What Is a Wellhead in Oil and Gas?

By CRC Wellhead Staff | November 24, 2025

Many important systems work underground, out of sight, in the huge and complicated world of oil and gas research and production. However, every successful well requires a crucial visible component on the surface: the wellhead.

So, what is a wellhead in oil and gas? Simply put, a wellhead in oil and gas is a pressure-containing system installed at the surface of a well. It provides structural support, pressure control, and safe access to the wellbore during drilling, completion, and production.

In simple terms, the wellhead acts as the anchor point for the entire well system, connecting the underground casing strings to surface equipment and ensuring the well operates safely.

Why Is the Wellhead Important?

The wellhead is essential because it:

  • Supports casing strings during drilling

  • Seals the annulus between casing layers

  • Provides pressure control to prevent blowouts

  • Serves as the base for BOPs and production trees

  • Ensures safe flow of oil, gas, or injected fluids

Without a reliable wellhead system, drilling and production operations cannot be performed safely or efficiently.

Learn More About Different Wellhead Types

If you want to understand how wellheads vary depending on the application, you can explore the full breakdown here:
Read: Types of Wellhead – A Complete Guide

This internal resource explains conventional, unitized, thermal, high-pressure, and dual completion wellheads in detail.

The Essential Functions of a Wellhead System

 

A wellhead system is much more than a simple pipe connection. It performs several indispensable roles:

  1. Pressure Containment: This is its most critical function. The wellhead safely contains the immense pressures from the reservoir, preventing uncontrolled flow (blowouts) and ensuring the safety of personnel and the environment.

  2. Casing Suspension: As a well is drilled, multiple concentric steel pipes (casing strings) are run into the wellbore. The wellhead provides a means to suspend and anchor these heavy casing strings, transferring their weight to the surface foundation.

  3. Tubing Suspension: Once drilling and completion are finished, a smaller diameter pipe (tubing) is run inside the casing for hydrocarbon production. The wellhead also suspends this tubing string and provides a pressure-tight seal around it.

  4. Annulus Sealing: It seals the annular spaces between the different casing strings and between the tubing and the outermost casing string, preventing fluid migration between these spaces.

  5. Flow Control & Monitoring: The wellhead provides outlets for attaching valves (like the Christmas Tree) to control the flow of oil or gas, as well as ports for pressure gauges and other monitoring equipment.

Key Components of a Wellhead System

 

To perform these functions, a wellhead system is comprised of several interconnected wellhead components, all meticulously machined to precise specifications.

 

1. Casing Head

 

This is the foundational component of the wellhead. It connects directly to the surface casing, providing a base for subsequent components and a means to suspend the first string of casing.

 

2. Casing Spools

 

Stacked above the casing head, casing spools provide additional landing points for intermediate and production casing strings. Each spool also features outlets (side valves) for pressure relief or monitoring.

 

3. Tubing Head

 

Positioned atop the casing spools, the tubing head is where the production tubing string is suspended. It provides a pressure-tight seal around the tubing and typically includes outlets for the Christmas tree.

 

4. Casing Hangers & Tubing Hangers

 

These internal components are installed within the casing and tubing heads/spools. They physically support the weight of the casing and tubing strings and, crucially, contain the pressure in the annular spaces using various seal designs.

 

5. Wellhead Valves and Accessories

 

Beyond the core structure, the wellhead interfaces with a range of accessories:

  • Flow Tees and Crosses: These are attached to the side outlets of the heads and spools to divert or combine fluid flows.

  • Double Studded Adapters (DSAs) and Crossover Flanges: These critical pieces allow for connection between components of different sizes or pressure ratings, maintaining the overall system’s integrity.

CRC Wellhead Supply: Your Trusted API 6A Manufacturer

Understanding what is a wellhead in oil and gas highlights its immense importance. The manufacturing of these components demands absolute precision and strict adherence to industry standards.

At CRC Wellhead Supply, our comprehensive CNC Machining Edmonton facility is equipped with state-of-the-art lathes and mills, allowing us to produce every part with the exacting tolerances required. Our API Q1 and 6A certifications mean that our quality management system is verified, and eligible products can bear the coveted API monogram, assuring you of their compliance and reliability.

When you choose CRC Wellhead Supply, you’re choosing a partner committed to delivering industry-compliant, high-quality wellhead components that you can trust in your most demanding applications.

Contact us today to learn more about our API-monogrammed parts and how we can support your wellhead needs.

 

 

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