The effects of the coupled reservoir and fluid properties, in addition to the geomechanical effects inthe reservoir, are studied on reservoir pressure and cumulative gas produced. The behavioral variationof reservoir pressure, rock properties, and fluid properties are, numerically, studied both spatially andtemporally. The coal formation, subjected to dewatering and subsequent phases, is analyzed. The study of single-phase water followed by the multiphase flow of gas and water, in the transient region, is carried out. Thedrained distance dynamically varies with time and expands away from the wellbore. The flow to the wellboreis either a single-phase flow or a combination of single and multiphase flow. The transition between phasesmodeled to maintain continuity between the flow phases. Cleat and fluid compressibility are varied withtime 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 multiphasenonlinear advective term affects the flow pattern, which was, initially, diffusive in single-phase. Pressure, atany point in the reservoir, is revised when the flow regime and phases altered. The cumulative gas producedat the end of each phase and the cleat permeability, due to coupled reservoir compaction and matrix shrinkageeffects, of the reservoir, in comparison with the original, is estimated. It can be observed, from the resultsof the study, that the flow pattern remains the same for a phase type with changing time. The flow patternchanges 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 theconstant, but varying, reservoir and fluid property that helps to understand the pressure distribution in thereservoir for every phase at each time step and especially at the transitional zones. The study is beneficialto the industry in analyzing the different fluid phase flow patterns and flow associated parameters, whichultimately, after single-phase gas flow, will give us an idea of the recovery factor of methane gas and thechange in reservoir petrophysical parameters from the original state. © 2020 Society of Petroleum Engineers. All rights reserved.