莺歌海盆地中央泥底辟带东方区与乐东区中深层成藏地质条件

莺歌海盆地位于越南与我国海南岛西南之间的莺歌海海域,迄今为止天然气勘探已经发现东方1-1和乐东15-1等浅层气田群。盆地中深层天然气勘探程度较低,目前仅在东方区东方13-1、13-2构造岩性圈闭获得了天然气勘探的重大突破。通过中央泥底辟带东方区和乐东区浅层气藏地质条件及主控因素的深入研究,重点剖析了东方区中深层高温超压气藏形成的生储盖组合特征及其成藏主控因素,强调来自越南西部(莺西斜坡)物源、储集物性较好的上中新统黄流组海底扇储盖组合及其岩性圈闭,是其高温超压领域天然气成藏的关键控制因素。中央泥底辟带东南部乐东区中深层迄今尚未开展大规模天然气勘探,但天然气地质条件与东方区基本一致,只是其物源供给体系、储集层及储盖组合类型等可能存在一定的差异,而储盖组合及圈闭条件依据目前资料分析尚好,能够形成商业性高温超压天然气藏。因此,预测乐东区中深层亦具备较好天然气运聚成藏条件,天然气勘探前景广阔。

ASSESSMENT OF ACCUMULATION CONDITIONS FOR MEDIUM-DEEP OIL IN LEDONG AREA OF THE CENTRAL DIAPER BELT,YINGGEHAI BASIN

The Yinggehai Basin is located in the Yinggehai sea between Vietnam and Hainan Island. Up to now, only have the shallow gas fields DF1-1 and LD15-1 and several others been discovered. However, the exploration of medium-deep layers of hydrocarbon remains very low. So far, only have the DF13-1/13-2 structural-lithological traps got gas breakthroughs in the Dongfang area. In this paper, by analyzing and studying the geological conditions and main controlling factors of shallow gas fields in Dongfang and Ledong areas, we discussed in depth the characteristics of the source-reservoir-cap assemblages, and controlling factors for medium-deep reservoirs forming and the high temperature and over pressured gas reservoir in the Dongfang area. It is found that the western provenance from Vietnam, the reservoir-cap assemblages and the lithological traps with certain reservoir physical properties of the upper Miocene submarine fan are the key controlling factors for the formation of high temperature and over pressured gas reservoirs. Large scale of natural gas exploration has not been launched so far for the medium-deep strata in the Ledong area. But the basic conditions for hydrocarbon accumulation remain similar between the deep and the shallow. Of course, there may be few differences in provenances, reservoirs and reservoir-cap assemblages between the two areas. However, the conditions of reservoir-cap assemblages and traps are even better in the deeper part according to newest information. In conclusion, there is great potential to discover medium and deep commercial high temperature and over pressured gas reservoirs in the medium-deep layers of the Ledong area.