下扬子地块2个古生界地质剖面的烃源岩特征及其对南黄海盆地的意义

CHARACTERISTICS OF THE SOURCE ROCKS FROM TWO PALEOZOIC GEOLOGICAL SECTIONS IN THE LOWER YANGTZE AND THE IMPLICATION FOR THE SOUTH YELLOW SEA BASIN

针对南黄海海域油气勘探缺乏揭示古生界钻井样品资料的窘况,对邻近陆区2个典型露头剖面进行了调查研究。这2个剖面分别为南京幕府山的下古生界寒武系陆相泥岩和安微巢湖的上古生界二叠系海相灰岩,都呈深灰黑色;前者是当前下扬子陆区页岩气勘探重点研究层系;后者出露面积较大,似臭鸡蛋味浓烈,为含硅碳酸盐岩,俗称"臭灰岩"。通过系统油气地球化学测试,证实其均为优质烃源岩;岩石物性测试结果表明,后者还可为优质储集岩。由于古生代下扬子地块具有地台性质,沉积体系向南黄海海区自然延伸沉积,因此,利用这些来自陆区露头地质剖面的珍贵样品推测,二者均可作为南黄海盆地尤其是南部坳陷的潜在主力烃源岩,以期为相应的油气勘探评价提供借鉴。

No Paleozoic drilling samples are available in the South Yellow Sea so far. It has brought difficulties to the oil and gas exploration in the region. However, there are 2 sections in the nearby region, i.e. the Lower Paleozoic Cambrian terrigenous mudstone deposits on the Mufu mountain of Nanjing and the Paleozoic Permian marine limestone in the Chaohu region of Anhui province, and both are dark grey to black in color. The former is now the target of shale gas exploration on the Yangtze continent, and the later consisting of silicified limestone is known as the ＂rotten limestone＂ widely exposed in the Yangtze region. Oil and gas geochemical testing confirms that both of them are high quality source rocks. Test of physical properties even shows that the latter could also be high quality reservoir rocks. The Lower Yangtze region was then a platform in Paleozoic, the deposits could be extended to the South Yellow Sea. Therefore, it is reasonable to extend the research results of the samples from the outcrops of the land area, to the South Yellow Sea, in particularly the Southern Depression of the South Yellow Sea Basin as potential hydrocarbon source rocks.