CBM production optimisation can be performed by optimising drilling, fracturing treatment, well completion and pumping operation. Coalbed methane (CBM) well production has always been sensitive to changes in pumping operation. In a large number of cases, despite the reservoir parameters being favourable to high and sustainable production, CBM production declines dramatically due to improper pumping operation.
The most commonly used completion method for vertical CBM wells is fracture treatment. Successful fracture treatment can result in high peak production. However, the fracture may close and production declines abruptly if the bottom hole pressure cannot be controlled at a reasonable level. In order to optimise the pumping operation, it is necessary to analyse how changes in permeability affect production. Adsorbed gas saturation is relevant to the change in permeability during production.
This study uses actual cases from the Bowen Basin and the Surat Basin in Australia; Ordos Basin in China, and coalbed methane blocks in Russia to analyse the relationship between gas saturation, mechanic properties of coal and gas saturation, and conductivity of fracture. Petroleum engineers are often confronted with the difficulty of the recovery of production wells that have been damaged by improper operation in the past. This study exhibits actual cases that have been recovered by optimised pumping operation.
This study provides useful engineering methodologies in diagnosing well behaviours by cases study. Inflow Performance Relation (IPR) can be used to analyse the efficiency of the drainage of CBM well.