Drilling fluid removal in primary well cementing

The present invention relates to methods of ensuring the maximum removal of drilling fluid from a well bore including gelled drilling fluid and filter cake deposited on the walls of the well bore prior to placing cement in the well bore between a pipe disposed therein and the walls thereof. The methods basically comprise circulating the drilling fluid through the well bore while monitoring the drilling fluid pressure, flow rate, viscosity, temperature and density. The circulating volume of drilling fluid in the well bore is then calculated and compared with the total volume available in the well bore to determine the volume of drilling fluid remaining on the walls of the well bore.