摘要：

页岩储层因低孔低渗特征，常规开发手段难以实现有效动用。注CO₂技术既可提高油气采收率，又能兼顾地质封存，具有双重效益。然而，CO₂注入后引发的矿物溶蚀与沉淀作用会显著改变储层孔隙结构及流体渗流能力，其微观机理尚缺乏系统认识。本文基于真实页岩数字岩心，采用格子Boltzmann方法构建孔隙尺度反应输运模型，系统模拟CO₂—矿物反应过程中溶蚀与沉淀的时空演化规律，并分析注入速度与反应强度对矿物反应机制及渗透率演化的调控作用。研究结果表明，CO₂注入后页岩内部呈现溶蚀、沉淀与再溶蚀交替循环的演化特征，渗透率表现出阶段性波动，优势渗流通道的形成是流体实现贯通的关键控制因素。溶蚀与沉淀共同主导孔隙结构演化，二者之间存在明显的正反馈机制，溶蚀促进流体流动进而增强反应物供给，而沉淀则局部堵塞喉道并改变流动方向。注入速度与反应强度对反应前缘推进距离、沉淀堵塞程度及优势通道发育具有显著调控作用，高注入速度有利于扩大反应波及范围和促进通道贯通，低注入速度则使反应前缘趋于均匀推进；高反应强度增强入口端矿物溶蚀并延长沉淀阻塞周期，低反应强度下溶蚀沉淀循环更为频繁但幅度较小。本研究揭示了CO₂注入后矿物反应驱动孔隙结构动态演化的微观机制，明确了注入参数对渗流能力变化的影响规律，为页岩储层CO₂注入过程中注采参数优化及储层伤害防控提供了理论依据。

关键词: 格子Boltzmann方法, CO₂—矿物反应, 溶蚀—沉淀, 孔隙结构演化

Abstract:

Shale reservoirs are characterized by low porosity and low permeability, rendering conventional development methods ineffective. CO₂ injection technology can simultaneously enhance hydrocarbon recovery and achieve geological sequestration. However, mineral dissolution and precipitation induced by CO₂ injection significantly alter pore structure and seepage capacity, yet the underlying microscopic mechanisms remain insufficiently understood. Based on real shale digital rock, this study constructs a pore-scale reactive transport model using the lattice Boltzmann method to systematically simulate the spatiotemporal evolution of dissolution and precipitation during CO₂-mineral reactions, and analyzes the regulatory effects of injection rate and reaction intensity on mineral reaction mechanisms and permeability evolution. The results indicate that after CO₂ injection, the shale exhibits a cyclic evolution characterized by alternating dissolution, precipitation, and re-dissolution, with permeability showing periodic fluctuations. The formation of preferential flow pathways is the key factor enabling fluid breakthrough. Dissolution and precipitation jointly control pore structure evolution, with a clear positive feedback mechanism between them: dissolution enhances fluid flow and reactant supply, while precipitation locally blocks throats and redirects flow paths. Injection rate and reaction intensity significantly regulate the advancement distance of the reaction front, the degree of precipitation clogging, and the development of preferential channels. Higher injection rates expand the reaction sweep range and facilitate channel breakthrough, whereas lower rates lead to more uniform front advancement. Higher reaction intensities enhance mineral dissolution near the inlet and prolong precipitation blocking periods, while lower intensities result in more frequent but smaller-amplitude dissolution-precipitation cycles. This study reveals the microscopic mechanisms of pore structure dynamic evolution driven by mineral reactions following CO₂ injection, clarifies the influence patterns of injection parameters on seepage capacity variation, and provides a theoretical basis for optimizing injection-production parameters and preventing formation damage during CO₂ injection in shale reservoirs.

Key words: lattice Boltzmann method, CO₂-mineral reaction, dissolution-precipitation, pore structure evolution

中图分类号: 

• TE341

• P618.13