This paper will discuss the deployment of the concentric dual-diameter fixed-cutter bit technology, which was introduced in January 2015. The bit was deployed and tested twice in a vertical application in Burgan Field south of Kuwait and achieved the fastest penetration rate in the application.

The concentric dual-diameter bit is composed of a smaller pilot and a larger reamer section, where the reamer section dictates the final drill size. Conventional fixed-cutter bits take very little advantage of stress-relieving the rock, as it only affects the borehole wall. Concentric dual-diameter technology bits are able to initially drill with a leading smaller pilot section efficiently to relieve the stress of the rocks. Subsequently, the reamer section removes the stress-relieved rock with lower mechanical specific energy compared to regular fixed-cutter bits, giving it the advantage to generate higher penetration rates. Another advantage of the concentric dual-diameter technology bits is the stability of the bit, since two gauge sections are available to be in constant contact with the borehole while drilling.

The 12 ¼ in. concentric dual-diameter technology bit in conjunction with a packed rotary BHA was tested in a vertical application in the Burgan Field south of Kuwait. The bit was able to deliver improved performance, achieving the fastest penetration rate of 152.4 ft/hr. The section drilled was 762 ft in length and consisted of shale and sandstone.

The performance capability was confirmed when the same bit was reused again in a similar application subsequently and was able to deliver the same consistent record penetration rate of 152.5 ft/hr. The section length in this second run was 610 ft. and consisted of similar lithology of shale and sandstone.

The 12 ¼ in. concentric dual-diameter bit was able to surpass the average rate of penetration for the same application in the Burgan Field by 35%, saving the operator drilling time and making the concentric dual-diameter bit design the top performing drill bit in the field.

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