Research of Influence Preliminary Water Compression to the Processes of Methane-Containing Gas Mixtures Hydrate Formation

Abstract

Currently, the supply of a thermodynamic hydrate inhibitor (THI) increasing is the most common measure to prevent the formation of hydrates of gas transmission systems. It is proposed to improve the test procedure for calculating the consumption of inhibitors. By the method of Kinetic (K) and Hydrate Stability Zone (HSZ) the study of the formation and decomposition of gas hydrate phase was led in the mercury-free installation of GHA (Vinci Technologies, France). The moment of formation and decomposition of the gas hydrate phase is determined by the method of recording the pressure deviation from the reference one and duplicated visually.The substance of the methane-containing gas mixture is determined by the results of the analysis using a chromatograph SHIMADZU GC 2014. The gas mixture as natural gas of the Yuzhno-Kirinskoye Gas Condensate Field is used in the studies as follows: Methane [CH4] 91.28%, Ethane [C2H6] 3.74%, Propane [C3H8] 1.61%, Carbon dioxide [CO2] 1.87%, Butanes [C4H10] 0.37%, [i- C4H10] 0.28%, Pentanes [C5H12] 0.04%, [i-C5H12] 0.09%, [neo-C5H12] 0.001%.The measurements are carried out in the temperature range from -2°C to 20°C and pressures from 6 MPa to 11 MPa (930-1560 PSI). Cycles of the formation and decomposition of the gas hydrate phase are carried out in samples with water previously subjected to a pressure of 50 MPa and 10 MPa. The difference in experiments is described by the methods of Kinetics (K) and Hydrate Stability Zone (HSZ).It has been established that during the calculation of THI concentration, it is necessary to carry out additional tests of samples of the gas mixture and water, which was subjected to the preliminary exposure to high pressure, to prevent hydrate formation. The formation of hydrates in such samples occurs earlier than in standard tests.The increase in the incubation period of hydrate formation in repeated experiments with pre-prepared water indicates the flow of the equilibrium process of redistribution of the proportions of the cubic structures sI and sII. The process takes place in the system for a long time during several cycles of formation and destruction of the hydrate phase.