What is the oilfield unit for dynamic viscosity?

What is the oilfield unit for dynamic viscosity?

• A. Poise
• B. Centipoise
• C. Pascal-second
• D. Stokes

Answer: (B)

Dynamic viscosity describes how resistant a fluid is to shear or gradual deformation. In petroleum practice, this resistance is most conveniently expressed in centipoise because it reflects the typical range of oil viscosities and is easy to read on field data. The centipoise is 0.001 Pa·s, since 1 poise equals 0.1 Pa·s, and 1 centipoise equals 0.01 poise. So a crude oil with a viscosity of, say, 20 cP has a dynamic viscosity of 0.020 Pa·s. The poise itself is rarely used because it’s too large for common liquids, and the Pascal-second is the SI unit but not the customary field unit. Stokes, on the other hand, is a unit for kinematic viscosity (units of area per time), not dynamic viscosity, so it doesn’t fit the quantity described.

Dynamic viscosity describes how resistant a fluid is to shear or gradual deformation. In petroleum practice, this resistance is most conveniently expressed in centipoise because it reflects the typical range of oil viscosities and is easy to read on field data. The centipoise is 0.001 Pa·s, since 1 poise equals 0.1 Pa·s, and 1 centipoise equals 0.01 poise. So a crude oil with a viscosity of, say, 20 cP has a dynamic viscosity of 0.020 Pa·s. The poise itself is rarely used because it’s too large for common liquids, and the Pascal-second is the SI unit but not the customary field unit. Stokes, on the other hand, is a unit for kinematic viscosity (units of area per time), not dynamic viscosity, so it doesn’t fit the quantity described.