Depositional environment interpretation of sand reservoirs in the Niger Delta using porosity and discriminant functions

The accessibility and the worth of hydrocarbons in a reservoir are determined by the sediment deposited in the reservoir. Interpreting the depositional environment of a sand reservoir plays an important role in revealing the volume of appreciable hydrocarbons in the reservoir. Three wells’ data were used for this study. These data were processed and analysed with Microsoft Excel as well as the calculated parameters. The average total porosity estimated were 20.0% [indicating that the reservoir is highly porous; classified as good], 25.1% [showing that the reservoir is highly porous; belongs to the very good class] and 21.5% [signifying that the reservoir is highly porous; classified as good] respectively for wells AA, BB and CC. For well AA, the mean and standard deviation outcomes are 20.5 and 2.525 respectively. The sorting, skewness and kurtosis correspond to extremely poorly sorted, very coarse skew and extremely leptokurtic. For well BB, the mean and standard deviation results are 25.2 and 0.6 respectively. The sorting, skewness and kurtosis results for wells BB and CC correspond to poorly sorted, very coarse skew and very leptokurtic. The mean and standard deviation outcomes deduced from well CC reservoir are 21.0 and 0.75 respectively. The outcomes of the discriminant functions defined reservoir AA as one that has beach and fluvial characteristics with shallow agitated conditions. Wells BB and CC show aeolian and shallow marine with agitated conditions. The very coarse skew definition of sediment arrangement in the reservoirs points to the environment of deposition with high energy; as such the migration of hydrocarbons is faster from the reservoir to the well bore.