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Section Milling is a job for Medusa®

Medusa® section milling and cutting technology was developed to meet the need for a cost-saving, permanent and verifiable 360-degree barrier to be placed in the wellbore without the need to cut/pull and dispose of casing strings, or conduct lengthy and expensive pilot milling.


Sustained Casing Pressure (SCP) existing between multiple casing strings in a well presents enormous challenges for the Operator tasked with permanently abandoning that well. Often, SCP is present in multiple casing annuli requiring multi string section milling to mitigate. Some of the key challenges to a successful single or dual string section milling operation are:

  • Eccentric casing strings, either cemented or uncemented, can result in “skimming” or “troughing” of the outer casing, often resulting in a more complex, costly abandonment.
  • Inadvertently “puncturing” the outer casing string thereby compromising the integrity of the wellbore further and introducing more complexity and cost to the operation.
  • Limited Expansion ratios that require smaller ID casing strings to be physically removed form the wellbore prior to gaining access to the larger casing strings harboring SCP.
  • Flush joint and semi flush joint casing connections are difficult to mill through in eccentric casing scenarios due to limited standoff and strict adherence to be non-damaging to the outer casing.
  • Centralisers in casing strings to be section milled can often be problematic to section milling tools and require patience to mill up without compromising either casing integrity or BHA integrity.
  • Swarf created by section milling is massively less than by pilot milling but still can be challenging if not managed efficiently. Swarf left in the well needs to be periodically pushed to bottom and swarf circulated to surface needs to be completely removed from the circulating fluid to mitigate erosion.
  • It is not uncommon to meet an obstruction in an old well that precludes further section milling progress in a downward manner. This could be catastrophic if the regulatory casing window length for permanent P&A has not yet been accomplished and there is no easy means to extend the casing window in an upward direction.


Fortunately, through experience and technological development, Abrado's unparalleled range of Medusa® section milling tools address all of the above challenges related to single and dual string section milling of windows and provide the least risky route to success for achieving Permanent and Verifiable P&A.

Medusa® Technology

Medusa® enables dynamically stabilized single and multiple string section milling while ensuring no harm to outer casing strings, regardless of casing eccentrics. Learn more.