Известия Томского политехнического университета: Инжиниринг георесурсов (Oct 2018)
Mathematical model of hydrogen sulfide injection into a reservoir partially saturated with water
Abstract
The relevance of the research is related to the development of theoretical foundations of underground disposal technologies for hydrogen sulfide produced by industrial facilities for reducing its emission into the atmosphere. The paper considers the method of hydrogen sulfide utilization in the gas hydrate state, in which the same amount of gas can be stored at significantly lower pressures. The aim of the research is to study the features of formation of H 2 S gas hydrate when injecting liquid hydrogen sulfide into a porous reservoir. Object of the research is a porous formation saturated with oil and water, the initial pressure of which is lower than the equilibrium pressure of formation of hydrogen sulfide gas hydrate. Methods. B Based on the equations of continuum mechanics the authors have developed the mathematical model of heat and mass transfer in a natural reservoir, accompanied by formation of hydrogen sulfide gas hydrate. It is assumed that in the case under consideration, three characteristic zones and, respectively, two moving interphase front arise in the reservoir: between the first and the second zones where the water completely passes to the gas hydrate state (the hydrate formation front) and between the second and the third zones where oil is displaced by hydrogen sulfide (displacement front). Using the method of reduction to the self-similar variable the authors constructed the analytical solutions for the dimensionless pressure and temperature values in each of the three regions of the reservoir and studied the dependence of the coordinate and temperature of the interface boundaries on the temperature of the injected hydrogen sulfide and the initial temperature of the formation. Results. It was established that the coordinate of the formation front of H 2 S gas hydrate decreases, and the temperature of the front of oil displacement by hydrogen sulfide increases when the initial temperature of the formation and temperature of injected liquid hydrogen sulfide grow. It is shown that at sufficiently low values of reservoir temperature and injected hydrogen sulfide, the coordinates of hydrate formation and displacement fronts can be aligned. The authors constructed the solution maps in the parameter plane «injection temperature - the initial temperature of the reservoir», i. e. critical diagrams that determine the existence of a mode in which the front of oil displacement by hydrogen sulfide is ahead of formation front of H 2 S gas hydrate.
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