摘要
延长组6段（长6段）是鄂尔多斯盆地姬塬地区石油勘探的重要目的层。其油层埋深大、油-水关系复杂，油藏在垂向和平面分布上具有明显的差异性。利用大量岩心观察、铸体薄片和试油等资料，结合包裹体和原油生物标志化合物等地化资料，对姬塬地区长6段油藏地质特征进行了对比分析，并对油藏的差异富集因素进行探讨。研究结果表明，油源条件、砂体类型和储层物性是控制长6段油藏差异富集的关键因素。优质烃源岩、优势砂体和相对高渗区3个有利因素的叠加效应，形成了长6段油藏的富集区。受沉积环境影响，垂向上，姬塬地区长6段的3个亚段中长6亚段砂体厚度大，砂体类型以Ⅰ类为主，横向分布稳定，延伸较远，储层喉道半径较大，物性较好，油气富集程度最高；平面上，东、西部砂体具有厚度大、类型好、泥质夹层少和物性好的特征，加之区内烃源岩厚度大，供烃能力强，是源-储配置有利的成藏区带。姬塬地区中部砂体厚度虽大，但单层砂体薄且层数多，泥质夹层多，储层非均质性强，区内烃源岩厚度较薄。因此，中部储层物性虽较好，但区内储层含油性较差，以产水井为主。
Abstract
The 6 Member of Yanchang Formation (Chang 6 Member) is a key target layer for petroleum exploration in Jiyuan area, Ordos Basin.The reservoirs of Chang 6 Member are characterized by large burial depth and complex oil-water contact, resulting in markedly differential distribution both vertically and laterally.In order to find out the factors causing the differential enrichment of reservoirs in the study area, we make a comparative analysis of the geological conditions based on core and casting thin section observation, formation testing, and geochemical analysis of inclusions and crude oil biomarker compounds.The results show that the key factors of differential enrichment are the source rock quality, type of sand bodies and physical properties of reservoirs.As a result, high-quality source rocks, favorable sand bodies and relatively high permeability, work in unison to generate the enriched zone of Chang 6 reservoirs.In the particular sedimentary environment, vertically speaking, the Chang 6 submember with the thickest sand bodies dominated by Type Ⅰ and in steady lateral distribution, features larger radius of throats, better physical properties, high hydrocarbon abundance in the reservoirs; in planar view, sand bodies developed in the east and west of the study area, feature large thickness, favorable type, less argillaceous interlayers, and better physical properties.In addition, source rocks have large thickness and strong hydrocarbon generation capacity, so they are favorable play fairways with favorable source-reservoir configuration.While the sand bodies of large thickness in central Jiyuan area are characterized by multiple beds thin for each single, multiple argillaceous interlayers, strong reservoir heterogeneity, and the source rocks are thin, so although the reservoirs therein are of better physical properties, their oil-bearing properties are poor, with most wells producing water.
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