Motion compensator

A motion compensator comprising:

• telescoping mandrel means including interconnected outer tubular housing means and inner sleeve means;
• tubular mandrel means disposed between said housing means and said sleeve means;
• a pressure balancing seal system including:
• first seal means between said telescoping mandrel means and said sleeve means, and
• second seal means between said telescoping mandrel means and said housing means;
• said first and second seal means in conjunction with said telescoping mandrel means and said tubular mandrel means defining an annular chamber;
• low pressure accumulator means adapted to contain lubricant;
• means conducting lubricant between said low pressure accumulator means and said chamber;
• an environmental seal system spaced from said pressure balancing seal system including seal means between said telescoping mandrel means and said housing means;
• said second seal means and said environmental seal system in conjunction with said housing means and tubular mandrel means defining an annular cavity;
• first port means through said housing means permitting injection of lubricant to said environmental seal system;
• and
• communicating means between said annular cavity and the bore of said sleeve means.

A motion compensator comprising:

• telescoping mandrel means including interconnected outer tubular housing means and inner sleeve means;
• tubular mandrel means disposed between said housing means and said sleeve means;
• a pressure balancing seal system including:
• first seal means between said tubular mandrel means and said sleeve means, and
• second seal means between said tubular mandrel means and said housing means;
• said first and second seal means in conjunction with said telescoping mandrel means and said tubular mandrel means defining a chamber including a reservoir;
• low pressure accumulator means disposed in said reservoir;
• an environmental system spaced from said pressure balancing seal system including seal means between said tubular mandrel means and said housing means;
• said second seal means and said environmental seal system in conjunction with said housing means and tubular mandrel means defining an annular cavity;
• first port means to permit conduction of lubricant to said environmental seal system;
• second port means to permit conduction of lubricant to said annular chamber between said accumulator means and said first seal system;
• and
• communicating means between said annular cavity and the bore of said sleeve means.

A motion compensator comprising:

• telescoping mandrel means including outer tubular housing means;
• tubular mandrel means disposed within said housing means;
• an environmental seal system including seal means between said tubular mandrel means and said housing means;
• port means through said housing means permitting lubricant to be injected to said environmental seal system and opening near said seal means;
• conduit means extending from the surface to said motion compensator and connected in communication with said port means;
• means for transmitting lubricant through said conduit means so that lubricant may flow through said port means and be injected to said environmental seal system during the operation of said motion compensator;
• and
• guage means adapted to monitor the pressure of injected lubricant.

A motion compensator comprising:

• telescoping mandrel means including interconnected outer tubular housing means and inner sleeve means;
• tubular mandrel means disposed between said housing means and said sleeve means;
• a seal system including:
• first seal means between said tubular mandrel means and said sleeve means;
• and
• second seal means between said tubular mandrel means and said housing means;
• port means through said housing means permitting injection of lubricant to a chamber defined by said first and second seal means, said telescoping mandrel means and tubular mandrel means;
• conduit means extending from the surface to said motion compensator and connected in communication with said port means,
• means for transmitting lubricant through said conduit means so that lubricant may flow through said port means and be injected to said seal system during the operation of said motion compensator;
• and
• guage means adapted to monitor the pressure of injected lubricant.

The method of operating a motion compensator said motion compensator including telescoping mandrel means having interconnected outer tubular housing means and inner sleeve means;

• tubular mandrel means disposed between said housing means and said sleeve means;
• first seal means between said tubular mandrel means and said sleeve means;
• second seal means between said tubular mandrel means and said housing means;
• and port means through said housing means permitting injection of lubricant to an annular chamber defined by said first and second seal means, said telescoping mandrel means and said tubular mandrel means;
• the method comprising the steps of:
• operating said motion compensator with both of said seal means subject to well fluids;
• injecting lubricant at a low pressure to said annular chamber;
• monitoring the pressure of injected lubricant;
• and
• registering a change of pressure when at least one of said seal means fails.

The method of operating a motion compensator, said motion compensator including tubular mandrel means, tubular housing means telescoped around said tubular mandrel means, a seal system including seal means between said tubular housing means and said tubular mandrel means, and port means through said housing means opening near said seal means;

• the method comprising the steps of:
• positioning the motion compensator within a well pipe string extending between a stationary underwater wellhead and a floating platform so that the motion compensator can accommodate oscillating movement of the floating platform with respect to the stationary underwater wellhead;
• and
• injecting lubricant through said port means during the operation of said motion compensator.