Novel, Integrated and Revolutionary Well Test Interpretation and Analysis

Abstract

Well test interpretation is an important tool for reservoir characterization. There exist four methods to achieve this goal, which are as follows: type-curve matching, conventional straight-line method, non-linear regression analysis, and TDS technique. The first method is basically a trial-and-error procedure; a deviation of a millimeter involves differences up to 200 psi and the difficulty of having so many matching charts. The second one, although very important, requires a plot for every flow regime, and there is no way for verification of the calculated parameters, and the third one has a problem of diversity of solutions but is the most used by engineers since it is automatically made by a computer program. This book focuses on the fourth method that uses a single plot of the pressure and pressure derivative plot for identifying different lines and feature for parameter estimation. It can be used alone and is applied practically to all the existing flow regime cases. In several cases, the same parameter can be estimated from different sources making a good way for verification. Combination of this method along with the second and third is recommended and widely used by the author. TDS technique is quite versatile. The user finds the different flow regimes and, then, draws a line through it. From an arbitrary point on each flow regime, a given parameter can be calculated. Besides, the intersection point between the extrapolated flow regimes, although do not have a physical meaning, is excellent to find another reservoir parameter or the verification of others. For instance, well-drainage area can be readily estimated from the intersect point formed between the radial flow regime and the late pseudosteady state period. Every time someone starts working using TDS technique, he or she never stops. The reader is invited to give it a try.