zone,and there were deep sea facies siliceous sedimentation, and the distributions of Mesozoic in the northern South China Sea and the adjacent land areas,especially the marine strata were related to the early Ailao Mountain-Red River Indosinian suture zone,and there were the Upper Triassic-Lower Jurassic marine facies and marine-terrigenous facies clastic rocks and Late Jurassic-Cretaceous continental clastic sediments.It can be inferred from the drilling data and land geology that there are two sets of good hydrocarbon source rocks developed and stronger hydrocarbon generating potential in the Southeast China Sea.A series of hydrocarbon source rock is the Upper Triassic-Lower Jurassic marine mud shale,with organic carbon contents between 0.28% 14.96%,the main types of kerogen type dominated Ⅱ2 and Ⅲ,and another is the Lower Cretaceous marine mud-shale,with organic carbon content between 0.60% 2.00%,kerogen type Ⅲ,partial type Ⅱ2 .And there are two sets of source-reservoir-caprock assemblages.One is composed of the Upper Triassic-Lower Jurassic Marine mud-shale and Lower Cretaceous marine mud-shale as hydrocarbon source rocks, the Middle-Upper Jurassic sandstone as reservoir,together with the Early Cretaceous mud shale as caprock.Another is composed of the Early Cretaceous mud shale as hydrocarbon source rocks,and the Cretaceous sandstone as reservoir,the Upper Cretaceous or later mud-shale as caprocks.It is worth exploring plays formed by combining with the “lower source-upper reservoir”and “self source-self reservoir”.