The Study Of Coal Bed Methane Seepage Rule In Hypotonic Reservoir Considering Slippage Effects

In summarize the predecessor some findings foundation, this thesis used theory of migration of coal-bed methane, solid mechanics, pore media theory, seepage mechanics, poly-phase seepage and finite element numerical simulation and so on, studied the rule of gas migration in hypotonic reservoir considering slippage effects, completed the following research work:1. According to the hypotonic reservoir characteristic, carried on the reasonable essential mechanics supposition, and based on this, established the mathematical model of coal-bed methane migration in hypotonic reservoir considering slippage effects, established the mathematical model considering coupling of gas and water and gas slippage effects that the material effect gas water two seepage stage in hypotonic reservoir, through simplification established the single-phase gas seepage mathematical model influence by slippage effects in hypotonic reservoir.2. Used the single-phase gas seepage mathematical model influence by slippage effects carried on the theory analysis, obtained the steady-flow pore pressure distribution analysis formula in the finite coal bed; gamma infinity hypotonic coal bed non-steady flow pore pressure distribution analysis formula influence by slippage effects; gas output prediction formula in gamma infinity hypotonic coal bed considered by gas slippage effects; spheric non-steady flow pore pressure distribution analysis formula with the slippage effects as well as the spheric non-steady flow gas output prediction formula in gamma infinity hypotonic reservoir.3. Used the experiment method carried on the experiment that gas migration in hypotonic reservoir considered gas slippage effects and the gas slippage effects experiment in hypotonic reservoir with different water degree of saturation, obtained the new gas slippage effects fitting formula and explained various coefficients physics significance in the formula; obtained the relation between the slippage factor and the absolute permeability; explained the water degree of saturation, the pore pressure and the environment pressure dynamic effected to the reservoir effective permeability; proved under the low permeability environment, the pore pressure of gas slippage effects existence had the high threshold value.4. Developed the single-phase gas nonlinear seepage and the gas-water two phase gas nonlinear seepage finite element simulators influence by gas slippage effects.5. Used the field engineering wells data and delivery dynamic data of liulin coal-bed methane experiment block in shanxi hedong coal field, analyzed the variation rule of pore pressure in hypotonic reservoir considering the slippage effects and different mining condition, the variation rule of gas current velocity, the prediction rule of gas output and the change rule of gas-water two degrees of saturation.The result of numerical simulation indicated: gas slippage effects had the significant contribution to distribution of pore pressure, changing of gas current velocity, gas prediction output and changing of gas-water degree of saturation, mainly manifested in the gas slippage effects caused the pore pressure drop accelerate around of the mining wells, increased differential pressure between the hypotonic reservoir and the mining wells that is advantageous the coal-bed methane persistent desorption; slippage effects caused the gas speed to be higher than daxi seepage gas speed; it caused the prediction gas output more closer to the coal-bed methane historical fitting value; it also caused the gas phase degree of saturation of low seepage reservoir to achieve the saturated condition very quickly, and the water phase degree of saturation also rapid drop and stable along with the mining thorough, it was more advantageous to coal-bed methane recovery.The main innovation of this thesis lied, according to the hypotonic reservoir characteristic, established the mathematical model of coal-bed methane migration in hypotonic reservoir considering slippage effects; and based on this, established the mathematical model considering coupling of gas and water and gas slippage effects that the material effect gas water two seepage stage in hypotonic reservoir, established the single-phase gas seepage mathematical model influence by slippage effects in hypotonic reservoir; used the theoretical analysis method obtained pore pressure distribution analysis formula and the gas output prediction formula under the different flowing characteristic; used the experiment method obtained the coal-bed methane migration rule in hypotonic reservoir considered the slippage effects; explained the water degree of saturation, the pore pressure, the environment pressure to the reservoir effective permeability dynamic effect; explained the water degree of saturation, the pore pressure and the environment pressure dynamic effected to the reservoir effective permeability; proved under the low permeability environment, the pore pressure of gas slippage effects existence had the high threshold value; developed the single-phase gas nonlinear seepage and the gas-water two phase gas nonlinear seepage finite element simulators influence by gas slippage effects and used the numerical simulation method to systematic research these questions such as the pore pressure changing rule in hypotonic reservoir different mining condition, the gas variation current velocity rule, the gas prediction output rule and the gas-water two degrees of saturation change rule considering the slippage effects and so on.