Abstract

This paper provides a review of recent technology advancements and addresses practical considerations associated with drill pipe and drill stem components for extreme drilling applications. Ultra-high torque double-shoulder rotary connections are often employed in these applications potentially complicating proper design and material selection for cross-overs, top-drive subs, pup joints and other accessories These new connections often employ materials with higher strength requirements than the standard API connections they replace. The paper outlines recommendations for material strength and design parameters for various drill stem accessories. High-performance connectors' impact on BHA design is also addressed. Weight tapered drill string designs with double-shoulder connections can result in mismatched connection bores or ID's. Guidelines to accommodate this mismatch along with supporting finite element modeling results are presented.

Proper hardband selection, application and maintenance are essential to successfully and safely drill world-class UD, ER and deep-water projects. Hardband system trends for critical applications are highlighted, and recent hardband casing wear and tool joint protection test results obtained using an advanced hardband wear machine are discussed.

Due to the dramatic increase in oil prices the industry has seen a re-emergence of deep and ultra-deep drilling projects that encounter H2S gas. The paper provides initial results from a study of the effect on S-grade drill pipe samples to various H2S exposure concentrations, representing typical conditions when circulating a gas kick to surface.

The surge in critical drilling has led to an increasing trend of drill stem friction heating failures. The paper includes characteristic features of these failures along with case histories and prevention methods. High-speed telemetry (wired) drill pipe has been successfully deployed on critical drilling applications in various parts of the world. The paper provides an update on this exciting technology and reviews recent case histories.

Material Requirements for Drill Stem Components and Accessories

A drill string consists of many components. In addition to the drill pipe that is manufactured from upset and heat treated tubes with specified minimum yield strength (SMYS) values ranging from 75,000 psi to 135,000 psi or up to 150,000 psi and higher for the new ultra-high strength drill pipe with friction welded tool joints that are generally machined from forgings with a SMYS of 120,000 psi there are drill collars, heavy weight drill pipe, cross-overs, top-drive saver subs and pup joints. Proper material selection for each component is critical to insure safe drilling operations.

API specifications require material with SMYS of 120,000 psi for tool joints. API specifications permit lower minimum yield strength values for other drill stem components, see Table 1. Make-up torque values for connections machined on these other components with lower yield strength than the drill pipe tool joints must be adjusted down to account for the lower strength levels. If rig personnel are made aware of the lower make-up torque values and utilize these lower values when running the various components the string can be operated safely. Of course, these miscellaneous components can create a weak link in the string limiting maximum working torque for drilling operations. Often times the weaker components are only run near the bottom of the drill string where working torques are lower and the maximum surface drilling torques are not restricted by the weaker component. The situation can be further compromised with some of the newer proprietary connections that utilize tool joints with minimum yield strength values of 130,000 or 135,000 psi.

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