Glass Disk Barrier Subs

MCT glass disk barrier subs are tubing-conveyed tools that place a temporary pressure barrier in the completion string. The glass disk holds pressure for testing, setting and isolation, then opens at a pre-set pressure to restore the tubing bore. The range covers six variants: Glass Disk Flow Sub, Glass Disk Surge Sub, Underbalance Glass Disk Sub, Packer Setting Device, Well Barrier Glass Disk and Floating Device Glass Disk.

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What Is a Glass Disk Sub?

A glass disk sub is a short tubular sub that holds a glass disk inside the tubing bore. While the disk is intact, it isolates the string above from the well below, so the tubing can be pressure tested, a hydraulic packer can be set, or the string can be run dry or partly empty. When the operation is complete, the disk is sheared by applied pressure at a value set for the job, with mechanical opening as an alternative, leaving no residue in the well.

Key Features

• No moving parts: nothing to stick, jam or fail to shift downhole
• Integral design: the disk is housed in a one-piece sub body
• No ports: no side ports or extra leak paths in the string
• Primary shear by pressure: opens at a pre-set pressure customized to the application
• Alternative mechanical opening: a secondary option if pressure opening is not possible
• No residue after shearing: the disk leaves no debris that could restrict the bore or damage equipment
• Customizable: size, rating, shear pressure, material and elastomer grades to suit the well
• Can be redressed: the sub can be redressed and run again

Glass Disk Flow Sub

Keeps the tubing isolated while the string is run and tested, then opens on demand to establish the flow path for well kick-off and production. The flow sub is widely used in tubing-conveyed perforating (TCP), perforating and drill stem testing (DST) strings, run together with the Glass Disk Surge Sub, surge valves and the Underbalance Glass Disk Sub to control when and how the well is opened to flow.

Glass Disk Surge Sub

Holds a pressure differential across the disk until it is opened. Breaking the disk releases a sudden inflow surge, typically used for perforation clean-up and to remove debris from the near-wellbore area.

Underbalance Glass Disk Sub

Lets the tubing be run with a reduced or empty fluid column, holding the underbalanced condition until the disk is opened. This gives an instant underbalance at the moment of opening, for perforating or for bringing the well on without swabbing.

Packer Setting Device

Provides a temporary plug below a hydraulic-set packer so setting pressure can be applied down the tubing. The same disk allows tubing pressure tests while running in hole. Once the packer is set and tested, the disk is opened by pressure. See this tool in service: glass disk barrier case study, offshore gas well, North Africa.

Well Barrier Glass Disk

Acts as a temporary, pressure-tested barrier in the tubing during completion operations, holding pressure from above and below until the barrier is no longer required and the disk is opened.

Floating Device Glass Disk

Traps air or light fluid in the lower section of a casing or liner string to make it buoyant, reducing drag and hook load when running long deviated and horizontal strings. When the string is on depth, the disk is opened by pressure and normal circulation resumes.

Specifications

• Sizes: 2-3/8″ to 7″
• Pressure rating: 0 to 15,000 psi
• Temperature rating: up to 400°F
• Disk opening: primary by pressure, with shear pressure customized to the application; mechanical opening as an alternative
• Materials: available in all material grades
• Elastomers: available in all elastomer grades, selected for well fluids and temperature
• Threads: to customer specification
• Customized products: sizes, ratings and configurations outside this range are available on request. Contact MCT.

RFQ: What to Include

To help MCT recommend the right glass disk sub, include in your request:

• Variant required (flow, surge, underbalance, packer setting, well barrier or floating device)
• Tubing or casing size, weight and grade
• Thread connection required
• Pressure rating and required disk opening pressure
• Bottom-hole temperature and well fluids, including H2S or CO2
• Setting depth and planned test pressures
• Quantity and delivery location

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Frequently Asked Questions

What sizes and pressure ratings are available?

MCT glass disk subs are available from 2-3/8″ to 7″, rated from 0 to 15,000 psi and up to 400°F. Other sizes and ratings can be engineered on request.

Can the opening pressure be set for my job?

Yes. The disk opening (shear) pressure is customized to each application, so it sits above your planned test and setting pressures with the margin your program requires.

Does the glass leave debris in the well?

No. MCT glass disks leave no residue after shearing, so there is nothing to restrict the bore or interfere with equipment run later. The sub has no moving parts and no ports, and it can be redressed for reuse.

Which material and elastomer grades can you supply?

MCT supplies glass disk subs in all material and elastomer grades to suit the well environment.