Numerical modelling the stress dependent transitional fluid flow in coal bed methane reservoirs

The effects of the coupled reservoir and fluid properties, in addition to the geomechanical effects in the reservoir, are studied on reservoir pressure and cumulative gas produced. The behavioral variation of reservoir pressure, rock properties, and fluid properties are, numerically, studied both spatially and temporally. The coal formation, subjected to dewatering and subsequent phases, is analyzed. The study of singlephase water followed by the multiphase flow of gas and water, in the transient region, is carried out. The drained distance dynamically varies with time and expands away from the wellbore. The flow to the wellbore is either a single-phase flow or a combination of single and multiphase flow. The transition between phases modeled to maintain continuity between the flow phases. Cleat and fluid compressibility are varied with time to analyze their individual and coupled effect on flow parameters. The study details flow pattern at a time and how it changes when the time expands. The multiphase nonlinear advective term affects the flow pattern, which was, initially, diffusive in single-phase. Pressure, at any point in the reservoir, is revised when the flow regime and phases altered. The cumulative gas produced at the end of each phase and the cleat permeability, due to coupled reservoir compaction and matrix shrinkage effects, of the reservoir, in comparison with the original, is estimated. It can be observed, from the results of the study, that the flow pattern remains the same for a phase type with changing time. The flow pattern changes once the phase change from single to multiphase and vice versa. The study is novel from previous works because the cumulative production is not a function of the constant, but varying, reservoir and fluid property that helps to understand the pressure distribution in the reservoir for every phase at each time step and especially at the transitional zones. The study is beneficial to the industry in analyzing the different fluid phase flow patterns and flow associated parameters, which ultimately, after single-phase gas flow, will give us an idea of the recovery factor of methane gas and the change in reservoir petrophysical parameters from the original state.