It’s important that the drill bit rotates in a stable manner with adequate contact pressure (called “weight-on-bit”, WOB). However, because of nonlinear dynamic motion of the drill pipe and the drill bit this control is sometimes difficult to achieve in deep drilling.
WOB changes, owing to the propagation of various kinds of vessel motion to the drill pipe. Therefore, the most effective way to mitigate the variations in WOB is to mitigate the propagation of these motions to the drill pipe. Chikyu has a heave compensator to help do just this. CDEX is evaluating the performance of the heave compensator via numerical simulation and data analysis, and improving software based on these evaluations. CDEX is also developing software to control the drilling torque and the rate of penetration.
- Establishing a mathematical model of the compensator, and evaluate the performance by analyzing data obtained from the compensator during actual field operations. These will be used in establishing operation guidelines to improve the performance of the compensator.
- Developing a software algorithm for active control of the compensator by considering the nonlinear dynamic motions of the drill pipe that occur in deep drilling.
- Developing and improving the software to control the drilling torque and the rate of penetration.
- Developing and improving the software to mitigate stick-slip.