Layer-thickness determination and stratigraphic interpretation using spectral inversion: Theory and application

Abstract

Spectral inversion is a seismic method that uses a priori information and spectral decomposition to improve images of thin layers whose thicknesses are below the tuning thickness. We formulate a method to invert frequency spectra for layer thickness and apply it to synthetic and real data using complex spectral analysis. Absolute layer thicknesses significantly below the seismic tuning thickness can be determined robustly in this manner without amplitude calibration. We extend our method to encompass a generalized reflectivity series represented by a summation of impulse pairs. Application of our spectral inversion to seismic data sets from the Gulf of Mexico results in reliable well ties to seismic data, accurate prediction of layer thickness to less than half the tuning thickness, and improved imaging of subtle stratigraphic features. Comparisons between well ties for spectrally inverted data and ties for conventional seismic data illustrate the superior resolution of the former. Several stratigraphic examples illustrate the various destructive effects of the wavelet, including creating illusory geologic information, such as false stratigraphic truncations that are related to lateral changes in rock properties, and masking geologic information, such as updip limits of thin layers. We conclude that data that are inverted spectrally on a trace-by-trace basis show greater bedding continuity than do the original seismic data, suggesting that wavelet side-lobe interference produces false bedding discontinuities.

Reflection and transmission coefficients of a thin bed

“…These parameters can be used in estimation of thin-bed thicknesses (Liu and Marfurt, 2006;Puryear and Castagna, 2008). Under the assumption that the middle layer is thin, equation 1 for thin-bed reflection-transmission coefficients is simplified into a relatively simple form, which is similar to the Zoeppritz equations.…”

Low-frequency seismic analysis and direct hydrocarbon indicators

“…The CWT is essentially equivalent to a narrow-band filtering of the data in the temporal domain (Puryear and Castagna, 2008). In practice, the CWT has higher frequency resolution for low frequencies and better time resolution for higher frequencies (Chakraborty & Okaya, 1995).…”

“…Spectral decomposition is a seismic analysis technique that decomposes seismic data into the time-frequency domain, which often contains useful information for layer thickness estimation, stratigraphic interpretation (Puryear and Castagna, 2008), and hydrocarbon indication (Castagna et al, 2003;Sinha et al, 2005).…”

Application of spectral inversion and fuzzy logic interpolation in post-stack resolution enhancement on a seismic volume of the Colombian llanos basin

“…A interpretação de três mapas sísmicos a diferentes tempos ("time slices") permitiu inferir ambientes de formação que foram validados com informação de poço. P ara mejorar la interpretación estratigráfica de datos sísmicos 3D se procuró aumentar la resolución vertical mediante una inversión espectral (Puryear & Castagna, 2008;Qiu, Junhua, Xiaohui, Hu, & Lei, 2016) y la resolución lateral usando una interpolación de lógica difusa (Souverville et al, 2015). La inversión espectral mediante algoritmo genético y la interpolación se implementaron en Matlab®, y se probaron en datos sintéticos así como en una imagen digital de alta resolución, donde ambos algoritmos demostraron un buen desempeño.…”

“…isando melhorar a interpretação estratigráfica de dados sísmicos 3D procuramos aumentar a resolução vertical mediante uma inversão espectral (Puryear & Castagna, 2008;Qiu, Junhua, Xiaohui, Hu, & Lei, 2016) e a resolução lateral empregando uma interpolação de lógica difusa (Souverville et al, 2015). A inversão espectral mediante algoritmo genético e a interpolação foram implementadas em Matlab®, sendo testadas em dados sintéticos, bem como na imagem digital de alta resolução, onde ambos algoritmos demostraram um bom desempenho.…”