Hydra jet fracturing is an effective stimulation method for unconventional reservoir exploitations. Fracturing fluid migration in annular influences behaviors of multi-cluster fractures initiation and extension. To investigate the fluid transportation in annular, a model was adopted to figure out the flow filed feature around water-jet and the relationship between fluid migration and some key parameters, i.e. annular velocity, jet velocity, fracture extend pressure difference (FEPD) and annular outlet pressure. It demonstrated that flow field variation in annular primarily located around jets. Static pressure in jet-core was higher and pressure-drop zone exists around jets. A point-sink-like flow existed around jets. Simultaneously, the flow field distributed heterogeneously. There was no interference among clusters. In the same situation, maximum flow rate difference between clusters was merely 0.08 kg/s, the variation of referenced cluster flow rate was just 0.05 kg/s, the FEPD among clusters was 4 MPa, and clusters’ flow rate changed according to a uniform law as fracture extend pressure changes. A positive relationship existed between clusters’ flow rate and nozzle velocity or annular outlet pressure, while annular velocity had no impact. All parameters mentioned above had no influence on flow rate difference. FEPD among clusters was a domain parameter of difference of clusters’ flow rate. Flow rate in each cluster increased linearly with FEPD deducing. In addition, the flow rate difference possessed a positive linear trend with FEPD. Utilization of fluid would reach to 100%, when annular velocity was less than 3 m/s or annular outlet pressure surpass 40 MPa in this study. This research may function as a reference in hydra-jet fracturing design.
Key words：
multi-cluster fracturing; water jet; annular flow field; fracturing fluid migration; interference between clusters
