Kerogens were purified from 26 samples of the Kimmeridge Clay Formation over the full range of maturities pertinent to petroleum generation. Most samples comprised >90% amorphous organic matter (AOM). Prior to and during the early phase of petroleum generation, kerogen densities range between 1.18 and 1.25 g cm-3. During peak and late stage petroleum generation, densities increase to ∼1.35 g cm-3 as hydrogen indices decrease from ∼350 to 50 mg HC/g C. The data are qualitatively consistent with the loss of alkyl carbon from kerogen to petroleum and the increased aromatization of remaining carbon. The density increase observed for AOM contrasts with the data for vitrinite, which exhibits a decrease in density at maturity levels relevant to petroleum generation. The contrasting behavior of AOM and vitrinite is thought to reflect the differing structural composition of the two kerogen types, most obviously the greater initial aromaticity of vitrinite.

To achieve a better understanding of the nature of the factors influencing groundwater composition as well as to specify them quantitatively, conventional graphical and multivariate statistical analysis (principal component analysis) were applied on hydrochemical data consisting of 51 groundwater samples collected from domestic boreholes in Yenagoa city, Bayelsa State, Nigeria. The mode of study includes analysis of major ion contents and other chemical parameters such as pH, total dissolved solids and electrical conductivity of the groundwater samples. The PCA yielded three principal components explaining 78.38 % of the total variance of the 11 parameters. The three components are interpreted as controlled by the natural weathering of existing silicate rocks, reverse ion-exchange processes and oxidation reactions which are further supported by the scatter diagrams, ionic signatures and mechanisms controlling the water chemistry diagrams as the common factors influencing the groundwater hydrogeochemical character. Limited anthropogenic influence on the groundwater composition has also been noticed in the study area. The groundwater poses no threat to human health because the concentrations of physico-chemical parameters that can be used to evaluate drinking water quality are within World Health Organisation standard specification. The groundwater in the area is fresh, high salinity and low sodium in nature.

Nineteen Schlumberger vertical electrical soundings (VES) were carried out within and around Yenagoa city, South South Nigeria, using a maximum current electrode separation ranging between 300 - 400 m. The objectives of the study were 1) to evaluate the possibility of mapping Quaternary sediments to infer the geological structure from the electrical interpretation and identify formations that may hold fresh water with low concentration of conducting minerals such as iron 2) to evaluate the vulnerability of the aquifer in the study area. The interpretation of the data collected was by computer assisted iterative interpretation using 1-D inversion technique software (1X1D, Interpex, USA). The results of the interpretation revealed four distinct geoelectric layers. Sounding curve types obtained in the area are mostly of the form <i>ρ</i>₁ > <i>ρ</i>₂ < <i>ρ</i>₃ < <i>ρ</i>₄ (where <i>ρ</i> is the density) but fresh water lenses with low concentration of conducting minerals such as iron were obtained only in locations that exhibit <i>ρ</i>₁ > <i>ρ</i>₂ < <i>ρ</i>₃ < <i>ρ</i>₄ curve types. Depth to the aquifer ranges from 4.5 m in the vicinity of VES 05 to 27.0 m at the vicinity of VES 14. The resistivity of the aquiferous horizon varies between 60 - 2868 Ωm. High transverse resistance values obtained were associated with zones of high transmissivity which agrees with the geology of the Benin Formation (Coastal Plain sands) consisting of fine-medium-coarse sands. The aquifer vulnerability map illustrates the impermeability of the overburden clay layer. Values of >0.5 mhos indicate good protective capacity, while values <0.3 mhos indicate vulnerable zones with probable risk of contamination

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In order to quantify the P-and S-wave velocities, dynamic elastic moduli and bearing capacity of shallow alluvial sediments, seismic refraction and cone penetration test (CPTu) soundings were carried out in two sites in Yenagoa. The seismic refraction data was analysed using the intercept-time technique to obtain the seismic velocities which were subsequently used to estimate the dynamic elastic moduli. The relevant CPTu data were emplaced into an established empirical equation to determine the shear wave velocity (V s ), with which the compressional wave velocity (V p ) was estimated. Combing the compressional and shear wave velocities, the dynamic elastic moduli of the shallow sediments were determined within the depth range of 0.5-8.0 m. On comparison, it was observed that the average values of V p and V s from the two methods are fairly in agreement. Significant difference in the average values was only observed in the dynamic elastic moduli. Correlation of the V s -wave and the dynamic moduli from the CPTu data show linear relationship between S-wave velocity and the dynamic elastic moduli with correlation coefficients (R 2 ) greater than 0.9 in all cases. These elastic moduli values can be used for the design of foundation of structures, site response and settlement analysis.

The corrosivity of the top three metres of the soil along a pipeline route was determined using soil electrical resistivity for the emplacement of a conduit intended to serve as a gas pipeline. Fifty-six Schlumberger vertical electrical soundings (VES) were carried using a maximum current electrode separation ranging between 24 - 100 m at 2.0 km interval. The data was interpreted using a 1D inversion technique software (1X1D, Interpex, USA). Model resistivity values were classified in terms of the degree of corrosivity. Generally, the sub-soil condition along the pipeline route is non-aggressive but being slightly or moderately aggressive in certain areas due to local conditions prevailing at the measuring stations. Based on the corrosivity along the pipeline route, appropriate cathodic protection methods are prescribed.

Hydrogeochemical studies were carried out in Yenagoa city and environs, Southern Nigeria in order to assess the chemistry of the groundwater and identify the dominant hydrogeochemical processes and mechanisms responsible for the evolution of the chemical composition of the groundwater. The study approach includes detailed geochemical analysis of groundwater samples collected from domestic boreholes for major constituents such as Ca 2+ , Mg 2+ , Na + , K + , HCO 3 , Cl-, SO 4 2-, and NO 3 and the hydrochemical data was subjected to multivariate statistical analysis and conventional graphical plots. The results show that most groundwater quality parameters are within World Health Organization acceptable limits for drinking water. The chemical relationships of the ions in Piper diagram identify Ca-Cl, Ca-HCO and Na-HCO 3 as most prevalent water types. The alkalis exceed the alkaline earths and weak acids exceed the strong acids. The contribution of (Ca + Mg) and (Na + K) to total cations and HCO 3 indicates the dominance of silicate weathering as the major source of cations. The plot of Na vs Cl indicates higher Na, derived from silicate weathering process which was also supported by higher HCO 3 values. Reverse ion exchange process is also significant in the study area which is indicated by negative Schoeller indices and shifting to the left in the plot of Ca 2+ + Mg 2+ vs HCO 3 + SO 4. Furthermore, the plot of Na-Cl vs Ca+Mg-HCO 3-SO 4 confirms that Ca, Mg, and Na concentrations in groundwater are derived from aquifer materials. Saturation index of silicate and carbonate minerals indicate undersaturation to oversaturation

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