辽河断陷西部凹陷油气成藏主控因素

Main controlling factors of hydrocarbon accumulation in West Sag of Liaohe Rift Basin

辽河断陷西部凹陷的油气资源非常丰富,通过对已发现的773个油气藏地质特征参数的统计表明,西部凹陷油气藏类型非常丰富,但主要以构造油气藏和岩性油气藏为主,且复合油气藏发育,近90%的油气藏与断裂有关;油气藏类型受构造带控制明显,缓坡带主要以构造油气藏为主,中央背斜带多为构造油气藏或与构造有关的岩性油气藏,而陡坡带则多为岩性油气藏;沉积相带控制油气作用明显,油气藏主要分布在扇三角洲、三角洲和浊积扇相;油气资源在空间上遵循"油气总量平衡模式",无论在平面上还是层位上,油气资源互补性强。研究认为西部凹陷具有生烃洼陷、断裂、异常压力和沉积相带联合控藏的特点。油气藏分布主要受生烃洼陷控制,沙三段和沙四段有效烃源岩大量发育,资源量极为丰富,为西部凹陷油气富集提供了物质保证;各组段砂体叠合连片,平面展布连续,具较好的储集能力,也为油气的侧向运移提供了条件;东营组沉积末期因走滑引起的大量泄压断裂发育,为油气大规模远距离垂向运移提供了可能。

There is abundant oil and gas in the West Sag of Liaohe Rift Basin. According to the statistical analyses of the geological factors of 773 oil pools discovered, it is considered that there are various petroleum reservoir types in the West Sag, with structural and lithological oil pools being the dominant ones and numerous composite pools being present. The statistic data show that nearly 90% of the oil pools are related to faults. The types of petroleum reservoirs are significantly controlled by structural belts. There are mainly anticlinal and lithological-structural oil pools in the gentle slope belt, anticlinal and fault block oil pools in central anticlinal belt, and lithological petroleum reservoirs in steep slope belt. Petroleum reservoirs are obviously controlled by sedimentary facies, and are mainly distributed in fan delta facies, delta facies and turbidite fan facies. The spatial distribution of oil and gas resources follows ＂the model of total oil and gas resources balance＂, and shows obvious complementary characteristics both horizontally and vertically. According to this study, the distribution of oil pools is jointly controlled by hydrocarbon generating sag, faults, abnormal pressure and facies belts in the West Sag. The active source rocks in the Members 3 and 4 of Shahejie Formation are well developed and the resource quantity is very large. Thus they form the material sources for hydrocarbon accumulation and control the distribution of oil pools in West Sag ; The oil-bearing sandbodies of each formation and member are overlapped and continuously distributed, which is favorable for hydrocarbon lateral migration; The development of pressure releasing faults resulting from the strike-slipping during the late depositional period of Dongying Formation, made it possible for the oil and gas to make a large scale and long distance vertical migration.