Calculate rheology from R600 and R300
The calculator determines PV, YP, YP/PV and AV from direct viscometer readings at 600 and 300 r/min.
PV = R600 − R300
YP = R300 − PV
YP/PV = YP ÷ PV
AV = R600 ÷ 2
Example
R600 = 38 and R300 = 25 give PV = 13 cP, YP = 12 lb/100 ft², YP/PV = 0.92 and AV = 19 cP.
Reference interpretation
For API-oriented drilling-grade bentonite, R600 ≥30 and YP/PV ≤3 are the two rheological reference points. For OCMA, the YP/PV maximum is 6.
Rheology alone is not a complete bentonite qualification. Filtrate volume and residue above 75 µm must also be evaluated.
Validation
R300 greater than R600 is flagged for review. When PV = 0, the YP/PV ratio is undefined. Negative inputs are invalid.
Calculation precision
The interface may round displayed results, but technical comparison uses the unrounded calculated value to avoid classification errors close to a limit.