National Oilwell Varco’s 121?4-in. TC11 roller cone bit continues to set rate of penetration (ROP) records. The latest ReedHycalog TuffCutter design incorporates the proprietary Powder Forge process along with FullGage and TuffJacket features for 100% hardmetal coverage of the cones.

Pinedale performance

The typical 121?4-in. application in Wyoming’s Pinedale Anticline is 2,500 ft (762.5 m) through abrasive Wasatch sands. This includes drilling surface hole to the kickoff point, then building angle and drilling to the casing point.

The post-run analysis of the 9 7/8-in. DE713PUX Diamond Edge bit confirmed the durability of the cutting structure in the Haynesville shale. (Image courtesy of Varel)

Initial TC11 runs in the Pinedale Anticline demonstrated a 21% increase in ROP over the best competitor. Most recently, a TC11 bit delivered an average ROP of 337 ft/hr, an 80% increase over competitor offsets. This bit drilled 2,530 ft (771 m) and was dull graded 1-1-WT-A-E-I-FC-TD.

Improved forging

This most recent success of the TC11 is due to the improvements of the tooth hardmetal allowed by the patented powder forge process. The forging temperature is low enough not to degrade the tungsten carbide in the hardmetal matrix.

Traditional welded tooth hardmetal is subjected to temperatures well above the melting point of tungsten carbide, resulting in a dilution of the tungsten carbide mix in the applied hardmetal. TuffCutter hardmetal contains up to 75% tungsten carbide by volume compared to roughly 50% for conventional welded materials. More tungsten carbide equates to longer life at higher ROP.

Coupled with the FullGage feature and TuffJacket full coverage, TuffCutter bits set the benchmark, making two 2,500-ft runs in abrasive formations with minimal tooth wear at outstanding penetration rates.

DuraForce cutters

The process used to make PDC cutters is complex and results in high internal stresses in the polycrystalline diamond. These stresses can lead to the loss of large pieces of diamond (catastrophic diamond table loss) when the cutter is subjected to high static or dynamic loads.

ReedHycalog’s DuraForce cutter bits demonstrate outstanding performance in applications where cutter overloading leads to catastrophic diamond table loss. Cutter overload can result from bit vibration, such as whirl, or from the use of very high weight on bit at high ROP, particularly in interbedded formations.

DuraForce impact resistant cutters are the latest generation of Thermostable PDC cutters with dramatically enhanced toughness. By re-engineering both the materials and geometry, ReedHycalog DuraForce cutters reduce the risk of catastrophic diamond table loss, thereby improving bit performance. In the field this equates to consistent increases in durability, and penetration rate with reduced drilling costs.

Record drilling in Louisiana

The 83?4-in. DSF713 bit with 13 mm DuraForce cutters set a record for ROP and interval in De Soto Parish, La. The bit went in at 8,065 ft (2,459 m) and drilled 3,335 ft (1,017 m) at an average ROP of 32.1 ft/hr. When compared to the offset average, the DuraForce bit achieved:

• 90% faster ROP;

• 312% increase in interval drilled;

• 65% lower CPF; and

• Savings of approximately US $200,000.

High ROP in Texas

Another record run was achieved in Garza County, Texas, where it typically takes two or three bits to reach total depth through the target interval. The 77?8-in E1046 bit, equipped with 16 mm DuraForce cutters, drilled the 6,020 ft (1,836 m) interval in 107 hours at an ROP of 56 ft/hr. The bit drilled more footage at a higher rate of penetration than any other bit in the area.

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