| http://www.w3.org/ns/prov#value | - The invention, including the arrangement of the drillstems 18 and 82 and the retrievable bit assemblies 22 and 88, as well as the retrievable motor assembly 100, provide several advantages in well drilling operations including the elimination of expensive and hazardous tripping of the drillstem into and out of the wellbore for changing the components such as the bit assemblies and motors as well
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