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U.S. Department of the Interior
Minerals Management Service
Gulf of Mexico OCS Region |
Safety Alert No. 219
February 9, 2004 |
Contact: Jack
Williams
(504) 732-3012 |
Loss of Well Control While Drilling
Surface Hole
Recently an operator
drilled a well from a producing platform. Though the track of the new well was
within 100 ft of the tracks of the four previous wells drilled from the platform, an
anomalous, thick, highly porous sand deposit was encountered at a shallow depth.
Throughout the drilling of the
conductor casing hole and the setting of the conductor casing, significant drilling fluid
losses were experienced, and drilling and cementing returns were erratic in nature or
entirely absent due to unexpectedly permeable morphology. After the conductor casing
was set, the operator continued to face severe lost circulation problems during the
drilling of the surface casing hole, and the anomalous, thick sand deposits continued to
be encountered to a depth where the Operator planned to set surface casing.
While the crew was tripping to prepare
to set surface casing, the hole first went on vacuum, then ceased taking fluid, and then
began flowing. The annular was closed, the diverter system opened, and the flow,
mostly water, was placed into the downwind diverter line. After eight hours, flow
ceased and the well again began taking fluid. Normal lost circulation operations
were initiated and surface casing was run, sealing off the thief zone and the zone of
influx.
The failure or inability to forecast
the presence of the thick anomalous sand deposit, through use of sparker and shallow gas
hazard surveys, may have contributed to the failure to anticipate the difficult
circulation problems encountered.
In the Gulf of
Mexico, several shallow formation loss-of-well-control events have recently occurred
during drilling from producing platforms. The MMS recommends to operators and
drilling contractors that they thoroughly review shallow hazard information even when
operating from a previously drilled platform. Attention to formation anomalies, in
addition to actual shallow gas markers, may allow precautionary actions that prevent
potential loss of control situations.
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