Effect of foam and WAG (water alternating gas) injection on performance of thin oil rim reservoirs

Abstract

A design of experiment was used to create oil rim models from a wider range of reservoir, operational and reservoir architecture parameters. A response surface model was generated based on a concurrent oil and gas production and a Pareto analysis was conducted to ascertain the significance of the parameters. The models were classified based on the Pareto analysis and due to the low oil recoveries arising from the complexity of oil rims, a series of secondary injection schemes were instigated. The results from the models indicated an optimum 2 cycle WAG up dip injection and WAG down dip injection for thin oil rims. Also the results estimated an incremental oil recovery of 9.2% and 30.1% with respect to base case (no injection) for WAG up dip injection and 10.66% and 6.11% for WAG down dip injection while an incremental recovery of 14.2% and 52.74% for up dip foam injection and 18.19% and 29.73% incremental oil recovery for foam down dip injection for oil rim model ‘3’ with large gas cap and large aquifer and model ‘7’ with small gas cap small aquifer respectively. A case study reservoir from the Niger delta region of Nigeria showed an 8.57% and 8.56% incremental oil recovery for foam up dip and foam down dip injection and incremental oil recovery of 8.35% and 7.94% for WAG up dip and WAG down dip injection. This paper will provide useful information as to the extent of oil recovery in different oil rim models under different foam and WAG injection.