A Laboratory Study of Oil Recovery by Nitrogen WAG injection in Berea Sandstone Rock

This work concerns to experimentally investigate the nitrogen immiscible WAG injection in Berea sandstone rocks which has been rarely attended in the available literature. Flooding tests were conducted on a 30 cm length Berea sandstone core sample at reservoir conditions and the influences of injection rate and WAG ratio on breakthrough time, early recovery and ultimate recovery were investigated. Relatively long core size makes it attractive to be a more reliable representation of flow through reservoir rocks. Nitrogen, 5000 ppm NaCl brine, and Kerosene were used as working fluids. The results revealed that among 4 different flow rates implemented in the experiments, 0.4 cc/min is optimum. Three screening factors, higher early and final recovery and lower gas production (after breakthrough) are considered for selecting the optimal rate. In addition, the results of the experiments performed at different WAG ratio, and at optimum rate, showed that there is an optimum WAG ratio, 2, in which the oil recovery is maximized. This work illustrates that if the parameters influencing WAG injection are thoroughly investigated, it can achieve a high recovery in Berea sandstone even with a cost-effective choice of Nitrogen in immiscible conditions where no other better alternative is economically available.