IDEAS Certified 7-7/8-in. Outlaw (Mi616) PDC bit with advanced cutter technology and new cutting structure design. (Image courtesy of Smith International)

Smith Bits recently introduced Outlaw Series polycrystalline diamond compact (PDC) bit technology specifically designed to drill hard carbonates and abrasive sandstones.

Historical perspective

The encroachment of PDC bits into fields previously dominated by roller cone bits continues at an ever-increasing rate, resulting in significant performance improvement.

However, since 2003 when PDC products first gained acceptance in the Texas Panhandle, one specific application remained particularly troublesome. Drilling the vertical 77⁄8-in. hole section from the surface casing to the top of the Granite Wash formation continued to be plagued by inconsistent performance, which was driving up field development costs.

The major issue preventing consistent PDC bit performance is the wide range of formations that must be penetrated in the 77⁄8-in. hole section. A typical stratigraphic section generally includes the Anhydrite, Brown Dolomite, Penn Shale, Douglas, Tonkawa, and the Granite Wash. In the Brown Dolomite, stringers have compressive strengths up to and sometimes exceeding 30,000 psi, making bit stability an issue. The bit vibration generally associated with drilling these harder formations can cause cutter damage in the form of chipped, broken, and/or spalled PDC compacts.

In many cases, two to four PDC bits were required to reach the top of the Granite Wash at approximately 11,000 ft (3,355 m) total vertical depth. To achieve a successful run, operators require a PDC bit design that is durable and stable in the hard limestone but has sufficient wear resistance to remain sharp through the abrasive sands to top the Granite Wash while drilling at an acceptable rate of penetration (ROP). To identify the barriers to efficient PDC performance, the drilling team conducted an in-depth engineering study.

After identifying the challenges, Smith’s engineering team set an aggressive performance objective for the 77⁄8-in. hole section as follows: Design a PDC bit that can consistently drill out the 95⁄8-in. surface casing shoe, then continue drilling the Pennsylvanian overburden and top the Granite Wash formation at an average ROP of 50 ft/hr (15 m/hr) in one run.

Outlaw technology platform

To identify the root cause of drilling inefficiency, key data points from different operators were entered into Smith’s integrated dynamic engineering analysis system (IDEAS). Using field data and technical information derived from the simulation, engineers created the new Outlaw PDC product line by combining advanced PDC cutter technology with new cutting structure designs. The new cutters offer unprecedented toughness for efficient hard formation drilling and good abrasion resistance for the sharp sandstone intervals. To further enhance durability, the bit is specifically designed to remain dynamically stable in all formations encountered in the target interval, virtually eliminating vibration-induced cutter damage and extending the service life of expensive downhole tools.

Performance results

Since their introduction to the region in 2008, the Outlaw PDC bits have set six county ROP records and three county footage records in the Texas Panhandle and western Oklahoma. Average Outlaw ROP in the study area is 55 ft/hr (17 m/hr) (169 runs), 10% faster then the target objective of 50 ft/hr (15 m/hr). Average Outlaw footage drilled in the area is 7,793 ft (2,377 m), a 50% increase from Smith’s 2007 average of 5,208 ft (1,588 m).

The consistency of drilling out from surface casing and penetrating past 11,000 ft (Granite Wash) has improved 294% from the Smith high of 11% in 2005 to a current 42% success rate in 2008. The Outlaw Series PDC technology has achieved the target goals of consistently drilling more footage while increasing average ROP, making it the preferred PDC bit for this application.