松南地区断－坳盆地油气成藏条件

松辽盆地属断、坳叠置型盆地。断陷成藏体系受断陷的分割性和沉陷强度控制,源岩以Ⅲ型、Ⅱ_B型为主,热演化程度较高,油气形成早,以天然气为主。油气主要以断裂为通道作垂向运移,但T₃,T₄界面侧向运移的调节、补充作用不能忽视。同生圈闭、早期构造圈闭、多期复合型圈闭是捕集油气的有利圈闭。由于圈闭规模小、源岩分散,后期构造改造较强,断陷成藏效率较低。坳陷盆地具有统一性和稳定性,源告分布稳定、面积大,主要为Ⅰ,Ⅱ_A型干酪根,整体演化程度较低,油气形成晚,以石油为主,伴生气次之。油气主要以T₁,T₂界面和储层的侧向运移为主导,叠置在古隆起、古斜坡之上的各类圈闭是最有利的圈闭,成藏效率高。

HYDROCARBON POOL-FORMING CONDITION OF FAULT-DEPRESSED BASIN IN SOUTH SONGLIAO REGION

Songliao Basin is a superposed basin composed of fault-subsidence and depression. The pool forming system of the fault-subsidence was controlled by faulting and subsiding intensity. The source rocks of the basin are mainly type-Ⅲ and type-Ⅱ_B of high thermal evolution. Hydrocarbon generation took place quite early and most of the hydrocarbon is natural gas. Hydrocarbon migrated vertically through faults and fractures associating with lateral migration along T₃, T₄ interfaces. Traps such as contemporaneous, early stage structural and multistage composite traps are favourable for trapping oil and gas. Since the traps are small,source rock are dispersive and posttectonic reworking was intensive, the pool-forming efficiency is quite low. As for the depressed basin, its source rock distribution is stable and extensive, the kerogens are primarily type-Ⅰand type-Ⅱ_A,and on the whole,the evolution degree of organic matter is lower. Hydrocarbon, mainly oil associated with gas, generated late in the depressed basin. Oil and gas in the basin migrated laterally along T₁, T₂ interfaces and reservoirs. Verious kinds of traps superposed on paleo-uplifts and paleo-slopes are more favourable to form oil and gas pools.