Abstract

Quantities of mature oil fields in the North West (NW) Shelf of Western Australia are characterized by high water cut and poor productivity, which makes them potential candidate for Enhanced Oil Recovery (EOR). In recent years, CO2 foam flooding has been widely recognized as a promising EOR method in terms of its outstanding ability to increase swept volume as well as improving the displacement efficiency.

In this paper we present the experimental investigation on the feasibility of applying CO2 foam flooding in mature oil fields in Western Australia. A procedure was firstly developed to screen ideal foaming agents at reservoir condition; furthermore, core flooding was performed to optimize operation parameters such as injection mode and volume ratio of aqueous phase to CO2.

The results demonstrate: 1) among a number of commonly used surfactants, AES exhibited the highest foambility and stability; 2) by adding 1.2% additive triethanolamine and 1500ppm polymer (AVS) into 0.5% AES solution, the stability of CO2 foam would be improved significantly without affecting the foamability considerably; 3) the foam stability increased with foam apparent viscosity; 4) the ultimate recovery of direct injection of foam was 7.72% and 4.09% higher than that of co-injection of solution and gas and surfactant-alternating-gas respectively; 5) under optimal flow rate and volume ratio of aqueous phase to gas phase, the oil recovery could go up to 30.05% after the water flooding.

Through systematic and thorough research, CO2 foam flooding has been shown to be a viable and effective EOR method assisting in maintaining the production in mature oil fields in the NW Shelf of Western Australia.

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