Abstract
Abstract
Dynamic dysfunctions of the drillstring are extremely complex to model, and it is difficult to produce timely model updates to keep up with the continually changing conditions during drilling operations. This paper describes an integrated measurement system that mitigates the effects of damaging downhole vibration and enables the driller to instantaneously respond and evaluate the effectiveness of corrective actions.
The failure to measure all of the correct parameters will leave the driller blind to the existence of damaging vibration and lead to sub-optimal performance or equipment and drillstring failures. The integrated system of downhole and surface measurements combines a significant amount of surface, downhole, and formation information to help the driller to correctly identify the vibration mechanism and to determine the appropriate response. The system measures the movement of the bottomhole assembly (BHA), the levels of energy generated during episodes of vibration, and the energy going into the system.
The capability to clearly and concisely present the results of the analyses to the driller and to produce recommendations for the correct mitigation strategy is a powerful tool for controlling downhole vibration. Monitoring surface weight on bit (WOB), torque (TRQ), rotary speed (RPM), and standpipe pressure (SPP), and performing a frequency analysis helps to identify vibration signatures for stick/slip and bit bounce. Mechanical specific energy (MSE) calculations determine drilling efficiency. Downhole accelerometer, gyroscope, magnetometer, bending, tension, and torsion measurements used alongside formation evaluation data identify bit bounce, bit whirl, BHA whirl (both forward and backward), torsional resonance, bit chatter, modal coupling, and lateral shocks. A three-tier warning system brings attention to the presence of vibration, supplies the mechanism and corrective actions, and provides detailed analytical information to the expert. Tracking environmental exposure of downhole equipment enables the driller to determine when the operating limits of WOB, RPM, temperature, and dogleg severity (DLS), as well as axial, lateral, and torsional vibration, are being approached or exceeded.
This smart system reduces the reliance on expert analysis to identify the correct actions to mitigate the problem, leading to an increased speed of response. The combined capacities of identifying all vibration mechanisms, tracking the environmental exposure, and representing this information in an easily understood manner provides a powerful tool for the control of drilling operations.