Regions of western Canada comprise tough interbedded formations of hard sandstone, siltstone, shale and chert, which create great challenges for directional drilling applications. Historically, using conventional tungsten carbide insert (TCI) rollercone drill bits to drill a directionally placed wellbore trajectory has resulted in low penetration rates and short runs due to the impact of high cyclic loading and damaging hole-wall contact on the bits. With WOB being preferentially loaded on the heel and adjacent heel area of the roller cone cutting structure during directional drilling, cutting structure breakdown is accelerated and seal failures occur. Additionally, rigorous hole-wall contact increases gauge and shirttail wear.
Extensive research, testing, and development have produced TCI rollercone bit designs that have addressed these major challenges. A multitude of design iterations have resulted in a new TCI rollercone drill bit that includes innovative cutting structures for improved durability and ROP, enhanced OD and leg protection to ensure bearing integrity and gauge-holding ability, and stronger materials and processes to withstand high cyclic loading of directional drilling. Drill bits designed with these features have been successful in increasing average footage per run by 121% while improving penetration rates modestly vs. offset drill bit runs in the western Canadian regions, which include Saskatchewan, Alberta, and British Columbia. Additionally, one-bit runs, as opposed to two or three, are now possible in builds to horizontal in many applications, thus reducing overall drilling time by over 25%, and significantly reducing drilling costs.
This paper will detail the directional TCI rollercone drill bit design features and technologies used as well as field results and case studies from Canadian-specific markets.
More and more oil and gas wells throughout Canada are being drilled directionally or horizontally. There are many reasons why Canadian operators are choosing to drill a well directionally, including:
Thin reservoir formations—Often, the vertical thickness of a formation to be produced is quite thin such that a borehole drilled vertically through the formation would have very little surface area downhole from which to produce. By drilling the well horizontally in the reservoir formation, a much larger surface area is exposed and production potential is greatly increased.
Restricted surface access—Often times, target formations to be drilled lie below areas that a drilling rig cannot access. These areas include environmentally sensitive areas, lakes or rivers, man-made structures, or areas for which the owner of the surface access rights does not want to grant access. This problem is avoided by setting up the drilling rig adjacent to the desired surface area and directing the wellbore laterally to target the zone of interest.
More efficient exploration—Many wells are now being drilled in areas that have been produced in the past, but not completely exploited. By drilling directionally, the operator is able to locate and produce zones that were previously undiscovered or bypassed.