Schlumberger

Case Study: KOC Achieves High-Quality Window Through Dual Casing in Complex Sidetracking Job

IDEAS platform and WhipSim software enable accurate and efficient wellbore departure in challenging Raudhatain carbonate field, Kuwait

Challenge: Sidetrack from existing wellbore with 9 5/8-in and 13 3/8-in casing in challenging high-shock carbonate environment.

Solution:

  • Ensure efficient operation and minimized shock and vibration by modeling and analyzing the BHA and operation parameters using IDEAS integrated dynamic design and analysis platform and WhipSim whipstock simulation software.
  • Use TrackMaster CH cased hole whipstock system to deliver high-quality full-gauge window for exiting the two casings.

Result: Successfully performed dual-casing exit with mitigated BHA shock loading.

Efficiently perform challenging dual-casing exit operation

Sidetracking a preexisting drilled and cased wellbore poses many challenges. The operator must plan ahead to select the sidetracking depth while ensuring that all AFE and geological target objectives are met. Window quality is critical because it ensures that the subsequent BHAs will pass through the window without concern, helping to avoid costly and risky tripping procedures. Knowing the location of the centralizers and casing collars along the length of the wellbore at and around the kickoff point is crucial to a high-quality window. Operations grow in complexity when the job requires sidetracking the wellbore with the milling assembly and cutting two strings of casing.

Kuwait Oil Company (KOC) sought to sidetrack an existing well drilled in the Raudhatain carbonate field of northern Kuwait. The well included two casing strings at the kickoff point—9 5/8-in 43.5-lbm/ft L80 buttress thread casing (BTC) and 13 3/8-in 68-lbm/ft K55 BTC. The operator collaborated with Schlumberger on a solution that would achieve a high-quality window and wellbore departure, minimize vibration, and mitigate losses at the kickoff point.

Model BHA and simulate operation with Schlumberger technologies

For this challenging application, Schlumberger engineers recommended the TrackMaster CH cased hole whipstock system because it delivers high-quality full-gauge windows for casing exit operations. The system’s mill behavior and cutting structures were modeled using IDEAS integrated dynamic design and analysis platform to select the configuration that would generate minimal vibration. Additionally, the engineers studied the feasibility of a bimill versus a trimill BHA.

Considering the dimensions of the whipstock slide and mill position during the milling operations, the engineers finalized a parameter road map and studied the placement of the centralizers and casing collars along the length of the casing at the kickoff point. The exact locations where the lead mill initiates the cut at each casing string were analyzed to help determine the setting depths for the whipstock.

Additionally, Schlumberger engineers used the WhipSim whipstock simulation software to check the bending moments and stresses for the pass-through BHA because the dogleg through the window can pose additional concerns. WhipSim software helps ensure that completion strings are not affected by the dogleg across the whipstock. The software calculates the dogleg severity for a liner or BHA pass-through and the forces or stresses of the liner or BHA. Schlumberger engineers also reviewed the total volume of cuttings that would be generated from the milling operation while cutting two strings of casing.

Successfully meet objectives of complex sidetracking campaign

The TrackMaster CH system delivered a successful dual-casing exit with a high-quality full-gauge window. The planning using the IDEAS platform and WhipSim software helped to mitigate BHA shock loading. This success enabled increased confidence in IDEA platform’s ability to accurately identify the root cause of damaging vibrations in the planning stage while sidetracking through carbonates in Kuwait.


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The TrackMaster CH System Delivers a Successful Dual-Casing Exit

KOC Achieves High-Quality Window Through Dual Casing in Complex Sidetracking Job
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