The Thermal-Hydro-Mechanical Coupling For Heavy Oil Recovery And The Optimization Of Steam Injection

Steam stimulation is a complex system engineering with some great technical difficulties, which refers to reservoir geology, production technology, heat transfer, economic analysis, etc. therefore, to achieve the object of the steam stimulation scientifically and economically, we should, from actual conditions, study the main processes of steam stimulation, which includes temperature and pressure transmission of steam in the well bore, heat and mass transfer of multiphase flow in reservoir, etc. so as to determine scientific and rational production mode and working system. In this paper, the flow of steam in the well bore and reservoir are seemed as a whole system. By considering the coordinating relationship between wellhead injection parameters and steam absorption ability of reservoir, vapor-liquid dynamic mathematical models of shaft in the process of steam injection is established. By comprehensively analyzing the coupling relationship among temperature field, fluid field and solid field and mechanical mechanism of three fields, a thermo-hydro-mechanical coupling model reflecting real reservoir conditions of changing temperature and deformation is established. On this basis, according to non-uniformity absorption of horizontal well section in the process of steam injection, an optimization model of horizontal-well steam injection parameters is established. This paper has main sections as follows:1. Based on mass conservation, momentum conservation and energy conservation, a comprehensive mathematical model predicting pressure and temperature distribution in the well bore is established. Using iteration method, the pressure and dryness in the well bore is calculated and its sensitive analysis is conducted.2. Based on continuum, hydro-mechanical coupling, coupled thermal elasticity mechanics and thermodynamics theory, a coupled thermo-hydro-mechanical mathematical model is established. With corresponding finite element formulas and decoupling method given out. Using finite element program FEPG, the steam injection process in the reservoir is simulated, some significant parameters, such as horizontal displacement, vertical displacement, horizontal stress and vertical stress in reservoir, are compared and analyzed. Corresponding conclusions show the importance role of thermo-hydro-mechanical coupling during heavy oil recovery.3. Base on the above study and with a goal of uniform steam injection in the horizontal section, thermodynamic model of steam in the steam injection string and throttling model of flow regulator are established. Using finite-element numerical modeling method, structure parameters of horizontal steam injection string are optimized with some quantitative results given out.