Abstract

During the last few years, research has been done on generalized material balance equations for conventional oil and gas reservoirs in order to improve the reservoir performance analysis. However, those equations are inappropriate for coal seam gas (CSG) reservoirs. To address this limitation, a generalized material balance equation (GMBE) for CSG reservoirs was developed. This work is based on a mathematical development and the straight-line method, published previously and widespread used for conventional reservoirs.

Three validation examples of the proposed equation were designed. They show the new equation has the following advantages:

  1. it is applicable to CSG reservoirs in saturated, equilibrium, and undersaturated conditions,

  2. it is applicable to any type of coalbed without restriction on especial diffusion constant values,

  3. existent equations are particular cases of the generalized equation evaluated under certain restrictions, and

  4. its reorganization is analogous to the popular straight- line method for conventional reservoirs.

P. 621

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