Environmental Applications
Whether the goal is to contain environmentally hazardous cuttings, obtain an accurate profile of the formation or just keep a clean job site, the DR method is ideal. Environmental Sampling As in placer drilling, casing can be advanced ahead of the drill string so cuttings do not mix with material from the borehole wall as they exit the hole. Cuttings remain representative of the material at the bit face. In recent years, some US Government authorities have specified the DR method for a growing number of projects because it is possible to drill and case without introducing water or mud into the formation. On critical environmental sites, a DR can install casing and retrieve cuttings into containers without releasing water or unfiltered air into the atmosphere. The DR can also be fitted with Reverse Circulation (RC) hammers and tooling, which can be beneficial when drilling in contaminated soils, or when sampling in open-hole applications.

Re-Charge Wells
The DR effectively uses casing to seal off the strata above the recharge reservoir. This prevents undesirable material or substances such as salt from bleeding further down into the formation and causing cross-contamination. And, because drilling is accomplished without the use of drilling mud, there is no danger of plugging or contaminating the underground reservoir.

Other Applications
Cathodic Protection
DR rigs offer an advantage when anodes must be buried in overburden or when casing is being set to house the sacrificial anode.

Hollow Stem Auger Drilling
For special limited applications, hollow stem augers can be fitted to the lower rotary drive using an optional adapter.

Kelly Driving
The torque of the lower drive can be added, via kelly bar, to the torque of the top drive to
enable large diameter open-hole drilling. This is useful where the required borehole diameter
exceeds the I.D. capacity of the lower drive spindle or when the torque requirements
exceed the output of the top drive. Cuttings are typically evacuated using reverse flooding in this application

Oilfield Rat Hole Drilling
The Dual Rotary Method is being used in Western Canada by oilfield service companies
to drill rat holes, mouse holes, and conductor casing for oil and gas wells. In oilfield
applications, a 20" (508 mm) conductor casing is externally cemented into a 24" (610
mm) borehole to depths of 300 ft. (100 m), or more. In some cases, the DR method is
also being used to pre-set Range II surface casing.

SUMMARY
Since its introduction the Dual Rotary drilling method has gained worldwide acceptance as a cost-effective drilling technique. It has proven to be a viable alternative to more conventional methods when drilling in unstable overburden. Its flexibility and versatility continues to deliver economic advantage to drilling contractors. Without question, the Dual Rotary concept has contributed significantly to advancing the technology of overburden drilling.
For further information about the Dual Rotary drilling method and Foremost Dual Rotary rigs, including brochures, application videos, case studies and drill quotations, please contact Foremost Industries at:
Foremost Industries, LP
1225 - 64th Avenue NE, Calgary, Alberta, Canada T2E 8P9
Tel: 403-295-5800 • Fax: 403-295-5810 • 1-800-661-9190 Canada/U.S.A.