川北地区上二叠统吴家坪组火山碎屑岩油气藏储层特征及主控因素

Characteristics and controlling factors of volcanic clastic rock reservoirs in Wujiaping Formation of Upper Permian in northern Sichuan Basin

夏文谦 朱祥 金民东 张雷 刘雁婷 章思遥

XIA Wenqian ZHU Xiang JIN Mindong ZHANG Lei LIU Yanting ZHANG Siyao

中国石化 勘探分公司, 成都 610041

SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

受峨眉地裂运动影响，川北地区二叠纪吴家坪期发育一套火山碎屑岩。该类岩性非均质性强，储层孔隙结构复杂。为进一步明确该地区吴家坪组火山碎屑岩油气藏储层发育特征和形成机理，从而落实其勘探潜力，以露头和实钻资料为基础，结合岩心薄片观察、地化分析、氩离子抛光扫描电镜、盖层微孔联合测定等多种手段，分析川北地区吴家坪组火山碎屑岩储层发育特征及成因机理。研究认为，该火山碎屑岩主要岩性为凝灰质泥岩、泥质凝灰岩及沉凝灰岩。储层储集空间主要为纳米级黏土矿物收缩孔和有机质孔，微米级有机酸溶蚀孔和微裂缝。储层物性具有中—高孔特低渗的特征，其中凝灰质泥岩物性最好。储层主控因素分析认为，近火山口斜坡—陆棚环境有利于火山碎屑岩储层发育，火山灰脱玻化作用及次生有机酸溶蚀是储层形成孔隙的主要原因。

Under the influence of the Emei Taphrogenesis, a set of volcanic clastic rocks were developed in the Wujiapingian age of Permian in the northern Sichuan Basin. The lithology is highly heterogeneous, and the pore structure of reservoir is complex. In order to further clarify the characteristics and formation mechanism of volcanic clastic rock reservoirs in the Wujiaping Formation and confirm the exploration potential, this paper analyzes the reservoir characteristics and formation mechanism of volcanic clastic rock reservoirs in the Wujiaping Formation in the northern Sichuan Basin based on outcrop and actual drilling data and combining with core section observation, geochemistry analysis, argon ion buffing scanning electron microscope, combined determination of cap micro pores and other methods. It is concluded that the volcanic clastic rocks can be divided into three rock types: tuffaceous mudstone, argillaceous tuff and sedimentary tuff. The reservoir space is dominated by nano-scale clay mineral shrinkage pore and organic matter pore and micron-scale organic acid dissolution pore and micro fracture. The reservoir physical property is characterized by medium to high porosity and ultra-low permeability, and the tuffaceous mudstone has the best physical property among the three rock types. The analysis of the controlling factors of the reservoir shows that the near-crater slope and shelf environment is favorable for the development of volcanic clastic rock reservoirs, and the devitrification of volcanic ash and secondary organic acid dissolution are the main causes for the formation of pores in the reservoir.

国家自然科学基金企业创新发展联合基金项目 U19B6003;中国石化科技部项目 P20059-1

https://doi.org/10.11781/sysydz202302307