鄂尔多斯盆地东南部柴上塬区三叠系延长组长6致密油成藏主控因素及富集规律

鄂尔多斯盆地东南部柴上塬区位于中国陆上发现的第一个油田——七里村油田，主力含油层为三叠系延长组长6油层。目前，对该区长6致密油成藏主控因素还缺乏全面深入研究。在综合分析钻井、录井、电测井、岩心、试油、生产动态等资料的基础上，结合室内实验观测，并引入下伏砂地比和上覆泥地比概念，对研究区长6油藏成藏特征以及烃源岩、储层、构造、盖层、运移条件等因素对长6致密油藏的控制作用进行了全面剖析。研究区长6致密油藏为边底水不发育的岩性油藏，具有集群准连续分布特征，形成和分布受烃源、输导条件、储层、直接盖层四大因素控制，且四者对油藏的控制作用依次减弱。区内东部烃源较差，原油富集区为砂体发育较好的下段地层；而西部烃源较好，盖层和输导条件则更多控制着原油的富集程度，是否利于成藏取决于两者耦合关系的好坏。

Key controlling factors and enrichment mechanisms of tight reservoirs in 6th member of Triassic Yanchang Formation,Chaishangyuan area,southeastern Ordos Basin

Chaishangyuan area locates in the Qilicun Oilfield of the southeastern Ordos Basin, the first onshore oil field discovered in China, and its main layer for oil-producing is the 6th member of Triassic Yanchang Formation (Chang 6). At present, the comprehensive study on the key controlling factors of Chang 6 tight oil reservoir in this area is not clear. In this paper, a large number of drilling, logging, core, production test and other data, combined with laboratory experimental observation were carried out to progress the understanding of the factors controlling reservoir formation. In addition, the concepts of the ratio of underlying sand thickness to formation thickness and the ratio of overlying mud thickness to formation thickness were introduced to comprehensively analyze the forming characteristics of Chang 6 reservoir in the study area and the controlling effects of source rocks, reservoirs, structures, caprocks and migration conditions on Chang 6 tight reservoirs. The Chang 6 tight reservoir in the study area is a lithologic reservoir with undeveloped edge and bottom water, which has the characteristics of clustered and quasi-continuous distribution, and its formation and distribution were controlled by four factors: hydrocarbon source, transport condition, reservoir and direct caprock, and the controlling effect of the four factors on the reservoir is weakened in turn. In the eastern area where source rock quality is poor, crude oil was mainly enriched in the lower strata where sand bodies were well developed, while in the western area where source rock quality is relatively better, the enrichment of crude oil was more controlled by caprock and transport conditions. The better the coupling relationship between them, the more conducive to reservoir formation.