What is a capillary coiled tubing unit in oil and gas?

--Core Components, Key Functions & Oilfield Applications

 Learn what a capillary coiled tubing unit (CCTU) is in oil & gas. Discover its core components, functions (chemical injection, monitoring) for optimized downhole operations.

The Capillary Coiled Tubing Unit (CCTU) is a specialized system integral to modern oil and gas downhole operations, particularly for well intervention and logging. This article aims to clearly explain the core components and primary applications of the CCTU for oil and gas engineers and technicians, providing a professional technical reference for oil and gas production companies to optimize downhole operations and improve production efficiency.

Core Components of the Capillary Coiled Tubing Unit

The stable operation of the unit depends on the coordinated operation of key modules, each with clear and interrelated functions:

Capillary Coiled Tubing: The core component of the unit, this continuous length of small-diameter tubing must be engineered to withstand high pressure, temperature, and corrosive downhole environments.Materials of stainless steel or nickel alloy are selected based on actual operating conditions.

• The Tubing Reel: It is used to store and retract thousands or even tens of thousands of feet of continuous capillary tubing. The reel system includes a rotary joint, allowing fluid to be pumped into the tubing as it rotates.

• Injector Head: This mechanism grips the tubing and precisely injects it into or retrieves it from the wellbore.

• Control Cabin: From this central hub, operators monitor and manage all critical parameters in real time, including tubing depth, speed, and pumping pressures.

• Power Pack: Typically driven by a diesel engine, it provides the powerful power required for the injector head, reel, and other hydraulic equipment.

Core Functions

1. Chemical Injection for Well Integrity: CCTUs can precisely deliver corrosion and scale inhibitors into the wellbore, protecting production casing and extending the well's operational life.

2. Well Stimulation and Enhancement: The unit can accurately inject stimulation fluids or displacement agents into specific zones, targeting low-permeability reservoirs while minimizing formation damage.

3. More Convenient Parameter Monitoring: Manual logging can interrupt operations, but the Capillary Coiled Tubing Unit transmits real-time downhole temperature, pressure, and fluid composition data, facilitating timely adjustments to production plans.

MTSCO is a major supplier of oilfield services. Its Siri Tubing facility provides core components for Capillary Coiled Tubing Units for oil and gas applications. These units are made of stainless steel and nickel alloy, with single coil lengths up to 50,000 feet and a pressure resistance of 100 MPa. These units have been successfully used in deep wells and complex projects worldwide, adapting to the harsh underground operating environments.