A method for analyzing transient flow-after-flow (FAF) deliverability test data from both gas and oil wells is presented. The paper describes the derivation and application of this method to several field and synthetic cases. The method solves the transient absolute open flow potential (AOFP) and average reservoir pressure () by evaluating the parameters of the Forchheimer (a and b) and the empirical backpressure (C and n) equations together with . Consequently, this new method allows one to describe the stabilized deliverability equation from transient test data, given reasonable estimates of the reservoir drainage area and shape. This approach is a significant improvement over currently available methods, which require an independent, a priori knowledge of for establishing a well's AOFP, along with the need to conduct a stabilized flow segment of the test.
All the resulting formulations are flexible enough to handle the pressure, pressure-squared, and pseudopressure approach for gas wells. This methodology is not restricted to gas wells as oil wells also lend themselves to the proposed analysis procedures. For oil wells, we used the pressure approach for single-phase flow and the pressure-squared approach for two-phase flow.
In the proposed technique, a well's orientation is unimportant. For example, a horizontal well's deliverability may also be characterized using the new method. In addition, layered reservoirs may be analyzed with the proposed technique. We also show that this method can be extended to injection wells.
Synthetic data were initially used to verify the method. Field data from several gas and oil wells, including a horizontal well and gas injector, were then used to demonstrate the method's application. In all cases, the new method shows good agreement with the results obtained from conventional methods, both in terms of AOFP and .