Estimation of permeability from pump-in/flowback tests: An after-closure analysis approach

•Novel approach extends Soliman.•Craig model for after-closure analysis.•Innovative analysis technique addresses the gap in hydraulic fracturing testing.•The model detects flow regimes, estimates permeability, and reservoir pressure.•Simulations reveal a time advantage of flowback tests in permeability assessment. In this study, our primary objective is to introduce a novel approach for estimating permeability and reservoir pressure during the after-closure period of pump-in/flowback tests. While existing techniques primarily focus on Diagnostic Fracture Injection Tests (DFIT) for formation parameter estimation, no methods have been developed for analyzing the shut-in period following pump-in/flowback tests. We extend the after-closure analysis based on the Soliman and Craig model to make it applicable to pump-in/flowback tests. Our analysis involves studying after-closure data to calculate formation permeability and reservoir pressure. During the after-closure period, we introduce a model to identify the flow regime and estimate permeability, particularly during the pseudo-radial flow period. To validate our model, we compare its performance with conventional DFIT cases using a finite difference numerical simulator. Our simulations reveal a time advantage for pump-in/flowback tests over traditional DFIT in permeability estimation. This pioneering approach represents a significant advancement in the field, providing a unique and efficient method for estimating reservoir properties during radial flow in pump-in/flowback tests.