Safety Evaluation Of Geological Environment In The Process Of Waste Water Reinjection

During the course of waste water reinjection, the pore pressure and temperature arealways changing, this would cause the porous media to deformation, and the porous mediadeformation would also influence the pore pressure and temperature. And chemicals in wastewater will affect the physical parameters of stratum, leading to the changes of reservoir stressand temperature. In return, the changes of reservoir stress and temperature will affect thetransport of pollutants. Formation fluid flowing, temperature, strata deformation andpollutants migration are interacting and inter-influencing, this is so-called Thermal-Hydrological-Mechanical-Chemical coupling. It has extremely important application value inconcerning the THMC coupling functions researches in many domains such as the petroleumengineering, the underground nuclear waste storage security and so on. As a result of thedifferences of the research object, the forms of the THMC coupling models exist differences,it is extremely difficult to establish the coupling model conforming to the actual problem.Therefore, the saturated porous media is taken as the research object in this paper, with mixedanalytic method, and the THMC coupling model is established based on the smalldeformation situation, and calculated to be confirmed through Mathematics analytic solutionand numerical simulation.On the bases of the theory of continuum mechanics, aining at the queation of multi-fieldcoupling, especially the THMC coupling, this paper developed the following research work:(1) Using the equivalent continuum model, according to the linear momentum balanceequation, mass conservation equation and energy conservation equation and thecorresponding physical equation (state equation and constitutive equation), THMC couplingmathematical model is derived. The chemical field and other fields coupling effect is the keyconsideration in the model. (2) By finite Fourier transformation to solve the one-dimensional case of THMCcoupling equations, and comparing with existing Terzaghi theory solution and verify therationality and feasibility of the model.(3) The THMC coupling problem in the process of waste water reinjection arenumerically simulated using Comsol multiphysis, some significant parameters, such asdisplacement, pore pressure, temperature and concentration are compared and analyzed.Corresponding conclusions show the importance role of the THMC coupling, furthermore, themulti-field coupling regulations of porous media are discussed.