(57) There is described an adjustable bent sub comprising a cylindrical housing (12) having
a first uphole portion (20) and a second downhole portion (22), the up and downhole
portions being axially offset to one another, a tubular mandrel (14) having a first
uphole end (39) and a second downhole end (43), the up and downhole ends being axially
offset to one another, the uphole end of the mandrel being receivable within the housing
means for longitudinal and rotational movement relative thereto, connectors (65,71)
provided between the mandrel and the housing to prevent the relative rotation thereof
when the mandrel is in a first locked position relative to the housing, a lock (84)
actuatable to maintain the mandrel in a first locked position thereof or to release
the mandrel for longitudinal movement thereof relative to the housing into a second
unlocked position in which the mandrel and housing are free to rotate relative to
one another, a piston (58) concentrically disposed in the housing for longitudinal
movement relative thereto, and a spring (50) concentrically disposed in the housing
for biasing the piston into contact with an end of the mandrel, wherein the rotation
of the mandrel relative to the housing increases or decreases the amount of bend in
the bent sub between predetermined limits.
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