Patent attributes
A frac plug has a mandrel (42) about which slips (48) and (56), conical rings (46) and (54), and a seal element (52) are disposed in conventional fashion. A setting rod (32) has an upper end secured to a firing head (16), extends through the mandrel (42), and has a lower end secured to a shoe (62) located at the bottom of the mandrel (42). A power charge (110) is located in an annular-shaped space (106) extending between the mandrel (42) and the setting rod (32). Flow ports (90) extend through the mandrel (42) to a barrel piston (94) disposed around the exterior of the mandrel (42). During setting, the setting rod (32) will release from the shoe (62) at a predetermined force, allowing retrieval of the setting rod (32) and the firing head (16) separate from the frac plug (14). The firing head (16) has flow passages (34) for passing ignition gasses from the primary igniter (28) to the secondary igniter (108) with the flow passages (34) extending at an angle to a longitudinal axis (30).
