The paper presents the results of an experimental study of the behaviour of formation and decomposition of natural gas hydrates of the Srednevilyuiskoe and Otradninskoe gas condensate fields depending on the concentration of sodium bicarbonate solution. Natural gases used in the hydrate formation process differ in their component composition and physicochemical properties. It was found that with increasing concentration of solutions, the gas pressure at which the hydrate formation process ends is increased. During hydrate formation, the initial dry natural gas of the Srednevilyuiskoe field turns into semi-wet gas, and that of the Otradninskoe field turns into wet gas. The decomposition of natural gas hydrates is described by sigmoid curves without an induction period. For the decomposition reaction of hydrates formed by natural gas of the Srednevilyuiskoe field, the reaction acceleration period is shorter than the deceleration period, while the opposite is observed for the Otradninskoe field. Therefore, in the first case, hydrates decompose faster than in the second. Thus, it was found that the hydrate formation process in model solutions of the sodium bicarbonate type and the decomposition reaction of the resulting hydrates depend on the composition of natural gas.
The use of methanol as an inhibitor of hydrate formation in the fields of the Far North is fraught with environmental risks and a threat to the health of personnel. Therefore, an urgent task is to find an analytical method for determining the methanol content in water-methanol solutions instead of the areometric method. One of such methods is Raman spectroscopy. In this work, water-methanol solutions used at the Otradninsky gas-condensate field are investigated. For the quantitative determination of the inhibitor content in water-methanol solutions samples, the stretching vibration bands of the CH groups of methanol molecules was selected, the intensity of which monotonously increases with increasing alcohol concentration. A comparison of the mass concentrations of methanol obtained by different methods showed that the presence of salts in water methanol solutions leads to an underestimation of the alcohol content. This entails an excessive consumption of inhibitors and an increase in the cost of gas companies to purchase and transport methanol.
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