The drilling practices of oil and gas wells prove that reducing the bottom-hole differential pressure (BHDP) can significantly improve the rate of penetration (ROP) that reduces the drilling cost. This paper summarizes the structure features, depressurization capacities, and the current researches and developments of equivalent circulation density (ECD) reduction tool, vortex joint and vortex bit based on the analysis of the depressurization theory of the vortex tools. Using field tests and flow field numerical calculation methods, the key factors which affect depressurization capacity of the vortex tools are analyzed. The reasonable axial angle, radial angle, reverse flow ratio, rotation speed, and distance between reverse nozzle outlet and the bottom-hole surface of the vortex bit are analyzed emphatically. The vortex and jet pump combination bit can reduce the BHDP about 0.8 MPa that is about 3 times of the vortex bit, which shows that the fluid vortex and jet pump combination depressurization method is feasible to reduce the BHDP. The results provide the theoretical guide for the development of the vortex tools.
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