Analysis of wave disturbance in the drill string while releasing stuck pipes

Abstract

The work is devoted to testing the hypothesis about the possibility of assessing the nature of the release of the drilling tool by percussion devices by analyzing the response of the system in the form of vibration records of the upper end of the drilling tool. For this purpose, based on the examined existing theoretical models, a wave diagram of the propagation, reflection and interference of deformation waves caused by the operation of the percussion device along the tacked drilling tool is constructed. Based on the developed diagram, a prediction is made of the nature of the oscillatory processes of the upper end of the drilling tool of a typical design located in a vertical well and the nature of their occurrence is explained. Based on the presented theoretical model the authors made an analysis of records in relative units of the vibration velocity of the upper end of a drilling tool in two specific cases of freeing stuck drilling tools in wells No. 812-Pasichna and No. 903-Pasichna of Nadvirna and Ivano-Frankivsk UBR, where they used VUK-170 that worked in jar mode. For this purpose, the time-frequency representation of the obtained records in the form of spectrogram, scalogram and Wigner-Ville pseudo-distribution was performed, and, based on the obtained theoretical prediction of oscillations of the upper end of the drilling tool, the time of the following stages of the percussion cycle – striking, impact and post – was established. Based on the data obtained, a time-frequency impact assessment was carried out and the character of the attenuation of deformation waves in the drill string was evaluated. Based on the well-known arrangement of stuck drilling tools, the propagation speed of deformation waves along the drill string is determined, which turned out to be more than theoretically calculated for an ideal thin rod according to the wave equation. The paper considers further directions of development of the proposed approach, as well as the use of its results to increase the efficiency of the freeing of stuck tool using impact tools.