| 摘要 |
<p>An oil well casing assembly includes a perforated tube and upper and lower packers coupled to the upper and lower ends of the tube. The lower packer is in turn coupled to a spacer tube and the upper packer is connected to a casing string. Each packer includes an elastomeric sleeve bounded by upper and lower collars. The packers are so arranged that when the casing assembly is lowered into the borehole and comes to rest at the bottom of the borehole, the weight of the casing assembly is used to cause the elastomeric sleeves to swell out against the borehole surface, thereby sealing the casing assembly above and below the payzone. In addition, a casing seal is provided which comprises an elastomeric sleeve positioned between upper and lower rings around a pump column included in the casing assembly. The upper and lower rings are so mounted that the weight of the pump column causes the elastomeric sleeve to shorten axially and to swell out against the inside of the casing string, thereby providing an effective, airtight seal between the pump column and the casing string. The packers and casing seal of this invention can be used in a method for sealing a casing in place such that the casing can be removed when necessary. Furthermore, the normal pumping action of the pump inside the pump column serves to remove oil from the payzone area and, because of the seals provided by the casing seal, to reduce pressure in the payzone, thereby promoting the flow of oil into the perforated tube. This method can be used with other types of seals between the casing and the borehole and between the pump column and the casing.</p> |
