GEOPRESSURE ANALYSIS AND RESERVOIR FLUID DISCRIMINATION IN A CENTRAL SWAMP FIELD, NIGER DELTA, NIGERIA.

Nwozor, K.K and Onuorah, Loretta O. (2014) GEOPRESSURE ANALYSIS AND RESERVOIR FLUID DISCRIMINATION IN A CENTRAL SWAMP FIELD, NIGER DELTA, NIGERIA. Petroleum & Coal, 56 (2). pp. 124-140. ISSN 1337-7027

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Abstract

Significant discrepancies often exist between measured and predicted pore pressures especially in deep-seated reservoirs in the Niger Delta Basin. The associated risks when not properly considered contribute to drilling challenges and some exploration downturns. At the background to these challenges is the vague understanding of the subtle complexities that may characterize the geopressure system. Key to this is the growing need to account for additional mechanisms of overpressure generation beyond the routinely believed undercompaction during pressure prognosis and well planning. Data from a deep well in the Central Swamp Depobelt depict the occurrence of two vertical effective stress regimes. The corresponding two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings two pressure settings are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive are separated by massive succession of succession of succession of succession of succession of succession of succession of succession of succession of succession of succession of succession of succession of succession of shaleshaleshaleshaleshales at at at an an an approximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth ofapproximate depth of 14500ft (4421m) towards the base of the Agbada Formation. Cross-plots of density and velocity as well as velocity and vertical effective stress indicate that undercompaction dominates pressure generation above the massive shale while load transfer processes, especially hydrocarbon generation could be responsible for deep-seated extreme overpressures. The intervening massive shale acts as an effective regional seal with the result that there is no pressure communication between the reservoirs above and beneath it. Calculated overpressures in the water-saturated section of the reservoir that lies above the seal typically were below 150 psi (1.03MPa). On the contrary, overpressure beneath the seal is as much as 4490psi (30.96MPa). Pressure prediction based on standard Eaton method failed to produce matching profile with measured data in the deep reservoir. Modified Eaton and Bowers methods were then used to obtain a geopressure profile consistent with wireline measurements.

Item Type:	Article
Subjects:	L Education > L Education (General) Q Science > Q Science (General)
Divisions:	Faculty of Natural and Applied Sciences
Depositing User:	miss ifeoma agbo
Date Deposited:	02 May 2019 14:23
Last Modified:	02 May 2019 14:23
URI:	http://eprints.gouni.edu.ng/id/eprint/1437

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