琼东南盆地深水区松南低凸起天然气成藏条件与勘探潜力

Gas accumulation conditions and exploration potentials of natural gases in Songnan low uplift,deep water area of Qiongdongnan basin

采用三维地震及新钻井资料,对琼东南盆地深水区松南低凸起天然气成藏条件与勘探潜力进行了综合分析,结果表明该低凸起为一继承性隆起,经历了裂陷期、断拗转换期、拗陷期等3个构造演化阶段;呈现多凹供烃,崖城组倾气型源岩主力生烃,烃源条件良好;发育花岗岩潜山、崖城组与陵水组三角洲砂岩以及三亚组水道砂等多套储层,储集性优良;形成前古近系潜山+古近系披覆背斜+地层超覆以及三亚组水道砂岩性圈闭等多种圈闭,纵向叠置特征明显。该低凸起是油气沿台缘同生长断裂+古近系多个不整合面构造脊汇聚式运移的有利指向区,勘探潜力大,其中永乐8区位于松南低凸起西南部高部位,发育前古近系潜山+古近系披覆背斜及下中新统三亚组水道砂岩性圈闭,圈闭面积大,且为多层系叠合,目标层具有含气地震信息,是下一步天然气藏勘探的有利靶区。

Based on the 3D seismic data and the latest drilling results,this paper comprehensively investigated the gas accumulation conditions and exploration potentials in the Songnan low uplift,deepwater area of Qiongdongnan basin.The low uplift is an inherited one and experienced three tectonic evolution stages,i.e.,chasmic stage,fault sag transformation stage and depression stage.It is well sourced by surrounding sags where the Yacheng Formation acts as the main gas-prone source rock and the source properties are good.Several types of reservoirs are developed including buried granite hill,deltaic sandstones of Yacheng Formation and Lingshui Formation and the Sanya channel sandstones,and the reservoir properties are good.Different types of traps including the pre-Paleogene buried hill trap,Paleogene draped anticline and stratigraphic onlap trap,and the Sanya Formation channel lithologic trap are developed and are characterized by vertically superpose.In addition,the Songnan low uplift is located on the favorable pathways of focusing gas migration along platform marginal faults,Paleogene unconformities and structural ridge,and therefore has a large exploration potential.In particular,the YL8 area,located in the southwestern high part of the low uplift,develops pre-Paleogene buried hill and Paleogene draped anticline and Miocene Sanya Formation channel lithologic traps with large areas,and often vertically overlaid with each other.There is the obvious gas-bearing seismic anomaly in target layers,suggesting that it is a favorable target for the future gas exploration.