Earth Science

Sequence stratigraphic analysis carried out on the XP field, Greater Ughelli Depobelt, Niger Delta, revealed three sedimentary sequences within the intervals penetrated by three wells studied in the field. Well logs and biostratigraphic data integrated helped in the identification of three major Maximum Flooding Surfaces (MFS1, MFS2, MFS3) recognized between the intervals of 3840- 3080m (aged 31.3- 26.2Ma) and three sequence boundaries designated SB1, SB2 and SB3, between 4232m and 3140m (aged 32.4 – 27.3Ma). The Maximum Flooding Surfaces were recognized using intervals containing high abundance and diversities of three index fossils (Uvigerinella 8, Bolivina 27 and Alabamina 1) which represent the three regional marker shales identified in the field. The erosional surface coincides with intervals that are barren in faunal activity and also corresponds with the coastal deltaic paleobathymetric depth interpreted as Sequence Boundaries. The sequences depict sediments that were deposited between Early to Late Oligocene period in water depth ranging from coastal deltaic to neritic environments. Three depositional patterns resulting from regression and transgression recognized include progradation, retrogradation and aggradational packages with associated systems tracts. The systems tracts form good reservoirs with prospects in the field.

Disease causing pathogens have a strong relationship with the environment wherein the animal as well as the microorganisms lives. The present study was conducted to evaluate the relationship between the meteorological data and the disease prevalence in cattle in Tamilnadu. The data revealed a closer relationship between the climatic factors (temperature, rainfall and relative humidity) and infectious diseases (Anthrax, Black Quarter, Hemorrhagic Septicemia and Foot and Mouth Disease). Hence, the incidence of infectious diseases were found to be significantly (P<0.05) associated with the season and microclimatic factors.

Deck- drain samples obtained from five oil wells in the Niger Delta Basin of Nigeria were analyzed using Atomic Absorption Spectrophotometer (AAS), digital meters , American Standard and Testing Materials. The results shows that the pH of the deck-drain samples varies from 5, 10 to 5.4 while the total dissolved solids(TDS) varies from 4,585 to 27,170 mg/l. The electrical conductivity varies from 7,054 to 21,277µS/cm while the chloride content varies from 4 ,000 to 4,400mg/l. The H2S concentration ranges from 1.10 mg/l. These values do not conform with the Nigerian Department of Petroleum Resources (DPR) effluent water standard and thus constitute a threat to the environment. The result also show that the deck-drain samples are hard and contains high concentrations of calcium and sodium. The concentrations of the major cations in decreasing order is: Na+ > Ca2+ > Mg2+ >. K+ while that of the anions is: Cl- > HCO3- > SO42- > NO3- implying that the fluid type is NaCl. The pollution index (PI) of the samples varies from 17.81 to 42.47; this is in excess of the PI critical value of 1 and thus confirms high rate of degradation of the deck-drain samples.. The Sodium Adsorption Ratio (SAR) values of the samples ranges from 28.04 to 28.97 indicating that the deck-drains are poor for irrigation purposes. Piper and Stiff diagrams shows that the deck-drain samples exhibits the same chemical trend and model. Although, the deck-drain samples contains high concentrations of pH, TDS, electrical conductivity, H2S, Cl-, Ca2+ and Na+ ; these parameters can be treated and reduced to tolerable levels using soda ash, reverse osmosis , electro dialysis and aeration methods thus preventing soil and water pollution which can arise from the discharge of untreated deck-drains into these environments.

The facies architecture and depositional environments of the ‘X’ Field reservoirs have been studied in Wells NDI-A10, A12, A11, A7, A2P2 and A2, using wireline log data. The logs were examined and analyzed for reservoir identification, thickness distribution, continuity, and connectivity. The depositional environments were determined by closely comparing the log shapes of interest with the standard log motifs of Schlumberger (1985) and Emery (1999). Three deltaic sub-environments of deposition were recognized: beach-barrier, river mouth bar and shoreface. The sequence stratigraphic concept has been applied to these sub-environments. Six reservoirs: I, J, K, L, M and N, and five stratigraphic sequences: SEQ.I, SEQ.II, SEQ.III, SEQ.IV and SEQ.V, were identified. The reservoirs were deposited as progradational parasequences during a high-frequency highstand systems tract, while the shale units underlying and overlying the reservoirs were deposited as retrogradational parasequences. The consistent alternation of progradational sand units and retrogradational shale units have been interpreted as a tripartite union of source rock, reservoir and seal, essential for hydrocarbon generation, accumulation, and trapping in the ‘X’ Field. Well-to-well correlation across the entire field allowed a reconstruction of the depositional history of the reservoirs and delineation of the reservoir geometry. There was more development of the reservoirs in the northeastern part of the field which has been interpreted as the direction of sediment supply, but the overall depositional trend is similar to that of the present-day Niger Delta.

The results of the first for Bulgaria ecomonitoring researches, carried out during three seasons (spring, summer and autumn) of 2011 in 4 biotopes of the Vit River valley in the direction middle – lower course trough tests performed to find chemical pollution, are presented; analysis of the biological diversity of bioindicative groups of organisms (bioindicative macroinvertebrate fauna), occupying different trophical levels in the researched freshwater ecosystems. The physicochemical monitoring was made on the basis of indicators of: acidity, insoluble substances, conductivity, biological oxygen demand (BOD5), chemical oxygen demand (COD), nitrate ions, sulphate ions, copper, lead, etc.

A geo-electric survey involving vertical electric sounding (VES) was carried out at the Nigeria Mining Corporation‘s quarry at Omi-adio near Ibadan Southwestern Nigeria, with a view to determinning the thickness and spatial variation of the clay deposit in the study area. Twenty VES were carried out in four traverses using a Geopulse Tigre terrameter within the vicinity of the study area with each traverse having four to six VES points. Quantitative interpretation of the data involved partial curve matching and computer assisted iteration method. A 3D contour map showing the variation of clay resistivity and thickness was also plotted. The results show that the deposit is made up of four lithological layers namely top soil, sandy clay, clay and weathered/fresh basement. The resistivity curves fall into five categories HA type (i.e. > < < ) KH type (i.e. < > < ), QH type (i.e. > > < ), A type (i.e. < < ), H type (i.e. > < ) with KH type dominant. Also the Geoelectric section shows that the top soil has resistivity between 11.5 and 155.6 and thickness between 0.7m and 3.8m. The sandy clay layer has thickness between 0.2m and 4.0m and resistivity between 71.5 and 278.8 . The clay layer has resistivity between 7.7 and 33.5 and thickness between 4.8 and 31.0 while the fresh/weathered basement has resistivity between 46.3 and 871.7 .The depth to bedrock is between 6.2m and 32.9m.The coefficients of anisotropy fall between 1.01 and 1.76 suggesting the presence of good quality clay.

Lithostratigraphic, foraminiferal and calcareous nannofossil biostratigraphic studies have been carried out on ditch cutting samples from KR-1 well located in the offshore area of the Niger delta. The Agbada Formation sediments are made up of shales and sandy shales which are grey in colour with intercalations of medium to fine grained sandstone beds. The shales are fissile and slightly calcareous while the sandy shales are light grey, ferruginous and sub-fissile. The sediments yielded rare planktonic but relatively rich benthonic foraminifera and calcareous nannofossils with significant variations in abundance and diversity. The important foraminifera recovered are Globigerina ciporoensis angustiumblicata, Globigerinoides praebulloides, Lenticulina inornata, Epistominella vitrea, Hanzawaia concentrica, Poroeponides lateralis, Quiqueloculina lamarckiana, and Brizalina mandoroveensis while Helicosphaera truempyi, Calcidiscus leptoporus, Cyclicargolithus abisectus, Cyclicargolithus floridanus, Discoaster and Helicosphaera euphrati constitute the principal nannofossils. Early Miocene age was assigned to the section using the top occurrences of some of these taxa while a marginal marine environment of deposition was suggested due to the low diversity of nannofossils and very low planktonic/bentonic ratio.

A surface geophysical investigation involving ground magnetic technique was carried out in Ikogosi warm spring situated in Ekiti South-western Nigeria using a high resolution Proton-precession Geometric Magnetometer model G-856 AX to measure total components of magnetic intensity of the area with the aim of giving details of the subsurface geological structure and evaluating the structural setting beneath the warm spring for probable geothermal energy exploration. Total field magnetic measurements data were acquired along twelve (12) N-S profiles. The Magnetic data interpretation applied was able to depict fractured and faulted areas within fresh massive Quartzite at varying depths beneath all the profiles. Profile 12 has the highest amplitude of 748 nT while profile 3 has the lowest amplitude of 81.1 nT. The magnetic anomaly obtained varied between a minimum negative peak value of -235.9 nT and a maximum positive value of 748 nT. The approximate depth to basement rocks ranges between 8 to 14 m. The magnetic contour, 3-D surface, 1-Grid, Image Maps showed that the magnetic anomalies are as a result of Hot dry rocks present in the study area which contributes to the temperature of the spring. Also the highly mineralized area is between profile 1 and 4. It was deduced that the fractured/faulted quartzite may have acted as channel for the movement of warm groundwater from high depths to the surface.

Water has been a precious resource for human life. The extent of utility of water resource for any purpose is dependent on a variety of factors like economic development, standard of living, industrialization and agriculture practices in a particular region. The ground water is a major source of domestic and agricultural activities in the present study area. The study area is classified into two divisions, the northern Command area and the southern Non-command area both lying in the same climatic region. The Command area is occupied by limestones and the Non-command area by hills of Quartzites, Phyllites and Shales. The results revealed that ground waters in the study area are slightly alkaline in nature. In terms of potability, although, concentrations of many parameters are within the limits of dirnking water quality standards (WHO (1993), ISI(1991) the ground water of the area is effected by the excess of salinity content, the excess of which can cause gastrointestinal problems to the local population.

The development of the field was considered by running the cashflow analysis and establishing the economic indications. The one-well scenario was only able to produce 50% of EUR (2.8MMbbl) while the two-well scenario gave up to 80% EUR (4.7MMbbl) before abandonment rate for a field life of about 15 years. The cashflow analysis showed an attractive marginal project with positive Net Present Value for the $50/bbl base oil price scenario and the contractor’s take was estimated to be about 22% of the total share. The greatest effect on the NPV was seen from the Petroleum Profit Tax and the oil price in the sensitivity analysis which is negative and positive respectively. OWA marginal field reflects a typical low reserve development category and with effective cost management even at extreme low crude oil prices, a marginal profit can be ascertained and eventually fostering the Nigeria economy.