Field Results

Drilling basement rock

New, counterforce assisted XC-AST Reveal Hard Rock Potential with PDC Bits


The cost of hard rock drilling grows exponentially with depth. The exponent is the individual drill-bit footage. Tomax took on a full-scale drilling test to demonstrate what could be done to PDC performance when the self-excited axial vibrations in a stiff system are replaced by the controlled motions of a purpose-built regulator.


A 6 ¾” XC-AST tool was made up in the BHA with a new, API class M333 PDC bit from Halliburton DBS. On bottom, the energy to drill, or Mechanical Specific Energy (MSE), was continuously monitored to look for wear and to compare against a reference run.

The new XC-AST produced a continuous ROP at 1.6 m/hr in South Scandinavian basement rock. There was no sign of wear from the MSE data.


The PDC technology represents the most energy-efficient kind of drill-bits. When the risk from axial impact is eliminated, these bits can drill practically any rock.