1. Field of the Invention
This invention relates to an improved sealed bearing particularly for use in oil and gas-well operations employing multiple liner-hanger assemblies.
2. Prior Art
In well-drilling operatons, such as in oil and gas wells, the well pipe is cemented into the bore hole and the liner pipes are suspended in the bore hole from hangers. It has been found desirable, during the cementing operations, to rotate the casing liner to ensure an even application of the cement and the proper displacement of the drilling mud. In operation the casing liner is cemented in the well casing by using a liner hanger, and the liner hanger is rotated through the use of a bearing assembly. Both open-type and seal bearings have been proposed for use in such liner-hanger assemblies and method, such as, for example, as set forth in U.S. Pat. No. 4,010,804, issued Mar. 8, 1977, and U.S. Pat. No. 4,033,640, issued July 5, 1977, both of which are hereby incorporated by reference in their entirety in this application.
The above patents are directed to a series of cooperating liner hangers which distribute the load on a bearing, with each hanger assembly located a selective distance from the other hanger assemblies, and a bearing arrangement employed with each of the hangers to provide rotational capacity to the hanger. FIGS. 5, 5A and 5B of the patents show prior-art bearings employed for liner-hanger assemblies and are described more particularly in column 5, lines 3-30 in each patent. The bearing assembly described comprises upper and lower bearing plates, with the interface of the two bearing plates fabricated of a resilient bearing material with a low coefficient of friction. Such bearings as described have not proven wholly satisfactory in use. The bearings being described as seal bearings are, in effect, not entirely sealed, and, under actual operating conditions, where the bearings are exposed to drilling mud and other contaminants under high torque conditions, are subject to failure. The present invention is directed to an improvement in bearings for the same end use.