Optimization of Fluorinated Wettability Modifiers for Gas-condensate Carbonate Reservoirs (SPE 154522)

A significant reduction in well productivity of gas-condensate reservoirs occurs owing to reduced gas mobility due to the presence of liquid condensate/water phases around the wellbore. Fluorinated chemicals as wettability modifiers are capable of delivering a good level of oil and water repellency to the rock surface, make it intermediate gas-wet and alleviate such liquid impairments. The main objective of this experimental work has been to propose an effective chemical treatment process for carbonate rocks, which in comparison to sandstone rocks, suffer from lack of information in this area. Screening tests including contact angle measurements, spontaneous imbibition tests and compatibility tests with brine were performed mainly using anionic and nonionic fluorosurfactants. The anionic chemicals were sufficiently effective on positively charged carbonate surfaces to repel the liquid phase, whilst the nonionic chemicals showed an excellent stability in brine media. A new approach of combining anionic and nonionic chemical agents is proposed to benefit from these two positive features of an integrated chemical solution. A number of low and high permeable carbonate cores have successfully been treated by chemicals selected through thorough screening tests. Optimization of solvent composition and filtration of solution before injecting chemicals into the core proved very effective to reduce/eliminate the risk of possible permeability damage due to deposition of large chemical aggregates on the rock surface. The chemical solution optimized in this study can be applied as an efficient wettability modifier for mitigating the negative impact of condensate/water banking in carbonate gas-condensate reservoirs.