A Review of Hydrocarbon Prospects in the Lower Benue Trough Nigeria: Another Insight from Potential Field Study

Onuba, Leonard N.; Onwuemesi, Godwin A.; Egboka, Boniface; Anudu, Goodluck K.; Omali, Aurelius

The lower portion of the Nigerian Benue Trough is a failed rift structure resulting from the separation of South American continent from the African continent in the Aptian. Previous geochemical and well-log evaluations for hydrocarbon in the trough revealed a number of organic rich intervals capable of yielding significant quantities of hydrocarbons in the Cretaceous sediments.

This study is a contribution to the previous evaluations and updates previous geophysical study in relation to potential field data. This was achieved by determining sediment thickness distribution, identifying areas with adequate geothermal gradients, delineating sediment - basement boundary, and estimating crustal thickness variation within the Lower Benue Trough.

Spectral analysis techniques were used to evaluate aeromagnetic anomalies of Afikpo - Ogoja axis of the Lower Benue Trough, covering about 27,225 square kilometres of the area. On the average, depth to the basement trough varies from 100m to less than 1680m for shallow magnetic sources while for deeper sources varies from 1870m to less than 3980m.

These results reveal sedimentary cover to be relatively low except for parts of Asu River Group, Ezeaku Formation, Awgu Formation, and Nkporo Formation. The crustal thickness on the average varies from about 10km at Afikpo area to less than 25km at Obolo Eke - Abakaliki Axis.

These results show the study area may likely be composed of mainly continental magnetised crust. Three zones of geothermal gradient were identified and these are: 16 - 280C/km for zone of low geothermal gradient, 28 - 420C/km for zone of intermediate geothermal gradient, and 42 - 580C/km for zone of high geothermal gradient. The parts of Asu River Group, Ezeaku Formation, Awgu Formation, and Nkporo Formation that fall within the zone of intermediate geothermal gradient, lie within the oil generating window.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013