Compact Hydropneumatic Heave Compensator

A hydropneumatic heave compensator and a semi-active control are proposed according to the requirements of offshore drilling at a depth of 6 km. This semi-active control is used to compensate mass changes in the system, to reduce the accumulator volume and improve the passive compensator performance. In this control, the system damping is modified at each instant of time through changes in the servo valve position, which is the only manipulated variable, and facilitates the low energy consumption of the compensator. The compensator with semi-active control has a satisfactory frequency response for each drill string mass and an accumulator volume comparable with the accumulator volume of the active compensators that are currently used in the offshore industry.