吉木萨尔凹陷芦草沟组异常高压与致密油富集

Abnormal High Pressure and Tight Oil Enrichment of Lucaogou Formation in Jimusaer Sag

准噶尔盆地吉木萨尔凹陷中二叠统芦草沟组致密油藏具有良好的油气资源潜力,其富集机理与常规油气藏有很大差异。通过计算吉木萨尔凹陷芦草沟组流体压力,建立了芦草沟组的异常高压分布体系,结合芦草沟组地质条件、地球化学化验分析、重点井试油情况,探讨异常高压与致密油藏富集的关系。结果表明,吉木萨尔凹陷芦草沟组油藏具典型的源储一体式结构,优质烃源岩在低成熟—成熟阶段生成的致密油,在烃源岩层内自生自储或在烃源岩层间短距离运移,是异常高压形成的主要原因。芦草沟组烃源岩和储集层普遍发育异常高压,横向上稳定连片,展现出一定的"层控"特征;纵向上不同层段有机质丰度及生烃能力的差异导致异常高压分布不均,存在明显的层间剩余流体压力差。剩余流体压力为致密油垂向运移的主要动力,层间高剩余流体压力差分布带是致密油的有利富集区。

The tight oil reservoir of the Middle Permian Lucaogou formation in Jimusaer sag is of good hydrocarbon potential. Its enrich-ment mechanism is greatly different from that of conventional oil-gas reservoirs. This paper calculated the fluid pressure of this formation,established the abnormal high pressure distribution system of it, and combined with the geologic conditions, geochemical analysis and for-mation testing of key wells, it discussed the relationship between the abnormal high pressure and tight oil enrichment. The results show thatthe Lucaogou reservoir is of typical source-reservoir structure, and the tight oil generated from high-quality source rocks in low mature-ma-ture stage is characteristic with both source and reservoir within the source rocks, and migrates in short distance between source rocks,which is the main reason for forming the abnormal high pressure. Such abnormal high pressure is widespread in the source rocks and thereservoirs, with lateral stability and connectivity, showing a certain stratabound characteristic; with longitudinal differences in organic mat-ter abundance and hydrocarbon-generated ability in different strata, resulting in uneven distribution of the abnormal high pressure, indicat-ing that there exists distinct remained fluid pressure of interlayers. Such a remained fluid pressure could be the main force for the tight oilvertical migration, and the distribution belt of big difference of the remained fluid pressure of interlayers might be the favorable area fortigh oil enrichment.