F.A. LUCAS

Hydrocarbon Reservoir Characterization and Evaluation of TOKS Field, Greater Ughelli Depobelt, Niger Delta Basin, Southern Nigeria was carried out with the aim to achieve optimal evaluation and characterization of the reservoirs in wells of TOKS field. The study utilizes an integration of well logs, seismic data, and core data to offer unique insights into the intricate
complexities of subsurface formations.

The materials (data) used for this study includes one (1) SegY 3D seismic, seven (7) well logs and four (4) checkshot from TOK’s well in the TOK’s Field, these were use to generate logs that consist of lithology log (gamma ray log), resistivity log and porosity logs (density, neutron, sonic). The data also included base map and information
used on the sandstone tops and base. The data collected were analyzed using petrophysical and well correlation, ischore thickness map, seismic horizon interpretation, stratigraphic modelling, structural modelling, upscalling and petrophysical method to evaluate and characterize the reservoirs.

The result shows that TOKS 1000 and TOKS 3000 are the reservoir intervals. The
Petrophysical analysis of TOK 1000 for the TOKS wells 14, 15,16,17,18, 19 and 51 shows porosity value of 0.3054, 0.3103, 0.3042, 0.3252, 0.3055, 0.3108, 0.3857, water saturation values of the wells as 0.2750, 0.2645, 0.2788, 0.2521, 0.2684, 0.2638 and 0.2972, the shale volume results shows 0.05, 0.05, 0.04, 0.04, 0.05, 0.07 and the Net to gross (NTG) ratio result shows 0.95, 0.95, 0.95, 0.96, 0.96, 0.95, 0.93. The Petrophysical analysis of TOK 3000 for the TOKS wells 14, 15,16,17,18 and 19 shows porosity value of 0.3491, 0.3121, 0.3135, 0.2993, 0.3353, 0.2881 and 0.3857, water saturation values of the wells as 0.2349, 0.2627, 0.2615, 0.2741,
0.2446, 0.2846 and 0.2972, the shale volume results shows 0.08, 0.05, 0.05, 0.04, 0.08, 0.05 and 0.07 and the Net to gross (NTG) ratio result shows 0.92, 0.95, 0.95, 0.96, 0.92, 0.95 and 0.93. The seismic interpretation (Horizon and seed) of reservoir tops of TOKS 1000 and TOKS 3000 correspond to trough events. Facies models of both TOKS 1000 and TOKS 3000 aid in the determination of Fine sand, Coarse Sand and Shale lithofacies. The seismic interpretation of reservoir tops of TOKS 1000 and TOKS 3000 reveal trough events. Four (4) zones and five (5) layers were delineated in the TOKS wells. Isochore map shows the thickness of TOKS 3000 reservoir zone. The Subsurface map helps us to identify areas with our reservoir. This structural model helps in understanding the reservoir's structural features. The Net To Gross (NTG) value at the reservoir zones ranges from 0.78 to 0.91 for TOKS 1000 and ranges from 0.76 to 0.92 for TOKS 3000. The porosity value at the reservoir zones ranges from 0.28 to 0.39 for TOKS 1000 and ranges from 0.25 t0 0.36 for TOKS 3000. The water saturation values at the reservoir zones ranges from 0.18 to 0.5 and ranges from 0.25 to 0.39. The prospective reservoirs were coarse grained. The overall results shows From the reservoir characterization and evaluation of TOKS Field, Greater Ughelli Depobelt, Niger Delta Basin, Nigeria shows that the evaluated reservoirs have favourable petrophysical characteristics that will lead to excellent production of hydrocarbon from their porespores hence regarded as prospective wells.

One hundred (100) ditch cutting samples from OK-1 well, Greater Ughelli Depobelt, Niger Delta Basin, Southern Nigeria, collected from Research and Development Division of Shell Petroleum Development Company was subjected to lithological analysis with the aim of identifying the lithofacies, lithozones, source rocks and seal or caprocks of the analyzed section of the well. The lithological analysis was carried out between six thousand, one hundred and forty (6140ft) and twelve thousand, seven hundred and forty (12740ft). Various lithofacies, together with their associated mineral units were observed mainly by visual examination, taking note of grain sizes, shapes, color, sorting patterns, presence of plant materials and lignitemstreaks of the samples provided. Results of the lithological analysis yielded two (2) lithofacies, which include shale and sandy shale, with presence of plant materials and streaks of lignite, and as a result six (6) lithozones were established. All the lithofacies within the analyzed section of The well were regarded as potential source rocks, because they satisfied the lithological characteristics of source rocks. Seal or caprocks potential of the analyzed section could not however be totally ascertained, because the shales and sandy shales were not observed to be deposited on a reservoir rock by reason of their stratigraphic position, despite satisfying the lithological characteristics of seal or caprock. The analyzed section 6140ft- 12740ft of the OK-1 well was inferred to be the Agbada Formation (paralic sequence) of the Niger Delta Basin, by reason of depth and lithofacies within the section which are basically shale and lesser percentages of sand particles

One hundred (100) ditch cutting samples from OK-1 well, Greater Ughelli Depobelt, Niger Delta Basin, Southern Nigeria, collected from Research and Development Division of Shell Petroleum Development Company was subjected to lithological analysis with the aim of identifying the lithofacies, lithozones, source rocks and seal or caprocks of the analyzed section of the well. The lithological analysis was carried out between six thousand, one hundred and forty (6140ft) and twelve thousand, seven hundred and forty (12740ft). Various lithofacies, together with their associated mineral units were observed mainly by visual examination, aking note of grain sizes, shapes, color, sorting patterns, presence of plant materials and lignitemstreaks of the samples provided. Results of the lithological analysis yielded two (2) lithofacies, which include shale and sandy shale, with presence of plant materials and streaks of lignite, and as a result six (6) lithozones were established. All the lithofacies within the analyzed section of The well were regarded as potential source rocks, because they satisfied the lithological characteristics of source rocks. Seal or caprocks potential of the analyzed section could not however be totally ascertained, because the shales and sandy shales were not observed to be deposited on a reservoir rock by reason of their stratigraphic position, despite satisfying the lithological characteristics of seal or caprock. The analyzed section 6140ft- 12740ft of the OK-1 well was inferred to be the Agbada Formation (paralic sequence) of the Niger Delta Basin, by reason of depth and lithofacies within the section which are basically shale and lesser percentages of sand particles.

One hundred (100) ditch cutting samples from OK-1 well, Greater Ughelli Depobelt, Niger Delta Basin, Southern Nigeria, collected from Research and Development Division of Shell Petroleum Development Company was subjected to lithological analysis with the aim of identifying the lithofacies, lithozones, source rocks and seal or caprocks of the analyzed section of the well. The lithological analysis was carried out between six thousand, one hundred and forty (6140ft) and twelve thousand, seven hundred and forty (12740ft). Various lithofacies, together with their associated mineral units were observed mainly by visual examination, taking note of grain sizes, shapes, color, sorting patterns, presence of plant materials and lignitemstreaks of the samples provided. Results of the lithological analysis yielded two (2) lithofacies, which include shale and sandy shale, with presence of plant materials and streaks of lignite, and as a result six (6) lithozones were established. All the lithofacies within the analyzed section of The well were regarded as potential source rocks, because they satisfied the lithological characteristics of source rocks. Seal or caprocks potential of the analyzed section could not however be totally ascertained, because the shales and sandy shales were not observed to be deposited on a reservoir rock by reason of their stratigraphic position, despite satisfying the lithological characteristics of seal or caprock. The analyzed section 6140ft- 12740ft of the OK-1 well was inferred to be the Agbada Formation (paralic sequence) of the Niger Delta Basin, by reason of depth and lithofacies within the section which are basically shale and lesser percentages of sand particles.