Publications

The petroleum industry has been using different types of well testing procedures and technologies in coal bed methane (CBM, also known as Coal Seam Gas (CSG)) wells for many years: for instance –Injection/Falloff (IFO), Drill Stem Test (DST), and Wireline Formation Test (WFT). Evaluation of formation pressure, permeability and skin factor is as important in a CBM reservoir as in any other conventional reservoir for production and economic forecasting. Well testing represents a significant part of the total well cost, especially in Australia. In certain cases, the WFT approach has proven to be a means of reducing costs and saving rig time because it requires less time than DST. The main objective of this paper is to review the conventional pressure transient analysis that is used to interpret WFT and DST build-up transients in the CBM environment. Examples of DST tests from Australia involving partial tubing fill-up followed by shut-in, and of WFT tests, have been evaluated and compared. The paper also discusses some of the abnormal trends in the pressure derivative of the WFT, which can be explained from a CBM geological point of view.