| 摘要 |
A method for preventing annular fluid flow following primary cementing of oil and gas well casings is disclosed. Pursuant to said method the casing is vibrated so as to maintain the hydrostatic pressure of the cement column surrounding the casing at or above the pressure of the fluids in the various formations penetrated by the well until the cement has acquired its initial set. The vibration may be either continuous or intermittent. Preferably, the vibration has a low frequency. The method may include the additional step of applying pressure to the surface of the cemented annulus while the cement is curing. The vibration may be induced in several ways. For example, the casing may be vibrated by simultaneous or sequential explosions of a slow-burning black powder. Alternatively, hydraulic jars may be used to strike blows on the casing causing the casing to vibrate.
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