The Analysis Of Water Injection And Casing Damage Based On THM Coupling

In oil exploration and drilling process,seepage, stress and temperature are the important factor influencing oilfields mining, whose interaction and the relationship between the thermal-hydrological-mechanical(THM) coupling constitute the basic relations. In recent years, the number of casing damage well is rising sharply, like daqing oilfield, jilin oilfield and shengli oilfield, etc have happened to the casing damage. According to statistics, 90% above of casing damage problem has a direct or indirect relation with modern geostress. Based on the research of the casing well, we know that the occurrence of casing damage has the a relation with rock, fluid and temperature interaction. So reserching the fluid pressure and stress and temperature of the water injection formation is quite important to prevent casing damage. So the water injection formation will be quite important in the process of THM coupling.In this paper, from 2-dimensional elasticity and plasticity and 3d elastic and elastoplastic, we research the formation in water comprehensivly. We see the permeability and porosity, density and so on as the physical quantities which change with the time and pressure. On the basis of the equation of continuity, energy equation and motion equation , we establish the mathematical model of THM coupling. Namely: the seepage control equations under the distortion field and temperature field; the deformation equation under the seepage field and temperature field; the temperature control equations under the seepage and distortion field. On this basis, the paper derives the form weak solution of THM coupling problem. We simulate and simulate the deformation of water injection formation for 2 dimension and 3 dimension. The results of simulation indicate, the casing deformation and damage have a close relationship with the water injection formation of THM coupling effect; In the process of water flooding, because the change of surface stress is the biggest near the cap rock and reservoir, therefore in the probability of casing damage happens here is the largest, so the probability of casing damage is the most. For casing itself, the perforating segment is the weak link and the concentration of geostress. Through the analysis of casing deformation, this paper proposes design flaws and preventing measures for casing damage.