Casing circulator and method

An improved method of circulating drilling mud from adjacent a lowermost end of a casing string in a well bore so that the casing string may be lowered into the well bore, the lowering of the casing string into the well bore being controlled by regulating downward movement of traveling blocks with respect to a rig floor, an uppermost end of the casing string extending above the rig floor to a position adjacent an elevator suspended from the traveling blocks for selectively grasping the uppermost end of the casing string, the method comprising:

• providing a casing circulator having an exterior sealing member and an interior packer tube defining a fluid flow path;
• suspending the casing circulator from the traveling blocks while securing the casing string in a fixed position with respect to the rig floor;
• lowering the travel block to a position such that the casing circulator is within the uppermost end of the casing string at a position above the rig floor while the casing string is fixed with respect to the rig floor;
• thereafter activating the casing circulator to seal the sealing member between the casing string and the interior packer tube;
• establishing fluid communciation between the interior of the packer tube and the interior of the casing string below the casing circulator while maintaining the sealing element in its sealed position;
• thereafter pumping the drilling mud through the casing circulator and into the casing string to wash the well bore adjacent the lowermost end of the casing string;
• thereafter deactivating the casing circulator to unseal the sealing element from the casing string;
• and
• releasing the casing string from its fixed position, fixing the casing string to the elevator, and lowering the elevator to lower the casing string further into the well bore.

A casing circulator for temporarily sealing the uppermost end of a casing string extending into a well bore, the uppermost end of the casing string extending above the rig floor to a position adjacent an elevator suspended from traveling blocks, the casing circulator comprising:

• packer tube means and defining a fluid flow path there through;
• external sealing sleeve means radially outward of the packer tube means and formed from an elastomeric material for sealing engagement with an internal surface of the uppermost end of the casing string;
• the sealing sleeve means being radially moveable with respect to the packer tube means and sealed therewith at both its upper end and its lower end;
• one or more ports extending radially through the packer tube means for providing fluid communication between the fluid flow path and the interior of the casing string, and between the fluid flow path and an interior surface of the sealing sleeve means as a function of the axial position of the sealing sleeve means with respect to the packer tube means;
• and
• guiding means secured to a lower end of a packer tube means for directing the sealing sleeve means downward into the uppermost end of the casing string.