Estimating the near-surface Q factors through the enhanced spectral ratio method utilizing data from an uphole survey

Abstract

The quality factor Q is a crucial physical parameter that quantitatively describes the absorption and attenuation characteristics of formation media with respect to seismic waves. Accurately determining the quality factor Q is significant for improving the resolution of seismic data. The near-surface strata is more shallowly buried and less compacted by the overlying layers. Compared to the deeper strata, the near-surface strata absorbs seismic wave energy more strongly, which directly impacts seismic data resolution and Q value calculation. A common method for obtaining the surface Q factor is through the uphole survey, which is known for its simplicity and low cost. However, the accuracy of estimating the near-surface Q factor is compromised due to variations in seismic wavelets and geophone coupling responses, leading to considerable uncertainty in the survey results of near-surface absorption structures. In this study, the impact of actual data and model data on source wavelet differences and geophone coupling response differences was analyzed. A near-surface Q factor estimation method was proposed, grounded in the conventional spectral ratio method, which simultaneously addresses the effects of source wavelet differences and geophone coupling response differences. Field data application from a work area in eastern China demonstrates the effectiveness of the proposed method.