Mathematical model of hydrogen sulfide injection into a natural reservoir accomponied by its hydrate formation

Based on the equations of mechanics of multiphase media, a mathematical model of liquid hydrogen sulfide injection into a porous formation saturated with oil and water is developed. To describe the processes of heat and mass transfer in the porous medium, the combined equations including mass and energy conservation laws, Darci's law, and the equation of state are used. Self-similar solutions to the problem, in which three characteristic areas are formed in the reservoir, are obtained. In the first area (the nearest region), the porous are saturated with liquid hydrogen sulfide and its hydrate; in the second area (intermediate region), there is water and liquid hydrogen sulfide; and in the third area (distant region), the porous are saturated with oil and water. Self-similar coordinates of the interphase borders are studied as functions of permeability of the reservoir and its initial pressure. It is established that increase in the initial pressure of the reservoir and decrease in its permeability cause a decrease in the velocity of oil displacement by hydrogen sulfide. It is shown that in conditions of low permeability of the reservoir and high initial pressure, the merge of interphase boundaries could happen. The dependences of critical values of injection pressure, corresponding to a merge of interphase boundaries, on the permeability of the reservoir and its initial pressure are found.

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