Sedimentological Resolution of Biostratigraphic and Sequence Stratigraphic Evaluation of Toms-well, OG-field, Greater Ughelli Depobelt, Onshore, Niger Delta Basin, Nigeria

Abstract

One hundred and seventy six ditch cutting samples within the interval of 5425ft to 8535ft from Toms-well, OG-Field, Greater Ughelli Depobelt, onshore, Niger Delta basin, were subjected to sedimentological analysis and microscopic analysis using a binocular reflected light microscope and microscopic analysis of palynomorphs and foraminifera using a binocular transmitted light microscope. Textural analysis of ditch cutting samples to build a lithologic model of the penetrated sedimentary succession was established to constrain the alternation of sand packages from proximal to distal. The alternation of shale and sand revealed that the studied intervals belong to paralic Agbada Formation of the Niger Delta basin. The combined results of foraminiferal, palynological and sequence stratigraphy showed that the studied well (Toms-well) was deposited during Oligocene to Early Miocene Epoch of  numerical ages of 31.3MaMfs, 33.0 Mfs and 34.0MaMfs; while 24.3MaMfs and 31.3MaMfs indicated by Bolivina 26 and Uvigerina 5 as diagnostic marker shale with their corresponding SB delineated at 24.9Ma and 32.4Ma. Prospective reservoirs intervals delineated in Toms-well are 6870 ft-6915 ft, 8175-8205 ft and 8265-8340 ft. The P-zones and F-zones established are P560/F7400, P540/F7600 and P520/F7800. Results from the integration of sedimentological, foraminiferal and palynological suggest sediments deposition in marginal marine to shallow marine environments.