Device and method for measuring horizontal/vertical permeability of hydrate reservoir

A method for measuring a horizontal/vertical permeability of a hydrate reservoir, comprising the following steps:

• (1) loading a dried quantitative porous medium used for simulation into a hydrate reservoir horizontal/vertical permeability measuring apparatus;
• (2) starting an air compressor and a booster pump to inject a gas into a high-pressure gas tank to a required gas pressure;
• (3) injecting the gas from the high-pressure gas tank into the hydrate reservoir horizontal/vertical permeability measuring apparatus to a certain pressure to check tightness of the hydrate reservoir horizontal/vertical permeability measuring apparatus to ensure that the hydrate reservoir horizontal/vertical permeability measuring apparatus does not leak;
• then stopping the injection of the gas;
• (4) adjusting a temperature of a constant-temperature water bath surrounding the hydrate reservoir horizontal/vertical permeability measuring apparatus to a required temperature;
• opening a water circulation inlet and a water circulation outlet to allow water entering a cooling water/saturated methane water tank;
• opening an intake line of the cooling water/saturated methane water tank to allow methane gas entering the cooling water/saturated methane water tank through a bubbler so that the methane gas dissolves in the water sufficiently to produce methane water;
• adjusting a temperature of the methane water to the same temperature as the temperature of the constant-temperature water bath;
• (5) starting a water injection pump to inject the methane water into the hydrate reservoir horizontal/vertical permeability measuring apparatus and a related process;
• purging any air from the porous medium and a pipeline;
• adjusting a back pressure valve downstream of the hydrate reservoir horizontal/vertical permeability measuring apparatus to 5 MPa until a liquid in a gas tank with a balance scale has a constant flow rate and a liquid volume thereof is kept in balance with an injection volume from the water injection pump;
• (6) purging any air from a P1 horizontal differential pressure gauge, a P2 horizontal differential pressure gauge, a P3 horizontal differential pressure gauge, a P4 vertical differential pressure gauge, a P5 vertical differential pressure gauge and a P6 vertical differential pressure gauge to ensure that the pipeline is filled with the methane water;
• (7) adjusting a reaction vessel of the hydrate reservoir horizontal/vertical permeability measuring apparatus to a certain pressure, and monitoring data in real time by a reactor inlet pressure gauge, so as to keep a constant state;
• closing relevant gate valves to all the vertical differential pressure gauges;
• adjusting the reaction vessel to a certain pressure by monitoring pressure data in real time from the pressure gauge;
• then stopping the water injection pump;
• (8) injecting a portion of the gas from the high-pressure gas tank to displace the methane water in the hydrate reservoir horizontal/vertical permeability measuring apparatus having the reaction vessel, and adjusting the reaction vessel to a certain pressure;
• (9) starting the water injection pump again to inject the methane water from the cooling water/saturated methane water tank through the bubbler into the hydrate reservoir horizontal/vertical permeability measuring apparatus to a certain pressure, then again stopping the water injection pump;
• (10) allowing a hydrate to be synthesized to form a hydrate sample in the hydrate reservoir horizontal/vertical permeability measuring apparatus, and allowing completing a hydrate formation process after a period of time by isolating the reaction vessel with closed relevant gate valves;
• (11) adjusting the back pressure valve downstream of the hydrate reservoir horizontal/vertical permeability measuring apparatus to a required pressure;
• then opening the closed relevant gate valves;
• then, in a horizontal permeability test process, keeping the relevant gate valves closed to all the vertical differential pressure gauges, starting the water injection pump to inject the methane water into the hydrate reservoir horizontal/vertical permeability measuring apparatus at a constant speed until a first flow rate through the gas tank with the balance scale remains constant;
• checking a gas flow meter to ensure that the hydrate sample is not decomposed, and obtaining a change in different differential pressures of the hydrate sample in a horizontal direction to complete the horizontal permeability test process by obtaining the P1 horizontal differential pressure gauge, the P2 horizontal differential pressure gauge, and the P3 horizontal differential pressure gauge;
• (12) in a vertical permeability test process, after the horizontal permeability test process is completed, closing relevant gate valves to all the horizontal differential pressure gauges and opening the gate valves to all the vertical differential pressure gauges, starting the water injection pump to inject the methane water from the cooling water/saturated methane water tank through the bubbler into the hydrate reservoir horizontal/vertical permeability measuring apparatus at the same constant speed as in the horizontal permeability test process until a second flow rate through the gas tank with the balance scale remains constant;
• checking the gas flow meter to ensure that the hydrate sample is not decomposed, and obtaining a change in different differential pressures of the hydrate sample in a vertical direction by obtaining the P4 vertical differential pressure gauge, the P5 vertical differential pressure gauge and the P6 vertical differential pressure gauge;
• (13) recording relevant data of the hydrate formation process and the horizontal and vertical permeability test processes with a data acquisition instrument;
• and
• (14) processing the relevant data based on Darcy's Law to obtain a change in the horizontal/vertical permeability.