Study On Engineering Optimization Of Heavy Oil Reservoir In SAGD Mining Of Double Horizontal Well

Steam assisted gravity drainage (SAGD) technology is an innovation exploitation of heavy oil reservoir, it will achieve very satisfactory results in the mining index and economic benefits because of using this technology in suitable heavy oil reservoir. Research SAGD technology for the exploitation of heavy oil reservoirs is very important.In this paper, dual horizontal wells steam assisted gravity drainage technology was studied through theoretical study and numerical simulation methods. In the theoretical study, analyzed the basic principle of the steam-assisted gravity drainage, described the flooding mechanism of steam assisted gravity drainage and exploration characteristics and well pattern, adaptability of the steam-assisted gravity drainage was studied from two aspects of geological and fluid, and summed up the screening criteria of SAGD exploration. According to the SAGD drainage theory, the mathematical model of dual horizontal wells was built, obtained analytical solutions, the lateral extension curves of vapor-liquid interface of steam chamber was calculated by the theoretical formula, and analyzed the relevant factors on SAGD production through the production forecast formulas.In this paper, taking an example of dual horizontal wells SAGD, establish a numerical model, first of all, research parameters optimization of steam circulating preheating phase of the dual horizontal wells steam assisted gravity drainage and obtained reasonable preheating parameters through numerical simulation, then researched the steam chamber expansion of dual horizontal wells steam assisted gravity drainage, at last, optimized parameters of production and injection wells in SAGD production stage.In the steam circulating preheating phase, steam injection rate, steam quality, steam injection pressure, the timing of applying pressure, pressure difference between the wells and other parameters were researched in this paper. Numerical simulations show that cyclic steam injection rate select80m3/d, steam quality should not be less than70%, steam injection pressure is not higher than the initial reservoir pressure of0.5MPa,60days after the preheating,100kPa is applied between wells. When the steam chamber expanded lateral, it is affected by the steam chamber temperature, reservoir permeability and the reservoir porosity respectively, the higher the temperature of the steam chamber, steam chamber expanded lateral sooner; reservoir permeability is greater the lateral expansion of the steam chamber is sooner; smaller reservoir porosity, steam chamber expanded lateral sooner, while the effects of different parameters on the production forecast were researched. During SAGD production stage, the changes in temperature and pressure along the wellbore were studied in the paper, and optimized steam injection rate and the steam quality of injection well, the fluid recovery rate and sub-cool control of production well. For steam injection well, SAGD production time increases, temperature and pressure along the wellbore is gradually reduced and becomes stable; for production well, SAGD production time increases, the temperature along the wellbore gradually increasing and pressure along the wellbore is gradually reduced. When the steam injection rate increases, the daily oil production increased, if steam injection rate is too high, the oil steam ratio will be reduced, and steam may break through in production well, so select the steam injection rate of250m3/d-300m3/d; the higher steam quality, the higher the oil steam rate, when steam quality is too lower the oil gas rate is relatively low, so the steam quality should not be less than70%; the higher production-injection ratio, oil production higher, but when the ratio is too high, oil production is almost no change, so the best production-injection ratio is1.3-1.4; when sub-cool is too large, it is not conducive to the development of the steam chamber, when sub-cool is too small, it is too easy to cause steam breakthrough, so it is proposed to sub-cool control in the range of5℃-10℃.