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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)

In coiled tubing conveyed through-tubing fishing operations, conventional jarring technology often creates limitations due to the requirement to repeatedly cycle the coiled tubing over the gooseneck in order to actuate and re-cock the jar. It is well known and documented in our industry that this repeated cycling leads to pipe fatigue and coiled tubing life reduction. Additionally, the low frequency, high-impact of the jarring assembly, may in some cases cause the fish to become wedged tighter. Vibratory and high frequency impact tools have been found to provide operational and economic benefits over hydraulic, time delayed jarring tools in a variety of through tubing fishing and workover applications, particularly in horizontal and extended-reach wells. As opposed to jars, vibratory type impact systems are capable of delivering significant impact forces at the fish with only limited set-down weight or over pull available making them particularly well suited to the constraints of coiled tubing operations. These hydraulically powered systems are configured to deliver downward impacts in compression and upward impacts in tension. Both downward and upward impacts are achieved without the necessity to cycle the coiled tubing between impacts, therefore significantly reducing low-cycle pipe fatigue. Additionally, when a fish is stuck in sand or debris, temporarily suspending or liquefying sand particles by lighter high frequency blows as delivered by an impact tool while over pull is applied offers a higher degree of success in freeing the fish. This paper will outline the uses and advantages of down-hole high-frequency vibration technology from a coiled tubing perspective and also describe the development and laboratory testing results of a new, modular vibratory impact tool offering a significantly reduced operating length yet delivering greater impact thus increasing the operating envelope for such tools adding demonstrable value to a variety of coiled tubing fishing and workover operations. Introduction It is well known that coiled tubing generates greater force pulling rather than pushing. If the coiled tubing does not generate enough force (either up or down), force assisting tools can be included in the workstring. In today's horizontal and extended reach wells, conventional jarring assemblies are not always an option for retrieving or shifting downhole devices on coiled tubing. Contrary to jars, vibratory and high-frequency impact tools are capable of significant impact forces with limited set down weight or overpull available. High frequency impact tools have been used in the industry for quite some time now, providing operational and economical benefits. For the purposes of this paper "frequency" is discussed as a relative term. Low frequency is used to describe approximately 1 to 2 blows per minute and high frequency describes approximately 1200 to 3600 blows per minute, equal to 20 to 60 blows per second (Hz). When running jars on coiled tubing, the pipe has to be cycled over the gooseneck multiple times to fire and re-cock the jar, whether in the up or down mode. Repeatedly cycling the coiled tubing can result in fatigue of the pipe section that is traveling up and down over the gooseneck. This can often be a limiting factor in the fishing job. In some cases, the low-frequency, high impact blows of a jarring tool can also be a limitation. A sand stuck fish is often wedged tighter after the combination of hard jarring with small particles. If the sand particles are temporarily suspended or liquified by lighter, high frequency blows while overpull is applied, there is a much greater chance of freeing the fish. The high-frequency impact tool can deliver both upward and downward impacts without cycling the coiled tubing.[1] Vibratory and high-frequency impact tools are typically used for shifting sliding sleeves, fishing, swaging collapsed tubing, breaking knock-out isolation valve discs and setting and retrieving wireline tools in deviated wells. Some high-frequency impact tool designs include a rotational option in the down mode for "impact drilling" applications. The most common applications of the impact drill include scale milling, hard-cement milling, resin-sand removal and gravel removal.

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