A new mathematical workflow to predict permeability variation using flowing gas material balance

In the dynamic approach, production data including the flowing wellhead or bottomhole pressures are used to conduct the material balance analysis to determine the gas in place at any time during the life of well. However, the procedure did not extend to identify the well health issues such as permeability variation. The objective of this research is to develop a simplified mathematical workflow to identify and verify permeability variation using flowing gas material balance. In this approach, a new form of flowing gas material balance equation is derived by adding permeability variation term. In this new mathematical workflow, linear and exponential curve fitting tools along with the flowing material balance analysis are used to predict well expected behavior. The prediction is then compared with initial well production behavior. The deviation of the prediction and the expected production behavior formed the basis of permeability variation. The component of the model is tested with known data and then the total model is verified with known values. After that, the workflow is applied in the gas well. The new model prediction is validated using field data and the prediction compares quite well. The well health diagnostics are successfully compared with known well issues from an active gas field. Results presented in this paper will show that the novel workflow is able to accurately predict permeability variations in both constant and variable production rates. In addition, the new workflow enables the production engineers to send an alarm to take corrective measure about the issue and to diagnose production issues like permeability variation.