Different Types of API Ring Gaskets Used in Well Control Equipment, Wellhead, Riser, and Xmas Tree

For well control equipment or pressure containment for oil and gas, ensuring reliable sealing solutions is paramount to maintaining operational integrity and safety standards. Among the array of sealing mechanisms employed, API ring gaskets stand out for their versatility and effectiveness in various applications, including wellheads, risers, and Xmas trees.

These ring gaskets, designated by different API types such as ‘R’, ‘RX’, ‘BX’, ‘AX’, ‘VX’, and ‘CX’, each offer unique sealing characteristics tailored to specific operational requirements. Understanding the intricacies of these API ring gaskets is essential for ensuring optimal performance and mitigating potential risks associated with leaks and equipment failures.

In this comprehensive exploration, we delve into the different types of API ring gaskets, their design principles, sealing mechanisms, and practical applications in well control equipment. From the traditional ‘R’ type gasket to the advanced ‘CX’ pressure-energized gasket, we examine their features, benefits, and challenges, providing insights to aid industry professionals in selecting the most suitable sealing solution for their specific operational needs.

API Type ‘R’ Ring Joint Gasket

The ‘R’ type ring joint gasket doesn’t rely on internal pressure for its sealing. It seals through small bands of contact between the grooves and the gasket’s OD and ID. The gasket can be octagonal or oval in cross-section. Due to its design, ‘R’ type gaskets don’t allow face-to-face contact between hubs or flanges, so external loads are managed through the sealing surfaces. However, vibration and external loads may deform the small bands of contact, potentially leading to leaks unless the flange bolting is regularly tightened.

API Type ‘RX’ Pressure-Energized Ring Joint Gasket

The ‘RX’ type gasket, developed by Cameron Iron Works and adopted by API, is pressure-energized. Sealing occurs along small contact bands between the grooves and the gasket’s OD, with the gasket slightly larger in diameter than the grooves, compressed slightly during joint tightening. ‘RX’ gaskets are designed to withstand external loads without deforming the sealing surfaces. It’s recommended to use a new gasket for each joint assembly.

API Type ‘BX’ Pressure-Energized Ring Joint Gasket

Similar to ‘RX’, ‘BX’ gaskets rely on pressure energization and sealing along small contact bands. However, achieving face-to-face contact between hubs or flanges can be challenging due to tolerance variations. Without proper contact, vibration and external loads may cause deformation and eventual leakage. ‘BX’ gaskets often feature axial holes to ensure pressure balance.

API Face-to-Face Type ‘RX’ Pressure-Energized Ring Joint Gasket

This ‘RX’ variant aims for face-to-face contact between hubs, with sealing occurring along small contact bands. However, the gasket may lack support on its ID, potentially leading to deformation during tightening and subsequent leaks. This type is not widely accepted in the industry.

‘CIW’ Type ‘RX’ Pressure-Energized Ring Joint Groove

Modified by CIW, these grooves aim to prevent gasket buckling and consequent leaks. While similar to standard ‘RX’ gaskets, these grooves offer improved support, reducing the likelihood of gasket deformation and leaks.

Type ‘AX’ and ‘VX’ Pressure-Energized Ring Joint Gasket

Developed by Cameron Iron Works and Vetco respectively, ‘AX’ and ‘VX’ gaskets seal along small contact bands, with the gasket slightly larger than the grooves. They feature smooth IDs and grooved ODs, allowing for minimal axial pressure loading. They’re designed to maintain face-to-face contact between hubs with minimal clamping force, with external loads transmitted through the hub faces.

‘CIW’ Type ‘CX’ Pressure-Energized Ring Joint Gasket

Similar to ‘AX’ and ‘VX’, ‘CX’ gaskets seal along small contact bands and are slightly larger than the grooves, with recessed designs for protection against keyseating. They allow for face-to-face contact between hubs with minimal clamping force and are suitable for use throughout the BOP and riser system.

Application of Type ‘AX’, ‘VX’, and ‘CX’ Pressure-Energized Ring Joint Gaskets

These gaskets facilitate face-to-face contact between hubs with minimal clamping force and are suitable for various applications, including at the base of the wellhead, side outlets on the BOP stack, and throughout the BOP and riser system.

Key Takeaways:

  • Pressure-energized gaskets generally offer better performance than non-energized ones.
  • Face-to-face contact, when achieved, distributes loads better and reduces gasket damage.
  • Each type has its own strengths and weaknesses, requiring careful selection based on application.

References 

Cormack, D. (2007). An introduction to well control calculations for drilling operations. 1st ed. Texas: Springer.

Crumpton, H. (2010). Well Control for Completions and Interventions. 1st ed. Texas: Gulf Publishing.

Grace, R. (2003). Blowout and well control handbook [recurso electrónico]. 1st ed. Paises Bajos: Gulf Professional Pub.

Grace, R. and Cudd, B. (1994). Advanced blowout & well control. 1st ed. Houston: Gulf Publishing Company.

Watson, D., Brittenham, T. and Moore, P. (2003). Advanced well control. 1st ed. Richardson, Tex.: Society of Petroleum Engineers.

Indicators of Formation Pressure Changes During Drilling Operations

Identifying signs of formation pressure changes is crucial for drilling operations, ensuring the safety and efficiency of the process. Drilling team on the rig plays a vital role in recognizing and communicating these indicators to supervisors. The following key signs should be closely monitored, acknowledging that some may have alternative interpretations.

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Understanding Drill Pipe Float Valve: Functionality, Types, and Benefits

A drill pipe float valve, also recognized as a non-return valve, is a specialized valve installed in the bottom hole assembly (BHA) and its primary function is to serve as a check valve, permitting the downward flow of drilling mud through the drill string but preventing any unwanted fluid from flowing back up into the drill string.

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What is a trip tank and its roles for drilling operation?

A trip tank serves as a compact, calibrated tank typically holding between 20 to 50 barrels, employed in drilling operations to monitor the flow of drilling fluid into and out of the wellbore whether pulling out (tripping out) or running in (tripping in) drill pipe or any tubular in the hole.

As each section of pipe is pulled out, the resulting void must be filled with drilling mud equivalent to the removed steel volume. This process, known as “pulling dry,” prevents a decrease in hydrostatic pressure, which can lead to unwanted wellbore events. The volume of mud pumped in is meticulously recorded on a trip sheet.

Trip tanks help detect potential kicks (inflow of formation fluids) by comparing the actual mud volume pumped in with the calculated displacement volume. If the actual volume is significantly lower, it suggests the well is swabbing and fluids are entering, a key indicator of a potential kick. Conversely, while running pipe in, any excess mud displaced should equal the steel displacement. The image below shows the typical trip tank diagram.

Trip tanks come in various configurations, but all prioritize accurate volume monitoring. The typical design is tall and narrow, allowing for easier detection of even slight changes in fluid level. This ensures precise measurement of fluid gain or loss within the wellbore.

The ability to continuously fill the hole and simultaneously capture returns in the trip tank is highly beneficial. This eliminates the need for constant driller attention, reducing the risk of hydrostatic pressure fluctuations. Comparing the actual trip tank volume changes with the calculated displacement volumes helps identify discrepancies and ensures the well is receiving the appropriate amount of mud. Trip tanks can also be utilized for dedicated wellbore monitoring. By diverting wellbore returns to the tank, even small fluid gains or losses can be identified, providing valuable information during flow checks and other critical operations. The image below shows the actual trip tank on the rig.

Trip Tank

Trip Tank

Rigorous maintenance of trip tanks is essential. Regular cleaning prevents solids buildup, while inspections ensure proper valve and pump functionality. Additionally, floats and instrumentation require calibration at specified intervals to maintain accuracy.

For even greater accuracy, especially during stripping operations, a separate tank with a smaller capacity (3-4 barrels) can be used. This “strip tank” allows for precise measurement of small fluid volumes before transferring them to the main trip tank for cumulative volume analysis.

Conclusion:

Trip tanks are indispensable tools in drilling operations, ensuring accurate wellbore pressure maintenance, kick detection, and overall wellbore status. By prioritizing reliability, accuracy, and meticulous maintenance, these vital pieces of equipment contribute significantly to a safe and efficient drilling process.

References 

Cormack, D. (2007). An introduction to well control calculations for drilling operations. 1st ed. Texas: Springer.

Crumpton, H. (2010). Well Control for Completions and Interventions. 1st ed. Texas: Gulf Publishing.

Grace, R. (2003). Blowout and well control handbook [recurso electrónico]. 1st ed. Paises Bajos: Gulf Professional Pub.

Grace, R. and Cudd, B. (1994). Advanced blowout & well control. 1st ed. Houston: Gulf Publishing Company.

Watson, D., Brittenham, T. and Moore, P. (2003). Advanced well control. 1st ed. Richardson, Tex.: Society of Petroleum Engineers.

What is Valve Removal Plug (VR plug) for Wellhead?

The Valve Removal Plug (VR Plug) is a specialized one-way check valve designed for threaded installation through an outlet valve on a casing head, casing spool, or tubing spool into a female thread in the outlet. This configuration effectively isolates the valve from pressure, enabling the convenient removal of the outlet valve for repair or replacement. After the necessary maintenance, the valve can be reinstalled, and the VR Plug can then be removed. It is important to note that VR Plugs are intended for short-term use and should not be considered a permanent substitute for wellhead valves. The image below is a VR plug.

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