Drilling Index—A New Approach to Bit Performance Evaluation

Abstract

Abstract The drilling industry has seen tremendous improvements in drill bit development and performance’. Technological advancements are being made by bit manufacturers in order to meet the continuously changing and more demanding needs of operators2-'4. Bits now stay in the hole longer and drill faster. Within this context, it is also worth noting that the application envelopes of all types of bits have expanded4-'6. Bit technology has evolved and continues to advance to meet the challenging needs of today's drilling industry. However, the means of evaluating drill bit performance improvements have not kept up with advancements in technology. Methods such bit factor, formation drillability, mechanical specific energy and cost per foot continue to be used for bit performance evaluation7. Although cost per foot is the most accepted method, its effectiveness has drastically been overshadowed by today's drilling needs and bit technology. This paper will present the Drilling Index (Dl), as a new approach to bit performance evaluation. It draws on the strengths of the older methods and establishes cost per foot as an indirect evaluation tool. Dl benefits from the greater understanding that has been gained by the bit industry with regard to product development and application. It defines performance, behavior, directional responsiveness and steerability as dimensionless parameters that reflect the operator's needs as well as the bit manufacturer's technological strengths.