Slickline Power Unit on Coiled Tubing Provides Innovative Solution for Setting a Nippleless Lock in a Multilateral Completion
Authors: Hall Jack , Wijngaards Ben M. 
Published: December 2007

The procedure most often used for drilling laterals from horizontal completions requires a retrievable bridge plug to be set in the casing. The bridge plug serves as the base for orienting and setting the whipstock used to mill the window in the casing so that the drilling of the lateral section can be initiated,

In recent years, monobore completions have allowed operators to drill lateral sections through the tubing. Using coiled tubing drilling technology, this procedure can often be performed without killing the well and without pulling the present completion. With this method, a horizontal lateral can be drilled with the well flowing, which allows efficient removal of the cuttings and minimizes formation permeability impairment.

If, however, the well completion has wireline nipples or sliding sleeves installed in the tubing, the operation becomes significantly more difficult. This is due to the limited selection of bridge plugs that can be passed freely through the restricted bores of the nipples or sleeves, and then, can be set securely in the casing. If the well has been drilled horizontally, bridge plugs that must be set and retrieved with wireline (either slickline or electric line) cannot be used as they cannot be run into horizontal sections of the wells. Further, retrievable bridge plugs run on tubing or drill pipe would require that the well be killed, the Christmas tree nippled down, and a blowout preventer (BOP) stack installed on the well, Since retrievable bridge plugs run on tubing and drill pipe are frequently hydraulically set, and tubing rotation may be required to release from the bridge plug, a rig or well pulling hoist to perform the workover would be needed. Thus, any economic advantage of performing the workover operation with coiled tubing would be lost.

For these reasons, the retrievable bridge plug most commonly used when being set with coiled tubing is the inflatable bridge plug. This plug can be run through the most common restrictions in the tubing (nipples and circulating sleeves) and the element inflated to create the seal against the casing wall, The primary drawback to inflatable bridge plugs is their relatively low differential pressure ratings when compared to other retrievable bridge plugs. If, due to casing damage or other well conditions, the inflatable bridge plug cannot be set, the operator may be left with few viable options for completing the drilling program. This paper will discuss such a case, In this scenario, repeated attempts to set an inflatable bridge plug failed during the operator's drilling program, and a slickline running tool and nippleless lock mandrel were adapted for use with coiled tubing to provide a solution. Use of the slickline running tool with coiled tubing string had never before been attempted. How the adaptation variables were addressed and the considerations for running the nippleless lock on the coiled tubing string will be the focus of the paper.

In addition to providing an innovative solution for a difficult service problem, combing these technologies will undoubtedly offer viable alternatives for other service needs.

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