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鄂尔多斯盆地是国内大型内陆坳陷盆地,在延长组富集大量的原油。近年来,随着勘探的深入,在盆地中部的长9油层组发现大量的工业油流,具有较大的勘探潜力,但是油藏分布东西向差异较大。通过对西部和东部2种储层的矿物成分、沉积相类型及砂体分布特征进行对比分析,证明研究区存在2种不同结构的砂体类型:西部砂体单层厚度大,纵向多层叠加,顺物源方向连续性较好,东部砂体单层厚度薄,纵向泥质夹层发育,顺物源方向连续性较差,砂体分布相对孤立。并对2种砂体类型的成因环境进行了分析:西部砂体主要发育在盆地西部的辫状河三角洲沉积体系,在近物源、高能量、物源供给充足的条件下,河流入湖后河道的能量大于湖水的顶托作用,河道继续向前延伸,形成条带状的厚层垂向叠置砂体;东部砂体主要发育在盆地东北曲流河三角洲沉积体系,是在坡缓水浅、远物源、低能量的缓慢沉积条件下,湖水能量和河道入湖能量彼此强弱交替,形成了单层厚度薄且不连续的砂体。
The Ordos Basin is a large-scale inland depression basin in the country, enriching a large amount of crude oil in the Yanchang Formation. In recent years, with the deepening of exploration, a large amount of industrial oil flow is found in the Chang 9 oil-bearing formation in the central part of the basin, which has great potential for exploration. However, the distribution of oil and gas in the reservoir is quite different from east to west. By comparing the mineral composition, sedimentary facies types and distribution characteristics of sandstone in the two kinds of reservoirs in the west and east China, it is proved that there are two types of sand bodies with different structures in the study area. The thickness of single layer in the western sand body is large, , The continuity of the source material is good, the thickness of the monolayer in the east sand body is thin, the longitudinal muddy interbed is developed, the continuity of the source material is poor, and the sand body is relatively isolated. The origin of the two types of sand bodies is analyzed. The western sand body is mainly developed in the braided river delta depositional system in the western part of the basin. Under the conditions of near-provenance, high energy and abundant source materials, The energy of the river channel is greater than that of the lake water, and the river channel continues to extend forward to form a strip-shaped, thick vertical superimposed sand body. The eastern sandstone body is mainly developed in the meandering delta river sedimentary system in the northeast of the basin, Under the conditions of shallow, distant source and slow energy deposition, the energy of the lake and the energy entering the lake alternate with each other to form a thin and discontinuous sand body with a single layer.