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Two new retrievable ball type safety valves are now available in the TFL (pumpdown) configuration. These valves offer greater depths in a more simplified configuration to operators planning subsea completions. They were developed planning subsea completions. They were developed at the request of major producers for use in the North Sea and Southeast Asia.
Design of these new valves began in 1977 and early 1978 by engineers from Otis' Research and Development Department. One valve is a balance line valve with a fail-close leak protection feature. The other valve is a single line deep set valve which allows installation at greater depths than previously achieved. They have been successfully tested in test wells and test loops at the manufacturer and in two land test wells by the operators. The safety system packages for these valves are currently installed in six subsea wells - five in the North Sea and the other in the South China Sea.
The material presented in this paper shows how the capabilities of subsea production are expanded by the development of a truly fail safe balance line retrievable ball valve and a deep set single line ball valve which can be placed at or near the packer, below paraffin levels, or below the kickoff point.
As completion technology has kept pace with drilling technology in the push for oil into deeper waters and hostile environments, so too has pumpdown (TFL) completion and service technology kept pace with developments to give the industry viable alternatives in the completion of subsea installations. This holds particularly true for TFL retrievable ball safety particularly true for TFL retrievable ball safety valves; two new valves have been developed which help extend subsea completion technology.
In 1977 a design team consisting of R and D Engineers from Otis and engineers from a major North Sea producer met and established design criteria for a new subsea safety system. This system would consist of a tubing retrievable ball valve and a separate backup insert TFL ball valve both of which would be of the balanced type. The exact details of the design criteria for the tubing retrievable valve and the overall safety system are presented in detail in OTC Paper No. 4253 presented at the 1982 Offshore Technology Conference.
In early 1978 Otis was approached by a major producer from the Southeast Asia area regarding producer from the Southeast Asia area regarding new TFL completion equipment. This equipment was to be for a new below-the-mudline subsea completions and was part of an ongoing development program in which five TFL subsea completions had been made with an above the mudline wellhead configuration.
Discussions centered around the updating and compatability of the TFL completion and service equipment with the new system; but also in particular on the safety system. The safety particular on the safety system. The safety system would, as in the past, be a single line system. However for this completion it would consist of both a tubing retrievable valve and an insert valve. Five previous completions had consisted of only a landing nipple and TFL insert valve for the safety system which spoke well of the reliability of and confidence in the insert valve's operation and retrievability.
The previous single line insert valves were designed for approximately 500 ft. depth and were generally landed in depths of 200 - 300 ft. The requirements for the valve for this completion, however, would be a minimum of 1000 ft., if possible, while still maintaining the same maximum possible, while still maintaining the same maximum bore and other features the previous valves and control system compatability.
Victaulic has introduced the Series 727 ball valve, a high-pressure, enhanced-port valve with grooved ends for upstream oil applications. The internal design of the Series 727 valve has been streamlined to provide enhanced flow characteristics, offering improved throughput. Flow testing demonstrated up to one-third better flow than competitive standard-port ball valves. Featuring grooved ends, the Series 727 is joined using Victaulic couplings, enabling quicker and easier installation and maintenance than flanged valves. The Series 727 weighs one-third less than equivalent flanged valves, further easing handling and installation.
High Pressure Equipment’s (HiP) new locking device for its trunion-style ball valves ensures protection from unauthorized use and can be used on HiP valves with 0.187-in., 0.375-in., or 0.500-in. Designed for severe duty applications, the valves have an effective shutoff of liquid or gas flow through 20,000 psi at 350°F. The two-way ball valve can be shut off completely with a ¼-in. The three-way ball valve requires a ½-in. The valves are constructed with 316 stainless steel.
Medley, Edward L., Amoco (UK) Exploration Company
There are 92 surface operated, wireline retrievable sub-surface safety valves installed in Amoco (UK) Exploration Company's portions of the Leman, Indefatigable and portions of the Leman, Indefatigable and Rough Fields. These valves are fail-safe in operation and offer a back-up shut-in safety system to all other safety shutdown devices on a platform. Therefore, each valve is function tested monthly.
There are three types of valves in use in these fields, the bypass type, the ball type and the flapper type. Records covering an eight year period were reviewed to provide data to determine a failure rate provide data to determine a failure rate for each type of valve. Individual graphs were prepared showing each time a valve was pulled, and these were reviewed and summaries given to show how failure rates were determined.
Based on the review, the following failure rates were determined:
Type No. of No. of Failure Valve Tests Failures Rate
Bypass 3472 28 0.8%
Ball(old 595 68 11.4% type)
(new 172 4 2.3% type)
Flapper 1651 26 1.5%
Amoco has been producing gas from the southern North Sea since April 1969 and until July 1977, 101 development wells had been completed in the Leman, Indefatigable and Rough Fields. The fields produce from the Rotliegendes Sandstone from depths ranging from 6600' to 8500'. In these fields two completion schemes are used, one with 4 1/2" tubing, the other with 5 1/2" tubing. The 4 1/2" tubing was used in 36 wells on the first three platforms in the Leman Field, but all later completions used 5 1/2" tubing.
As part of the completion equipment, a surface operated, wireline retrievable, subsurface safety valve is set in the tubing, approximately 100' below the sea bed. These valves are referred to as mudline safety valves (MLSV). These are fail safe, since hydraulic pressure from the surface must be maintained to keep them open. A concentric tubing/casing annulus is used to transmit this hydraulic control pressure. Due to the type of operation and the location of these valves, they provide a back-up to all other safety shut-in devices on a platform. They will automatically close if any of the surface hydraulic control equipment is damaged, or if the Christmas tree is damaged, and due to their location within the well, they should be immune from any damage above the sea bed.
Each MMSV is function tested once per month. This test is conducted in the following manner:
1. With the well flowing, the hydraulic annulus pressure is bled off, causing the MLSV to close.