Experimental Study of High-Frequency Drill String Vibrations Under Different Conditions

In this paper, the experience of measuring high-frequency drilling string vibrations during drilling is presented. Vibration registration is carried out by a borehole noise recorder which has specially been made for this purpose. Three accelerometers are built into its construction design. The measuring axes of those accelerometers form an orthogonal coordinate system. Vibrations are recorded in the frequency band from several hertz to 25 kHz. Measurements are carried out during various drilling operations, i.e., rotary drilling, directional drilling, reaming, making a connection, and circulation. The drill string includes a mud motor. Measurements were performed either during horizontal and vertical drilling. The total record involves several days and its size is approximately 250 GB. The recorded data includes oscillograms separately obtained from each of the three accelerometers and the time dependencies of temperature and internal pressure in the borehole. Since the main goal is investigating high-frequency noise during drilling, frequencies below 1 kHz are partially suppressed by a high-pass filter during registration. Some peculiarities of noise distribution in frequency domain under different drilling conditions are presented in this article. Modified Welch’s method is used for spectrum estimation.