Estimation of Petrophysical Properties of Ajali Sandstone in Western Anambra Basin Using Granulometric Analysis
DOI: 10.23977/geors.2019.21001 | Downloads: 5 | Views: 299
Edirin Akpofure 1, Ebiegberi Oborie 1
1 Department of Geology, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
Corresponding AuthorEdirin Akpofure
Most sedimentary deposits have complex regional permeability and porosity variations which can be determined through various methods. The petrophysical properties of Ajali Sandstone such as permeability, porosity, and grain mean diameter were estimated using textural characteristics of the sediment from field data, petrography and grain size distribution. Grain-size distributions of sediment samples were determined by mechanical sieving. The porosity and permeability have been affected adversely by the moderate to poor sorting of grains. Whereas, fracture line, diagenetic imprints such as the solution, alteration and corrosion at grain margins and lack of cement have made the grains friable, thereby, increasing porosity. Sedimentary structures such as the reactivation surfaces and mud drapes which interspace the thick cross-bedded beds form seals which impede permeability. The porosity of the sandstone is very high and ranges mainly from 50% - 70%, with a few above 70%. Whereas, the least estimated permeability is 3.74 m/day and the highest is 724.55 m/day. A very complex variation exist in the permeability of the studied sandstone which may be due to the occurrence of the several large planar, trough and herringbone cross stratification, erosion and pebble lagged surfaces prevalent in the Formation. There is a strong correlation between permeability and porosity and the associated regression equation is expressed, with a correlation coefficient R² = 0.6795. Poor correlations exist between permeability and other grain size parameters such as grain mean diameter, d10 and d60.
KEYWORDSPermeability, Porosity, Grain size distribution, Sedimentary structures, Diagenetic Imprints
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Edirin Akpofure, Ebiegberi Oborie, Estimation of Petrophysical Properties of Ajali Sandstone in Western Anambra Basin Using Granulometric Analysis, Geoscience and Remote Sensing (2019) Vol. 2: 1-24. DOI: http://dx.doi.org/10.23977/geors.2019.21001.
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