辽河西部凹陷新生代断裂构造特征与油气成藏

Cenozoic fault structure and hydrocarbon accumulation in Western Sag,Liaohe Depression

为了揭示辽河坳陷西部凹陷新生代断裂构造与油气关系,运用油区构造解析理论对西部凹陷新生代断裂构造发育及演化特征进行系统分析。结果表明:以沙三段中下部大套泥岩为界,西部凹陷形成了上下叠加的2个断裂系统,主要发育长寿型、早衰型和后生型3种类型断层和张性正断层、走滑断层、走滑正断层和走滑逆断层4类不同性质断层。断裂活动控制了西部凹陷烃源岩的分布与演化、油气的运聚以及圈闭形成:断陷期是主要的烃源岩形成期,持续沉降有利于烃源岩演化;伸展变形阶段形成的下部断裂系统有利于油气的聚集,走滑变形阶段发育的上部断裂系统有利于油气的运移;构造活动强烈期是圈闭主要形成期,在沙四段—沙三段沉积早期及东营组沉积晚期形成两期主体圈闭。根据断裂发育特征和演化过程,指出双西隐伏走滑断层带和台安—大洼断层带的海外河以南部分是有利勘探区。

To reveal the relationship between the Cenozoic fault structure and the hydrocarbon of the western sag in the Liaohe Depression,a systemic analysis is carried out on the development and evolution of the fault structure using the theory of oilfield structural analysis.Divided by mudstones of the middle and lower parts in the Sha-3 Member,two superimposed fault systems are formed in the Cenozoic strata in the western sag,including long-term active faults,presenile active faults and late-developed active faults,which,in origin,are extensional normal fault,strike-slip fault,strike-slip normal fault,strike-slip reverse fault.The fault activity controls the distribution and evolution of the source rock,hydrocarbon accumulation and trap formation： the period of faulting and depression is the main forming time of the source rock,continuing subsidence is favorable for the source rock evolution;the lower fault system formed in the extensional deformation period is good for hydrocarbon accumulation,while the upper fault system formed in the strike-slip deformation period is beneficial to the migration of oil and gas;the timing of trap formation accords with the intensive structure activity periods,and the majority of traps are formed in the early time of Sha-4 Member to Sha-3 Member and the late period of Dongying Formation.The Shuangxi subtle strike-slip fault and the south of Haiwaihe in the Tai＇an-Dawa fault are favorable plays.