Case Studies

Offshore Persian Gulf

Medusa VS Multi-String Section Milling

Medusa VS Multi String

Section Milling Case Study

OVERVIEW:
Offshore in the Persian Gulf, near Qatar, a major operator faced a significant challenge in their plug and abandonment operations. Migrating gas from a subsurface reservoir had resulted in sustained casing pressures at surface. Previous attempts to perforate and squeeze cement had proven to be unsuccessful. Multiple cemented casing strings across the reservoir interval prevented the use of conventional section milling tools. The operator turned to Abrado’s proprietary tooling safely milled all windows without damaging the outermost casing string. With the same tool all internal casing strings were scrubbed creating a pristine wellbore environment eliminating micro annulus concerns and permitting the successful placement of all cement plugs.

CHALLENGES:
Based on the existing well profile, cementing, requirements dictated that windows be milled in both the 9-5/8″
and 13-5/8″ casings at ~7,500′. The casings were a P-110 “heavy wall” grade and a minimum of 100′ window was necessary for proper cement placement. Integrity of the cement plugs mandated the window milling operations be completed without creating any damage to the 18 5/8″ casing. Additonally, proper cement assurance required ID wall cleanout of the over 840′ of the 18 5/8″ casing through to the 9 5/8″ prior to cementing.

SOLUTIONS:
• Unique ‘patented” Medusa VS fully stabilized section milling technology was utilized to accomplish the project.
• A 124′ window was milled in the 9 5/8″ casing and a 100′ window was milled in the 13 5/8″ casing.
• Over 900′ of 18 5/8″, 13 5/8″ and 9 5/8″ casing ID was cleaned for cement placement in a single run with Medusa.
• Medusa mill swarf management program yields +95% recovery

RESULTS:
The project was successful with the windows completed and the well cemented. Plug and abandonment operations of the well were allowed to continue.

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