Abstract

New developments in drilling tubulars are rapidly evolving and represent enabling technologies for the industry's continued advancement of drilling deeper, further and more cost-effective wells. Much focus has been made toward the advancement of drill pipe connection technology to permit high torque drilling of extended reach, directional and horizontal wells. First and second generation high torque connections have been available to the industry for several years.

In today's rig market; deepwater, extended reach and ultradeep wells dictate large spread rates that can benefit significantly from reduced tripping times. These same wells often have mechanical and hydraulic load requirements for which today's high torque connections may not be specifically optimized.

In response to this need, the development of third generation, ultra-high torque connections is now complete. This paper will present the results of a 2–1/2 year comprehensive effort to design, test, manufacture and field trial a family of connections that were engineered to meet the specific needs of each drill pipe size. Results from extensive laboratory tests and two field trial programs designed to produce harsh, aggressive dynamic loads to the connections are presented.

The thread form is a double-start thread that reduces the number of revolutions to assemble the connection by 50%. The thread form also provides a unique dual-radius thread root that offers a step change improvement in fatigue resistance. Conservative estimates suggest that the new connections will save approximately 7–1/2 hours in planned trip time per 20,000 ft well. The new connections provide increased mechanical and hydraulic performance compared to second generation high torque connections while also providing fatigue performance greater than standard API connections. These connections can facilitate more challenging wells, provide increased cost savings and reduce risk during the well construction process.

Introduction

The current trend to drill offshore in deeper waters, longer extended reach wells and record setting ultra-deep wells is destined to continue. Many rig contractors are presently upgrading or building new jack-up, semi-submersible and dynamically positioned drill ship rigs capable of drilling to 35,000+ ft total depth (TD). One rig contractor, in particular, recently contracted the manufacture of three $650 million USD dynamically positioned drill ships capable of drilling in 12,000 ft of water to well depths of 40,000 ft.(1) Wells that are in the planning stages today demand drill string technology with capabilities that exceed current connection designs and material performance properties.

As mentioned above, rig rates have risen dramatically, as have the costs for virtually all services, equipment, tools and materials used by the energy drilling industry. At the same time, existing wells and reservoirs are experiencing accelerated decline rates. Our industry must respond to these realities with advanced technologies that improve efficiency, enabling wells to be drilled more effectively and at acceptable costs. Drill pipe and drill stem materials and connections represent mature technologies. Nevertheless, innovations can and are being developed in this important area critical in the quest to exploit more remote hydrocarbon target zones. The third generation double-shoulder connection presented in this paper represents one advancement that addresses some of the drilling challenges ahead.

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