南海南部海域曾母盆地油气地质特征

Petroleum geology of the Zengmu basin in the southern South China Sea

曾母盆地是位于南海南部的一个大型新生代沉积盆地,具有面积大、沉积速率快、沉积厚度大的特点。国内外油气勘探和研究表明,曾母盆地具有十分良好的油气地质条件,主要发育渐新统海陆过渡相炭质页岩、煤层、海相泥岩和下—中中新统海相泥岩两大套烃源岩,以及渐新统—中新统砂岩和中—上中新统灰岩或礁灰岩两大套储层。康西坳陷和东巴林坚坳陷为盆地两个主要生烃区。纵向上,油气主要赋存于下中新统砂岩和中上中新统碳酸盐岩,前者以含油为主,后者以含气为主;横向上,曾母盆地具有南油北气的特征,气田主要分布在东部南康台地上和西部斜坡上,油田主要赋存在巴林坚地区。油气分布具有明显的分区性,主要与盆地不同构造单元构造和沉积作用的差异性相关。

The Zengrnu basin is a large Cenozoic sedimentary basin located in the southern South China Sea, characterized by a high sedimentation rate and great thickness. Recent petroleum exploration and research indicate that the Zengrnu basin has very favorable geological conditions for the formation of petroleum, where there occur mainly two groups of source rocks, including Oligocene paralic carbonaceous shale, coal layers and marine mudstones and lower-middle Miocene marine mudstones, and two types of reservoirs, namely, Oligocene- middle Miocene sandstones and middle-upper Miocene limestone or reef limestone. The Kangxi depression and Eastern Balinjian depression are two primary hydrocarbon-generating zones. Vertically, petroleum mostly occurs in lower Miocene sandstone and middle-upper Miocene carbonates, with the formar mainly containing oil and the latter mainly containing gas. Laterally, the petroleum distribution in the Zengmu Basin is characterized by occurrence of oil in the south and gas in the north. Gas fields are mainly distributed in the Nankan mesa in the east and the western slope, while oil fields mainly occur in the Balinjian area. The distinct zonal distribution of oil and gas is primarily related to structures in different tectonic units and difference in sedimentation in the basin.