Pressure switch for selective firing of perforating guns

A method for selectively firing a perforating gun train, comprising:

• forming the perforating gun train to include includes at least a first perforating gun and a second perforating gun,
• forming an electrical connection between the perforating gun train and a surface location using at least one switch, wherein the switch includes:
• a casing having a bore;
• a piston assembly having an outer circumferential surface, a first end and an exposed end, a plurality of flanges formed at the first end and projecting radially outward from the outer circumferential surface, a plurality of grooves formed at the exposed end and recessed radially from the outer circumferential surface;
• a contact assembly disposed in the bore;
• a pin disposed in the bore, the pin being slidable between a first position and a second position, wherein the pin electrically contacts the piston assembly and is electrically isolated from the contact assembly in the first position, and the pin is electrically isolated from the piston assembly and electrically engages the contact assembly in the second position, wherein the pin and piston assembly define a volume in the bore;
• a lubricant deposited in the bore, the lubricant forming a pressure transmitting body between the pin and the piston assembly as the pin slides from the first position to the second position, wherein the pressure transmitting body completely fills the volume defined by the pin and the piston assembly when the pin is in the second position;
• and
• a spring urging the pin into engagement with the piston assembly when the pin is in the first position;
• conveying the perforating gun train into a wellbore with the pin in the first position;
• firing the first perforating gun, the firing causing the pressure transmitting body to apply a pressure to move the pin to the second position;
• locking the pin with the contact assembly when the pin is in the second position using the lubricant, the lubricant completely filling the volume defined by the pin and the piston assembly;
• and
• firing the second gun.