A study of sedimentary facies,mineral and textural characteristics of sections of conglomerates/pebbles and sandstone facies found within the Lokoja and Patti Formations in southern Bida Basin,Nigeria,is carried out t...A study of sedimentary facies,mineral and textural characteristics of sections of conglomerates/pebbles and sandstone facies found within the Lokoja and Patti Formations in southern Bida Basin,Nigeria,is carried out to evaluate the paleo-environment and reservoir quality of the sandstones of the formations through field observations and textural and mineralogical(using X-Ray Diffractogram)analyses.Nine lithofacies are identified and grouped into three main facies associations.These sedimentary facies suggest deposition in both foreshore and estuaries.The mineral analysis(XRD)shows that the quartz content in sandstone facies of the Lokoja Formation ranges between 49%and 67%,and that of the Patti Sandstone between 43%and 56%,indicating a quartz dominance.The granulometric studies reveal that the Lokoja Formation comprises coarse-to medium-grained(-0.63 to 1.30φ)sandstone with moderatepoor sorting of 0.72e1.824.On the other hand,medium to fine-grained sandstones dominate the Patti Formation,which is averagely poorly sorted(1.29-1.54φ).The sandstones are coarsely skewed to finely skewed,with the kurtosis ranging from very platykurtic to leptokurtic.Morphological results of the pebbles from both Lokoja and Patti Formations indicate that the study areas are mainly characterized by the interplay of both wave and fluvial processes,which suggests that the environment of deposition of sandstone facies is predominantly of the fluvial to the shallow marine environment with the indication of tidal influence.Integrating sedimentary facies and textural results suggests subtidal sand ridge/foreshore,estuarine mudflat,and estuarine delta environments with fluvial influences.Evidence from the textural and mineral characteristics indicate that the sandstone facies of the Lokoja and Patti Formations are fairly matured and can act as potential hydrocarbon reservoirs in the formations.The facies,XRD mineral,and textural results have revealed potential hydrocarbon reservoir areas and paleo-depositional features of the Lokoja and Patti Formations.展开更多
An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of grou...An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of groundwater within these two studied locations. The dissolved organic carbon content of water is an important component of the geochemical cycling of elements capable of affecting groundwater quality. The sediments which serve as a conduit and pathways for the elements’ transport depending on the characteristics of the particle sizes are to be considered in the evaluation of contaminant mobility within the pathways. Representative cored sediment samples were collected and their particle size characterization and chemical analysis for Organic Matter (OM), Organic Carbon (OC) and Moisture Content (MC) were carried out. The hydrometer results show that the sediment particle sizes are in the order of sand > clay > silt in both locations with few exceptions. This represents the geology of the area (sandstone). The Mean values of 1.14% and 1.98% of OC and OM respectively were recorded in the sediment samples collected in parts of Ebgako. In contrast, 1.72% and 2.97% mean values were recorded in sediments collected in part of Bida for OC and OM respectively. The values of the OC and OM in the sediments from the two wetlands are low and may have been dissolved along the groundwater pathways to the aquifer. Other physicochemical parameters analysed in the sediments showed poor correlation. OM and OC were strongly positively correlated and showed an R<sup>2</sup> value of 1 and 0.9 respectively for parts of the Bida and Egbako sheets. There is low acidity of the sediments from the two study locations with a mean pH value of 5.64 and 5.13 respectively for Egbako and Bida. The low acidic nature of the sediments and the OM and OC composition have the potential to influence biogeochemical processes in the sediments and can affect the chemical quality of the groundwater in these two study locations.展开更多
Detailed fieldwork carried out in the southern part of Bida Basin, Nigeria, allowed the documentation of soft sediment deformation structures (SSDS) in the Maastrichtian Patti Formation. The aim of this study is to ex...Detailed fieldwork carried out in the southern part of Bida Basin, Nigeria, allowed the documentation of soft sediment deformation structures (SSDS) in the Maastrichtian Patti Formation. The aim of this study is to examine the sedimentary successions, describe and analyse these deformation features, discuss their deformation mechanisms and potential triggers. The Maastrichtian Patti Formation is composed of lithofacies interpreted to have been deposited in tidal and fluvial sedimentary environments. Soft sediment deformation structures recognised in the tidal sediments were clastic dykes, load cast, isolated sand balls, dish-and-pillar structures, convolute lamination, diapiric structures and recumbent folds. Severely deformed cross beds, ring structures, associated sand balls, normal folds and recumbent folds were identified in the fluvial sediments. SSDS recognised were interpreted to have been caused by effects of liquefaction and fluidization. Field observations, facies analysis and morphology of the SSDS indicate that there are relationship between the depositional environments and SSDS. Endogenic processes are considered as the trigger agents and they are represented by rapid sedimentation and overloading, impact of breaking waves, pressure fluctuations caused by turbulent water flow, cyclic stress and current generated by storm waves and changes in water table. The present study did not identify exogenic processes as trigger agent. The occurrence of SSDS in southern Bida Basin strongly favoured a non-tectonic origin but a clear relationship high energy processes in tidal and fluvial depositional environments.展开更多
The study assessed petroleum systems in the southern Bida Basin,Nigeria,focusing on the Cretaceous sediments.Reservoirs comprise Lokoja and Patti Formation sandstones,while shales,claystone,and siltstone serve as sour...The study assessed petroleum systems in the southern Bida Basin,Nigeria,focusing on the Cretaceous sediments.Reservoirs comprise Lokoja and Patti Formation sandstones,while shales,claystone,and siltstone serve as source rocks and stratigraphic traps/seals.Detailed studies delineating the key elements of the petroleum systems in the basin have not been conducted due to a lack of subsurface data.The goal of the current study was to use field observations,Scanning Electron Microscopy(SEM),X-ray diffraction(XRD),and geochemical and geomechanical data to evaluate key components of petroleum systems in the southern Bida Basin.The results presented in this investigation are intended to attain specific objectives,especially those lacking in the basin's study sections.Petrophysical analysis revealed that the Lokoja Sandstone has porosity of 37%-39.5%and moderate permeability of 23.22-42.29 mD.The Patti Formation sandstone reservoirs exhibited high porosity(38%-42%)and moderate to good permeability(31.54-66.48 mD),suggesting good potential reservoirs.SEM results revealed intragranular pores and micro-fractures in the Patti Shale,whereas the sandstone reservoirs in the Lokoja and Patti formations displayed fractures,facilitating hydrocarbon migration.Quartz was the dominant mineral in the sandstone units of both formations.XRD analysis revealed that brittle and clay minerals influenced the microstructure of Patti Shale.Geochemical analysis indicated promising petroleum potential in the Patti Shale,with a total organic carbon(TOC)content of 1.87 wt%,free hydrocarbon from kerogen(S1)of 0.41 mg/g,hydrogen index(HI)of 0.75 mg HC/g TOC,and production index(PI)of 0.17.The Patti and Lokoja formations'shale,claystone,and siltstone exhibited sealing potential,with a plasticity index of 24-35 and coefficient permeability of 2.8×10^(-4)-3.6×10^(-4)cm/s.Field studies,XRD,geochemical data,and geomechanical index values have confirmed the key components of the petroleum system,which in turn facilitate hydrocarbon generation,migration,accumulation,and entrapment in the basin.展开更多
文摘A study of sedimentary facies,mineral and textural characteristics of sections of conglomerates/pebbles and sandstone facies found within the Lokoja and Patti Formations in southern Bida Basin,Nigeria,is carried out to evaluate the paleo-environment and reservoir quality of the sandstones of the formations through field observations and textural and mineralogical(using X-Ray Diffractogram)analyses.Nine lithofacies are identified and grouped into three main facies associations.These sedimentary facies suggest deposition in both foreshore and estuaries.The mineral analysis(XRD)shows that the quartz content in sandstone facies of the Lokoja Formation ranges between 49%and 67%,and that of the Patti Sandstone between 43%and 56%,indicating a quartz dominance.The granulometric studies reveal that the Lokoja Formation comprises coarse-to medium-grained(-0.63 to 1.30φ)sandstone with moderatepoor sorting of 0.72e1.824.On the other hand,medium to fine-grained sandstones dominate the Patti Formation,which is averagely poorly sorted(1.29-1.54φ).The sandstones are coarsely skewed to finely skewed,with the kurtosis ranging from very platykurtic to leptokurtic.Morphological results of the pebbles from both Lokoja and Patti Formations indicate that the study areas are mainly characterized by the interplay of both wave and fluvial processes,which suggests that the environment of deposition of sandstone facies is predominantly of the fluvial to the shallow marine environment with the indication of tidal influence.Integrating sedimentary facies and textural results suggests subtidal sand ridge/foreshore,estuarine mudflat,and estuarine delta environments with fluvial influences.Evidence from the textural and mineral characteristics indicate that the sandstone facies of the Lokoja and Patti Formations are fairly matured and can act as potential hydrocarbon reservoirs in the formations.The facies,XRD mineral,and textural results have revealed potential hydrocarbon reservoir areas and paleo-depositional features of the Lokoja and Patti Formations.
文摘An improvised auger sediment sampler was used to collect sediments at shallow depths from two wetlands in the Northern Bida Basin for laboratory studies in order to ascertain the impact on the chemical quality of groundwater within these two studied locations. The dissolved organic carbon content of water is an important component of the geochemical cycling of elements capable of affecting groundwater quality. The sediments which serve as a conduit and pathways for the elements’ transport depending on the characteristics of the particle sizes are to be considered in the evaluation of contaminant mobility within the pathways. Representative cored sediment samples were collected and their particle size characterization and chemical analysis for Organic Matter (OM), Organic Carbon (OC) and Moisture Content (MC) were carried out. The hydrometer results show that the sediment particle sizes are in the order of sand > clay > silt in both locations with few exceptions. This represents the geology of the area (sandstone). The Mean values of 1.14% and 1.98% of OC and OM respectively were recorded in the sediment samples collected in parts of Ebgako. In contrast, 1.72% and 2.97% mean values were recorded in sediments collected in part of Bida for OC and OM respectively. The values of the OC and OM in the sediments from the two wetlands are low and may have been dissolved along the groundwater pathways to the aquifer. Other physicochemical parameters analysed in the sediments showed poor correlation. OM and OC were strongly positively correlated and showed an R<sup>2</sup> value of 1 and 0.9 respectively for parts of the Bida and Egbako sheets. There is low acidity of the sediments from the two study locations with a mean pH value of 5.64 and 5.13 respectively for Egbako and Bida. The low acidic nature of the sediments and the OM and OC composition have the potential to influence biogeochemical processes in the sediments and can affect the chemical quality of the groundwater in these two study locations.
文摘Detailed fieldwork carried out in the southern part of Bida Basin, Nigeria, allowed the documentation of soft sediment deformation structures (SSDS) in the Maastrichtian Patti Formation. The aim of this study is to examine the sedimentary successions, describe and analyse these deformation features, discuss their deformation mechanisms and potential triggers. The Maastrichtian Patti Formation is composed of lithofacies interpreted to have been deposited in tidal and fluvial sedimentary environments. Soft sediment deformation structures recognised in the tidal sediments were clastic dykes, load cast, isolated sand balls, dish-and-pillar structures, convolute lamination, diapiric structures and recumbent folds. Severely deformed cross beds, ring structures, associated sand balls, normal folds and recumbent folds were identified in the fluvial sediments. SSDS recognised were interpreted to have been caused by effects of liquefaction and fluidization. Field observations, facies analysis and morphology of the SSDS indicate that there are relationship between the depositional environments and SSDS. Endogenic processes are considered as the trigger agents and they are represented by rapid sedimentation and overloading, impact of breaking waves, pressure fluctuations caused by turbulent water flow, cyclic stress and current generated by storm waves and changes in water table. The present study did not identify exogenic processes as trigger agent. The occurrence of SSDS in southern Bida Basin strongly favoured a non-tectonic origin but a clear relationship high energy processes in tidal and fluvial depositional environments.
文摘The study assessed petroleum systems in the southern Bida Basin,Nigeria,focusing on the Cretaceous sediments.Reservoirs comprise Lokoja and Patti Formation sandstones,while shales,claystone,and siltstone serve as source rocks and stratigraphic traps/seals.Detailed studies delineating the key elements of the petroleum systems in the basin have not been conducted due to a lack of subsurface data.The goal of the current study was to use field observations,Scanning Electron Microscopy(SEM),X-ray diffraction(XRD),and geochemical and geomechanical data to evaluate key components of petroleum systems in the southern Bida Basin.The results presented in this investigation are intended to attain specific objectives,especially those lacking in the basin's study sections.Petrophysical analysis revealed that the Lokoja Sandstone has porosity of 37%-39.5%and moderate permeability of 23.22-42.29 mD.The Patti Formation sandstone reservoirs exhibited high porosity(38%-42%)and moderate to good permeability(31.54-66.48 mD),suggesting good potential reservoirs.SEM results revealed intragranular pores and micro-fractures in the Patti Shale,whereas the sandstone reservoirs in the Lokoja and Patti formations displayed fractures,facilitating hydrocarbon migration.Quartz was the dominant mineral in the sandstone units of both formations.XRD analysis revealed that brittle and clay minerals influenced the microstructure of Patti Shale.Geochemical analysis indicated promising petroleum potential in the Patti Shale,with a total organic carbon(TOC)content of 1.87 wt%,free hydrocarbon from kerogen(S1)of 0.41 mg/g,hydrogen index(HI)of 0.75 mg HC/g TOC,and production index(PI)of 0.17.The Patti and Lokoja formations'shale,claystone,and siltstone exhibited sealing potential,with a plasticity index of 24-35 and coefficient permeability of 2.8×10^(-4)-3.6×10^(-4)cm/s.Field studies,XRD,geochemical data,and geomechanical index values have confirmed the key components of the petroleum system,which in turn facilitate hydrocarbon generation,migration,accumulation,and entrapment in the basin.
