玄武岩孔隙结构特征及其对储层渗透性的影响研究

Multiple pore network of basalts is composed of diverse pores and fractures with different scales, which is significant to reserving of hydrocarbons, ground water and heat resources, and also to permanent carbon dioxide storage. As the key factor which determines the reservoir and sealing capacities, the permeability of basalts is close related to their pore structures. Comparatively study the outcrop samples of Jingpohu Holocene basalts and borehole core samples from Liaohe Depression, which were formed in similar tectonic background due to the Tanlu fault zone. Serial sectioning of resin-impregnated plugs and scanning electron microscope are used to decomposition and characterization of pore network. On the basis of description and summarization of pore types, shapes, occurrences and identifying marks, the pore network of basalt is decomposed into four units such as macro pores, fractures, intra-phenocrystal porosities and matrix porosities. Characteristics of these four porosity units and their connections and proportions are used to the description and modeling of pore networks. High-pressure mercury injection, low-temperature nitrogen adsorption, porosity and permeability tests are used to obtain quantitative parameters of pore structure and reservoir permeability, which are further applied to principal component analysis and grey relational analysis, thus enabling the classification and evaluation of pore structures, summarization of their characteristic parameter ranges and modeling of typical pore networks.Moreover, impacts of diagenesis on pore structures are studied by energy spectrum, cathodoluminescence (CL), whole rock mineral analysis and experiments of rock mechanics. Finally, synthetic studies enable the discoveries of heterogeneities of pore structures and permeabilities as well as their controlling factors, and indicating the distribution of high permeable reservoir bodies and low permeable barriers.

玄武岩发育由多种类型、不同尺度的孔隙和裂缝组成的复杂多重孔隙网络，对于油气、地下水和地热资源的存储以及二氧化碳注入封存等具重要意义。作为决定储集性能和封隔能力的关键指标，玄武岩的渗透性与孔隙结构密切相关。拟通过露头与钻井对比，借助岩样铸体系列切片和扫描电镜分析，对玄武岩孔隙网络进行分解刻画，总结孔隙类型、形貌产状及识别标志，分析宏观孔隙、宏观裂缝、斑晶内孔隙和基质孔隙等4类孔隙单元发育特征、连通关系及占总孔隙的比例。借助高压压汞、低温液氮吸附和孔渗测试，获取表征储层孔隙结构和渗透性的定量参数，结合主成分分析和灰色关联分析，开展孔隙结构分类评价，总结孔隙结构类型及其特征参数范围，建立孔隙结构模式。综合能谱、阴极发光、全岩矿物分析和岩石力学实验，探究充填、蚀变和溶解等成岩作用对玄武岩孔隙结构的影响，阐述各类孔隙结构的储层渗透性差异及其控制因素，指出玄武岩高渗储集体和低渗隔挡层的分布规律。

玄武岩发育由多种类型、不同尺度的孔隙和裂缝组成的复杂多重孔隙网络，对于油气、地下水和地热资源的存储以及二氧化碳注入封存等具重要意义。本项目主要通过露头与钻井对比，开展玄武岩多重孔隙网络分解刻画与孔隙结构量化表征，总结了玄武岩孔隙网络连通方式及特征，建立了玄武岩孔隙连通方式与储层渗透性的对应关系，明确玄武岩孔隙结构和储层渗透性差异的影响因素，并指出玄武岩高渗储集体和低渗隔挡层的分布规律。结果表明：玄武岩孔隙网络主要由宏观孔隙、宏观裂缝、斑晶内孔隙和基质孔隙等4类孔隙单元组成，共发育8种储集空间类型。孔隙连通方式主要包括气孔—气孔、气孔—裂缝—气孔、气孔—基质溶孔—气孔3种类型。玄武岩总体上孔隙度介于0.9%~30.2%、渗透率介于0.01~36.6md。气孔玄武岩孔隙度最高（平均13.4%），角砾化玄武岩次之（平均11.7%），致密玄武岩孔渗性较差（平均8.3%）。对储层贡献较大的有效孔隙主要为气孔充填残余-溶蚀孔、节理缝和构造缝，有效孔隙主要受气孔-裂缝分带性、蚀变充填作用、界面溶蚀改造作用、近断裂构造作用等因素控制。与基质矿物蚀变形成的黏土矿物相关的微裂缝以及基质溶蚀微孔对提高玄武岩的孔隙连通性以及储层渗透性能起到极为重要的作用。