A method to manipulate a well, comprising: - (a) providing an apparatus (60a, 60b) comprising: - a container (68a, 68b) having a volume of at least 1 litre and at most 1600 I; - a port (61a, 61b, 473) to allow pressure and fluid communication between a portion of the container and a surrounding portion of the well; - a mechanical valve assembly having a valve member (62a, 62b', 62b", 477) adapted to move, to selectively allow or resist, directly or indirectly, fluid exit from at least a portion of the container, via the port; - a control mechanism (66a, 64a) to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; - (b) providing a fluid comprising a gas in at least a portion of the container, said portion having a volume of at least 1 I; - (c) pressurising the gas to a pressure of at least 68,95 x 10 5 PA (1000 psi) and maintaining it at said pressure for at least one minute; - (d) running the apparatus into the well, such that the apparatus is at least 100m below the surface of the well; then, - (e) isolating the port of apparatus from the surface of the well using at least one isolating component, the, or the uppermost, isolating component being at least 100m from the surface well; - (f) sending a control signal to the communication device at least in part by a wireless control signal transmitted in at least one of the following forms: electromagnetic, acoustic, inductively coupled tubulars and coded pressure pulsing; then, - (g) moving the valve member in response to said control signal to allow at least a portion of the fluid to be released from the container; and wherein (h) the container has a pressure of at least 68,95 x 10 4 Pa (100 psi) more than a surrounding portion of the well immediately before the valve member is moved in response to the control signal. - (a) providing an apparatus (60a, 60b) comprising: - a container (68a, 68b) having a volume of at least 1 litre and at most 1600 I; - a port (61a, 61b, 473) to allow pressure and fluid communication between a portion of the container and a surrounding portion of the well; - a mechanical valve assembly having a valve member (62a, 62b', 62b", 477) adapted to move, to selectively allow or resist, directly or indirectly, fluid exit from at least a portion of the container, via the port; - a control mechanism (66a, 64a) to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; - a container (68a, 68b) having a volume of at least 1 litre and at most 1600 I; - a port (61a, 61b, 473) to allow pressure and fluid communication between a portion of the container and a surrounding portion of the well; - a mechanical valve assembly having a valve member (62a, 62b', 62b", 477) adapted to move, to selectively allow or resist, directly or indirectly, fluid exit from at least a portion of the container, via the port; - a control mechanism (66a, 64a) to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; - (b) providing a fluid comprising a gas in at least a portion of the container, said portion having a volume of at least 1 I; - (c) pressurising the gas to a pressure of at least 68,95 x 10 5 PA (1000 psi) and maintaining it at said pressure for at least one minute; - (d) running the apparatus into the well, such that the apparatus is at least 100m below the surface of the well; then, - (e) isolating the port of apparatus from the surface of the well using at least one isolating component, the, or the uppermost, isolating component being at least 100m from the surface well; - (f) sending a control signal to the communication device at least in part by a wireless control signal transmitted in at least one of the following forms: electromagnetic, acoustic, inductively coupled tubulars and coded pressure pulsing; then, - (g) moving the valve member in response to said control signal to allow at least a portion of the fluid to be released from the container; and wherein (h) the container has a pressure of at least 68,95 x 10 4 Pa (100 psi) more than a surrounding portion of the well immediately before the valve member is moved in response to the control signal.