Dynamical measurement of drill tool attitude at stick-slip and continuous rotation mode in vertical drilling

Abstract

Wellbores with less than 3 degree of inclination are generally considered vertical in oil industry, as it is difficult to maintain wellbores vertical by traditional methods, the strap-down automatic vertical drilling system (AVDS) was developed to drill straight down fast and smoothly. The determination of drill tool attitudes is premise and critical for real time deviation control and correction in vertical drilling, where accelerometers and magnetometers sensors synchronously rotate with drilling tools. A dynamical measurement while drilling (MWD) algorithm is proposed in this paper by taking the magnetometers signals as rotation modes indicator. The drill tool rotation modes are divided into three categories: static, continuous rotation and stick-slip rotation mode. In static mode, the accelerators signals are seldom affected by vibration, normal MWD method is enough, so this paper focuses on measurement at stick-slip and continuous rotation modes. To filtering out real signals from the noised accelerometers by vibration, a pseudo-static model is applied for stick-slip mode; in continuous rotation mode, the algorithm is based on narrow band pass filter and the concept of evenly re-sampling in angle domain. The actual drilling results show that the proposed algorithm could provide reliable azimuth and inclination angle of drill tool.