scholarly works

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Nigeria Gazette
(The Government Printer, Nigeria, 1953-01) Federal Government of Nigeria
A correlation for predicting the viscosity of Nigerian crude oils
(Society of Petroleum Engineers, 1990) Amoo, O. A.; Isehunwa, S. O.
An empirical equation that could be used for predicting the viscosity of Nigerian crudes is presented in this paper. The correlation uses oil specific gravity as the main correlating parameter, and also incorporates the effects of reservoir pressure, temperature and oil formation volume factor. Data from well over 400 samples of Nigerian crudes were used for developing the correlation, with most samples however, from reservoirs at or above saturation pressure. The results show however that the correlation could have general applicability. The correlation when compared with some earlier works proved to be more accurate for Nigerian crudes. Graphical and Statistical error analyses undertaken suggest good performance and accuracy. The correlation should prove valid for estimating the viscosity of Nigerian crudes, as well as other crude types having properties that fall within the range of the data used in this work.
A type curve approach to qualitative description of reservoir fluids
(Society of Petroleum Engineers, 1993) Isehunwa, O. S.; Falade, G. K.
Qualitative description of reservoir fluids is normally based on such parameters as saturation pressure, gas in solution, viscosity and density. Most Engineers ignore compositional data unless when phase behavior predictions or compositional simulation are to be undertaken. This work describes a simple, quick method of qualitative reservoir crude assessment, using the well known Type Curve matching techniques with fluid compositional data. The method is demonstrated for some Niger Delta reservoir crudes, and shown to be useful in checking the validity of laboratory PVT results in cases where there are disagreements between the experimental and observed (field) values of saturation pressure. Volatile crudes and condensates can also he readily identified. It. would appear that the method can be applied regionally, as well as locally (in-field) as an aid in reservoir-to-reservoir fluid correlation. It can also help to ide1ltify non-equilibrium fluid distribution in. large, thick, or segmented reservoirs.
A two-parameter correlation for predicting oil recovery factor in water-drive reservoirs
(Society of Petroleum Engineers, 1994) Isehunwa, S. O.; |Nwankwo, S. U.
A simple correlation has been developed for estimating primary recovery factors for Niger Delta oil reservoirs. The correlation which was developed, from data collected across the Niger Delta, is valid for reservoirs with strong water drives. Only two major parameters are required for the recovery factor calculations in this work, unlike other multi-parameter correlations. This makes this correlation very easy to apply. An expression has also been included for predicting residual oil saturation, where core or log analysis data are not available. The results obtained using these models have been compared with other published models, and applied to many case studies, with better predictions. Graphical and statistical error analyses also confirm good correlations. These correlations should also, yield good predictions for reservoirs from other regions that have similar reservoir and fluid characteristics.
Analysis of mud filtration properties using factorial design
(Society of Petroleum Engineers, 1995) Isehunwa, S. O.; Orji, H. I.
Determining the filtration properties of a mud system requires that experiments be run for both the standard API and the high Temperature High Pressure (HTHP) tests at intervals throughout the duration of drilling an oil well. However, cost and hazard considerations cause more emphasis to be placed on the standard API test at ambient conditions, without taking into account the effects of elevated downhole pressures and temperatures on filtration properties. In this work, the factorial design concept was applied to the filtration properties of drilling muds. Different samples of water based bentonitic muds were used for the experimental runs at both Low Temperature - Low pressure (LTLP) and high Temperature - High Pressure (HTHP) conditions. The input variables considered were temperature, pressure, solids content, mud weight and time; while the response variables were fluid loss and cake thickness. The final results are presented in the form of a statistically significant model that enables prediction of filtration properties at both LTLP and HTHP conditions. This method minimizes the inherent risks usually associated with operating filter presses at elevated pressures and temperatures. In addition, it saves time and cost by minimizing the number of experimental runs always required to assess mud quality and maximizes the information obtained from the few experimental runs. This experimental design technique can also be applied to the quality assessment and control of other drilling fluid properties.
Generalized analysis of the multi-well interference test in hydrocarbon reservoirs
(2003) Falade, G. K.; Isehunwa, S. O.
This study presents a generalized analytical formulation of the Multi-Well Interference test problem using the concept of the source arid sink functions as a tool for solving the basic interference equations. The much broader case, featuring inner well boundary conditions with skin and storage factors at both the active and the several observation wells, is considered. The general nature of the formulation allows for the analyses of non-homogeneous reservoirs and hence the concepts of reservoir directional permeability and the related issues of reservoir principal axes of permeability were addressed. Most of the published cases of interference tests were identified as limiting cases of the generalized formulation.
Improved reservoir description using surface oil viscosity data
(Society of Petroleum Engineers, 2003) Umeh, N.; Isehunwa, S.; Okorafo, C.; Owolabi, S.; Agu, I.; Olare, J.; Biambo, T.
Subsurface oil viscosity data are usually not readily available for most reservoirs, as they are expensive to acquire. On the other hand, surface oil viscosity is routinely measured and therefore readily available for all producing wells. A method has been developed for converting the surface viscosity to reservoir viscosity data, using SPDC's "Field A" as a case study. Surface oil viscosity data from all producing wells in "Field A" where collected from SPDC-West Production Chemistry laboratory and converted to reservoir viscosity using a simple method that utilizes relevant PVT data. The method allows a better and more detailed subsurface description of reservoir viscosity in line with facies variations. The study also shows that reservoir oil viscosity could be lower in some sands than previously estimated. This gave a significant impact on reserves in one of the reservoirs where scope to increase the booked reserves by about 60 MMstb was observed. Opportunity to also –increase constrained off take from 2300 b/d to 3000 b/d in some planned new wells was also observed.
Science, engineering and technology in Nigeria. Problems and prospects
(Centre for Local Government and Rural Development Studies, 2004) Isehunwa, S. O.
A general overview of the evolution and development of science, engineering and technology in Nigeria has been presented. Five phases of development were Identified between 1960 and 2003. It was observed that while significant efforts have been made at establishing the institution and infrastructure necessary for industrialization, the third important requirement, namely a conducive and political climate has been largely missing. This has led to delay in achieving industrial revolution in the country Other problems affecting science, engineering and technology were identified and some practical solutions have been recommended.
A simple generalized equation of state
(Society of Petroleum Engineers, 2005) Isehunwa, O. S.; Falade, G. K.
A pressure perturbation technique based on a simple adaptation of the Weirtheim's first order thermodynamic perturbation theory has been developed and used to formulate a generalized equation of state. The practical equation formulated was applied to pure fluids, binary systems and real samples of Niger Delta Petroleum fluids. Tuning of data is not required. The results show more accurate predictions than the commonly used SRK and PR equations. This work provides a theoretical framework for improving the accuracy of cubic equations of state. One major advantage of the generalized equation expressed in this work is the fact that it provides a theoretical framework for explaining the physical significance of the parameters in multi-parameter equations of state. Thus, in a three-parameter equation of state, while 'a' captures the attractive forces, 'b’ is the co-volume, 'c ' could represent non-physical forces. This is different from the concept of 'c' in such equations as Peng-Robinson EOS where 'c ' obviously represents an "after-the-fact" volume correction term.
Machining of nickel-base, Inconel 718, alloy with ceramic tools under finishing conditions with various coolant supply pressures
(Elsevier Limited, 2005) Ezugwu, E. O.; Bonney, J..; Fadare, D. A.; Sales, W. F
Machining of Inconel 718 with whisker reinforced ceramic tool gave better performance in terms of tool life under high-pressure coolant supplies up to 15 MPa compared to conventional coolant supplies. The use of 15 MPa coolant supply pressure tend to suppress notching during machining thus improving tool life, while the use of higher coolant supply pressure of 20.3 MPa did not show improvement in tool life due probably to accelerated notch wear caused by water jet impingement erosion, Cutting forces decreased with increasing coolant supply pressure due to improved cooling and lubrication at the cutting interface as well as effective chip segmentation ensured by the momentum of the coolant jet. Surface roughness generated were well below the rejection criteria. This can be attributed to the round shape of the insert which tend to encourage smearing of the machined surface with minimum damage. Microstructure analysis of the machined surfaces show evidence of plastic deformation and hardening of the top layer up to 0.15 mm beneath the machined surface as a result of increase in dislocation density.
Application of generalized pressure perturbation principle to cubic equation of state formulation
(Society of Petroleum Engineers, 2005) Isehunwa, S. O.; Falade, G. K.
Cubic equations of state are commonly used for predicting the properties of reservoir fluids. They are simple to use and require few parameters during computations. They have also been found to produce results that are comparable to the more rigorous multi-parameter equations. However, they are still regarded by many as mere comprehensive correlations of fluid properties because of a number of weaknesses and /imitations. This work addresses two weaknesses of cubic equations of state commonly highlighted in literature, viz: that they do not seem to have deep theoretical foundations and are not as accurate as non-cubic equations. A pressure perturbation technique based on a simple adaptation of the Weirtheim's first order thermodynamic perturbation theory has been developed and used to formulate a cubic equation of state. The practical equation formulated was applied to pure fluids and samples of Niger Delta Petroleum fluids. The results show more accurate predictions than the commonly used SRK and PR equations. This work suggests that cubic equations could have deeper theoretical.
Modelling the correlation between cutting and process parameters in high-speed machining of Inconel 718 alloy using an artificial neural network
(Elsevier Limited, 2005-03) Ezugwu, E. O.; Fadare, D. A.; Bonney, J.; Da Silva, R. B.; Sales, W. F.
An artificial neural network (ANN) model was developed for the analysis and prediction of the relationship between cutting and process parameters during high-speed turning of nickel-based, Inconel 718, alloy. The input parameters of the ANN model are the cutting parameters: speed, feed rate, depth of cut, cutting time, and coolant pressure. The output parameters of the model are seven process parameters measured during the machining trials, namely tangential force (cutting force, Fz), axial force (feed force, Fx), spindle motor power consumption, machined surface roughness, average flank wear (VB), maximum flank wear (VBmax) and nose wear (VC). The model consists of a three-layered feedforward backpropagation neural network. The network is trained with pairs of inputs/outputs datasets generated when machining Inconel 718 alloy with triple (TiCN/Al2O3/TiN) PVD-coated carbide (K 10) inserts with ISO designation CNMG 120412. A very good performance of the neural network, in terms of agreement with experimental data, was achieved. The model can be used for the analysis and prediction of the complex relationship between cutting conditions and the process parameters in metal-cutting operations and for the optimisation of the cutting process for efficient and economic production.
Carbon(IV)oxide Capture and Sequestration in Nigeria: Prospects and Challenges
(Society of Petroleum Engineers, 2006) Isehunwa, S. O.; Makinde, A. A.; Olamigoke, O.
The capture and storage of carbon dioxide (CCS) produced during the combustion of fossil fuels now offers one option for attaining large scale reductions in the emissions of greenhouse gases and thus, promote a clean environment. It is now becoming clear that CCS technologies could promote the use or consumption of fossil fuels than otherwise previously thought. This paper presents an overview of the techniques involved in the capture and sequestration of carbondioxide(CO). The opportunities and the challenges of the application of CCS in Nigeria are considered. It is concluded that the development of gas utilization schemes and power plants makes it imperative for Nigeria togive attention to CCS technologies.
A correlation to predict the viscosity of light crude oils
(Society of Petroleum Engineers, 2006) Isehunwa, O. S.; Olamigoke, O.; Makinde, A. A.
Direct viscosity measurements are often expensive or unavailable. Therefore, empirical correlations are often used for predicting the viscosity of crude oils. However, several published correlations are either too simplistic or too complex for routine operational use. Many of the common correlations in use were developed using data from other regions of the world, Empirical correlations for predicting the viscosity of light crude oils in the Niger Delta have been presented in this paper. Data from over 400 oil reservoirs from the Niger Delta were collected. The samples were representative of the two crude oil viscosity regimes: above and below the bubble point. After normal quality checks, non-linear multiple regression with linear partial correlation coefficient techniques were used to establish simple correlations between viscosity, pressure, temperature, oil specific gravity and solution gas oil ratio. Statistical error analysis of the developed correlation showed average absolute relative percentage error of 4.00% and 3.25% and R2 of 0.99 and 0.97 for oil viscosity above and below the bubble point respectively. These results constitute considerable improvements over existing correlations.
Energy analysis for production of powdered and pelletised organic fertilizer in Nigeria
(Asian Research Publishing Network, 2006-06) Fadare, D. A.; Bamiro, O. A.; Oni, A. O.
Energy study was conducted in an organic fertilizer plant in Ibadan, Nigeria, to determine the energy requirement for production of both powdered and pelletised organic fertilizer. The energy consumption patterns of the unit operations were evaluated for production of 9,000 kg of the finished products. The analysis revealed that eight and nine defined unit operations were required for the production of powder and pellets, respectively. The electrical and manual energy required for the production of powdered fertilizer were 94.45 and 5.55% of the total energy, respectively, with corresponding 93.9 and 5.07% for the production of pelletised fertilizer. The respective average energy intensities were estimated to be 0.28 and 0.35 MJ/kg for powder and pellets. The most energy intensive operation was identified as the pulverizing unit with energy intensity of 0.09 MJ/kg, accounting for respective proportions of 33.4 and 27.0% of the total energy for production of powder and pellets. Optimisation of the pulverizing process is suggested to make the system energy efficient.
Modelling the association between in vitro gas production and chemical composition of some lesser known tropical browse forages using artificial neural network
(2007) Fadare, D. A.; |Babayemi, O. J.
In vitro gas production of four different browse plants (Azadirachta indica, Terminalia catappa, Mangifera indica and Vernonia amygdalina) was investigated under different extractions. The relationship between the forage composition parameters (dry matter, organic matter, crude protein, acid detergent fibre, neutral detergent fibre and acid detergent lignin), process parameters (extraction mode and incubation time), and volume of gas production were modelled with artificial neural network (ANN). The ANN model consisted of simple, multi-layered, back-propagation networks with eight input neurons consisting of the composition and process parameters and one output neuron for the gas volume. The networks were trained with different algorithms and varying number of layer and neuron in the hidden layer to determine the optimum network architecture. The network with single hidden layer having 45 ‘tangent sigmoid’ neurons trained with Livenberg-Marquard algorithm combined with ‘early stopping’ technique was found to be the optimum network for the model with R-value: mean = 0.9504; max. = 0.9618; min. = 0.9343; and std. = 0.0059. The influence of each chemical composition and processing parameters on gas production was simulated. The developed ANN model offers a more cost and time efficient strategy in feed evaluation for ruminant animals.
Prediction of the viscosity of a water - base mud treated with cassava starch and potash at varying temperatures using factorial design
(2007) Okumo, I.; Isehunwa, S. O.
In order to monitor and control the properties of drilling fluids, measurements are routinely made at the surface. However, these surface measurements may not be representative of down-hole properties where the desired functions of hole cleaning and other related issues are critical to the success of the drilling operations. Consequently, it is important to make necessary adjustments of the fluid properties obtained at ambient conditions to give estimate of properties at high temperatures and pressures. The principle and method of factorial design have been used to develop a model, which makes possible the prediction of drilling fluid viscosity at varying temperatures. Cassava starch and potassium carbonate were used as local additives in a water based bentonic drilling fluid after running a quality check 23 full factorial design experiments which consider temperature, starch and potash as factor variables and viscosity as the response variable were conducted. The main effects as well as the interaction effects were determined and examined. The results were analyzed and a predictive model was obtained. Viscosity values obtained using the model were compared with the experimental results and it was observed that the model has an accuracy of93.6%. This method makes possible the prediction of the viscosity of drilling fluids at varying temperatures, hence the treatment of mud systems can be determined ahead of time.
Improved characterization of heptanes-plus fractions of light crudes
(Society of Petroleum Engineers, 2007) Isehunwa, O. S.; Falade, G. K.
Heptanes plus fractions have strong effects on the physical properties and phase behaviour of petroleum fluids. It is therefore very important to properly characterize plus fractions. A step to achieving improved characterization is to obtain more realistic molecular weights. Most of the current methods of heptanes plus characterization assume their molecular weights are accurate. However, what is commonly measured in the laboratory is the molecular weight of the complete fluid; the molecular weight of the heptanes plus fraction is then estimated using Kay's mixing rule. Unfortunately, physical properties like molecular weight obtained using 'equivalent fluid' principles by mixing pure components, do not give the same values with actual measurements. Therefore, while a very accurate estimate of the molecular weight of a reservoir oil could be available, that of the heavy fractions, which is 'inferred' could be unreliable, because of the mixing rule. A simple technique has been formulated to achieve improved characterization of petroleum fluids and the heavy fractions. We suggest fine tuning' Kay's mixing rule in order to achieve a match between actual measured molecular weight and the 'equivalent fluid'. Experimental data from over 400 PVT reports from over 100 fields in the Niger Delta were collected and studied A correlation was established between oil gravity and molecular weight and compared with other commonly used correlations. Statistical error analysis was undertaken. Heptanes plus molecular weights which were generally estimated using Kay's mixing rule were found to be generally high and hence fine tuned using a simple technique. The results of this study show that the well-known Cragoe's and Standing correlations gave absolute average deviation of 126.8 and 53.3 respectively for light crudes, compared to 2.5 obtained in this study Furthermore, better description of heavy fractions was achieved with more accurate molecular weight. It is concluded that the proposed technique perhaps provides a theoretical basis for the usual 'tuning' of heptane-plus properties during fluid modelling. It is also concluded that a more accurate correlation for estimating the molecular weight of light crudes has been developed
A statistical analysis of wind energy potential in Ibadan, Nigeria, based on weibull distribution function
(Akamai University, 2008-06) Fadare, D. A.
Modeling of wind speed variation is an essential requirement in the estimation of the wind energy potential for a typical site. In this paper, the wind energy potential in Ibadan (Lat. 7.43°N; Long. 3.9°E; Alt. 227.2m) is statistically analyzed using daily wind speed data for 10 years (1995-2004) obtained from the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. The daily, monthly, seasonal, and yearly wind speed probability density distributions are modeled using Weibull Distribution Function. The measured annual mean wind speed in Ibadan is 2.75 ms-1, while mean wind speed and the power density predicted by the Weibull probability density function are 2.947 m/s and 15.484 Wm-2, respectively. Ibadan can be classified as a low wind energy region. The coefficient of determination (R2) between the actual wind speeds and the Weibull predicted values ranged between 0.475 - 0.792. The Weibull distribution function can be used with acceptable accuracy for prediction of wind energy output required for preliminary design and assessment of wind power plants.
Artificial neural network modeling of heat transfer in a staggered cross-flow tube type heat exchanger
(Akamai University, 2008-11) Fadare, D. A.; Fatona, A. S.
This paper presents the application of Artificial Neural Network (ANN) in modeling the heat transfer coefficient of a staggered multi-row, multi-column, cross-flow, tube-type heat exchanger. Heat transfer data were obtained experimentally for air flowing over a bank of copper tubes arranged in staggered configuration with 5 rows and 4 columns at different air flow rates with throttle valve openings at 10 - 100%. The Reynolds number and the row number were used as input parameters, while the Nusselt number was used as output parameter in training and testing of the multi-layered, feed-forward, back-propagation neural networks. The network used in this study was designed using the MATLAB® Neural Network Toolbox. The results show that the accuracy between the neural networks predictions and experimental values was achieved with Mean Absolute Relative Error (MRE) less than 1 and 4% for the training and testing data sets respectively, suggesting the reliability of the networks as a modeling tool for engineers in preliminary design of heat exchangers.