EXACT TITLE OF PAPER: PRODUCTIVITY PREDICTION MODEL ESTABLISHMENT AND NUMERICAL SIMULATION OF COALBED METHANE WELLS

摘要

Coalbed methane is stored in coal seam at an adsorption state, desorption-diffusion-seepage are the three different physical processes when developed. The effect of matrix porosity-cleat-artificial fracture in coal reservoir on coalbed methane production process is analyzed in detail. The fracturing fractures are regarded as the extension of wellbores, because the percolating resistance of coalbed methane in fracturing fracture is very small. Reasonable physical model of coalbed methane flow is designed based on this. According to Fick's law, Langmuir adsorption equation and Darcy's law, the continuity equation of coalbed methane output was established by law of mass conservation. The numerical simulation software of coalbed methane vertical wells fracturing producing is compiled on the basis. The influence of different factors on the capacity, the formation and extension of pressure drop funnel is analyzed using the software. The influence of permeability, initial formation pressure, Langmuir adsorption capacity on production and formation pressure distribution is relatively significant. Coal seam thickness has an obvious impact on the output, whereas it has little relation with the formation and extension of pressure drop funnel. The software has functions of historical matching and prediction. By matching the coalbed methane well production based on field practical data, the future production can be predicted accurately, thus providing the basis for the implementation of coalbed methane well production measures.