琼东南盆地松南低凸起潜山演化及成藏条件

Evolution and reservoir formation conditions of buried hills in Songnan Low Uplift of the Qiongdongnan Basin

琼东南盆地松南低凸起潜山发育广泛,但尚缺乏系统研究,为了厘清潜山对该区油气勘探的影响,根据琼东南盆地重磁、地震、钻井及分析化验资料,结合南海北部陆缘构造演化特征,分析了松南低凸起潜山的形成演化及成藏条件。研究表明:松南低凸起潜山形成于中生代末区域性隆升阶段,早期变质岩遭受风化剥蚀,顶部出露花岗岩,潜山形成,构造类型上属于花岗岩残丘山,在后期构造应力作用下,孔隙、裂缝大量发育,油气主要聚集在风化壳和裂缝带内,上覆的半深海—深海泥岩作为大套的区域盖层,形成该区良好的储盖组合;研究区被多个生烃凹陷环绕,烃源充足,断裂和砂体作为输导通道,成藏条件优越,为它源侧向成藏模式。松南低凸起潜山圈闭成带发育,资源潜力丰富,可作为下步重点勘探领域。

Buried hills developed extensively in Songnan Low Uplift of the Qiongdongnan Basin. But there is no sys- tematic researches related to such buried hills. To clarify impacts of buried hill on oil-gas exploration in the con- cerned area, gravity-magnetic, seismic, drilling and lab test data of the Qiongdongnan Basin have been used in combination with continental-edge tectonic evolution features in northern parts of South China Sea to analyze forma- tion, evolution and reservoir formation conditions in buried hills of the Songnan Low Uplift. Research results show ： buried hills in the Songnan Low Uplift were formed during Late Mesozoic regional uplifting stage with early metamor- phic rocks experienced weathering and denudation. With granite exposed on top, buried hills were formed. Structur- ally, these buried hills can be classified as granite remnant hills. Under tectonic stresses in later stages, pores and fractures developed massively. Hydrocarbons accumulated predominantly in weathering crust and fractured belts. Covering semi-deep-sea--deepsea mudstone may serve as large package of regional caprocks. In this way, favora- ble preservation-capping assemblies can be formed within the concerned area ; The concerned area is surrounded by multiple hydrocarbon-generating sags with sufficient hydrocarbon supplies. With faults and sandstone formations served as transmission channels, these areas have outstanding reservoir formation conditions. Generally speaking, these reservoirs have lateral formation patterns characterized by external sources. The Songnan Low Uplift contains well developed buried hill traps with rich resource potentials. Consequently, the Area may serve as major explora- tion target in future.