Challenge

• Provide a well isolation lubricator valve that exhibits excellent tolerance to well flow and produced debris

Solution

• En-Ter, a flapper valve that provides both well isolation and system integrity testing capability..

Benefits

• Large bore valve for deployment in marine riser or completion casing environments that offers bi-directional pressure support with improved performance and reliability in high well flow and tolerance to produced debris.

Technology Compromise

• Generally flapper valves have been the primary choice for well isolation and safety devices used in well completions, primarily due to providing superior sealing and operating integrity over comparable ball valves.
• Despite ball valves providing neither the sealing or operating integrity associated with flapper valves, they historically have been selected in well intervention systems as lubricator valves to provide increased lubricator section to allow the accommodation of long intervention strings where a requirement to not only provide well isolation capability but also to provide a bi-directional pressure support that permits the intervention system integrity to be tested prior to exposure to well fluids.

Solution

• The En-Ter flapper valve was conceived to address the problems associated with the inferior operating and sealing performance of ball valves, particularly as a lubricator valve in wells with high flow rates.
• When deployed as a Lubricator Valve within a marine drilling riser the slim external envelope of the valve allows a large umbilical to safely pass for control of the landing string valves and completion equipment located further down the intervention system.

Development

• The development of the En-Ter concept was conducted in stages with an initial sponsored design study to establish the optimum operating parameters for a well intervention valve followed by a detail design to refine the concept and identify the optimum mechanism to provide the high operating and sealing integrity. The final phase involved the manufacture of a prototype valve to prove the concept and complete qualification testing to recognised industry standards for operating and reliability.
• Following successful qualification testing the En-Ter technology has been incorporated into several well intervention systems as a lubricator valve, providing either production or annulus access through the intervention system.

Operating Detail

• The En-Ter valve utilises dual independent valve actuation mandrels with the upper mandrel replicating the functions of a conventional flapper valve which when actuated downwards by means of control line pressure pushes the flapper out against its closed biased spring to hold the valve in the open position and allow well bore access. Upward movement of the actuating mandrel allows the spring assisted flapper to close and isolate the well bore.
• An additional lower actuation mandrel in the En-Ter valve, which under application of control line pressure is forced against the underside of the flapper energising the contact between flapper and seat. The opening forces created by a pressure differential from above during a system pressure test, are overcome by the continued application of control line pressure to affect a seal from above. This on demand pressure support function allows the valve to operate as a conventional flapper valve to permit the passage of fluid from above for equalization or pumping operations.
• The independent upper and lower mandrel operations are sequenced through hydraulic control logic, where the hydraulic ports are routed via popper valves which prevent inadvertent operation of either mandrel that could damage the flapper assembly.

Applications

• The En-Ter can be configured in fail open, fail close or fail as is operating modes in a wide variety of sizes and pressure ratings as a completion intervention valve that allows the upper riser or completion to be used as a lubricator for the safe introduction of wireline or coil tubing well intervention tooling into the well bore.