Abstract A surface controlled subsurface safety valve is positioned in a well production tubing and an adjustable choke is installed in the surface production tubing. The safety valve is operated by the absolute pressure of the production fluids in the well tubing. The adjustable choke is controlled by a timer which periodically cycles the choke to reduce the flow area available for production of well fluids for a predetermined short period of time. The reduction in flow area causes a corresponding build up of pressure in the surface tubing which is transmitted down the well tubing to the subsurface valve. Biasing means urges the valve to its closed position while tubing pressure urges the valve to its open positions. During normal well flowing conditions the force of the tubing pressure is less than the force of the biasing means and the valve, while remaining fully open is moved by the biasing means towards its closed position. Such movement is retarded by a dash pot arrangement in the valve. Means are provided in the valve to bypass the dash pot and cause rapid closure of the valve when the valve has reached a predetermined point towards its closed position. Under normal operations before the valve reaches the point of rapid closure the tubing pressure force at the valve is increased substantially over the force of the biasing means and the valve is moved rapidly to its initial open position. The increase in tubing pressure at the valve results from reducing the flow area by means of the adjustable choke in the surface tubing.
A method for operating a subsurface safety valve used in closing off flow of well fluids through a well tubing comprising the steps of: periodically reducing momentarily at the surface the flow of fluids from a well tubing to cause a pressure pulse to travel down the well tubing from the surface to the subsurface valve; said pressure pulse causing a flow tube component of said valve to move from a third position in which said valve is fully open to an initial second position in which said valve is also fully open; said flow tube moving under normal operating well fluid pressures from its initial second position towards said third position thereof; and said flow tube moving to its first position in which said valve is closed from its third position thereof under normal operating well pressures.
Claim 2
Independent Claim
138 words
A method for operating a subsurface safety valve used in closing off flow of well fluids through a well tubing comprising the steps of: periodically reducing momentarily at the surface the flow of fluids from a well tubing to cause a pressure pulse to travel down the well tubing from the surface to the subsurface valve; said pressure pulse causing a flow tube component of said valve to move from a third position in which said valve is fully open to an initial second position in which said valve is also fully open; said flow tube moving under normal operating well fluid pressures from its initial second position towards said third position thereof; and said flow tube moving to its first position in which said valve is closed from its third position thereof under normal operating well pressures.
Claim 3
Dependent Claim
42 words
A method as recited in claim 1 in which said flow tube moves slowly from its second position to its third position and rapidly from its third position to its first position and rapidly from its third position to its second position.