Identifying crater potential improves shallow gas kick control
- Louisiana State Univ./Petrobras, Baton Rouge, LA (United States)
- Louisiana State Univ., Baton Rouge, LA (United States)
An understanding of sea floor crater mechanisms can help drillers determine whether to divert or shut in a shallow gas kick. Proper well planning that considers potential shallow gas sources can eliminate some of the more common failure situations with both diverting and shutting in of a well. Current well control practice for land and bottom-supported marine rigs usually calls for shutting in the well when a kick is detected, providing sufficient casing has been set to keep any flow underground. The casing and surface equipment must have an adequately high working pressure to ensure that formation fracture occurs before the equipment fails. Even for high shut-in pressures, an underground blowout is preferable to a surface blowout. An operator may choose to divert the flow if the surface casing is not set deep enough to keep the underground flow outside the casing from breaking through the sediments to the surface. Once the flow reaches the surface, a crater may form at the sea bed, possibly sinking or damaging the rig. Craters increase the difficulty and time required to kill a blowout. The paper describes shallow gas environments, the decision to divert or shut in the well, fluid migration, cement bond failure, hydraulic fracture, shear failure, the effect of fault planes, crater mechanisms, formation liquefaction, piping, caving, historical cases, and a deepwater crater.
- OSTI ID:
- 5701327
- Journal Information:
- Oil and Gas Journal; (United States), Vol. 91:52; ISSN 0030-1388
- Country of Publication:
- United States
- Language:
- English
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