Southeastern Niger Delta Research Articles

Source Rock Evaluation of Shale in Parts of Ini Local Government Area, Akwa Ibom State, Southeastern Niger Delta Basin, Nigeria

Total organic carbon and Rock – Eval pyrolysis studies were conducted on seven (7) shale samples outcropping in parts of Ini Local Government Area of Akwa Ibom State, Southeastern Niger Delta, Nigeria. The studies were done to determine the quantity and quality of organic matter in the shale source rock, and their hydrocarbon generation potential. Total organic carbon (TOC) values indicate poor to excellent organic richness with values ranging from 0.46 wt.% to 5.98 wt.%. The free oil content (S1) values range from 0.02-0.21 mg HC/g rock, (mean = 0.07 mg HC/g rock), while the source rock potential (S2) ranges from 0.08-1.09 mg HC/g rock with an average value of 0.45 mg HC/g rock both indicating poor source rock generative potential. The Hydrogen Index (HI) and the Oxygen Index (OI) range from 11 mg HC/g TOC to 59 mg HC/g TOC and 41 mg CO/g TOC to 74 mg CO/g TOC with an average value of 27.28 mg HC/g TOC and 55.71 mg CO/g TOC respectively. HI versus OI and S2 versus TOC cross plot results indicate that shale in parts of Ini Local Government Area contains organic matter capable of generating kerogen type III to type 1V which is gas prone.

Palynostratigraphy and Palaeoenvironmental Interpretation of Outcrop Formations in Parts of Ini-Akwa Ibom State, Southeastern Niger Delta Basin, Nigeria

The palynological study of the outcrop Formations in parts of Ini Local Government Area of Akwa Ibom State, Southeastern Niger Delta Basin, Nigeria has contributed to unraveling the palynostratigraphy and paleoenvironments of the outcrops through the use of diagnostic palynomorphs. The section is made up of carbonaceous shales, sandstones, mudstones and claystones. The conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments was used to prepare twenty outcrop samples for palynological studies. The samples produced poor to fair diversity assemblages of palynomorphs. A total of 176 palynomorphs species were recorded, with 48% pollen grains, 33% spores, 12% dinoflagellate cysts, 5% fungal spores, and 2% microforam test wall linings. Based on stratigraphically selected index taxa recovered,age determination and correlation wereestablished. The samples from Imo Formation were assigned Late Paleocene-Eocene based on Psilatricolporites Crassus, Retitricolporites irregularies, Psilatricolporites sp. and Leiotriletes adriennis with the presence of Paleocene dinoflagellate cysts such as Lejeunacysta beninensis and Selenopemphix nephroides. Ameki samples were dated Early-Middle Eocene based on Proxapertites operculatus, Retistephanocolpites williamsi, Mauritidites crassiexinius, Monocolpites marginatus and Longapertites marginatus. Ogwashi-Asaba shale samples were assigned Late Eocene-Early Oligocene due to the abundant presence of Verrucatosporites usmensis, Laevigatosporites discordatus and Retitricolporites irregularis while Eze-Aku samples were tentatively assigned Paleocene because of the presence of two pollen index fossils Proxapertites operculatus and Pachydermites diederixi. Inferred depositional conditions suggest that Imo Formation was deposited in a shallow marine or near shore brackish water estuarine environment. The Ameki Formation was accumulated in a marginal marine or near shore, brackish water-estuarine environment in the upper deltaic setting. The Ogwashi-Asaba Formation was deposited in a progradational shoreline moving between the brackish water and fresh water deltaic plain. The Eze-Aku Formation was deposited in an upper foreshore fresh water environment. The palynological study of the samples are Paleogene Formations while the paleoenvironment is in a costal deltaic to shallow-marine environment and are appropriate for hydrocarbon accumulations and exploration.

Core sediments and oil chemistry from contaminated mangroves in eastern Niger Delta, Ogoniland, Nigeria

Thirty cores to maximum depth of 3.7 m were taken in 2018 to investigate sedimentary characteristics and hydrocarbon penetration within mangrove sediments in Bodo (southeastern Niger Delta), an area contaminated by numerous ongoing oil spills but most significantly in 2008. Sediments were dominated by organically rich (Chikoko) mud underlain by clay with sandier sediments at deeper core depths and adjacent to shorelines. Analysis of 202 samples showed high median hydrocarbon concentrations at the surface (39,000 mg/kg) and shallow subsurface (10–25 cm, 25,000 mg/kg), decreasing with depth: 430 mg/kg at 40–70 cm; 157 mg/kg at 75–120 cm, and <30 mg/kg at depths ≥150 cm. Most (85%) EPA-16 priority polycyclic aromatic hydrocarbons and all monoaromatics were below detection limit. Shallow subsurface oil penetration was aided by crab burrows and presence of mangrove remnants and was inhibited from deeper depths by groundwater at ~25 cm and increased sediment compaction.

Effects of anisotropic changes on the conductivity of sedimentary aquifers, southeastern Niger Delta, Nigeria

Sundry soils/rocks are characterized by electrical properties with clearly or obscurely expressed anisotropies. These anisotropic effects may be low, moderate or high depending on the coefficient of anisotropy (λ). The vertical electrical sounding technique employing Schlumberger electrode configuration and lithological information from boreholes were deployed to characterize the lithological diversity in homogeneous and anisotropic geologic units that serve as aquifer systems and their overlaying layers in the coastal region of Akwa Ibom State. Based on the $$\lambda$$ , the assessed volume of sedimentary formation is classified into low anisotropy λ < 1.2, moderate anisotropy $$\left( {1.2 < \lambda \le 1.3} \right)$$ and high anisotropy $$\left( {\lambda > 1.3} \right)$$ with alluvium (64.3%), inter-bedded shale and sandstone (14.3%) and shale and slate (21.3%). The estimated percentage of respective compositional coverage indicates that alluvium is dominant, while the blended inter-bedded shale and sandstone as well as the shale and slate are minor geologic units in the Benin Formation. Inferred index of spread of alluvium indicates that the homogeneous and anisotropic units assessed are intrinsic/microscopic in nature as identified by the impressed current that passed through geologic system. The results showcased that the plot between the strike-dependent resistivity $$\left( {\rho_{\theta } } \right)$$ at arbitrary chosen strike and geometric mean resistivity $$\left( {\rho_{m} } \right)$$ can be used as a yardstick for inferring the degree of consistency of geologic compositions in homogeneous and anisotropic media. Both the quantitative (graphic) and qualitative (contour) results portend the thin possibility of having anisotropy free geologic units. The finding proposes that ground resistivity measurements and interpretations of geologic structures should be constrained by borehole information in order to firm up the intended plans for obtaining clearer, defendable and well-resolved subsurface structures.

Effects of oil spillage on soils nutrients of selected communities in Ogoniland, south-eastern Niger Delta, Rivers State, Nigeria

Effects of oil spillage on soils nutrients of selected communities in Ogoniland, south-eastern Niger Delta, Rivers State, Nigeria

Whole-oil relationship and origin of oil derived from heterogeneous reservoir systems in an offshore field, SE, Niger Delta

Whole-oil (C3–C39) gas chromatograms were obtained for 46 oil samples collected from a reservoirs pool in an oilfield located offshore SE Niger Delta, to investigate the origins and the relationships of the oils, in spite of the discontinuity of the reservoirs from which the oils were produced. All the oils contained hydrocarbons in the range C3–C39 with prominent pristane and phytane. The plot of pristine: nC17 versus phytane: nC18 shows oils of terrestrial origin that is deposited in an oxidizing environment. However, some of the oils show depletion of n-paraffin in the C5–C11 range and have abundant n-paraffin in the C12–C35 range suggesting biodegraded oils. The isoprenoid peaks, however, are more prominent than adjacent n-paraffin in some of the other oils. A star plot of the ratios derived from napthenic, aromatic, isoprenoid, and normal alkane compounds of the samples, in addition to the above-mentioned variations, allowed the grouping of the oils into three families. The results infer that the oils from the south eastern Niger delta may be related in some way (in terms of source input) but may have undergone slightly different histories due to reservoir discontinuity.

The effect of anisotropy on amplitude versus offset (AVO) synthetic modelling in Derby field southeastern Niger delta

The effect of anisotropy on AVO synthetic modelling in Niger delta Derby field has been attempted. The objective of the study is to determine if anisotropic synthetic model can improve amplitude versus offset (AVO) analysis of CDP gathers by comparing them with isotropic synthetic model over shale-gas sand boundaries. Well logs and common depth point (CDP) processed gathers were used for the analysis. The result of the present study revealed that reservoirs in Derby field are overlain by intrinsically anisotropic shale and as such, anisotropic synthetic modelling yields the best fit to CDP gathers than the isotropic synthetic model. However, in conventional processing for AVO analysis, isotropic rather than anisotropic earth models are usually assumed, which could possibly affect the outcome of an AVO-based analysis at large offsets. Therefore, the effect of anisotropy should be incorporated and properly accounted for using the anisotropic synthetic modelling in the processing and interpretation workflows for quantitative AVO analysis in Niger delta to optimise hydrocarbon recovery.

Lipid Biomarker Analysis of Suspended Particulate Matter from the Great Kwa River, SE Nigeria: Origins and Environmental Implications of Biogenic and Anthropogenic Organic Compounds

Biomarkers found in natural waters, sediments, soils, fossils, crude oil, and coal can be unambiguously linked to specific precursors biosynthesized by biota. Petroleum and its refinery products carry their biomarker information into the environment when they are released by pollution. Lipid biomarkers can be used to assess the environmental status of an ecosystem and the degree to which it has been influenced by biogenic and anthropogenic inputs. The marine ecosystem of the southeastern Niger Delta of Nigeria is receiving new attention due to increased human and industrial development and the consequent potential health effects. Suspended particulate matter (SPM) from the Great Kwa River was characterized using biomarkers to assess such pollution. The total organic carbon contents of SPM from the river at low and high tide was 12–50% (avg 34.75%) and 16–28% (avg 24.25%), respectively. The lipid biomarkers identified using gas chromatography–mass spectrometry were mainly n-alkanes, n-alkan-2-ones, triterpenoids and minor amounts of aromatic compounds. The n-alkanes ranged from C 17 to C 35, with an odd/even predominance and C max > 27, indicating a mixed origin from higher plant wax, biodegraded detritus, and petroleum. The n-alkan-2-ones in most samples ranged from C 16 to C 33, with C max = 31, also supporting an input from vascular plants dominating the riparian zone along the river. The triterpenoids, mainly taraxerone, taraxerol, α- and β-amyrins, and friedelin, also derived from higher plants (angiosperms). Minor amounts of aromatic hydrocarbon derivatives from α- and β-amyrins were present and are likely the result of different diagenetic processes. The presence of trace fossil fuel-derived hopanes with an unresolved complex mixture of branched and cyclic hydrocarbons supported a minor petroleum product input to the SPM of the Great Kwa River.

Plane Versus Elastic Wave AVO Anisotropic Synthetic Modeling in Derby Field, Southeastern Niger Delta

AVO based Zoeppritz’s plane wave and elastic spherical wave anisotropic synthetic modelling have been investigated in Derby field, Southeastern Niger delta. The objective of the study is to investigate the influence of anisotropy on plane and elastic wave AVO synthetics modeling over shale-gas sand horizons in the field. Well log data was check shot corrected and correlated with pre-stack data and a zero phase wavelet was extracted after well conditioning and petro physical analysis. Elastic and plane wave algorithms were then used to generate offset-dependent anisotropic synthetic seismograms respectively, using p-wave sonic, s-wave and density logs and Thompsen’s epsilon (e) and delta (σ) anisotropic logs for a transversely isotropic media. Results revealed that seismic anisotropy for AVO based analysis is better modelled with elastic rather than the conventional Zoeppritz’s plane wave model and their approximations for transversely isotropic media at larger offsets. This is attributed to the breakdown of the Zoeppritz’s plane wave model and their linearized approximations at large offsets or near the critical critical angle. Using elastic synthetic model for anisotropic AVO analysis will not only ensure that the reservoir will be adequately imaged, but misinterpretation of data and misplacement of the well will be circumvented.

Anisotropic Avo Analysis for Reservoir Characterization in Derby Field Southeastern Niger Delta

Anisotropic Avo Analysis for Reservoir Characterization in Derby Field Southeastern Niger Delta

Integrating Old and New Data-Evaluation Techniques for Effective Reservoir Characterization of Southeastern Niger Delta Reservoirs

Summary The value of data integration has been proved in assessing the thin-bedded H4 reservoir and the stratigraphically natured H5 reservoir in UKU Field, southeastern Niger Delta, toward planning effective development strategies for depletion. Reservoirs of these definitions pose problems during mapping from seismic for well planning and drilling activities, as well as at the production stage. Data for this work consist of a recently acquired full-stack, 3D ocean-bottom-cable (OBC), prestack-time-migrated (PSTM) seismic data; well logs from five vertical wells; core information; and modular-dynamic-test (MDT) data. Seismic-attribute maps and extracted geobodies revealed the reservoir extent within the limit of seismic resolution (≈27 ft), while petrophysical analysis indicates the reservoirs to be of excellent flow-and-storage quality. MDT data reveal the hydrocarbon fill to be of medium-to-heavy grade. While water production was decided not to be probable for H4 reservoir depletion, it is of certainty in H5 reservoir production. Mapping showed that the field is separated into two fault blocks (FB1 and FB2) on the basis of the difference in water-contact levels, with calculated oil volume of 4 million BO (FB1) and 12 million BO (FB2) in H4 reservoir and 12 million BO (FB1) and 2 million BO (FB2) in H5 reservoir. Gas reserves in H4 sand were calculated to be 480 MMcF in FB2.

Engineering Assessment of South-Eastern Niger Delta Soils Utilized for Highway Pavement

Engineering properties of soils recovered along a road alignment route (right-of-way) and borrow pits of a 30 km road in the South-Eastern Niger Delta area, Nigeria were assessed for utilization as highway pavement earth materials. Laboratory soil tests conducted included the natural moisture content, grain size distribution analysis, consistency limits, standard proctor compaction and California bearing ratio (CBR). About thirty-five (35) soil samples were retrieved from the fifteen (15) boreholes and examined. Results show that all identified and examined soil samples from the borings along the road route and the borrow pits classified as A- 3, A-2-4 and A-2-6 are excellent sub-grade, good fill and sub-base materials. However, none of the soil types meet the engineering requirements for use as base course. Earth materials comprising overburden of clayey sands, silty sands and sandfills (previously used as sub-grades) along the Ahoada-Upatabo-Oyigba-Ebiriba-Ombor 30 km. road in South-eastern Niger Delta were evaluated for highway pavement construction. The results are presented in this paper. The objective of the study was to examine the appropriateness of these soils for the purpose of pavement design and construction as sub-grades, sub-base and base course materials. Previous related studies in the area include works by (1-5).

Comparative analysis of sonic and neutron-density logs for porosity determination in the South-eastern Niger Delta Basin, Nigeria

A comparative analysis of porosity values computed from sonic and neutron-density logs obtained from the same well is here presented. The aim is to identify the more reliable logging tool between sonic and neutron-density in the estimation of porosity values in a formation. Two wells from different parts of Niger Delta were logged for Transit times, bulk density and hydrogen index of the formation as a function of depth. The analysis of sonic, density and neutron porosity values shows a conventional trend of decrease in porosity with depth. Sonic porosity values of well A, and well B varies from 1 to 17%, and 27 to 60% respectively while Neutron-Density Porosity values of well A, and well B varies from 24 to 45%, and 21 to 37% respectively. The Coefficient of Variation for sonic porosity data are 56%, and 23%of well A, and well B respectively , similarly the Coefficient of Variation for Neutron-Density porosity data are 15%, and 14% of well A, and well B respectively. Coefficient of variation of Neutron-density log derived porosities is less than sonic log derived porosities; therefore Neutron-density log derived porosity is more reliable tool for porosity data estimation than sonic log derived porosity. Neutron and density logging tool is here recommended for determination of a reliable porosity value of a formation.

Biomarkers in surface sediments from the Cross River and estuary system, SE Nigeria: Assessment of organic matter sources of natural and anthropogenic origins

Herein, lipid biomarker analysis is applied to surface sediments from the southeastern Niger Delta region for the quantitative determination of aliphatic lipids, steroids and triterpenoids in order to differentiate between natural (autochthonous vs. allochthonous) and anthropogenic organic matter (OM) inputs to this deltaic environment. This ecosystem, composed of the Cross, Great Kwa and Calabar Rivers, is receiving new attention due to increased human and industrial development activities and the potential effects of these activities impacting its environmental health. While the presence of low molecular weight n-alkanes (<C22) and the fossil biomarkers pristane and phytane in all samples, are indicative of a minor petroleum related input, the total extractable organic component of the surface sediments of these rivers remains predominantly of a natural origin as characterized by the variety and predominance of lipid classes that are mainly derived from the epicuticular waxes of vascular plants and include n-alkanes, n-alkanols, n-alkan-2-ones, n-alkanoic acids, steroids and triterpenoids. In addition, recent OM inputs from microorganisms are indicated by the presence of lower molecular weight n-alkanoic acids (Cmax=16), while the major triterpenoids of the sediments, taraxerol and friedelin, and the major sterol, sitosterol, indicate recent OM inputs from vascular plants. Plankton-derived sterols, such as fucosterol and dinosterol, are also found in sediments from the Cross and Great Kwa Rivers and likely originate from autochthonous primary productivity. Furthermore, the coprosterols coprostanol and 24-ethylcoprostanol are present in most samples and indicate measurable anthropogenic contributions from domestic untreated sewage inputs and agricultural run-off, respectively. Of the three rivers studied, the Cross River system was excessively influenced by human and industrial development activities, including drivers such as urbanization and population center growth, land-use change to support agricultural production and animal husbandry, and petroleum exploration and production. These influences were found to be regionally specific as controlled by point sources of pollution based on the relative distributions measured and on the fact that the molecular characteristics of sedimentary OM were not distributed smoothly along a gradient.

Abstract: Slope deformation controls on trap and reservoir development in turbidite systems, southeastern Niger delta, offshore Nigeria

Abstract: Slope deformation controls on trap and reservoir development in turbidite systems, southeastern Niger delta, offshore Nigeria

Abstract: Geochemical Characterization of the Hydrocarbons in the Petroleum System of the Southeastern Niger Delta

Abstract: Geochemical Characterization of the Hydrocarbons in the Petroleum System of the Southeastern Niger Delta

Sequence stratigraphy based on microfacies analysis: Mfamosing Limestone, Calabar Flank, Nigeria

Field observations and petrographic analysis allow a sequence-stratigraphic interpretation of the intensely karstified Albian Mfamosing Limestone Formation in the Calabar Flank of the south-eastern Niger Delta. Main criteria for this interpretation are the presence of siliciclastic intercalations, of prominent hardgrounds, of characteristic microfacies including stromatolites and of phreatic and vadose diagenetic patterns. These criteria enable the recognition, from bottom to top in the type section of the Mfamosing Limestone, of a late phase in the formation of a highstand systems tract and of a flooding surface followed by a lowstand systems tract in which erosional features have been developed locally. The succession is topped by a transgressive systems tract. Some of these units and key sequence-stratigraphic boundaries have been traced into other outcrops in the area. In their identification within the heavily karstified outcrops, petrography overprints and vertical sequence patterns play a significant role. A sedimentation model explains the areal differences in development. Siliciclastic shedding influenced the carbonate system. Time-equivalent carbonate bodies occur on either side of the opening South Atlantic Ocean.

Aspects of the Petroleum Systems in the Southeastern Niger Delta, Nigeria: ABSTRACT

Aspects of the Petroleum Systems in the Southeastern Niger Delta, Nigeria: ABSTRACT

The Afam Clay Member: a Lower Miocene incised channel in the south-eastern Niger Delta

This paper describes a Lower Miocene incised channel system and its lithic fill within the Niger Delta sedimentary succession. Stratigraphic cross-sections, which clearly show the base to be generally asymmetric, and very sharp with erosive characteristics in places, suggest a channel configuration for the base of the Afam Clay. The geometry of the channel and its lithic fill supports this interpretation. The channel was cut by fluvial processes into pre-existing unconsolidated Eocene-Miocene sediments of the Benin and Agbada Formations during a period of low sea level. The Imo River proto-channel is thought to have aided the channelling. The channel was subsequently enlarged by marine processes associated with a Middle Miocene rise in sea level. The lithic fill of the Afam channel is dominated by clay beds with localized development of sand bodies in time and space. Analysis of the spatial distribution of the sand units and their SP shapes supports the hypothesis of sand input from the north, east-central and west-central flanks of the channel. These are interpreted to reflect sand contributions from tributaries that fed the main channel. The faunal, lithological and textural characteristics of the Afam sediments suggest a predominance of marine conditions in the south, paralic conditions in the central area and fluvial processes in the north. In addition, the southern flanks of the channel may constitute truncation stratigraphic traps for hydrocarbons and it is proposed that these flanks should be fully explored.