CO2 Flooding to Increase Recovery for Unconventional Liquids-Rich Reservoirs

The rising energy demand is causing the petroleum industry to develop unconventional oil reservoirs; however, the primary recovery factor is low in these types of reservoirs. Alternative methods to increase recovery need to be studied. This paper analyzes the impact of CO2 flooding a sector of the Elm Coulee field using reservoir modeling. The sector is two miles by two miles and consists of six original single-lateral horizontal wells. Two different reservoir models are built for the sector: a primary recovery black oil model and a CO2 flood solvent model. They are used to determine the additional recovery due to a CO2 flood. Furthermore, the CO2 flood model is executed with different scenarios to determine the best well locations and injection schemes. The models demonstrate that CO2 flooding horizontal wells in the Elm Coulee field increases production. Comparison of vertical and horizontal injection techniques indicates continuous horizontal CO2 injection is more efficient; it yields higher injection rates, and it is also beneficial for long-term recovery. Focusing on horizontal injection, the best scenario involves the practice of drilling new injectors and producers along with converting existing producers to injection wells. In order to satisfy production requirements, production wells can be drilled such that there is an injector between two producers. This type of arrangement on horizontal injection increases the field recovery factor over 15% after eighteen years of injection.