Direct and inverse problems of gas emission and the sorptive deformation of coal beds

L. A. Nazarova, L. A. Nazarov, M. Vandamme, J. M. Pereira

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1 Citation (Scopus)

Abstract

Using the equations of state for fractured-porous media that describe the sorptioninduced deformation of coal, we develop a geomechanical model for radial gas influx to a borehole drilled in a coal bed with the concurrent evolution of stress field in the borehole environment. A numerical-and-analytical method is proposed for solving the corresponding system of equations for poroelastic media. A relation is found between the volume of slack withdrawn in the borehole (when opening up the gas-bearing seams), the sorption-and-storage capacities of coal, the permeability k, and the horizontal component σh of the natural stress field. We demonstrate the solvability of the inverse boundary-coefficient problem of determining k and σh on the basis of pressure in the closed borehole. We substantiate an express-method for estimating the permeability by the measurements of pressure in the borehole operating in the “pressure drop” mode.

Original languageEnglish
Pages (from-to)236-243
Number of pages8
JournalJournal of Applied and Industrial Mathematics
Volume11
Issue number2
DOIs
Publication statusPublished - 1 Apr 2017

Keywords

  • borehole
  • coal bed
  • filtration
  • fracture-porousmedium
  • inverse problem
  • natural stress
  • permeability

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