A Complete Subsea Wireline System
Abstract: This paper was prepared lor presentatiOn at Offshore Europe 87, Aberdeen, 8·11 September. 1987. /3~~ SPEPermissiOn to copy is restricted to an abstract ol not more than 300words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgement ol where and by whom the paper was presented. Publication elsewhere is usually granted upon request provided proper credit is made.
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Summary In 1987, an extensive wireline program was completed on two subsea wells in the Highlander field in the central North Sea with a subsea lubricator deployed from a drilling rig that was drilling and working over adjacent wells. Working on two wells concurrently is a way to reduce the operating costs of a subsea development significantly. Introduction An extensive wireline work program had been planned for Summer 1987 on the Highlander field. This field, located in Block 14120 in the central North Sea, consists of a subsea production template tied back to the Tartan platform located 8 miles away (Fig. 1). Undertaking wireline work on subsea wells is costly because it usually requires the use of a semisubmersible drilling rig and completion riser. The completion riser is latched onto the top of the subsea tree and connects the well to a surface tree located in the rig's derrick. This setup allows the use of conventional wireline equipment and a surface lubricator to enter the well. The need to find a more cost-effective way of wirelining in subsea wells led to the development of alternative approaches. One of the alternatives is subsea wireline, which uses a subsea lubricator system. This system allows a well to be entered with a lubricator mounted directly on top of the subsea tree. The wireline passes from the subsea lubricator through the open water to a winch passes from the subsea lubricator through the open water to a winch mounted on the surface. The subsea lubricator system can be deployed from a diving support vessel (DSV), which results in cost savings because DSV's historically are significantly cheaper to operate than semisubmersible drilling rigs. But because of the depressed rig rates prevailing in 1987, a subsea lubricator deployed from a DSV for the prevailing in 1987, a subsea lubricator deployed from a DSV for the Highlander field wireline program would have been more expensive than conventional wireline equipment from a drilling rig. As a result, we developed an alternative approach for subsea wireline operations that allowed the new subsea wireline technology to be used cost-effectively. It consisted of using a semisubmersible drilling rig to work on two wells concurrently. Simultaneous operations on two wells was achieved by the use of a subsea lubricator deployed through a second moonpool cut in the deck of the rig. Thus, while one well was being worked on with a conventional drilling or completion riser, an adjacent well was being worked on with subsea wireline (Fig. 2). In Sept./Oct. 1987, the subsea lubricator system was mobilized onto the semisubmersible drilling rig Benvrackie, and an extensive wireline program was undertaken while the rig was engaged in drilling or working over adjacent wells. In addition to wireline work being undertaken from the rig, the diving team, on board the rig to support the subsea operation, were inspecting and doing maintenance work on the template. Consequently, three operations were going on at the same time, allowing the cost of the rig and support services to be spread between several jobs. Significant cost savings resulted. Highlander Field The Highlander field is situated in 420 ft of water and consists of a 12-slot subsea template tied back to the Tartan platform. The field came on stream in 1985, when existing appraisal wells were completed and connected to the platform through two 8-in. pipelines. The template was installed adjacent to these satellite wells, which were then hooked up to the template. Three production wellsWells HS12, HS13, and HS14-and one water-injection wellWell HS15-make up the satellite wells. The first well on the template, Well H1, was drilled and completed in Summer 1987 (Fig. 3).
Summary In 1987, an extensive wireline program was completed on two subsea wells in the Highlander field in the central North Sea with a subsea lubricator deployed from a drilling rig that was drilling and working over adjacent wells. Working on two wells concurrently is a way to reduce the operating costs of a subsea development significantly. Introduction An extensive wireline work program had been planned for Summer 1987 on the Highlander field. This field, located in Block 14120 in the central North Sea, consists of a subsea production template tied back to the Tartan platform located 8 miles away (Fig. 1). Undertaking wireline work on subsea wells is costly because it usually requires the use of a semisubmersible drilling rig and completion riser. The completion riser is latched onto the top of the subsea tree and connects the well to a surface tree located in the rig's derrick. This setup allows the use of conventional wireline equipment and a surface lubricator to enter the well. The need to find a more cost-effective way of wirelining in subsea wells led to the development of alternative approaches. One of the alternatives is subsea wireline, which uses a subsea lubricator system. This system allows a well to be entered with a lubricator mounted directly on top of the subsea tree. The wireline passes from the subsea lubricator through the open water to a winch passes from the subsea lubricator through the open water to a winch mounted on the surface. The subsea lubricator system can be deployed from a diving support vessel (DSV), which results in cost savings because DSV's historically are significantly cheaper to operate than semisubmersible drilling rigs. But because of the depressed rig rates prevailing in 1987, a subsea lubricator deployed from a DSV for the prevailing in 1987, a subsea lubricator deployed from a DSV for the Highlander field wireline program would have been more expensive than conventional wireline equipment from a drilling rig. As a result, we developed an alternative approach for subsea wireline operations that allowed the new subsea wireline technology to be used cost-effectively. It consisted of using a semisubmersible drilling rig to work on two wells concurrently. Simultaneous operations on two wells was achieved by the use of a subsea lubricator deployed through a second moonpool cut in the deck of the rig. Thus, while one well was being worked on with a conventional drilling or completion riser, an adjacent well was being worked on with subsea wireline (Fig. 2). In Sept./Oct. 1987, the subsea lubricator system was mobilized onto the semisubmersible drilling rig Benvrackie, and an extensive wireline program was undertaken while the rig was engaged in drilling or working over adjacent wells. In addition to wireline work being undertaken from the rig, the diving team, on board the rig to support the subsea operation, were inspecting and doing maintenance work on the template. Consequently, three operations were going on at the same time, allowing the cost of the rig and support services to be spread between several jobs. Significant cost savings resulted. Highlander Field The Highlander field is situated in 420 ft of water and consists of a 12-slot subsea template tied back to the Tartan platform. The field came on stream in 1985, when existing appraisal wells were completed and connected to the platform through two 8-in. pipelines. The template was installed adjacent to these satellite wells, which were then hooked up to the template. Three production wellsWells HS12, HS13, and HS14-and one water-injection wellWell HS15-make up the satellite wells. The first well on the template, Well H1, was drilled and completed in Summer 1987 (Fig. 3).
Subsea completions have been on the rise in recent years due to the economics, extreme environments, the use of infrastructures (subsea tiebacks), and migration to water depths in excess of 1300-feet. In this paper, subsea slickline operations are performed on three cluster wells situated beneath the operator's semi-submersible floating production unit in Vietnam's offshore Dai Hung field. The services were needed for reservoir management, including installation and retrieval of memory gauges, performance of logging surveys, and to manipulate sliding sleeves that had been installed with the ultimate purpose of optimizing hydrocarbon recovery. A subsea wireline unit (capable of deploying slickline and electric line) was chosen to provide the services. This unit was selected because of its cost efficiency and capability to perform a fishing job without impacting platform space and weight restrictions on the floating production unit as would have been imposed by use of a drilling riser. This paper will provide the case history of these services, which were unique in that these were the first diverless subsea slickline jobs performed solely with remote-operated vehicle (ROV) support for manipulation or assistance. Slickline provided an effective solution for the operator's service requirement within the specified criteria. Because of the versatility of newly developed advanced systems, slickline equipment was able to meet the restrictions of weight and size on platforms to provide a more efficient alternative for services that traditionally require rig mobilization. As a result of the success of this operation, the operator is planning other subsea slickline services that will be performed without a drilling or jack-up rig. With the present economic climate of the oil-and-gas industry, the significant costs normally associated with heavy workover and drilling facilities have strengthened the need to find other ways to enhance cost efficiency in subsea workover scenarios. To support this trend, innovative methods that have expanded the scope of operations that can be performed on subsea wells without a drilling rig have now been introduced. As an example, plug and abandonment operations can be performed with subsea wireline intervention units and other coiled tubing and wireline intervention techniques rather than with a tensioned riser from an anchored drilling vessel or a jack-up rig. With the new methods, the deployment system for wireline and coiled tubing does not require special system modification—any standard wireline or coiled tubing unit can be used. These techniques will be discussed more fully in the paper.
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