The trend toward mechanized drilling systems began almost 2 decades ago, and new technologies are continuously being developed. The goal is an increase in safety for rig floor personnel and improvements in overall operational efficiency. Increased mechanization has driven both the implementation of new technology and the adaptation of existing equipment, helping the industry achieve safety and productivity goals that historically have not been possible.
Traditional casing or tubing running involves one crew member, the stabber, working thirty feet above the rig floor, secured to the rig only by a safety cable. The stabber's work is the most physically demanding and potentially dangerous job in the casing crew.
In the 1990s, several attempts were made to develop tools to remove human error from difficult makeup process with special pipe, but not necessarily with the intent to improve personnel safety or efficiency. In 1996, a system was introduced that allows stabberless running of casing and tubing strings. The system mainly consists of a hydraulically activated remote controlled arm that is mounted in the derrick and a remotely controlled set of a spider an elevator equipped with interlock and sensor systems. This system not only eliminates the job function of the stabber but it also allows much more precise alignment of the connection through position feedback and position memory control by the electronic control system. This minimizes delays because of cross-threading or damaged connections caused by out-of-center alignment of the joint to be stabbed.
The introduction of the programmable logic controller (PLC) and electronic position feedback systems enabled various mechanized rig systems, including alignment tools, to be controlled remotely. The combination of PLC technology with the alignment tool eliminated the need for mechanical adjustments in the derrick to achieve repeatable "fixed" joint alignment for tubular connections.
While this was a major advancement, these alignment tools still could not entirely replace the stabber in the derrick. Recognizing this concern, Weatherford created the Stabberless system, which is capable of running casing and other tubulars without a stabber in the derrick. Added features included remote control and interlocking of slip-type elevators and
spiders, flagging devices indicating correct elevator position before closing the elevator around the upper joint (no stabber or camera required in derrick to guide the driller), and dual hinged single-joint elevators that would not have to be opened up in
the derrick.

The system includes:
Derrick-mounted vertical alignment tool, which centers the pipe during stab-in, replacing a human stabber;
Elevator positioning indicator, which signals the driller at the proper height to close the elevator;
Stabberless single-joint elevator; and
Integrated Safety Interlock System (ISIS), which avoids accidental dropping of casing and tubing strings by preventing the spider and elevator from opening at the same time.
Initially, many drilling crews and casing-running personnel were concerned that dynamic rig motions would shift joint alignment on semisubmersibles and drillships. However, 10 years of experience have proven that not only does the system greatly improve safety and efficiency under normal weather conditions, it also enables continued operations during extreme wave and wind conditions when rigs with manual stabbing operations have to shut down.

Time savings
The first casing and tubing operations with this system were performed on land rigs in Holland in 1996. Today, hundreds of casing strings are run without stabbers and without accidents, with an average time savings of up to 30% over previous manual stabbing operations on the same rigs. The time savings is realized through simpler operation with a more precise repeatable alignment resulting in fewer cross-threaded connections, less thread damage and fewer rerun or rejected joints.
This system not only eliminates the job function of the stabber but also allows much more precise stabbing-in of the connection. Once the well center position has been found at the beginning of the operation, it is memorized by the electronic control system. Although the system was not originally designed to save rig time, studies indicate that the time savings benefit is significant.

Field acceptance
Reports from the field show that the time savings extends beyond pure casing running time. The physical force of the stabber sets certain limits to the ability to handle larger casing sizes, especially in adverse weather conditions. Usually, casing or tubing running operations are shut down when wind speeds exceed a certain maximum. This downtime is costly. The use of a mechanical system allows for continued casing running within a certain wind-speed window.
Clients find the system safer to use than having a man on the stabbing board, and the operation becomes generally faster and more controlled. Rigs with these systems are less affected by marginal weather conditions than those running casing conventionally with a man on the stabbing board. Savings realized through continued operations under harsh conditions can quickly offset a year's cost of the system's rental.
One client in the Gulf of Mexico experienced 40 to 50 mph winds with 80 mph gusts, well beyond ideal conditions to run casing with conventional methods. The casing and rig crew felt confident that they could safely run the casing job using the system.
The validity of the stabberless technology has proven itself in areas such as the Middle East, Venezuela, the Gulf of Mexico and the North Sea. On a major operator's offshore well in the Middle East, the system was installed for a trial period and reduced casing running times by 20% on 20-in. casing. Additionally, personnel exposure was reduced since the system is controlled by a dedicated operator on the drill floor. After the trial period on the first rig, a second system was fitted for another. Both systems increased efficiency and personnel safety over the course of a full year onboard two standard 250-ft (76.25-m) jackup rigs in offshore waters.

New designs and the future
When the system was introduced, it was mainly used on larger installations. More recently however, operators are beginning to use the system on smaller drilling and workover rigs. With joint lengths varying during workover operations, the standard alignment tool operating height of approximately 30 ft (9.15 m) was often too high for short joints. In consequence, a stabber was still needed. To improve the handling of pipe with variable lengths, a special alignment system was recently developed for an operator in Germany. The system allows remote shifting of the alignment tool between operating heights of 32 ft and 24 ft (9.76 m and 7.32 m) depending on the length of casing to be handled. Variations of the alignment tool with shorter and longer reach have been derived from the original tool design to suit applications from small to large rigs. The alignment tool can be fully integrated into casing running and drilling systems.
Incidents involving pipe running operations, proven field histories
with existing units, more demanding safety targets, and the desire for a more efficient running operation have resulted in greater acceptance for the system and the value it brings, demonstrating that the system is also viable in low-cost environments considered "unfriendly" to technology such as mechanized rig systems.
Although the primary function of the system was to enhance safety, 10 years of running experience, with over 100 tools installed worldwide shows that this system is capable of reducing casing, tubing or riser running times considerably, without compromising safety.

Comments