Advancing hard/harsh rock drill bits: A new bit design improves ROP and reduces tripping

摘要

A significant challenge for oil and gas operating companies worldwide is to maximize drill bit run intervals within interbedded, hard-to-drill rock sections. In these more challenging applications, polycrystalline diamond compact (PDC) and roller cone insert designs are pushed to their limits and often fail due to PDC thermal fatigue, severe abrasion, bearing failures, or impact damage. This translates into additional trips for replacing bit types or cleaning the hole from junk left in the hole, representing significant added costs. An additional cost that operators incur is represented by the utilization of multiple bits to finish these intervals when a single diamond-impregnated bit can complete the interval using a mud motor or a turbine. Standard mud motors have a maximum circulating life of 250 to 300 hours depending on temperatures, fluid type in the string, and a variety of other downhole environmental variables. When a challenging zone is encountered that results in the need for a high-speed drive technology, high-speed mud motors or turbines are often used with impregnated-diamond bits to complete these intervals. Tool selection criteria will consider longevity, torque capability, and temperature tolerance, amongst other variables. From the directional drilling aspect, traditionally only mud motors were used, but currently both motors and turbines are used to steer the well toward the objective.