济阳坳陷太古宇已逐渐成为油气勘探重点目标之一,但储层形成机制认识不清,严重制约了勘探发现。本文通过野外地质考察、岩心观察和薄片鉴定,结合阴极发光、XRD、扫描电镜、流体包裹体等分析测试,对济阳坳陷太古宇基岩的成岩作用及其对储层发育的影响进行了系统研究。成岩作用特征通过岩心、铸体薄片、元素分析结果和流体包裹均一温度识别,其对储层发育的影响作用通过铸体薄片面孔率和物性测井数据表征。结果表明:研究区基岩岩性主要为岩浆岩和变质岩两大类,岩浆岩先后经历了冷凝固结、岩浆期后热液、风化剥蚀淋滤和埋藏成岩4个成岩阶段,其中岩浆岩先后经历了冷凝固结作用、压实作用、溶蚀作用、充填胶结作用和蚀变交代作用,最后经变质变形作用形成变质岩。冷凝固结作用可以形成少量原生基质孔隙,溶蚀作用可形成溶蚀孔和溶蚀缝,孔隙度贡献可达80%,对改善储层质量起关键性作用;压实作用和蚀变交代作用破坏孔隙,方解石和黏土矿物等次生矿物充填胶结裂缝,充填度为30%~70%,对储集空间有破坏作用。综合分析得出,片麻岩储层物性特征优于花岗岩,有利于储层主要发育在风化壳和内幕断裂带。风化壳分布于基岩潜山顶部,纵向具有分带性,主要受控于风化作用,多发育Ⅰ和Ⅱ类储层。内幕断裂带分布在潜山腹部,沿断裂发育,主要发育Ⅱ和Ⅲ类储层。该研究成果可为基岩储层成因研究提供参考。

The Archean basement of the Jiyang Depression has emerged as a key target for oil and gas exploration; however, an unclear understanding of the reservoir formation mechanisms has severely limited exploration and discovery efforts. This paper systematically studies the diagenesis of Archean basement rock in the Jiyang Depression and its influence on reservoir development through field geological investigation, core observation, thin section identification, cathodoluminescence, X-ray diffraction (XRD), scanning electron microscopy, and fluid inclusion analysis. Diagenetic characteristics are identified based on core analysis, flake and elemental analysis results, and fluid inclusion homogenization temperatures. The impacts of these characteristics on reservoir development are characterized through flake face rates and physical property logging data. The results indicate that the lithology of the basement rock in the study area is primarily divided into two categories: magmatic and metamorphic rocks. Magmatic rock has undergone four successive diagenetic stages: condensation consolidation, post-magmatic hydrothermal alterations, weathering denudation leaching, and buried rock formation. During these stages, magmatic rock has experienced processes such as condensation consolidation, compaction, dissolution, filling and cementation, as well as alteration and metasomatism. Eventually, metamorphic rock is formed through metamorphic deformation. Condensation consolidation can create a small number of primary matrix pores, while corrosion processes generate corrosion pores and fractures, contributing to up to 80% of the porosity, which is crucial for enhancing reservoir quality. Conversely, compaction, alteration, and metasomatism tend to destroy these pores, as calcite, clay minerals, and other secondary minerals fill and cement fractures, with a filling degree ranging from 30% to 70%, adversely affecting reservoir space. A comprehensive analysis reveals that the physical properties of gneiss reservoirs are superior to those of granite. Favorable reservoirs are mainly located in the weathering crust and the inner fracture zone. The weathering crust, which is situated at the top of the buried hill of the basement rock, displays longitudinal zoning and is primarily influenced by weathering, leading to the development of I and II reservoirs. The inner fault zone, located in the middle section of the buried hill and aligned along fault lines, predominantly develops II and III reservoirs. The findings of this study provide valuable insights into the genetic research of basement rock reservoirs.