A Comprehensive Prediction Model of Hydraulic Extended-Reach Limit Considering the Allowable Range of Drilling Fluid Flow Rate in Horizontal Drilling

Hydraulic extended-reach limit (HERL) model of horizontal extended-reach well (ERW) can predict the maximum measured depth (MMD) of the horizontal ERW. The HERL refers to the well’s MMD when drilling fluid cannot be normally circulated by drilling pump. Previous model analyzed the following two constraint conditions, drilling pump rated pressure and rated power. However, effects of the allowable range of drilling fluid flow rate (Q (min) ≤ Q ≤ Q (max)) were not considered. In this study, three cases of HERL model are proposed according to the relationship between allowable range of drilling fluid flow rate and rated flow rate of drilling pump (Q (r)). A horizontal ERW is analyzed to predict its HERL, especially its horizontal-section limit (L (h)). Results show that when Q (min) ≤ Q (r) ≤ Q (max) (Case I), L (h) depends both on horizontal-section limit based on rated pump pressure (L (h1)) and horizontal-section limit based on rated pump power (L (h2)); when Q (min) < Q (max) < Q (r) (Case II), L (h) is exclusively controlled by L (h1); while L (h) is only determined by L (h2) when Q (r) < Q (min) < Q (max) (Case III). Furthermore, L (h1) first increases and then decreases with the increase in drilling fluid flow rate, while L (h2) keeps decreasing as the drilling fluid flow rate increases. The comprehensive model provides a more accurate prediction on HERL.