Abstract
Bottomhole assemblies (BHAs) are becoming much longer to carry equipment to the bottom of the hole. In many instances, these BHAs can be many hundreds of feet in length and may need to be passed into a live well. Under traditional conditions, a top-side lubricator is used and mounted directly to the wellhead to contain well pressure as tools are run into the hole. However, with today's longer-length BHAs, it becomes impossible to provide a lubricator with enough length to place on top of the wellhead to run tools.
As a result of the more common use of extremely long BHAs, a solution is desired to provide a barrier valve that is resident in the tubing string that allows the section of tubing between it and the wellhead to act as the lubricator. This barrier valve must be bidirectional in sealing capability to hold pressure from both above and below the valve.
This paper discusses a new barrier valve that can be used as a lubricator valve and has a unique closure mechanism that allows it to seal pressures of 10,000 psi and potentially higher, from both above and below. It is operated hydraulically from the surface via dual control lines with one port used to manipulate the valve into the open position and the other port to manipulate it to the closed position. In this scenario, the valve control system is neutrally balanced and pressure only needs to be applied during shifting of the valve to the appropriate position. In addition, the valve control system is tubing-pressure-insensitive, which allows for extremely low shifting pressures that are typically well below tubing pressure.
This paper presents the design considerations for such a valve. Test results will demonstrate the capabilities of this new valve with respect to high-pressure sealability across the closure mechanism combined with extremely low operating pressures required for valve control.
