An oil or gas well is flow tested by acoustic transmission (68,70) and reception (102) devices for communicating preferably through at least 5,000 feet (1525m) of an annular column of substantially static fluid which is susceptible to gelling which further attenuates the acoustic signals. The apparatus comprises a tubing string (66) including a packer (92), a tester valve (76). an actuator (109) therefor, an acoustic receiver (102). an acoustic transmitter (68,70) and control means (110) responsive to the receiver (102) to control the actuator (109).

A control system especially but not exclusively for use downhole in a well bore during drill stem testing, includes first means (38) for producing a first response to a changing stimulus (eg. well bore pressure changing at a varying rate); second means (58) for producing a second response to the stimulus, which response is initially masked by the first response; and signal producing means (6) arranged to produce a signal when the second response exceeds the first response. In one embodiment, two components (38,58) are moved in different directions, but in a net first direction, until the rate of change of the pressure is sufficiently low (e.g. near steady state), at which time the rates of movement of the two components produce net movement in a second direction which initiates a control valve (6) to produce a signal.

A control system especially but not exclusively for use downhole in a well bore during drill stem testing, includes first means (38) for producing a first response to a changing stimulus (eg. well bore pressure changing at a varying rate); second means (58) for producing a second response to the stimulus, which response is initially masked by the first response; and signal producing means (6) arranged to produce a signal when the second response exceeds the first response. In one embodiment, two components (38,58) are moved in different directions, but in a net first direction, until the rate of change of the pressure is sufficiently low (e.g. near steady state), at which time the rates of movement of the two components produce net movement in a second direction which initiates a control valve (6) to produce a signal.

A sequential remote control plug release system allows actuation of plug release plungers (34,36) and manifold valves (38,40,42) associated with a cementing plug container (20), only in a predetermined sequence. The plug container has two plugs, and thus two plug release plungers, and three manifold valves, and the middle (40) and upper (42) manifold valves and the upper plug release plunger (36) can be opened and retracted only in a predetermined sequence. This is implemented through interconnected actuation valves and sequencing valves contained in a housing (22) which can be located remotely from the plug container.

A hydraulic system and method are provided for supplying high pressure hydraulic fluid to a cylinder for operating a ram, e.g a shearing and/or shut-off ram for a blowout preventer. It comprises means for supplying high pressure hydraulic fluid to the cylinder, said hydraulic fluid supply means comprising first (10) and second (11) storage means for storing hydraulic fluid under pressure, first conduit means (12) for supplying hydraulic fluid under pressure from said first storage means to the cylinder, a pressure sensing device (19) for determining the back pressure in said first conduit means, second conduit means (27) for supplying hydraulic fluid under pressure from said second storage means to the cylinder and valve means (25) for automatically opening said second conduit means when the back pressure in the first conduit means reaches a predetermined amount.

A system for verifying the effectiveness of electromagnetic signal control of a subsurface safety valve installed in a well. Signals are transmitted from a surface station to actuate the subsurface installed valve. Signals received at the valve are decoded and information relating to them is stored. A sensor detects actual valve actuation and provides signals indicative thereof which are also stored. After the valve is removed from its downhole installation, the stored signals are read, and the data indicated thereby is compared with data recorded at the time of signal transmission from the surface.

An overpressure device for applying pressure from a first hydraulic fluid to a second hydraulic fluid comprises:

• a housing (20) in which is located a piston (1),
• an opening (7) in the housing (20) for the entry of the first hydraulic fluid to one side of the piston (1),
• a second opening (12) in the housing (20) for the entry of the second hydraulic fluid to a chamber on the other side of the piston (1) whereby the pressure of the first hydraulic fluid is exerted on the second hydraulic fluid, and
• an additional means (5) of exerting pressure on the piston (1) so that pressure exerted on the second hydraulic fluid is greater than that of the first hydraulic fluid alone.

A hydraulic safety valve manifold system for providing positive opening and closing of a surface-controlled, sub-surface safety valve in a subsea well, including a shut-off valve which prevents leakage of well fluids to the outside environment if a leak should occur in the safety valve or in hydraulic lines which are connected to the hydraulic actuator of the safety valve. A hydraulic control line is connected to the safety valve actuator through a normally closed shut-off valve, and this line is also connected to the actuator of the shut-off valve to hold both the shut-off valve and the safety valve open when the line is pressurized. The hydraulic line is also connected to an actuator of a variable volume accumulator to empty the accumulator when the line is pressurized. When pressure in the hydraulic line is relieved the shut-off valve closes and the accumulator accepts fluid from the hydraulic actuator of the safety valve to insure that the safety valve closes.

Apparatus for the remote individual control of a plurality of hydraulically-actuated operators comprises first and second signal pressure lines (A, B) connected from a pressure source (37) to supply selected pressure signals to a plurality of AND-gates (G1-G25) each having its output connected to a-separate operator, and a pair of matrices (Vl-V5, V6-V10) of series-connected valvepairs connected between the respective signal pressure lines and the respective inputs of the AND-gates to select the appropriate pressure signals, for the applicator to be energised and apply them to the two inputs of the AND-gates associated with that applicator, each AND-gate when opened by said signals connecting the associated applicator to a source of pressure.

A device for use in a subterranean well. The device comprising an actuator sleeve (210) coupled to an actuated element (200) of the device to operate the actuated element when the actuator shifts axially in the device, and an actuator (220) comprising a spring (222) to act on the actuator sleeve (210). The actuator is responsive, independent of well annulus pressure, to a remotely generated hydraulic signal in a central bore (208) of the device to change from an unactuated state, with the spring compressed, to an actuated state, with the spring expanded to shift the actuator sleeve from a first position to a second position, and the actuator is responsive to reset to the unactuated state when the spring is recompressed.