Craig H. Cooley

Application of Digital Technology Optimizes Bit Selection to Cut Drilling Costs in Torrente Cigno Field-Italy

This paper describes how digital technology was used to make a landmark bit selection decision that significantly reduced drilling costs in Torrente Cigno field of central Italy. The operator used a new computer program that converted open-hole log data from an offsetting well into a digital format select an appropriate bit for the expected drilling conditions. This new tool analyzed rock mechanics and helped the operator determine that a particular limestone section in the field traditionally drilled with roller cone bits fell within the limits of new polycrystalline diamond compact (PDC) bit technology. A medium set bit was selected with polished cutters and sufficient face volume and junk slot area to allow efficient drilling through shale. The bit also incorporated a newly developed high impact strength cutter with a highly stabilized layout to resist premature damage while drilling the limestone section. The bit drilled the lime faster than planned and also maintained a good rate of penetration through the shale section under controlled parameters. The bit came out of the hole in excellent condition. The authors will discuss how the software program unraveled the complex problems associated with calculating rock strengths of the Miocene allochthonous and Pliocene formations. The output of the program, which uses empirical formulas derived from statistical observations and tests, gave the operator the confidence to run a PDC bit for the first time in the lime/shale sequence. This combination of new bit and cutter technology along with the innovative log analysis techniques allowed the 8 1/2 section of the well to be drilled with one bit for a savings of

Diamond cutting structure for drilling hard subterranean formations

423,000 US compared to the offset well.