Method to characterize fracture plugging efficiency for drilling fluids

A method for determining a Plug Normal Stress Difference (ΔN1(p), the method comprising:

• providing a test base drilling fluid that is characterized by having a first normal stress difference N1(TB) when measured in a rheological procedure that includes a rheometer, testing temperature, testing pressure, testing shear ramp rate, and testing gap setting;
• adding a first concentration of a test particulate to the test base drilling fluid;
• adjusting the concentration of the test particulate in the test base drilling fluid to achieve a minimum concentration of the test particulate in the test base drilling fluid that will substantially plug a tapered slot,
• testing the test base drilling fluid with the minimum concentration of the test particulate using the same rheological procedure to determine the its first normal stress difference, N1(TA);
• and wherein the tapered slot has a width between about 0.1 mm and about 6 mm;
• and
• calculating ΔN1(p)=|N1(TA)|−|N1(M)|.

A method for determining a Plug Normal Stress Difference (ΔN1(p)), the method comprising:

• providing a test base drilling fluid comprising an oil-based fluid and a polar organic molecule that is characterized by having a first normal stress difference of N1(TB) when measured in a rheological procedure that includes a rheometer, testing temperature, testing pressure, testing shear ramp rate, and testing gap setting;
• adding a first concentration of a test particulate to the test base drilling fluid, the test particulate comprising a fiber;
• adjusting the concentration of the test particulate in the test base drilling fluid to achieve a minimum concentration of the test particulate in the test base drilling fluid that will substantially plug a tapered slot,
• testing the test base drilling fluid with the minimum concentration of the test particulate using the same rheological procedure to determine its first normal stress difference, N1(TA);
• and
• calculating ΔN1(p)=IN1(TA)I - IN1(TB)I.