Weight-On-Bit variations analyses in the drillstring of rotary drilling systems under Stick-Slip vibrations

Abstract

In this article, the main objective is to study the influences of weight-on-bit variation on the severity of stick-slip vibrations that appear in the toolstring of the rotary drilling systems. These types of vibrations can be very harmful to the equipment if not detected in real time and mitigated soon after. The only solution that is adopted in Algerian petroleum industry is the manipulation of drilling parameters, namely weight-on-bit and top drive torque. Where, the drillers as soon as they detect the appearance of such vibrations through abnormal decrease of rate of penetration (ROP) and the increase of the torque, they generally decrease the weight on bit and increase the torque of the top drive by increasing the angular velocity so that the vibrations will disappear and ROP will be maintained. However, the influences of the fast variation of these parameters (either increasing or decreasing) have not been previously studied. For that reason, the simulations conducted in this study are designed with different scenarios in order to analyze these effects for the severity of the stick-slip vibrations. Moreover, the importance of the analysis is that it allowed us to determine at what rate the Wob and Torque should be varied without creating sever vibrations that may damage the toolstring equipment. Therefore, it is highly recommended to consider the results of this study in suppressing the stick-slip vibrations