Simulation Study of 2-D SAGD Experiment and Sensitivity Analysis of Laboratory Parameters

Abstract

Abstract Bitumen resources constitute a high portion of the total world oil resources. The main recovery mechanism for these high viscous fluids is to reduce their viscosity by the application of heat, mostly by introducing steam. Among different steam injection schemes, steam assisted gravity drainage (SAGD) has become the method of choice applicable to bitumen and oil sand reservoirs. In these extra heavy oil reservoirs the reservoir has almost no injectivity due to high oil viscosity, and therefore conventional steam flooding is hard to conduct. SAGD, however, reduces the viscosity of bitumen in place and the heated bitumen drains due to gravity forces towards the production well and is then being produced. Our simulation study is based on the experimental work done by Chung (1988) and the simulation model of this experiment by Chow (1993). Chung's physical experiment was a 2-D model to simulate SAGD experiment in laboratory. A reservoir simulation model was built using a numerical thermal reservoir simulator. The model was then tested and validated with Chung's physical model. Having a valid model, sensitivity analysis was run to examine the effect of different simulation parameters on recovery and steam oil ratio. The sensitivity parameters tested are steam temperature and quality, the permeability of the model, both horizontal and vertical, different well placement schemes, and the effect of grid refinement. High permeability was found to have a profound effect on recovery. Different steam temperatures and qualities were examined. The best injection condition was found to be 130 °C and 90% quality, beyond which no increased recovery was achieved. Different injector and producer placements were tested. Placing injector and producer diagonally in the model showed the best horizontal sweep efficiency in the laboratory model. The Chung's experiment was done with Cold Lake crude oil. Our model was tested using bitumen with higher viscosity from Athabasca and results showed that in order to get the same recovery as in the Cold Lake case; the temperature must be increased to 140 °C as compared to 100 °C for the case with lower viscosity oil.