Application of pressure and pressure integral functions for the analysis of well test data

Abstract

The analysis of well test data by methods which only use the pressure change can be ambiguous, and analysis using the derivative of the pressure change is often distorted by random error in the data or data noise. Although various "smoothing" techniques have been used to reduce data noise, some concern exists that smoothing procedures may alter the basic character of the data. In this work, we use pressure integral and pressure integral derivative functions to reduce the data noise. First, we perform the conventional semilog analysis on the well test data using the pressure integral functions. Then, we demonstrate the applicability of the pressure change integral and derivative of pressure change integral functions. In this manner we couple the integral functions with the pressure change and pressure change derivative functions to derive useful qualitative and quantitative information from these test data. We also analyze well test data with these methods without the use of superposition time functions such as, Horner time and Agarwal "effective time" functions. In addition, we introduce a numerical technique to generate the pressure integral functions. Thus, we integrate the pressure analysis approach with the pressure integral analysis approach and develop a consistent and applicable method for the analysis of well test data.