Shale applications challenge drilling performance
Drilling 6 ¾-in curve and lateral sections in Louisiana's Haynesville shale, an operator was experiencing bit balling and nozzle plugging, resulting in bits being prematurely pulled. The operator also had to deal with other difficulties commonly associated with shale play applications: Drilling is generally conducted using low-power rigs and relatively high mud weights of 16 ppg. These factors produce a poor hydraulic environment with low flow rates. Adding to this is an inadequate hydraulic horsepower (HSI) of 0.3 to 0.8 at the bit, which impairs cuttings evacuation, which results in bit balling, poor toolface control, and low ROP.
Next-generation PDC bit for shale applications
To eliminate the nozzle plugging and bit balling the operator was encountering drilling the Haynesville shale. Smith Bits recommended their next-generation Spear PDC bit: It is based on the first generation Spear bit, which was characterized by its distinctive bullet-shaped steel body and significantly reduced bit balling and cuttings packing around bit blades.
The next-generation Spear PDC bit design, developed using IDEAS integrated drillbit design platform, features increased capabilities through design enhancements: Taller blades give it an increased junk-slot that promotes cuttings migration from the bit face. A shale evacuation channel around nozzle ports and an improved hydraulic configuration directs cuttings evacuation to inhibit nozzle plugging. And, a reduced bit body profile improves cuttings evacuation into the annulus.