Enhanced Recovery Of Light And Medium Crude Oil In Canada

Abstract

Abstract In Canada, the major enhanced oil recovery (EOR) technique for light and medium erode oils is Hydrocarbon Miscible Flooding (HCMF). A solvent (rich hydrocarbon gas) that is or will become miscible with the oil is injected to mobilize the oil down to a lower residual oil saturation than can be achieved under water-flood. A variety of reservoir conditions need to be considered in designing an HCMF. Monitoring the HCMF progress is necessary to optimize oil recovery. Many HCM floods, which are either vertical (gravity stable) or horizontal, have been implemented and accepted as being technically successful. These schemes have already produced a significant amount of incremental reserves and are expected to be a major contributor to Canadian oil production in the future. Introduction Enhanced oil recovery (EOR), as discussed here, is a means to increase light and medium oil recovery to a higher level than achievable by waterflooding. In Canada, as in other parts of the world, there are a variety of techniques being used or considered. The major ones are miscible flooding, immiscible CO2, flooding, polymer flooding, and chemical flooding. The following is a brief description of the different processes. Miscible (Hydrocarbon, CO2) Miscibility is defined as the physical condition where two or more fluids will form a single homogeneous phase when mixed in all proportions, that is, they mix without forming an interface. This results in a dramatic improvement in the displacement efficiency over that of a waterflood. The potential for hydrocarbon and CO2 miscible floods is well known as demonstrated by the number of projects in operation. The choice of solvent (miscible displacing fluid) to be used in a potential EOR scheme is primarily controlled by solvent availability. There are more developed sources of CO2 in the United States than in Canada and, as a result, there are more CO2 miscible flood projects in the U.S. High productivity natural gas wells (with associated natural gas liquids [NGL]) that would otherwise be shut in due to reduced market demand, serve as sources of solvent for HCMF projects in Canada. There now are 56 HCMF and 5 CO2 projects known to be operating in Canada. Immiscible (CO2) This process improves recovery because the CO2 mobilizes the oil by causing oil swelling and reducing oil viscosity. Currently, there are no known active projects in Canada. Polymer A high viscosity fluid (water with dissolved polymer) is injected into the reservoir to improve the mobility ratio between the displacing fluid and the oil. This technique has potential in specific situations (i.e. good reservoir quality with some higher permeability streaks and a viscous oil). There are five known projects now operating in Canada. Chemical Flooding This process usually involves the injection of surface active chemicals which are used to reduce the mobility ratio or mobilize trapped oil. The technique currently has limited economic potential because of the high cost of chemicals in comparison to the incremental recovery. At the present time, there are four known projects operating in Canada.