65 / 2023-05-18 10:58:01

Study on effective extraction radius of directional long borehole and analysis of influencemechanism

directional long drilling; effective extraction radius; negative pressure at the orifice;drilling diameter;

In order to accurately determine the effective extraction radius of directional long drilling, the influence of negative pressure of the hole mouth, the drilling diameter and the drilling length of the hole on the effective extraction radius of the directional long drilling hole is simulated by establishing a coal-to-gas gas-structure coupling model considering the Klinkenberg effect. Finally, the reliability of the numerical simulation was verified by field testing in Yuxi Coal Mine. The results show that the attenuation of negative pressure in the directional long borehole along the long hole has a great influence on the gas extraction effect. When the negative pressure of extraction decays along the direction of hole length, the radial gas pressure of the extraction drilling hole is distributed in a "V" shape. The greater the negative pressure of the hole and the diameter of the drilling hole, the better the gas extraction effect. When the negative pressure of extraction is attenuated along the long hole direction, the effective extraction radius is exponentially related to the drilled hole depth. The negative pressure of the hole and the diameter of the borehole are linearly related to the effective extraction radius at the bottom of the borehole. Through field tests, when extracting 180 days based on the stubble pressing effect, the effective extraction radius of the directional long borehole of the No. 3 coal seam of Yuxi Coal Mine was 5.7 m, and the absolute error between the numerical simulation was 0.1 m. At the same time, the gas pressure obtained from different sampling points is consistent with the numerical simulation, and the relative error is 0.3 to 4.1%. The research results provide a theoretical basis for the rational layout of directional drilling.