CBM Well Test Analysis Method

With the rapid development of the world economy, the conventional energy already can’tmeet its needs, coalbed methane as a kind of new eiffcient and cleaner energy, has largeadvantages in the development and application.So it is taken more and more attention.Then,there has a practical signiifcance to study coalbed methane well test.Lots of expeirmentresearch shows that, stress sensitivity was existed in the coal reservoir,which has a significanteffect on production of coalbed methane. Previous CBM well test analysis method littleaccount of the inlfuence of strata pressure sensitive. This paper focuses on the well testmodel of coal reservoir consideirng stress sensitivity.In this thesis, based on the literature research, the reservoir capabilities，migration andproduction mechanisms of coalbed methane are analyzed first, the unsteady state sorptionmodeland the pseudo-steady state sorption model of single-phase lfow for CBM areestablished. The Langmuir adsorption isotherm law and Fick’s law are introduced to descirbethe CBM desorption and diffusion behavior in these models. Then, And then in theestablishment of stress sensitivity of the consideration of well test model, solving process toreplace Langmuir Absorbing Formula with imitative gas pressure that has led to the equationwith satisfied imitative pressure in the CBM strata. Analysis is also made on vairablecoefficients of permeability and the changing law of pressure with changes of parameters indouble media. This paper also application deconvolution in analyze variable lfow of CBMwell test model. All these results have provided both the theory basis and new model for pilotwells to develop CBM resources.