| 摘要 |
Nozzle jet drill bits for drilling drainholes from a wellbore are provided in a 4 -inch or larger casing. The drills are small enough to allow use of a bit diverter to turn the bits about 90 degrees in the casing when attached to an elastomeric high-pressure tube. Pumping of fluid, which may contain abrasive particles, through the bits allows drilling though the wall of casing, if present, and continued drilling into a formation surrounding the well without withdrawing the bit from the well. Direction-indicating instruments and geophones may be used to measure or monitor direction and location of the bit. One type of jet drill that may be used can change direction of drilling by controlling pressure at the bit
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