鄂尔多斯盆地西北地区樊学油区延长组长8油层沉积相特征研究

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。

Study on Sedimentary Microfacies of Yanchang Formation Chang8 Reservoir in Fanxue District,Northwestern Ordos Basin

The oil sand of Chang8 reservoir of Yanchang formation in Fanxue district,northwestern Ordos basin is taupe fine, fine-grained feldspathic sandstone, grain size probability is curve two-stage form and partial three-part form. Combined with sedimentation in the study area, diagenesis and individual well-phase analysis, it’s pointed out that Chang8 reservoir is delta front facies of lake delta depositional system, the provenance of the north or northeast direction from mainly developed underwater distributary channel, river side edge, split between bay microfacies. Logging curve shape is box, bell-shaped and their combination, which reflects the micro underwater distributary channel development, sand bodies were stacked on a series of cycles repeated cross-section, formed flat convex lens on the profile body. In vertical, there is a coarsening-upward sequence, which indicates the scope of the study area sedimentary basin expanded to constitute deltaic sediments.