Abstract: The gate valve 10 suitable for controlling fluid flow into a gas injection well of a hydrocarbon recovery operation includes a thru-conduit valve body 12, a bonnet 30, an operator handle 36 for raising and lowering a gate 22. A pair of seat assemblies 26, 28 are provided on opposing sides of the gate. Each seat assembly seals with a planar face of the gate, and includes a metal seat ring 56 and a pair of concentric face seals 70 and 72 supported on the seat ring. The seal rings are fabricated from a selected plastic material, and may be easily removed and reinstalled on the seat ring for customizing the gate valve for specific applications, and for reduced maintenance. The seat ring 56 is configured to facilitate its removal from the valve body.