IOSR-JAGG   Volume-2 ~ Issue-2 ~ MAR-APR-2014

Abstract:The southern part of Kadiri Schist Belt is in juxtaposition with granitoids on either side which include TTG, TGM, and MS suites. The schist belt rocks and granitoids exhibit three phases of deformation. The granitoids are mainly medium to coarse grained and exhibit hypidiomorphic texture. Geochemical signatures suggest that the granitoids are magmatic, metaluminous, calc-alkaline and grouped under mixed origin. The field, mineralogical and chemical observations discriminate them as I-type. Petrogenetic studies indicate that polyphase polymigmatised TTG gneisses show the existence of older simatic crust which later gave rise to varied sialic crust in marginal basin environment. The calc-alkaline TGM suite points to magma mingling and mixing and fractional crystallization differentiation. The MS suite has evolved due to crustal anatexis and mantle derived melts.

Keywords : Granitoids, Kadiri Schist Belt, Magma mingling and mixing, Petrology.

Abstract:The performance of drilling bits has a direct influence on cost and increase in the rate of penetration translates significantly to cost and time saving. From a total sample of 56 wells, approximately 450 tri-cone bits were consumed at a cost of KSh 200Millions.

Abstract: Geochemical analyses of domestic groundwater sources within Okeagbe-Akoko, South-western Nigeria have been conducted. A total of twenty (20) water samples, sourced from hand-dug wells, deep wells and streams, were analyzed for their physico-chemical characteristics, with the aim of determining their suitability for local domestic consumption. The physico-chemical analyses involved the determination of Electrical Conductivity (EC), Acidity (pH), Total Dissolved Solids (TDS) and the determination of the concentration of a heavy metals suite consisting of Zinc (Zn), Nickel (Ni), Cadmium (Cd), Copper (Cu), Lead (Pb), and Chromium (Cr), using the Atomic Absorption Spectrometry (AAS). Result ranges obtained for the physical parameters were pH: 5.82 to 7.08, total dissolved solids: 43 to 492 mg/l, and electrical conductivity: 71.681 to 820.164 μs/cm. The heavy metal concentrations for Cu and Zn ranged from 0.001 to 0.014 mg/l and 0.001 to 0.030 mg/l respectively. Ni, Cd, Pb and Cr were not detected in any of the water samples. All determined physico-chemical parameters were well below the current World Health Organization (WHO) acceptable limits for safe water sources. This indicates that the domestic water sources in the area are relatively contaminant free and safe for domestic use. The Cu2+ concentration distribution pattern however, provides insight into the likely nature of heavy metal contaminant migration path in the event of an impact.
Keywords: Domestic water sources, physico-chemical properties, water quality, Atomic Absorption Spectrometry (AAS), heavy metal concentration.

Abstract: Magnetic data were compiled from four aeromagnetic maps. A submap for the study area was produced from the four magnetic sheets in an ILWIS environment. Magnetic intensity values vary between 32,600 and 33,160 nT. The lowest magnetic contour values closure is centred over the Kagoro granite rocks at the central part. This closure is structurally aligned along the NE – SW direction. Regional field values vary between7789.1 and 7896.6 mGal. The residual contour values range from -180 to +160 nT. The main closure of the residual map is located on the central part of the area. A slipper-shaded closure centred over the Kagoro Granite is oriented along the NNE – SSW direction. Some of the closures in the study area are aligned along the NE – SW and E – W directions. Patterns of the closures of the magnetic maps are in conformity with those of the Nigeria basement and younger granite rocks. Isolations and magnitudes of the closures suggest that the various rock bodies occur separately and at different levels. The regional fields along nine profiles were obtained by third degree polynomial fitting using OriginLab7 software so as to obtain the residuals used for the models. The residual anomalies were accounted for by Mag2dc (2.5D) algorithms. The four profiles that traversed the Kagoro younger granite complex were estimated at maximum thicknesses of 14.1, 15.2, 9.5 and 10.4 km. These suggest that the Kagoro younger granite complex was emplaced at depths between 9.5 and 15.2 km. The volcanic rocks and their associates were formed from depths between 4.7 and 13.0 km.
Keywords: Closure, emplacement, granite, Kagoro, magnetic, structure.

Abstract: Twenty five resistivity data points were sounded in the study area with an ABEM Terrameter. Maximum electric current half spacing attained for each point was 100 m. The raw data were interpreted with IX1D software. The X, Y, Z data file was imported into Surfer9 software for resistivity mapping and contouring using kriging interpolation algorithm. Isopach closures of the surface layer trend along NNE – SSW and NE – SW directions. The iso-ohmic map of the layer depicts compositions of sands, sands/gravels, and gravels. Thickness of the second layer ranges from 1 - 21 m and its resistivity values suggest sediments of argillaceous and arenaceous composition. The third layer isopach map indicates that sediments of intermediate values are sandwiched and partly sandwiched by thinner ones. Iso-ohmic map of the layer has clay lenses within sandy constituents. Isopach map of the fourth layer shows majority of the thinner sediments occurring along the west to the south directions. Thicker sediments are located at the northeast.
Keywords: Aquifer, borehole, isopach map, iso-ohmic map, lithology.

Abstract: Spectral depth analysis of aeromagnetic data covering latitude 12.00'N to 13.00'N and longitude 10.00'E to 11.00'E which corresponds to part of Borno basin, Northeastern Nigeria, was carried out for the purpose of investigating the sedimentary thickness beneath the surface. The study area was covered by 4 aeromagnetic maps. The aeromagnetic maps were digitized on a 3km grid and later complied to produce a combined aeromagnetic data file for the area. The data file comprises 1369 data points. Polynomial fittings method was applied in the regional residual separation. The residual map was later sub-divided into 16 spectral sectors. The result of the study shows that the first layer depth was estimated to have a range from 0.18km to about 1.9km while the second layer depth was estimated to have ranged from 2.9km to about 4.2km. The highest sedimentary thickness of 4.2km occurred at the extreme northeast part of the study area and corresponds to areas around Gorgoram. These areas may be subjected for further geophysical method like seismic reflection/refraction, so as to ascertain its hydrocarbon potential.
Keywords: Aeromagnetic data, spectral, depth, sedimentary depth, first and second layer depth.

Abstract: The groundwater of the Middle aquifer was collected to examine its characteristics. The chemistry of the water showed that it has SAR value of about 4.6 and EC is 667 Scm-1. This makes the water suitable as fresh water and can be used for irrigation. The results were presented in Richards and Piper's diagrams for easy visualization. The water samples plots in good and permissible water class with salinity hazards of medium – high salinity groups. While the water samples plots in the same region in the piper's diagram indicating that they are hydrogeologically connected and continuous. The chemical data recognized a water type classified as sodium bicarbonate type (Na + HCO3) facies where sodium is significant in its concentration; with cation and ions in the order of Na > Ca > K > Mg and HCO3 > CO3 > Cl > SO4 for drinking water quality.
Keywords: Groundwater, Salinity hazard, Hydrogeologically, Sodium bicarbonate, Facies.

Abstract: The Middle zone aquifer is the most extensive and most widely exploited of the three well known aquifers of the Chad Formation. This aquifer is confined by variable thickness of argillaceous deposits of 100 – 150 m thick. This led to the variable heads in boreholes drilled to this zone. Boreholes drilled from 1960 to 2010 shows a drastic decline in piezometric heads. The piezometric heads of over 20 m above ground level ( agl) observed in 1960 to 1.2 m agl in 2010 have declined over the last half century. In the present work the heads at 0.2 m/ year giving the present piezometric head at an average of 0.5 m agl. The lower heads in old boreholes are attributed due to siltation, encrustation and ageing of borehole. Furthermore, lack of present day recharge and poor borehole construction methods play a vital role in determining the piezometric head.
Keywords: Aquifer, Declined, Piezometric head, Borehole, Encrustation.

Abstract: Sonic, gamma ray, density and resistivity logs in the onshore Coastal Swamps of the Niger Delta are used in the determination of some petrophysical properties of the reservoir in the Coastal Swamp Depobelt in the Niger Delta. The parameters investigated were porosity, velocities, shear and compressional velocities, and Poisson's ratio. The results of the analysis show that the reservoir is 66m sandstone thick having porosity range of 0.21 – 0.39 with average of 0.26; density ranges between 2.01 and 2.30 with average of 2.21g/cc; Poisson's ratio range 0.33 – 0.45 with 0.40 as average value; shear-wave velocity Vs ranges from 718 to 1097 having average of 932.33 m/s, compressional-wave velocity Vp ranges from 2110 to 2570 with average of 2230m/s, Vp/Vs ratio ranges 1.96 – 3.18 with average value of 2.55; and Gamma-ray GR value ranges 62 – 105 having average of 90AP and Vs 718 m/s are indicative fluid-filled reservoir. The results of this work can be used for well drilling and petroleum production programmes, and for civil engineering work in the area of study.
Keywords: Petrophysical properties, reservoir characterization, lithofacies, porosity, Poisson's ratio, compressional and shear velocities, Niger Delta.

Abstract:Petrophysical imaging of two reservoirs of Amangi hydrocarbon field of the Niger Delta of Nigeria was conducted based on crossplot analysis using AVO information from well log data of five appraisal wells in the field. The field consists of series of reservoirs stacked in channelized shoreface sands encased in shales. Two reservoirs H1000 and H4000 which constituted the first phase of development of this field formed the pivot of this study. Firstly, we extractedpetrophysical parameters such as P and S impedances, Lamé's parameters, etc. Secondly, appropriate pairs of rock attributes and properties were crossplotted so that common lithologies and fluid types cluster together for quick identification and interpretation.

Abstract: In this paper we performed seismic-to-well tie and wavelet extraction that would subsequently be used for inversion. We took cognizance of the key factors that make for accurate well-to-seismic tie and ensured that the borehole seismic and the surface seismic at the borehole trajectory look as similar as possible. This was possible through quality control of the well log and seismic data, timing and log calibration, well tie location, seismic bandwidth and signal-to-noise ratio and the use of well tie diagnostics that underlie a successful close well tie. The data were processed to zero phase and the dominant loop in the resulting seismic wavelet was delayed and corresponds to an increase in P-impedance.

Abstract: We present a fluid substitution case study of Amangi hydrocarbon field applying Biot-Gassmann theory in which the changes in acoustic parameters (P- and S-wave velocities and density) were modelled. Shear wave velocity was predicted using Greenberg and Castagna empirical relationships between P-wave and S-wave velocities. The results of fluid substitution compare favorably to the available sidewall data. The amplitude character of seismic reflections varied with offset, due to changes in the angle of incidence. The wells on the field penetrated several stacked channelized shoreface sands of variable qualities at depths of 2,702 m and 2,919 m and with thicknesses of 89.05 m and 25.67 m respectively.