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利用测井、岩心、薄片等资料,从储层沉积学的角度对比研究了姬塬地区和陕北地区长81水下分流河道砂体的迥异性。研究表明:2个地区砂岩均为岩屑长石砂岩和长石岩屑砂岩,属于细砂岩和极细砂岩,但陕北地区砂体粒度比姬塬地区更细,分选更好。姬塬地区砂体厚度大、泥质含量低,叠加期次不明显,垂向和纵向上连续性好;而陕北地区砂体单层厚度薄、泥质含量高,具有明显的多旋回性,垂向和纵向上连续性差。姬塬地区长81属于浅水沉积环境,近物源、物源供给相对稳定且充足,湖水扩张动力大于河流入湖动力,形成了“连续退积式”的厚层砂体;而陕北地区长81同样属于浅水沉积环境,湖水水体相对姬塬地区浅,远物源、供给量稳定但不充足,湖水扩张动力和河水动力均较弱,形成了“拉锯式”的薄层砂体。2个地区砂体孔隙以粒间孔和长石溶孔为主,整体上姬塬地区长81水下分流河道砂体储集性能优于陕北地区,但是陕北地区长81水下分流河道砂体同样具备油气储集能力。
From the perspective of reservoir sedimentology, the heterogeneity of sand bodies in the Jiuyuan area and the Chang 81 subaqueous distributary channel in northern Shaanxi is studied by using well logs, cores and thin slices. The results show that the sandstone in both areas are feldspar feldspathic sandstone and feldspathic lithic sandstone, belonging to fine sandstone and very fine sandstone. However, the grain size of sand body in northern Shaanxi is finer and the sorting is better. The thickness of sand body in Jiyuan area is large, the content of shale is low, the period of superposition is not obvious, and the continuity in vertical and vertical direction is good. However, the monolayer of sand body in northern Shaanxi is thin and thick, with obvious multi-cycle , Vertical and vertical continuity is poor. The length of 81 in Jiyuan area belongs to the shallow water sedimentary environment. The supply of near-provenance and provenance is relatively stable and sufficient, and the driving force of water expansion is greater than that of river flowing into the lake, forming a thick sand body of “continuous retrogradation” The region 81 also belongs to the shallow sedimentary environment. The lake water is relatively shallow and far from the Jiyuan region, and the supply is stable but not sufficient. The lake expansion power and the hydrodynamic force are weak, forming a “see-saw type” thin sand body. The sand bodies in the two regions are dominated by intergranular pores and feldspar dissolved pores. Overall, the reservoir performance of Chang 81 underwater distributary channel sand body is better than that of northern Shaanxi. However, the long 81 submarine distributary channel Sand body also has oil and gas storage capacity.