Abstract
As an unconventional energy, coalbed methane (CBM) mainly exists in coal bed with adsorption, whose productivity is different from conventional gas reservoir. This paper explains the wellbore pressure drop, surface pipeline network simulation, and reservoir calculation model of CBM. A coupled surface/wellbore/reservoir calculation architecture was presented, to coordinate the gas production in each calculation period until the balance of surface/wellbore/reservoir. This coupled calculation method was applied to a CBM field for predicting production. The daily gas production increased year by year at the first time and then decreased gradually after several years, while the daily water production was reduced all the time with the successive decline of the formation pressure. The production of gas and water in each well is almost the same when the structure is a star. When system structure is a dendritic surface system, the daily gas production ranked highest at the well which is the nearest to the surface system collection point and lowest at the well which is the farthest to the surface system collection point. This coupled calculation method could be used to predict the water production, gas production, and formation pressure of a CBM field during a period of time.
Highlights
coalbed methane (CBM) is one of the most important sustainable energy for the strategy of sustainable development in the 21st century
Dempsey et al [2] first studied the coupling of gas reservoir flow simulation and surface system simulation, which built the foundation of other relative research on the production system integration
Combined with material balance method for isothermal adsorption of coalbed methane, this paper proposes a method to meet the need of unconventional coalbed methane integrated simulation coupling CBM considering network model, wellbore pressure drop, CBM adsorbed state, and its drainage gas recovery mechanism
Summary
CBM is one of the most important sustainable energy for the strategy of sustainable development in the 21st century. Guyaguler et al [8] proposed a similar approach, but in this method each subdomain needs to be solved repeatedly before reaching equilibrium, and when the final equilibrium is reached the IPR curve that can reflect the condition of near-well reservoir is obtained. This method is time-consuming and the amount of calculation is large, it can reduce the balance error. Combined with material balance method for isothermal adsorption of coalbed methane, this paper proposes a method to meet the need of unconventional coalbed methane integrated simulation coupling CBM considering network model, wellbore pressure drop, CBM adsorbed state, and its drainage gas recovery mechanism
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