内蒙古二连盆地岩性油气富集因素分析

根据近年来在内蒙古二连盆地有关岩性油藏方面取得了很多勘探成果,通过对4个主力凹陷的岩性油气富集因素进行分析,认为形成岩性油气富集的3大主要因素是:(1)丰富的油源;(2)优质的砂岩体圈闭;(3)存在汇流通道。丰富的油源是油气富集的物质基础,二连盆地发育的2套有效烃源岩层系厚度大、分布面积广、资源规模大,与储集砂体之间具多种接触关系。优质的砂岩体圈闭具有圈闭规模大、发育有利的储集相类型和良好储集层的特点,这些是油气富集的关键因素。圈闭规模大表现为单一大规模砂岩体圈闭或多个小型圈闭叠合连片,扇三角洲、辫状河三角洲和湖底扇是有利的储集相类型,油气富集往往形成于良好的储集层中。此外,存在汇流通道是油气富集的重要因素,充足的油气通过指状砂体侧向汇流通道和断层垂向汇流通道运移,在优质的砂岩体圈闭中聚集成藏。

Analysis of Lithological Hydrocarbon Enrichment Factors in Erlian Basin,Inner Mongolia

Based on exploration achievements of lithological reservoirs in Erlian Basin,the hydrocarbon enrichment factors are analysed in four primary sags.Lithological hydrocarbon enrichment factors include luxuriant(oil-source,) high quality sand-body trap and confluence pathway.The luxuriant oil resources are substantial base of hydrocarbon enrichment,because there are two sets of source rocks with huge thickness,widespread distribution,large resource extent and several relationships to sandbodies in Erlain Basin.The high quality sand-body trap is characteristic of a large-scale trap,having furthersome types of reservoir facies and favorable reservoir,which are key factors for hydrocarbon enrichment.The analysis of the high quality sand-body trap's characteristics suggests that large-scale traps include single large-sized sand-body trap and several overlaying small-sized(lithological) traps;furthersome reservoir facies involve fan delta,braided river delta and sublacustrine fan;the hydrocarbon enrichment usually forms in favorable reservoirs.Furthermore,abundant hydrocarbon enriches in high quality sand-body traps by lateral confluence pathway in digitiform sand and fault vertical confluence(pathway).