Constructing Difficult Colony Wash Lateral with Innovative Rolling Cutter Technology Improves Drilling Performance

Abstract

Efficiently drilling the lateral hole section through the abrasive Granite Wash reservoir sands in western Oklahoma and the Texas Panhandle creates a unique challenge. The highly heterogeneous formation was causing inconsistent PDC bit performance while constructing the 6-1/8" 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 assembly has essentially the same OD as a standard PDC cutter for superior design flexibility and cutter placement options. A new-style 6-1/8" PDC (MSiR613/MSiR713) was manufactured with rolling cutters strategically positioned in the shoulder area. It has been run over 45 times in the Granite Wash formation and is delivering positive results. On a steerable motor, the RC equipped bit has increased total footage, hours on bottom and ROP compared to direct offsets drilled with fixed cutter PDC.

Study on rock breaking efficiency of special shaped cutters

“…Locating in the highest wear zone of the bit structure, the bit using the entire circumference of the cutting edge cuts through the formation, rather than leaking a fixed area outside the cutter. The 360° rotary action keeps the blade sharper, longer, and prolongs the use of the composite blade, and far exceeds the life of a conventional flat-cutter PDC bit [12].…”

Experimental study on PDC single-tooth flexible vibration reduction effect

“…However, the conditions of deep strata are often complicated. When drilling in uneven or alternate soft and hard strata, the bit will bear large bit weight and torque, resulting in severe vibration of the bit, which directly leads to the abnormal fatigue impact failure of the PDC bit cutting structure, the rapid failure of the drill bit, the obvious decline in drilling speed, and the significant increase in drilling costs [1][2][3][4][5] . According to statistics, the bit cost accounts for more than 20% of the drilling operation cost [6] .…”