Numerous failures of high-pressure piping used to connect nitrogen supplies to coiled tubing (CT) units drove the development of a new approach to CT operations. Pipe and connections often aren't properly maintained and tested, and the heavy, high-pressure pipe is awkward to carry and hook up. On some jobs, where access to the tree is tight, hundreds of feet of pipe might be run, with the sections connected using hammer unions. Lifting and hammering injuries are not uncommon.
Eliminating the high-pressure piping would significantly improve worker safety, and the only way to eliminate it is to combine the CT and nitrogen units so they would be permanently connected. That concept was the basis of WISE (well-intervention services and equipment) multifunction CT units.
Economics also drove the multifunction concept. With the cost of fuel driving transportation costs up, having fewer vehicles going to the wellsite saves money. So, in addition to eliminating temporary piping, the goal was to fit as many well-intervention functions on a trailer as possible. The multifunction concept also reduces personnel costs. The multifunction unit usually requires only three people instead of the six or seven that conventional methods typically employ.
The first unit combined CT and nitrogen systems on a single trailer along with a crane and a control cabin. All the systems were hydraulic, with the truck engine driving the multiple hydraulic pumps. Although this initial effort encountered overheating problems in the field, the problem was solved by going to a larger truck engine and adding a cooler. In 2003, the industry's first multifunction well intervention unit was operational.
For jobs requiring pressure pumping, a small trailer was added that carries a pump skid and power pack. The trailer is towed to the well site by a pickup truck. Now only a single tractor-trailer and the towable trailer could perform almost any kind of CT intervention. Conventional CT services require four tractor-trailers to do the same job.
Faster rig-up and rig-down
Another benefit of eliminating the temporary high-pressure lines is that rigging up at the well site is much faster. The system positions the pump trailer next to the CT unit. Only one short, high-pressure line is run, and the system can be up and running in an hour or 2, compared to a full day for conventional equipment. The compact CT system can also get close to wells in tight locations.
Centralized control
All operations are controlled from a single cabin and console, which is a major safety benefit. CT jobs are noisy. With conventional equipment, people operating the different units communicate using headsets or by yelling and signaling. If anything goes wrong, it can take several minutes to shut everything down. With one person at a single console in control of the entire operation there is no communication problems. The control-system operator can respond quickly and shut everything down instantly if necessary.
Offshore: three functions vs. one
The WISE multifunction concept is also perfect for offshore. Three intervention functions - CT, nitrogen and pressure pumping - are combined on only four compact skids. Altogether the offshore system is half the size and weight of a conventional spread that does not include the nitrogen or pressure pump services. The skids are sized and configured for economical transportation and easy lifting and installation, even in confined deck spaces. The WISE system has been used on the smallest platforms in the Gulf of Mexico, which means any offshore well can now be serviced economically. Costs are also reduced by eliminating two 18-wheelers taking equipment to the dock.
First amphibious CT unit
WISE multifunction CT technology has extended into marshes and shallows. The company recently performed the first well intervention from an amphibious vessel in Louisiana's Timbalier Bay. The marsh buggy, which had been purpose-built to support environmental services, can reach locations in marshes and tidal locations that are inaccessible to other types of vessels. The buoyant vessel travels through water under its own power but also has wide, low-load tracks that carry it over low-lying land and shallows. The deck of the buggy easily accommodate all the WISE systems needed to perform a pressurized nitrogen well cleanout. It is the only complete CT intervention system that can fit on the buggy deck and meet weight requirements. In the future, the company plans to add wireline and plug-and-abandon capabilities, creating a full workover system that can reach any well in shallow inland or coastal waters.
Eliminating liquid nitrogen
Another WISE innovation is a mobile nitrogen-generating unit that delivers 97%-plus pure nitrogen at the well site, using proven membrane air-separation technology. Again, safety was the motivator, because liquid nitrogen is hazardous and hard to handle. But there is also an economic benefit. Transporting liquid nitrogen to remote locations is expensive, and in some international markets it is not available. The membrane technology already existed and was adapted to the WISE system. The company has built and tested its first WISE N2 unit, which is already working in the Barnett Shale in Texas with good results. The long-term goal is to completely replace liquid nitrogen in the field.
The future
The company is adding other intervention services to the system to extend its capabilities. The ultimate goal is to deliver a complete package of well-intervention services. CT intervention will play an increasingly vital role in meeting world demand for oil and gas. Multifunction technology will make it possible for safe, economical CT intervention to be available in any part of the world.

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