| US 7,392,849 B2 | ||
| Balance line safety valve with tubing pressure assist | ||
| Donald Powell Lauderdale, Cypress, Tex. (US); Roddie R. Smith, Cypress, Tex. (US); and Richard Gledhill, Houston, Tex. (US) | ||
| Assigned to Weatherford/Lamb, Inc., Houston, Tex. (US) | ||
| Filed on Mar. 01, 2005, as Appl. No. 11/69,781. | ||
| Prior Publication US 2006/0196669 A1, Sep. 07, 2006 | ||
| Int. Cl. E21B 34/10 (2006.01) | ||
| U.S. Cl. 166—375 [166/386; 166/324; 166/332.8] | 20 Claims |
| 1. A subsurface safety valve, comprising:
a flow tube having a bore therethrough;
a control piston having two sides isolated from each other by a seal assembly and coupled to the flow tube; and
a balance piston having two sides isolated from each other by a seal assembly and selectively coupled to the flow tube,
wherein:
the valve is configured so that the control piston will receive a control pressure on the first side and the balance piston
will receive a hydrostatic pressure on the second side, and
the flow tube is actuatable between a first position and a second position and the balance piston is selectively coupled to
the flow tube so that the balance piston may urge the flow tube towards the second position but not towards the first position.
|