Maintaining pressure key to casing integrity

Posted on 08 July 2014

By Linda Hsieh, Managing Editor

A 3D visualization created from caliper log data demonstrates deformation in the wellbore. Dr Trent Kaiser, Principal Consultant at Noetic Engineering, urged the industry to address casing deformation due to the practices being used for unconventional development.

A 3D visualization created from caliper log data demonstrates deformation in the wellbore. Dr Trent Kaiser, Principal Consultant at Noetic Engineering, urged the industry to address casing deformation due to the practices being used for unconventional development.

For drilling contractors, asset integrity is most strongly linked to the reliability and performance of drilling rigs and the equipment onboard those rigs. However, many other aspects – particularly downhole – make up critical pieces of the overall well integrity puzzle.

“For casing integrity, the primary concern is pressure integrity – making sure that the casing functions as a pressure vessel that provides a pressure conduit from the surface to the target,” Dr Trent Kaiser, Principal Consultant at Noetic Engineering, said. “The primary challenge is constructing the well – how do you design, assemble and install the casing while maintaining that needed pressure integrity to operate the well.”

A build-up of annular pressure between different casing strings or between the tubing and casing is one potential failure scenario. Drilling wear from inside the casing can also be a problem. “Corrosion is the other aspect of it. Over the life of the well, exposure to wellbore fluids might attack the casing wall and compromise wall thickness and its pressure integrity as a result.”

One of the most common issues surrounding casing integrity, however, is well deformation, Dr Kaiser said. If the operator can’t access deeper parts of the well to service it, the value of the well is quickly compromised. “We’ve seen time and again just how much deformation these wells can tolerate and still maintain their pressure integrity,” he said.

Dr Kaiser cited a casing integrity management program by a Canadian petroleum company where caliper logs are run after every thermal cycle in the well. “They monitor the deformation and have developed criteria that capture the deformation tolerance of the casing. Where in much of the world, you might recognize the deformation and think that’s a reason to shut-in the well, they are actively monitoring that definition and identifying more realistic limits of deformation to guide the management of the well and their choices about abandonment.”

Especially with the high level of activities in unconventional development in North America, casing integrity is a growing challenge. With unconventionals, “they have to really stress up the reservoir in order to make it productive. They stress it by either fracking or, in oil sands, by thermal stimulation. These introduce stresses and deformation on the wells that are quite challenging.”

In most wells, the worst casing loads are imposed during well construction, he said. “But in unconventional wells, the subsequent operation of those wells impose much higher loads than what the installation loads are.”

He believes that the industry will soon have to more specifically address casing deformation as a result of practices required for unconventional resources. “I think it’s something that the industry is just now coming to recognize as an issue. There is a big opportunity here to learn from failures and apply them to future well construction and future casing integrity developments.”

Leave a Reply

*

FEATURED MICROSITES


Recent Drilling News

  • 24 October 2014

    GDF SUEZ, BP discover new Central North Sea Field

    “This is an encouraging exploration discovery in a part of the Central North Sea that needs additional volumes of hydrocarbons to open up development options…

  • 24 October 2014

    Chevron, BP discover oil in deepwater US Gulf of Mexico

    The discovery well, on Keathley Canyon Block 10, was drilled by operator Chevron on behalf of the Guadalupe co-owners. The well encountered significant oil pay…

  • 22 October 2014

    Shell discovers gas in pre-salt reservoir offshore Gabon

    Shell announced a frontier exploration discovery offshore Gabon, West Africa. The well Leopard-1 encountered a substantial gas column with around 200 m net gas pay…

  • 22 October 2014

    Statoil proves new oil resources near Grane field in North Sea

    Well 25/8-18 S, drilled by the rig Transocean Leader, proved an oil column of 25 m in the Heimdal Formation. The estimated volume of the discovery…

  • 21 October 2014

    IADC Cybersecurity Task Group to provide industry guidance to assess risks

    The oil and gas industry is not immune to cybersecurity threats, from computer viruses and malware to targeted attacks. The IADC Advanced Rig Technology (ART) Committee…

  • Read more news