Experimental investigation on the recovery performance and steam chamber expansion of multi-lateral well SAGD process

Abstract

Multi-lateral well SAGD process is a newly proposed recovery process in recent years, in which a multi-lateral well is applied to replace the horizontal well in classic SAGD process. In this paper, a three-dimensional physical model is applied to simulate the recovery performance of multi-lateral well SAGD process in heavy oil reservoirs. First, on the basis of Pujol-Boberg similarity criterion, the Forchheimer's law is introduced to deal with the similarity of model permeability in 3D experiment. Thus, from the actual properties of Long Lake heavy oil reservoir, the lab scale experimental parameters are obtained. Then, by using a multi-lateral wellbore model, four scaled 3D SAGD experiments are performed, including one conventional dual horizontal well SAGD experiment (base case) and three multi-lateral well based SAGD experiments. From the experimental observation, the advantages of multi-lateral well are discussed from liquid production and steam chamber expansion. Finally, by the collected images, the distribution of residual oil saturation after SAGD process is also discussed. Results indicate that the introduction of Forchheimer's law can effectively handle with the problem of kinetic similarity damage caused by high permeability during a 3D experiment. Compared with the conventional dual horizontal well SAGD process, the application of multi-lateral well can increase the oil recovery factor by above 15%. To some extent, the application of multi-lateral well can increase the duration time of plateau stage or wind down stage. Simultaneously, compared with the single application of multi-lateral well in SAGD well pair, a dual multi-lateral well SAGD process has a higher expansion rate of steam chamber and a shorter recovery time. For steam chamber, under the dragging mechanism of branch wellbore, the shape of steam chamber is a “inverted trapezoid” shape instead of the “inverted triangle” shape for conventional dual horizontal well configuration. Under the effect of branch wellbore, steam chamber can effectively reach to the reservoir boundary and increase the volume of steam chamber. The residual oil saturation mainly distributed around the reservoir boundary, which is far from the main wellbore and branch wellbore. This paper further clarifies the EOR mechanisms and steam chamber expansion rules of multi-lateral well SAGD process.