초록 ▼

An embodiment of a method for limiting the probability of failure on demand of a subsea test tree (“SSTT”) includes the steps of providing a safety shut-in system for actuating a safety valve of the SSTT, the safety shut-in system including a surface control station positioned above a water surface

An embodiment of a method for limiting the probability of failure on demand of a subsea test tree (“SSTT”) includes the steps of providing a safety shut-in system for actuating a safety valve of the SSTT, the safety shut-in system including a surface control station positioned above a water surface connected via an umbilical to a subsea control system positioned below the water surface to actuate the safety valve; and diagnostically testing the safety shut-in system without actuating the safety valve.

대표청구항 ▼

1. A method for limiting the probability of failure on demand of a subsea test tree (“SSTT”), comprising: utilizing a safety shut-in system comprising a surface control station positioned above a water surface and connected via an umbilical to a subsea control system positioned below the water surfa

1. A method for limiting the probability of failure on demand of a subsea test tree (“SSTT”), comprising: utilizing a safety shut-in system comprising a surface control station positioned above a water surface and connected via an umbilical to a subsea control system positioned below the water surface and operationally connected to the SSTT to actuate a safety valve of the SSTT in response to a signal received from the surface control station;transmitting an electric current to the subsea control system that is insufficient to actuate the safety valve;calculating the implied impedance to the electric current; anddetermining if a fault mode of the SSTT has occurred. 2. The method of claim 1, wherein the subsea control system does not include a microprocessor. 3. The method of claim 1, comprising actuating the safety valve via DC actuation. 4. The method of claim 1, comprising maintaining the safety valve in an as-is position for a selected time delay upon electric failure of the safety shut-in system. 5. The method of claim 4, comprising actuating the safety valve to a safe state upon passage of the selected time delay. 6. The method of claim 4, wherein the subsea control system does not include a microprocessor. 7. The method of claim 4, comprising actuating the safety valve via DC actuation. 8. The method of claim 3, wherein the subsea control system does not include a microprocessor. 9. The method of claim 1, comprising demultiplexing the electric current below the water surface. 10. The method of claim 9, wherein the subsea control system comprises a diode steering circuit for the demultiplexing the electric current. 11. The method of claim 4, comprising demultiplexing the electric current below the water surface. 12. The method of claim 11, wherein the subsea control system comprises a diode steering circuit for the demultiplexing the electric current. 13. A method for limiting the probability of failure on demand of a subsea test tree (“SSTT”), comprising: utilizing a safety shut-in system comprising a surface control station positioned above a water surface and a subsea control system positioned below the water surface and operationally connected to the SSTT to actuate a safety valve of the SSTT in response to a signal from the surface control system;diagnostically testing the safety shut-in system without actuating the safety valve; andmaintaining the safety valve in an as-is position for a selected time delay upon electric failure of the safety shut-in system. 14. The method of claim 13, comprising actuating the safety valve to a safe state upon passage of the selected time delay. 15. The method of claim 13, wherein the subsea control system does not include a microprocessor. 16. The method of claim 13, comprising actuating the safety valve via DC actuation. 17. The method of claim 16, wherein the subsea control system does not include a microprocessor. 18. The method of claim 13, comprising demultiplexing the electric current below the water surface. 19. The method of claim 18, wherein the subsea control system comprises a diode steering circuit for the demultiplexing the electric current. 20. The method of claim 18, comprising actuating the safety valve to a safe state upon passage of the selected time delay.