Seismic waves interacting with rock formations

Unlock Earth's Secrets: How Spectrum Decomposition Revolutionizes Oil Exploration

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Lena Voss in Tech & Innovation April 2025 • 4 min read.

"Dive into the world of seismic data and discover how a cutting-edge technique is helping energy companies find oil hidden beneath the surface, even in complex geological settings."


The quest for oil drives innovation, particularly in exploration techniques. In the B block, flanking the Doba basin in Chad, Africa, the M prospect presented a complex challenge. Traditional methods struggled to accurately map the thickness of reservoir sands, vital for estimating oil reserves. To solve this, energy companies are turning to advanced methods like spectrum decomposition.

Between 2015 and 2016, the D-1, M-1, and M-2 wells were drilled, with M-1 and M-2 successfully striking oil. However, determining the extent and thickness of the reservoir remained challenging. This is where spectrum decomposition came into play, offering a way to interpret the seismic data and understand the reservoir's structure.

The goal was to semi-quantitatively determine the spatial sand thickness distribution of the tested reservoir. By applying spectrum decomposition analysis, the team aimed to resolve uncertainties in traditional seismic interpretation.

Spectrum Decomposition: A New Way to See Underground

Seismic waves interacting with rock formations

Spectrum decomposition works by breaking down seismic signals into their frequency components. It's like analyzing the different colors that make up white light to reveal hidden details. This technique can highlight subtle variations in the subsurface that might be missed by conventional seismic interpretation.

To understand how this works, consider the challenge: The reservoir sands in the M prospect are interbedded with shale, creating a complex geological environment. Traditional seismic interpretation, which often relies on a "wedge model" (where sand thickness is directly related to amplitude), can be misleading in these settings. A dim amplitude, which is when the signal from the oil is weak, can either indicate thin sand or interbedded layers.
Here’s how spectrum decomposition helps:
  • It identifies frequency responses associated with different sand thicknesses.
  • It helps differentiate between thin, interbedded sands and areas of zero sand thickness.
  • It improves the accuracy of reservoir models.
  • It ultimately leads to better estimates of oil reserves.
The team built four 2D geological models representing different sand/shale combinations. They used the P-velocity and density logs from the discovery wells to generate rock properties for each model. These models ranged from a single blocky sand to four thin sands interbedded with shale. By analyzing the seismic response of these models, the researchers developed a better understanding of how spectrum decomposition could be used to interpret the actual seismic data from the M prospect.

The Impact on Oil Exploration

The results from the spectrum decomposition modeling aligned with the drilling results. This confirmation reinforces the reliability of the technique. By integrating spectrum decomposition into their workflow, energy companies can improve their chances of success, reduce exploration costs, and optimize resource extraction. This approach not only helps in identifying potential oil reserves but also in understanding the geological complexities of subsurface environments.

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