Advanced Materials Research Vols. 62-64

Abstract: One of the major ecological and environmental problems confronting the Niger Delta region of Nigeria today is degradation and hazard arising from oil spill. Spillage occurs in this region either from vandalisation or sabotage by ethnic militants, youths who are jobless and therefore deliberately break open crude oil transport pipelines to scoop fuel for sale in the black market to earn a living or rupture of pipes due to ageing and mechanical malfunction. In most spillages, farmlands are lost, aquatic and wildlife is affected, and people are in many cases displaced from their homes. In extreme cases as occurred in Jesse, lives were lost. This paper examines the use of Geoinformation technology in oil spill response modelling and management. The use Global Positioning System (GPS) derived data for the creation of a management database is discussed. Data generated from the Jesse spill and fire site covering these areas were used to generate case study scenario for oil spill response modelling and clean up management operation.

Abstract: This paper investigates the use of redox parameters as a measure of the environmental impact assessment of soil contaminated with polycyclic aromatic hydrocarbons. The levels of naphthalene and anthracene which were used as model contaminants in the soil were periodically monitored along with ferric sulphate and nitrate at ambient conditions. The Brucine and Gelatin Barium methods were employed in estimating the nitrate and sulphate reductions. Experimental results revealed that the microbial utilization of nitrate was faster than that of sulphate; an indication that nitrate is the basic nutrient which provides nitrogen for the metabolic processes occurring during soil remediation. The percentage absorption for both nitrate and sulphate was comparatively higher for the soil unimpacted with polycyclic aromatic hydrocarbons, approximately 49.3% and 26.12% respectively. The percentage absorption of nitrate and sulphate for soil spiked independently with naphthalene and anthracene was found to be 42.18%; 31.21% and 22.93%; 19.74% respectively. The percentage reduction of naphthalene and anthracene in the nitrate and sulphate enhanced soil was 47.5%; 43.1% and 42.5%; 36.5% respectively. These results further affirm that the higher the molecular weight of the polycyclic aromatic hydrocarbon, the slower the rate of its degradation.

Abstract: This paper examines the relative permittivity of irradiated and non-irradiated crude oil samples in the frequency range 0.1 – 100.0MHz and room temperature regulated at 25 ± 1oC. Samples of crude oil of mean specific gravity 0.780 ± 0.015 were irradiated for periods of two, four, six, eight and ten months respectively using a gamma radiation source (Cobalt 60) at a dose rate of 0.65mSv per hour. Dielectric measurements were made by using a Boonton RX meter type 250A admittance bridge manufactured by central research Laboratories, Inc, Red, Wing, Minnesota. Analysis of the resulting dielectric data revealed that both the irradiated and non-irradiated samples exhibited dielectric dispersion over the frequency range investigated. However, the relative permittivity values of the irradiated samples were found to be higher than those of the non-irradiated sample. This difference is understandable as it can be attributed to the ionization of atoms and weakening of molecular bonds in the irradiated samples. The increase in relative permittivity for the irradiated samples was observed to be time dependent as the longer the time of irradiation of sample the higher the value of its relative permittivity. Also, in this study, it was observed that the non-irradiated crude oil sample has longer relaxation time than the irradiated ones. The relaxation time decreases gradually with increasing irradiation time. This has physical significance on the basis of the molecular theory of matter and the fact that relaxation time is inversely proportional to relaxation frequency. These results are comparable with the work of other researchers for which similar trends have been observed.

Abstract: This paper considered the toxicity assessment of some crude oil contaminated soils in Niger Delta areas. The soil samples were collected from different horizontal distances, vertical depths and contaminated soil of different ages. The heavy metals in the contaminated soils were digested and extracted using di-acid digested and DTPA extraction methods respectively. The physiochemical parameters (moisture content, pH, N, P and heavy metals (Ni, Pb and Cd) were analysed with APHA method. The heavy metals concentration was determined using atomic absorption spectrophotometer (AAS). The results show that the metals concentration decreased with the age of the contaminated soil and with increased vertical depths. However, the metals concentrations were almost constant at different horizontal distances. Similar trend was observed for the moisture content, pH, N, P and K.

Abstract: Casing drilling can be an effective method of reducing drilling costs and minimising drilling problems but its uptake around the world has been slow with only a few wells drilled so far with casing. Complex geological features like the high overburden on top of shallow unconsolidated reservoirs characteristic of offshore West Africa can benefit from casing drilling when effectively combined with Managed Pressure Drilling technique. For the industry to develop a managed pressure drilling capability that will allow today’s generation of complex wells to be drilled safely with casing, it is necessary to develop models that include the effect of eccentricity , rotation and fluid rheology at bottom hole conditions on flow and pressure regimes, and to embed these models within an easy to use, intuitive well design package for pre planning and as a real time tool to monitor and provide forward simulations based on real time rig and downhole data. The paper presents new results of the theoretical predictions of the wellbore pressure regimes incurred when different types of drilling fluid flows in concentric and eccentric horizontal annuli. The concentric and eccentric casing drilling results are compared with parallel predictions from conventional drillstring results from developed analytical solutions integrated into the VisWELL(DeskTop Simulator) , which is used in simulating well operations.

Abstract: Development of appropriate strategy for the management of reservoirs with sanding problems is rather complex and requires an integrated approach to finding the optimum solution to solving the problem. This requires integration of key aspects of reservoir characterisation, drilling, completion and production technologies including sand tolerances (Seabed wellhead/flow lines, topside facilities. Providing an accurate forecast of the tolerance depends on accurate prediction of sand failure and the corresponding volume of produced sand. This is a transient phenomena further complicated by gas reservoir fluid flow. In this paper the results of a comprehensive Thick Wall Cylinder[TWC] experimental sand production studies carried out on synthetic sandstones are presented. The sand production prediction model for liquid flow are further calibrated and upscaled with field data for gas reservoirs. The prediction model developed is further validated with independent field data with good results. The results represent a first for sand production forecast for gas reservoirs. Mitigation of sanding requires reliable sanding prediction, precise well design, accurate technology selection as well as optimum completion strategy.

Abstract: A new equation for the viscosity of Natural Gas under Reservoir conditions has been developed. The equation was obtained by the analysis of experimental Pressure, Volume and Temperature (PVT) Data of Gas associated with Nigerian Crude Oil. The PVT Data were those of renowned companies that operate in Nigeria. The pressure ranged from 144 psia to 4100 psia, and a temperature variation between 130oF and 220oF. Comparison of the equation formulated in this work with experimental PVT viscosity gave an average absolute error of 1.55%, a maximum absolute error of 4.878% and a standard deviation of 1.29. A comparison of viscosity obtained from the charts of Carr et al and the equation of Lee et al with Nigerian PVT Viscosity showed that the new equation gave more accurate result. Since some Correlations perform better when applied to data from which they were derived, a further comparison test was performed. In this test, the new equation was used to solve two problems for which solutions by the method of Carr et al were available. The first problem from the Handbook of Natural Gas Engineering by Katz et al gave a viscosity of 1.158cp while the new equation gave 1.157cp. The second problem from Ikoku’s book (Natural Gas Production Engineering) gave a viscosity of 1.178cp and the new equation also gave 1.178cp. This closeness of the viscosity of the new equation to the values from the Carr et al method proved the applicability of the new equation to any type of Natural Gas.

Abstract: New equations for calculating the Gas Deviation Factor (z) and the Compressibility of Nigerian Natural Gas have been developed. The equation for the Gas Deviation Factor was developed from a plot of the logarithm of the ratio of Pressure to Temperature versus the logarithm of the ratio of the Pressure to the Gas Deviation Factor.. The plot gave a linear relationship that gave the Gas Deviation Factor equation. A differentiation of the Gas Deviation Factor equation produced the new equation for calculating the Gas Compressibility. Values from the new equation for calculating the Gas Deviation Factor were compared with experimental Pressure, Volume, Temperature (PVT) measurements and the following statistical measurements of accuracy were obtained: Average percent error of 3.050, average absolute percent error of 3.649 and standard deviation of 3.910. Over 75% data tested showed error less than 5 %. A big advantage of the new equations is that they are simple and do not require pseudo critical pressure and pseudo critical temperature needed to obtain z from the current popular equations of state used in the Oil Industry. The data used to develop the model in this work came from Gas associated with produced oil in the Niger Delta. API gravity of the oil, ranged from 17.4 to 44. Pressure ranged from 15 psia to 4015 psia and Temperature ranged between 127 and 205 degree Fahrenheit. This range of data covers at least, ninety five percent of data used in the upstream sector of the Nigeria Oil and Gas Industry.

Abstract: Zimbabwe has an abundance of the renewable energy sources yet it is facing chronic energy and capacity shortages, leading to the country relying on imported power, having load shedding and having blackouts. This paper discusses the renewable energy power potential, the role renewable energy resources can play to alleviate these problems and the policy options and instruments that can be used to promote renewable energy technologies. The study found out that Renewable Energy Technologies are cost-competitive to conventional energy sources in several applications. The major barriers to the deployment of the technologies are discussed and possible solutions proposed.

Abstract: Tracking solar-power devices often employ photovoltaic position sensors to detect the angle of misalignment between the axis of mounted solar panels and that of sunlight. The nonlinear input-output characteristics of this type of sensors tend to complicate controller design in such systems. This paper presents a nonlinear mathematical model of the photovoltaic position sensor. A three-layer feedforward neural network was trained to linearise the characteristics of the sensor. The MATLAB neural network tool (nntool) was used for neural network training. A final error of was obtained after training. Simulation of the neural network showed that linear sensor characteristics could be reproduced throughout the domain of sensor operation.