Well Performance Estimation from Brief Discharge Using Heuristic Decline Analysis

Abstract

Traditionally stable well outputs have been determined by extended discharge: flowing the well to waste for a period of weeks or months. This has become increasingly difficult because of environmental constraints, resulting in well testing requiring injection wells and pipelines in order to allow extended flow periods, and this means that tests cannot be carried out routinely in the exploration program.

Brief vertical or horizontal discharges to waste are still possible, and indeed a brief discharge is required to clear the well of debris. Data from a period of several hours of open flow has been used for a decline analysis. The analysis is an heuristic adaptation of flow at constant pressure. For wells which were reasonably well warmed up before discharge, such decline analysis has given acceptable estimates of ultimate stabilised flow, even though it involves extrapolation well beyond the accepted limit of validity. Examples from Mokai are used to illustrate the application of the method