Geophone Magnet

The demand for accuracy and quality in seismic data acquisition is increasing as geophysical exploration technology advances. Broadband, high-fidelity, high signal-to-noise ratio, and high dynamic data are required to identify lithology, fluid, and fractured reservoirs, improving reservoir location, characteristics, connectivity, and, ultimately, oil recovery. A geophone is a specialized sensor that converts surface mechanical vibration into an electric signal-an electromechanical converter that transforms mechanical energy into electrical energy. It is a critical component of the entire seismic data acquisition process. Geophones are classified as electromagnetic induction, piezoelectric ceramic, MEMS, and fiber optics based on their operating principles. The most common type is electromagnetic induction, with the moving coil geophone being the most representative.

Basic Structure and Working Principle

Geophones are classified into two main systems: vibration systems and magnetic circuit systems. The shell is made of cylindrical soft iron, and the midsection houses the magnetic circuit system. This system consists of a magnet and two pole shoes that are attached to the shell. The space between the soft iron shell and the geophone magnet contains the vibration system, which consists of a coil, coil support, and springs that form a floating body. When the geophone is inserted vertically into the ground, it couples with the surface via the shell's tail cone. Surface vibration causes relative motion between the floating body and the shell, leading to relative motion of the coil in the magnetic field, producing an output current signal corresponding to the vibration period. The structure of the underground strata can then be determined through signal processing.

About Geophone Magnets

The geophone magnet, as the product's core component, not only influences the primary indices and parameters of the geophone but also its cost. Different types of permanent magnets provide different geophone characteristics. The magnet's parameters solely determine the air gap flux. The magnetic aftereffect, temperature, electromagnetic interference, and vibration all impact the air gap flux, which can alter the geophone's parameters. While AlNiCo magnets, sintered Samarium Cobalt magnets, and sintered Neodymium magnets have all been used in geophones, cast AlNiCo magnets are still considered the best choice due to their high accuracy, stability, and low cost. Additionally, these magnets have very tight dimensional tolerances.

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