Field Foam Applications in Enhanced Oil Recovery Projects: Screening and Design Aspects

Abstract

Abstract An in-depth analysis was conducted for over forty foam applications in Enhanced Oil Recovery (EOR) projects, and numerous production well treatment operations involving the use of foam in cyclic steam operations and in gas miscible floods, to derive insights on screening and design aspects in such applications. Foam can be used to solve conformance problems caused by either a thief zone or gravity override; The proper identification of the cause, as well as of the production well(s) affected is basic to the definition of the problem. Either blocking/diverting foams or in-depth mobility control foams can be placed through the injection wells. On the other hand, foam treatment in production wells is done mainly to mitigate an override problem. The most important factors in foam assisted EOR projects were determined to be: (a) manner of foam placement in the reservoir (injection of pre-formed foam, co-injection foam and SAG or surfactant alternating gas foam), (b) reservoir pressure and c) permeability. While pre-formed foam are effective mainly in the treatment of the production wells, the co-injection foam and SAG can be employed for solving specific sweep efficiency problems in EOR projects. It is concluded that for designing a steam-foam project (which is essentially a low pressure foam application) a foam quality in the range 45% to 80% should be considered. In this kind of application, a co-injection foam is to be employed and the additives (surfactant and non-condensable gas) are to be injected intermittently (on and off), superimposed on a continuous steam injection. Injection cycles as short as 7 days (2 days-on and 5 days-off) should be considered. Under suitable conditions, an oil rate increase of 1.5 to 5 times, a decrease in water cut by 20 %, and an incremental oil recovery of 6%-12% OOIP can be achieved with such an implementation. At high pressure, such as in gas miscible flooding (CO2 and hydrocarbon gas), foam application can result in excessive mobility reduction factors, and injectivity reduction. Due to this reason, alternate injection of surfactant solution and gas (SAG foam) is favoured over a co-injection mode of placement. Recommendations for laboratory tests in support of a proper design of the field pilot are presented.