PERFORMANCE OF SWAG INJECTION VERSUS ALTERNATING AND CONTINUOUS INJECTION OF WATER AND GAS IN LOW GAS-OIL IFT AND MIXED-WET SYSTEMS

摘要

In some reservoirs, gas and water are both available for injection as a means of improving recovery. In such cases it may be advantageous to inject a combination of gas and water either alternately (WAG) or simultaneously (SWAG). Obviously, gas or water can also be injected separately and continuously. Unfortunately, little experimental evidence, under reservoir conditions, is available to allow a direct comparison of the performance of these various injection strategies. Operationally, SWAG injection may be less problematic compared to WAG as it avoids significant pressure and temperature swings associated with WAG injection. However, there are many other parameters that may affect economic evaluation of these processes. We report the results of a comprehensive series of well-controlled core-flood experiments which includes continues gas injection (CGI), two series of WAG, and two series of SWAG injection tests. The difference between the two WAG experiments is the order in which gas and water injection is carried out. The first WAG test started with water injection whereas the second WAG experiment started with gas injection. The difference between the two SWAG experiments is the gas/water ratio, which was 0.25 for the first one and 1.0 for the second SWAG test.