Optimization of Fluorinated Wettability Modifiers for Gas-Condensate Carbonate Reservoirs
- Jalal Fahimpour (Heriot-Watt U.) | Mahmoud Jamiolahmady (Heriot-Watt U.) | Romain Severac (DuPont) | Mehran Sohrabi (Heriot-Watt University)
- Document ID
- Society of Petroleum Engineers
- SPE Europec/EAGE Annual Conference, 4-7 June, Copenhagen, Denmark
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 1.8 Formation Damage, 5.2.1 Phase Behavior and PVT Measurements, 5.8.7 Carbonate Reservoir, 1.2.3 Rock properties, 5.8.8 Gas-condensate reservoirs, 5.1 Reservoir Characterisation, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.2 Reservoir Fluid Dynamics, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating, 4.6 Natural Gas, 5.4.2 Gas Injection Methods, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.6.9 Coring, Fishing
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Significant reduction in well productivity of gas-condensate reservoirs occurs owing to reduced gas mobility arising from the presence of condensate/water liquid phases around the wellbore.
As wettability modifiers, fluorinated chemicals are capable of delivering a good level of oil and water repellency to the rock surface, making it intermediate gas-wet and alleviating such liquid blockage.
The main objective of this experimental work has been to propose an effective chemical treatment process for carbonate rocks, which have received much less attention in comparison to sandstone rocks. Screening tests, including contact angle measurements and compatibility tests with brine, were performed using mainly anionic and nonionic fluorosurfactants. On positively charged carbonate surfaces the anionic chemicals were sufficiently effective 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 permeability carbonate cores have been successfully treated using chemicals selected through screening tests. Optimization of solvent composition and filtration of the solution before injecting chemicals into the core proved very effective in reducing/eliminating 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.
Well productivity of many gas-condensate reservoirs can suffer considerably from reduced gas mobility due to accumulation of liquid phases, i.e. condensate and water, around the wellbore. A significant productivity loss of 50% in the Arun field has been attributed to the accumulation of fall out condensate from a fairly lean gas, with a maximum liquid dropout of 1.1% (Afidic et al., 1994). A sharp decline in gas production rate from a tight reservoir in the Cal Canal field was also noticed soon after the well bottom-hole pressure fell below the dew point pressure. The presence of liquid hydrocarbon and of water in the vicinity of wellbores were considered as the main restricting parameters making only 10% of original GIP recoverable from this reservoir (Engineer, 1985). A large number of theoretical and experimental studies have been devoted to understanding, modeling and predicting the condensate accumulation and its associated impaired well productivity (O'Dell and Miller, 1967; Fussel, 1973; Danesh et al., 1991; Henderson et al., 1993, 1995; Fevang and Whitson, 1996; Mott, 2002; Jamiolahmady et al., 2003).
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