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Slower ROP due to bit cleaning efficiency is now becoming history.
In the Anaima field in Oman, the carbonate and shale formations are not particularly abrasive, but frequent bit balling was slowing the ROP to an average of 20 m/hr to 21 m/hr (65 ft/hr to 70 ft/hr). The operator had been using mostly tungsten carbide bits. A switch to steel-body fixed cutter bits showed some gains as the ROP rose to an average of 30 m/hr to 32 m/hr (100 ft/hr to 105 ft/hr).
The lessons learned from this improvement were applied to the Halliburton SteelForce bit. The fine tuning paid off – while drilling the 12 1/ 4 -in. interval, the operator set a field record for drilling 1,634 m (5,360 ft) in 23 hours at an ROP of 71 m/hr (233 ft/hr). When the operator reached total depth (TD) for the interval, the new SteelForce bit was pulled and graded 1-1 – nearly new condition.
With higher penetration rates, lower cost per foot, and application-specific designs, the Halliburton SteelForce bit makes slow ROP (due to bit cleaning) history. The SteelForce bit features a large flow area and anti-balling coating to help with cuttings removal and bit balling. The SteelForce bit has premium cutter technology that provides abrasion and impact resistance and thermal mechanical integrity (TMI). The bit has achieved 87% faster ROP over the field average in Oman.
The success was accomplished primarily by resolving the bit cleaning issue. The steel-body bit has several characteristics that make this possible. First, steel is more ductile than tungsten carbide. The blades of the steel bit extend farther from the body, creating improved flow paths for the fluid emerging from the bit nozzles, which increases the ROP.
Another success factor is the expansion of nozzle types available to design. The different types allow greater flexibility to get the fluid flow in the places of the design where cleaning is most effective. This flexibility ensures that the SteelForce design is consistently faster and has less erosion than other similar bits in the fields.
To combat erosion in abrasive formations, SteelForce bits are coated in a new hardfacing that increases the amount of carbide pellets on the surface. This hardfacing helps extend the life of the bit so it can compete favorably with tungsten carbide bits. In addition, each bit has an anti-balling coating that changes the electrical potential of the steel to a strong negative. This repels the negative ions in the drilling fluid so a lubricant barrier of water forms on the surface of the bit, preventing the bit from balling.
The cutters, like the rest of the bit, are designed to extend bit life without sacrificing ROP. Traditionally, cutters provide abrasion and impact resistance, but thermal degradation can damage cutters through the differing expansion coefficient of the materials in the cutter. The ability of a cutter to manage the frictional heat generated during the drilling process allows it to stay sharper longer and wear at a slower rate.
Each bit is designed specifically for the application. The combination of these optimized features means the cutter bit will drill farther faster and reduce the cost per foot drilled.