Proposed Technique for Improved Oil Recovery from Thin Oil Rim Reservoirs with Strong Aquifers and Large Gas Caps

Abstract

AbstractOil production from thin oil rim reservoirs with strong aquifers and large gas caps is challenging due to early gas and water breakthrough, movement of the fluid contacts and low oil recovery factor. One means of handling the problems associated with thin oil reservoirs is the use of horizontal wells which improves recovery factor. This work however proposes a measure through which gas injection into the reservoir is used to improve oil recovery factor and minimize water production using vertical wells. A simulation study was carried out using the data from a thin oil rim reservoir in the Niger Delta. The five cases studied are the base case (using conventional vertical wells), use of horizontal wells, water production and disposal, water production and re-injection into the oil zone to improve recovery, and gas injection at the oil water contact.The recovery factor and volume of produced water were compared for all five cases for a production period of 40years. An oil recovery factor of 25%, 29%, 40%, 33% and 44% were obtained for the base case, use of horizontal wells, water production and disposal, water production and re-injection to improve recovery, and gas injection at the oil water contact respectively. Volume of produced water was lowest while the GOR was highest for the proposed method than any other method. The main disadvantage using the approach of injecting gas at the water oil contacat is the high GOR however; recycling the gas by injecting the produced gas back into the gas cap is a viable solution. The relatively higher oil recovery factor and minimal volume of produced water which are highly desired for effective production from thin oil reservoirs makes the proposed technique worth investigating.