Accumulator apparatus, system and method

A pressure accumulator apparatus for use in offshore drilling and production, comprising:

• a pressure vessel having an upper cylindrical compartment and a lower cylindrical compartment;
• a cylinder block for partitioning the pressure vessel into the upper cylindrical compartment and the lower cylindrical compartment;
• a means for admitting seawater at ambient pressure into a portion of the upper cylindrical compartment of the pressure vessel;
• a means for controlling an amount of hydraulic fluid ejected from a portion of the lower cylindrical compartment of the pressure vessel, wherein the ejected hydraulic fluid is delivered to a blowout preventer actuator chamber;
• an upper piston member circumscribed by an interior wall of the upper cylindrical compartment of the pressure vessel, said upper piston member being capable of sliding within the upper cylindrical compartment of the pressure vessel;
• a lower piston member circumscribed by an interior wall of the lower cylindrical compartment of the pressure vessel, said lower piston member being capable of sliding within the lower cylindrical compartment of the pressure vessel;
• a piston rod for connecting the upper piston member and the lower piston member, said piston rod capable of sliding through a bore in the cylinder block;
• and
• a volume of precharge gas stored in a second portion of the lower cylindrical compartment.

A system for delivering pressurized hydraulic fluid to a blowout preventer for use in offshore drilling and production comprising:

• a plurality of dual piston pressure accumulators;
• a means for serially connecting hydraulic fluid volumes of the dual piston accumulators;
• and
• a structure on which to mount the plurality of dual piston pressure accumulators.

A method of pressurizing hydraulic fluid in a dual piston pressure accumulator for use in offshore drilling and production comprising the steps of:

• drawing a vacuum in the volume of a first portion of a first compartment of a pressure vessel, said first portion being adjacent to a first side of a first piston circumscribed by the first compartment of the pressure vessel;
• injecting a gas to pressurize, to a specified pressure, the volume of a first portion of a second compartment of the pressure vessel, said first portion being adjacent to a first side of a second piston circumscribed by the second compartment of the pressure vessel;
• filling with hydraulic fluid a second portion of the second compartment of the pressure vessel, said second portion being adjacent to a second side of the second piston;
• admitting ambient fluid into a second portion of the first compartment of the pressure vessel, said second portion being adjacent to a second side of the first piston;
• and
• wherein the second piston is connected in tension to the first piston.

A method of controlling the pressure of hydraulic fluid comprising the steps of:

• drawing a vacuum in the volume of a first portion of a first compartment of a pressure vessel, said fist portion being above a first piston circumscribed by the first compartment of the pressure vessel;
• injecting a gas to pressurize, to a specified pressure, the volume of a first portion of a second compartment of the pressure vessel, said first portion being beneath a second piston circumscribed by the second compartment of the pressure vessel, wherein the second piston is connected to the first piston by means of a piston rod;
• filling with hydraulic fluid a second portion of the second compartment of the pressure vessel, said second portion being above the second piston;
• and
• immersing the pressure vessel into a fluid;
• admitting ambient fluid into a second portion of the first compartment of the pressure vessel, said second portion being beneath the first piston;
• transferring the ambient fluid pressure from the first piston over the piston rod to the second piston;
• applying the ambient fluid pressure from the piston rod to the second piston;
• imparting the load from the second piston to the hydraulic fluid contained in the volume of the second portion of the second compartment of the pressure vessel;
• and
• wherein the piston rod is in tension.