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Abstract Diagnostic Fracture Injection Tests (DFITs) have become commonplace in low-permeability (unconventional) reservoirs to obtain parameters used in hydraulic fracture stimulation design and reservoir characterization. However, the time taken to acquire reliable estimates of these parameters may be excessive. As a result, pump-in/flowback tests, as opposed to the more conventional pump-in/shut-in tests, have been applied in the industry to accelerate the closure process and to estimate closure pressure, which is used in hydraulic fracture design. However, this comes at the expense of losing after-closure data, which is required to estimate reservoir pressure and flow properties. The goal of this paper is to accelerate the closure process during a DFIT, without sacrificing the after-closure data and derived parameters. The proposed DFIT procedure includes flowing back the fracturing fluid, after opening and propagation of the fracture, at a very low and constant rate. The flowback process is continued for a few hours after fracture closure. The well is then shut-in and the pressure falloff is monitored. The main purpose of the ultra-low rate flowback is to remove or reduce the afterflow caused by wellbore storage. The new DFIT procedure is applied to two field examples performed in a low-permeability reservoir in western Canada. The data are analyzed using well-established pressure-transient analysis methods. An estimate of closure pressure was obtained in less than two hours for both field examples, despite the low-permeability of the reservoir (several hundred nanodarcies). For one of the field examples, estimates of reservoir pressure and transmissibility were obtained after just 4 days of shut-in following the flowback process. Finally, a conceptual model is presented to analyze the conventional pump-in/flowback tests for determination of reservoir pressure. The conceptual model is validated against synthetic simulation results. Using this method, reservoir pressure is obtainable with just a few hours of flowback data. Highlights • A new DFIT procedure is presented and applied in the field. • A conceptual method is presented for estimation of reservoir pressure in pump-in/flowback tests. • The procedure and analysis method provide reliable estimates of in-situ stress and reservoir pressure in a short period. [ABSTRACT FROM AUTHOR]