Allan PLESKIE, Technical Sales Representative – Oilfield Products, Foremost Industries

 

The concept of drilling with coiled tubing has existed as early as the mid 1930’s. However, the potential of drilling with coiled tubing conveyed technologies have only become evident within the last decade. Today, is has become clear that coiled tubing can be used quickly and competitively to drill a wide variety of well bores in North America and around the globe.

 

Coiled Tubing (CT) technology was initially developed as a means of clearing out wells. Coiled Tubing Rigs (CTR’s) have since evolved into a technology that has a wide range of applications in the oilfield. Early attempts at drilling with coiled tubing utilized modified coiled tubing deployment equipment that was available at that time. Although these initial attempts were moderately successful, the limitations of early coiled tubing technology were ultimately ineffective in the overall execution of drilling and casing wells. Early CT equipment was not effective at drilling surface holes, and not able to handle or run jointed tubulars. The equipment was also difficult to rig up and difficult to transport between site locations.

 

In 1994, the first attempts at drilling with coiled tubing in western Canada occurred near Medicine Hat, Alberta using rigs adapted from other applications. Although it demonstrated the possibilities of drilling with coiled tubing, other parts of the operation proved ineffective and the project was abandoned. Advancements in CT technology continued to develop into the mid 1990’s, however no rigs specifically designed for the purpose of drilling with large diameter tubing had yet been manufactured. It was this challenge that spawned a revolution in CT rig design, making way for “fit for purpose” hybrid coiled tubing drill rigs.

 

In 1997, the first generation Coiled Tubing Rigs (CTR’s) were born out of a modified coiled tubing service rig. This modified rig addressed a few of the issues from past experiences. The rig was trailer mounted, improving its mobility and included a mast to run tubulars. These rig designs improved drilling and tripping times due to the elimination of tool joint connections. They also allowed for continuous fluid circulation, creating a smoother and more stable well bore while decreasing formation damage. These first generation rigs were also safer than conventional rigs. There were less people involved in the process on the drill floor, no derrick hand was required and there was no requirement to join pipe. The rigs were also smaller and could be moved in compact loads, resulting in reduced environmental impact. By 2002, more than 6,200 new wells had been drilled in Canada using these first generation rigs, further demonstrating the potential and benefits of using coiled tubing technology. These rigs, however, were poorly suited for drilling surface holes, and were limited to drilling depths of less than 1,000 m.

 

In 1997, CT technology was commercialized when Foremost Industries was commissioned to engineer and manufacture a fleet of CTR’s unique to the specific requirements of production drilling. This led to the development of second generation CTR’s, which incorporated a top drive system to facilitate the drilling of surface holes, and the implementation of the powered cat walk, an automated tubular handling system, thereby evolving CTR’s into true hybrid drilling units. These units had increased injector capacities, up to 54 tonne, and hoisting capacities, up to 90 tonne, and included a coiled tubing storage reel, with capacities up to 2,100 m of 89 mm diameter tubing.  The first Hybrid CTR’s went into service in 1999 and immediately delivered improved production.  By the end of 2002, 35 second generation CTR’s were operating in North America and Foremost Industries collaborated with other drilling companies, on new and custom Hybrid CTR design configurations.

 

The development of the current, third generation CTR’s have been met by further increasing injector capacities, up to 90 tonne, and increased tubular hoisting capabilities, up to 136 tonne. More A/C driven components are utilized, which improve the reliability of these units while simultaneously reducing maintenance, and greater pipe and tool joint handling capabilities through automation.  Transportable loads are still maintained through modularized construction and storage reel capacities have been increased up to 3,000 m of 89 mm diameter tubing. A record depth of 3,034 m using 89 mm OD has been achieved using this design.

 

To date, Foremost has designed and manufactured the majority of Hybrid Coiled Tubing Rigs for drilling with large diameter coil up to 3-1/2’ (89 mm). Coiled tubing is one of the fastest growing areas of oilfield drilling. It has both practical and economic benefits; with the increased efficiency of the continuous coil, penetration rates of 250 meters per hour are commonplace. In addition, well bores are left more stable as the penetration rate is consistent and not subject to the problems associated with starting and stopping circulation while making connections.

 

Hybrid CTR technology not only allows for a variety of drilling applications, but the technology also allows drilling in more diverse formations. Risks of formation damage are reduced as fluid leakoff is avoided by utilizing underbalanced drilling techniques. Production strings can be installed under pressure, without killing the well, and tripping times are reduced because Coiled Tubing has no connections to make or break. This technology also allows drilling to be accomplished safely and effectively in vertical, deviated or horizontal wells.

 

Foremost Hybrid CTRs are also useful in well logging, well testing and other applications with down-hole conveyance tools. Strings with electric lines can be run to tools, which can identify and predict flow characteristics, and conduct stress analysis and cleanout analysis when connected to computers with analysis software. From the beginning of 2000 to the end of 2008, more than 35,000 wells have been drilled in North American using coiled tubing, proving that CTR’s are no longer a fad or curiosity, but have become a primary service and a key technology in the hunt for energy.

 

Foremost Industries, in conjunction with several major drilling contractors, continues to develop and improve capacities of hybrid coiled tubing drilling rigs.  As the industry leaders in the design and manufacture of Hybrid Coiled Tubing Rigs, Foremost continues to be committed to working with innovative customers to further the development of coiled tubing drilling.