So the gradient of pressure decline in vertical well section and deviated well section is different, it aroused the gradient of fluid viscosity in the two sections has differentia.

• 在稠油流动过程中，压力损失主要表现为摩阻损失，因此，在定向井中，直井段和斜井段的压降梯度有所不同，流体粘度梯度在直井段和斜井段也有差异。