Abstract: A continuously adjusted calculated annulus drilling fluid lag time while drilling oil and gas wells and analyzing the drilling mud at the well surface for formation gas, fluids and rock in order to accurately index the release of the formation gas, fluids and rock released by the drill bit with the depth at which they were released. The method obtains such analyses by using a computer and pumping pressure to accurately track the drilling mud time lag and automatically adjusts for variations in the annulus flow rate to correlate the recorded data with its originating depth.