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Experimental Investigations of DDP and SCWD in a Naturally Fractured Reservoir, HP/HT

The use of the Double Displacement Process (DDP) has received considerable interest as a method of Enhanced Oil Recovery (EOR). The DDP has already studied in several fields and yielded promising results. This process consists of injecting gas into waterflooded oil zones. The Second Contact Water Displacement (SCWD) Process is an extension of the DDP and consists of injecting water after a DDP. In general, fractured reservoirs have always been considered poor candidates for enhanced oil recovery; this is mainly due to the complexities involved in predicting performance in such reservoirs. This paper investigates the efficiency of oil recovery using DDP and SCWD in a group of fractured cores. It was necessary to stack several core plugs in order to obtain accurate volumetric results. Two experiments were designed to illustrate both natural depletion and tertiary gas injection under extreme conditions; it means 5520 psi and 280.4 o F (HP/HT). Natural and nitrogen gas were used during the experiments. Results indicate that injection of natural gas in naturally fractured reservoirs with light oils could significantly recover more oil, compared to N2 injection (DDP). The study reveals that a significant amount of residual oil will be recovered by tertiary gas injection in a mature oil field where the water injection has been used during a long period. Finally, a second water displacement (SCWD) was carried out to evaluate additional recovery factors.