Verification of bright spots in the presence of thin beds by AVO and spectral analysis in Miocene sediments of Carpathian Foredeep

Abstract

Twin structural traps that lie within the Miocene strata of the Carpathian Foredeep that are localized above Cierpisz and Mrowla-Bratkowice highs exhibit identical bright-spot seismic anomalies, but only those associated with the Cierpisz high are profitable gas reservoirs. Bright spots can be a result of weak gas or water saturation, but also seismic interference known as tuning effect. For these reasons, it is crucial to differentiate between seismic anomalies. In this article, we present the possibilities of verification of seismic anomalies that occur within the siliciclastic Miocene sediments of the Carpathian Foredeep with the application of AVO analysis and spectral decomposition. AVO methodology enabled to limit the number of anomalies that are present in the post-stack seismic data. These anomalies, however, may also be a result of tuning which is common for the heterolithic sequences in the Miocene sediments of the Carpathian Foredeep. For classification of anomalies in the view of the above, spectral decomposition based on the Basis Pursuit algorithm was applied. Spectral decomposition enabled to divide AVO anomalies in those that are the result of gas saturation and the tuning effect. Gas-saturated zones are characterized by higher spectral amplitudes of the lower frequency range, whereas tuning effect yields higher spectral amplitudes for the higher frequency content. This relation is visible for the data set and enables qualitative differentiation for the set of seismic anomalies.

Estimation of Shallow Sulphur Deposit Resources Based on Reflection Seismic Studies and Well Logging

“…The variable morphology of the basement (numerous faults and uplifts) causes facial differentiation of the Miocene formations. The Miocene formations are overlain from the south by the Carpathian Flysch formations, and they are partly folded at the edge of the Carpathian overthrust [24,25]. The Miocene formations include the Badenian and Sarmatian deposits [26].…”

Shallow Seismic Refraction Tomography Images from the Pieniny Klippen Belt (Southern Poland)

“…Seismic refraction tomography was widely employed in the late 1980s and early 1990s, mainly for the investigation of deep crustal structures [24]. Over time, seismic refraction was adapted for near-surface geophysics, and seismic reflection profiling has become the main method for deeper investigations [25][26][27]. Today, SRT is an established near-surface investigation method used in environmental and engineering studies [28].…”

Homogenization of Porous Thin Layers With Internal Stratification for the Estimation of Seismic Reflection Coefficients

“…Thin layers commonly exhibit heterogeneous structures (e.g., Hussain et al., 2023; Li et al., 2020), such as internal stratification (Figure 1a), which, in turn, govern their effective seismic response. Pertinent applications of reflectivity studies on thin layers are, for instance, the characterization of gas‐bearing beds (e.g., Cichostȩpski et al., 2019; Shakir et al., 2022) as well as the monitoring of carbon sequestration (e.g., Williams & Chadwick, 2012; Zhang et al., 2013). Current methodologies to estimate the rock properties of thin layers have been largely developed within the elastic framework (e.g., Huang et al., 2016; Puryear & Castagna, 2008; Romdhane & Querendez, 2014; Rubino & Velis, 2009; Zhang et al., 2013).…”