Evolution of oil-generative window and oil and gas occurrence in Tertiary Niger delta basin/sup 1/

Journal Article · Thu Nov 01 04:00:00 EST 1984 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6199509

Ejedawe, J E; Adoh, F O; Alofe, K B; Coker, S J.L.; Lambert-Aikhionbare, D O

Assuming a simple model of delta development involving progradation and uniform burial at 500 m/m.y. (1,640 ft/m.y.) to present depths, oil-genesis nomographs derived from the time-temperature index (TTI) method were constructed for geothermal gradients ranging from 2.2/sup 0/ to 5.1/sup 0/ C/100 m (1.2/sup 0/-2.8/sup 0/ F/100 ft) of the Niger delta and used in mapping the positions (depth, temperature) of the top of the oil-generative window (OGW) at various times between 40 m.y.B.P. and the present. During the active subsidence phase, oil generation within any megasedimentary unit was initiated at a temperature of 140/sup 0/-146/sup 0/C (284/sup 0/-294.8/sup 0/F) and depth of 3,000-5,200 m (9,843-17,060 ft) within 7-11 m.y. after deposition of the potential source rocks. After cessation of subsidence, vertical upward movement of the OGW by 800-1,600 m (2,625-5,249 ft) was accompanied by a temperature lowering of 23/sup 0/-54/sup 0/C (41/sup 0/-97/sup 0/F), producing correspondingly heavier crudes. In a central belt of the delta, hydrocarbon generation and expulsion from the lower part of the Agbada Formation predate the cessation of subsidence and structural deformation, whereas, in other areas, it postdates the cessation of subsidence and structural deformation. In this central belt, the Agbada is the major oil source, with the Akata serving as a gas source. In the other areas, both the Agbada and Akata constitute oil sources, which implies that the thermal conditions rather than the kerogen type influence the oil/gas mix in the Niger delta basin.

• Research Organization: Department of Geology, University of Benin, Benin City
• OSTI ID: 6199509
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 68:11; ISSN AAPGB
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
ALLUVIAL DEPOSITS
CENOZOIC ERA
DIAGRAMS
FORMATION DAMAGE
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC MODELS
GEOLOGY
GEOTHERMAL GRADIENTS
GEOTHERMOMETRY
GROUND SUBSIDENCE
HIGH TEMPERATURE
MAPPING
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NIGER RIVER
NOMOGRAMS
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
RESOURCES
RIVERS
STREAMS
SURFACE WATERS
TEMPERATURE GRADIENTS
TERTIARY PERIOD