Possibilities of Application of a Mixed Hydrate Formation Inhibitor Based on Methanol and Monoethylene Glycol

Currently, two thermodynamic hydrate inhibitors are used in Russia: methanol and monoethylene glycol (MEG). Application of MEG is primarily driven by environmental aspects. However, using MEG in Russian gas condensate fields has several drawbacks: to reduce viscosity and the freezing point, it must be diluted with water, which reduces its anti-hydrate activity. This paper discusses a mixture of two thermodynamic inhibitors. The mixed inhibitor methanol + MEG (with MEG predominating in the mixture), combines the low content of methanol vapor in natural gas with the low freezing point and viscosity of the inhibitor solution. This paper considers the methodology of MEG + methanol inhibitor application, as well as the calculation technique of specific inhibitor consumption for hydrate control in a low-temperature gas separation unit (LTS), particularly in offshore gas condensate fields. Using a mixed inhibitor instead of an aqueous MEG solution (80 wt %) has been shown to reduce specific inhibitor consumption by up to two times. This approach also allows lowering the gas separation temperature from –23 to –30°C, which increases the yield of hydrocarbon condensate. The potential of dual-reagent technology at underground gas storage (UGS) facilities is also being analyzed. Wells and gas gathering systems are treated with methanol, and concentrated aqueous MEG is fed to the LTS unit to form a mixed inhibitor directly in the unit. This approach decreases the technological losses of methanol with the treated gas, thereby reducing the overall loss of the inhibitor.