川西南二叠系茅口组一段滑石特征及其形成机理——以A1井茅一段样品为例

Characteristics and formation mechanism of talc in Permian Maokou Formation, southwestern Sichuan Basin: a case study of first member of Maokou Formation in well A1

任海侠 林小兵 刘叶 敬永红 钟玉梅 康保平 韩智英

REN Haixia LIN Xiaobing LIU Ye JING Yonghong ZHONG Yumei KANG Baoping HAN Zhiying

中国石化 西南油气分公司 勘探开发研究院, 成都 610041 中国石化 西南油气分公司 地质中心实验室, 成都 610081 成都理工大学 油气藏地质及开发工程国家重点实验室, 成都 610059

Exploration and Production Institute of SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610041, China Central Laboratory of Geology, SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610081, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China

四川盆地二叠系茅口组一段发育形态各异的滑石，作为一种热液蚀变矿物，其形成机理及对茅一段储层的影响尚待深入探索。以四川盆地西南地区茅一段的滑石为研究对象，通过岩心观察、薄片鉴定，结合扫描电镜、包裹体均一温度等测试数据，在精细描述滑石颜色、结构、赋存状态的基础上，探讨了滑石形成机理。茅一段滑石主要赋存于泥晶生屑灰岩、生屑泥晶灰岩和灰质云岩中，以交代生屑颗粒或呈星点状赋存于泥晶灰岩中；滑石是硅质热液流体与富镁碳酸盐岩在一定条件下发生交代作用而形成的，属于热液交代型；储层中滑石含量与储层物性呈正相关关系，滑石在形成过程中产出大量CO2酸性气体，对茅一段储层孔隙具有一定的溶蚀改造及保存作用，有利于提高储集性能；滑石具有指示含硅流体运移路径及分布范围的作用，热液高能区为下一步勘探有利区。

Different forms of talc have been developed in the first member of Permian Maokou Formation (P2m1) in the Sichuan Basin. As a hydrothermal alteration mineral, its formation mechanism and its influence on the P2m1 reservoir need to be further explored. The talc of P2m1 in the southwestern Sichuan Basin was studied by means of core observation, thin section identification, scanning electron microscope, and the homogenization temperature of fluid inclusions. Based on the detailed description of the color, structure and occurrence state of talc, the formation mechanism of talc was discussed. The talc of P2m1 mainly occurs in micrite bioclastic limestone, bioclastic micrite limestone and limestone dolomite, or in micrite limestone as metasomatic bioclastic particles or star points. The genetic mechanism of talc is metasomatism between siliceous hydrothermal fluid and magnesium-rich carbonate rocks under certain conditions, which belongs to hydrothermal metasomatism. There is a positive correlation between the content of talc and the physical properties of reservoir. Large amount of acid gas (CO2) may be generated during the formation process of talc, which was favorable for the dissolution and pore preservation of P2m1 and finally to improve the reservoir capacity. The existence of talc may be indicative for the migration path and distribution of silicon-bearing fluid, and the hydrothermal high energy area is favorable target for further exploration.

国家科技重大专项 2016ZX05007-004-02;国家自然科学基金项目 41772134

https://doi.org/10.11781/sysydz2021061038