海拉尔盆地乌尔逊-贝尔凹陷油气富集规律及主控因素分析

Rules and main controlling factors of hydrocarbon enrichment of Urxun——Beier Depression, Hailar Basin

在含油气系统划分的基础上,对油气富集区带进行刻画,分析总结海拉尔盆地乌尔逊—贝尔凹陷的油气富集规律及控制因素。研究结果表明:海拉尔盆地乌尔逊—贝尔凹陷油气藏具有两期成藏,伊敏组晚期烃源岩大量排烃,控制早期原生油藏的形成,伊敏组末—青元岗组沉积时期盆地反转,受活动断层调整形成次生油藏。纵向上发育中下部两套含油气系统(被动裂陷含油气系统与主动裂陷含油气系统)和一套上部含油组合,油主要分布在被动裂陷含油气系统。油气分布的主控因素可概括为3个方面:(1)"断-盖"共控油气富集层位,盆地发育南一段上部和大一段两套区域性优质泥岩盖层,控制了中下部含油气系统油气富集。晚期盆地反转,部分断裂活动使得油气穿越盖层运移至大磨拐河组形成次生油藏;(2)"源-储"共控油气分布范围,中下部含油气系统均发育一套烃源岩,其中南一段中部源岩为优质源岩。受大气水淋滤和有机酸溶蚀作用部分区域发育优质储层,烃源岩与优质储层的时空配置控制了油气的分布范围,油气以短距离侧向运移为主,洼陷中生成的油气优先在附近优质储层中聚集。(3)"断-隆-扇"共控油气聚集部位,中央背斜带控制潜山油藏聚集,滚动背斜带控制形成构造油藏,反向断层下盘掀斜隆起带与中央隆起带控制中下部含油气系统油气聚集,受反转构造影响活动的断裂控制上部含油组合油气聚集,近岸水下扇及三角洲前缘砂体控制洼漕中心油气成藏形成岩性油气聚集带。

Based on the division of petroleum systems, oil-gas prolific zones were characterized, and the hydrocarbon enrichment rules and main controlling factors of reservoirs of Urxun--Beier Depression, Hailar Basin were analyzed. The research proves that petroleum accumulation has two stages. During the middle to late period of the Yimin Formation （K1y） sedimentation, oils derived from the source rock, and the primary reservoirs formed. At the end of the Kly and Qingyuangang Formation （K2q） sedimentation, inversion occurred in the basin, resulting in a strong movement of faults,and forming secondary oil pools later. There are two petroleum systems （passive rift petroleum system and active rift petroleum system） and the upper oil-bearing combination, with the oil is mainly distributing in the passive rift petroleum system. There are three major controlling factors of oil and gas distribution. First of all, the regional cover and fault control the layer of hydrocarbon accumulation. The basin has two mudstone regional covers--Upper Nan-1 section and Da-1 section, which controlled the oil and gas accumulation in middle and lower petroleum systems. When basin reversed, oil and gas could vertical migrate through the regional cover to Damoguaihe formation（K^d） by active faults, forming secondary reservoir. Secondly, the effective hydrocarbon kitchen and good reservoir control the range of oil and gas distribution, while middle and lower petroleum systems both develop a set of hydrocarbon source rock. Middle Nan-1 section bed is high-quality source rock. The role of atmospheric water washout filter and organic acid dissolution is to form a high-quality reservoir. Oil and gas occur a short distance lateral migration. The hydrocarbon generated in the depression at the early stage has preferentially migrated and accumulated to the adjacent high-quality reservoir. The third is that the antithetic fault, the uplift zone and the fan complex control the hydrocarbon accumulation. Central anticlinal belt controlled hydrocarbon accumulation of Buried hill Reservoirs. Small Rollovering anticline controlled hydrocarbon accumulation of Structural Oil Reservoir. The tilted block at footwall of backward faults and the central uplift zone controlled hydrocarbon accumulation of middle and lower petroleum systems. Active fault affected by basin inversion controlled hydrocarbon accumulation of the upper oil-bearing combination. The Nearshore subaqueous fan and Delta front sandbody accumulate hydrocarbon in the central of depression, and form the lithologic reservoirs.