The introduction of new, wear-resistant polycrystalline diamond compact (PDC) bit cutter technology in recent years has dramatically increased the demand for increased torque output from the positive displacement motor (PDM). The commercial introduction of pre-contoured (i.e., equidistant rubber thickness) stators in 2000 solved the theoretical technical challenge of developing very high torque output in a PDM. Yet, in cost-sensitive, land-based drilling markets where conventional power sections are still a major factor, the requirement for traditional motor power section construction restricted the rate of penetration improvements.
Recent developments in the chemistry of the standard stator elastomer have enabled a step-change improvement in the performance and durability of the power sections in PDMs. This premium elastomer, manufactured in conventional stator cans, can generate higher differential pressure and subsequently more torque, while achieving increased durability, even in some of today's oil-based drilling environments. This higher level of torque and increased downhole durability is ideally suited for the increasing toughness and aggressiveness of today's premium PDC bit. This paper will review in detail this innovative motor technology, describe how it enables reaching higher performance levels, and present several case histories illustrating this performance enhancement.