松辽盆地幔源成因CO_2气藏分布规律及控制因素

Distribution Law of Mantle-Origin CO_2 Gas Reservoirs and Its Controlling Factors in Songliao Basin

通过深部15s大剖面解译和典型CO2气藏解剖,深入剖析了松辽盆地幔源成因CO2气藏分布规律及控制因素。纵向上CO2气主要富集在营城组火山岩和泉头组三、四段砂岩储层中。与深部热流体(热流底辟体和侵入体)直接相连的、控陷的、控制火山通道的铲式基底断裂控制着CO2气藏呈串珠状分布的特征,断裂走向拐点、端点和侧列叠覆区控制了CO2气出气点。深部热流体是CO2气藏主要的气源。与之相衔接的基底断裂活动导致幔源岩浆充注盆地,同时携带的CO2气释放进入早期喷发的火山岩中形成营城组火山岩CO2气藏。基于控藏断裂多为断陷期和泉头组晚期—青山口组早期活动的基底断裂,推测营城组CO2气藏主要成藏时期为泉头组晚期—青山口组早期。松辽盆地强烈的构造反转发生在明水组末期,挤压应力自南南东向北北西方向衰减的过程中,基底断裂复活形成正反转断层,CO2气从热流底辟体中脱出上运而聚集在反转构造带上,断层式反转构造南部比北部发育,西部比东部发育,因此松辽盆地南部比北部、西部比东部CO2气更富集。

Based on the interpretation of 15s deeper seismic profiles and the anatomy of typical CO_2 gas reservoirs,the distribution law of CO_2 gas reservoirs and its controlling factors have been deeply analyzed in the Songliao basin.Vertically,CO_2 is mainly rich in volcanic rocks of the Yingcheng Formation,and sandstone reservoirs in 3th and 4th Members of Quantou Formation.The beaded distribution feature of CO_2 is mainly dominated by lystric basement faults which are in direct contact with deep thermal fluid： heat-flow diapirs and intrusions,and are depression-controlling and volcanic vent-controlling.Meanwhile,outlet points of CO_2 are controlled by strike infection-points,endpoints and overlap zones of these faults.And CO_2 mainly comes from the deep thermal fluid.The activity of basement faults connected with thermal fluid led to the basin filling by mantle-derived magma,at the same time,the carried CO_2 was released into volcanic rocks erupted earlier and then developed into volcanic CO_2 gas reservoirs of Yingcheng Formation.Considering that faults controlling gas pool are usually basement faults which were active during fault-depression phase and the Late Quantou Formation to the Early Qingshankou Formation,it was speculated that CO_2 reservoirs of Yingcheng Formation were mainly formed between the Late Quantou Formation and the Early Qingshankou Formation.In Songliao basin,the stronge tectonic inversion occurred in the Late Mingshui Formation,and during the declining of compressive force from the SSE to the NNW,the reactivation of basement faults formed positive inversion faults;released from thermal fluid diapirs,CO_2 was migrated upward and then accumulated in inversion structural belts;as the development of fault-style inversion tectonics in the southern part is better than the northern part,and the western is better than the eastern part,CO_2 is richer in the south than in the north,richer in the west than in the east in Songliao basin.