Well casing flotation device and method

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. This method and device have the added benefit of safely venting air, and not adding a low density miscible fluid to the well bore casing annulus.