Insights of Abrasive Water Jet Slotting on Enhancing Efficiency of Hydraulic Fracturing

Abrasive water jet (AWJ) slotting is an improved perforation method based on the AWJ perforation. The perforation shape of AWJ slotting and the mechanisms of AWJ slotting effect on fracturing are not thoroughly comprehended. In this study, the perforation experiments and the fracturing experiments under AWJ slotting and AWJ perforation without casing and cement were conducted. The hole shape resulting from AWJ slotting resembles a sword, with an approximately grooved cross-section. The length of the groove is directly proportional with the jet’s travel distance, whereas the width of the groove is approximately 5.8 times the nozzle diameter. Under the same jet rate and jet time, the hole depth of AWJ slotting is 2.4 times that of AWJ perforation, and the hole volume of AWJ slotting is 7.0 times that of AWJ perforation. These differences result from to the expansion of fluid flow channel and the wall area by the moving jet. Compared with the traditional perforation method, the shape of AWJ slotting can facilitate multi-fracture initiation along the direction of slotting. Consequently, hydraulic fracturing under AWJ slotting exhibits lower fracturing difficulty and larger fracture scale compared to that under AWJ perforation. At the same hole depth, the peak fracturing pressure of AWJ slotting is 77.2% of that of AWJ perforation and the fracture area is 1.3 larger than times that of the AWJ perforation. On the basis of the original hydra-jet fracturing tools, a torsional device is added to realize the AWJ slotting along the normal plane. The implementation of AWJ slotting is anticipated to improve the efficiency and quality of hydraulic fracturing.