http://hdl.handle.net/123456789/113 Tue, 07 Apr 2026 20:05:14 GMT 2026-04-07T20:05:14Z http://hdl.handle.net/123456789/2141 ATTRIBUTE-DRIVEN FLUID REPLACEMENT MODELING AND RESERVOIR CHARACTERISATION OF TETEMU FIELD, ONSHORE NIGER DELTA, NIGERIA SALAMI, Rotimi Change in saturation levels occurs in reservoirs during hydrocarbon production resulting in fluid replacement. This impacts on the mechanical and elastic properties of reservoirs and consequently, alters production model and forecast. Increasing occurrence of altered production model has necessitated the need to understand how these properties can trigger fluid replacement in hydrocarbon reservoirs. Mechanical and elastic properties can be harnessed to constrain Fluid Replacement Modeling (FRM) in two scenarios: increasing water and gas saturations (Sg) at various reservoir conditions. This research was designed to produce geological model to predict the responses of rock properties to fluid replacement and reservoir behaviour. The FRM and reservoir characterisation were carried out using petrophysical and rock-physics analyses of wells A1, A2 and A3 of Tetemu Field, onshore Niger Delta. Petrophysics was employed to determine lithology, Net-Gross Ratio (NGR), shale volume (Vshale), porosity (ɸe) and saturations which were estimated by Gamma Ray (GR), neutron-density and resistivity logs. Depositional environments were deduced by GR signatures. Rock-physics was used to determine reservoir’s stress state, elastic and mechanical properties’ responses to increasing saturation. Young (E), Bulk (K) and Shear (G) moduli, Unconfined Compressive Strength (UCS), Compressibility (Cb) and Poisson ratio (ʋ) were derived from elastic properties such as Compressional wave velocity (Vp). Sand production potentials were estimated using G/Cb. Four hydrocarbon reservoirs (A, B, C and D) were delineated. The NGR reduces from proximal to distal due to reduction in depositional energy. The reservoirs were relatively clean with Vshale less than 15.0% threshold. The Vshale increased in the direction of lower hydrodynamic flow. Reservoirs were deposited in fluvial channel, progradational and deltaic sands. Dynamic Rock Physics Template (RPT) showed pore pressure depletion in reservoirs A and D of A1 as well as A, B and D of A2. The density increase was attributed to increasing G and K when brine replaced hydrocarbon. Unconventional attenuation of Vp from 3.09-3.04, 3.13-3.08, 3.92-3.86, 3.53-3.49 and 3.87-3.80 km/s in A of A1 and A3, and D of A1, A2 and A3, respectively, were due to dissolved gases. The values of E and K increased exponentially from 21.45-21.67 GPa and 16.93-18.28 GPa in A of A2. The value of ʋ was higher in oil and brine but negligible in gas-sand. The G/Cb for all reservoirs were greater than 0.8×1012 psi2 threshold. Increasing Sg resulted in reduction in E and UCS. The observed pore pressure depletion from RPT could cause well instability due to induced matrix stress. Anomalous behaviours of elastic parameters were attributed to dissolved gases, while a decrease in UCS and E in A and D of A1 and A3 will cause wellbore collapse. None of the reservoirs produced sand during hydrocarbon production. Enhanced recovery modeling generated decreased K and E which reduced the stiffness and brittleness of the reservoirs. Unconventional attenuation of compressional wave velocity and the responses of bulk modulus in gas provided a pathway for prediction of reservoirs’ responses to changing fluid saturations during hydrocarbon production. These models could be employed as templates for monitoring hydrocarbon reservoir performance. Tue, 01 Aug 2023 00:00:00 GMT http://hdl.handle.net/123456789/2141 2023-08-01T00:00:00Z http://hdl.handle.net/123456789/2139 HIGH RESOLUTION CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY OF THREE WELLS 1, 2 AND 3 IN NORTHWEST OFFSHORE NIGER DELTA, NIGERIA COLE, JANET ADERONKE Over the years, various biostratigraphic approaches (foraminifera, pollen and spores) have been used for determining age and biozonation which are useful for exploration and production activities in the Niger Delta. However actual age determination and refined zonation of the deep offshore Niger Delta area have not been achieved. Hence the need to determine the litho-stratigraphic sequence, age of the strata and a sequence stratigraphic frame work for the Paleogene – Neogene section of the Niger Delta. This study was therefore designed to establish absolute age using calcareous nannofossils for the sediments penetrated by three Wells 1, 2 and 3 in Northwest offshore Niger Delta. Five hundred and ninety nine ditch cuttings (599) from three wells (1, 2, 3) offshore Niger Delta were lithologically examined and lithofacies delineated. Slides from the ditch cuttings were prepared using standard procedures and studied using light microscopy. The abundance and diversity of the markers of the calcareous nannofossils were identified using standard procedures and were used for precise zonal delineation and recognition of dated events. Greyish to brownish shale, silt and mudstone intercalated with coarse to medium and fine-grained sand beds were identified. Forty-one calcareous nannofossil species identified confirmed Early Paleocene to Early Pliocene age (NP3-NN15 zones) for the three wells. Well 1 penetrated Middle Miocene to Early Pliocene (NN7-NN15 zones); Well 2 was restricted to Early to Late Miocene age (NN3-NN11), while Well 3 encountered the Early Paleocene (NP3-NN4 zones). Established on the first and last appearances of the marker species as well as their relative abundances three major zones (NN7-NN8, NN9-NN10, NN10 and Younger) four major zones (NN3-NN4, NN7, NN8-NN10, NN11) and three major zones (NP3-NP6, NP14-NP21, NN4) were identified for well 1, 2 and 3 respectively. The acme events of Discoaster prepentaradiatus, Catinaster coalithus, Discoaster kugleri, Helicosphaera ampliaperta, Helicosphaera scissura, Pemma basquensis and Chiasmolithus daniscus were associated with the 8.80, 9.50, 12.18, 14.20, 15.60, 32.47 and 64.75 Ma maximum flooding surfaces, respectively. The correlation of the three wells showed basin-ward younging direction and two zones recognized in wells 1 and 2 (NN7 and NN8) belonging to the Late Miocene age was confirmed. The established zonation scheme for Wells 1, 2 and 3 subdivided the offshore Niger Delta Paleocene to Pliocene sequence into zones, subzones and lithostratigraphic sequences and hence the absolute age determined Sat, 01 Apr 2023 00:00:00 GMT http://hdl.handle.net/123456789/2139 2023-04-01T00:00:00Z http://hdl.handle.net/123456789/1796 AGRO-GEOPHYSICAL ASSESSMENTS OF SPATIAL VARIABILITY IN AGRICULTURAL SOIL PROPERTIES IN IBADAN, SOUTHWESTERN NIGERIA OLAOJO, ABAYOMI ADESOLA Agricultural soil nutrients variability assessment for sustainable crop production has usually been through soil geochemical/chemical analyses which are laborious and expensive, thus necessitating the need for faster and cheaper alternatives. The application of geophysical methods to resolve this has gained acceptability globally. However, there is paucity of data from Nigeria on the application of geophysical investigation for soil properties variability determination. Therefore, this investigation was designed to use geophysical methods to assess the physical properties that can substitute for geochemical analysis of agricultural soil nutrients in Ibadan, southwestern Nigeria. The investigation was at the research farms of the Cocoa Research Institute of Nigeria, Ibadan. The Apparent Electrical Conductivity (ECa) and Volumetric Water Content (VWC) of the soils were determined using resistivity earth-meter and VG-meter-200 moisture-meter. The 912 (cocoa farm) and 700 (kola field) points were classified into zones of Low ECa (LECa), Moderate ECa (MECa) and High ECa, (HECa) on which other investigations were based. Thermal Conductivity (TC), Volumetric Heat Capacity (VHC) and Thermal Diffusivity (TD) at 90 (Cocoa farm) and 67 (Kola field) points were determined by KD2PRO analyser. The ECa, VWC, TC, VHC and TD were assessed in both wet and dry seasons. Falling and constant head permeability tests were conducted on duplicated ten cored soil samples per farmland for water infiltration assessment. Soil textural classes were established in the cocoa (54-sample) and kola (42-sample) farms using Bouyoucos method. Soil (20-sample/farmland) were analysed for pH, Electrical Conductivity (EC), organic carbon, total nitrogen, available phosphorus, acidity, Na, Mg, K, Ca and Cation Exchangeable Capacity (CEC) using standard soil science procedures. Soil mineralogy (6-sample/farmland) was determined using X-ray diffractometer. All investigations were limited to the root zone (0.3 m). The soils EC a, VWC, TC, VHC and TD were 10-545 µS/cm; 2-69%; 0.700-2.715 W/mk; 0.760-4.578 mJ/m3k and 0.351-1.994 mm2/s, respectively. The soils were categorised into LECa (1-49 µS/cm), MECa (50-99 µS/cm), and HECa (>100 µS/cm). The HECa had high TC (1.668-2.148 W/mk), high VHC (2.604-2.721mJ/m3k), and low TD (0.622-0.835vii mm2/s), while LECa had inverse distribution, indicating that heat energy retained in soils aided mobility of ions. Soils’ permeability ranged from 6.2x10-6-3.97x10-3 cm/sec across the field. Infiltration rate was low (HECa), moderate (MECa) and rapid (LECa) accounting for the moisture variation. Texturally, the soils were sandy loam (HECa/MECa/LECa), loamy sand (MECa/LECa) and sandy clayey loam (HECa). The soils’ pH, EC, organic carbon, total nitrogen, available phosphorus, acidity, Na, Mg, K, Ca, CEC ranged from 6.1-7.6; 30-180 µS/cm; 0.270-1.667%; 0.03-0.17%; 3.50-12.71 mg/kg; 0.32-1.20 cmol/kg; 0.15-0.42 cmol/kg; 0.25-2.84 cmol/kg; 0.13-1.33 cmol/kg; 0.46-5.84 cmol/kg and 1.92- 10.33 cmol/kg, respectively. The saturation of basic cations in HECa (81.38-87.73%), MECa (73.24-81.82%) and LECa (71.80-77.87%) indicate that HECa had more nutrients than others. Kaolinite (4.7-41.2%), microcline (6.8-24.6%) and quartz (14.3-67.2%) were the main minerals in the soils. The HECa had low quartz (22.5-41.3%) and microcline (9.85-15.05%), but high kaolinite (31.1-37.6%). Soil physical properties from geophysical methods were effective in evaluating the spatial agricultural soil nutrient variability. This method can therefore be adopted for cost effective agro-soil evaluation. Wed, 01 Sep 2021 00:00:00 GMT http://hdl.handle.net/123456789/1796 2021-09-01T00:00:00Z http://hdl.handle.net/123456789/1619 OPTIMISING SLOPE STABILITY BY OPEN PIT SLOPE DESIGN AT IKPOBIA MARBLE QUARRY, OKPELLA, SOUTHWESTERN NIGERIA OUADADI, SENOUCI The adoption of Open Pit Slope Design (OPSD) used in exploitation of minerals is known to impact mining outputs and safety if slope stability is properly determined. However, slope stability is dependent on the understanding of the rock mass properties and identification of critical features such as overburden materials, structural features, and groundwater system of the mines, all of which are usually not well defined. Therefore, this study was aimed at determining the rock mass properties and associated critical features of Ikpobia Marble Quarry, Okpella, Southwestern Nigeria towards optimising slope stability. The quarry was divided into seven zones (1-7), each with approximately constant bench orientation. Geologic mapping of the quarry was conducted. Vertical Electrical Sounding (VES) using the Schlumberger array was done to determine the subsurface lithology. Quarry photographs were taken and used in photogrammetric analysis to create models of each of the seven zones. Rock mass classification (Geologic Strength Index, GSI) was carried out on the models. Core rock samples from the quarry were tested to determine Uniaxial Compressive Strength (UCS), indirect tensile strength, and density. Petrographic study and X-Ray Diffractometry (XRD) of the rocks were also undertaken. Joint sets orientations were determined from the photogrammetric models and used for kinematic analysis. Data from the analyses were used to determine rock mass properties and as input for analysis of slope stability. The heights (m) and angles (°) of slopes of the seven zones analysed were 25 and 85; 25 and 80; 20 and 80; 20 and 75; 30 and 80; 20 and 80; and 25 and 85, respectively. Rocks in the quarry were marble interbedded with calc-silicate gneiss, banded gneiss and quartz schist. The VES showed H-type curves to be dominant (62%) indicating three geoelectric layers made up of clayey sand topsoil, weathered bedrock, fractured and fresh bedrock. Joint sets observed in the zones ranged from 4 – 8 with the dominant orientation posing stability risk to the Northwest. The GSI ranged from 30 to 40. The UCS ranged from 45.7 to 52.3 MPa, tensile strength ranged from 1.5 to 4.6 MPa, and density ranged from 2710 to 2745 Kg/m3 which are in the low to medium range for intact rock. Minerals identified in the rocks were Calcite, Quartz, Alkali Feldspar, Chlorite, Apatite, Biotite, Muscovite, Epidote, Diopside, Phlogopite, Microcline and Albite. Kinematic analysis indicated low risk of slope failure across the zones but a toppling failure with 60% probability in zone 1. The current safety factors for each zone were 1.5, 1.43, 1.34, 1.69, 1.35, 1.34, and 1.5, respectively for zones 1 to 7. The optimum slope angles determined from finite element sensitivity analysis are 55°, 40°, 20°, 40°, 45°, 20° and 55° for zones 1 to 7, respectively. The optimum slope angles for optimising slope stability were determined. The quarry rock mass properties, critical features assessment and measurements met the requisites standards for acceptable limits of safety. Wed, 01 Sep 2021 00:00:00 GMT http://hdl.handle.net/123456789/1619 2021-09-01T00:00:00Z