Abstract: A cementing system where cement slurry is pumped down the annulus between the casing string and the well bore wall and then allowed to harden therein. A cement shoo on the lower end of the casing string prevents upward flow of fluids as the casing string is run, and then is opened and locked open in response to inside pressure. A normally open check valve in the casing string several joints above the cement shoo has flow passages that are closed by balls or ball discs which are suspended in a fluid spacer that is run ahead of the lower end of the column of cement slurry as it descends in the annulus.

Abstract: In accordance with an illustrative embodiment of the present invention, a container for preventing spilling of drilling mud onto the rig floor to thereby save the mud for later reuse includes a diametrically split and hinged barrel having a fixed lower seal assembly and a movable upper seal assembly which engage the outer wall of the drill pipe respectively below and above a joint connection that is to be unthreaded. Upon disconnection and upward movement, the upper seal moves upward with the pipe to totally eliminate wear which otherwise would result in seal and mud leakage.

Abstract: In accordance with an illustrative embodiment of the present invention, a restriction sub apparatus for use during well cementing operations includes a tubular body having an internal annular recess, and a plastic restriction sleeve mounted in the recess, such sleeve having an inner diameter which is less than the inner diameter of the body so that when a drive plate on a cement displacement plug encounters the inner portion of the sleeve during downward movement, such inner portion is progressively deformed and bulged inward until the bulge dissipates into a recessed region near the bottom end of the sleeve. The resistance afforded by the plastic sleeve to downward movement of the plug provides a positive pressure surge indication at the surface that the plug is located at a particular depth in the casing.

Abstract: In accordance with an illustrative embodiment of the present invention, a positively operable stop collar for providing a bridge in a well casing that prevents reverse flow of cement slurry includes a tubular body having upper and lower stop rings positioned in upper and lower recesses therein, seal rings between the recesses, and a bevel on the upper stop ring that is engaged by an inclined surface on the drive plate of a displacement plug to expand the upper stop ring and allow the drive plate to pass through the upper stop ring and to be locked in engagement with the seal rings.

Abstract: In accordance with an illustrative embodiment of the present invention, a clamp assembly that is tightened around a pipe to handle the same includes linked, circumferentially spaced gripping members open on one side to provide a gate region, a pressure operated piston and cylinder assembly that cooperates with a latch to close and open the gate region, and line connections to apply selected pressures to the opposite sides of the piston. A low level pneumatic pressure is applied to the outer side of the piston at all times and tends to open the clamp, and a high level of pressure is selectively applied to the opposite side of the piston to close the gate region. As the high pressure is bled off, the low pressure level automatically opens the gate region.

Abstract: In accordance with an illustrative embodiment of the present invention, a restriction sub apparatus for use during well cementing operations includes a tubular body having upper and lower internal recesses, a restriction ring having a shoulder engaged with the upper recess, and depending, inwardly inclined fingers at its lower end, and a back-up rubber ring mounted in the lower recess that yieldably resists expansion of the fingers as the drive plate of a displacement plug passes downward therethrough to provide a positive surface indication in the form of a pressure change that the plug is located at a particular depth.

Abstract: In accordance with illustrative embodiments of the present invention, a ball injecting apparatus for use in launching cementing plugs into a well casing includes a tubular body having an inlet port and one or more cylinders on the sides thereof adapted to be loaded with the balls, gates on the cylinders to prevent and permit injections of the balls, drive members extending into the upper and lower ends of the body and being rotatable relative thereto, and a sleeve slidably splined to the upper drive member and movable downward in the body in response to fluid pressure to transmit rotation of the upper drive member to the lower drive member. A set of uniquely arranged upper and lower plug assemblies are releasable attached to one another and are arranged to be sequentially released in response to seating of a ball, bomb or a dart therein.

Abstract: A displacement plug injection apparatus and manifold for sequentially injecting cementing plugs into the casing in an oil or gas well to reduce contamination of the interface between the well fluid and the cement, which apparatus includes an injection manifold for injecting pick-up balls into the fluid stream which pass through an inlet port in the casing to selectively pick-up cement displacement plugs in a plug set which are suspended or held in place with in the casing to be cemented. A positive mechanical indication of the injection of each pick-up ball is apparent and in adition a secondary magnetic sensor indicates a passage of a pick-up ball into the throat provided above the set of displacement plugs to indicate the beginning of the launch of each plug in the plug set. Also disclosed is a new and improved check valve apparatus for use in float collars and cementing shoes used in casing cementing operations.

Abstract: In accordance with illustrative embodiments of the present invention, restriction subs for use in setting cement plugs in wells include a tubular threaded adapter having an internal annular recess, and a metal restriction sleeve mount in such recess. In one embodiment, the sleeve has a corrugation that extends into the bore of the adapter to provide a deformable restriction; in another embodiment the sleeve has curved resilient tabs whose free ends extend into such bore. The restrictions are cooperable with a displacement plug having a metal expander member on its nose so that a distinct pressure is required to cause the expander member and plug to be forced through the restriction.

Abstract: A plug catcher assembly comprising an elongated adapter sub having threads on its upper end for connecting to the pipe string, a reverse circulation or jet sub threadedly connected to the adapter sub, and a catcher sub threadedly connected to the jet sub for catching plugs.The catcher sub and the jet sub have a plurality of upwardly and outwardly directed apertures in its wall which are arranged to promote turbulent flow and slurry mixing and to initially direct such slurry flow in the upward direction. The apertures are vertically spaced in the catcher sub so as to prevent pressure locking and to assure that the sub stays free of cement slurry.The catcher sub can contain and catch as many as eight plugs to save rig time by eliminating tripping of the string between plugging operations.Additionally, a plug launching apparatus is disclosed for use in launching a plurality of plugs during a cementing operation.