Newest TFL Retrievable Safety Valves for Subsea Completions

Abstract

ABSTRACT Two new novel 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 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 novel 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 two subsea wells - one 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. IN1RODUCTION 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 valves; two new valves have been developed which help extend subsea completion technology. In 1977 a design team consisting of R&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 arc 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 new TFL completion equipment. This equipment was to be for a new below-the-mudline subsea completion 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 compatibility of the TFL completion and service equipment with the new system; but also in 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 which spoke well of the reliability of and confidence in the insert valve's operation and retrievability.