Subsea Wellhead Tree

Overview

A subsea wellhead tree controls and routes hydrocarbon flow from a deepwater well into the production flowline, sitting on the seabed in place of the surface wellhead used on land. It contains the well pressure, provides the valves to open, throttle and shut in production, and gives a remotely operated vehicle the interfaces to operate and intervene without a rig on station. This is a vertical tree rated to 15,000 psi for a 3,000 m water depth, in sour-service materials.

The system stacks a structural high-pressure wellhead, the valve-bearing tree body, and the control and intervention hardware that lets it run unattended on the seabed for the field life.

Construction

The High-Pressure Wellhead Housing forms the structural foundation: a forged high-pressure housing landing the Casing Hanger strings with metal-to-metal annulus seals over a low-pressure conductor housing. Production tubing lands in the Production Tubing Hanger, whose stab plate aligns hydraulic and electric penetrations.

The Subsea Christmas Tree carries the production valve block, master, wing, swab and crossover gate valves, each a fail-safe-close slab gate driven by a spring-return hydraulic actuator, plus the production choke and an internal tree cap. The Connector System uses hydraulic collet connectors with API metal hub gaskets to lock the tree onto the wellhead and mate the flowlines.

Control runs through the Subsea Control Module, a retrievable module whose electronics, pilot solenoids and pressure/temperature sensors actuate the tree on multiplexed electro-hydraulic command. The Hydraulic Accumulator Bank stores hydraulic energy for fast valve response, and the ROV Interface Panel provides standardized torque buckets and hot-stab receptacles for ROV intervention and valve override.