四川自贡地区五峰组—龙马溪组下段古地貌刻画及其油气意义

Paleogeomorphology restoration of Wufeng Formation-Lower Member of Longmaxi Formation in Zigong area of Sichuan Province and its oil and gas significance

王同 张克银 熊亮 史洪亮 董晓霞 魏力民 温真桃 欧阳嘉穗 李斌 王浩宇

WANG Tong ZHANG Keyin XIONG Liang SHI Hongliang DONG Xiaoxia WEI Limin WEN Zhentao OUYANG Jiasui LI Bin WANG Haoyu

1. 中国石化 西南油气分公司, 成都 610016; 2. 中国石化 西南油气分公司 博士后工作站, 成都 610016; 3. 西南石油大学 地球科学与技术学院, 成都 610500

1. SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610016, China; 2. Post-doctoral Research Station, SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610016, China; 3. School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China

四川盆地威远-自贡地区是页岩气重点产区之一。上奥陶统观音桥段的展布情况对于页岩气勘探具有重要指导意义。通过构造-沉积背景分析，结合自贡地区岩心、薄片、古生物、测井及沉积速率、碳氧同位素等资料，认为观音桥段为构造稳定期大幅海退背景下的介壳灰岩沉积。A205、A1井观音桥段的缺失反映古地貌高点暴露出海平面，未沉积观音桥段介壳灰岩，并剥蚀下伏五峰组页岩。据此，运用残余厚度法对五峰组观音桥段古地貌进行刻画，观音桥段及五峰组厚度在自贡地区由北西向南东均表现出厚-薄-厚的变化特征，认为自贡地区存在以A1井-A205井为核部的北东-南西向展布的自贡低隆。建立了五峰组-龙马溪组下段沉积期自贡低隆沉积演化模式，并揭示了对于龙马溪组高伽马段黑色页岩的沉积厚度的影响。五峰组-龙马溪组高伽马段厚度存在以自贡低隆区A1井-A205井为中心向四周增厚的趋势，自贡低隆区两侧的低洼区域为有利勘探区。

The Weiyuan-Zigong area is a main shale gas production area in the Sichuan Basin. The distribution of the Upper Ordovician Guanyinqiao Member provides significant guidance for shale gas exploration. Tectonic-sedimentary background analysis combined with core, thin section, paleontology, logging, deposition rate and carbon-oxygen isotope data were used to interpret the micro-paleogeomorphology of the Zigong area in the Hirnantian-Rhuddanian period. The Guanyinqiao Member comprises shell limestone deposited under the background of regression in the tectonic stabilization period. The Guanyinqiao Member was missing and the Wufeng Formation was thin in wells A205 and A1. The NE-SW-directed Zigong low uplift identified in wells A1 and A205. A sedimentary evolution model of the Zigong area during the Hirnantian-Rhuddanian period was established, and its influence on black shale thickness was clarified. The Wufeng Formation and the high gamma ray value section of Longmaxi Formation thickened around wells A1 and A205. Both sides of the Zigong low uplift are favorable for exploration.

中国石油化工股份有限公司非常规科技项目“川西南下古生界海相页岩气高产富集条件与有利区评价”（P15100）和四川省教育厅重点科研项目“深层页岩储集物性研究”（15ZA0047）联合资助。

https://doi.org/10.11781/sysydz201806764