FACIES ARCHITECTURE AND RESERVOIR PROPERTIES ESTIMATION OF THE CAMPANIAN-MAASTRICHTIAN DEPOSITS IN ITUKU-OZALLA AREA, ANAMBRA BASIN, SOUTH-EASTERN NIGERIA.
Keywords:
Depositional elements, heterogeneities, Net-to-Gross, Owelli Formation, permeability.Abstract
Facies architecture and reservoir studies were carried out using outcrop data from the Campanian-Maastrichtian
succession in the Anambra Basin, south-eastern Nigeria. This research is aimed at identifying key depositional
elements and their reservoir potential that will give insight into the geometry, continuity and lateral/vertical distribution
of the sandstone bodies, as well as the reservoir qualities of the strata. Four (4) architectural elements identified include;
(i) isolated and amalgamated channel (ii) sandy cross-stratified (iii) floodplain and (iv) heterolithic elements. Reservoir
assessment of the sandstone shows permeability ranges from 7,925 to 160,793 mD while granular parameter ranges
between 10.43 to 211.57 mm2. The strata were not altered by intense diagenesis, so they gave a quantitative reservoir
quality prediction. Studies suggest that net-to-gross varies considerably across the depositional facies ranging from
moderately good to excellent (61 to 100%). In tidal channel deposits, the heterogeneities occur as mud drapes and mud
laminae which act as baffles and barriers. The shales of the Nkporo Group and Mamu Formation act as potential source
rocks while the Owelli Formation of the Nkporo Group acts as potential reservoir rock for the accumulation of
hydrocarbon in the Anambra Basin.
