�?�?t ρ l k + �?�?x i ρ l k v l = �?�?x j μ + μ t σ k �?k �?x j + G k �?ρ l ε �?Y MThe lessen in annular return stream will trigger the circulation pace of drilling fluid while in the annulus to lower, and the friction involving it and the annulus will decrease, Hence the BHP and standpipe pressure will reduce linearly wi