安塞油田侯市地区长6油层沉积微相研究

Sedimentary Microfacies of Chang-6 Reservoir in Houshi District,Ansai Oilfield

通过岩心描述和分析 ,确定了侯市地区长 6油层河控三角洲沉积体系 ,主要沉积微相为三角洲前缘分流河道、分流河口砂坝、前缘砂席和分流间等 ,分流河道和河口砂坝是本区占主导地位的骨架砂体 .在图像粒度分析的基础上 ,通过绘制概率累积曲线、C- M图、散点图和环境判别图 ,对该区砂体形成的水动力条件及形成环境进行了分析 .长 6油层的三角洲体系代表了较为完整的自旋回 ,这一自旋回形成的原因主要是分流河道迁移、袭夺、决口以及因压实的均衡调整等 ,从而形成三角洲复合体内部各分流三角洲砂体的相互叠置交错 .根据岩心微相分析、小层砂体形态和测井剖面对比分析 ,对该区长 6油层砂组及小层的沉积微相进行了研究 ,掌握了沉积微相的时空展布和变化规律 .

The origins of the main sand bodies in Houshi district of Ansai Oilfield are interpreted jointly with careful core descriptions and logging data. The Chang 6 petroleum reservoir horizons in this area are river dominated delta sandstones. The main sedimentary microfacies include distributary channel,distributary mouth bar,front sand sheet, and interdistributary deposits. The distributary channel and distributary mouth bar sands constitute the dominated reservoirs.Grain size distributions of the sandstones are investigated by measurements in thinsections. The overall grain size distributions are characteristic of delta sands on the basis of cumulative curve, skewness standard deviation, C M pattern, and other distinction approaches. Delta switching, together with regional subsidence,produced cyclic alternations of distributary and interdistributary deposits in the area. Progradation of distributaries constructed at first only a delta skeleton. Rapid deposition of sediment did not block the distributary mouths but lead to rapid progradation basinward of distributary mouth bars and produced long, straight distributaries. The distributary channels cut through silts and sands deposited in distributary mouth bars.The sand deposited at the distributary mouths was readily redistributed to form a delta front sand sheet.Consequently, the development of deltaic sedimentation produced in detail based on depositional sequence and sand body geometry.