Hydrate Size Measurements in Anti-agglomeration at High Watercut by New Chemical Formulation

Abstract

Risk management of gas hydrates is a major challenge in offshore hydrocarbon production. Use of anti-agglomerants (AAs) is an attractive option because of effectiveness at low dosage and high subcooling. The literature suggests that anti-agglomeration requires formation of water-in-oil emulsion. Our recent work has demonstrated that the process can occur without emulsion or through oil-in-water emulsion. We have shown anti-agglomeration in oil-free systems in methane hydrates and natural gas hydrates. In this work, through particle size measurements in an autoclave setup in both freshwater and brine, light is shed on the effectiveness of our chemical formulation. Hydrate particle sizes are determined by the focus beam reflectance measurement (FBRM). The results show that our formulation reduces hydrate particle size significantly and eliminates large particles. The AA formulation is a mix of three chemicals: surfactant, base, and oil (e.g., n-octane). n-Octane helps with even distribution of the surfactant in the solution. The base helps with elimination of small amounts of hydrogen ions in the aqueous solution in conditions when acid gas species are present in the natural gas. These two additives increase the effectiveness of the surfactant for anti-agglomeration. Hydrate particle size measurements show that small amounts of n-octane reduce particle sizes by a factor of 2. Our measurements reinforce the idea of effective anti-agglomeration to be the most feasible approach in hydrate flow assurance, with superiority over other alternatives. The formulation has many features, including viscosity reduction of slurry.