Cementing casing in a large diameter mud drilled well

摘要

A method of cementing casing in a large diameter mud drilled well is shown. A drilling rig turns drill pipe with sufficient down pressure being applied to a drill bit to drill a large diameter borehole. Initially drilling mud flows down the annulus between the drill pipe and borehole, then back up the drill pipe. An air pressure line in the drill pipe creates a suction at the drill bit. Direction of flow of drilling mud is reversed when the drill pipe is replaced with casing. Cuttings and heavy mud are removed from the borehole by bi-directionally rotating a casing while reciprocating up and down near a bottom of the borehole. When the desired mud weight and viscosity is reached, mud flow is stopped and cement is applied through a tremie tube.