Abstract: A ported float shoe (5) and a landing collar (16) are attached at a first end of a portion of a casing string (4) and a sliding air trapping insert (20) is attached at the other end. The air trapping insert (20) includes a fluid flow passageway (24) blocked by a plug (22) attached by shear pins to the insert (20) or the air trapping insert is an inflatable insert (55) having a conduit (60) providing a fluid passageway to the first end. The air trapping insert and float shoe form an air cavity (12a or 12b) within the string portion (4). The air cavity provides buoyant forces during running, cementing or other casing operations within a borehole (2), reducing running drag and the related chance of a differentially stuck casing (4). It also allows reciprocation and rotation during cementing and avoids separate removal steps.

Abstract: A ported float shoe (5) and a landing collar (16) are attached at a first end of a portion of a casing string (4) and a sliding air trapping insert (20) is attached at the other end. The air trapping insert (20) includes a fluid flow passageway (24) blocked by a plug (22) attached by shear pins to the insert (20) or the air trapping insert is an inflatable insert (55) having a conduit (60) providing a fluid passageway to the first end. The air trapping insert and float shoe form an air cavity (12a or 12b) within the string portion (4). The air cavity provides buoyant forces during running, cementing or other casing operations within a borehole (2), reducing running drag and the related chance of a differentially stuck casing (4). It also allows reciprocation and rotation during cementing and avoids separate removal steps.

Abstract: A ported float shoe and a landing collar are attached at one end of a casing string and a sliding air trapping insert attached by shear pins at the other end. The air trapping insert includes a fluid flow passageway blocked by a plug attached by shear pins to the insert. The air trapping insert and float shoe form an air cavity within the string portion. After running the string into a deviated well bore, the shear pin supported plug is pressure actuated open to allow air to be vented and drilling mud to flow into the cavity. A wiper plug followed by pressurized cement slurry shears away the attached insert, opens the float shoe, moves the insert to the bottom of the well, and allows cementing of the casing. Moved apparatus (near well bottom) forms a single drillable unit until drilled out in normal post-cementing operations. The flotation method reduces insertion drag and the related chance of a differentially stuck casing, and avoids the separate removal steps required by current flotation techniques.