This research was aimed at investigating the effect of well configuration on SAGD performance and developing a methodology for optimizing the well configurations for different reservoir characteristics. The role of well configuration in determining the performance of SAGD operations was investigated with help of numerical and physical models.
Since mid 1980’s, SAGD process feasibility has been field tested in many successful pilots and subsequently through several commercial projects in various bitumen and heavy oil reservoirs. Although SAGD has been demonstrated to be technically successful and economically viable, it still remains very energy intensive, extremely sensitive to geological and operational conditions, and an expensive oil recovery mechanism. Well configuration is one of the major factors which affects SAGD performance and requires greater consideration for process optimization.
Several well patterns were numerically examined for Athabasca, Cold Lake and Lloydminster type of reservoirs. Numerical modeling was carried out using a commercial fully implicit thermal reservoir simulator, Computer Modeling Group (CMG) STARS. For each reservoir, one or two promising well patterns were selected for further evaluations in the 3-D physical model or future field pilots.
Three well patterns including the Classic SAGD pattern, Reverse Horizontal Injector, and Inclined Injector, of which the last two emerged as most promising in the numerical study, were examined in a 3-D physical model for Athabasca and Cold Lake reservoirs. The physical model used in this study was a rectangular model that was designed based on the available dimensional analysis for a SAGD type of recovery mechanism. Two types of bitumen representing the Athabasca and Cold Lake reservoirs were used in the experiments. A total of seven physical model experiments were conducted, four of which used the classic two parallel horizontal wells configuration, which were considered the base case tests. Two experiments used the Reverse Horizontal Injector pattern and the last experiment tested the Inclined Injector pattern. The suggested well patterns provided operational and economical enhancement to the SAGD process over the standard well configuration and this research strongly suggests that both of them should be examined through field pilots in Athabasca/Cold Lake type of reservoirs.
In order to develop further insight into the performance of different well patterns, the production profile of each experiment was history matched using CMG-STARS. Only the relative permeability curves, porosity, permeability, and the production constraint were changed to get the best match of the experimental results. Although it was possible to history match the production performance of these tests by changing the relative permeability curves, the need for considerable changes in relative permeability shows that the numerical model was not able capture the true hydrodynamic behavior of the modified well configurations.