Assessment of Foam for GOR Control to Optimize Miscible Gas Injection Recovery

Abstract

Miscible gas flood in a CEPSA-operated oil field has matured and, over the years, oil has been produced at an increasing gasoil ratio (GOR). Even though the gas displacement mechanism is miscible, or close to miscible, the poor mobility ratio between injected gas and displaced oil has led to inefficient sweep of the reservoir.The use of foam for gas mobility control is a proven IOR technology that can greatly improve gas injection conformance and hence improve volumetric sweep efficiency in secondary or tertiary recovery processes. This paper presents the results of comprehensive laboratory studies undertaken to define a foam system that will reduce gas mobility and preclude any risk of affecting formation injectivity.We evaluated four surfactants to establish the Foaminess, Mobility Reduction Factor (MRF) and impact of hardness, oil presence and surfactant concentration on foam strength: AOS C12-14 and AOS C14-16, LAS and Fluorobetaine. We found AOS C12-14 and AOS C14-16 to be the best foamers under screening conditions (60 bar, 90 ºC): both significantly reduced mobility. AOS was not brine-sensitive but in the presence of oil, the foam performance was reduced. Optimum concentration regarding cost and effectiveness was found to be 5000 ppm. We demonstrated that strong foam can be formed under reservoir conditions (200 bar, 96 ºC), using the Surfactant-Alternating-Gas injection technique.We have submitted a request for approval of a field pilot test which will be the first application of foam as an IOR technology in this field. If success is demonstrated in the field, the proposed approach should be helpful for field operators facing similar production optimization challenges or, for example, Foam-Assisted Water Alternating Gas (FAWAG) projects.

Evaluation of oil-tolerant foam for enhanced oil recovery: Laboratory study of a system of oil-tolerant foaming agents

“…As the results show, the FC surfactant and SDS foaming agent system are expected to be stable in the presence of oil. This observation of FC surfactants is consistent with results obtained by Cubillos et al (2012). However, the water and oil repellency of the FC molecular structure led to its lower foam ability than that of SDS.…”

“…This is because the lower the concentration, the fewer adsorbed surfactants molecules are on the gasliquid interface, thus resulting in its poor foaming ability. As the concentration increases, the SFT of foaming agent decreases and its foaming ability improves (Cubillos et al, 2012).…”

“…However, the field applications of fluorinated surfactants have limitations, such as higher costs and environmental problems. Cubillos et al (2012) evaluated four surfactants (LAS, AOS C 12-14 , AOS C 14-16 , FBET) to establish foaminess and foam stability in the presence of oil, and their study showed that AOS C 14-16 had the best performance of all formulations and was sufficient for field application. In contrast, other studies (Dalland et al, 1994) indicated that AOS surfactant exhibited poor blocking performance and failed to generate foam in the presence of oil.…”

A review of gas enhanced oil recovery schemes used in the North Sea

“…AOS surfactants are very good foaming agents and can significantly reduce gas mobility. They have been used successfully in the North Sea (Cubillos et al 2012). However, high pressures above 400 bar may limit foam formation.…”

Laboratory Analysis of Foam Generating Surfactants and Their Thermal Stability for Enhanced Oil Recovery Application

“…In the chemical EOR, anionic surfactants are widely used because of their low adsorption on sandstone reservoirs. AOSc12-14 anionic surfactant is proved to be an excellent foam insensitive to brine composition and tolerant to presence of crude oil [14]. Nonionic surfactants are used as co surfactants to improve system phase behavior.…”