A general approach for deliverability calculations of gas wells

This paper presents a general and a simplified method for deliverability calculations of gas wells, which among other advantages, eliminates the need for conventional multipoint tests. The analytical solution to the diffusivity equation for real gas flow under stabilized or pseudo-steady-state flow conditions and a wide range of rock and fluid properties are used to generate an empirical correlation for calculating gas well deliverability. The rock, fluid and system properties, used in developing previous correlations found in literature, were limited to reservoir pressure, reservoir temperature, gas specific gravity, reservoir permeability, wellbore radius, well drainage area, and shape factor. Additional key properties such as reservoir porosity, net formation thickness and skin factor are included in this work to develop a more general dimensionless Inflow Performance Relationship (IPR). It is found that the general correlation, developed is this study, presents the observed field data much closer than previous ones found in the literature. In addition, based on the larger data set, an empirical relation to predict future deliverability from current flow test data is also developed.The two modified and general relations developed in this work provide a simple procedure for gas deliverability calculations which greatly simplifies the conventional deliverability testing methods. The required data can be obtained from a buildup test, or a single-point flow test, instead of an elaborate multipoint flow test. Further, the broad range of practically all rock and fluid properties used in developing the modified dimensionless IPR curves should cover the majority of the field situations generally encountered. The use of the modified dimensionless IPR curves, the pseudopressure formulation and the sensitivity analysis indicate a generality of the approach presented in this paper, irrespective of the gas reservoir system under study.