Abstract

Methane gas is adsorbed on the surface of coal matrix under hydrostatic pressure. On reduction of reservoir pressure (by dewatering) below the Critical Desorption Pressure, methane desorbs and migrates to the wellbore. However, presence of prospective coal seams alone does not warrant a well to be good CBM producer as adsorptive properties of coal leads to susceptibility from drilling mud, fracturing fluids and cement which might cause swelling and subsequent blockage. Apart from its Gas content and Gas Saturation, producibility from Coal largely dependent on the frequency and distribution of Cleats (i.e. extensive natural fracture system), cleats orientation and fracture induction in maximum stress direction. The aim of the study is to find out the prospective coal seams not only from resistivity, density and porosity parameter but also degree of fracture present in in-situ condition using Vp/Vs ratio and to characterise the fracture systems within the coal seams and to establish their relationship with the present day stress regime with a view to connect Cleats and to enhance as well as ensure sustainable flow of CBM to the well bore. Oriented perforation in maximum stress direction helps in generating enhanced permeability by increasing degree of fracture during Hydro-fracturing operations.