An Analytical Solution for Aerated Mud andFoam Drilling Hydraulics in Deviated Holes

摘要

A closed form hydraulics equation was derived in thisstudy to predict bottom hole pressures during drillingahead and circulation break when aerated liquids areused for drilling inclined boreholes. The analytical modelwas developed on the basis of bubbly flow. It considerseffects of injected liquid, injected gas, formation fluidinflux, and cuttings entrained at bottom hole on thebottom hole pressure. Different rheological models areused for aerated liquids with and without foaming agents.The new equation together with selected rheologicalmodels was tested with data from two field-drilling cases.In the first case, a shallow (697 ft vertical depth)horizontal well was drilled with aerated mud. Thedifference between the measured and equation-calculatedbottom hole pressures is less than 1%. In the secondcase, a vertical well section was drilled with stable foamfrom 860 m to 884 m. The difference between the measured and equation-calculated bottom hole pressuresis less than 2%.