Method and system for determining fluid pressures in wellbores and tubular conduits

A method for determining friction pressure losses in a flow conduit through which a non-Newtonian or generalized Newtonian fluid is being pumped, at a predetermined rate comprising the steps of:

• pumping said fluid through conduit means of known length and diameter and at plural known velocities and measuring the pressure differential due to friction over said known length at said plural velocities, respectively;
• calculating the generalized shear stress and shear rate for said plural velocities and respective pressure differentials due to friction losses;
• determining the consistency index (K') and the Power Law Index (n') for said fluid from the respective sets of values of shear stress and shear rate;
• selecting a scaling parameter of the fluid flowing through said flow conduit and determining a value of said scaling parameter for the flow conditions of said fluid flowing through said flow conduit;
• conducting said fluid through a pipe viscometer section at the same value of said scaling parameter;
• measuring the friction pressure loss, the fluid density, and the velocity of fluid flow through said viscometer section;
• calculating the value of the Fanning friction factor (f) based on the measured values of friction pressure loss, fluid density, fluid velocity and the effective diameter and length of said viscometer section;
• and
• determining the friction pressure loss through said flow conduit by measuring the effective diameter of said flow conduit, the effective length of said flow conduit, the density of said fluid, the velocity of fluid flow through said flow conduit and using said friction factor.