Dynamic Simulation Of Self-reformation Of Fracturing Wells In Coalbed Methane Reservoirs

Flow of coal gas in the reservoir is subject to self-transformation effect, matrix desorption and diffusion. The practical development of coalbed gas reservoir shows that the effect of self-transformation effect on the production of gas well (especially fractured gas well) is great. So, it is necessary to study the effect of self-transformation and its effect on the yield.The self-transformation effect of fractured wells in coalbed methane reservoirs is studied by numerical simulation, and the main results are as follows:(1) The effect of the self-transformation is that in the early stage, the effective stress is dominant, as it increases, the permeability of the reservoir decreases, leading to the decline of production, In the middle and late stage, the matrix shrinkage is in the leading position, while matrix shrinks, the permeability of the matrix increases, then the gas well production increases.(2) A permeability model considering effective stress, matrix shrinkage and Klinkenberg effect is built.(3) Build a three-dimensional, dual porosity, gas-water two-phase productivity model of coalbed reservoir, the model consider adsorption, diffusion, Self-transformation effect and other physical process and taking the artificial fracture into account, the IMPES method is employed to solve this model.(4) A dynamic simulation software based on Visual Basic 6.0 Chinese version is developed to solve the model, which provides a favorable tool for the study of the self-transformation effect and the development of the prediction of gas pressure in coal seam.(5) Based on the analysis of the calculation results, the influence of the Young's modulus? Initial micro fracture compression coefficient?Langmuir strain constant?Langmuir pressure? Slippage coefficient and Poisson ratio on permeability of coalbed methane is studied.(6) Based on the analysis of the calculation results, the influence of the self-transformationeffect on the productivity of coalbed methane fractured wells under different Young's modulus?Langmuir pressure?Langmuir volume?Initial micro fracture permeability? Initial micro fracture porosity?Bottom hole flow pressure?Fracture length and flow conductivity is studied.