T he value of coal seam water effective permeability is obviously a criticalparameter when evaluating the productivity of a coal seam. In dewatering process,further development plan, a suitable type of pump is needed which is commensuratewith the productivity level of coal seam. The objective of this paper is to estimates the reservoir permeability that are obtained from the analysis of single well pressuretransient test using Ecrin Software. . Injection Fall-off test is conducted in X and Ywells which are a CBM exploration well located in Muara Enim field in SumateraSelatan Province.Well X is a CBM well with depth of 2077ft net pay formation of 20.9ft.Pressure observed responses showed that well X has a Double Porosity slab type ofreservoir with infinite boundary. Reservoir characteristic that also been determinedare wellbore storage coefficient of 4.01x10-5permeability measured of 2.15mD,skin factor scaled of -5.37, initial pressure reservoir gauged of 1003.33psi, lambdaof 3.42x10-4, omega of 3.49x10-5.Well Y is a CBM well with depth of 2300ft, net pay formation of 18.44ft.Pressure observed responses showed that well Y has a dual porosity slab type ofreservoir with one fault boundaries with reservoir characteristic such aspermeability measured of 1.53mD, skin factor scaled of -5.08, initial pressurereservoir gauged of 1010psia, lambda of 5.74x10-5, omega of 0.945 , and distancebetween well to fault lengthened of 97.1ft. with constant pressure boundary.