The how and why of downhole safety valves
Downhole safety valves are designed to prevent the uncontrolled production of oil or gas from a well, in the event of damage to the Christmas tree or flow lines, or failure of surface control equipment. The first downhole safety valves were fairly simple devices invented primarily to protect caisson-type completions offshore from blowing out as a result of a collision on the surface. Caisson completions were vulnerable to damage because the wellhead was protected only by some pilings-frequently wood-driven into the ocean floow in shallow waters. The wells were drilled from submersible barges, usually, in near shore or inland waters. There was justified concern collisions could occur, with workboats or sports-fishing boats, to the extent that well control would be lost. Another concern was severe weather which could damage caisson-type completions-and platforms-to allow uncontrolled flow from wells. One of the manufacturers registered the name Storm Choke for its product, a name that has almost become generic, although still under legal protection. Early models of subsurface safety valves worked on the velocity principle. If flow through the tubing exceeded a fixed maximum, the valve would close. At that time, the maximum was established at something higher than the well's allowable producing rate. Since allowables are no longer effective, the maximum is fixed by the well's characteristics relative to reservoir damage, sand production, or water coning. The reasons subsurface safety valves are used remain the same, but today's designs are high-tech, many can be controlled from the surface, testing is fairly simple, and platform wells can be shut in individually or all at one time.
- OSTI ID:
- 5847931
- Journal Information:
- Pet. Eng. Int.; (United States), Vol. 58:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
NATURAL GAS WELLS
VALVES
OIL WELLS
DESIGN
OPERATION
BARGES
BLOWOUT PREVENTERS
DAMAGE
FAILURES
FOUNDATIONS
SAFETY
SAFETY ENGINEERING
WELLHEADS
CONTROL EQUIPMENT
ENGINEERING
EQUIPMENT
FLOW REGULATORS
MECHANICAL STRUCTURES
SUPPORTS
WELLS
020300* - Petroleum- Drilling & Production
030300 - Natural Gas- Drilling
Production
& Processing