Under formation conditions, the steel ball falls freely in a smooth standard pipe containing formation oil. By recording the falling time of the steel ball, the viscosity of crude oil is calculated by the following formula:
μ = κ(ρ1-ρ2)t
Where,μ—Dynamic viscosity of crude oil,in mPa·s;
t- The falling time of steel ball in s
ρ1、ρ2—Density of steel ball and crude oil
Κ—The viscometer constant , is related to the inclination angle of the standard tube, the size and density of the steel ball.