frac stack

1. n. [Shale Gas, Well Completions, Well Workover and Intervention]
A Christmas tree installed specifically for the fracturing process. A frac stack typically consists of upper and lower master valves, flow cross, wing valves, goat head, and swab valve. Frac stacks generally have larger bores and higher pressure ratings than production trees to accommodate the high flow rates and pressures necessary for hydraulic fracturing.
Alternate Form: frac tree