Wellhead Equipment and Well Control Safety System (Workover Safety Barrier Assembly) Workover operations face pressurized wells, oil and gas wells, overflow wells, and sand-producing wells, making well control equipment of paramount importance. 1. Wellhead Christmas Tree Assembly Comprising gate valves, a cross (spool), casing head, and tubing hanger, it is the main wellhead equipment of oil and water wells. Workover operations require coordination of opening, closing,