Western Niger Delta Research Articles

Correction to: Building 3D Lithofacies and Depositional Models Using Sequential Indicator Simulation (SISIM) Method: A Case History in Western Niger Delta

Sequential indicator simulation algorithm is one of the popular stochastic simulation algorithms for reservoir geomodelling. It has been used to model delineated lithofacies and depofacies units within the OPO field, western Niger Delta. This simulation algorithm was chosen because of its ability to honour the well logs as local conditioning data using the global histogram, areal and vertical geological trends of the data, as well as the patterns of correlation. Three lithofacies were identified and modelled, namely sand, shaly sand and shale units. Vertical succession of the depositional facies within the field reveals five major facies which are basal shelf shale facies, heterolithic (sand–shale) facies, lower shoreface sand facies, upper shoreface sand facies and shoreface channel systems. The general environment of deposition is interpreted to be shoreline–shelf systems where the shoreface channel units, upper shoreface sand, lower shaly sand and heterolithic units constitute the parallic reservoir sequences, while the shale units within the shoreface and coastal environments act as potential source rocks and caprocks for hydrocarbon accumulation.

Evaluation of optimal reservoir prospectivity using acoustic-impedance model inversion: A case study of an offshore field, western Niger Delta, Nigeria

The evaluation of economic potential of any hydrocarbon field involves the understanding of the reservoir lithofacies and porosity variations. This in turns contributes immensely towards subsequent reservoir management and field development. In this study, integrated 3D seismic data and well log data were employed to assess the quality and prospectivity of the delineated reservoirs (H1–H5) within the OPO field, western Niger Delta using a model-based seismic inversion technique. The model inversion results revealed four distinct sedimentary packages based on the subsurface acoustic impedance properties and shale contents. Low acoustic impedance model values were associated with the delineated hydrocarbon bearing units, denoting their high porosity and good quality. Application of model-based inverted velocity, density and acoustic impedance properties on the generated time slices of reservoirs also revealed a regional fault and prospects within the field.

Hydrocarbon resource evaluation using combined petrophysical analysis and seismically derived reservoir characterization, offshore Niger Delta

Subsurface characterization and hydrocarbon resource evaluation were conducted using integrated well logs analysis and three-dimensional (3D) seismic-based reservoir characterization in an offshore field, western Niger Delta basin. Reservoir sands R1–R4 were delineated, mapped and quantitatively evaluated for petrophysical characteristics such as net-to-gross, volume of shale, water saturation, bulk water volume, porosity, permeability, fluid types and fluid contacts (GOC and OWC). The volume attributes aimed at extracting features associated with hydrocarbon presence detection, net pay evaluation and porosity estimation for optima reservoir characterization. Neural network (NN)-derived chimney properties prediction attribute was used to evaluate the integrity of the delineated structural traps. Common contour binning was employed for hydrocarbon prospect evaluation, while the seismic coloured inversion was also applied for net pay evaluation. The petrophysical properties estimations for the delineated reservoir sand units have the porosity range from 21.3 to 30.62%, hydrocarbon saturation 80.70–96.90 percentage. Estimated resistivity Rt, porosity and permeability values for the delineated reservoirs favour the presence of considerable amount of hydrocarbon (oil and gas) within the reservoirs. Amplitude anomalies were equally used to delineate bright spots and flat spots; good quality reservoirs in term of their porosity models, and fluid content and contacts (GOC and OWC) were identified in the area through common contour binning, seismic colour inversion and supervised NN classification.

Investigation of Seawater Intrusion into Coastal Groundwater Aquifers of Escravos, Western Niger Delta, Nigeria

In coastal regimes groundwater aquifers are often vulnerable to saltwater intrusion. Saltwater intrusion is often precipitated by natural hydrodynamic processes and overpumping of groundwater resource. Saltwater intrusion is presumed to have significant effect on quality of groundwater and accountable for lack of access to freshwater in the areas under study. The objective of this study is to use resistivity data obtained from vertical electrical sounding to ascertain the salinity of shallow aquifers, determine depth and thickness of freshwater aquifers. The Schlumberger array configuration was employed in acquisition of data. The maximum and minimum spacing between electrodes (AB/2) ranged from 2m to 250m. Resistivity values ranged from 0.24Ωm to 427Ωm, Values which ranged from 0.2Ωm to 4Ωm was construed to be aquifer saturated with saltwater, brackish water was inferred from resistivity values which vary between 7Ωm and 11Ωm, and clay was assigned to resistivity values that ranged from 17Ωm to 29Ωm. Effect of tide contributes to salinity of shallow aquifer around the seashore area. Aquifers saturated with saltwater are found at the depths of 10.5m, brackish water at 4m to 9m, while freshwater can be located from the depth of 19-46m. The study is able to reveal that groundwater quality has been compromised by intrusion of saltwater. We conclude that there is potential of saltwater intrusion into the freshwater lenses, which may be enhanced in the future by over- development of groundwater. Key words: Escravos, Vertical electrical sounding, Saltwater Intrusion, freshwater lenses, Aquifer, groundwater

Saltwater Intrusion Appraisal of Shallow Aquifer in Burutu Area of the Western Niger Delta with 2D Electrical Resistivity Tomography

The area is faced with endemic groundwater quality problems arising from abandoned shallow and deep boreholes. The abandonment of shallow boreholes is presumed to have been caused by saltwater intrusion from the ocean. The objective of this paper is to examine if saltwater is responsible for groundwater degradation associated with shallow groundwater aquifer. To achieve this, a multi-electrodes ABEM SAS 4000 Terrameter was used in the acquisition of 2D electrical resistivity tomography data. Inverse models which estimate actual subsurface geologic resistivity was generated from RES2DINV software and subsequently geologic information were construed from them. The interpretation of the various profiles returned resistivity values which contrasted the existence of saltwater in the pore spaces of groundwater aquifer media in the area under investigation. Resistivity images of values ranged from 2.34Ωm to 70 Ωm where interpreted as clays, greater than 70-90Ωm as fine sand and 90Ωm and above where interpret as medium sand. The evidence revealed by the 2D electrical resistivity tomography investigation combined with geochemistry of groundwater from literature suggested that abandonment of shallow boreholes are probably not related to saltwater intrusion. The study has established that poor groundwater quality being experienced is not caused by saltwater intrusion rather by iron which cannot be separately distinguished from groundwater by resistivity technique. Key Word: 2D electrical resistivity tomography, Burutu, Saltwater intrusion, shallow aquifer, western Niger Delta, groundwater quality

X-ray Fluorescence (XRF) Geochemical Investigation of Delta Steel Company (DSC), Ovwian–Aladja, western Niger Delta, Nigeria, Steelmaking Slag for use as Iron making Blastfurnace Feed and Fertilizer

This work investigated the bulk geochemistry of fifteen (15) samples of Delta Steel Company (DSC) dump slag produced by the direct reduction steelmaking process, using the X–ray fluorescence spectroscopy (XRF) method and glass discs prepared from each of the fifteen test slag samples. The results indicate the presence of major amounts of CaO(36.62%), MgO(9.77%), Fe2O3(27.32%), SiO2(19.86%), Al2O3(5.43%), low amounts of MnO(1.46%), TiO2(0.42%), Cr2O3(0.17%), P2O5 (0.53), and minor amounts of SO3(0.04). The geochemical composition of the slag indicates suitable use as iron making blastfurnace feed and as fertilizer. The low amount of MnO in the slag is advantageous as it can reduce the disadvantage of probably causing refractory lining destruction in the presence of a notable amount of K20. The use of this slag would contribute to the conservation of natural steelmaking resources, improved crop yeild and reduction in CO2 emission in the company environment.Â

Seafloor and buried mounds on the western slope of the Niger Delta

Seafloor mounds are potential geohazards to offshore rig emplacement and drilling operations and may contain evidence of underlying petroleum systems. Therefore, identifying and mapping them is crucial in de-risking exploration and production activities in offshore domains.A 738 km2 high resolution three-dimensional seismic dataset was used to investigate the occurrence, seismic characteristics and distribution of features interpreted as seafloor and buried sediment mounds, at water-depths of 800–1600 m, on the western Niger Delta slope. Fifteen seafloor mounds and eighteen shallowly buried mounds were identified. The seafloor mounds are characterised by lower seismic amplitude anomalies than the surrounding seabed sediments, and overlie vertical zones of acoustic blanking. The buried mounds in contrast are characterised by high amplitude anomalies; they also directly overlie sub-vertical zones of acoustic blanking. Seismic evidences from the features, their distribution patterns and tectono-stratigraphic associations suggest that their formation was controlled by the juxtaposition of buried channels and structural highs and their formation caused by focused fluid flow and expulsion of entrained sediments at the seabed.Considering the acoustic and geometrical characteristics of the mounds and comparing them with mound-shaped features from around the world, we conclude that the mounds most likely comprise heterolithic seafloor extrusions of muds and sands from the Agbada Formation with gas and possibly oil in some of the pore space giving rise to the acoustic characteristics.

Some Theories and Concepts of Intergroup and Conflict Relations in the Western Niger Delta of Nigeria

Intergroup conflicts occupy a special place in the interaction of social groups and of necessity form the basic building blocks for the integration of previously fragmented groups. The Western Niger delta obviously has since been a theatre of socio-political conflicts. Viewed from the contemporary clime, there is a lacuna in the formulation of theories and concepts in understanding and explaining the nature and pattern of intergroup relations in the region from the pre-colonial period. This work therefore attempts an exploratory analysis of some theories and concepts of intergroup relations in the Western Niger Delta of Nigeria using the historical approach with the use of secondary source materials. The paper concludes that the relation among the diverse ethnic groups in Nigeria, especially the Western Niger Delta, may not have been as intense, or as hostile as it has become since the attainment of independence in 1960. This paper no doubt is essential for the understanding and tackling of the problem of intergroup relations and conflict in the region in particular and Nigeria at large.

Facies architecture of submarine channel deposits on the western Niger Delta slope: Implications for grain‐size and density stratification in turbidity currents

AbstractHigh‐resolution bathymetry, seismic reflection, and piston core data from a submarine channel on the western Niger Delta slope demonstrate that thick, coarse‐grained, amalgamated sands in the channel thalweg/axis transition to thin, fine‐grained, bedded sands and muds in the channel margin. Radiocarbon ages indicate that axis and margin deposits are coeval. Core data show that bed thickness, grain size, and deposition rate strongly decrease with increasing height above channel thalweg and/or distance from channel centerline. A 5 times decrease in bed thickness and 1–2 ψ decrease in grain size are evident over a 20 m elevation change (approximately the elevation difference between axis and margin). A simplified in‐channel sedimentation model that solves vertical concentration and velocity profiles of turbidity currents accurately reproduces the vertical trends in grain size and bed thickness shown in the core data set. The close match between data and model suggests that the vertical distribution of grain size and bed thickness shown in this study is widely applicable and can be used to predict grain size and facies variation in data‐poor areas (e.g., subsurface cores). This study emphasizes that facies models for submarine channel deposits should recognize that grain‐size and thickness trends within contemporaneous axis‐margin packages require a change in elevation above the thalweg. The transition from thick‐bedded, amalgamated, coarser‐grained sands to thin‐bedded, nonamalgamated, finer‐grained successions is primarily a reflection of a change in elevation. Even a relatively small elevation change (e.g., 1 m) is enough to result in a significant change in grain size, bed thickness, and facies.

Taxonomic Notes on Some Species of Genus Globigerinoides from Kafe Field, Offshore Western Niger Delta, Nigeria

Taxonomic Notes on Some Species of Genus Globigerinoides from Kafe Field, Offshore Western Niger Delta, Nigeria

Mineral Phase Crystallization Sequence of Delta Steel Company (DSC), Ovwian-Aladja, Western Niger Delta Steelmaking Slag for Use as Material in Industry

Slag is a non-metallic by-product obtained in the refining of metals from metallic ores. Slag production at the Delta Steel Company (DSC), Ovwian-Aladja, western Niger Delta, follows the direct iron reduction steelmaking process. Fifteen company slag samples collected were examined by x-ray fluorescence, thin section petrography and electron microprobe analyses to establish the mineralogy and mineral crystallization sequence and thus explain their occurrences. The results show the presence of synthesized silicate minerals of belite, melilite and merwinite; calcium aluminate, wustite, periclase, perovskite and glass in the slag formed at between the temperatures of 1500°C and 500°C. Crystallization sequence is alpha (α) form of belite (1500°C-1420°C), alpha high (α/H) belite (1420°C-1160°C), alpha low (α/L) belite (1160°C-680°C, beta (β-) belite (680°C – 630°C), Melilite (1420°C-680°C), aluminate, merwinite, wustite, periclase, peruvskite and glass (630°C–500°C) in that order. This study has revealed that in behavior, synthetic minerals also crystallize from high to low temperature forms as is the case with natural minerals formed from silicate magmas. The forming behaviour of these minerals confers on them the important characteristics for industrial use as an industrial mineral compliment to natural materials.

Interaction between gravity-driven listric normal fault linkage and their hanging-wall rollover development: a case study from the western Niger Delta, Nigeria

Abstract Rollover is the folding of the hanging-wall sedimentary record in response to slip on listric normal faults, and is a common feature of sediment-rich, gravity-driven tectonic provinces. Rollovers have been extensively studied by means of geometrical reconstruction, and numerical and analogue modelling. However, the detailed interaction between the kinematics of bounding listric normal faults and their hanging-wall deformation is not yet fully understood. In this study, we use 3D seismic-reflection data from the Forcados-Yokri area, western Niger Delta, Nigeria, to study the lateral linkage and landwards backstepping history of an array of listric normal faults, particularly focusing on their influence on the development and evolution of hanging-wall rollovers. Five individual, partly overlapping rollover structures have been studied with respect to their relative initiation and decay time, their spatial distribution, and their relationship to the tectonic history of their respective bounding faults. We demonstrate that the studied rollovers are highly dependent on the development of their bounding faults in terms of initiation time, lateral linkage, internal structural development and decay. Fault–rollover interaction is dynamic and changes through time depending on the temporal evolution of listric faults. Four genetic types of fault–rollover interaction were identified in this study: (1) the rotation of a rollover–crestal-collapse system, controlled by a changing lateral bounding-fault orientation during fault growth; (2) a stepwise shift of rollover–crestal-collapse systems associated with rollover abandonment, controlled by the initiation of a new fault in the footwall of an older structure; (3) a gradual shift of successive rollovers controlled by branching main faults; and (4) a general landwards and upwards migration of crestal-collapse faults within a rollover above stationary listric main faults.

High-resolution, millennial-scale patterns of bed compensation on a sand-rich intraslope submarine fan, western Niger Delta slope

Near-seafloor core and seismic-reflection data from the western Niger Delta continental slope document the facies, architecture, and evolution of submarine channel and intraslope submarine fan deposits. The submarine channel enters an 8 km long x 8 km wide intraslope basin, where more than 100 m of deposits form an intraslope submarine fan. Lobe deposits in the intraslope submarine fan show no significant downslope trend in sand presence or grain size, indicating that flows were bypassing sediment through the basin. This unique dataset indicates that intraslope lobe deposits may have more sand-rich facies near lobe edges than predicted by traditional lobe facies models, and that thickness patterns in intraslope submarine fans do not necessarily correlate with sand presence and/or quality. Core and radiocarbon age data indicate that sand beds progressively stack southward during the late Pleistocene, resulting in the compensation of at least two lobe elements. The youngest lobe element is well characterized by core data and is sand-rich, ~ 2 km wide x 6 km long, > 1 m thick, and was deposited rapidly over ca. 4,000 yr, from 18-14 ka. Sand beds forming an earlier lobe element were deposited on the northern part of the fan from ca. 25 to 18 ka. Seafloor geomorphology and amplitudes from seismic reflection data confirm the location and age of these two compensating lobe elements. A third compensation event would have shifted sand deposition back to the northern part of the fan, but sediment supply was interrupted by rapid sea level rise during Meltwater Pulse 1-A at ca. 14 ka, resulting in abandonment of the depositional system.

Paleoclimatic significance of microflora retrieved from Well ‘Y’, Western Niger Delta, Nigeria

Palynomorph species comprising 53 pollen, 7 spores, 2 algae and 6 dinoflagellate cysts were recovered from a section of well ‘Y’ located in the offshore western Niger Delta and were used for paleoclimatic deductions of the sediments. There was a dominance of the fresh water swamp species over the brackish, savannah and the rain forest types. Stratigraphically, four floral zones corresponding to inferred climatic units were identified. M2 floral zone, at the lower portion of the well, occurred between 8150 ft (2486 m) and 6440 ft (2147 m). It corresponded to wet and humid climate with periodic rainfall. M1 floral zone was between 6440 ft (1964 m) and4820 ft (1470 m) indicating a dry climatic phase in a high sea level stand. The P7 floral zone was also a humid climate in a sea level rising environment while the topmost floral zone between 4370 ft (1333 m) and3125 ft (953 m) was a fluctuating dry and wet climatic phase in a tidally influenced environment. A humid tropical climate characterised by alternation of dry and wet regimes occasioned by sea level changes and cyclic fluctuation in continental climatic condition is inferred from the analysed well that spanned through Late Miocene and Early Pliocene.Keywords: Floral zones; Niger Delta; Paleoclimate; Palynomorphs; spores; pollen

Ijo-Itsekiri Relations before the Colonial Period in Nigeria

The Ijo and Itsekiri are two of the closest neighbours in the Warri area of the Western Niger Delta region of Nigeria. They have intermarried and had lived together for centuries. But towards the close of the last century, the two groups clashed, ostensibly over the relocation of the headquarters of the then newly created Warri South (later Warri South-West) Local Goverment Area in the present Delta State from Ogbe-Ijoh (an Ijo town) to Ogidigben (an Itsekiri town) by the late General Sani Abacha – led Federal Military Government of the time. During the crisis which claimed many lives and property, and destroyed many private and public businesses, the two groups fought each other with all kinds of dangerous and sophisticated weapons. This situation had made many well-meaning people to ask whether there were longstanding grievances between the two groups. The available records reveal that there were, indeed, deep-rooted grievances between the two groups. These problems however started from the colonial period in Nigeria. Before then, the two groups had lived peacefully together. This is the picture this article attempts to document.

European Influence in Ijo-Itsekiri Relations in Nigeria

There is currently an uneasy calm in the Ijo-Itsekiri area of the Western Niger Delta. The two groups have intermarried, and had lived together for centuries. But towards the end of the last century, the two groups clashed, ostensibly over the relocation of the headquarters of the then newly created Warri South (later Warri South-West) Local Government Area from Ogbe-Ijoh (an Ijo town) to Ogidigben (an Itsekiri town). During the crisis, the two groups had employed all types of dangerous and sophisticated weapons against each other. This development had made many well-meaning persons to wonder if there were longstanding grievances between them. This article underscores the fact that there was, indeed, deep-noted bitterness between the two groups, dating back to the period of European contact with Nigeria from the 15th Century. the hostilities started with the introduction of new forms of trade, religion, education, government etc. because of space, this article concentrates on three major areas, namely, trade, education, and land acquisition and ownership. The article is produced mainly from written sources.

Hydrocarbon field evaluation: case study of ‘Tadelu’ field shallow offshore Western Niger Delta, Nigeria

Field evaluation in a complex sedimentary environment is always tedious due to problems associated with imaging of the subsurface in such areas. The ‘Tadelu’ field in Western Niger Delta, Nigeria, consists of a series of vertically stacked reservoirs in the Agbada Formation, thus making the field a complex sedimentary environment. The main objective of this study is to perform geophysical and petrophysical interpretations of properties that are typical of a shallow marine, transitional environment, with its attendant pattern of subsurface complexities, using 3D seismic and well log data. The approach adopted in achieving this objective included 3D seismic data interpretation, petrophysical rock typing, fluid typing and contact identification and determination of reservoir properties, onwards to reserve estimation for all the hydrocarbon-bearing reservoirs in the field. Five horizons as well as major and minor faults were mapped in the field, and five structural depth maps of reservoirs A, B, B1, C and C1 were generated within the objective depth interval to define the geometry of the reservoirs. Well log data from four wells in the field were studied to characterize the porosity, shale volume and water saturation of the reservoirs. The gamma ray (GR) logs were normalized and used in the computation of shale volume, while available density logs were used in the computation of porosities. Water saturation was determined using the Waxman–Smits model to take into consideration the shaly nature of the reservoir sands. The combination of porosity, shale volume and water saturation cut-off values was used in calculating net pay and net pay averages. The result of the structural interpretation shows that Tadelu field is characterized by two major faults and synthetic faults. The synthetic faults are dipping in northeast–southwest direction, and the closure formed by their hanging walls constitutes the target area for hydrocarbon in the field. However, within the reservoirs of Tadelu field, the net sand range is from 0.17 to 0.99 ft, having an average porosity in the range of 22 to 27 %. Water saturation average ranged from a minimum of 19 to a maximum of 27 %. Porosity in the field is high on the average due to very good to excellent sand quality. These petrophysical deliverables served as an input in the estimation of reserves. The gross rock volume (GRV) was determined by establishing a cut-off at appropriate contact(s). Reserve estimation was performed for the hydrocarbon-bearing sands and a total proven recoverable oil and gas estimate put at 42.797 MMbbl and 13.256 Bscf, respectively.

Evaluation of Hydrocarbon Prospect of Fareed Field, Western Niger-Delta, Nigeria

Evaluation of Hydrocarbon Prospect of Fareed Field, Western Niger-Delta, Nigeria

Environmental Impact Assessment of Selected Oil Production Facilities in Parts of Niger Delta, Nigeria

The impact of oil production activities on the chemistry of soil and groundwater was investigated around seven production facilities, ranging from flow stations to wellhead in the western Niger Delta area. The method involved systematic sampling of soil and groundwater within a one kilometre radius of such facilities. The samples obtained were analysed for pH, TOC, TPH, V, Ni and Fe by standard procedures. The results indicate a general conformity of groundwater physico-chemistry to international standards for chemical potability. However, the investigated soil samples reveal in some cases elevated values of TPH (mean: 26.07 mg/kg) and Ni (mean: 8.89 mg/kg) which suggest a negative impact on the soil in the vicinity of such oil production facilities. Although ground-water may show no apparent contamination, pollutants trapped in the soil are in potential transit to groundwater, and may eventually be dissolved and transported through the soil profile to the water table by recharging rainwater. The environmental and health conditions of host communities are thereby endangered.

The Petrol-dollar Economy and the Value Shift among the Youths of the Western Niger Delta Region of Nigeria

The pre-petroleum Niger Delta region was well endowed with enormous natural and cultural resources. However, the advent of the oil industry seems to have affected some changes in the social–cultural structures of this region. Therefore, to determine the impact of the petroleum industry on livelihoods and value orientation, in-depth interview sessions were held with 20 respondents in four communities in the Delta State Nigeria to complement the secondary information collected through documentary method. Consequently, the article argues that the petroleum-led agrarian crisis has created a monetised culture among its youths. This condition has impacted negatively on traditional values, resulting in the socio-cultural quaking of communities in the region. The article therefore suggests a holistic approach that would provide education, cultural reorientation and economic empowerment for the youths.