Published July 2018

Bridging in horizontal wellbore drilling and its liquidation

D.S. Akhundov

F.N. Ismailov

Drilling with incomplete removal of cuttings leads to the formation of so-called cutting pads, resulting in the bridging of annular space, accompanied by tightening, which can cause stuck with complete loss of circulation. It was established by repeated observations that while drilling well with a large diameter due to the low rate of upward drilling mud, large-sized particles of sludge are accumulated in lower parts of bottom-hole assembly. With increasing concentration of cutting pads during washing, they moving in the annulus, connect with mud wall cake and thickening clay particles form a plug. It was established by practice that to prevent bridging, the rate of upward drilling mud should be not less than 0.50 m/s. In case if it is not possible to increase the rate, it is necessary to add 8-10 % of oil into the drilling mud.