Emerging Coiled-Tubing Applications at Prudhoe Bay, Alaska
Abstract: Coiled tubing (CT) has been used at Prudhoe Bay since the early 1980’s, saving hundreds of millions of dollars in well servicing costs for such operations as cement squeezing, well cleanouts, stimulation, inflatable packers and plug placements, fishing, and temporary artificial lift applications previously performed by drilling/workover rigs. The majority of these CT jobs are currently conducted with 1-3/4″ OD CT which has proven to have excellent strength, capacity, and durability for typical field operations… Show more
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Cited by 4 publications
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A recently developed electromechanical precision pipe-cutting tool is being field tested. Its primary applications are to cut and free stuck pipe (tubing or drillpipe) or cut pipe to modify a production completion installation. Cutting pipe in today's complex completions presents many challenges. Testing of this new cutting technology has demonstrated significant advantages over previously used equipment. It is non-ballistic, has a large cutting range for a wide range of metal pipes, provides cut monitoring and success detection. The precision of the cut is facilitated by the tool's internal programming (smart function) which allows for specifying the type of metal to be cut, monitoring the depth of the cut, recognizing the drag and making the appropriate adjustments to complete a cut. The ability to complete multiple precise cuts reduces associated rig time. Its large operating temperature and pressure ratings (20,000 psi), large cutting size range, and portability make possible quick deployment to offshore and land operations. Additional field-demonstrated capabilities include: performs accurate smooth cuts, cuts harder metals with a high chrome content, performs precision cuts for inner pipe cutting, works at any deviation, produces minimum debris, surface system allows application to any wireline, does not require circulation holes for the cutting device, operation deployment is not constrained by chemical issues relate to safety and environment, the cutter's light weight, short shipping length (two sections, each less than 10 feet in length), and compatible portable support equipment allow for quick deployment in a variety of transport modes. This paper includes a case study to illustrate the operating challenges associated with tubing and drillpipe cutting in a variety of conditions and environments.
A recently developed electromechanical precision pipe-cutting tool is being field tested. Its primary applications are to cut and free stuck pipe (tubing or drillpipe) or cut pipe to modify a production completion installation. Cutting pipe in today's complex completions presents many challenges. Testing of this new cutting technology has demonstrated significant advantages over previously used equipment. It is non-ballistic, has a large cutting range for a wide range of metal pipes, provides cut monitoring and success detection. The precision of the cut is facilitated by the tool's internal programming (smart function) which allows for specifying the type of metal to be cut, monitoring the depth of the cut, recognizing the drag and making the appropriate adjustments to complete a cut. The ability to complete multiple precise cuts reduces associated rig time. Its large operating temperature and pressure ratings (20,000 psi), large cutting size range, and portability make possible quick deployment to offshore and land operations. Additional field-demonstrated capabilities include: performs accurate smooth cuts, cuts harder metals with a high chrome content, performs precision cuts for inner pipe cutting, works at any deviation, produces minimum debris, surface system allows application to any wireline, does not require circulation holes for the cutting device, operation deployment is not constrained by chemical issues relate to safety and environment, the cutter's light weight, short shipping length (two sections, each less than 10 feet in length), and compatible portable support equipment allow for quick deployment in a variety of transport modes. This paper includes a case study to illustrate the operating challenges associated with tubing and drillpipe cutting in a variety of conditions and environments.
In the past, tubing, casing and drill pipe recovery has been employed where chemical and explosive severing tools could not effectively sever the pipe. A coiled-tubing-conveyed hydromechanical pipe cutting system has proven to be a viable alternative to pipe recovery when conventional severing systems are not effective. The system does not contain or require any hazardous materials, which makes it safer to use than conventional systems. The pipe cutting system incorporates modular stabilizing devices that decrease the risk of the coiled tubing forces and the wellbore deviation from interfering with the cutting operation. The pipe-cutting mechanism uses several unique blade configurations that were designed specifically to address various metallurgical properties and dimensions. The cutting blades contain state-of-the-art cutting inserts, which were previously proved in various metal milling and cutting applications within subterranean wells. A detailed description of the coiled-tubing-conveyed hydromechanical pipe cutting system, its operational function and a variety of case histories are discussed in this paper. Introduction Electrical wireline-conveyed explosive jet and chemical cutters are currently the preferred choices for cutting pipe in slimhole wellbores. Explosive jet cutters are used for severing common sizes of production tubing, drill pipe and casing. The cutting action is produced by a circular-shaped charge. Typically, this type of cutter leaves a flare on the severed pipe string. In order to perform subsequent pipe recovery operations, it is necessary to smooth the top end of the tubing left in the wellbore with an internal mill insert that is usually run with an overshot1. Chemical cutters are designed to cut through one string of pipe while not damaging the adjacent string. They produce a flare-free and undistorted cut. The topside of the severed pipe can be engaged with an overshot without dressing with a mill1. A wireline-conveyance operation provides several advantages when compared to using coiled tubing and threaded pipe. Wireline equipment can be mobilized and disassembled quickly; the wireline can be run in and out of a hole much faster; and the cost of a wireline operation is usually less than other methods. The success rate can be reduced, however, when wireline-conveyed cutting tools are used for exotic applications such as cutting through plastic coated or corrosion-resistant alloys. High-density wellbore fluids, a greater-than-standard pipe wall thickness and distance between the cutter and the internal wall of the pipe also reduce the effectiveness of the wireline-conveyed systems. Another drawback is that the wireline systems are designed to cut only one string of pipe per operation. Therefore, several trips into the wellbore are required to separate multiple, adjacent strings internally. The limitations of wireline-conveyed cutters can be overcome for the specific applications noted above with a hydromechanical pipe cutting system (HPCS) that takes advantage of proven, downhole metal cutting technology. The HPCS is activated by weight or hydraulic pressure. It can be rotated by a downhole workover motor or from the surface using a rotary rig or power swivel. The HPCS provides the power needed to cleanly cut single or multiple strings of pipe downhole. Such non-distorted pipe cuts are especially beneficial when it is necessary to recover pipe that is stuck in open hole2. Time is a critical factor for a successful pipe recovery operation. The quicker the fishing jar assembly can be employed the greater the chances of a successful pipe recovery operation. The clean top of the severed drillpipe left by the HPCS improves efficiency in employing the fishing assembly3. History Until the early 1990s, very few pipe-cutting operations were attempted using coiled tubing as a conveyance means4,5.
Traditionally, completion engineers have faced a dilemma when deciding whether to run a large-bore, hydraulically set, permanent or retrievable packer completion. Thanks to advances in cutting technology, this decision is no longer an either/or proposition. The innovative alternative which has been enabled by through-tubing cutting technology is the removable packer completion. Combining a through-tubing-conveyed hydromechanical cutter with a "cut-to-retrieve" packer had never previously been attempted. In addition to providing an innovative solution for difficult service environments, the new capabilities gained by combining these technologies has led to the development of a work-string-conveyed method of cutting and retrieving the packer, thus enlarging the scope of viable applications for the removable packer completion. This paper will review the removable packer completion and the coiled-tubing-conveyed hydromechanical pipe cutting system and describe in detail how the technology was proven, both in the laboratory and at the rig, and how it is being used to design and complete wells in Alaska and Kazakhstan. Introduction The increased use of coiled tubing in the last twenty years has led to many technological advances in through-tubing workover operations such as fishing, impact services, milling, underreaming and hydromechanical pipe cutting systems. Because these operations are often performed to solve unforeseen problems, traditionally they have not been planned for during the completion design phase. As a result, challenges and restrictions placed on through-tubing tools and equipment can complicate through-tubing workover operations and add to their cost. Although the "cut-to-retrieve" feature of the removable packer may still be considered a contingency application, the due consideration and planning afforded the hydromechanical pipe cutting system at the completion design stage has effectively repositioned this through-tubing workover application from an "afterthought" to an extremely reliable and effective enabling technology. Removable Packer The removable packer was developed to offer large inside diameter, high performance and design simplicity missing from retrievable packers. The removable packer is retrieved by cutting the packer mandrel and picking up on the tubing. The packer and its tailpipe can then be removed from the well without the need to mill over the packer. (It should be noted, however, that since the mandrel is cut, redressing and re-running the packer will, in all likelihood, be uneconomical.) The cut-to-remove concept is based on the premise that the cross-section of the packer's cut zone is similar to that of the production tubing. Thus, existing through-tubing cutting technology can be used to cut the mandrel of the removable packer. The primary challenges were to establish a method of locating the cut region and optimizing the original hydromechanical pipe cutter design for this application. Existing location methods were established and are described in this paper. Optimizing the cutter design included controlling the depth of the cut, which was deemed a critical issue. If the cutter severs the mandrel and the outer housing, the removable packer will not be capable of removing the lower half of the packer and the tailpipe. (Figure 1) For the removable packer concept to be viable, operators requested multiple retrieving scenarios. Four were developed:Coiled-tubing conveyed hydromechanical cutterWorkstring-conveyed hydromechanical cutterStandard milling methodChemical cut method All four systems were designed and validated for use. (Figure 2)
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