GB1442563A - Removable subsea production test valve assembly - Google Patents

Abstract

1442563 Wells etc BAKER OIL TOOLS INC 17 Aug 1974 34755/74 Heading E1F A valve assembly A adapted to be lowered on a tubular string J into position within a blowout preventer stack D at the upper end of a well bore G, includes a housing structure 14 having a valve member which is moved to open position in response to an increase in pressure in a fluid control line 64 and which is automatically closed upon decrease in pressure in the line 64. The housing 14 is connected to the string J by latch means 15 which are held locked by fluid pressure in line 64 and which are unlocked by fluid pressure in line 38, thus permitting the string J to be raised leaving the valve assembly 14 (in closed condition) in the B.O.P. stack D. As described the upper part of latch means 15 is releasably secured to the lower half of latch means 15 by threads 35 (Fig. 3b) on latch fingers 33 (secured to the upper half) engaging threads 36 on the lower half of the latch means. The latch means 15 is locked by raising a locking piston 50, an upper portion 51 of piston 50 engaging the fingers 33 to hold them in engagement with threads 36. The locking piston 50 is biassed upwardly by sping 55 and is locked in its uppermost position as shown in Fig. 3b by applying fluid pressure below piston head portion 52 from control line 64 via passage 63 and port 65. The locking piston 50 can be moved downwardly to unlock the latch means by applying fluid pressure from control line 38 via passage 40 and port 53. In the event of a loss of fluid pressure in the control line 38 the latch means 15 can be released by rotating the string J to break shear pins 190 thus allowing the latch fingers 33 to be unscrewed from the threads 36. The valve assembly 14 includes two ball valve members 97 (only one shown, Fig. 3d, the two being identical). Each ball valve 97 can be moved downwardly by a piston 92, a pin 146 engaging a slot in the ball valve 97 so that during downward movement the ball 97 is rotated from its closed position, as shown, to its open position. The ball 97 is raised and thus closed by a spring 110. The piston 92 is of the differential type, areas S and R being subjected to the pressure in control line 64 via passage 63, poppet valve 78, Fig. 3c (which closes when the drill string is raised), passage 88, and passage 103 in the piston 92. The hydrostatic head of pressure in the control line 64 is balanced by the hydrostatic head of pressure outside the valve housing by means of a diaphragm 165 Fig. 3c) and fluid filled passages 175, 177 and 179. Thus the piston 92 is only moved downwardly by an increase in pressure in control line 64, this pressure acting over effective area T. When the pressure in line 64 decreases the piston is raised by spring 110. Since both the valve opening piston 92 and the latch looking piston 50 are actuated by fluid pressure in line 64 the latch cannot be released with the valve open. In use the valve assembly A is lowered into B.O.P. stack D and one B.O.P. D-1 is closed as shown in Fig. 1. The latch 15 can then be released and the string J raised thus leaving the valve assemlbly 14, in closed condition, in the B.O.P. stack D. A blind B.O.P. D-2 can then be closed to completely close off the stack above the valve assembly. For Figures see next page