Method and Apparatus for Completing a Horizontal Well

A method of completing a well, comprising:

• (a) providing a firing head assembly comprising a sealed chamber containing a piston for movement along a firing head axis, a firing pin axially aligned with the piston, and an impact detonator axially aligned with the firing pin;
• (b) installing the firing head assembly within a sub and linking the impact detonator to a perforating charge;
• (c) securing the sub to a string of conduit and lowering the conduit into a wellbore;
• (d) lowering a drill bit into the conduit, pumping drilling fluid through the drill bit into the conduit and rotating the drill bit against the firing head assembly to disintegrate at least a portion of the sealed chamber, thereby exposing the sealed chamber to the fluid pressure of the drilling fluid in the conduit;
• and
• (e) in response to the fluid pressure, the piston driving the firing pin against the detonator, causing the perforating charge to detonate to create a perforation through the conduit, a portion of the cement and into an earth formation.

A method of performing a downhole operation on a well, comprising:

• (a) providing a firing head assembly comprising a sealed chamber containing a piston for downward movement, a firing pin below the piston, and an impact detonator below the firing pin;
• (b) installing the firing head assembly and a perforating charge within a sub;
• (c) securing the sub to a string of conduit and lowering the conduit into a wellbore;
• then
• (d) pumping cement down the conduit, through the sub around the firing head assembly, and out a lower end of the conduit into the wellbore;
• then
• (e) lowering a drill bit into the conduit, pumping drilling fluid through the drill bit into the conduit and rotating the drill bit against the firing head assembly to disintegrate at least a portion of the sealed chamber, thereby exposing the sealed chamber to the fluid pressure of the drilling fluid in the conduit;
• (f) in response to the fluid pressure, the piston driving the firing pin against the detonator, causing the perforating charge to detonate to create a displacement perforation through the conduit, a portion of the cement and into an earth formation;
• then
• (g) providing a logging tool with a pump-down head and lowering the logging tool on a wireline into the conduit and pumping fluid into the conduit above the pump-down head of the logging tool to pump the logging tool down the conduit, the downward movement of the pump-down head causing at least some fluid in the conduit below the pump-down head to flow out the displacement perforation into the earth formation, then retrieving the logging tool on the wireline;
• and
• (h) performing a well survey with the logging tool while the logging tool is in the conduit.

An apparatus for completing a well, comprising:

• a sub for connection into a string of conduit to be lowered into the well;
• a support within the sub for holding a perforating charge;
• a firing head assembly mounted in the sub and comprising:
• a housing having a chamber;
• a piston located in the chamber for downward movement;
• a firing pin below the piston for delivering a blow to an impact detonator below the firing pin within the housing;
• and wherein
• an end of the housing is constructed of a drillable material, so that a drill bit when lowered into the conduit and rotated against the end of the housing, exposes the chamber to drilling fluid pressure contained in the conduit, causing the piston to drive the firing pin against the detonator, which causes the perforating charge to detonate to create a displacement perforation through the conduit.