Abstract
Coalbed methane (CBM) and shale gas reservoirs are confirmed and a reservoir of natural gas dissolved in water of Mobara type has a possibility to include adsorbed gas. A combination of Langmuir isotherm and a dual porosity model successes for numerical reservoir simulation of CBM. However, the combination cannot work well for other natural gas reservoirs including adsorbed gas. This means that correct and simple gas retention and flow models have not been developed for reservoirs of shale gas and natural gas dissolved in water of Mobara type. This study shows common and different terms of petrophysical properties of reservoirs with adsorbed gas to understand characteristics of the reservoirs.
In addition, this study shows results of numerical simulations to estimate efficient geometries of horizontal wells and efficiency of mix injection of N2 and CO2 for enhanced coalbed methane recovery (ECBM) analysis using a reservoir simulator for CBM. Because other natural gas reservoirs including adsorbed gas have not established yet to make a proper numerical model, we cannot apply numerical simulations to reservoir conditions with large influence of desorption and flow of adsorbed gas. Also, we show that the amounts of adsorption of mudstones are relatively large. We need discuss the potential of mudstone as gas reservoirs but cap rocks.
