Abstract
Precise description of displacement efficiency (Ed) is extremely important for evaluating the performance, economic effectiveness and final recovery of thermal recovery techniques. Current researches mainly focused on one-dimensional core displacement experiment, and it is difficult to obtain precise Ed beyond the range of test points. In addition, there are two ways to improve the Ed for thermal flooding: Increasing injection pore volume (PV) or raising injection temperature (T), it’s hard to make decisions. In this study, the above two problems were solved by a statistical approach research. At the beginning, one dimensional core displacement experiment was carried out for hot water and steam, respectively. Then, dozens of curves and correlations about Ed varied with injection PV number and injection temperature was regressed, respectively. Based on this, the formula of Ed and PV, Ed and T for injection hot water and steam was established respectively, which makes up for the shortage of the finite test data points. Next, chart of the Ed between the PV and T was obtained. In addition, sensitivity analyses of injection rate and steam quality are discussed in this paper. Finally, the precise of the regression formula was verified by three steam flooding case of different heavy oil fields. The results indicated that, in order to get higher Ed, higher injection PV and temperature are beneficial. With the Ed chart, technicians can determine different schemes to improve oil displacement efficiency according to specific reservoir conditions. Besides, main production indexes such as oil recovery can be predicted quickly and precisely. Key words: Fossil energy, heavy oil, displacement efficiency, thermal recovery, steam flooding.  
Highlights
Oil reserves in the world can be classified into light oil, heavy oil and bitumen according to the density and viscosity (Butler, 1981)
For any one of these curves, the injection pore volume (PV) number is negatively correlated with the injection temperature
Parameter Permeability, mD Porosity, % Initial oil saturation, % Residual oil saturation, % Reservoir temperature, °C Initial oil viscosity under reservoir temperature, cp Net thickness, m Injection rate, cold water equivalent,m3/day Steam quality, fraction Total day of calculations, days Injection PV number Injection temperature (°C) Average oil saturation after steam flooding predicted by Formula (31), fraction Displacement efficiency predicted by Formula (30), fraction Average swept volume efficiency by reference 6 (%) Maximum recovery forecasts by this article
Summary
Oil reserves in the world can be classified into light oil, heavy oil and bitumen according to the density and viscosity (Butler, 1981). (3) according to the requirements of high temperature relative permeability and oil displacement efficiency measurement standards, the unsteady method with constant speed was used to inject steam and hot water until the oil was not released at the outlet.
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