Research on the flow properties of fracturing fluids through nozzles during the flowback process in oil wells

Optimizing flowback control through nozzle sizing is critical for preserving hydraulic fractures and maximizing post-fracturing production. This study develops a physics-based fluid-dynamics model integrating the energy-conservation and continuity equations with actual wellhead pipeline configurations to predict flowrate and velocity of fracturing fluid through nozzles during early flowback. Validated rigorously against field data from Well GLX, the model demonstrated exceptional accuracy, with a maximum error of only 2.2% between calculated and measured flowrates across multiple operational stages involving different nozzle sizes (e.g., 2 + 2 mm and 2 + 3 mm). Key quantified findings reveal: flowrate is predominantly governed by nozzle size (sensitivity ranking: nozzle size > wellhead pressure > fluid density > local resistance coefficient), while velocity is primarily driven by wellhead pressure. Finite element analysis visualized the abrupt pressure drop and velocity surge at the nozzle throat, consistent with Bernoulli's principle. Crucially, discrepancies between model predictions and field measurements serve as reliable indicators of nozzle erosion damage or formation permeability issues. This robustly validated model provides a practical tool for real-time nozzle condition diagnosis and flowback optimization in field operations, enhancing reservoir protection and production stability.