Abstract

The days of easy oil are going. The frontier of oil and gas exploitation continues to be pushed further as a result of oil price volatility, new technologies, and an ever dynamic political and economic atmosphere. Production by primary and secondary recovery have been known to only recover a limited fraction of the oil in place thus the need to look into more innovative ways to improve recovery especially in declining assets through suitable EOR methods.

Several EOR techniques have been developed for improving oil recovery from reservoirs one of which is Water Alternating Gas (WAG) injection. In this work, WAG is presented as a potential candidate to increase oil productivity in the Niger delta. WAG involves the cyclic injection of water and gas into the reservoir so as to squeeze out more oil. By decreasing gas mobility and capillary forces, guaranteeing effective microscopic displacement due to gas flooding and reducing the mobility ratio thus improving the macroscopic sweep created by water injection, it combines the advantages of water flooding and gas injection in optimizing residual oil production.

This study aims at investigating the possible increase in oil production and reserves from a Niger Delta field through the use of Immiscible WAG injection as an EOR process. In conducting this study, various development strategies such as Gas Injection, Water Injection and Immiscible WAG were proposed in exploiting the reservoir. Using a conventional 3-D numerical simulator to mimic the process, comparison was then made between the various strategies where results such as field oil recovery, cumulative oil recovery and production rate were analysed. With Immiscible WAG injection, an increase in recovery above the very popular gas injection or water injection was observed. Parameters critical to the success of a WAG enhanced oil recovery process such as three-phase flow, hysteresis effect, WAG cycle, WAG ratio, and Injection rates and their effects was also studied.

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