Performance Predictions on Low Permeability Gas Wells

Abstract

Abstract Frequently it becomes necessary for the reservoir engineer to predict the stabilized deliverability of a gas well with a minimum predict the stabilized deliverability of a gas well with a minimum of test and production data. Usually this must be done with limited test data obtained by venting the gas to the atmosphere. The pipeline may not be available, since the purpose of the test and the production forecast may be to justify the installation of the pipeline. Although venting does not degrade the quality of the test, it does frequently reduce the quantity of test data obtained. Since sizeable expenditures for pipeline installation and development drilling, or conversely, the abandonment of a structure, may be influenced by the well's predicted performance, it is essential the most accurate prediction possible be made with the data available. However, when conditions permit, the more desirable test, a prolonged drawdown into the pipeline followed by a pressure buildup test, should be conducted. It will be shown that the typical short term one-point flow test taken on a well completed in a tight reservoir will indicate deliverabilities which are greatly exaggerated. Many wells in the Mid-Continent Area give indications of requiring several months to stabilize or reach simi-steady state flow conditions. A test of such duration is usually impractical. Frequently, time in addition to the cost preclude such a test. It, therefore, becomes necessary to obtain a reasonably accurate forecast in the absence of extensive field test data. It is the purpose of this paper to present a practical method of obtaining a reliable forecast.