�?�?t ε l ρ l v l + �?�?ε l ρ l v l v l = ε l �?�?τ l + ε l ρ l g �?ε l �?p �?β v l �?v s The reduce in annular return flow will trigger the flow pace of drilling fluid while in the annulus to minimize, and the friction concerning it and also the annulus will lessen, Hence the BHP and standpipe stress will minim