Study And Application Of Drilling String Vibration Signals

Drilling string vibration signal is a very multiform and complex wave, which contains three kinds, the vibration of the drilling string by itself, the vibration stimulated by the interaction of bit and the formation, the vibration induced by colliding between drill string and borehole. The vibration waves can reveal the real-time information for downhole drilling. Studying the method of measurement and data processing of the drilling string vibration signals can identify the downhole working status and optimize the well drilling parameters online. It is not only very helpful for prevention of drill string and bit early damage, but also for prevention of sticking and the drill bit accident. More over, it has important value for raising drilling speed and reducing drilling cost.In this paper, drilling string vibration mechanism was discussed, the transmission rules of the vibration wave in drill pipe were analyzed. Meanwhile, based on the investigation of various overseas measurements of vibration, a wireless measuring device for drilling vibration was designed, which has many advantages, such as low voltage, low power and antinoise. This device can realize the real time measurement of axial vibration and torsional vibration at the surface. Further more, process method of drilling string vibration signals which includes the signals characteristic value, spectral analysis, wavelet transformation was discussed. The drilling string vibration signals processing software was also designed successfully. Comprehensive indoor and field tests show that drill vibration measurement device can achieve real-time data acquisition with 250 meters effective data transmission distance. Drilling string processing software can real-time gather and analysis process vibration data, which is very useful operating mode analysis for and lithologic identification.