四川盆地寒武系洗象池组滩相白云岩规模储层发育特征及勘探意义

Characteristics and exploration prospect of dolograinstone beach reservoir in Xixiangchi Formation, Cambrian, Sichuan Basin

石书缘 胡素云 汪泽成 文龙 徐祖新 刘伟 谢武仁 姜华 卞从胜 刘静江 陆彬 苏旺 冯庆付 周刚 郝涛

SHI Shuyuan HU Suyun WANG Zecheng WEN Long XU Zuxin LIU Wei XIE Wuren JIANG Hua BIAN Congsheng LIU Jingjiang LU Bin SU Wang FENG Qingfu ZHOU Gang HAO Tao

中国石油勘探开发研究院, 北京 100083 中国石油 西南油气田公司 勘探开发研究院, 成都 610000 中国石化 勘探分公司 勘探研究院, 成都 610041 南方石油勘探开发有限责任公司, 海口 570216

Research Institution of Petroleum Exploration & Development, PetroChina, Beijing 100083, China Exploration and Development Institute of PetroChina Southwest Oil & Gasfield Company, Chengdu, Sichuan 610000, China Exploration and Development Institute of SINOPEC Exploration Branch Company, Sichuan 610041, China Southern Petroleum Exploration and Development Company Ltd., Haikou, Hainan 570216, China

寒武系洗象池组是四川盆地下古生界天然气勘探重要接替层系，规模储层控制了低勘探程度区的勘探发现。采用岩心、测井和地震资料分析，结合区域构造演化，通过对该区洗象池组滩相白云岩原岩结构恢复，开展了储层特征、控制因素及发育模式等研究。①滩相白云岩储层岩石类型包括砂屑白云岩、含砾屑砂屑白云岩、砂砾屑白云岩、鲕粒白云岩、残余颗粒白云岩以及晶粒白云岩等，主要发育在滩—滩多期叠置、坪—滩—坪、潟湖—滩—潟湖和坪—滩—潟湖等多种沉积微相组合序列。储集空间类型以晶间(溶蚀)孔、粒间(溶蚀)孔和溶洞为主，少量(溶蚀)裂缝发育。储层段孔隙度在3%~6%之间，最高可达10%以上。②在同沉积古隆起影响下，洗象池组滩相白云岩受同生—准同生期高频次暴露形成了大量溶蚀孔洞，后期叠加了加里东期多幕次构造作用的影响，形成了规模发育的滩相白云岩储层。其中，洗象池组沉积末期的郁南运动影响范围大，全盆地广泛发生暴露，对洗象池组中—上部储层有进一步改造作用；都匀运动和广西运动可能对川中古隆起及周缘储层有改造作用。③全盆地洗象池组以Ⅱ类储层和Ⅲ类储层为主，其中，古隆起周缘斜坡带(合川—营山)规模储层分布面积过万平方千米，有望成为目前最有利勘探区带。

The Cambrian Xixiangchi Formation is an important succeeding stratum for gas exploration[JP] in the Lower Paleozoic of the Sichuan Basin, for which, the exploration degree is low, and the main controlling factors of large-scale[JP] reservoirs have not been well understood. Based on core, logging, seismic data and combined with regional tectonic evolution analysis, the original sedimentary structure of the shoal dolograinstone reservoir in the Cambrian[JP] Xixiangchi Formation were restored in this paper, and the characteristics, controlling factors and development patterns were further discussed. Results show that: (1) The rock types of shoal dolograinstone karst reservoirs mainly include dolograinstone, dolopackstone, granulated dolostone, residual granular dolomite and grain dolomite. It appeared to be developed in a variety of sedimentary micro-facies assemblages, such as shoal-shoal superimposition, flat-shoal-flat, lagoon-beach-lagoon and flat-beach-lagoon. The main reservoir space are intergranular (dissolution) holes, intergranular (dissolution) pores and vugs, and a small number[JP] of (dissolution)fractures were also developed. The reservoir porosity ranges from 3% to 6% with a highest value greater than 10%. (2) The dolograinstone shoal facies dolostone of the Xixiangchi Formation was controlled by the sea level changes and synsedimentary paleouplift. A large number of dissolution pores were formed after multiple exposure in the contemporaneous and quasi contemporaneous periods. Among them, the Yunan Movement at the end of the Xixiangchi period has a wide range of distribution and extensive exposure in the whole basin, which may further transform the middle and upper reservoirs of the Xixiangchi Formation. The Duyun and Guangxi movements might transform the central Sichuan paleouplift and its surrounding reservoirs. (3) The favorable reservoir distribution areas of Xixiangchi Formation in the Sichuan Basin were predicted to develop mainly type Ⅱ and Ⅲ reservoirs. Among them, the scale reservoir distribution area of the slope belt around the paleo-uplift is more than 10 000 km2[JP], which is expected to be the most favorable exploration area at present.

国家科技重大专项"下古生界-前寒武系碳酸盐岩油气成藏规律、关键技术及目标评价" 2016ZX05004-001

https://doi.org/10.11781/sysydz202203433