官渡构造带下沙溪庙组砂体展布特征研究

Sand distribution in lower Shaximiao formation of Guandu structure belt

(1.成都理工大学“油气藏地质及开发工程”国家重点实验室，四川成都610059；2.中国石油化工股份有限公司勘探南方分公司，四川成都610041)

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China

利用官渡三维地震资料和钻井、测井资料，对官渡构造带下沙溪庙组层序、沉积相展布特征及砂体分布规律进行了综合研究。首先在单井层序、沉积相划分与联井剖面对比的基础上，结合三维地震资料，开展了沉积相平面展布研究；然后利用砂体的自然伽马响应特征，结合研究区实际情况，选取伽马值90 API作为砂体反演的上限，对下沙溪庙1砂组和2砂组进行了反演预测。研究表明，该区下沙溪庙组可划分为3个长期旋回，11~12个中期旋回，主要为河流控制的三角洲—湖泊相沉积环境，储层砂体均位于长期旋回的上升半旋回底部，砂体发育程度严格受沉积相带展布控制：早期主要为三角洲平原沉积，河道摆动迁移频繁，使河道砂体叠置连片分布；晚期发育三角州前缘沉积，水下分流河道砂体发育，河道化程度高，使得砂体呈带状展布。

Based on logging, drilling，and seismic data of the 3-D area in Guandu area, through seismic facies and sedimentary facies analysis, we used the reservoir inversion technology to comprehensively study the sequences, sedimentary feature and sand distribution laws. Firstly, based on the classification of sequence and sedimentary facies in a single well and joint profile comparison, combined with 3-D seismic data, the plane distribution of sedimentary facies was studied. Then, according to the response characteristics of natural gamma ray of sand bodies and the actual conditions of the working area, 90 API was selected as the upper limit of sand inversion to inverse the first and second sand set of the lower Shaximiao formation. The result indicates that 1) the lower Shaximiao formation can be divided into three long sequence cycles, eleven to twelve middle sequence cycles, 2) the lower Shaximiao formation is mainly the delta-lake sedimentary environment controlled by rivers and the reservoir sand body lies in the bottom of upward semi-cycle in long sequence cycle, and 3) the developing degree of sand bodies is strictly controlled by the distribution of sedimentary facies belt. In the early stage, the sedimentary facies is mainly the delta plain and rivers sway, moving frequently and causing the overriding and merging distribution of channel sand bodies. In the later stage, the sedimentary facies is mainly the delta front, making the underwater sand bodies well developed with zonal distribution.