Abstract
Sedimentological study and petrographic analyses were carried out on thirty ditch cutting samples from well-S, Niger Delta, Nigeria, with the aim of determining the provenance and depositional environment of the sediments. The samples were subjected to soxhlet extraction for the removal of soluble organic matter from them and particle size analyses using Pipette and Emery sedimentation techniques in order to determine the grain size distribution of the sediments. Separation of heavy of mineral from the samples was done with the aid of bromoform to enable petrographic analyses of the heavy mineral suite, under the polarising microscope. The data obtained from the grain size analysis were used in preparing histograms, from which some simple statistical parameters were derived. Graphic mean values obtained range between 0.74 and 2.64 O, which implies that the sediments are predominantly fine-medium grained. The inclusive standard deviation values ranges from 0.53 to 1.24 O, indicating that the sediments are moderately well sorted to moderately sorted. Inclusive graphic skewness values of 0.29 to 0.70 indicate that the sediments ranges from finely skewed to strongly finely skewed and the graphic kurtosis values of 0.61 to 1.54 shows that the sediments are predominately very platykurtic which implies a low energy environment of deposition. The polymodal nature displayed by the histograms indicates that the sediments have been derived from various sources. The study concluded that the sediments were deposited in a fluvial environment. It also established that the sediments originate from metamorphic and acid igneous rocks of the Nigeria Basement Complex and mineralogically mature to sub-mature.
Highlights
Sediments are derived from the pre-existing rocks that have been weathered, transported and deposited in basins.The Niger Delta is one of the depositional basins in Nigeria and it has been accommodating sediments since the Paleocene.The understanding of the sedimentary processes most importantly the environmental factors that have influence on the weathering, transportation, deposition and subsequent modification of the sediments are crucial in knowing their source and reconstructing the environment in which they were
The Niger Delta has been extensively studied by various workers, as regard the provenance of the sediments, heavy mineral suit and depositional environment (NERDECO (Netherlands engineering consultant, 1959 [1]); Evamy et al, 1978[2]; Adedokun 1981[3]; Mateawo 1995[4]), there is paucity of information on sedimentological and heavy mineral studies of sediments from deepwater wells in the Niger Delta
It has been noted by Friedman and Sanders (1978)[14] that opaque minerals typically predominate in a heavy mineral suite
Summary
Sediments are derived from the pre-existing rocks that have been weathered, transported and deposited in basins.The Niger Delta is one of the depositional basins in Nigeria and it has been accommodating sediments since the Paleocene.The understanding of the sedimentary processes most importantly the environmental factors that have influence on the weathering, transportation, deposition and subsequent modification of the sediments are crucial in knowing their source and reconstructing the environment in which they were. Sediments are derived from the pre-existing rocks that have been weathered, transported and deposited in basins. The Niger Delta is one of the depositional basins in Nigeria and it has been accommodating sediments since the Paleocene. The understanding of the sedimentary processes most importantly the environmental factors that have influence on the weathering, transportation, deposition and subsequent modification of the sediments are crucial in knowing their source and reconstructing the environment in which they were. The aim of the present work is to study the sedimentological properties of sediments from two deepwater Niger Delta wells penetrated in the sequence and subsequently establish the provenance and environment of deposition of the sediments The Niger Delta has been extensively studied by various workers, as regard the provenance of the sediments, heavy mineral suit and depositional environment (NERDECO (Netherlands engineering consultant, 1959 [1]); Evamy et al, 1978[2]; Adedokun 1981[3]; Mateawo 1995[4]), there is paucity of information on sedimentological and heavy mineral studies of sediments from deepwater wells in the Niger Delta.
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