INTEGRATED SEISMIC VELOCITY ANOMALY AND ANAEROBIC MICROBIAL GAS GENERATION STUDY FOR THE DELTA NORTH SENATORIAL DISTRICT, SOUTHERN NIGERIA
DOI:
https://doi.org/10.60787/tnamp.v25.718Keywords:
The biogenic methane, seismic velocity anomaly, low-velocity zone, Delta, anaerobic methanogenesisAbstract
Formations favourable to the generation of methane include the Benin, Agbada and Akata Formations in the Delta North Senatorial District of Southern Nigeria. This study is the first to analyze the region geophysically and microbiologically together with different techniques such as seismic refraction and gas chromatography. The velocities of the weathering layers varied from 310 to 445 m/s, and the depths were from 4.2 to 8.4 m. Up to 18% decrease in compressional velocity was noted in the Agbada Formation and identified as significant low velocity zones. The saturations in these zones, as determined from gas saturation models, were 38-68%. A biogenic subsurface gas was observed in geochemical analyses, the TOC (Total Organic Carbon) content in the samples ranged from 1.88 to 6.80 wt%. The spatial analysis revealed the presence of an area of about 802 km2 of low velocity zones and showed that seismic velocity is a good indicator of mapping the microbial gas-rich zones, which would aid in better assessment of geohazard and environmental monitoring.
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