Sedimentological analysis and log-sequence stratigraphy of X-Field, Niger Delta

Sedimentological analyses were carried out on one-hundred and fifteen (115) ditch-cutting samples of depth ranges (6240ft-10020ft) from well-X, in the Central Swamp Depobelt, of the Niger Delta Basin to determine the depositional environment of the sediments. The ditch-cutting samples were analysed using a stereo microscope for the lithologic description, thirty-three (33) samples were identified as sandstone, while the other eighty-two (82) samples were classified as shale. Grain size analysis was carried out using a set of sieves on the thirty-three (33) samples identified as sandstone. The grain size analysis results were visualised in a graphical method from which some simple statistical parameters were derived. The sample description yielded lithologies that are sandstone and shale. The sandstones were found to be fine to medium-grained, poorly sorted to moderately well sorted. They were fine to coarsely skewed with kurtosis values indicating the sandstones were mostly Leptokurtic. The shales were light to dark grey shales controlled by organic content in the shale. This finally produced a lithologic framework of the well. Bivariate plots of the relationships between the graphic statistical moments (mean, median, standard deviation, skewness and kurtosis) revealed that sediments were deposited in a fluvial environment with the samples falling with the river processes with minor to negligible influence from wave and beach processes. Log-sequence stratigraphic analyses of wireline logs revealed five (5) depositional sequences each beginning and ending with a sequence boundary and also containing lowstand, highstand and transgressive parasequences.