CO2地质封存联合咸水开采协同作用机理及其优化控制研究

CO2 geological storage combining with deep saline water recovery (CO2-EWR) is one of the main ways to reduce CO2 emission with large-scale industrial application. The synergistic mechanism of injection-production process and the optimization of injection-production scheme are the key scientific problems of this technology to be urgently solved. The project focuses mainly on the influence of pore pressure gradient, chemical potential different and CO2 migration, caused by CO2 injection and brine exploitation, on pore mechanical property, permeability and mineral trapping. By the combined method of experiments, theoretical analysis and numerical simulation, the multi-factor synergistic mechanism of CO2 geological storage combining with deep saline water recovery is illuminated in the view of reservoir rock pore mechanics- mineralization reaction- permeation coupling theory. And the viscous-elastic-plastic pore mechanics model of reservoir rock in hydro-chemical-mechanical coupling process is established, as well as the porosity- permeability evolutionary model and pressure solution/precipitation model. With the application of 3d multiwell model, time-dependent effect of different coupled injection-production scheme on the permeability, mechanical deformation and mineralization reaction of reservoir rock is investigated to analyze and optimize the coupled injection-production scheme. The above research achievements would provide an important theoretical basis and technical support for the optimal utilization of pore space and mineral trapping in reservoirs and the safety and stability of CO2 geological storage combining with deep saline water recovery.

CO2地质封存联合深部咸水开采（即CO2-EWR）是开展规模化工业化应用的CO2主要减排途径之一。注采过程协同作用机理及注采方案优化是该技术亟待解决的关键科学问题。本项目以CO2注入与咸水开采过程中引起的孔隙压力梯度、化学势差以及CO2运移等对储层孔隙力学性质、渗透性能和矿物捕集的影响为研究主线，采用试验、理论分析和数值模拟结合的方法，从储层岩石孔隙力学-矿化反应-渗透耦合理论角度阐明CO2地质封存联合深部咸水开采过程多因素协同作用机理，并建立CO2渗流-化学-力学耦合作用下储层岩石的粘-弹-塑性孔隙力学模型及其孔隙度-渗透率演化模型和应力条件下溶解沉淀模型，利用三维多井模型模拟不同耦合注采方案对储层渗透性能、力学变形以及矿化反应的时效作用，由此分析优化耦合注采方案。研究成果可为实现储层孔隙空间和矿物捕集的优化利用并确保CO2封存与咸水开采过程的安全性与稳定性提供重要的理论依据和技术支撑。

CO2地质封存联合深部咸水开采（即CO2-EWR）是开展规模化工业化应用的CO2主要减排途径之一。在CO2地质封存联合咸水开采过程中实现储层的优化利用还存在一系列科学问题和难题亟待解决和突破。本项目以CO2注入与咸水开采过程中引起的孔隙压力梯度、化学势差以及CO2运移等对储层孔隙力学性质、渗透性能和矿物捕集的影响为研究主线，采用试验、理论分析和数值模拟结合的方法，从储层岩石孔隙力学-矿化反应-渗透耦合理论角度阐明CO2地质封存联合深部咸水开采过程多因素协同作用机理，并建立CO2渗流-化学-力学耦合作用下储层岩石的粘-弹-塑性孔隙力学模型及其孔隙度-渗透率演化模型和应力条件下溶解沉淀模型，利用Tough和Flac3D的迭代计算数值方法模拟CO2-EWR过程中咸水层渗透性能的时效规律。为了研究孔隙压力在CO2矿化捕集中的作用，开展了不同孔隙压力下砂岩试样的CO2-NaCl溶液渗透-蠕变试验。实验结果表明，孔隙压力越低，砂岩中固碳量越高，揭示了采用CO2-EWR方式在增强CO2矿物捕集方面的效果。建立了储层多孔岩石介质矿化捕集CO2的几何模型，定量描述了矿化捕集过程中的压力溶解机理。然后利用该模型进行数值计算，研究了影响深层盐水含水层CO2捕集效率的主要因素(矿物类型、温度、孔隙度、孔隙压力和粒径)，比较了不同温度、孔隙压力、颗粒直径和孔隙率下，单位立方米钠长石、碳酸钾长石和钙长石通过压力溶解作用吸收的CO2的累积量。结果表明，高地温、低孔隙水压力、大孔隙度、细颗粒矿物等封存条件对增加咸水层矿化封存CO2量有积极促进作用。这些因素可以用来作为判断矿化封存过程的潜在效率的评价指标，可为实现储层孔隙空间和矿物捕集的优化利用并确保CO2封存与咸水开采过程的安全性与稳定性提供重要的理论依据和技术支撑。