Thermally-Actuated Gas Lift Safety Valve: Apparatus and Operational Procedure

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Thermally-Actuated Gas Lift Safety Valve
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Inventors
Professor Franz Hover
Department of Mechanical Engineering, MIT
External Link (oceans.mit.edu)
Eric Gilbertson
Department of Mechanical Engineering, MIT
Jose Arellano
Chevron Corporation
Eduarto Colina
Chevron Corporation
Bryan Freeman
Chevron Corporation
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Thermally-Actuated Gas Lift Safety Valve

US Patent 8,800,590
Publications
A Thermally Actuated Gas-Lift Safety Valve
SPE Production & Operations, Vol. 28, no.01 (2013): 77-84
Sharp Phase Change in Shape Memory Alloy Thermal Actuators for Subsea Flow Control
ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, Vol. 6, July 1–6, 2012, 309-315
Design of a Thermally-Actuated Gas Lift Safety Valve
ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering, Vol. 2, June 19–24, 2011, 675-684
Gas Lift Valve Failure Mode Analysis and the Design of a Thermally-actuated Positive-locking Safety Valve
DSpace@MIT, 2010

Applications

Gas lifting mechanisms are used to produce oil from wells where flow does not occur naturally. A primary application for this technology is in the  prevention of oil backflow during gas lift assisted oil extraction.

Problem Addressed

With current methods, there is a danger of oil passing from the tubing into the annulus (backflowing) when the reverse-flow check valve opens or has leaks. This occurs when, simultaneously, the reverse-flow check valve has a lead and the tubing pressure exceeds the gas pressure. The combination of high tubing pressure and low gas pressure allows the bellows valve to open, thus allowing for backflow. If this were to happen, the passage of product through the annulus can cause an undesirably high accumulation of hydrocarbons at the well and surface to occur, thus increasing the risk of injury to personnel and/or damage to equipment. This invention prevents product from entering the annulus by placing a thermally-actuated safety valve at the gas lift where gas is supposed to pass during well production. 

Technology

This invention proposes the design of a thermally-actuated gas lift safety valve that prevents oil backflow. In a backflow event, oil passes through the gas lift valve into the annulus because the oil is warmer than the injection gas. Before unloading begins, the thermally-actuated gas lift valve is at oil temperature and thus the safety valve is in the closed position. With the invention, the modified unloading process follows the normal unloading process, but with the subsurface safety flapper valve in the tubing initially closed. This allows for the normal unloading process to be unaffected by the thermal gas lift valve at this point because the safety valve is closed and it cannot pass gas. The new design uses shape memory alloys to close the valve in this event. If the check valve ever leaks and allows oil to pass through the thermal gas lift valve, the shape memory alloy wires will heat up and the ball valve located in the venturi orfice of the gas lift valve will close to prevent backflow.

Advantages

  • Prevents oil from entering the annulus
  • Tunable transition temperatures of the shape memory alloys to match well conditions
  • Invention and operational procedures work well with a safe level of hysteresis