A method and device for measuring the quality factor of near-surface formations

Abstract

The invention discloses a method and device for measuring a quality factor of a near-surface stratum, and belongs to the technical field of petroleum seismic exploration. The method comprises the steps of respectively determining frequency spectrums of seismic waves detected by a first detector and a second detector, wherein the first detector and the second detector are respectively arranged at the bottom and the mouth of a reception well, the seismic waves are excited by an excitation point arranged at the bottom of an excitation well, the depth of the excitation well is greater than the thickness of a low-velocity layer, and the depth of the reception well is less than the thickness of the low-velocity layer; determining a frequency spectrum of seismic waves detected by a plurality of third detectors; and determining a quality factor of the near-surface stratum based on the frequency spectrums of the seismic waves respectively detected by the first detector, the second detector andthe plurality of third detectors. The depth of the reception well is less than the thickness of the low-velocity layer, so that the interference caused by strong reflection of a bottom interface of the low-velocity layer for the seismic waves is avoided, and the seismic wave detection accuracy of the detector is improved.

Description

technical field [0001] The invention relates to the technical field of petroleum seismic exploration, in particular to a method and device for measuring the quality factor of near-surface strata. Background technique [0002] The near surface generally has a layered structure, mainly including a low-velocity layer, and the low-velocity layer may also include a low-velocity layer and an underlying formation of the low-velocity layer, wherein the underlying formation of the low-velocity layer is located below the low-velocity layer. Because it is easily affected by weathering and denudation, the near-surface has a strong absorption and attenuation effect on seismic waves, which seriously affects the penetration depth and resolution of seismic waves. Therefore, it is necessary to measure the near-surface formation quality factor in order to According to the formation quality factor, the absorption and attenuation of seismic waves near the surface are compensated. [0003] In t...

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Problems solved by technology

[0005] However, when the quality factor of the near-surface formation is measured by the dual-well micro-logging technology, the low-velocity layer bottom interface has a strong reflection effect on the seismic wave, that is, it is easy to produce ghost reflections, which leads to the reception of the geophone at the bottom of the receiving well. Seismic waves cause disturbance

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