Tracking prevention in roller cone bit drilling

In the world practice of open pit mining, drilling is mainly carried out using roller cone bits. The cost of drilling totals 25–40% of the overall cost of mining. One of the factors which worsen drilling efficiency is tracking which occurs when spiked teeth of the cones fall into the same craters cut during previous rotations of the bits, and which increases wear of the drilling tool and decreases the rate of drilling. This article proposes a calculation algorithm for the contact paths of teeth in the peripheral rows of roller cones using actual involutes of toroidal surfaces in the periphery of the well bottom. The algorithm provides a sufficiently accurate mesh of coverage of the well bottom periphery by tricone drill bits with the offset spin axes of roller cones with a view to preventing tracking. The proposed algorithm can be used for the design and reasonable selection of the roller cone bits with regard to geological conditions of drilling.

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