Tubing Heads in Oil & Gas Operations

The tubing head is a critical component in wellhead assemblies. It is a specialized flanged device or spool installed at the top of the uppermost casing head prior to perforation operations. This essential component performs dual primary functions: it supports the tubing string while creating a reliable seal in the annular space between the tubing and production casing. Furthermore, it provides convenient access to the casing-tubing annulus through strategically placed side outlets.
In day-to-day operations, the tubing head serves multiple vital functions that ensure smooth well operations. Beyond suspending the downhole tubing string, it effectively seals the annular space between the tubing and casing. The design incorporates a crucial transitional connection linking the casing head to the Christmas tree. Furthermore, the tubing head cross features two side outlets that facilitate essential operations such as water injection and well washing procedures.
From a structural perspective, it comprises several integrated components working in harmony. These include the tubing head cross, tubing hanger, sealing assembly, lock screws, gate valve, pressure gauge, and various flanges. The assembly's top section connects to the Christmas tree through either a flanged or clamp-type connection, utilizing a specialized flange design.
The tubing hanger, a crucial component of this assembly, sits securely within its tapered bore. This precision-engineered component not only suspends the tubing string but also ensures proper sealing between the suspended tubing and the head seat. For offshore oil and gas completions, which typically incorporate downhole safety valves, the tubing hanger design must include specific passages for hydraulic control lines. In wells equipped with electric submersible pumps, the design becomes even more sophisticated, requiring additional passages for downhole gas vent valves and sealed electric cable penetration.
The primary structural body of the assembly is comprised of the tubing head cross, located at the heart of the assembly. This component creates crucial connections between the casing head at its lower end and the Christmas tree at its upper end, with robust steel ring seals ensuring integrity at both connection points. The cross serves as both carrier and housing for the tubing hanger while enabling various essential operations, including forward and reverse circulation well washing, casing pressure monitoring, and diverse operations through the tubing-casing annulus.
The security of the tubing head assembly relies heavily on the tubing hanger lock screws, which must be installed once the tubing hanger is properly positioned. These lock screws play a vital role in securing the tubing hanger, effectively preventing any unwanted vertical movement or rotation that could compromise well integrity.
Completing the assembly is the lock screw flange plate, mounted securely on the casing cross. This component provides a stable seat for the tubing hanger while performing two critical functions: it compresses the packing to create an effective seal in the tubing-casing annulus while simultaneously securing the tubing against the substantial forces that could be generated by excessive downhole pressure.
For professional consultation regarding tubing head solutions tailored to your specific operational requirements, please contact our technical team at info@vigorpetroleum.com.