| 摘要 |
A method and apparatus for use in stage-cementing an oil well in the region of a lost circulation zone that is proximate an annular space defined by the lower end of an outer casing surrounding an inner casing include a load-bearing annular steel plate of substantial thickness that is positioned on, and maintained stationary relative to the inner casing by supporting and retaining means secured to the inner casing, the outer diameter of the plate being less than the inside diameter of the outer casing so that the plate can be lowered with the inner casing string to the desired location inside of the outer casing and, with a layer of gravel, to provide a seal and support the cement poured into the annulus between the inner and outer casings.
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