Fracturing Effectiveness Evaluation Based on Flowback Data Using Pressure Transient Testing

This study addresses fracturing performance evaluation during shale oil well flowback by developing a seepage flowback mathematical model and a water-phase evaluation framework. A method calculating effective fracture pore volume via flowback water production data is proposed. Using Well H flowback records, variable-production log-log well test plots and RNP-tm diagnostic charts were constructed for time-dependent fracturing effectiveness quantification. Key findings include: (1) Initial maximum cumulative water production derived from Arps harmonic decline model shows a semilogarithmic relationship between daily/cumulative water output; (2) Unit slope in fracturing fluid flowback indicates pseudosteady single-phase fracture depletion, while early positive slope deviation represents radial flow regime; (3) Complex fracture networks from stimulation reduce fluid seepage distances, transforming imbibition displacement into dominant mechanism and establishing fracture-dominated early flow imbibition-controlled sustained production progression. Field applications demonstrate the significance of flowback water production data in flow regime characterization and fracturing performance evaluation.