Modelling discontinuous well log signal to identify lithological boundaries via wavelet analysis: An example from KTB borehole data

Journal of Earth system science

Amrita Singh1²  Saumen Maiti1²  R K Tiwar2¹ 

[1] CSIR – National Geophysical Research Institute, Hyderbad 500 007, India.$$;Indian School of Mines (ISM), Dhanbad 826 004, India.$$

关键词: Fast Fourier transform (FFT);    continuous wavelet transform (cwt);    discrete wavelet transforms (dwt);    lithological boundary identification;    KTB;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Identification of sharp and discontinuous lithological boundaries from well log signal stemming fromheterogeneous subsurface structures assumes a special significance in geo-exploration studies. Well logdata acquired from various geological settings generally display nonstationary/nonlinear characteristicswith varying wavelengths and frequencies. Modelling of such complex well-log signals using the conventionalsignal processing techniques either fails to catch-up abrupt boundaries or at the best, do notprovide precise information on insidious lithological discontinuities. In this paper, we have proposed anew wavelet transform-based algorithm to model the abrupt discontinuous changes from well log databy taking care of nonstationary characteristics of the signal. Prior to applying the algorithm on thegeophysical well data, we analyzed the distribution of wavelet coefficients using synthetic signal generatedby the first order nonstationary auto-regressive model and then applied the method on actual welllog dataset obtained from the KTB bore hole, Germany. Besides identifying the formation of layeredboundaries, the underlying method also maps some additional formation boundaries, which were hithertoundetected at the KTB site. The results match well with known geological lithostratigraphy andwill be useful for constraining the future model of KTB bore hole data.

【 授权许可】

Unknown