Automation of Drawworks and Topdrive Management To Minimize Swab/Surge and Poor-Downhole-Condition Effects

Abstract

Summary Careless axial and rotational movement of the drillstring can cause formation fracturing or fluid influx, resulting in costly remedial actions. With increasingly complex wellbore geometries and narrow geopressure windows, it is not always obvious for the driller how to estimate accurately the real maneuvering limits of the drawworks and the topdrive, especially under poor downhole conditions. The solution presented in this paper uses continuously updated safeguards applied to the drilling-control system to maintain a downhole pressure within the acceptable limits of the openhole formations. It automatically stops the movement of the drillstring in the case of abnormal hookloads or surface torques. Because automatic actions can be triggered in the case of an unexpected situation, some standard procedures have been fully automated, including friction tests and back reaming. Numerical models are used to constantly calculate the maximum accelerations and velocities, which can be applied to the drillstring in the current drilling conditions. The resulting envelope of protection is dependent on many factors. Therefore, a proper evaluation of the downhole conditions is of paramount importance for the quality of the calculated safeguards. An automatic calibration of the physical models, on the basis of surface measurements, is at the heart of the system. The calibrated mechanical models are used to determine the limits for abnormal surface torques or hookloads. It is, therefore, possible to take actions automatically in the case of overpull, set-down weight, or high torque. In 2008, a preliminary version of the system was tested during the drilling of a well in the North Sea. Even though the control algorithms did work well at that time, it was noticed that, in some circumstances, the drilling-control system would not be ready in time for fast-changing drilling conditions. An improved version of the drawworks and topdrive automation system has been tested during the drilling of three North Sea wells in the spring of 2009. In this last version, the response time of the system has been optimal at all times. The drillers involved in the testing of the system have found the system useful and user friendly.