Bakken is a soft shale play where increased rates of penetration can be obtained. The overarching goal is to achieve a one-bit lateral run (~9,500’) without having to trip; and if a rig has to trip in the lateral section it is usually because of tool failure and not necessarily the bit. In addition, the speed of a bit is very much tied to the motor on which it is run. All of the bit runs reviewed were run on the same high speed major-supplier motor and are also from the same rig, which has a good track record with their tools holding up; resulting in a rig that does not have to trip very often.
As the basis for improvement, the Varel design group and field engineer started with the already successful bit profile of the single row bit VM613, as this design’s steering features had yielded a number of high marks from the operator due to its ease of use. The new design, a 6” VM613P2 Navigator™ series, carries a more aggressive primary cutting structure, engineered in an effort to increase speed when compared to the original design.
In order to counteract the highly aggressive bit design, the bit is equipped with a PowerCutter™ backup row cutting structure (P2 feature). The Shoulder Durability Enhancement feature, a patent pending Varel innovation, allows the backup cutters to be situated on the three primary blades of the bit in an offset pattern.
Field run reports show that the bit design has been immensely successful in the Bakken Shale application for which it was designed. This bit was run over 72 hours yielding an overall ROP of 133 ft/hr, a full 45 percent faster than the offset average. The company men on this rig are also the directional drillers so steerability is a defining factor in their book. The rig complimented this new design on the ease and reliable steerability of the bit; it stayed consistently straight when they needed it to and it was very easy to slide when they required sliding.