Actuation of a gun firing head

Method of firing a perforating gun which is suspended downhole in a borehole on the end of a tubing string, wherein the gun includes shaped charges which are connected to an initiator so that the initiator can be activated to detonate the charges, comprising the steps of:

• (1) elevating the tubing pressure to a first downhole pressure value;
• (2) moving a first member in response to the pressure value of step (1);
• (3) using the member movement of step (2) for closing a passageway which extends into a piston;
• (4) effecting the pressure value of step (1) on one side of the piston to cause the piston to move;
• (5) using the movement of the piston set forth in step (4) for activating the initiator and thereby detonating the charges of the gun.

Method of detonating a perforating gun located on a pipe string and positioned downhole in a borehole, comprising the steps of:

• (1) arranging the perforating gun in a manner to be detonated by an initiator;
• (2) placing a first and a second piston, respectively, in spaced relationship within a first and a second cylinder, respectively;
• (3) positioning the initiator, first and second pistons, first and second cylinders to form a first chamber between the initiator and the first piston, and to form a second chamber between the first piston and the second cylinder;
• (4) forming a passageway along the axial centerline of the first piston into which one end of the second piston can be sealingly received;
• (5) forming a flow path which extends from the interior of the tubing string, into the second cylinder, and into the second chamber when the second piston is sealingly reciprocated into the passageway of the first piston, thereby providing a means by which an increased pressure effected within the tubing string also effects a pressure differential across the first piston, thereby driving the first piston downwardly and exploding the initiator.

Method of perforating a highly deviated well comprising the steps of:

• suspending a perforating gun on a pipe string extending down into the highly deviated well;
• setting a packer disposed on the pipe string above the perforating gun;
• communicating a fluid flow path from the surface to a firing head adjacent the perforating gun;
• effecting a predetermined pressure through the flow path to the firing head;
• opening a valve in the flow path for fluid communication with one side of a movable member reciprocally disposed in a chamber in the firing head in response to the predetermined pressure;
• effecting the predetermined pressure on the one side of the movable member to cause the movable member to move;
• and
• using the movement of the movable member to actuate the perforating gun.

Method of testing a formation in a well comprising the steps of:

• mounting a first perforating gun and firing head on a pipe string;
• mounting a second perforating gun and firing head on the pipe string;
• running the pipe string into the well;
• setting a packer disposed on the pipe string above the first perforating gun;
• communicating the firing head of the first perforating gun with a fluid flow path to the surface;
• locating the first perforating gun adjacent a first formation to be tested;
• effecting a predetermined pressure through the flow path to the firing head of the first perforating gun;
• effecting the predetermined pressure on one side of a movable member reciprocably disposed in a chamber in the firing head of the first perforating gun to cause the movable member to move;
• using the movement of the movable member to actuate the first perforating gun and communicate the first formation with the wellbore;
• testing a parameter of the first formation;
• setting another packer to isolate the first formation from a second formation in the well;
• communicating the firing head of the second perforating gun with the fluid flow path to the surface;
• effecting another predetermined pressure greater than the first mentioned predetermined pressure through the flow path to the firing head of the second perforating gun;
• effecting the another predetermined pressure on one side of the movable member reciprocably disposed in a chamber in the firing head of the second perforating gun to cause the movable member to move;
• using the movement of the movable member to actuate the second perforating gun and communicate the second formation with the wellbore;
• and
• testing a parameter of the second formation.

Method of firing a perforating gun which is suspended within a well on a pipe string, comprising the steps of:

• communicating a flow path from the surface to a firing head adjacent the perforating gun;
• filling the flow path with a fluid;
• effecting a predetermined pressure through the flow path to the firing head;
• lowering a mass through the pipe string to close a passageway through a moveable wall reciprocably mounted in a chamber within the firing head and to open a valve in the flow path for fluid communication with one side of the movable wall in the chamber;
• effecting the predetermined pressure on the one side of the movable wall to cause the movable wall to move;
• and
• using the movement of the movable wall for detonating the charges of the perforating gun.