Surface Test Tree

Reliable surface well control during well testing or intervention operation


Our surface test tree (STT), comprised of API 6A manual or actuated gate valves and a dynamic string swivel, provides a means of surface well control during testing or intervention on a production well. The Anson™ STT provides the capability to flow or kill the well and to perform coiled tubing or wireline operations as part of well intervention.

Surface test tree configuration

The configuration of the tree can be dictated by the user or by design code requirements. Generally, the assembly is comprised of all (or most) of the following: main block assembly, low-torque dynamic string swivel, lower master valve, handling sub, and flow wings.

The main block assembly, which includes dual production bore isolation valves (master and swab), allows for full-bore passage of coiled tubing or wireline tools. The wing valves (flow and kill), located between the master and swab valves, isolate the STT from the well test equipment. They are used to allow the flow of wellbore fluids and injection of kill. The kill line into the STT can be supplied complete with an inline non-return valve to prevent return of any wellbore fluid to the kill pump.

All hydraulic lines can be terminated in a hydraulic bulkhead or stab plate mounted on the flowhead block.

The Anson low-torque, dynamic string swivel is typically situated below the main flowhead block assembly. This industry-leading string swivel allows for rotation of the drill string while the STT remains stationary, preventing the transfer of torque to the landing string/riser due to any rig rotational movement. For applications in which a hydraulic lower master valve is included in the tree assembly, we can offer a “live center” swivel design, which provides hydraulic communication between the rotating and static sections of the tree.

The surface test tree can be supplied designed, tested, and manufactured in accordance with ISO13628-7 /API 17G.

A lower master valve can be included to completely isolate the swivel and flowhead block from wellbore pressure.

The handling sub located above the main block enables rig elevators to raise and lower the tree in the derrick. The handling sub can be used to interface with wireline or coiled tubing equipment as required.

Flow wings allow hydraulic umbilical connection from the rig floor to the kill and flow valves on the flowhead block.

Control systems

Alongside our surface test trees, we can also supply a control system designed to suit your operations. NOV has dedicated engineers with vast experience in design of these packages.


  • Sizes and pressure ratings: 31/16 in. through 7.3/8 in. with operating pressures up to 20,000 psi 
  • The actuation technology used on the STT ensures reliability and performance validated by performance qualification testing to API 6A PR2F. Closure times on the safety-critical flow wing can be enhanced by the inclusion of a quick exhaust valve in the hydraulic return line, reducing shutdown time to less than 5 seconds for specific applications. 
  • E-type gate valve technology includes no performance-limiting elastomeric seals in the design construction. PTFE and metal sealing technology are used throughout the valve design. 
  • The valve actuators and hydraulic piping on the flowhead body are protected from impact by inclusion of a bumper/crash frame on the flowhead block.   
  • Skid bases, frames, or baskets can be included upon request, designed for ease of shipping and protection. 
  • Can be supplied completely gas tested to API 6A PSL3G on request 
  • Anson 6 3/8-in. 15K Compact Surface Test Tree Spec Sheet

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