Reducing the bottom-hole differential pressure by vortex and hydraulic jet methods

Reducing the bottom-hole differential pressure (BHDP) of a gas/oil well and so as to reduce the "chip hold-down effect" can significantly improve the rate of penetration (ROP). The fluid vortex and hydraulic jet methods are used to reduce the BHDP while the wellbore pressure is unchangeable to prevent wellbore instability. The depressurization theories of the two hydraulic pressure drawdown methods are studied. The structures, depressurization mechanism, depressurization capacity, and the current researches and developments of the hydraulic pressure drawdown tools, including the vortex tools and the jet hydraulic pressure drawdown tools (JHPDTs), are analyzed. Using field tests and flow field numerical calculation methods, the key factors which affect depressurization capacity of the vortex tools and the JHPDTs, and the design principles of the vortex bit and the jet pump bit are proposed. Different depressurization methods and structures are simulated, which shows the vortex and jet pump combination bit with 106 mm distance is preferable.