Method and apparatus for placing and cementing casing in horizontal wells

摘要

An apparatus (10) for placing and cementing a casing string (12) in a horizontal well bore section (14) comprises a float shoe (18) attached to the end of the casing string (12) and a float collar (22) connected in the casing string (12) for trapping air (25) in a first portion (24) of the casing string (12) thereby causing it to be buoyed up during placement by drilling fluid (16) contained in the well bore. A selectively openable and releasable closed baffle assembly (34) is connected within the casing string (12) for trapping air (25) or a low density fluid (38) in a second portion (36) of the casing string (12) thereby causing it to also be buoyed up by drilling fluid (16) in the well bore. The buoying up of the casing string reduces placement drag and consequent compressive loading on the casing string (12). A method of the invention comprises placing the apparatus (10) in a horizontal well bore section (14), opening the closed baffle means (34) to allow fluid circulation and conditioning of the annulus (13), landing a bottom cementing plug on the baffle assembly (90), releasing the baffle assembly (90) and moving it to the float collar (22). A cement slurry is thereafter placed in the annulus and allowed to set therein. IMAGE