Some problems of groundwater development in the Niger Delta ranging from negligence to geological peculiarities are examined to highlight the importance and application of geologic knowledge and research for decision ...Some problems of groundwater development in the Niger Delta ranging from negligence to geological peculiarities are examined to highlight the importance and application of geologic knowledge and research for decision making and averting failure in groundwater development for provisional use. Although the geology and hydrogeologic properties of the aquifer system in the Niger Delta immensely favors groundwater development, there are several recorded cases of failed groundwater development projects poor water quality, dry boreholes and boreholes with surprisingly low yield which could have been avoided. This is due to the perception that since groundwater is prolific, geologic and locational peculiarities can be ignored. This research has highlighted the importance of the knowledge of the hydrogeology of the different geologic units as significant factor in the success of groundwater projects through the correlation of past research of geologic units and groundwater potentials, quality and challenges with the present projects implemented in some of the locations. Cases where groundwater projects are executed with wrong exploration options and without consideration of the peculiarity of the geologic units of the project area, including engagement of incompetent contractors, and negligence to the existing regulatory framework for groundwater development in Nigeria are presented. In order to promote sustainable groundwater development and management in the Niger Delta, this research highlights and recommends the pragmatic use of geologic information including various technical, institutional, regulatory and management measures which have the capacity to avert challenges in groundwater development for provisional use.展开更多
3D seismic and petrophysical log data interpretation of reservoir sands in “SIMA” Field, onshore Niger Delta has been undertaken in this study to ascertain the reservoir characteristics in terms of favourable struct...3D seismic and petrophysical log data interpretation of reservoir sands in “SIMA” Field, onshore Niger Delta has been undertaken in this study to ascertain the reservoir characteristics in terms of favourable structural and petrophysical parameters suitable for hydrocarbon accumulation and entrapment in the field. Horizon and fault interpretation were carried out for subsurface structural delineation. In all, seven faults (five normal and two listric faults) were mapped in the seismic section. These faults were major structure building faults corresponding to the growth and antithetic faults in the area within the well control. The antithetic fault trending northwest-southeast and the normal fault trending northeast-southwest on the structural high in the section act as good trapping mechanisms for hydrocarbon accumulations in the reservoir. From the manual and auto-tracking methods applied, several horizons were identified and mapped. The section is characterized by high amplitude with moderate-to-good continuity reflections appearing parallel to sub-parallel, mostly disturbed by some truncations which are more fault related than lithologic heterogeneity. The southwestern part is, however, characterized by low-to-high or variable amplitude reflections with poor-to-low continuity. Normal faults linked to roll-over anticlines were identified. Some fault truncations were observed due to lithologic heterogeneity. The combination of these faults acts as good traps for hydrocarbon accumulations in the reservoir. Reservoir favourable petrophysical qualities, having average NTG, porosity, permeability and water saturation of 5 m, 0.20423, 1128.219 kD and 0.458 respectively.展开更多
This paper evaluates the hydrocarbon prospectivity and play risks of “Bob” field in Niger Delta Basin, Nigeria. The aim is to enhance exploration success through improved approach/technique by incorporating risk ana...This paper evaluates the hydrocarbon prospectivity and play risks of “Bob” field in Niger Delta Basin, Nigeria. The aim is to enhance exploration success through improved approach/technique by incorporating risk analysis that previous studies have not fully considered. This approach combines a set of analyses including stratigraphic/structural, amplitude, petrophysical parameter, volumetric and play risk using a suite of well logs and 3D seismic data. Maximum amplitude anomaly map extracted on the surfaces of delineated 3 reservoirs revealed 6 prospects, namely: Dippers, Cranes, Turacos, Nicators, Jacanas and Pelicans with hydrocarbon accumulation. Petrophysical analysis showed ranges of values for porosity, permeability and water saturation of 0.21 to 0.23, 158.96 to 882.39 mD, and 0.07 to 0.11, respectively. The various prospects yielded the following stock tank volumes 12.73, 6.84, 3.84, 11.32, 7.42 and 4.76 Million barrels (Mbls) each respectively in a column of 66 ft reservoir sand in the study area. Play risk analysis results gave: Pelicans and Nicators (low), Turacos and Dippers (moderate), while Jacanas and Cranes show high risk with minimal promise for good oil accumulation. The prospects possess good reservoir petrophysical properties with low to moderate risk, thus, viable for commercial hydrocarbon production, which increases confidence in management decisions for production.展开更多
Integrated modelling, well correlation and petrophysical analysis were performed to characterize the reservoirs for optimum hydrocarbon correlation using 3-D seismic reflection data and suites of well logs from Ataga ...Integrated modelling, well correlation and petrophysical analysis were performed to characterize the reservoirs for optimum hydrocarbon correlation using 3-D seismic reflection data and suites of well logs from Ataga 5, 7, 10 and 11 wells respectively in Ataga field, shallow offshore, Niger Delta Basin, Nigeria. The study revealed the presence of two viable hydrocarbon bearing reservoirs, AT1 and AT2 and the average values of porosity, permeability, water saturation, hydrocarbon saturation, Net to Gross (NTG) and volume of shale are in the ranges of 15% - 77%, 44.5% - 75.5%, 25.5% - 85%, 15% - 75.5%, 0.70 - 0.88 and 0.11 - 0.38 respectively which goes further to show that the both reservoirs have fair characteristics that are suggestive of the presence of hydrocarbon accumulation. It can therefore be deduced that the permeability values are reflective of fair interconnectivity of pore spaces of sands within the well areas and their ability to transmit fluids, the depth and depth structural map generated for the horizons and structures shows that the most dominant trapping mechanism in the area under study is the crescentic growth fault and the rollover anticlines trending in the Northwest-Southeast direction and from the volumetric analysis. It can be deduced that the recoverable gas for AT1 and AT2 reservoirs is 2 × 10<sup>6</sup> mscf and 6 × 10<sup>6</sup> mscf respectively.展开更多
Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for deve...Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for development purposes and to meet construction needs in the region. There is currently no regulation as to where sand can be mined in river channels because of the lack of adequate understanding of the risks to coastal infrastructure involved with its abstraction. The phenomenon of bridge Abutment and bank failure induced by excessive dredging of sand river bed is considered. Two types of instability were distinguished, one relating to the equilibrium slope of the riverbed and the other riverbank instability. An empirical relationship in the form X<sub>s</sub> = 3Htan(90 - α) has been developed through analysis, supported by examples that a minimum distance of 94 m (for sand river beds) from a bridge should be observed for sand abstraction in order to guaranty the safety of bridge foundation. For clay riverbeds, slightly shorter minimum distances can be considered safe. The study further shows that the capacity of sand borrowing in river channels to generate bank instability is dependent on the composition and stratigraphy beneath the river bed.展开更多
Despite exploration and production success in Niger Delta,several failed wells have been encountered due to overpressures.Hence,it is very essential to understand the spatial distribution of pore pressure and the gene...Despite exploration and production success in Niger Delta,several failed wells have been encountered due to overpressures.Hence,it is very essential to understand the spatial distribution of pore pressure and the generating mechanisms in order to mitigate the pitfalls that might arise during drilling.This research provides estimates of pore pressure along three offshore wells using the Eaton's transit time method,multi-layer perceptron artificial neural network(MLP-ANN)and random forest regression(RFR)algorithms.Our results show that there are three pressure magnitude regimes:normal pressure zone(hydrostatic pressure),transition pressure zone(slightly above hydrostatic pressure),and over pressured zone(significantly above hydrostatic pressure).The top of the geopressured zone(2873 mbRT or 9425.853 ft)averagely marks the onset of overpressurization with the excess pore pressure above hydrostatic pressure(P∗)varying averagely along the three wells between 1.06−24.75 MPa.The results from the three methods are self-consistent with strong correlation between the Eaton's method and the two machine learning models.The models have high accuracy of about>97%,low mean absolute percentage error(MAPE<3%)and coefficient of determination(R2>0.98).Our results have also shown that the principal generating mechanisms responsible for high pore pressure in the offshore Niger Delta are disequilibrium compaction,unloading(fluid expansion)and shale diagenesis.展开更多
The influence of origin, depositional environment and thermal maturity of organic matter on the occurrence of aromatic hydrocarbons in source rocks from the central and northwestern Niger Delta was investigated. Eight...The influence of origin, depositional environment and thermal maturity of organic matter on the occurrence of aromatic hydrocarbons in source rocks from the central and northwestern Niger Delta was investigated. Eighty two source rock samples from four oil wells in the central and northwestern Niger Delta were analyzed for the aromatic hydrocarbon content using gas chromatography-mass spectrometry (GC-MS). The results of analysis of aromatic hydrocarbon fractions of the source rock extracts show the presence of many classes of aromatic hydrocarbons, which include naphthalenes, phenanthrenes, biphenyls, dibenzothiophenes and fluorenes. Trimethylnaphthalene (TMN) is the most abundant among the naphthalenes while dimethylphenanthrene (DMP) is the most abundant among the phenanthrenes. Among the biphenyls, 3-methylbiphenyl (3 MB) is the most abundant while 4-methyldibenzothiophene (4MDBT) is the most abundant among the dibenzothiphenes. Only two fluorenes were detected, and fluorene is more in abundance than 1-methylfluorene (1 MF). Depositional environment indicators of aromatic hydrocarbon organic matter reveal that the organic materials in the source rocks in these wells were deposited in marine-to-swamp depositional environments under reducing to suboxic conditions. Thermal maturity indicators calculated from the abundance of the aromatic hydrocarbons indicate that the source rock samples are thermally mature. Most of the source rocks are at the peak of oil window while a few at the early oil window. Source rocks from wells GB, OP and OT in the central Niger Delta are thermally more mature than those from well AW in the northwestern Niger Delta.展开更多
This paper studied an architecture model of turbidite channel systems based on the shallow- layer high resolution 3D seismic information in the deepwater area in the Niger Delta continental slope, West Africa as a pro...This paper studied an architecture model of turbidite channel systems based on the shallow- layer high resolution 3D seismic information in the deepwater area in the Niger Delta continental slope, West Africa as a prototype model. Different types of channel systems were identified and the corresponding architecture models were established. The controlling factors, evaluation criteria and spatial distribution of different channel systems were analyzed. This study shows that turbidite channel systems of West Africa could be classified into three types; confined, semi-confined and unconfined, according to the condition of canyon and the levees on both sides. Oil one hand, along the transport direction, channel system evolves from confined to unconfined. Within channel systems, channel complexes, including two types of incised and enveloped, are the most important reservoir bodies. On the other hand, there is a channel complex evolution from incised to enveloped vertically. The geological factors exert impacts of different levels on the architecture of the turbidite channels in different sedimentary systems or even within the same system.展开更多
Deep-water turbidite channels have attracted much attention as a focused issue in petroleum exploration and development. Extensive studies have been performed on the architecture of turbidite channels, and most resear...Deep-water turbidite channels have attracted much attention as a focused issue in petroleum exploration and development. Extensive studies have been performed on the architecture of turbidite channels, and most researches have focused on their geometric shapes, sedimentary processes and controlling factors. However, little attention has been paid to the distribution patterns, distribution laws and quantitative studies of composite sand bodies of turbidite channels. Taken one slope area of the Niger Delta Basin as an example, this study conducted a semi-quantitative to quantitative analysis on architecture of composite sand bodies of turbidite channels based on cores, well logging and seismic surveys. It is shown that turbidite channel systems can be classified as confined and unconfined channel systems. For confined channel systems, the vertical evolution process involves four stages. The sinuosity of a channel system is controlled by slope, with a negative power function relationship between them. When slope gradient reaches four degrees, the channel system is nearly straight. Based on the migration direction and migration amount of single channels within channel complexes, channel composite patterns can be divided into four classes(the lateral composite, en-echelon composite, swing composite and vertical composite) and several subclasses. Various channel composite patterns show specific distribution laws spatially. For meandering channel complexes at the middle-late evolution stage of confined channel systems, the lateral migration amongst single channels shows the features of integrity and succession. The sinuosity of single channels in the late period is greater than that in the early period, and cut-offs may occur locally when the sinuosity is larger than five degrees. This study provides a better understanding for the geological theory of deep-water sedimentary, and also improves exploitation benefits of this type of reservoirs.展开更多
Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the...Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the geochemical significance of tricyclic and tetracyclic terpanes in source rock extracts from the Offshore Niger Delta Bain,Nigeria with gas chromatography-mass spectrometry(GC-MS).The total relative abundances of tricyclic terpanes,C_(19)TT-C_(21)TT,and C_(23) TT in the rock samples ranged from 82.50 to 96.37%,50.08 to 74.17%,and 25.83 to 49.92%,respectively.These values showed the source rocks were formed from a mixed origin(terrestrial and marine).Among the tricyclic and tetracyclic terpanes identified in the rock extracts,the conventional(C_(20)TT,C_(23)TT,C_(24)TT,C_(24)TeT)and recent(Y1,X1,Z1)were more prominent than all others,indicating mixed input of terrigenous and marine organic matter.The C_(24)TT/C_(23)TT,C_(24)TeT/(C_(24)TeT+C_(26)TT),C_(19)TT/C_(23)TT,C_(20)TT/C_(23)TT,C_(25)TT/C_(24)TeT,C_(25)TT/C_(26)TT,C_(19)TT/C_(20)TT,C_(24)TeT/C_(26)TT,Z1/(Z1+C_(24)TT),and Y1/(Y1+C_(24)TT)in the rock samples range from 0.33 to 1.30,0.76 to 0.90,0.18 to 0.73,0.34 to 1.05,0.33 to 1.74,0.30 to 1.39,0.31 to0.89,1.66 to 4.33,0.36 to 0.83,and 0.34 to 0.79,respectively.These values further showed that the rock samples were formed from mixed input of terrigenous and marine organic matter and deposited under oxic to suboxic conditions in lacustrine-fluvial/deltaic environments.Also,the C_(24)TeT/C_(20)-26TT,C_(24)TeT/C_(30)HOP,and C_(23)TT/C_(30)HOP ranged from 0.16 to 0.45,0.02 to 0.42,and 0.01 to 0.48,respectively.This range of values suggests that source rocks were within immature to early mature stage.Thus,this study showed that tricyclic and tetracyclic terpanes were effective in determining the origin,depositional environments,and thermal maturity of source rocks in the Niger Delta Basin,Nigeria.展开更多
Thirty-nine crude oils and twenty-one rock samples from Niger Delta Basin,Nigeria have been characterized based on their isotope compositions by elemental analysis-isotope ratio mass spectrometry and gas chromatograph...Thirty-nine crude oils and twenty-one rock samples from Niger Delta Basin,Nigeria have been characterized based on their isotope compositions by elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry.The bulk carbon isotopic values of the whole rock extracts,saturate and aromatic fractions range from–28.7‰to–26.8‰,–29.2‰to–27.2‰and–28.5‰to–26.7‰,respectively while the bulk carbon isotopic values of the whole oils,saturate and aromatic fractions range from–25.4‰to–27.8‰,–25.9‰to–28.4‰and–23.5‰to–26.9‰,respectively.The average carbon isotopic compositions of individual alkanes(nC12-nC33)in the rock samples range from–34.9‰to–28.2‰whereas the average isotopic values of individual n-alkanes in the oils range from–31.1‰to–23.8‰.Theδ13C isotope ratios of pristane and phytane in the rock samples range from–29.2‰to–28.2‰and–30.2‰to–27.4‰respectively while the pristane and phytane isotopic values range from–32.1‰to–21.9‰and–30.5‰to–26.9‰,respectively.The isotopic values recorded for the samples indicated that the crude oils were formed from the mixed input of terrigenous and marine organic matter and deposited under oxic to sub-oxic condition in lacustrine-fluvial/deltaic environments.The stable carbon isotopic compositions were found to be effective in assessing the origin and depositional environments of crude oils in the Niger Delta Basin.展开更多
Objective The term "pockmark" was introduced by King and MacLean (1970) to describe small "circular" on echosounder records in Nova Scotia. described as circular, near Pockmarks are usually circular or elongated...Objective The term "pockmark" was introduced by King and MacLean (1970) to describe small "circular" on echosounder records in Nova Scotia. described as circular, near Pockmarks are usually circular or elongated depressions, generally 10--400 m in diameter and 30-50 m in deep. Pockmarks are normally regarded to be manifestations of fluids escape through the seabed. Pockmarks are valuable features on the seafloor and are useful in constraining the hydrodynamics of sedimentary basins. Since then pockmarks have been recognized in many areas around the world. They occur predominantly in fine-grained siliciclastic depositional settings, although a few case studies have been reported in carbonate settings. In this paper we illustrate a suite of fluid escape features, discovered during the course of petroleum exploration on the West Africa continental margin (Fig. 1). They are particularly of interest to the oil and gas industry because they could be potential indicators of deeply buried hydrocarbon reservoirs, and fluid flow phenomena in the deep water oilfield are important for the safe and efficient exploration, development and production of hydrocarbons in the area.展开更多
The distribution and geochemical significance of dibenzofurans,phenyldibenzofurans and benzo[b]naptho-furans in source rocks from Niger Delta basin,Nigeria,were investigated by Rock-Eval pyrolysis and gas chro-matogra...The distribution and geochemical significance of dibenzofurans,phenyldibenzofurans and benzo[b]naptho-furans in source rocks from Niger Delta basin,Nigeria,were investigated by Rock-Eval pyrolysis and gas chro-matography--mass spectrometry(GC--MS).The data obtained from the source rocks evaluation showed that the rock samples contained type 1/III kerogen capable of generating oil and gas and were within immature to early mature stage.The relative abundance of the Cor,C1-and C2-dibenzofurans range from 1.75%to 29.82%,27.60%to 40.52%and 29.66%to 6889%,respectively.The diben-zofurans were dominated by C-dibenzofurans.Among the C1-dibenzofurans,2-+3-methyldibenzofuran was the most abundant in the rock samples while 1-methy ldibenzofuran appeared to be the least.The relative abundance of benzo[b]naphtho[1,2-d]furan(1,2]BNF),benzo[b]naph-tha[2,1-d]furan(2.1]BNF)and benzo[b]naphtha[2,3-d]fu-ran([2.3]BNF)in the rock extracts range from 12.01%to 52.58%,32.61%to 75.219%and 10.27%to 52.43%.The wide range of values recorded for the three isomers of benzo[b lnapthofurans in the samples suggest source rocks formed from mixed organic matter.Among the pheny ldibenzofuran isomers,4-pheny ldibenzofuran was the most abundant while 1-phenyldibenzofuran was the least.Phenyldibenzofuran ratio-1(PhFR-1)and pheny ldibenzofuran ratio-2(PhFR-2)values range from 0.13 to 1.20 and 0.11 to 2.11,respectively.The resuls showed that the relative abundance of PhFR-1 and PhFR-2 increase gradually with increasing burial depth and maturity(VRo≤0.77%,MPI-1≤0.62.Tmax s 443℃),and have a good correlations with calculated vitrinite reflectance.MPI-I and maximum Temperature(Tmax)-This range of values suggested immature to early mature source rocks.The source rocks were found to have shale and coul lithologics and deposited in a lacustrine/fuvial deltaic settings within immature to early mature stages based on the distribution of dibenzofurans,pheny ldiben-zofurans and benzo[b]naphthofurans in the source rocks.This study showed that dibenzof urans,phenyldibenzofu-rans and benzo[b]naphthofurans were ffcive in deter-mining the origin,depositional environment and thermal maturity of source rocks in Niger Delta basin,Nigeria.展开更多
This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered...This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WHO standards for drinking water. However, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, investments in infrastructure and an integrated management approach to ensure optimal basin-wide benefits.展开更多
Acidic aerosols resulting from gas flaring and refinery operations in the Niger Delta are a serious environmental and public health concern. Several thousand tons of flue gas components (dust particles, SO<sub>x...Acidic aerosols resulting from gas flaring and refinery operations in the Niger Delta are a serious environmental and public health concern. Several thousand tons of flue gas components (dust particles, SO<sub>x</sub>, CO and NO<sub>x</sub>) are released into the atmosphere by flaring billions of cubic meters of natural gas, refining and volatilizing the spilt oil. Heat wave is generated by flaring travels several meters away from flare points, destroying crops, farm lands, exotic species that are hunters delight while causing extinction of fragile soil flora and fuana. The occurrence of acid rain in the region implies that the natural receptors of the area are the final recipient of land and atmospheric pollutants. In effect, the water needs and public health of the populace are greatly impeded. Nitric and sulphuric acids are regarded as the sole contributors of nitrate and sulphate in precipitation influenced by combusted hydrocarbons: fine nitrate aerosols that dissolve in rain water are conversion products of NO<sub>2</sub> that arise from flaring, power plants and motor vehicles. Scientific evidence has shown that rain water and surface water quality in the Niger Delta can accentuate the poor health burden, and may be perpetuated through generations unborn. Diagnostic health risk assessment has revealed that drinking nitrate contaminated water may be associated with spontaneous miscarriage, ectopic pregnancy, adult malignant lymphomas, soft tissues sarcomas, cancers and lesions with added health burden associated with heavy metals and other ions. All these pose public health emergency and may significantly entrench health risk for generations to come. Therefore, this manuscript is intended to close certain gaps that were not covered by toxicological information and available data on environmental and food contamination and human internal exposure: it will serve as a continuous reminder and a useful guide to public health policy makers, workers and community based physicians.展开更多
The Niger Delta region has witnessed environmental impacts arising from oil production activities. Soil fertility in these areas and the entire marine habitat was investigated based on the re-occurring spill incidents...The Niger Delta region has witnessed environmental impacts arising from oil production activities. Soil fertility in these areas and the entire marine habitat was investigated based on the re-occurring spill incidents in the area to establish the consequences of oil pollution on key performance indicators as well as the remedial actions for resuscitation. One of the bases of evaluation was on the fertility profile of the area impacted by oil spills as compared with the areas without oil spills influence. A suitable cost effective and environmentally friendly technique to handle the pollutions in the Niger Delta region can be found in systematic containment, recovery, clean up and restoration of the marine habitat to its initial capacity and status to be able to sustain life once again.展开更多
An integrated interpretation of processed 3D seismic data,a suite of well logs,biostratigraphic data and core photographs of AMO Field,deep offshore Niger Delta,is carried out for the sequence stratigraphic analysis o...An integrated interpretation of processed 3D seismic data,a suite of well logs,biostratigraphic data and core photographs of AMO Field,deep offshore Niger Delta,is carried out for the sequence stratigraphic analysis of strata penetrated by wells.Lithologic and key stratigraphic surfaces,that is,the maximum flooding surfaces(MFSs)and sequence boundaries(SBs),are identified based on bioevents and log motifs.Biostratigraphic data help the delineation of MFSs and SBs,as well as dating,determination of depositional environment and paleobathymetry.The sequence stratigraphic study reveals seven MFSs(of 13.0 Ma,11.0 Ma,9.5 Ma,7.4 Ma,5.8 Ma,5.0 Ma and 2.7 Ma)and six SBs(of 12.1 Ma,10.3 Ma,8.5 Ma,6.3 Ma,5.5 Ma and 4.2 Ma).The key stratigraphic surfaces identified involve three depositional sequences characterized by lowstand,transgressive and highstand system tracts respectively.The studied section is deposited in a deepwater environment ranging from Lower to Upper Bathyal and can be dated back to the Middle Miocene-Middle Pliocene in age.Seven faults and two horizons(corresponding to reservoir units)are identified and mapped across the seismic data volume to establish a continuity of the reservoir to areas lacking well control.The established sequence stratigraphic framework displays successions of sediments(system tracts)where the reservoir sand units of the lowstand and highstand system tracts are of hydrocarbon prospective units in the field.展开更多
Objective:To investigate the level of heavy metals(Cu,Zn,Fe Mn Ni,Pb and Cd) in muscles,gills and liver tissue of Croaker fish from oil spilled rivers of Bonny and Finima,Niger Delta region,Nigeria.Methods:Twenty four...Objective:To investigate the level of heavy metals(Cu,Zn,Fe Mn Ni,Pb and Cd) in muscles,gills and liver tissue of Croaker fish from oil spilled rivers of Bonny and Finima,Niger Delta region,Nigeria.Methods:Twenty four Croacker fishes(Genyonemus lineatus) weighing between 250 and 260 g and 24–26 cm length were collected from each sampling sites(Bonny and finima rivers).The frozen fishes were thawed and dried at 105C until they reach a constant weight.The dried samples were homogenized and digested with 10 ml tri-acid mixture(HNO3:HCl O4:H2SO4),and then the digested samples were diluted to 100 ml with deionized water.Heavy metals(Cu,Ni,Zn,Pb,Mn,Iron Fe,and Cd) concentrations were determined by atomic absorption spectrophotometer.Results:Our results revealed that concentrations and distribution patterns of all heavy metals studied varied significantly(P < 0.05) amongst the fish tissues analyzed and sampling sites.Moreover,liver tissue of fish caught from Finima creek accumulated the highest concentrations of Cu(52.64 ± 3.01 mg/g dry wt),Zn(166.50 ± 6.45 mg/g dry wt)and Fe(801.50 ± 14.15 mg/g dry wt) in comparison to the liver of fish caught from Bonny river in which the levels of Cu,Zn and Fe were(45.00 ± 2.79),(49.90 ± 2.91) and(216 ± 6.11 mg/g dry wt),respectively.In addition,Mn,Ni,Pb and Cd exhibited their highest concentrations in gills from both locations.As expected,muscle tissue contained the least concentrations of all metals investigated from both sampling sites.Furthermore,all the metals investigated exhibited highest concentration in fish collected from Finima creek.These abnormal high level heavy metals accumulation observed in this location could be linked to the frequent crude oil spills as well as industrial activity around the area which might get discharged into Finima creek.In general,the mean concentrations of some toxic heavy metals investigated exceed the recommended maximum permissible limits set by the Joint FAO/WHO committee.However,some metals are within the acceptable limits.Conclusions:In conclusion,our data showed the abnormal higher concentration of these metals and this might be toxic to the fish and other aquatic organisms directly or by extension to humans that frequently consumed such contaminated fishes.展开更多
This paper reviews the significant contribution of hydrologic continuity in the development, evolution and fate of the Niger Delta. Formed from the aggregation of sediments from a drainage catchment area of over 2 mil...This paper reviews the significant contribution of hydrologic continuity in the development, evolution and fate of the Niger Delta. Formed from the aggregation of sediments from a drainage catchment area of over 2 million km<sup>2</sup>, the Niger Delta has evolved into a prolific sedimentary basin with a dense network of rivers and creeks. The ecological system is in a fragile state with fresh and saline water ecosystems maintaining a dynamic equilibrium. Rainfall typically varies from 2500 - 4000 mm per year compared to average annual evaporation of about 1500 mm, resulting in net antecedent moisture. Over 70% of the rainfall occurs in 4 months between May and September, creating a potential for flooding. Water level varies from less than 1.5 m in the estuaries to about 8 m at the apex of the delta, with Nun River having a slightly higher elevation compared to Forcados River, implying that canals connecting both rivers at the same reach would experience water movements from Nun to Forcados River. Similarly, water level gradients vary across the stretch of the rivers from 8.6 to 9.5 × 10<sup>-5</sup> (cm/km) between Onitsha and Asamabiri, 7.5 to 7.7 × 10<sup>-5</sup> (cm/km) on the Forcados River downstream of Asamabiri, and from 7.4 to 7.6 × 10<sup>-5</sup> (cm/km) on the Nun River. At peak flood, about 23 × 10<sup>3</sup> m<sup>3</sup>/sec of runoff enters the Niger Delta. At the same time, about 16 × 10<sup>3</sup> m<sup>3</sup>/sec discharges from the estuaries into the ocean in a semi-diurnal tidal flow leaving a surplus that accumulates to cause flooding. The delta thus acts like a sponge, absorbing the shear amount of flow and releasing slowly stored water through at least twenty-one outlet estuaries into the Atlantic Ocean. The shear amount of discharge overwhelms the capacity of the network of distributaries and predisposes the delta to flooding. Assessment of the capacity of the rivers to evacuate pollutants showed that rivers to the west of Brass which are fed by Forcados River exhibited relatively stronger flux efficiencies prior to 1998 but are presently weaker compared to rivers fed by Nun. The rivers to the east between New Calabar and Imo Rivers exhibited very weak ebb tide asymmetry or net upstream flow largely because these rivers receive little or no freshwater influx from upstream sources. Flood and erosion are the major hydrological hazards in the region.展开更多
An earlier study of GC-MS analysis on bitumen samples from the Agbabu area in Western Niger Delta showed the significant presence of gammacerane and no Oleanane and is suggested to be generated from the Lower Cretaceo...An earlier study of GC-MS analysis on bitumen samples from the Agbabu area in Western Niger Delta showed the significant presence of gammacerane and no Oleanane and is suggested to be generated from the Lower Cretaceous (Neocomian) source rock, however, twelve core samples were obtained from the geological survey of Nigeria for both optical geochemical and biomarker analysis, two of the samples from Isan-9 well indicated the presence of Botryococcus braunii a freshwater alga which is characteristic of a lacustrine lake type environment. The extracts from the same core showed m/z = 191 chromatogram with the significant presence of gammacerane which is diagnostic for stratified water columns and characterizes a typical lake environment. However, the m/z = 191 chromatogram also shows the presence of Oleanane which is diagnostic for vascular plant materials, this doesn’t corroborate with that of the Ise-2 well. The Isan-9 well source rock is suggested to have occurred due to the evolving structural geology of the continental shelf after the onset of the rifting, whereby the dominant lake-type environment in the Early Cretaceous was accompanied by a sediment fill of continental runoffs containing vascular plant materials. This implies that an ancient lacustrine lake system was gradually modified as a result of sedimentary infill. And that the bitumen is sourced from the lower Cretaceous Neocomian source rocks.展开更多
文摘Some problems of groundwater development in the Niger Delta ranging from negligence to geological peculiarities are examined to highlight the importance and application of geologic knowledge and research for decision making and averting failure in groundwater development for provisional use. Although the geology and hydrogeologic properties of the aquifer system in the Niger Delta immensely favors groundwater development, there are several recorded cases of failed groundwater development projects poor water quality, dry boreholes and boreholes with surprisingly low yield which could have been avoided. This is due to the perception that since groundwater is prolific, geologic and locational peculiarities can be ignored. This research has highlighted the importance of the knowledge of the hydrogeology of the different geologic units as significant factor in the success of groundwater projects through the correlation of past research of geologic units and groundwater potentials, quality and challenges with the present projects implemented in some of the locations. Cases where groundwater projects are executed with wrong exploration options and without consideration of the peculiarity of the geologic units of the project area, including engagement of incompetent contractors, and negligence to the existing regulatory framework for groundwater development in Nigeria are presented. In order to promote sustainable groundwater development and management in the Niger Delta, this research highlights and recommends the pragmatic use of geologic information including various technical, institutional, regulatory and management measures which have the capacity to avert challenges in groundwater development for provisional use.
文摘3D seismic and petrophysical log data interpretation of reservoir sands in “SIMA” Field, onshore Niger Delta has been undertaken in this study to ascertain the reservoir characteristics in terms of favourable structural and petrophysical parameters suitable for hydrocarbon accumulation and entrapment in the field. Horizon and fault interpretation were carried out for subsurface structural delineation. In all, seven faults (five normal and two listric faults) were mapped in the seismic section. These faults were major structure building faults corresponding to the growth and antithetic faults in the area within the well control. The antithetic fault trending northwest-southeast and the normal fault trending northeast-southwest on the structural high in the section act as good trapping mechanisms for hydrocarbon accumulations in the reservoir. From the manual and auto-tracking methods applied, several horizons were identified and mapped. The section is characterized by high amplitude with moderate-to-good continuity reflections appearing parallel to sub-parallel, mostly disturbed by some truncations which are more fault related than lithologic heterogeneity. The southwestern part is, however, characterized by low-to-high or variable amplitude reflections with poor-to-low continuity. Normal faults linked to roll-over anticlines were identified. Some fault truncations were observed due to lithologic heterogeneity. The combination of these faults acts as good traps for hydrocarbon accumulations in the reservoir. Reservoir favourable petrophysical qualities, having average NTG, porosity, permeability and water saturation of 5 m, 0.20423, 1128.219 kD and 0.458 respectively.
文摘This paper evaluates the hydrocarbon prospectivity and play risks of “Bob” field in Niger Delta Basin, Nigeria. The aim is to enhance exploration success through improved approach/technique by incorporating risk analysis that previous studies have not fully considered. This approach combines a set of analyses including stratigraphic/structural, amplitude, petrophysical parameter, volumetric and play risk using a suite of well logs and 3D seismic data. Maximum amplitude anomaly map extracted on the surfaces of delineated 3 reservoirs revealed 6 prospects, namely: Dippers, Cranes, Turacos, Nicators, Jacanas and Pelicans with hydrocarbon accumulation. Petrophysical analysis showed ranges of values for porosity, permeability and water saturation of 0.21 to 0.23, 158.96 to 882.39 mD, and 0.07 to 0.11, respectively. The various prospects yielded the following stock tank volumes 12.73, 6.84, 3.84, 11.32, 7.42 and 4.76 Million barrels (Mbls) each respectively in a column of 66 ft reservoir sand in the study area. Play risk analysis results gave: Pelicans and Nicators (low), Turacos and Dippers (moderate), while Jacanas and Cranes show high risk with minimal promise for good oil accumulation. The prospects possess good reservoir petrophysical properties with low to moderate risk, thus, viable for commercial hydrocarbon production, which increases confidence in management decisions for production.
文摘Integrated modelling, well correlation and petrophysical analysis were performed to characterize the reservoirs for optimum hydrocarbon correlation using 3-D seismic reflection data and suites of well logs from Ataga 5, 7, 10 and 11 wells respectively in Ataga field, shallow offshore, Niger Delta Basin, Nigeria. The study revealed the presence of two viable hydrocarbon bearing reservoirs, AT1 and AT2 and the average values of porosity, permeability, water saturation, hydrocarbon saturation, Net to Gross (NTG) and volume of shale are in the ranges of 15% - 77%, 44.5% - 75.5%, 25.5% - 85%, 15% - 75.5%, 0.70 - 0.88 and 0.11 - 0.38 respectively which goes further to show that the both reservoirs have fair characteristics that are suggestive of the presence of hydrocarbon accumulation. It can therefore be deduced that the permeability values are reflective of fair interconnectivity of pore spaces of sands within the well areas and their ability to transmit fluids, the depth and depth structural map generated for the horizons and structures shows that the most dominant trapping mechanism in the area under study is the crescentic growth fault and the rollover anticlines trending in the Northwest-Southeast direction and from the volumetric analysis. It can be deduced that the recoverable gas for AT1 and AT2 reservoirs is 2 × 10<sup>6</sup> mscf and 6 × 10<sup>6</sup> mscf respectively.
文摘Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for development purposes and to meet construction needs in the region. There is currently no regulation as to where sand can be mined in river channels because of the lack of adequate understanding of the risks to coastal infrastructure involved with its abstraction. The phenomenon of bridge Abutment and bank failure induced by excessive dredging of sand river bed is considered. Two types of instability were distinguished, one relating to the equilibrium slope of the riverbed and the other riverbank instability. An empirical relationship in the form X<sub>s</sub> = 3Htan(90 - α) has been developed through analysis, supported by examples that a minimum distance of 94 m (for sand river beds) from a bridge should be observed for sand abstraction in order to guaranty the safety of bridge foundation. For clay riverbeds, slightly shorter minimum distances can be considered safe. The study further shows that the capacity of sand borrowing in river channels to generate bank instability is dependent on the composition and stratigraphy beneath the river bed.
文摘Despite exploration and production success in Niger Delta,several failed wells have been encountered due to overpressures.Hence,it is very essential to understand the spatial distribution of pore pressure and the generating mechanisms in order to mitigate the pitfalls that might arise during drilling.This research provides estimates of pore pressure along three offshore wells using the Eaton's transit time method,multi-layer perceptron artificial neural network(MLP-ANN)and random forest regression(RFR)algorithms.Our results show that there are three pressure magnitude regimes:normal pressure zone(hydrostatic pressure),transition pressure zone(slightly above hydrostatic pressure),and over pressured zone(significantly above hydrostatic pressure).The top of the geopressured zone(2873 mbRT or 9425.853 ft)averagely marks the onset of overpressurization with the excess pore pressure above hydrostatic pressure(P∗)varying averagely along the three wells between 1.06−24.75 MPa.The results from the three methods are self-consistent with strong correlation between the Eaton's method and the two machine learning models.The models have high accuracy of about>97%,low mean absolute percentage error(MAPE<3%)and coefficient of determination(R2>0.98).Our results have also shown that the principal generating mechanisms responsible for high pore pressure in the offshore Niger Delta are disequilibrium compaction,unloading(fluid expansion)and shale diagenesis.
文摘The influence of origin, depositional environment and thermal maturity of organic matter on the occurrence of aromatic hydrocarbons in source rocks from the central and northwestern Niger Delta was investigated. Eighty two source rock samples from four oil wells in the central and northwestern Niger Delta were analyzed for the aromatic hydrocarbon content using gas chromatography-mass spectrometry (GC-MS). The results of analysis of aromatic hydrocarbon fractions of the source rock extracts show the presence of many classes of aromatic hydrocarbons, which include naphthalenes, phenanthrenes, biphenyls, dibenzothiophenes and fluorenes. Trimethylnaphthalene (TMN) is the most abundant among the naphthalenes while dimethylphenanthrene (DMP) is the most abundant among the phenanthrenes. Among the biphenyls, 3-methylbiphenyl (3 MB) is the most abundant while 4-methyldibenzothiophene (4MDBT) is the most abundant among the dibenzothiphenes. Only two fluorenes were detected, and fluorene is more in abundance than 1-methylfluorene (1 MF). Depositional environment indicators of aromatic hydrocarbon organic matter reveal that the organic materials in the source rocks in these wells were deposited in marine-to-swamp depositional environments under reducing to suboxic conditions. Thermal maturity indicators calculated from the abundance of the aromatic hydrocarbons indicate that the source rock samples are thermally mature. Most of the source rocks are at the peak of oil window while a few at the early oil window. Source rocks from wells GB, OP and OT in the central Niger Delta are thermally more mature than those from well AW in the northwestern Niger Delta.
基金supported by Open Fund(PLC201203)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Chengdu University of Technology)National Science and Technology Major Project(2011ZX05030-005)Major Project of Education Department in Sichuan Province(13ZA0177)
文摘This paper studied an architecture model of turbidite channel systems based on the shallow- layer high resolution 3D seismic information in the deepwater area in the Niger Delta continental slope, West Africa as a prototype model. Different types of channel systems were identified and the corresponding architecture models were established. The controlling factors, evaluation criteria and spatial distribution of different channel systems were analyzed. This study shows that turbidite channel systems of West Africa could be classified into three types; confined, semi-confined and unconfined, according to the condition of canyon and the levees on both sides. Oil one hand, along the transport direction, channel system evolves from confined to unconfined. Within channel systems, channel complexes, including two types of incised and enveloped, are the most important reservoir bodies. On the other hand, there is a channel complex evolution from incised to enveloped vertically. The geological factors exert impacts of different levels on the architecture of the turbidite channels in different sedimentary systems or even within the same system.
基金granted by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No.2011ZX05030-005 and No.2011ZX05009-003)the National Natural Science Foundation of China (Grant No. 40902035)
文摘Deep-water turbidite channels have attracted much attention as a focused issue in petroleum exploration and development. Extensive studies have been performed on the architecture of turbidite channels, and most researches have focused on their geometric shapes, sedimentary processes and controlling factors. However, little attention has been paid to the distribution patterns, distribution laws and quantitative studies of composite sand bodies of turbidite channels. Taken one slope area of the Niger Delta Basin as an example, this study conducted a semi-quantitative to quantitative analysis on architecture of composite sand bodies of turbidite channels based on cores, well logging and seismic surveys. It is shown that turbidite channel systems can be classified as confined and unconfined channel systems. For confined channel systems, the vertical evolution process involves four stages. The sinuosity of a channel system is controlled by slope, with a negative power function relationship between them. When slope gradient reaches four degrees, the channel system is nearly straight. Based on the migration direction and migration amount of single channels within channel complexes, channel composite patterns can be divided into four classes(the lateral composite, en-echelon composite, swing composite and vertical composite) and several subclasses. Various channel composite patterns show specific distribution laws spatially. For meandering channel complexes at the middle-late evolution stage of confined channel systems, the lateral migration amongst single channels shows the features of integrity and succession. The sinuosity of single channels in the late period is greater than that in the early period, and cut-offs may occur locally when the sinuosity is larger than five degrees. This study provides a better understanding for the geological theory of deep-water sedimentary, and also improves exploitation benefits of this type of reservoirs.
文摘Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the geochemical significance of tricyclic and tetracyclic terpanes in source rock extracts from the Offshore Niger Delta Bain,Nigeria with gas chromatography-mass spectrometry(GC-MS).The total relative abundances of tricyclic terpanes,C_(19)TT-C_(21)TT,and C_(23) TT in the rock samples ranged from 82.50 to 96.37%,50.08 to 74.17%,and 25.83 to 49.92%,respectively.These values showed the source rocks were formed from a mixed origin(terrestrial and marine).Among the tricyclic and tetracyclic terpanes identified in the rock extracts,the conventional(C_(20)TT,C_(23)TT,C_(24)TT,C_(24)TeT)and recent(Y1,X1,Z1)were more prominent than all others,indicating mixed input of terrigenous and marine organic matter.The C_(24)TT/C_(23)TT,C_(24)TeT/(C_(24)TeT+C_(26)TT),C_(19)TT/C_(23)TT,C_(20)TT/C_(23)TT,C_(25)TT/C_(24)TeT,C_(25)TT/C_(26)TT,C_(19)TT/C_(20)TT,C_(24)TeT/C_(26)TT,Z1/(Z1+C_(24)TT),and Y1/(Y1+C_(24)TT)in the rock samples range from 0.33 to 1.30,0.76 to 0.90,0.18 to 0.73,0.34 to 1.05,0.33 to 1.74,0.30 to 1.39,0.31 to0.89,1.66 to 4.33,0.36 to 0.83,and 0.34 to 0.79,respectively.These values further showed that the rock samples were formed from mixed input of terrigenous and marine organic matter and deposited under oxic to suboxic conditions in lacustrine-fluvial/deltaic environments.Also,the C_(24)TeT/C_(20)-26TT,C_(24)TeT/C_(30)HOP,and C_(23)TT/C_(30)HOP ranged from 0.16 to 0.45,0.02 to 0.42,and 0.01 to 0.48,respectively.This range of values suggests that source rocks were within immature to early mature stage.Thus,this study showed that tricyclic and tetracyclic terpanes were effective in determining the origin,depositional environments,and thermal maturity of source rocks in the Niger Delta Basin,Nigeria.
文摘Thirty-nine crude oils and twenty-one rock samples from Niger Delta Basin,Nigeria have been characterized based on their isotope compositions by elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry.The bulk carbon isotopic values of the whole rock extracts,saturate and aromatic fractions range from–28.7‰to–26.8‰,–29.2‰to–27.2‰and–28.5‰to–26.7‰,respectively while the bulk carbon isotopic values of the whole oils,saturate and aromatic fractions range from–25.4‰to–27.8‰,–25.9‰to–28.4‰and–23.5‰to–26.9‰,respectively.The average carbon isotopic compositions of individual alkanes(nC12-nC33)in the rock samples range from–34.9‰to–28.2‰whereas the average isotopic values of individual n-alkanes in the oils range from–31.1‰to–23.8‰.Theδ13C isotope ratios of pristane and phytane in the rock samples range from–29.2‰to–28.2‰and–30.2‰to–27.4‰respectively while the pristane and phytane isotopic values range from–32.1‰to–21.9‰and–30.5‰to–26.9‰,respectively.The isotopic values recorded for the samples indicated that the crude oils were formed from the mixed input of terrigenous and marine organic matter and deposited under oxic to sub-oxic condition in lacustrine-fluvial/deltaic environments.The stable carbon isotopic compositions were found to be effective in assessing the origin and depositional environments of crude oils in the Niger Delta Basin.
基金supported by the National Planned Major Science and Technology Projects of China(grant No.2011ZX05030-005-02)
文摘Objective The term "pockmark" was introduced by King and MacLean (1970) to describe small "circular" on echosounder records in Nova Scotia. described as circular, near Pockmarks are usually circular or elongated depressions, generally 10--400 m in diameter and 30-50 m in deep. Pockmarks are normally regarded to be manifestations of fluids escape through the seabed. Pockmarks are valuable features on the seafloor and are useful in constraining the hydrodynamics of sedimentary basins. Since then pockmarks have been recognized in many areas around the world. They occur predominantly in fine-grained siliciclastic depositional settings, although a few case studies have been reported in carbonate settings. In this paper we illustrate a suite of fluid escape features, discovered during the course of petroleum exploration on the West Africa continental margin (Fig. 1). They are particularly of interest to the oil and gas industry because they could be potential indicators of deeply buried hydrocarbon reservoirs, and fluid flow phenomena in the deep water oilfield are important for the safe and efficient exploration, development and production of hydrocarbons in the area.
基金The authors gratefully acknowledge the State Key Laboratory of Petroleum Resources and Prospecting,College of Geoscience,China University of Petroleum,Beijing,China for granting A.B.Ogbesejana an international visiting research fellowship towards this research work.
文摘The distribution and geochemical significance of dibenzofurans,phenyldibenzofurans and benzo[b]naptho-furans in source rocks from Niger Delta basin,Nigeria,were investigated by Rock-Eval pyrolysis and gas chro-matography--mass spectrometry(GC--MS).The data obtained from the source rocks evaluation showed that the rock samples contained type 1/III kerogen capable of generating oil and gas and were within immature to early mature stage.The relative abundance of the Cor,C1-and C2-dibenzofurans range from 1.75%to 29.82%,27.60%to 40.52%and 29.66%to 6889%,respectively.The diben-zofurans were dominated by C-dibenzofurans.Among the C1-dibenzofurans,2-+3-methyldibenzofuran was the most abundant in the rock samples while 1-methy ldibenzofuran appeared to be the least.The relative abundance of benzo[b]naphtho[1,2-d]furan(1,2]BNF),benzo[b]naph-tha[2,1-d]furan(2.1]BNF)and benzo[b]naphtha[2,3-d]fu-ran([2.3]BNF)in the rock extracts range from 12.01%to 52.58%,32.61%to 75.219%and 10.27%to 52.43%.The wide range of values recorded for the three isomers of benzo[b lnapthofurans in the samples suggest source rocks formed from mixed organic matter.Among the pheny ldibenzofuran isomers,4-pheny ldibenzofuran was the most abundant while 1-phenyldibenzofuran was the least.Phenyldibenzofuran ratio-1(PhFR-1)and pheny ldibenzofuran ratio-2(PhFR-2)values range from 0.13 to 1.20 and 0.11 to 2.11,respectively.The resuls showed that the relative abundance of PhFR-1 and PhFR-2 increase gradually with increasing burial depth and maturity(VRo≤0.77%,MPI-1≤0.62.Tmax s 443℃),and have a good correlations with calculated vitrinite reflectance.MPI-I and maximum Temperature(Tmax)-This range of values suggested immature to early mature source rocks.The source rocks were found to have shale and coul lithologics and deposited in a lacustrine/fuvial deltaic settings within immature to early mature stages based on the distribution of dibenzofurans,pheny ldiben-zofurans and benzo[b]naphthofurans in the source rocks.This study showed that dibenzof urans,phenyldibenzofu-rans and benzo[b]naphthofurans were ffcive in deter-mining the origin,depositional environment and thermal maturity of source rocks in Niger Delta basin,Nigeria.
文摘This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WHO standards for drinking water. However, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, investments in infrastructure and an integrated management approach to ensure optimal basin-wide benefits.
文摘Acidic aerosols resulting from gas flaring and refinery operations in the Niger Delta are a serious environmental and public health concern. Several thousand tons of flue gas components (dust particles, SO<sub>x</sub>, CO and NO<sub>x</sub>) are released into the atmosphere by flaring billions of cubic meters of natural gas, refining and volatilizing the spilt oil. Heat wave is generated by flaring travels several meters away from flare points, destroying crops, farm lands, exotic species that are hunters delight while causing extinction of fragile soil flora and fuana. The occurrence of acid rain in the region implies that the natural receptors of the area are the final recipient of land and atmospheric pollutants. In effect, the water needs and public health of the populace are greatly impeded. Nitric and sulphuric acids are regarded as the sole contributors of nitrate and sulphate in precipitation influenced by combusted hydrocarbons: fine nitrate aerosols that dissolve in rain water are conversion products of NO<sub>2</sub> that arise from flaring, power plants and motor vehicles. Scientific evidence has shown that rain water and surface water quality in the Niger Delta can accentuate the poor health burden, and may be perpetuated through generations unborn. Diagnostic health risk assessment has revealed that drinking nitrate contaminated water may be associated with spontaneous miscarriage, ectopic pregnancy, adult malignant lymphomas, soft tissues sarcomas, cancers and lesions with added health burden associated with heavy metals and other ions. All these pose public health emergency and may significantly entrench health risk for generations to come. Therefore, this manuscript is intended to close certain gaps that were not covered by toxicological information and available data on environmental and food contamination and human internal exposure: it will serve as a continuous reminder and a useful guide to public health policy makers, workers and community based physicians.
文摘The Niger Delta region has witnessed environmental impacts arising from oil production activities. Soil fertility in these areas and the entire marine habitat was investigated based on the re-occurring spill incidents in the area to establish the consequences of oil pollution on key performance indicators as well as the remedial actions for resuscitation. One of the bases of evaluation was on the fertility profile of the area impacted by oil spills as compared with the areas without oil spills influence. A suitable cost effective and environmentally friendly technique to handle the pollutions in the Niger Delta region can be found in systematic containment, recovery, clean up and restoration of the marine habitat to its initial capacity and status to be able to sustain life once again.
文摘An integrated interpretation of processed 3D seismic data,a suite of well logs,biostratigraphic data and core photographs of AMO Field,deep offshore Niger Delta,is carried out for the sequence stratigraphic analysis of strata penetrated by wells.Lithologic and key stratigraphic surfaces,that is,the maximum flooding surfaces(MFSs)and sequence boundaries(SBs),are identified based on bioevents and log motifs.Biostratigraphic data help the delineation of MFSs and SBs,as well as dating,determination of depositional environment and paleobathymetry.The sequence stratigraphic study reveals seven MFSs(of 13.0 Ma,11.0 Ma,9.5 Ma,7.4 Ma,5.8 Ma,5.0 Ma and 2.7 Ma)and six SBs(of 12.1 Ma,10.3 Ma,8.5 Ma,6.3 Ma,5.5 Ma and 4.2 Ma).The key stratigraphic surfaces identified involve three depositional sequences characterized by lowstand,transgressive and highstand system tracts respectively.The studied section is deposited in a deepwater environment ranging from Lower to Upper Bathyal and can be dated back to the Middle Miocene-Middle Pliocene in age.Seven faults and two horizons(corresponding to reservoir units)are identified and mapped across the seismic data volume to establish a continuity of the reservoir to areas lacking well control.The established sequence stratigraphic framework displays successions of sediments(system tracts)where the reservoir sand units of the lowstand and highstand system tracts are of hydrocarbon prospective units in the field.
文摘Objective:To investigate the level of heavy metals(Cu,Zn,Fe Mn Ni,Pb and Cd) in muscles,gills and liver tissue of Croaker fish from oil spilled rivers of Bonny and Finima,Niger Delta region,Nigeria.Methods:Twenty four Croacker fishes(Genyonemus lineatus) weighing between 250 and 260 g and 24–26 cm length were collected from each sampling sites(Bonny and finima rivers).The frozen fishes were thawed and dried at 105C until they reach a constant weight.The dried samples were homogenized and digested with 10 ml tri-acid mixture(HNO3:HCl O4:H2SO4),and then the digested samples were diluted to 100 ml with deionized water.Heavy metals(Cu,Ni,Zn,Pb,Mn,Iron Fe,and Cd) concentrations were determined by atomic absorption spectrophotometer.Results:Our results revealed that concentrations and distribution patterns of all heavy metals studied varied significantly(P < 0.05) amongst the fish tissues analyzed and sampling sites.Moreover,liver tissue of fish caught from Finima creek accumulated the highest concentrations of Cu(52.64 ± 3.01 mg/g dry wt),Zn(166.50 ± 6.45 mg/g dry wt)and Fe(801.50 ± 14.15 mg/g dry wt) in comparison to the liver of fish caught from Bonny river in which the levels of Cu,Zn and Fe were(45.00 ± 2.79),(49.90 ± 2.91) and(216 ± 6.11 mg/g dry wt),respectively.In addition,Mn,Ni,Pb and Cd exhibited their highest concentrations in gills from both locations.As expected,muscle tissue contained the least concentrations of all metals investigated from both sampling sites.Furthermore,all the metals investigated exhibited highest concentration in fish collected from Finima creek.These abnormal high level heavy metals accumulation observed in this location could be linked to the frequent crude oil spills as well as industrial activity around the area which might get discharged into Finima creek.In general,the mean concentrations of some toxic heavy metals investigated exceed the recommended maximum permissible limits set by the Joint FAO/WHO committee.However,some metals are within the acceptable limits.Conclusions:In conclusion,our data showed the abnormal higher concentration of these metals and this might be toxic to the fish and other aquatic organisms directly or by extension to humans that frequently consumed such contaminated fishes.
文摘This paper reviews the significant contribution of hydrologic continuity in the development, evolution and fate of the Niger Delta. Formed from the aggregation of sediments from a drainage catchment area of over 2 million km<sup>2</sup>, the Niger Delta has evolved into a prolific sedimentary basin with a dense network of rivers and creeks. The ecological system is in a fragile state with fresh and saline water ecosystems maintaining a dynamic equilibrium. Rainfall typically varies from 2500 - 4000 mm per year compared to average annual evaporation of about 1500 mm, resulting in net antecedent moisture. Over 70% of the rainfall occurs in 4 months between May and September, creating a potential for flooding. Water level varies from less than 1.5 m in the estuaries to about 8 m at the apex of the delta, with Nun River having a slightly higher elevation compared to Forcados River, implying that canals connecting both rivers at the same reach would experience water movements from Nun to Forcados River. Similarly, water level gradients vary across the stretch of the rivers from 8.6 to 9.5 × 10<sup>-5</sup> (cm/km) between Onitsha and Asamabiri, 7.5 to 7.7 × 10<sup>-5</sup> (cm/km) on the Forcados River downstream of Asamabiri, and from 7.4 to 7.6 × 10<sup>-5</sup> (cm/km) on the Nun River. At peak flood, about 23 × 10<sup>3</sup> m<sup>3</sup>/sec of runoff enters the Niger Delta. At the same time, about 16 × 10<sup>3</sup> m<sup>3</sup>/sec discharges from the estuaries into the ocean in a semi-diurnal tidal flow leaving a surplus that accumulates to cause flooding. The delta thus acts like a sponge, absorbing the shear amount of flow and releasing slowly stored water through at least twenty-one outlet estuaries into the Atlantic Ocean. The shear amount of discharge overwhelms the capacity of the network of distributaries and predisposes the delta to flooding. Assessment of the capacity of the rivers to evacuate pollutants showed that rivers to the west of Brass which are fed by Forcados River exhibited relatively stronger flux efficiencies prior to 1998 but are presently weaker compared to rivers fed by Nun. The rivers to the east between New Calabar and Imo Rivers exhibited very weak ebb tide asymmetry or net upstream flow largely because these rivers receive little or no freshwater influx from upstream sources. Flood and erosion are the major hydrological hazards in the region.
文摘An earlier study of GC-MS analysis on bitumen samples from the Agbabu area in Western Niger Delta showed the significant presence of gammacerane and no Oleanane and is suggested to be generated from the Lower Cretaceous (Neocomian) source rock, however, twelve core samples were obtained from the geological survey of Nigeria for both optical geochemical and biomarker analysis, two of the samples from Isan-9 well indicated the presence of Botryococcus braunii a freshwater alga which is characteristic of a lacustrine lake type environment. The extracts from the same core showed m/z = 191 chromatogram with the significant presence of gammacerane which is diagnostic for stratified water columns and characterizes a typical lake environment. However, the m/z = 191 chromatogram also shows the presence of Oleanane which is diagnostic for vascular plant materials, this doesn’t corroborate with that of the Ise-2 well. The Isan-9 well source rock is suggested to have occurred due to the evolving structural geology of the continental shelf after the onset of the rifting, whereby the dominant lake-type environment in the Early Cretaceous was accompanied by a sediment fill of continental runoffs containing vascular plant materials. This implies that an ancient lacustrine lake system was gradually modified as a result of sedimentary infill. And that the bitumen is sourced from the lower Cretaceous Neocomian source rocks.