Investigation on the effect of process parameters and rock breaking mechanisms on swirling impeller abrasive water jet breaking carbonate rock

Radial swirling impeller abrasive water jet drilling technology is a potential cost-effective way to develop carbonate reservoirs. Swirling impeller abrasive water jet carbonate rock breaking experiments are utilized to study the feasibility of drilling radial branches in carbonate reservoirs. Besides, the influence low of process parameters and optimal process parameter combination on the swirling impeller abrasive water jet carbonate rock breaking performances are studied and illustrated. Finally, the carbonate rock breaking mechanisms of swirling impeller abrasive water jet are discussed and revealed. The results of this study showed that the swirling impeller abrasive water jet could create a regular smooth circular hole with a conical bulge at the hole bottom. The cross-section of the swirling impeller abrasive water jet drilled hole presented a “W”-shape. The jet drilled hole diameter was greater than the maximum outside diameter of the jetting pipe string and the conical bulge at the hole bottom could be eroded by the subsequent jet, which proofed that it was feasible for the swirling impeller abrasive water jet to drill radial branches in carbonate reservoirs. The jet drilled hole diameter increased with the increase in the jetting pressure, the standoffdistance and the exposure time. And, it increased firstly and then decreased with the increase in the abrasive mass concentration. The jet drilled hole depth and hole volume increased with the increase in the jetting pressure and the exposure time, and with a decrease in the standoff distance. And, they increased firstly and then decreased with the increase in the abrasive mass concentration. The optimal process parameter combination under our experimental conditions was the jetting pressure, standoffdistance, abrasive mass concentration and exposure time were the 30 MPa, 0, 9.0%~10% and 60 s respectively. In the process of swirling impeller abrasive water jet carbonate rock breaking, the swirling impeller abrasive water jet not only through the tension force that was created by the high angle abrasive particle impact, but also through the shear force that was created by the low angle abrasive particle impact to break the carbonate rock. Since the tensile strength and shear strength of carbonate rock material was far small than the compressive strength, the swirling impeller abrasive water jet possessed a high rock breaking ability and efficiency on carbonate rock. The research results were expected to provide a theoretical basis and experimental foundation for utilizing the swirling impeller abrasive water jet to drilling radial branches in carbonate reservoirs.