低渗透岩石渗透特性测试及渗流应力耦合实验研究

Low-permeability rock is the main media and the geological environment for store underground oil and gas and CO2 and nuclear waste disposal, the permeability properties testing of Low-permeability rock and hydro-mechanical coupling research is the challenge frontier problems in rock mechanics. In this study, the typical low-permeability rock is studied theoretically and experimentally, by means of development of test technical method, the threshold criterion of pressure pulse test for low-permeability rock of different levels will be proposed, the expression method of permeability for low-permeability rock is derived. Based on the permeability experiment and the microscopic tests of pore structure within rock, the criterion of seepage mode of low-permeability rock is proposed, the non-linear seepage model of reflecting the permeability evolution of low-permeability rock is established. According to hydro-mechanical coupling experiment and the microcosmic analysis to the rupture surface of rock specimen, the permeability evolution equation of reflecting the coupling of stress-strain-permeability is established, the HM coupling mechanism during the process of stress and strain will be developed. By means of simulation experiment, the muti-scale non-linear constitutive model of expression the HM coupling characteristics of low-permeability rock is established. The research achievements will promote the theory development of hydraulic mechanics for low permeability rock, and provide a new theoretical methods and technique for scientific prediction and analysis the seepage and stress field of low-permeability rock engineering.

低渗透岩石是地下石油和天然气储存、CO2储存、核废料处置的主要介质和地质环境，低渗透岩石的渗透特性测试以及渗流应力耦合特性研究是目前岩体力学研究中的热点和难点问题，也是亟待解决的前沿科学问题。研究工作以典型低渗透岩石为研究对象，通过实验测试方法研究，提出不同层级低渗透岩石压力脉冲法测试的阈值，推求不同层级低渗透岩石渗透率表达方法；通过气体脉冲压力渗流实验和岩石孔隙结构微观分析，提出低渗透岩石渗流形态判据，建立反映低渗透岩石渗透率演化规律的非线性模型；通过渗流应力耦合实验和岩石断口微观形态分析，建立反映应力-应变-渗流耦合过程的渗透率演化方程，揭示应力应变过程中渗流应力耦合机理；通过数值试验，建立反映低渗透岩石渗流应力耦合特性的多尺度非线性本构关系。研究成果将有助于推动低渗透岩石渗流力学理论的发展，为科学预测和分析低渗透岩石工程的渗流应力场及其工程应用提供理论方法。

研究工作结合重大工程实践，利用低渗透岩石渗透特性测试系统，开展了大量典型低渗透岩石（包括不同饱和度低渗透岩石）在不同条件下（不同围压、不同渗压、渗流应力耦合）的渗流力学特性试验。建立了围压、渗透压力与渗透率和孔隙度之间的变化规律，提出了低渗透岩石渗透率与孔隙度变化的关联方程、渗透率演化方程，通过岩石宏微观断口形态分析揭示其渗流破坏机理，在此基础上建立了低渗透岩石渗流应力耦合力学模型。通过试验论证了气体在低渗透岩石中渗流时，普遍存在滑脱效应现象，即渗流规律不符合达西定律，气测渗透率需要修正以反映实际岩石渗透特性。研究工作将有助于推动低渗透岩石渗流力学理论以及岩石力学基本理论的发展，进一步揭示非线性渗流的渗流模式和渗流规律，以及渗流应力耦合关系与机理。