Rotatable reciprocating collar for borehole casing

摘要

A rotatable reciprocating collar is provided for series connection into a borehole casing string. The collar includes a cylindrical barrel connected to one segment of the casing and a cylindrical mandrel telescopically positioned within the barrel and connected to the other segment of the casing. The mandrel has a plurality of splines projecting radially outward and the barrel has a corresponding plurality of splines projecting radially inward from its inner surface. The splines of the mandrel engage the splines of the barrel when the mandrel is telescopically extended so that the entire casing string can be rotated as a unit. After the lower segment of the casing string is fixed in place by a lower stage cementing operation, the upper segment of the casing string can be reciprocated toward the lower segment to telescopically retract the mandrel into the barrel. In the retracted position of the mandrel, the splines of the barrel and the mandrel are disengaged, thus allowing the upper segment of the casing string to be rotated and reciprocated with respect to the fixed lower segment to enhance cement bonding during the upper stage cementing operation.