H.C. Tan & Bharat Mody, Halliburton Services
Typically, channels or streaks of high permeability develop after a period of time in CO2 injection programs. To help prevent injected CO and water from bypassing Recoverable oil polymer is injected which alters permeability to permit injected CO2 and water to contact previously bypassed oil-bearing formation. With the development of the laboratory apparatus described in this paper, significant improvements have been made in analyzing and designing polymer injection strategies to improve conformance control. The apparatus consists of a parallel series of cores of varying permeability to simulate variations in formation permeability. These cores are subjected to sequential injection of CO2 and water, followed by polymer injection. Effects of polymer injection on formation permeability are then evaluated. Results of studies conducted using this laboratory apparatus have led to findings regarding: 1. Selection of a nonionic organic crosslinked polyacrylamide polymer which is stable in the low pH environment of supercritical CO2. 2. Determination of an optimum treatment size to preferentially alter permeability to improve conformance control. 3. Long term effects of the CO2 environment on stability of injected polymer.