Abstract: Described is a cable rejuvenation apparatus for a cable used in a subsea environment. The apparatus applies a bias signal to a conducting element of the cable, the bias signal being selected to improve the insulation properties of the cable. The bias signal is generated by a bias signal generator that includes a voltage source that generates a bias voltage having a time varying component. The bias voltage promotes an electrochemical reaction between the conducting element and the salt containing liquid of the subsea environment resulting in the formation of a barrier material at the fault location restricting further leakage current flow and enhancing the insulation resistance of the cable. The bias signal is a voltage selected such that the electrochemical reaction promoted by the bias voltage maintains the presence of the barrier material at the fault location.

Abstract: Described is a cable rejuvenation apparatus for a cable used in a subsea environment. The apparatus applies a bias signal to a conducting element of the cable, the bias signal being selected to improve the insulation properties of the cable. The bias signal is generated by a bias signal generator. The bias signal can be a voltage which promotes an electrochemical reaction between the conducting element and the salt containing liquid of the subsea environment resulting in the formation of a barrier material at the fault location restricting further leakage current flow and enhancing the insulation resistance of the cable. The bias signal is selected such that the electrochemical reaction promoted by the bias signal maintains the presence of the barrier material at the fault location.

Abstract: Described is a rejuvenation method for a cable used in a subsea environment. The method includes applying a bias signal to a conducting element of the cable, the bias signal being selected to improve the insulation properties of the cable. The bias signal is selected such that, in the event of an electrical leakage current of predetermined magnitude flowing between the conducting element and a salt containing liquid of the subsea environment at a fault location. The bias signal can be a voltage which promotes an electrochemical reaction between the conducting element and the liquid resulting in the formation of a barrier material at the fault location restricting further leakage current flow and enhancing the insulation resistance of the cable. The bias signal is selected such that the electrochemical reaction promoted by the bias signal maintains the presence of the barrier material at the fault location.

Abstract: A rejuvenation method for a cable used in a subsea environment, the method comprising applying a bias signal to a conducting element 2a, 2b of the cable 2, the bias signal being selected to improve the insulation properties of the cable 2.

Abstract: Apparatus for surface control of a sub-surface safety valve set within the production tubing of a drilling well, the apparatus comprising a hydraulic actuator for opening the sub-surface safety valve, a control line for supplying hydraulic control fluid to the actuator, a first control valve for controlling the supply of hydraulic fluid to the control line, a non-return valve in the control line path, between the actuator and the control valve, for preventing any contaminants entering the hydraulic fluid at the actuator from reaching the first control valve by migration up the control line, and an exhaust line connected to the actuator and control line and an associated second control valve enabling flushing of fluid from the actuator and control line.

Abstract: An apparatus for sensing strain applied to a region of a hydrocarbon well comprises an optical fiber in communication with the region. The optical fiber is responsive to strain applied to the region and to a light signal transmitted through it, in order to produce a sensing light signal incorporating scattered light. A characteristic of the scattered light is indicative of the strain being applied to the region.