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鄂尔多斯盆地西北地区樊学油区延长组长8油层砂体为灰褐色细、细-中粒长石砂岩,粒度概率呈曲线两段式,还有部分呈三段式,砂体内发育水平层理。结合研究区沉积作用、成岩作用及单井相分析,认为长8为湖泊三角洲沉积体系的三角洲前缘亚相,物源来源于北部或东北方向,主要发育水下分流河道、河道侧缘、分流间湾等微相。测井曲线形态以箱型、钟型及其组合为主,反映了水下分流河道微相比较发育,砂体在剖面上呈一系列旋回多次叠置,剖面上呈上平下凸的透镜体,垂向上具有向上变粗的层序,表明研究区湖盆沉积范围不断扩大,构成进积三角洲沉积。
The Chang 8 reservoir of the Yanchang Formation in the Fanchang oil-bearing area in the northwestern Ordos Basin is a beige, fine-medium-sized feldspathic sandstone with a two-step curve of particle size probability and some three-stage sand bodies with developed horizontal bedding . Based on the sedimentary facies, diagenesis and single-well facies analysis in the study area, Chang 8 is considered as the delta front of the delta system of the lake delta with provenance originating in the north or northeast direction. The main distributary channel, the lateral edge of the channel, the diversion Bay and other micro-phase. The shape of well logs is mainly box, bell and their combination, reflecting the relatively developed micro-facies of submarine distributary channel. The sand body presents a series of cycles superimposed on the section, There is an upward thickening sequence in body and vertical direction, indicating that the sedimentary scope of the lake basin in the study area has been expanding continuously to form the sedimentary delta.