Field Results Verify Afterflow Analysis From D.S.T. And Short-Time Production Test

The McKinley afterflow method has been successfully used to interpret drill-stem tests (D.S.T.) and short-time production tests where conventional analysis methods cannot be employed, or are difficult to apply." Although the afterflow method has other applications, this study will be limited to pressure buildup behavior. Throughout this paper the McKinley afterflow buildup method will be referred to as simply the afterflow method. The Horner method is the most commonly used technique for interpreting short-time test data, so the following examples will be compared to this method.2 Effective permeability, wellbore damage or stimulation, radius of investigation, and expected production rate are the reservoir parameters obtainable by the afterflow method. Exact numerical values are not obtained by this or any curve-matching procedure, but the order of magnitude of the answers is sufficiently close to help make decisions that are normally made from a short-time test. Six examples have been selected to illustrate the application of the afterflow method. These examples are typical of many tests analyzed from producing areas around the world. They hav,e been selected because of the large amount of followup data made available by Henry Engineering and other industry companies. Reference 1 describes the analytical treatment of the afterflow method. Utilization of the afterflow method to D.S.T. and short-time production tests has previously been described by Milner and Warren in S.P.E. number 4123. Our contribution through this study is to present verification, by actual field results, of the afterflow method to certain types of problems.