Overview: Bit Technology and Bottomhole Assemblies (December 2007)

Abstract

Drilling Performance Improvements—Push Into New Horizons Increased global demand for oil and gas has created situations in which operators are forced to drill deeper and into much harder formations. These drilling environments present enormous operational and technical challenges. In addition to the low rate of penetration (ROP), downhole tool failures occur at much higher frequencies. As a result, operators must make multiple trips to replace drill bits and other downhole tools, thereby incurring additional operational costs. The known challenges of hard-formation drilling are compounded by the effects of depth, primarily the result of elevated downhole pressure and temperature. To reduce operational costs in such applications, ROP and downhole-tool reliability must be improved substantially. Researchers, focusing on these challenges, have identified the need for system-based solutions. Such an approach evaluates all the elements that influence the drilling process. Researchers have gained valuable insights into the effects of depth and pressure on the properties and behaviors of different rocks. Consequently, the drilling efficiencies of different bit types, in terms of their energy requirements, also have been studied. To complement these efforts, specialized data-acquisition tools that can be placed inside the bit have been developed. These tools detect dynamic events at the bit/rock interface, which makes the data more relevant compared to data from previous tools. The effects of different drilling fluids or additives on the rock-failure process also have been studied extensively. As part of the system-based solution, the drilling process must be executed effectively. Drilling-system definitions must facilitate efficient energy transfer to the drill bit. Energy received at the bit must be used to cause rock failure, not be lost through vibration events. In addition, system or operational flounders must be identified and resolved in real time to minimize their negative effects. Considering the understanding gained and the tools that have been developed, performance gains now can be made in hard-rock applications. Bottomhole founder contributes to poor ROP in hard formations. In addition, vibration founder has been classified as contributing immensely to poor ROP and downhole-tool failures. Tools are being developed that can withstand higher operating temperatures. We know the contributing factors as well as the science behind the problem—now, let us go after this problem aggressively. Bit Technology and Bottomhole Assemblies additional reading available at the SPE eLibrary: www.spe.org SPE 104502 "Maximizing Drilling Performance With State-of-the-Art BHA Program" by David C.-K. Chen, Halliburton Sperry Drilling Services, et al. SPE 107530 "How To Select PDC Bit for Optimal Drilling Performance" by R. Nygaard, University of Calgary, et al. SPE 105565 "Aggressive Drilling Parameters Capitalize on Cutter Technology and PDC Frame Advancement in Mature Field" by Peter Langille, Marathon Oil Company, et al.