Abstract: The present application provides a device for detecting a defect in a steel cord ply. The device is configured to obtain an enhanced magnetic field signal of the steel cord ply and detect a defect of the steel cord ply based on the enhanced magnetic field signal. The device includes a magnetic field unit including a permanent magnet configured to generate a background magnetic field; a signal obtaining unit configured to generate an enhanced magnetic field signal of a steel cord ply based on a plurality of first magnetic field signals and a plurality of second magnetic field signals; and a defect detecting unit configured to detect a defect of the steel cord ply based on the enhanced magnetic field signal, wherein the defect detecting unit includes an AD converting module, a signal processing module, a defect detecting module, a display module, and a control module.

Abstract: An exploitation method and an exploitation well pattern for coalbed methane in a low-permeability coalbed. The method comprises: determining a maximum principal stress direction in a low-permeability coalbed; disposing at least two large-roadway horizontal wells in the low-permeability coalbed; disposing a plurality of production wells on two sides of a horizontal segment of each of the at least two large-roadway horizontal wells, wherein a diameter of each of the production wells is smaller than a diameter of the horizontal segment; exploiting the coalbed methane in the low-permeability coalbed through the at least two large-roadway horizontal wells and the plurality of production wells. Through the horizontal segments of the large-roadway horizontal wells perpendicular to the maximum principal stress direction, it promotes stress release in low-permeability coalbed to form more fracture channels, thereby improving the exploitation efficiency of the coalbed methane in the low-permeability coalbed.

Abstract: The present disclosure discloses an exploitation method and an exploitation well pattern for coalbed methane in a low-permeability coalbed. The method comprises: determining a maximum principal stress direction in a low-permeability coalbed (1); disposing at least two large-roadway horizontal wells (3) in the low-permeability coalbed (1); disposing a plurality of production wells (4) on two sides of a horizontal segment (31) of each of the at least two large-roadway horizontal wells (3), wherein a diameter of each of the production wells (4) is smaller than a diameter of the horizontal segment (31) of the large-roadway horizontal well (3); exploiting the coalbed methane in the low-permeability coalbed through the at least two large-roadway horizontal wells (3) and the plurality of production wells (4).