Assessing Conductor and Casing Systems for Damage from Extreme Snag Loads

June 2014
Y. Arikan, R. Koska, J. Zlokich

Conductor and casing systems for subsea wells can be damaged due to excessive loads caused by vessel drift offs and snag loads. These types of accidental loads on the conductor and casing system are uncontrolled in nature and hence difficult to predict. Therefore, designing the system for these types of loads can be very challenging and economically not practical. Additionally, in the event of an incident subsea, a conductor and casing system is permanently installed and cannot readily be retrieved or inspected once the damage is done.
The decision to abandon or to produce from a well with a damaged conductor has serious financial and environmental consequences and should be fully understood. Therefore, to make a knowledgeable decision, it is necessary to understand extent of the damage and its implications for future operations by forensic analytical tools. This paper examines the methodology of a conductor and casing system damage assessment in order to support more informed decisions and provides a case example for a typical deepwater subsea well undergone excessive accidental loading. The objective of the assessment is (1) to verify wellhead system integrity and (2) evaluate the effect of any future operations on the integrity of the system. The paper outlines a process, suggested code checks, and analysis techniques which can be implemented to determine fitness for service of an excessively loaded wellhead system.

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