Hydraulics can significantly affect Polycrystalline Diamond Compact (PDC) bit performance in applications where cuttings volume, formation types, and rig pressure limitations lead to poor fluid dynamics that compromise cleaning and cooling, and result in lower ROP and higher bit wear. A key mitigation challenge is improving cleaning efficiency without experiencing a significant pressure drop across the bit. This paper studies hydraulic conditions affecting PDC bit performance, examines modeling and design steps to develop a curved nozzle design, and presents the nozzle's performance in the field.
Research including computational fluid dynamics (CFD) modeling was conducted to better understand flow and velocity across the bit face. The resulting curved nozzle geometry was complex and required multiple iterations to achieve the desired effect. The nozzle design was applied in the field and its performance was compared to similar PDC bits with standard nozzles.
The curved nozzle design redirects fluid flow and reduces distance from the nozzle outlet to cutting face while retaining the same total flow area (TFA). The change in flow characteristics increases fluid impact on the formation and velocity in the waterways to enhance cleaning efficiency and cooling. The carbide nozzles were manufactured and installed on standard PDC bits used in a series of Permian Basin vertical and lateral wells in the United States. Vertical applications in Canada's Viewfield field were also studied. Bits fitted with the curved nozzles demonstrated significant performance gains compared to bits with conventional nozzles. Field reports show higher ROP and less bit wear in formations where interbedded clays and reactive shales present hydraulic challenges.
The insights gained into PDC bit hydraulics and the performance of the resulting curved nozzle design has enhanced the ability to mitigate many common hydraulics-related cleaning and cooling challenges.