Abstract: According to the “Technical Specification of Seismic Data Interpretation” (GB/T 33684-2017), oilfield companies use the accuracy of well–seismic depth errors as an important indicator for assessing the precision of seismic interpreted structure results. There are two problems during the implementation process. Firstly, the absolute error and relative error accuracies are artificially specified in the national standard, lacking certain theoretical basis and technical support, which has a low operability in actual practice; Secondly, oilfield companies have established corresponding enterprise standards, with the continuously higher accuracy requirements of well seismic–depth errors far exceeding the vertical seismic resolution. Based on the practice of oil and gas exploration in Sichuan Basin, four main controlling factors that affect well–seismic depth errors are deeply analyzed, including (1) migrated imaging methods; (2) velocity errors in variable-speed depth conversion; (3) horizon calibration; and (4) vertical resolution of seismic exploration. The absolute error of well–seismic depth is related to the magnitude of the longitudinal resolution wavelength λ in seismic exploration. Therefore, based on the wavelength theory of vertical resolution in seismic exploration, and targeted at various exploration stages (exploration, appraisal, development, and fine development) of oil fields, different fractional values of seismic wavelength (λ_n and K_λn) can be taken as important reference indicators for the absolute and relative errors of well–seismic depth, which is operable in practice and can be used as a reference for oil field managers to assess the accuracy of seismic interpreted structure results.

Key words: well–seismic depth error, main controlling factors, standard, absolute wavelength error, relative wavelength error