A Top Injection Bottom Production Cyclic Steam Stimulation Method For Heavy Oil Reservoirs

Exploitation of heavy oil usually selects the method of thermal recovery, including steam flooding, steam stimulation, in-situ combustion, steam assisted gravity drainage oil(SAGD)and so on. Compared to steam stimulation, SAGD development can get high final recovery efficiency, but the application is restricted in the shallow-thin reservoir. In addition, the common wells with steam stimulation cycles increased downhole technical condition worse, so that the high-order wells stimulation effect of variation, thereby increasing the technical difficulty of improving the throughput effect of the old wells. In view of these questions, proposed that the top injection bottom production cyclic steam technology, which uses dual packer and dual tubing production, after crestal steam injection, closes the steam injection string, directly opens the bottom to product without soaking. Therefore, the research of this technology can enhance the recovery efficiency of heavy oil, there is a very important practical and economic significance.Based on the mechanism of heavy oil thermal production, through the research of crude oil, formation water, water of dehydration as well as the change rule of mixture density and viscosity which change along with variation of temperature, to determine the effect of the heavy oil thermal production development. Establishment the single well numerical simulation of heavy oil reservoir, combined with the production of dynamic data for history matching, to modify and adjust the model, so the simulation dynamic is consistent with the actual. Using history matching verification model contrast the recovery effect of the Top injection bottom production cyclic steam technology with the traditional technology. Due to the influence of heavy oil viscosity, reservoir thickness, density difference between oil and water on the top injection bottom production cyclic steam technology exploitation effect, so before the implementation, for Different reservoirs or a single well, it is necessary to optimize design of injection production parameters, in order to obtain the optimal parameter combination. Also the thesis research on top injection bottom production cyclic steam technology adaptability evaluation for heavy oil reservoirs to determine the adaptability.Through experiments and numerical simulation on prediction research, analysis, have drawn the following some meaningful conclusions:1Analysis of the enhanced recovery mechanism of the tap casting and bottom withdrawing dual pipe throughout technology, the main mechanism of the technology can be drawn as follows:thermal effects significant reduce the heavy oil viscosity, increase the mobility of heavy oil; using the density differences among steam, condensate and crude oil, so that gravity as the main driving force; Prolonging the residence time of hot injection steam in the reservoir to improve the system thermal efficiency.2Through the study of the temperature effects of heavy oil density and viscosity, Du229anhydrous oil sample density decreased with the temperature, viscosity under Different shear rate decreases with the increase of temperature; Du229water of dehydration density and pure water density decreases with the increase of temperature, the viscosity, decreases with the increase of temperature; when site water cuts is31%, the difference between Du229crude oil and water of dehydration increases with the increase of temperature slightly; when site water cute is0%, the difference between Du229crude oil and water of dehydration increases with the increase of temperature (70-95℃) slightly; and when the temperature is higher than95℃, the density difference declines with the increase of temperature rapidly, then the temperature reaches around170℃to180℃, density difference approaches to zero.3The establishment of a single well numerical simulator, combined with the production of dynamic data, to modify and adjust the model, so the simulation dynamic is consistent with the actual, through history matching and verification, the cumulative oil production to fit the absolute error of37.18m3, the relative error are-0.78%and0.79%, the coincidence rate high model is credible, which provides a reliable foundation for the next step predict, analysis and research.4The use of history matching verification model contrast the recovery effect of the top injection bottom production cyclic steam technology with the traditional technology, the cumulative oil production of the top injection bottom production cyclic steam technology increased compared to the traditional technology7535m3, recovery degree increased11.06%, composite water cut decreased2.5%, the increase effects significantly.5Using orthogonal design method to design optimal simulation scheme, analysis of variance indicated that liquid production per unit thickness on the recovery degree has the most significant effect, steam injection intensity, dryness fraction of steam, steam injection temperature on the degree of recovery effect is relatively distinct, the optimal injection-production parameters as well:steam injection strength400m3/d, dryness fraction of steam70%, steam temperature200℃, liquid withdrawal rate of50m3/d.6Through the research different crude oil viscosity, different reservoir thickness and vertical to horizontal permeability ratio in the adaptability of the top injection bottom production cyclic steam technology, and the results show that the same injection-production parameters, the top injection bottom production cyclic steam technology can effectively enhance the heavy oil reservoir development effect. At the same time oil viscosity, reservoir thickness and vertical to horizontal permeability ratio obvious effect reservoirs oil recovery of the top injection bottom production cyclic steam technology. To the different reservoirs, there is a limit of oil viscosity, reservoir thickness and vertical to horizontal permeability ratio for the top injection bottom production cyclic steam technology. Therefore, practice need to have the targeted evaluation research and injection-production parameters optimization.7The simulation forecast research shows that compared with the traditional cyclic steam injection, the top injection bottom production cyclic steam technology has obvious advantages, can effectively improve throughput heavy oil reservoir development effect, and the technology has good technology adaptability.