Device for simulating reasonable drainage speed in single-phase flow stage during vertical-well coalbed methane drainage

Abstract

A device for simulating a reasonable drainage speed in a single-phase flow stage during vertical-well coalbed methane drainage comprises a coal sample clamping system, a formation pressure simulatingsystem, a liquid supply system, a drainage control simulating system for simulating pressure drop in the drainage process and testing the liquid production, a fluid pressure propagation simulating system and an information acquisition and analysis and control system, wherein the coal sample clamping system is connected with the formation pressure simulating system, the liquid supply system, the drainage control simulating system and the fluid pressure propagation simulating system through pipes respectively; the formation pressure simulating system, the liquid supply system, the drainage control simulating system and the fluid pressure propagation simulating system are connected with the information acquisition and analysis and control system through data lines respectively. The device canevaluate and stimulate the permeability of different coal reservoirs and the reasonability of the drainage processes in different stress states to obtain a reasonable drainage working system in the single-phase flow stage under different coal reservoir conditions, and can improve the vertical-well coalbed methane drainage efficiency and increase the gas production thereof to the maximum extent.

Description

technical field [0001] The invention belongs to the technical field of coal bed gas extraction and relates to a reasonable extraction speed simulation device for coal bed gas vertical well single-phase flow stage. Background technique [0002] Surface coalbed methane wells are mainly produced by desorbing coalbed methane through "drainage-depressurization". During vertical well drainage of coalbed methane, with the production of water in the coal reservoir, the effective stress on the coal matrix increases, resulting in the narrowing and even partial closure of the cracks in the coal seam. The macroscopic manifestation is the decrease of the permeability of the coal seam. With the development of drainage, the water pressure continues to spread from near the wellbore to far away, forming a certain pressure gradient. The drainage during the period before the gas desorption pressure is reached is called the single-phase water flow stage. [0003] During single-phase flow stag...

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Problems solved by technology

Coal reservoir pressure, critical desorption pressure, coal reservoir permeability, coal seam stress, coal seam water content, coal rock mechanical properties, etc. all have an impact on the change of permeability in the process of coalbed methane well drainage. When these conditions change , will have an impact on the water pressure transmission distance in the single-phase flow stage. What kind of drainage rate is reasonable for the vertical coalbed methane well in the single-phase flow stage? At present, the field is more based on the combination of theoretical analysis and experience. Drainage is scientifically limited, and it is impossible to evaluate and simulate the rationality of the drainage process under different coal reservoir permeability and different stress states, and it is impossible to obtain a reasonable drainage working system for the single-phase flow stage under different coal reservoir conditions. Unable to maximize the drainage efficiency and gas production of coalbed methane vertical wells

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