Single Well Pilot Test of Near Miscible CO2 Injection in a Kansas Arbuckle Reservoir

摘要

A recent study showed that CO2 injection at pressures below minimum miscibility pressure (MMP) improves oil recovery with Arbuckle reservoir core samples at near miscible conditions. To demonstrate its applicability on a larger scale, a single well pilot test was designed to experimentally inject CO2 into the Arbuckle formation at pressures below MMP to determine the efficiency of CO2 displacement at near miscible conditions. The pilot test consists of a single-well chemical tracer (SWCT) test before and after CO2 injection on a selected well producing from the Arbuckle formation. The reservoir operating pressure was 1,150 psi while the MMP of the oil was 1,500 psi at 106 °F (reservoir temperature). The first chemical tracer test was performed to determine the oil saturation in the formation prior to CO2 injection. This was followed by injecting approximately 17 tons of CO2 at pressures below MMP with a follow up water displacement, followed by a second tracer test performed to determine the remaining oil saturation. The oil saturation measured from the two tracer tests were 0.23 and 0.20, respectively. A reduction of oil saturation by 0.03 represents a 13% improvement of oil displacement which results from CO2 injection at near miscible conditions. The test results indicate the potential of using near miscible CO2 to improve oil recovery in Kansas Arbuckle reservoirs and others where MMP cannot be achieved.