页岩气储层不同润湿性孔隙的连通性研究

Pore connectivity is an important, yet a poorly studied, aspect of pore structure characterization in shale gas reservoirs. Based on the studies of petrology, geochemistry and geometric characteristics of pore structure in shale reservoirs, this project will focus on the Wufeng-Longmaxi black shales from the Fuling gas field. High resolution imaging technologies are adopted to visually investigate and reconstruct the spatial distribution of micro- and nano- scale pores in shale. Using fluid (nitrogen, mercury and helium) injection, nuclear magnetic resonance and spontaneous imbibition approaches, the multi-scale connected pores in shale reservoirs will be characterized and key parameters for pore connectivity will be extracted. Based on imbibition and saturation diffusion tests involving three types of nano-sized tracers followed by laser ablation-inductively coupled plasma-mass spectrometry, the distributions of nano-sized tracers with different polarities in the connected pores will be characterized, as well as the connectivity of pores with different wettability. Using the above integrated approaches, connectivity of pores with different wettability of gas shale reservoirs will be comprehensively characterized, and effective characterization methods for pore connectivity will be proposed. By comparative investigations of the pore connectivity among different lithofacies, the influence of wettability on pore connectivity and main controlling factors of pore connectivity will be investigated. The outcomes of this project can provide theoretical bases for the establishment of shale pore structure model and reveal of the percolation mechanism for pore fluids in shale pore spaces.

页岩气储层的孔隙连通性是孔隙结构研究的重要内容，是目前页岩气储层孔隙结构研究的薄弱环节。本项目以涪陵气田五峰－龙马溪组黑色页岩为研究对象，在岩石学、地球化学和孔隙结构几何学特征研究的基础上，利用高分辨率成像技术重构页岩微纳米孔隙的空间分布，实现孔隙连通性可视化研究；采用流体（氮气、汞和氦气）注入法、核磁共振和自发渗吸实验表征页岩不同尺度的连通孔隙特征，提取表征孔隙连通性参数；基于三类纳米示踪剂自吸与饱和扩散实验以及LA-ICP-MS技术，研究不同极性纳米示踪剂在页岩连通孔隙的分布特征并刻画页岩不同润湿性孔隙的连通性；通过上述互补性实验综合表征页岩气储层不同润湿性孔隙的连通性，提出适合页岩储层孔隙连通性的表征方法；对比研究不同岩相页岩孔隙连通性的差异，研究润湿性对孔隙连通性的影响，分析页岩气储层孔隙连通性的控制因素。该研究成果可为构建页岩孔隙结构模型和揭示页岩孔隙流体渗流机理提供理论依据。

页岩气储层的孔隙连通性是孔隙结构研究的重要内容，是目前页岩气储层孔隙结构研究的薄弱环节。本项目以涪陵气田五峰－龙马溪组黑色页岩为研究对象，在查明页岩岩石学、地化和岩相特征基础上，重点针对4类主要岩相开展了对比研究，利用高分辨率成像技术重构页岩微纳米孔隙的空间分布，实现了孔隙连通性可视化研究；利用流体注入法和自发渗吸实验、纳米示踪剂、LA-ICP-MS技术等技术手段，查明了不同极性纳米示踪剂在页岩连通孔隙的分布特征并刻画页岩不同润湿性孔隙的连通性；对比研究了不同岩相页岩孔隙连通性的差异，研究了润湿性对孔隙连通性的影响，进一步分析了页岩气储层孔隙连通性的控制因素。本项目的研究成果可为构建页岩孔隙结构模型和揭示页岩孔隙流体渗流机理提供理论依据，同时有利于页岩储层改造和提高页岩气开采效率，具有重要的理论和实践意义。