Drill bit hydraulic system for oil and gas boreholes

Abstract

We set out to improve the existing design of a polycrystalline diamond bit with a steel or matrix body with the purpose of creating a hydro-monitoring effect. The research object was the hydraulic system of a diamond bit with a near-bit jet pump. The near-bit ejector system was studied by a theoretical analysis of the operation of the bit hydraulic system by means of canonical dependencies and hypotheses. A hydraulic system for a polycrystalline diamond bit is proposed. This system includes a high-pressure jet pump, which enhances the hydro-monitoring effect at the bottomhole. The main hydraulic characteristics of the bit flushing system with a jet pump are as follows: at a drilling pump feed of 18.4 l/s and a drilling fluid density of 1180 kg/m3, the working coefficient of jet pump injection equals 0.34; the working nozzle diameter equals 10.3 mm; the mixing chamber is 11.9 mm, bit hydromonitor nozzles are 11.1 mm; the number of hydromonitor nozzles is 3; the velocity at the exit of hydromonitor nozzles is 85.0 m/s; the pressure drop at the bit is 15.7 MPa. The possibility of using the hydro-monitoring effect enhanced by a near-bit jet pump was substantiated, since the velocity at the exit from the hydro-monitoring nozzles is sufficient to destroy most rocks (sandstone, limestone, dolomites, rock salt, gypsum stone, basalt, marble, granite). The jet pump in the proposed design of a polycrystalline diamond bit creates an additional circulation circuit above the bottomhole, injects cuttings from the annular space and feeds them to the hydro-monitor nozzles. This enables a more efficient destruction of the bottomhole rock. The power of hydro-monitor jets is sufficient to improve drilling performance.