| 摘要 |
Failure of casing set in wells drilled through permafrost zones can be anticipated if the casing is set in the usual manner. As the warm formation fluid is produced up through the permafrost zone, the permafrost adjacent the well thaws. In many instances the casing could be damaged by buckling when it loses its lateral support, while the upper termination of the casing moves downward due to subsidence. This problem is relieved by cementing the casing only below the permafrost zone and suspending the weight of the uncemented portion of the casing from a means at the surface which would not be affected subsidence-wise by the thawed region. A constant tension device can be used to adjust the tension on the casing.
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