Local drags of the completion string with packers in horizontal wells

Abstract

The multistage stimulation technique and horizontal wells are increasingly being utilized to improve oil and gas recovery. However, the sticking that occurs due to large drag during the completion string with packers tripping into the horizontal section, resulting in an abandoned well and huge economic losses. Based on a classical drag model, this paper illustrates how local drags affect the overall stress of the completion string by a case study. Mechanical models are also presented for analyzing the local drag of packers in horizontal sections considering the effects of microsteps or slots, borehole curvatures, and caliper variation respectively. The results confirmed that the local contact force is affected by centralizers, and local drags can be magnified during their upward transmission process. It is revealed that the slopes of microsteps or slots affect more on local drag of packers than the effects of microsteps’s height and slots’ depth; Moreover, the local drag of the packer was found increases with the increase of the borehole curvature, but less affected by the caliper variation; As to the effect of cuttings on the local drag of packers, it is affected by cuttings size and cuttings amount and cannot be quantitatively analyzed. This research could be utilized as a theoretical reference for estimating the sticking risks of the completion string and conditioning the horizontal open hole.