三塘湖盆地南缘冲断带成藏条件及勘探方向

Reservoir-forming Conditions and Exploration Orientation of Southern Thrust Belt, Santanghu Basin

三塘湖盆地南缘冲断带位于中央坳陷带以南,以南缘逆冲推覆断裂带为界与中央坳陷带分隔,紧邻条湖、马朗两大生油气凹陷,发育多套储盖组合。逆冲推覆断裂带的形成主要受控于晚海西运动和晚燕山运动,逆冲推覆断裂带下盘发育石板墩、黑墩两个构造带。目前,已发现黑墩P2l、石板墩C2k和西峡沟M4-T14区块J2x等多层系油气藏,证实其为一复式油气聚集带。构造、岩性、裂缝和火山岩体控制了油气藏的形成与分布。下一步应积极拓展南缘冲断带二叠系裂缝型油气藏,加强古生界火山岩油气藏勘探,同时兼顾中生界砂岩油气藏勘探,勘探思路应从构造控油打高点向岩性控油打河道、裂缝控油打破碎带、火山岩体控油打火山体转变。

Southern Thrust Belt in Santanghu Basin is located at the south of Central Depression Belt. A southern thrusting nappe fault zone is between these two belts. In addition, the former is very close to Tiaohu and Malang hydrocarbon-generating sags. There are lots of reservoir-seal associations developed at Southern Thrust Belt. The thrusting nappe fault zone was generated by late Hercynian movement and late Yanshanian movement; furthermore, two structural zones of Shibandun and Heidun are developed at the lower wall of fault zone. At present, many reservoirs with multiple sequences, including Hedun P2l, Shibandun C2k, J2x in Xishan’ gou M4-T14 Block, were discovered and demonstrated to a complex hydrocarbon accumulation belt. Reservoir formation and distribution are controlled by structure, lithology, fracture and volcanic rock. In the next, the Permian fractured reservoirs in Southern Thrust Belt should be further studied; the exploration of both Palaeozoic volcanic and Mesozoic sandstone reservoirs will be strengthened; and the exploration strategy should be changed from one point that structural high is drilled in structural reservoirs to some points that channel is drilled in lithological reservoirs, fractured zone is drilled in fractured reservoirs and volcanic body is drilled in volcanic-rock reservoirs.