马来盆地前I群油气成藏条件及富集规律

FORMING CONDITIONS OF HYDROCARBON RESERVOIR AND OIL ENRICHMENT MECHANISMS OF PRE-I GROUP(OLIGOCENE-LOWER MIOCENE) IN MALAY BASIN

马来盆地前I群(即J、K、L、M群,渐新统—下中新统)具有良好的油气成藏条件:①发育多期有利于成藏的构造运动:前中新世伸展断裂阶段,湖相烃源岩大量发育;早、中中新世构造沉降阶段,并伴随盆地反转,形成前I群油气系统的储盖系统;②烃源岩优越:烃源岩为湖相富含藻类的页岩,成熟度较高,有机质含量较高;③储集层丰富:K群储集层为辫状河砂岩,J群储集层为河口湾河道砂岩和潮间砂岩;④盖层良好:主要盖层为盆地海侵期沉积的前J群三角洲—浅海相泥岩,次要盖层为K、L和M群内的湖泊相泥岩;⑤油气运移通道畅通:上倾侧向运移为主;⑥有利的生储盖组合:自生自储和下生上储的组合方式有利于油气藏的形成。前I群油气系统位于马来盆地的东南部,以生油为主。分析认为盆地的油气分布主要受烃源岩的分布、质量和成熟度以及构造圈闭形成的相对时间和油气运移方式的控制。

The J、K、L and M groups（Pre-I group,Oligocene-lower Miocene）have good conditions for hydrocarbon accumulation in the Malay Basin.①Tectonic movements favor the accumulation of hydrocarbon.In early Miocene,the stage of extensional fracturing,numerous lacustrine source rocks were deposited.In early-middle Miocene,the stage of tectonic subsidence,accompanied by basin inversion,reservoir and seal systems of the Pre-I group’s petroleum system were formed.②The lacustrine deposits are excellent source rocks,which are rich in algae and have higher maturity and organic content.③Reservoirs are available,such as the braided river sandstone in the K group and the estuarian channel sandstone and intertidal sandstone in the J group.④Cap rocks are well developed.The main cap rock of Pre-I group is the delta-shallow marine mudstone deposited in the transgressive period of the Basin.The secondary cap rock is the lacustrine mudstone in K、L and M groups.⑤Migration pathways are still open.Both upward and lateral migration occurs ⑥The source-reservoir-seal assemblages are favorable.Both the self generation and self preservation assemblage and lower generation and upper preservation assemblage occur,which are favorable to oil and gas accumulation.The petroleum system of Pre-I group is located in the southeastern part of the Malay Basin.The oil and gas distribution in the Malay Basin is controlled by the distribution、quality and maturity of source rocks、forming time of structures and the migration of hydrocarbon.