E-Line Cable Considerations for Well Intervention in Gas Wells

When performing well interventions, the choice of a suitable cable is critical to ensure well control is maintained while deploying wireline through pressure control equipment (PCE). Depending on the well conditions, many considerations should be taken into account for choosing the best cable solution for any intervention work. In this week's article, we will look at the main factors influencing cable choice, and the reasons why these factors must be considered during the planning phase of the job.

From an HSE and well control perspective, to ensure safe and efficient operations, key considerations include:

• Well Conditions: What are the surface and downhole pressures and temperatures, and are additional measures needed with deployment into gas wells.
• Pressure Control Equipment: As a minimum requirement, the PCE should be rated for a working pressure of at least 1.2 times the maximum potential well head pressure. The grease control head should be configured correctly for the expected well head pressure (WHP) and matched to the wireline cable.
• Wireline Grease: The viscosity of the wireline grease at the operating temperature is often something that is overlooked, and it is essential that viscosity charts are used to identify the correct type of grease for any planned operation.

With the well conditions and pressure control equipment requirements understood, it is critical that the cable chosen is compatible. Most interventions use standard mono or coaxial cables, but some are hepta-cables, with the most common sizes of cables being 7/32” (0.22”) and 5/16” (0.32”).

Larger cables, such as those used in open-hole logging have significant limitations to ensure a seal in gas environments and should be avoided in their use. ?This is due to their mechanical properties and variations in the cable diameter across its length, which makes it difficult to remain within the PCE tolerances for the grease control head.

It is recommended, where possible to use a previously seasoned cable. Seasoned wireline cables are better prepared for the rigors of downhole operations, offering improved performance, reliability, and longevity. Seasoned cables also prevent torque imbalances between the armour layers which helps prevent mechanical issues and potential damage to the cable conductor, that may result in the loss of electrical integrity. While using alloy cables, it may still be possible to damage the conductor as the cable is difficult to season due to their material properties.

The seasoning process involves subjecting the wireline cable to cycles of tension and relaxation, bending over sheaves, and sometimes temperature variations, depending on the specific protocols of the manufacturer or operator. This process is usually performed when the cable is deployed into the well.

• Tension Cycling: The cable is stretched under controlled tension, then allowed to relax, in a series of cycles. This helps to align the internal strands and wires, reducing internal stresses.
• Bending Over Sheaves: Running the cable over sheaves under tension simulates the bending stresses it will encounter in the well. This step further helps in stress redistribution and enhances the cable's flexibility.
• Temperature Conditioning: Some seasoning processes may also involve exposing the cable to temperature variations, especially if the cable is expected to operate in extreme temperature conditions. This step can help in adjusting the cable's material properties to those specific conditions.

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Technical Advisory

A separate method of improved well head sealing pressure is by using a polymer cable. These are an advanced design in the construction of wireline cables, with polymer interlayers (polymers between armours, or gas-blocked cables) impregnated during the cable manufacturing stages. This design enhancement brings several key advantages, improving the cable's performance, durability, and overall effectiveness. Key benefits of polymer cables include:

• Impact Resistance: The polymer layer acts as a cushion, absorbing shocks and impacts that could otherwise damage the internal components of the cable. This is particularly beneficial when navigating through rough wellbore conditions or during handling on the surface.
• Abrasion Resistance: The added layer provides an extra barrier against abrasion, which is common in downhole environments where the cable may rub against the well casing, rocks, or other hard surfaces.
• Cable Seasoning: There is no requirement to season the cable as torque imbalances cannot occur between the inner and outer armoured layers, which are locked by the polymer
• Improved Insulation Properties: The polymer interlayer can enhance the overall electrical insulation of the cable. This is critical for maintaining signal integrity and ensuring efficient power delivery to downhole tools, especially in environments where electrical interference or leakage could be a concern.
• Environmental Protection: In addition to the sealing grease and corrosion inhibitors, the polymer layer provides additional protection against harsh downhole environments, including exposure to corrosive fluids, extreme temperatures, and high pressures. This can significantly extend the cable's service life by reducing wear and tear on its components.
• Fatigue Resistance: The flexibility and resilience of the polymer layer help distribute stresses more evenly across the cable, reducing the risk of fatigue-related failures. This is particularly important in applications involving frequent bending or movement of the cable.
• Flexible Design: The inclusion of a polymer layer can improve the overall flexibility of the cable, making it easier to handle and deploy, especially in complex wellbore geometries.
• Reduced Stiffness: Cables designed with polymer interlayers tend to be less stiff, allowing for easier spooling and unspooling, which can improve operational efficiency and reduce the risk of kinking or damage during handling.
• Fluid Resistance: Polymers selected for use in these layers are often resistant to hydraulic fluids and other chemicals encountered in downhole operations, preventing degradation that could affect the cable's structural integrity.
• Sealing and Protection: The polymer layer can also act as a sealant, preventing the ingress of fluids that could damage internal components or reduce the effectiveness of the cable's electrical and mechanical performance.

Wireline cables with polymer interlayers between armours offer a significant advancement in cable technology, especially in a gas environment, providing operators with a tool that is not only more durable and reliable but also better suited to the demanding conditions of downhole operations. These cables represent a thoughtful integration of materials science and engineering design, aimed at overcoming some of the most challenging aspects of well intervention and logging activities.

Closing Remarks

There are distinct advantages in using a polymer cable, but even if your operation required the use of a standard logging cable it is essential to ensure that the correct planning has been performed to ensure a safe operation at the wellsite. If you need assistance with the planning of any well intervention operation, then get in touch with one&zero, where we would be happy to discuss your requirements.