Permanent fiber-optic cable

Pressure rating

20,000 psi [138 MPa]

Temperature rating

Up to 572 degF [300 degC]

Applications

• Survey of multiphase flow profiles during production or injection, in conjunction with Optiq™ fiber-optic solutions
• Borehole seismic surveys via optical vertical seismic profiles (VSPs)
• Optimization and diagnostics of gas lift systems
• Monitoring of tubing and completion equipment for leak integrity and flow assurance
• Monitoring of mudline-to-riser temperature profiles for riser integrity
• Detection of frac hits during hydraulic fracturing
• Heavy oil thermal recovery operations, such as steam-assisted gravity drainage (SAGD) producer wells

Benefits

• Reduces costs and complexity with a single cable for multiple optical fibers
• Enables better understanding of the well and enhanced production and reservoir characterization via distributed temperature, acoustic, and strain measurements
• Enhances safety because it enables monitoring casing deformation and well integrity
• Helps improve production management with real-time measurements that provide immediate indication of changing downhole conditions

Features

• Survey and diagnostic services adaptable to project requirements
• Minimal impact on completion, wellhead interface, and installation procedures
• Tube-in-tube design for structural integrity and resistance to pressure
• Customizable single-mode and multimode fiber configurations with tailored filling compounds
• Centralized fiber in metal tube (FIMT) with polymer "belt" for protection and alignment
• Engineered to withstand hydrogen, high temperatures, mechanical stress, and corrosive downhole fluids
• Qualified to meet AWES* RP 3362-5d and SEAFOM F&C-01 standards for long-term reliability in the field

How it improves performance

Advanced design and construction
Permanent downhole fiber-optic cables are critical infrastructure in wellbore monitoring systems, ensuring reliable transmission of data for applications such as distributed temperature, acoustic, and strain sensing (DTS, DAS, and DSS)—all with one 1/4-in control line. These monitoring systems help improve well productivity by identifying trends throughout the producing life of the well, and they rely on the robust design and long-term survivability of optical cables under harsh downhole conditions.

Our cable uses the high-performance tube-in-tube design. At the core of this configuration is a fiber in metal tube (FIMT), which comprises optical fibers in a hermetically sealed stainless steel or INCONEL^® tube. The FIMT can be populated with a mix of single-mode and multimode fibers to accommodate a wide range of sensing and communication requirements. Filling gels within the FIMT provide additional protection against microbending and chemical ingress.

The FIMT is supported within the outer tube by an extruded polymer layer called the belt, which provides centralization and mechanical buffering. The outer tube acts as the primary pressure barrier and mechanical shield, enabling the cable to withstand extreme downhole conditions, including high pressure, elevated temperatures, mechanical shock, and corrosive fluids. Additional mechanical protection during deployment is provided by the outermost layer or encapsulation. The cable configuration is fully customizable, including quantity and type of fibers, encapsulation and armor materials, and filler.

To further enhance reliability, the cable is manufactured with controlled overstressing. Designed to prestress the cable assembly during fabrication, this process ensures that the fibers remain strain-free throughout deployment and operation, minimizing the risk of optical degradation or breakage. Additionally, cables are assembled in a moisture-controlled environment, which helps optimize resistance to hydrogen ingress—a known threat to long-term fiber performance in hydrocarbon environments.

Fiber selection is tailored to project requirements, with special attention to attenuation performance, bandwidth, and hydrogen resistance. Our standard fiber is rated 347 degF [175 degC]. We also offer a high-temperature version; designed for challenging applications with high heat (up to 572 degF [300 degC]) and hydrogen, this fiber is uniquely stable and reliable in heavy oil thermal recovery operations. For example, it is used in SAGD producer wells to ensure that the correct level of subcooling is maintained to avoid steam breakthrough from the injector above.

Conventional fiber temperature ratings do not take into account the degradation of the fiber when it is exposed to high levels of hydrogen (e.g., in SAGD wells), especially at high temperatures. We pioneered accelerated aging tests for optical fibers at high temperatures; the fiber resulting from this research demonstrates an almost 50-fold increase in light transmission, exceptional resistance to hydrogen, longer life, faster response times, and better spatial resolution.

Multiple configurations are available, whether the installation is on land, offshore, subsea, casing mounted, or tubing mounted.

How it works

One optical fiber provides temperature measurements every 0.5 m [about 1.6 ft] along its length, producing a profile of temperature effects along the production string and—when applicable—across the mudline. The fiber-optic line can be interrogated on a continuous or intermittent basis to provide rapid wellsite diagnostics without interfering with production. In addition to DTS, the fiber-optic cable enables DAS and DSS. At the surface, data can be transmitted to multiple remote locations via cable or wireless technologies.

Optiq real-time fiber-optic interpretation and analysis uses proprietary SLB algorithms and dynamic well models to analyze raw DTS, DAS, and DSS data in real time. Subsequently, a cloud or web interface presents actionable insights via an intuitive platform that is accessible from anywhere. Faster access to insights empowers immediate action, avoiding costly delays.

Additional information

If required, instead of using a cable, the optical fiber can be pumped through a conduit using SLB patented techniques to provide a cost-effective monitoring system suitable for high-volume applications. The conduit is hung from the surface across the interval of interest, and the temperature of the entire wellbore is monitored.