Application of horizontal wells for cyclic steam stimulation (CSS) in bitumen recovery: production optimization through reservoir simulation

Abstract

By declining conventional oil resources, global attention has turned to unconventional ones. Nonetheless, the heavy and viscous nature of bitumen prevents its flow at reservoir condition, which has paved the way for the progressive development of in situ thermal methods to lower the viscosity of bitumen and increase its mobility. Cyclic steam stimulation (CSS) is an alternative method to recover bitumen at higher depths. Using CSS in conjunction with horizontal wells extends the advantages of this method by increasing sweep efficiency, contact area opened to flow, and steam injectivity. In this study, the performance of CSS in the Athabasca region during 10 years was studied and sensitivity analysis of operational parameters was carried out. The effect of various factors was investigated to find the optimum case. The model under study is a sector of Athabasca bitumen deposit which was simulated by CMG-STARS (version 2006.1). Black oil model was used to simulate the behavior of bitumen in porous media. The studied bitumen consists of 91.5% asphaltene and 8.5% maltene. Its viscosity during 10 years of production changed from 755.5 cp to 16.8 cp representing the viscosity reduction as a dominant mechanism of bitumen production. The maximum bitumen recovery factor in the base case was found to be 4.3%. In addition, optimum soaking time was determined to be 20 days.