Parameter optimization based on deepwater drilling system simulation: A pre-salt exploration well in Brazil

Abstract

The vibration of downhole drilling tools is the primary factor that limits the ROP of deep-water salt drilling. Pre-drilling modeling is an essential method for analyzing the dynamic characteristics of the drilling system. Currently, there is limited research on coupling models between the single riser model and drill string model in deepwater drilling dynamics, which hampers offshore drilling dynamics development. In this study, we integrated the dynamic riser model with the flexible drillstring dynamic model, optimized the system's boundary conditions through experiments, and established an advanced full-scale deepwater drilling system. Through virtual drilling simulation analysis and energy flow calculations of the drilling process, we investigated the movement trajectory of the drillstring system at different positions and its correlation with downhole vibration in deepwater drilling. Finally, we performed parameter optimization on Brazil exploration well salt formation. The results indicate that the rotational speed significantly influences the vibration intensity and motion state of both the drill string and downhole drilling tool. Moreover, the kinetic energy and strain energy of BHA effectively reflect the motion state of the downhole drilling tool. When drilling salt and salt intercalation in the Brazil exploration well, the WOB was controlled within 200 kN and 180 kN, and the rotational speed was controlled within 180 rpm and 140 rpm, respectively. This ensured optimal stability and minimized vibrations within the drill string system. The virtual simulation work based on deepwater drilling systems can provide guidance for designing and planning actual drilling operations, as well as proposing reasonable drilling parameters to enhance stability and ROP in the drilling process.