Frequency Attribute Analysis at Euchis Field, Niger Delta, South-Southern Nigeria for Structural and Hydrocarbon Delineation

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International Journal of Research and Innovation in Applied Science (IJRIAS) |Volume VIII, Issue III, March 2023|ISSN 2454-6194

 Frequency Attribute Analysis at Euchis Field, Niger Delta, South-Southern Nigeria for Structural and Hydrocarbon Delineation

 Egwuonwu, Gabriel Ndubuisi1*, Anigbogu, Eucharia Oluchukwu1, Didi, Chekwube Nnamdi2
Ibe, Stephen Onyejiuwaka3 and Ezeobi, Chika Franklin1
1Department of Physics and Industrial Physics, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria
2Department of Ecology and Natural Resources Management, Peoples’ Friendship University (RUDN) Moscow, Russia.
3Department of Physics, Federal University Otuoke, Bayelsa State, Nigeria
*Corresponding Author
Received: 11 March 2023; Accepted: 15 March 2023; Published: 11 April 2023

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Abstract: – Aimed at enhancing hydrocarbon exploration in the Niger Delta, Nigeria; structural interpretation of at Euchis field was undertaken by analysing the frequency attribute of the reservoirs therein. Schlumberger’s Petrel 2017 software was used for data processing and interpretation of the field’s Well logs. In order to facilitate the lithostratigraphic interpretation of the field, seismic-to-well tie was carried out using three dimensional 3D seismic data provided. Seismic attribute analysis and prospects identification were carried out for structural analysis. Lithostratigraphic interpretation shows that the Euchis field is predominantly characterized by sand-shale interbeddings. The frequency attributes map analysis indicated three distinct reservoirs with frequency ranges of ≈ -9 to 48 Hz, ≈ -9 to 51 Hz and ≈ -6 – 54 Hz respectively. Based on the inverse proportionality between the thicknesses of rock layers in the subsurface and peak frequencies of the seismic reflection, the lower frequency were delineated as indicators of hydrocarbon occurrence at the field. Lithologic correlation at the field showed that the occurrence of the Basin within the Euchis field fall within the depth range of 2500 m and 3360 m and the presence of intra-reservoir seals. The structural analysis revealed occurrences of normal, listric, regional and minor faults at various depths. The regional faults were observed to have cut across the three reservoirs, forming a conduit for hydrocarbon migration; whereas the minor faults serve as traps within the second and third reservoirs. The other faults were observed to have a predominant trend in northnorth-west south-south east direction.

Keywords: lithological facies, seismic frequency, amplitude, faults, hydrocarborn migration, hydrocarbon traps, hydrocarbon prospective zones

I. Introduction

The approach of seismic attributes interpretation is an integral part of seismic interpretation projects for over about five decades now. Analyses of amplitude, average reflection strength and spectral decomposition are very useful tools for locating reservoir quality, outlining their geometry and displaying lateral changes in thickness of structures (Ryan, 2007). In recent times, seismic attributes has widened its lithological and petrophysical predictions of reservoirs (reservoir characterizations). Particularly, the application to hydrocarbon exploration is broadened extensively (Brown, 2004). Frequency attributes analysis is the most vital methods involved in seismic decomposition which involves separation and classification of seismic events within each seismic signal trace based on their frequency content (Sheriff, 2002).

Basically, it is known that during the propagation of elastic waves, loses energy occur due to spherical divergence, scattering, intrinsic absorption and reflection at rocks interfaces. The loss of energy also uniquely influences variations in amplitude and frequency responses of reflected seismic waves. Particularly, the major factors which lead to the significant changes in frequency includes; geologic structures, layer thicknesses, lithology and pore fluid properties among others. Arrivals of seismic p-waves and s-waves provide the exploration Seismologist useful information about the characteristic frequency responses. The responses are utilized for delineating the stratigraphic features, rocks properties changes and fluid accumulations and properties discriminating it from their surrounding environment.