Figure 2. Casing is hoisted in preparation to be stabbed by the CDS. Note the absence of a stabber in the derrick, who would be required during conventional casing running operations.

Repetitive action in the casing running process is the most dangerous stage for personnel when drilling and completing a well.

While the crew-less rig has yet to appear, various systems have been developed and commercialized that reduce the number of rig and third party crew necessary to perform casing running operations. In some cases, automation has actually resulted in eliminating personnel from some areas of the rig such as the stabbing board and rig floor. This is especially true when using Tesco Corp.’s proprietary casing drive system (CDS) to run casing.

The CDS initially was developed to enable drilling with casing. It later was proven to be a significantly better performing and safer method for casing running operations. The CDS can be used under all top drive drilling system-equipped rigs, and provides all of the advantages of a top drive system to casing running services including the ability to circulate, reciprocate and rotate. This ability improves getting over ledges, through tight spots, and improves chances of getting casing to bottom.

Automating the casing running process also increases safety by limiting the amount of equipment and crew necessary on the rig floor. Typically, the casing running process is accomplished with half the normal crew. The stabber, tong operator, tongs, fill-up tools and bails are completely eliminated, thus increasing safety by eliminating potential falls and other hazards.

There are alternatives to the CDS when automating casing running services. However, those options still require a stabber in the derrick. Additionally, there have been collision issues with stabbing arms and elevators, so there is still the potential danger of heavy equipment colliding high in the derrick. The company’s approach to automation of casing running services is to remove stabber and equipment obstacles in the derrick, and additionally reduce rig floor personnel.

Automated casing running system
The CDS tool is rated up to 500 tons, can handle casing from 4½-in. to 20-in., and is only 12 ft (3.6 m) in length. It is small and light enough to be moved with a forklift and makes up directly to the saver sub of any modern top drive. Once the CDS is installed and the hydraulic service loop is rigged up to the remote control console, the driller controls the casing running process with the assistance of the CDS operator. The integrated link tilts and hydraulic single joint elevator enables the smooth and safe operation of picking up casing from the V-door. This link tilt system is adjustable to allow the CDS to be used on a variety of rig floor layouts.
The casing is hoisted, positioned over the hole center and stabbed into the casing. The CDS grapples engage the inside diameter of the casing and the joint is rotated using the top drive. The dies used to grip the casing are very similar to pyramid dies used for handling chrome tubulars. The company’s proprietary non-directional dies hold the casing for vertical loads up to 500 tons and rotational torque of 40,000 ft/lbs.
Once the CDS has completed the makeup, the driller can fill the pipe with mud and break circulation on the fly. The top drive allows for a smooth make-up with precise control of the final torque. When the connection is assembled, circulation can be initiated and the CDS is used to rotate and/or reciprocate the entire casing string, significantly increasing the chances of getting casing to bottom.
The CDS replaces traveling elevators and supports the entire casing string load. It is used to lower the casing string into the well. Since no elevator is used and the CDS grips internally, the casing can be set at a comfortable working height, eliminating the need for a personnel work platform.
The process of running casing with the CDS is essentially the same as making up drill pipe, minimizing the driller’s learning curve as the CDS operator functions the link tilts and sets the grapples.
The CDS is designed using the same quill feature found on most top drives. The actuator body, hoses and link tilt do not rotate in the derrick. This reduction in rotating mass results in better torque makeup for API and premium connections. Additionally, since only the inside quill rotates, rotating speeds are equal to the maximum output speeds of the top drive.

Automation provides additional benefits
A broad suite of accessories enhances the CDS operational capabilities. Torque and drag information must be analyzed in order to determine if an API or premium connection can handle the rotational torque required to turn casing on bottom. The patented, multilobed torque rings are critical when using any API connection where torques are higher than the connection makeup torque. In some cases, installing the rings will triple the amount of torque that can be placed on the connection. The rings can be installed at the pipe yard or at the rig site.
The company’s patented process hydraulically presses a multi-lobe ring into the “J” dimension of the coupling to insure a proper standoff of any API connection. The new delta torques will ensure that the maximum amount of torque can safely be applied to enable the drilling engineer to rotate the casing string without advancing the connection. Because the CDS allows casing to be rotated, bowspring centralizers cannot be used without the danger of them coming apart downhole. To remedy this situation, patented Hydro-Form Centralizers can be crimped into place and safely rotated for purposes of standoff.

Case study
ExxonMobil set a North American record for an extended reach liner using the CDS system in its Sacate SA-1 well drilled from the Heritage platform offshore Santa Barbara, California. In order to maximize the well’s production potential, the operator designed an “S” shaped well bore with an extended reach 22,263 ft (6,790 m) liner. The liner was a tapered string including 2,566 ft (782 m) of 10 ¾-in. 55.5 lb HC-L80 Hydril 563, and 19,700 ft (6,008.5 m) of 9 5/8-in. 43.5 lb HC-L80 Hydril 563. The liner was set at 29,873 ft (9,111 m) measured depth with a true vertical depth of 5,563 ft (1,696 m). The kick-off point was 2,895 ft (882.9 m) and the horizontal reach was 24,800 ft (7,564 m). Due to the extreme reach of the well, the casing was floated in using buoyancy to aid in running the casing.
A key success factor in setting this string was the requirement to rotate the casing while running to break friction and reducing drag by a measured amount of 19,000 ft/lbs as the casing was rotated. Every joint of casing was rotated after the liner reached 11,700 ft (3,568.5 m) measured depth.
The CDS was rigged up and ready to run casing in 1½ hours. Total running time was about 34 hours, resulting in a run rate of 16 casing joints per hour, the speed of which was aided by use of the CDS. Non-productive time to change from 9 5/8-in. to 10¾-in. casing was only 15 minutes. The casing running and reaming operation was accomplished without incident or accident. The CDS’ automatic capability and zero learning curve by the driller helped to make this record-setting job successful.