Application of intelligent direct push measurement while drilling device for environmental geological surveys

In order to solve the technical challenges of inaccuracy and poor credibility of contaminant survey results due to the low accuracy of drilling trajectories in environmental geological surveys, the structural and functional characteristics of the existing direct-push drilling tools were analyzed. On this basis, the method of near-bit measurement while drilling using single-action combination was proposed. An intelligent measurement-while-drilling (MWD) device was developed, a laboratory platform monitoring module was established, a set of monitoring software was developed, and the stability and reliability of the intelligent MWD device was analysed. Then, verification tests have been carried out on the laboratory platforms and in the field separately. The results of the study show that the intelligent MWD device is characterized by lightweight and modular, with an overall length of 300 mm. The device has a stable measurement performance with an accuracy up to 0.01° for the drift angle, azimuth and tool face angle, which can meet the requirements of direct-push drilling guidance, and the single action of the inner tube greatly reduces the disturbance to the sites. Besides, the MWD device can automatically recognize the drilling status at different drift angle thresholds and it is well adapted to the conventional drill pipes, thus suitable for a wide range of direct push drilling scenarios. During the three direct-push drilling processes in the field test, the MWD device showed high stability and allowed continuous direct push drilling at a speed of 1.5 m/min. Generally, the device is capable of meeting the needs of MWD during the direct-push drilling in environmental surveys and provides the equipment basis and data support for the adjustment of the direct-push drilling trajectory. Moreover, the research results are of great significance to improve the accuracy of the direct-push drilling trajectory under non-homogeneous conditions, enhance the credibility of in-situ detection of contaminants in environmental geological surveys, and promote the level of intelligent drilling and surveying integrated technology and equipment for environmental geological surveys.