PETROPHYSICAL CHARACTERIZATION OF PETROLEUM RESERVOIRS AND SOURCE BEDS OF THE BATANGA SUB-BLOCK, KRIBI-CAMPO SUB-BASIN, CAMEROON.
Eric Ndonwie Mahbou
Department of Geology and Environmental science, University of Buea.
Composite petrophysical logs including sonic, gamma ray and resistivity are used to estimate the sonic porosity, volume of shale and to identify source beds and hydrocarbon zones for four wells (Kribi F-2 well, Kribi E-1 well, Batanga F-2 well, and Kribi F-1 well) in Cretaceous and Tertiary strata of Kiobe field, Batanga. The elastic properties (Poisson’s ratio, acoustic and shear impedance) and volume-percent of organic matter in sediments are modeled from the porosity and shale fraction estimates, for describing the hydrocarbon reservoir zones and source beds.
Source beds occur predominantly in the Cretaceous Mundeck Formation and to a lesser extent in the Tertiary Matanda Formation. Source rock thickness increases from 89m east-south-east to 416m west-north-west of Batanga. The Matanda Formation consists of relatively organic-poor sediments having volume-percent organic matter of 1 to 22% with an average of 10.6 %. The Mundeck shales are richer in organic matter with 3 to 22% with an average of 13.1% (where the boundary between organic-rich and organic-poor facies is defined as 2% organic content by volume). The major hydrocarbon-saturated reservoirs occur within the Mundeck Formation. The reservoirs west-north-west are typically turbidite facies with higher mean porosities (0.124 to 0.299), relative to channel deltaic distributary, and interdistributary sandstone reservoirs in east-south-eastern area with mean porosities between 0.123 to 0.275. Gas hydrate zones of the Mundeck Formation are identified by the low Poisson’s ratio (0.03 to 0.08), high acoustic impedance (21.47 to 16.16km/s g/cc) and high shear impedance (14.92 to 10.89km/s g/cc) of the beds.
AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid