| 摘要 |
Impending bearing failure, seal failure and drilling an undergage well bore, among other things, are immediately detected by sensing the presence of aqueous drilling fluid in a lubricant or other type of sealed cavity of a drilling tool or the like during a downhole drilling operation in an environment of aqueous fluid. Electrical conduction elements are preferably employed to sense the presence of the aqueous fluid. The electrical conduction means may employ a soluble anhydrous conductive material which, when in contact with the aqueous drilling fluid, dissolves or becomes an electrical conductor to signal the presence of the aqueous fluid. The aqueous fluid may additionally serve as an electrolyte between two dissimilar metals, thereby forming a galvanic cell, or as a conductor between a pair of contact terminals. In a drilling operation, a signal is preferably transmitted from a downhole location to the surface of the earth by mud pulse telemetry. In order to sense the drilling of an undergage well bore, material normally plugging the entrance of a conduit leading to the cavity is eroded during excessive wear, thereby admitting aqueous fluid to the cavity.
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