A wellhead forms the surface pressure boundary connecting casing strings, later completion equipment, and pressure-management access throughout the well life. China Vigor's Casing Head Assembly is in the Wellhead & Well Control category, where selection must match the actual casing program, pressure class, connection system, sealing design, and governing procedures. It is more than a structural fitting: it is an engineered interface between surface casing, subsequent strings, valves, outlets, and the equipment installed above. Current drawings, applicable standards, and approved procedures govern final selection; generic examples are not Vigor-specific ratings.
The Casing String Interface
A casing head commonly provides a means to suspend and seal the next casing string while creating a pressure-containing body at the wellhead. Depending on configuration, it can include a bowl for a casing hanger, side outlets, test ports, lockdown features, and interfaces for a spool or other wellhead equipment. The assembly must transfer load and maintain alignment while the planned casing string is landed and sealed.
Dimensional control is essential. Nominal casing outside diameter, casing weight, coupling clearance, and hanger geometry must match the selected bowl and seal arrangement. A mismatch may not be apparent from nominal size alone, particularly when casing strings have different wall thicknesses or connection styles. Before running casing, the field team should verify the current assembly drawing, bill of materials, and installation instructions.
Layered Pressure-Boundary Control
Well-control reliability depends on more than a body rating. It also requires compatible seals, clean sealing surfaces, correctly made connections, proper bolt loading where flanges are used, tested valves, and a documented pressure-test sequence. Pressure classes are commonly expressed in psi, while test durations may be stated in minutes or hours. The exact values must come from the wellhead program and manufacturer documentation for the selected configuration, including any 100°C temperature condition and 8 hours exposure requirement.
A disciplined plan normally defines:
The active pressure boundary during drilling, casing installation, completion, testing, and later intervention.
Test medium, target pressure, hold period, gauge calibration, acceptance criteria, and recording method.
For example, 2,000 psi, 5,000 psi, and 10,000 psi are familiar industry pressure references, but none is a claimed rating for a particular Vigor Casing Head Assembly. Similarly, a 15-minute, 30-minute, or 60-minute test hold only has meaning when prescribed by the approved procedure.
Outlets Need Managed Access
Side outlets can provide access for annulus monitoring, circulation, or connection to well-control equipment. Their use must remain governed by the pressure-control plan. Valves, plugs, and temporary lines should be selected and installed as a compatible system. An outlet is not automatically safe to open because it is accessible at surface. The work instructions should identify which valves are normally open or closed, who has authority to change the lineup, and how the lineup is verified before pressure is applied.
Loads Extend Beyond Pressure
A casing head assembly can experience suspended-casing load, thermal changes, surface-equipment weight, pressure thrust, and installation loads. The design must identify anticipated axial, bending, and pressure-related loads, then compare them with the approved equipment envelope. A 13-3/8 inch surface casing string and a 9-5/8 inch intermediate string are common industry examples of different interfaces needing purpose-selected hanger and seal systems; they are not claims about one Vigor assembly.
Wellhead elevation and alignment affect the stack above the casing head. Poor alignment can complicate installation of subsequent spools, valves, or pressure-control equipment. Crews should follow the approved lifting plan, protect sealing surfaces, and prevent damage from dropped objects or uncontrolled welding heat. Any field modification requires engineering approval because changes to pressure-containing equipment can affect integrity and traceability.
Records Support Later Operations
Installation records create a baseline for drilling, completion, and intervention teams. Records should identify the assembly configuration, available traceability information, casing details, hanger and seal components, required torque or make-up records, pressure-test results, and deviations. Photos of the assembled wellhead and protected outlets can help later crews confirm the surface configuration before connecting equipment.
China Vigor can support review of the Casing Head Assembly against current product data when the casing sizes, connection requirements, pressure and temperature conditions, service environment, and documentation needs are available. That evidence-led approach keeps the decision technical and traceable for the well-control responsibilities placed on the equipment.
*For Casing Head Assembly information, contact China Vigor at info@vigorpetroleum.com or +86 28 81161513.*
