HYDRAULIC UNDERREAMER AND SECTIONS FOR USE THEREIN

摘要

A hydraulic underreamer for enlarging a wellbore (18) includes improved packer (20), cutting (24), jet pump (26), and mill (28) sections. The packer section (20) is designed to minimize wear on its sealing elements (36, 38), the cutting (24) and jet pump (26) sections are designed to minimize pressure requirements and optimize hydraulic efficiency, and the mill section (28) has a removable center assembly which allows effective well control when pulling he underreamer out of a "live" well filled with gas, such as methane.