Abstract: A stage cementing apparatus (100) is disclosed which incorporates a stage cementing tool (102), a barrel (104) and a mandrel (106) for stage cementing of a casing within a wellbore. The apparatus (100) can be moved between a closed position preventing cement from flowing therethrough to the exterior of the casing at the apparatus to an open position to permit cement to flow from the interior of the casing exterior the casing to cement the casing to the wellbore. The barrel and mandrel can have cooperating splines which are engaged in a position which corresponds to the closed position of the apparatus. When the splines are disengaged, the apparatus is open to permit cement flow exterior the apparatus and concurrent rotation of the barrel relative to the mandrel to enhance the cementing of the casing within the wellbore.

Abstract: 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.