Motion compensator system and method

A motion compensator system for use on a floating vessel, comprising:

• a compensator cylinder assembly including three or more compensator cylinders each including a compensator cylinder body, a compensator piston slidingly disposed within the compensator cylinder body to define an upper chamber and a lower chamber, and a compensator rod slidingly disposed within the lower chamber with an upper end affixed to the compensator piston and a lower end extending beyond the compensator cylinder body;
• a guide cylinder assembly including three or more guide cylinders, wherein each guide cylinder includes a guide cylinder body and a guide rod slidingly disposed within the guide cylinder body, wherein a lower end of the guide rod extends beyond the guide cylinder body;
• an upper carriage affixed to an upper end of each compensator cylinder body and an upper end of each guide cylinder body, wherein the upper carriage includes two or more lift eyes each having a central aperture;
• a fastener assembly secured to one of the lift eyes and aligned with the central aperture, the fastener assembly including a pin bracket, a pin slidingly disposed within the pin bracket, a slide disposed within the pin bracket and secured to an inner end of the pin, wherein the pin is dimensioned to slide through the central apertures of the lift eyes, and wherein an outer end of the slide is disposed through a longitudinal slot in the pin bracket for controlling the position of the pin relative to the central apertures of the lift eyes;
• a lower carriage affixed to the lower end of each compensator rod and the lower end of each guide rod;
• and
• a safety shutoff assembly including a compensator manifold and three or more compensator valves, wherein each compensator valve is in fluid communication with a pressurized fluid source through the compensator manifold and in fluid communication with the lower chamber of one of the compensator cylinder bodies, wherein the safety shutoff assembly is configured to isolate a failed compensator cylinder by setting the compensator valve in fluid communication therewith to a vent setting.

A method of compensating for motion on a floating vessel, comprising the steps of:

• a) providing a motion compensator system comprising:
• a compensator cylinder assembly including three or more compensator cylinders each including a compensator cylinder body, a compensator piston slidingly disposed within the compensator cylinder body to define an upper chamber and a lower chamber, and a compensator rod slidingly disposed within the lower chamber with an upper end affixed to the compensator piston and a lower end extending beyond the compensator cylinder body;
• a guide cylinder assembly including three or more guide cylinders, wherein each guide cylinder includes a guide cylinder body and a guide rod slidingly disposed within the guide cylinder body, wherein a lower end of the guide rod extends beyond the guide cylinder body;
• an upper carriage affixed to an upper end of each compensator cylinder body and an upper end of each guide cylinder body;
• a lower carriage affixed to the lower end of each compensator rod and the lower end of each guide rod;
• and a safety shutoff assembly including a compensator manifold and three or more compensator valves, wherein each compensator valve is in fluid communication with a pressurized fluid source through the compensator manifold and in fluid communication with the lower chamber of one of the compensator cylinder bodies;
• b) suspending the motion compensator system from a suspension device on a floating vessel;
• c) securing a well tool to the lower carriage to suspend the well tool below the motion compensator system;
• d) when a distance between the floating vessel and a sea floor decreases, retracting the motion compensator system by setting the compensator valves to a feed setting to allow a fluid to flow from the pressurized fluid source into the lower chamber of each of the compensator cylinder bodies, thereby lifting the compensator piston, the compensator rod, the lower carriage, and the well tool relative to the upper carriage;
• e) when the distance between the floating vessel and the sea floor increases, extending the motion compensator system by setting the compensator valves to a vent setting in which the fluid in the lower chambers is vented to the atmosphere through a vent outlet of each of the compensator valves, thereby lowering the compensator piston, the compensator rod, the lower carriage, and the well tool relative to the upper carriage;
• f) monitoring a pressure within the lower chamber of each compensator cylinder body to detect a failure of the compensator cylinder body.