柴达木盆地西部南区第三系岩性油藏勘探与实践

Exploration and Practice of Tertiary Lithologic Oil Reservoir in South Area of Weatern Qaidam Basin

综合研究表明,柴达木盆地西部南区第三系岩性油藏具良好的成藏条件,表现在:现今构造格局和古构造发育区控制着岩性油藏的分布;三大沉积体系(阿拉尔河流—三角洲—滨湖沉积体系、阿尔金冲积扇—扇三角洲—半深湖沉积体系、昆仑山—冲积扇—河流—滨浅湖沉积体系)及有利砂体(水退体系域的河流、三角洲和扇三角洲砂体)展布控制着岩性油藏的富集;富油凹陷及油气运聚方向控制着岩性油藏的形成。经过近年来的勘探实践,提出了一套适合该区地质特征的岩性油藏勘探方法,具体步骤包括:沉积背景分析、层序划分对比、层序界面追踪、沉积相综合分析、等时储层预测、目标评价与成藏规律分析。勘探结果表明,阿尔金山前的扇三角洲沉积体系、红柳泉—跃进地区湖泊沉积体系和跃进地区的河流—三角洲沉积体系形成的砂体,具有形成岩性油气藏的有利条件,是该区下一步岩性油气藏勘探的有利区域。

Integrated research results show that the Tertiary lithologic oil reservoir in south area, western Qaidam Basin,has favorable reservoir-forming conditions, exhibiting the distribution of lithologic oil reservoirs is controlled by the present structure framework and paleo-structure developed area; The distribution of three depositional systems, including Ala'er fluvial-delta-lakeshore;Alerjin flooding fan-fan delta-half-deep lacstrine facies;Kunlunshan mountains flooding fan-fluvial-shallow lakeshore depositional system, and the favorable sandbodies formed in fluvial,delta and fan delta regressive system tracts controlled the enrichment of lithologic oil reservoirs; The oil-enrichment sags and the direction of oil-gas migration and accumulation controlled the formation of the lithologic oil reservoirs. After the exploration practice in recent years,it is proposed that a set of exploration method suited to the geologic features of lithologic oil reservoir in this area￡?including the analysis on sedimentary background, stratigraphic sequence division and correlation,sequence boundary tracing, comprehensive analysis of sedimentary facies, target evaluation and analysis on the regularity of reservoir- forming. Exploration results show that the sanbodies, formed in the fan-delta depositional system in foreland Alerjin, Hongliuquan-Yuejin lake depositional system and fluvial delta depositional system in Yuejin area, has the advantages to form the lithologic oil reservoirs and will become the promising target for next exploration in this area.