| 摘要 |
This apparatus provides an underreamer and a reamer or hole opener to enlarge an existing pilot hole thereby permitting further operation to be carried out in a well bore. The underreamer can be inserted down a well bore in the unexpanded condition and, since the radius of the eccentrically mounted cutters of the reamer or hole opener added to the radius of the unexpanded underreamer equals the pass through diameter (the inner diameter of the restriction), the entire assembly or apparatus can be inserted to the position requiring enlarging. The underreamer is expanded to engage the adjacent wall of the well bore and stabilize the reamer as it enlarges the hole. Since movement resulting from the lateral forces are restrained by the centralizer/underreamer as well as the bullnose or smaller pilot hole drill bit, the bi-center reamer can readily open the well bore to the desired diameter without lateral deviation.
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