A three-dimensional model was built, representing one fourth of an inverted nine-spot flood pattern, and several parameters significant to oil recovery by steam flooding were scaled in the model size. The model was designed to simulate steam flooding of an extra-heavy oil reservoir in Xinjiang Oil Field in which the reservoir is shallow and thin. The growth of steam chamber and the mitigation of oil and water were monitored by using 243 thermocouples and 15 pressure transducers. Three different well configurations were investigated-vertical injection and vertical production well-group, vertical injection-horizontal production well-group and horizontal injection-vertical production well-group. Numerical simulation of steam flooding processes using different well configurations was performed. The CMG-STARS thermal simulator was used to simulate the data from the present steam flooding experiments.
The experimental results indicated that the combination of vertical and horizontal wells plays weak roles for improving steam flooding in the experimental model, because of the limited contribution by gravity drainage. The Maximum oil recovery was observed during the vertical injection-vertical production well-scheme with follow-up. During the early stage of the runs, the oil production rate and oil steam ratio of horizontal injection-vertical production well-scheme is significantly lower than those observed in other two well-schemes. For all of the three different well configurations, steam override severely affects the oil recovery ratio due to the low output from the lower part of the reservoir, which is the further research focus to improve oil recovery. Reasonable agreement is found between the results from the history-matched numerical simulation and those of the experiments for oil production rate, cumulative oil production and temperature profiles in the model.