Abstract
Downhole drill string vibration data can provide an effective reference for research drill string vibration during drilling. In this paper, the research group used a storage-type downhole vibration measurement equipment equipped with an orthogonal, three-axis accelerometer to measure and collect drill string vibration signals during drilling in an oil well. Based on the installation characteristics of the sensor, the relationship between the acceleration measurement value of the sensor and the center acceleration value of the drill string is obtained. Then the time-domain signals representative of the vibration in igneous rock drilling is analyzed. It can be found that the occurrence of stick-slip vibration can be judged by the regular wave packets in the time-domain signal, while the time-domain signal of whirl is disorderly. The main frequency of stick-slip vibration in the low-frequency band is 0.1221 Hz and the period of stick-slip vibration is very close to 10 s through Fast Fourier (FFT) and Short-time Fourier transform (DTFT) methods. In the process of whirling, two frequencies, respectively, 0.05341 Hz and 155.5 Hz, play a major role. The frequency 0.05341 Hz is very close to the reciprocal of the period of 20 s when the peak energy spectrum density appears, indicating that the occurrence of whirl is very likely to be related to the natural frequency of the drilling tool. Through further time-frequency analysis, it also can be found that the occurrence of whirl and stick-slip is greatly related to the use of torsional impactors and jars.
Highlights
In the process of oil field development and oil and gas reservoir exploration, drilling is a project with high-cost and high-risk characteristics
The vibration of the drill string downhole can generally be divided into four patterns: longitudinal vibration, transverse vibration, torsional vibration, and whirl [13]
Fast Fourier transform can analyze each frequency component in drill string vibration, and short-time Fourier transform can clarify the change law of each frequency with time
Summary
In the process of oil field development and oil and gas reservoir exploration, drilling is a project with high-cost and high-risk characteristics. Through fast Fourier transform [33] and short-time Fourier transform [34] methods, we analyzed the time-frequency characteristics of vibration signals It provided an effective basis for identifying harmful vibrations in time and proposing damping measures during igneous rock drilling. In order to reduce the impact of the jar and the torsion device on the vibration measurement signal, the vibration measurement equipment was installed 32 m above the drill bit, 30.25 m from the lower torsion impactor, and 99 m from the upper jar. The three-axis acceleration sensor was eccentrically installed on the body of the drill string vibration measurement equipment. In the process of drilling into the igneous rock, the borehole wall collapsed and blocks frequently occurred This vibration measurement mainly collected vibration data with a depth of 4565~5020 m. Trically on the measuring equipment, the vibration acceleration at the center of the drill
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