Technical Paper: Constructing Difficult Colony Wash Lateral With Innovative Rolling Cutter Technology Improves Drilling Performance

Society: SPE
Paper Number: 167956
Presentation Date: 2014
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Efficiently drilling the lateral hole section through the abrasive Colony Wash reservoir sand in western Oklahoma creates a unique challenge. The highly heterogeneous formation was causing inconsistent PDC bit performance while constructing the 6 1/8-in horizontal and thus damaging project economics. A study determined that improved ROI could be achieved by extending bit life in areas where poor drilling performance is expected. A detailed forensic analysis showed extensive cutter damage with abrasive wear being the most common dull characteristic. The cutter wear was causing short runs and frequent trips for bit change-out. To solve the problem required a new approach. 

A fixed PDC element creates an inherent limitation because only a small portion of the cutter contacts formation and as the cutter wears, drilling efficiency declines. The resulting wear flat generates a high degree of frictional heat which breaks the diamond-to-diamond bond leading to accelerated cutter degradation. The situation is exacerbated by difficulty transferring weight-on-bit due to extended length lateral drilling. 

An R&D initiative was launched to investigate different methods to enable a PDC shearing element to fully rotate while drilling to increase overall cutting efficiency and bit life. Engineers investigated several different retention methods and developed a specialized fixed housing which is brazed into the bit blade. The PDC cutter is mounted on a circular shaft and fitted within the housing allowing 360° cutter rotation. The robust system holds the cutter/shaft assembly securely in the housing for superior reliability. The rolling cutter (RC) assembly has essentially the same OD as a standard PDC cutter for superior design flexibility and cutter placement options. The assembly was modeled using an FEA-based system and then tested in the laboratory to evaluate function and strength. Experiments confirmed the RC was able to shear an extended section of rock with a consistent force level (lbs). Conversely, the traditional fixed-cutter assembly required steadily increased force to drive the cutter the same distance. Examination of the rolling cutter’s dull condition clearly indicated significantly improved durability and cutting efficiency. 

A new-style 6 1/8-in PDC (MSiR613) was manufactured with rolling cutters strategically positioned in the shoulder area. It was field tested in the Colony Wash formation and has delivered positive results. On a steerable motor, the RC equipped bit increased total footage and ROP. In the Colony/Granite Wash application across Texas and Oklahoma, which contains more than 70 rolling cutter bit runs since January 2012, the 360 technology has increased average footage totals by 56% compared to 450 offsets drilled with conventional fixed cutter PDC bits from various manufacturers. The authors will present results of field tests and specific case studies that document performance improvement in this challenging drilling environment. They will also outline plans for future development.

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