| 摘要 |
A lateral wellbore (58) is formed from a high side ("H") of a horizontal portion of a primary wellbore (34) with a drill bit assembly (10) that has a selectively extendable pilot bit (22). The drill bit assembly (10) is mounted on a lower end of a drill string (36). A bit guide (38) is disposed adjacent the drill bit assembly (10) for urging the drill bit assembly ( 10) in a lateral direction against the high side ("H") of the primary wellbore (34). Rotating the drill bit assembly (10) while urging the drill bit assembly (10) upward creates a groove (50) in a subterranean formation ("F") adjacent the primary wellbore (34). This forms a ledge (52) at a far end of the groove (50). The drill string (36) is then drawn back from the groove (50), and the pilot bit (22) is deployed. Urging the drill bit assembly (10) forward engages the pilot bit (22) with the ledge (52), providing leverage for retaining the drill bit assembly (10) in an orientation for excavating the lateral wellbore (58). |
