Durable and time-tested, the roller cone bit has evolved many times since it was first introduced in the early 20th century, keeping pace with the industry’s continued foray into formations that push the limits of drilling technology. Designed with conical cutters, or cones, surrounded by spiked teeth, the bit rolls along the bottom of the hole as the drillstring is rotated, continuously crushing rock and removing rock chips with fluid jets.
A major breakthrough came in the early 1950s with development of the tungsten carbide insert (TCI), a significantly more wear-resistant cutting element especially suited for hard-rock drilling. Typically, a TCI bit features inserts laid out in concentric rows, with each row forming outwardly concentric rings on the bottom of the hole while drilling ahead. However, due to intermeshing, or overlapping between adjacent rows, the teeth can create ridges of rock that cause the bit to fall back, or track, into the resulting grooves and craters between the rows of teeth. This tracking phenomenon reduces overall bottomhole coverage and puts additional stress on the inserts, often causing breakage, resulting in reduced rates of penetration and increased rig time.
An article in E&P online “Making the Cut: Drilling Technology Aims to Optimize Performance, Improve Economics” describes how through advances in digital simulation and modeling technology, Smith Bits, a Schlumberger company, engineered the Xplorer Helix spiral TCI configuration to overcome this limitation and meet operators’ ongoing needs to optimize performance and improve field economics.
Launched as an expansion of the Xplorer premium roller cone drill bit portfolio, the new design uniquely arranges the inserts in a staggered, spiral pattern that has been shown to improve ROP from 20% to more than 50% in some conditions. The article includes a case study from the Middle East. Read the full article here on the E&P site.