川西龙门山前带雷口坡组四段古表生期大气水溶蚀作用对储集层的影响

Palaeokarst characteristics and effects on reservoirs in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin

李勇 邓美洲 李国蓉 高恒逸 王琼仙 何赛

LI Yong DENG Meizhou LI Guorong GAO Hengyi WANG Qiongxian HE Sai

中国石化 西南油气分公司 勘探开发研究院, 成都 610041 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 Research Institute, Southwest Oil and Gas Company, SINOPEC, Chengdu, Sichuan 610041, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China

川西龙门山前带雷口坡组四段主要岩石类型为潮坪相白云岩。该套白云岩储层的形成主要受沉积相带、白云化作用和溶蚀作用控制。利用岩心观察、薄片分析、激光碳氧同位素、探针微量元素、阴极发光及包裹体测温等实验手段，对溶蚀作用进行研究。研究表明该储层经历了3期溶蚀作用，即准同生期、古表生期和埋藏期，分别形成粒内溶孔及铸膜孔、膏溶孔洞以及沿裂缝或缝合线分布的溶蚀孔洞。深入研究古表生期岩溶作用和膏溶作用发现，印支Ⅰ幕大气水作用的识别标志有不规则网络状风化裂缝、岩溶及膏溶膏变角砾岩、保持石膏板状形态或直角边形态的去膏化方解石、广泛发育的膏模孔及膏溶孔洞，同时具有低的碳氧稳定同位素值、宽值域的锶同位素值、低含量的Sr-Mn-Fe-K-Na微量元素、低温单相水溶包裹体等地球化学特征，印支Ⅰ幕大气水作用下含膏白云岩内膏溶作用是储集层形成的关键作用。

Dolostones of tidal flat facies are the major reservoir rock type of the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin. The reservoir controls are dominated by phase belt, dolomitization and denudation. Core observation, cast thin section identification, laser carbon and oxygen isotopes, cathode luminescence, electron probe and inclusion thermometry were used to study the denudation effect. This reservoir went through three periods of denudation, including penecontemporaneous period, epidiagenetic period and buried period, which separately formed intragranular and moldic pores, gypsum caves, and fault-line cavities. The studies of karstification and gypsum dissolution in the paleo-epigenetic period showed that, the distinguishing signs of meteoric water impacts in episode I of the Indosinian Movement include the irregular network of weathering cracks, karst and gypsum breccia, de-anointed calcite maintaining gypsum board shape or right-angle edge shape, widely developed paste mold holes and paste-dissolved holes. These products are featured by low carbon and oxygen stable isotope values, a wide range of strontium isotope values, low content of Sr-Mn-Fe-K-Na trace elements, low-temperature single-phase water-soluble inclusions. The dissolution of gypsum in episode I of the Indosinian Movement is the key for reservoir generation.

国家科技重大专项“川西山前带潮坪相白云岩储层地震预测应用研究” 2017ZX05005-004-010;中国石化重大科技攻关项目“龙门山前雷口坡组气藏综合评价及开发技术政策研究” P16111

https://doi.org/10.11781/sysydz202101056