Methodological and Theory

Calculation method of critical desorption pressure in undersaturated CBM reservoirs

  • Si ZHANG ,
  • Xiaolong PENG
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  • State key laboratory of oil and gas reservoir geology and exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China

Received date: 2021-11-02

  Online published: 2022-09-02

Abstract

In order to investigate the physical meaning of critical desorption pressure in undersaturated CBM(coalbed methane) reservoirs, the traditional critical desorption pressure calculation method and the liquid phase adsorption theory commonly used in field are introduced based on the status of the reserves of CBM, and the origin of the “undersaturated” phenomenon under the premise of gas phase wet is discussed. On the basis of the modified gas phase adsorption, the relationship between the critical desorption pressure and the capillary pressure in matrix pores is explained, and a new calculation method of critical desorption pressure is obtained. By comparing the advantages and disadvantages of the four methods in error analysis, theoretical completeness and operability, it is considered that the new calculation method proposed is relatively complete in theory, has strong operability and is easy to calculate, and obtains a reasonable result in an example. It can be concluded that CBM adsorption equilibrium and critical desorption phenomenon can be interpreted as the result of the interaction between reservoir pressure and capillary pressure under the premise of coalbed gas phase wetting. The improved gas phase adsorption theory and the new calculation method of critical desorption pressure are worth the further study.

Cite this article

Si ZHANG , Xiaolong PENG . Calculation method of critical desorption pressure in undersaturated CBM reservoirs[J]. Petroleum Reservoir Evaluation and Development, 2022 , 12(4) : 589 -595 . DOI: 10.13809/j.cnki.cn32-1825/te.2022.04.006

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