西藏羌塘盆地盐相关构造特征与油气聚集

羌塘盆地中侏罗统盐岩层系发育,并控制了盆地变形和圈闭样式,将盆地盐相关构造和圈闭类型分为盐上、盐层(盐间)和盐下3种型式.盐上构造包括盐上滚动背斜、断弯-断展背斜、背冲断块、逆冲断层遮挡构造和盐推覆构造等;盐层(盐间)构造包括盐窿、断褶构造、鱼尾构造和盐间双冲构造等;盐下构造主要有背冲断块、断弯-断展背斜和盐下双重构造.羌塘盆地盐相关构造形成于侏罗纪末并在新生代进一步定型.根据盆地盐岩层分布和构造特点,将盆地分为盐上、盐层和盐下3种油气成藏模式,其中盐层和盐下是有利的油气聚集场所.

Salt-related structural characteristics and hydrocarbon accumulation in Qiangtang basin, Tibet, China

Salt beds of the Middle Jurassic are comprehensively developed in the Qiangtang basin. They restrict the deformation and trap styles of the basin. The salt-related structures and trap styles can be divided into suprasalt structure, salt bed structure and subsalt structure. The suprasalt structure includes suprasalt rolling anticline, fault-bending anticline, suprasalt pop-up, thrust screened structure and salt nappe. The salt bed structure includes salt bulges, interbed thrust-folds, fish-tail structure and intersalt duplexes. The subsalt structures mainly include subsalt pop-up, fault-bending anticline, subsalt duplexes. The salt-related tectonics in the Qiangtang basin mainly formed in late Jurassic and was further patterned during Cenozoic. Based on the salt beds distribution and the characteristics of salt-related structure, the hydrocarbon accumulation conditions and models of the Qiangtang basin can be divided into three accumulation styles of suprasalt, salt and subsalt horizons. Among them, the salt and subsalt horizons are the favorable place for hydrocarbon accumulation.