base fluid circulating system converted to ecd units for the same time period as described above in area 2 any sweep effects on ecd are not relevant area 1 and area 2 added together give the total mass flow rate of the base fluid circulating system for the time t u2212 t area 3 is the additional contribution of the sweep to ecd calculated using the density and theological properties of the sweep multiplied by time t u2212 t the contribution to area 3 mass flow rate by the sweep viscosity can be calculated at the wellsite when the sweep exits the wellbore or can be imported from hydraulics modeling example articles discussing such modeling as known in the industry are u201c validation of advanced hydraulic modeling using pwd data u201d by p charlez m easton g morrice and p tardy otc paper 8804 presented at the 1998 offshore technology conference in houston may 4 7 1998 and u201c field hydraulic tests improve hpht drilling safety and performance u201d by p isambourg d bertin and m branghetto spe drilling amp completion 14 4 december 1999 the viscosity related part of area 3 is usually relatively small in relation to the other areas area 4 is the additional mass flow rate resulting from the incorporation of drill cuttings brought out of the wellbore by the sweep the sum of all of the responses areas 1 4 is the total mass flow rate calculated from the pressure losses measured by the pwd tool for.