What is Tubing and Casing Couplin

A Tubing and Casing Coupling is a short, threaded cylindrical component used to connect two joints of tubing or casing in oil and gas wells. These casing & tubing couplings have internal threads that match the external threads of the pipe ends, allowing for a secure and pressure-tight connection.

Tubing Couplings: Join sections of tubing (smaller-diameter pipes used to transport hydrocarbons to the surface).

Casing Couplings: Connect casing (larger-diameter pipes that line the wellbore to stabilize and protect it).

Types of Tubing and Casing Couplings 

For Casing:API Round Thread (STC/LTC/BC)

Short Thread Coupling (STC): Shallow threads, used for shallow wells.

Long Thread Coupling (LTC): Deeper threads, better for medium-depth wells.

Buttress Thread (BC): Stronger than round threads, handles higher axial loads.

For Tubing:API Buttress Thread: Common for tubing, balances strength and sealing.

API Non-Upset (NU) / External Upset (EUE):

NU: No external thickening, weaker but smoother for downhole tools.

EUE: Reinforced ends for higher strength.

Differences Between Tubing Coupling and Casing Coupling

a. Function & Application

Tubing Coupling: Used to connect individual joints of tubing (smaller-diameter pipes that transport oil/gas to the surface). Tubing couplings must handle high-pressure production fluids and cyclic loads (e.g., from pump operations).

Casing Coupling: Used to join casing (larger-diameter pipes that line the wellbore to stabilize the formation). Casing couplings must withstand higher external pressures, axial loads during cementing, and potential collapse forces.

b. Size & Design

Tubing Coupling: Smaller in diameter (typically 2-4 inches), with finer threads (e.g., API Buttress or Premium threads) for better sealing in dynamic conditions.

Casing Coupling: Larger (4-20+ inches) with heavier threads (e.g., API Round or Extreme-line), designed for structural integrity rather than frequent movement.

c. Material & Strength

Tubing Coupling: Often made of corrosion-resistant alloys (e.g., 13Cr, Duplex SS) due to exposure to production fluids.

Casing Coupling: Typically carbon steel with higher yield strength (e.g., API L80, P110) to support wellbore loads but may lack corrosion resistance unless coated.

By Helen

Hello, I’m Helen, the export manager at Hebei Jiaruisike Oil Special Pipe Co., Ltd., overseeing international market development and customer relations for oil pipe products.

With 8 years of experience in the oil pipe trade, I specialize in global markets, technical standards, and production processes. I've successfully expanded into regions such as the Middle East, Africa, Southeast Asia, and South America, building lasting partnerships with international energy companies. My industry insights and negotiation skills have boosted export performance and optimized customer service systems.

I excel at cross-department collaboration to ensure efficient production, quality checks, timely delivery, and compliance with global standards. Staying attuned to market trends and policy shifts, I adapt sales strategies to meet challenges and competition.

Looking ahead, I aim to further strengthen our global presence and deliver quality products and services to customers worldwide.