Patent ID: 8530393

Claim:
A method comprising: providing a test drilling fluid comprising a test base fluid and a plurality of test particulates, wherein a first normal stress difference of the test drilling fluid without the plurality of test particulates is characterized by having a normal stress of N 1(TB) as calculated in a rheological procedure that includes a known rheometer model, testing temperature, testing pressure, testing shear ramp rate, and testing gap setting; and adjusting the concentration of the plurality of test particulates in the test drilling fluid to achieve a minimum concentration of the test particulate in the test drilling fluid that will substantially plug a tapered slot, testing the test drilling fluid with the minimum concentration of the test particulate with the rheological procedure to determine a normal stress of N 1(TA) ; and, calculating Δ N 1(p) =|N 1(A) |−|N 1(B) |; providing a drilling fluid comprising a base fluid and a plurality of particulates, wherein a first normal stress difference of the drilling fluid without the plurality of particulates is characterized by having a normal stress of N 1(B) ) as calculated in a rheological procedure that includes a known rheometer model, testing temperature, testing pressure, testing shear ramp rate, and testing gap setting; and testing the drilling fluid with a concentration of the particulates with the rheological procedure to determine a normal stress of N 1(A) ; and, calculating Δ N 1(F) =|N 1(A) |−|N 1(B) |; adjusting the concentration of the plurality of particulates in the drilling fluid by comparing the value of a first normal stress difference of the drilling fluid (ΔN 1(F) ) to the plug normal stress difference of a test base drilling fluid (ΔN 1(p) so that ΔN 1(F) ≧ΔN 1(p) .