Abstract: A system and method for maintaining continuous flow through a drill string during drill pipe connection includes establishing drilling fluid flow axially through the length of a tubular sub attached to the top of a drill string. The sub is then engaged with a collar disposed at least partially around the perimeter of the sub so as to define an exterior flow path along the exterior of the sub. Radial flow is then initiated into the sub through said collar and along said exterior flow path. Axial flow is then terminated through the length of the tubular sub while maintaining radial flow into the sub. A pipe joint is then attached to the top of the tubular sub, axial flow is reestablished through the length of the tubular sub, radial flow is terminated into the sub, and the collar is disengaged from the sub.

Abstract: Drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings are provided. Drill string flow control valves may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a piston axially movable within said valve housing and bearing against the valve sleeve, a biasing mechanism for biasing the valve sleeve into the closed position, a static pressure port for actuating said piston utilizing internal fluid pressure within said valve and a plurality of dynamic pressure ports for allowing a differential pressure to be exerted on the valve sleeve during dynamic flow conditions. The differential pressure exerted on the valve sleeve may be the result of an upstream pressure and a downstream pressure during fluid flow through said valve.

Abstract: A system for controlling drilling mud density in drilling operations that combines a base fluid of lesser/greater density than the drilling fluid required at the drill bit to drill the borehole to produce a combination return mud in a riser. Concentric tubular members are disclosed, wherein one tubular member, such as the drill string, is utilized to inject the drilling fluid into the wellbore. Another tubular member carries the combination fluid to the surface for separation by a centrifuge system. By combining appropriate quantities of drilling mud with another fluid, the density of the combination fluid carrying drill cuttings to the surface can be regulated. During separation by the centrifuge, a weir plate having an adjustable height is utilized in the centrifuge to regulate the separation of the base fluid from the drilling fluid, producing a high density fluid and a low density fluid.

Abstract: Controlling drilling mud density in drilling operations utilizing concentric drill tubes and at least two different density fluids. The mud required at the wellhead is combined with a base fluid of a different density to produce diluted mud in a riser. By combining the appropriate quantities of drilling mud with base fluid, greater control over the pressure in the wellbore and various risers can be achieved. Concentric drill tubes or risers are disclosed, wherein a first annulus defined within one riser is utilized to carry one fluid to the wellbore injection point, while a second annulus defined within another riser is utilized to carry a combination fluid and cuttings back to the drilling rig. In one embodiment with three concentric drill tubes, a third annulus is also define, wherein the various annuli can be utilized in various combinations to deliver at least two different fluids to the wellbore and return a combination fluid from the wellbore.

Abstract: A system for controlling drilling mud density in drilling operations that combines a base fluid of lesser/greater density than the drilling fluid required at the drill bit to drill the borehole to produce a combination return mud in a riser. Concentric tubular members are disclosed, wherein one tubular member, such as the drill string, is utilized to inject the drilling fluid into the wellbore. Another tubular member carries the combination fluid to the surface for separation by a centrifuge system. By combining appropriate quantities of drilling mud with another fluid, the density of the combination fluid carrying drill cuttings to the surface can be regulated. During separation by the centrifuge, a weir plate having an adjustable height is utilized in the centrifuge to regulate the separation of the base fluid from the drilling fluid, producing a high density fluid and a low density fluid.

Abstract: Drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings are provided. Drill string flow control valves may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a piston axially movable within said valve housing and bearing against the valve sleeve, a biasing mechanism for biasing the valve sleeve into the closed position, a static pressure port for actuating said piston utilizing internal fluid pressure within said valve and a plurality of dynamic pressure ports for allowing a differential pressure to be exerted on the valve sleeve during dynamic flow conditions. The differential pressure exerted on the valve sleeve may be the result of an upstream pressure and a downstream pressure during fluid flow through said valve.

Abstract: Drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings are provided. Drill string flow control valves may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a biasing mechanism for biasing the valve sleeve into the closed position, and a plurality of pressure ports for allowing a differential pressure to be exerted on the valve sleeve. The differential pressure exerted on the valve sleeve may be the result of an upstream pressure and a downstream pressure. By allowing a differential pressure resulting from a fluid flow to act on the valve sleeve, u-tubing in a drill string can be prevented or substantially reduced. Methods of use are also provided.