Calculation and application of near-surface Q field in Penglai Gas Area,Sichuan Basin
Near-surface absorption attenuation can seriously reduce the resolution of seismic data.Using micro logging data to estimate the near-surface absorption structure,obtain quality factor Q value of surface layer me-dium,and then perform inverse Q filtering compensation can achieve high fidelity and high resolution proces-sing.This paper proposed an improved spectral ratio method for obtaining Q values from micro logging data of a single well and then fitted the relationship between surface layer velocity and Q values to convert the near-sur-face velocity field into a near-surface Q field.Because the surface layer of the Sichuan Basin is thin,the depth sampling interval of the near-surface velocity field by tomographic inversion is 10 meters,which makes it diffi-cult to reflect the surface layer changes that are several meters.Therefore,combined with the multi-shot fitting algorithm for micro logging data of two wells,the equivalent Q value of the shallow surface layer was obtained.Then,the relative Q field of the surface layer was obtained using the amplitude and travel time information of the seismic data.In addition,the absolute Q value obtained from the micro logging data of two wellswas used to calibrate the relative Q field.Finally,the plane Q field of the surface layer was embedded in the shallow layer of the near-surface Q field converted according to the Q-V fitting relationship,and the optimized near-sur-face Q field of the work area was obtained and used for near-surface Q compensation of seismic data,so as to broaden the frequency band and improve the resolution of seismic data.
near surfacequality factor QQ value estimationnear-surface Q fieldSichuan Basin
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