HYDROCARBON SHOW AND CORRELATION BETWEEN OIL ND SOURCE ROCK IN THE QIANGTANG BASIN

There are 4 sets of hydrocarbon source rocks in the Qiangtang Basin,including the Upper Jurassic Suowa Formation(J3s),the Middle Jurassic Xiali Formation(J2x),the Middle Jurassic Buqu Formation(J2b) and the Upper Triassic Xiaochaka Formation(T3x).Multi points of hydrocarbon show have been discovered in several locations,mainly including 3 types.The first type is the liquid oil seepage in fractures of limestone in the Upper Jurassic Suowa Formation,which was discovered at 114 Daoban,the east of Southern Qiangtang Depression.Four spots of heavy crude oil have been discovered in this area.The second one is seepage in oil-bearing dolostone,which is mainly distributed in the Middle Jurassic Buqu Formation of Longenixi area and the Upper Jurassic Suowa Formation of northern Angdaercuo area in the Southern Qiangtang Depression,and also,oil-bearing limestone and argillaceous dolomite in the Upper Jurassic Suowa Formation have been discovered in the west of the Northern Depression,Xiliangshan area.The last one is the bitumen,which is mainly distributed in the west of Northern Qiangtang Depression and the east of the central buried uplift.It is considered by comparison of geochemical methods that the liquid oil seepage of J3s limestone sources from the J3s micrite,the oil seepage of J3s and J2b oil-bearing limestones and dolostones originates from the J3s and J2x mud shale,and lots of bitumen in the Qiangtang Basin maybe originate from J3s and J2b limestone.