鄂尔多斯盆地西南边缘地区长8段充注成藏模式南北对比

Comparison of accumulation model of Chang-8 reservoirs between Huanxi-Pengyang area in southwestern Ordos Basin

鄂尔多斯盆地长8段油层在区域上含油性差异显著,但勘探潜力巨大。在鄂尔多斯盆地西南缘成藏地质背景研究的基础上,开展环西与彭阳地区油藏形成控制因素攻关研究和成藏模式系统对比,总结成藏模式,为明确该区油气勘探潜力,预测有利区带提供理论支持。通过试油资料、岩心观察、薄片鉴定、有机地球化学与定量颗粒荧光技术分析等技术手段,从环西与彭阳地区延长组8段低渗透致密油的沉积储层、油藏特征差异着手,分析了南北充注成藏差异及石油富集主控因素。结果表明:区内南北油藏特点及成藏条件差异较大,南部彭阳烃源岩厚度较大、生排烃条件相对有利,加上整体物性较好,相比北部环西更有利于油气充注富集;但彭阳构造调整或破坏作用较强,使油气分布进一步复杂化。综合成藏条件与主控因素研究建立了区内长8段成藏模式,南部彭阳地区为垂向运移成藏模式,北部环西靠西地区主要表现为侧向运移成藏模式。

There’s large differences in oil bearing characteristics of Chang-8 reservoirs in different regions of southwestern Ordos Basin.The exploration potential is great.Studies on major control factors of oil accumulation and enrichment mode of Huanxi-Pengyang area have been carried out on the basis of fundamental oil formation condition analysis in southwestern margin of Ordos Basin to provide a theoretical support for the determination of oil exploratory potential and prediction of favorable zones.By the methods of formation test,logging and core analysis,organic geochemistry and thermodynamic simulations on the fluid inclusions,the migration and accumulation characteristics and major controlling factors of oil enrichment in Huanxi-Pengyang area is systematically analyzed based on the difference in sedimentary reservoir and reservoir characteristics of Chang-8 low-permeability tight reservoir.The results show that there is big difference exists in the features and formation conditions between north and south reservoir.As the source rock thickness is greater and hydrocarbon generation and expulsion conditions is better,and the overall physical property is good,it’s more favorable for oil charge and accumulation in Pengyang than that in Huanxi area.But structural adjustment influence secondary oil-gas migration or damage in southwestern margin contrast to basin center,resulting in more complex oil distribution.Thus,the oil-gas accumulation model of the Pengyang and Huanxi is further established while the former belongs to vertical hydrocarbon migration pattern and the latter lateral pattern.The research results provide significant guidance for next step of petroleum exploratory orientation evaluation and development for Chang-8 reservoirs in marginal areas of Ordos Basin.