Time-dependent cuttings transport modeling considering the effects of eccentricity, rotation and partial blockage in wellbore annuli

Abstract

This paper presents a new cuttings transport model that captures the time-dependent effects of pipe rotation, drillpipe eccentricity and annulus blockage on hole cleaning. By integrating the time-dependent model with well construction data, the level of cuttings deposition along the trajectory of the wellbore can be simulated in real-time. The model recalculates its hole cleaning assessment at every time-step, and can use real-time drilling data at pre-determined time/depth intervals for calibration purposes.The integrated, real-time hole cleaning model was applied to a field case. Field data from an actual stuck pipe event was used to calculate the behavior of the cuttings profile in time along the wellbore. The data show that a high rate of penetration whilst sliding with a directional motor in the near-horizontal section of the well resulted in a significant amount of cuttings buildup around the bottom hole assembly (BHA). Unsurprisingly, the drillstring packed off and became stuck on the final trip out of the hole. Moreover, the casing-hole annulus packed off and caused induced losses while cementing because of the cuttings bed left in the hole. If the proposed time-dependent cuttings transport model had been utilized, these well problems and associated non-productive time (NPT) could have been better predicted and possibly avoided.