MWD INTERPRETATION TRACKS BIT WEAR.

A new realtime, measurement-while-drilling (MWD), interpretation technique uses MWD downhole-weight-on-bit and torque sensors to monitor bit-tooth wear and to diagnose bearing failure. This article describes the results of the mechanical efficiency log (trademark MEL). In this example the efficiency calculation determined when to pull the bit and saved an estimated 114,000 in potential fishing expenses. Normal procedures for evaluating bit efficiency use surface measurements of weight on bit and torque which are often influenced by the interaction of the drillstring with the well bore. MEL, however, uses two surface measurements: rate of penetration and bit rotation speed, and two downhole measurements; MWD downhole torque and downhole weight on bit.