Master of Science
Department or Program
The variation of in situ stresses and geomechanical characteristics of a coalbed reservoir play an important role in determining variation of permeability, and hence, its overall gas production. In contrast to conventional reservoirs, CBM is released in a non-linear fashion with major part of adsorbed gas released as pressure decreases. It has been well established that strength of coal decreases with pressure depletion. It is hypothesized that the Young’s modulus (E) of coal, which is an important mechanical property indicative of its strength, is sensitive to pressure depletion.
The basis of this study is to develop a correlation between variation of E and changes in effective horizontal stress. The relationship is established by utilizing the Shi and Durucan theoretical model for permeability. The results achieved by varying Young’s modulus show an improved modeling of in situ stresses with gas depletion. The trend is believed to improve prediction of permeability variation which, in turn, would improve prediction of the overall gas production.