Dynamic Soltion Approach to the Inclination and Amizuth of Bottom Rotating Drill String

Abstract In the oil drilling process, measurement-while-drilling (MWD) system is usually used to provide real-time monitoring of the position and orientation of the bottom hole. Particularly, in rotary steerable drilling technology and application, how to accurately measure the spatial attitude (inclination, azimuth, tool face) of the bottom drilling tool in real time while the drill string rotating is a challenging problem. Current MWD surveying is performed along the well path at stationary survey stations, because of that the bottom drilling tool shows complex characteristics while rotating due to combined effect of their randomly nonlinear moving state, such as vertical vibration, horizontal vibration, and stick-slip. The effects of complex characteristics cause sensors to generate a great dynamic error which will accumulate gradually during attitude resolving, so ultimately measuring spatial attitude deviates seriously from the true value. This is a huge challenge for signal processing. In this paper, a set of "strap-down" measurement system was developed, the triaxial accelerometer and triaxial fluxgate were installed near the bit, and real-time well deviation and azimuth can been measured even when the drill string was rotating. However, according to the drilling field tests, playback analysis on storage data of the underground measurement indicates that drill string vibration is the main reason for measurement errors. So this paper proposed dynamic solution approach to the bottom of the rotating drill string attitude. By setting a time window, the real-time measurement of the accelerometer and the flux gate signal are processed and analyzed, the movement patterns of the rotary drilling tool at the bottom were judged within the time window.utilizing stick-slip vibration to improve measurement accuracy, reducing the impact of vibration on the measurement results at the same time. Although the stick-slip vibration should be avoided point of view the life of the drill string, we can still take advantage of it because of it cannot be avoided entirely. A continuous measurement while drilling system was developed and a large number of field test data were also analyzed. Simulation results in Matlab showed that recommended dynamic survey approach could effectively enhance measurement precision, and deduce effect of vibration on resolve results.