This paper presents a mathematical analysis of how incorrect estimates of initial reservoir pressure (pi) may affect rate-transient analysis (RTA) in ultralow-permeability reservoirs. Measured values of pi are rarely available, and the value estimated using alternative approaches, such as a diagnostic fracture injection test (DFIT), can be time-consuming and expensive and also may be inaccurate. In the complete paper, the authors examine what can and cannot be achieved with accuracy when reliable estimates of pi are not available.
Introduction
RTA and production forecasting using historical production data require flow-regime identification for model parameter calculation. The task of flow-regime identification is best achieved under constant-rate flowing conditions.
