Influence of pumping flowrate fluctuation on penetration shape during hydra-jet perforation

Flow-rate fluctuation cannot be avoided for high pressure pump group on surface during fracturing pumping. The hydra-jet perforation string moves along wellbore axis with the flow-rate fluctuation, which causes the penetration shape is not a circle, but an ellipse with major axis in wellbore direction. In the paper, an evaluation model for hydra-jet perforation shape was built based on the linear elasticity deformation and abrasive jet cutting theory. In order to judge whether the casing is penetrated, we proposed the compute scheme of the jet coordinates at each time and cutting depth. Assuming the pumping flowrate is of uniform statistical distribution within fluctuation region, the results show that the major axis of ellipse hole is proportional to the range of pumping fluctuation in vertical wells. If pumping flow-rate fluctuation is below ±0.04 m3/min, the ratio of major axis to minor axis of the ellipse hole would be less than 2.0, which can satisfy the pin-point perforation. Therefore, the paper recommends the flow-rate fluctuation needs to be controlled in the range of ±0.04 m3/min.