| 摘要 |
<p>Casing hardware, such as float collars and shoes, are used in oil well cementing operations. Some of the collars and shoes are constructed of a steel casing with a concrete core inside the casing. The casing structure of the collars and shoes now available places the core under a predominantly shearing force, so that it will fail at relatively low downhole differential pressures. The present invention provides a new design for the casing structure, which places the concrete core under a predominantly compressive force, and greatly increases the amount of pressure the core can withstand without failing.</p> |
