我国鄂尔多斯盆地合水长8油藏储层特征及开发潜力

Reservoir Property and Exploration Potential Analysis of Chang 8 Member in the Heshui Area, Ordos Basin, China

本文针对鄂尔多斯盆地合水地区长8油藏北部富集好而南部富集差,油藏向南扩展困难的问题,运用大量的现场岩心资料、测井解释成果、薄片镜下鉴定和储层物性测试数据,对合水南北长8段储层的岩石学特征、孔喉结构特征、物性特征和成岩作用等进行了对比分析,明确了合水南北长8段储层含油性差异的控制因素。结果表明,研究区长8段储集层整体物性偏差,属于特低孔–超低渗储层,主要发育粒间孔和长石溶孔,见少量晶间孔和微裂缝;由北向南石英、岩屑含量逐渐增大,而长石含量逐渐减少;较合水南部,合水北部的孔喉结构和储层物性更好。在此基础上,总结和分析了研究区成藏控制因素,显示油藏在平面上的分布与优质储层和长石溶蚀相在平面上的分布具有密切联系,合水南部不具有连片开发的潜力,但小规模的甜点区仍可作为下一步的开发目标。

The exploration of Chang 8 member of Yanchang formation in the north of Heshui area has made a great breakthrough, forming a contiguous oil-bearing area. But the exploration in the south of Heshui area is poor, and the reservoir is difficult to expand to southward. For this problem, this paper compares and analyzes the petrological characteristics, pore throat structure characteristics, physical characteristics and diagenesis of the Chang 8 reservoir in north and south of Heshui area, and identifies the accumulation controlling factors, basing on a large number of core observation, well logging interpretation, microscopic identification of thin sections and reservoir physical property. The results show that the overall physical properties of the Chang 8 reservoir in the study area are deviated, which belongs to an ultra-low porosity and ultra-low permeability reservoir. There are mainly intergranular and feldspar dissolution pores, and a few intercrystalline pores and microcracks. From north to south, the content of quartz and cuttings increased, while the content of feldspar decreased gradually. Comparing to north of Heshui area, the pore-throat structure and reservoir physical properties are better than those in the south of Heshui area. On this basis, the control factors of reservoir formation in the study area are summarized and analyzed, showing that the distribution of oil is closely related to the high-quality reservoir and diagenetic facies. There is no potential for continuous development in the south of Heshui area, but part of the dessert area can still be used as the next development target.