ABSTRACT:

We are beginning a new era for surface controlled subsurface safety valves (SCSSVs) in deepwater applications throughout the world. Upcoming projects will require large diameter subsurface safety valves to be set at record setting depths while enduring HP/HT environments. Not only must the valve address these requirements; many times, it must be able to overcome the obstacles of a subsea completion. Generally, as the fail-safe setting depth for a subsurface safety system increases for deepwater applications, so does the operating pressure. The increase in operating pressure may have significant cost implications, depending on whether a wet (subsea) or dry (surface piercing) tree is used to complete the well. The adverse effect this pressure can have on the subsystems of a wet tree (i.e., control system, umbilical, and tree and wellhead ratings) that support the subsurface safety system will play a vital role in the methodology for selecting a subsurface safety system. A discussion is presented of how completion design dictates safety system selection, with emphasis on the comparison and contrast of such aspects as ultra-deepset conventional valves and tubing-pressure-insensitive, dome-charged or balance line valves. New technologies required to increase reliability for these applications will also be evaluated. Finally, based on these considerations, a detailed methodology is presented for selecting the most effective safety system for various given completion scenarios

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