Method and apparatus for compressing a gas to a high pressure

A method of compressing a gas in a hydraulically driven reciprocating piston compressor that comprises a cylinder;

• a free floating piston disposed within said cylinder between a first closed end and a second closed end;
• a compression chamber defined by a volume within said cylinder between said first closed end and said piston;
• and a drive chamber defined by a volume within said cylinder between said second closed end and said piston;
• said method comprising:
• (a) in an intake stroke,
• supplying said gas to said compression chamber;
• removing said hydraulic fluid from said drive chamber, whereby said gas supplied to said compression chamber is at a higher pressure than said hydraulic fluid within said drive chamber, causing said piston to move to reduce the volume of said drive chamber and increase the volume of said compression chamber until said compression chamber has expanded to a desired volume and is filled with said gas;
• and
• (b) in a compression stroke,
• supplying said hydraulic fluid to said drive chamber whereby said hydraulic fluid within said drive chamber is at a higher pressure than said gas within said compression chamber, causing said piston to move to increase the volume of said drive chamber and reduce the volume of said compression chamber thereby increasing the pressure of said gas held within said compression chamber;
• discharging said gas from said compression chamber when the pressure of said gas is increased in a single cycle to a pressure of at least 2500 psi (17.2 MPa), which is at least five times greater than the pressure of the gas supplied to said compression chamber;
• employing a piston stroke length to piston diameter ratio of more than even to one;
• and
• dissipating heat from said cylinder during said compression stroke whereby said gas is discharged from said compression chamber with a temperature significantly less than isentropic.