Complex frequency domain seismic inversion method for well-free area based on geological model

For model-based inversion methods，a reasonable initial model can not only compensate for the missing low-frequency seismic information but also improve the accuracy and stability of seismic inversion. However，in areas with no or few wells，geophysical inversion is faced with the problem of lack of data and low data quality，which makes it difficult to obtain abundant low-frequency information directly from the well data. Therefore，obtaining a low-frequency model is the key to geophysical inversion and reservoir characterization in the well- free area. In view of this，a complex frequency domain seismic inversion method for a well- free area based on a geological model is explored for the new exploration area. Firstly，by considering the influence of faults and referring to the seismic facies to guide the macro trend qualitatively，the relative change of the low frequency of the trace integral is integrated，and the geological and seismic data of the well-free area are fully used to provide reliable low-frequency information for the inversion of the well-free area. Then，the low-frequency information of seismic data is mined according to the complex frequency domain inversion，and the well-free initial model is used as the low - frequency model for the complex frequency domain inversion. The seismic blind wavelet is extracted according to the blind signal theory，and the well-free low-frequency model in the complex frequency domain can be obtained to supplement the low - frequency information，which can alleviate the problem of missing low-frequency components of the seismic inversion in the well-free area to a certain extent. Finally，the effect of the new method is tested by using the model and actual working area data. The results show that the elastic impedance curves of the well-free inversion in the complex frequency domain are well fitted with the borehole elastic impedance curves. Compared with the sparse pulse inversion results with well，although the local accuracy is slightly lower，the general trend and reservoir distribution characteristics of the well-free inversion results in complex frequency domain are basically consistent with those of the borehole inversion results，which proves the effectiveness of the proposed method in the well-free area. © 2024 Editorial office of Oil Geophysical Prospecting. All rights reserved.