scholarly works
Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/564
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Item 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.Item Analysis of water cresting in horizontal wells(Society of Petroleum Engineers, 2009) Okwananke, A.; Isehunwa, S. O.Horizontal well application has sometimes been employed as a way of minimizing excessive water production arising from coning commonly encountered during oil production in vertical wells. Lots of efforts on water coning in vertical wells have been published. Available predictive models in horizontal wells vary from rather simplistic to complex models. This study investigated the development of practical models that combine ease of use with accuracy. Conformal mapping was used to combine steady state flow, volumetric voidage and pressure drop due to gravity effects in horizontal wells to obtain models that predict critical rates and breakthrough times. The results were compared with some existing correlations under varied reservoir fluid and rock properties. The models were also applied to vertical wells. It was also observed that critical rates and breakthrough times in horizontal wells are affected directly by effective permeability, well length, oil column height, density contrast between wafer and oil, !he height of the water crest. There is however, an inverse relationship with oil viscosity and production rate. It is concluded that simple and accurate correlation that can be applied to coning problems in both horizontal and vertical wells have been developed. They provide a means of comparing the performance of horizontal and vertical wells.Item 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.Item 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 developedItem 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.Item Estimation of developed reserves in gas lifted wells.(Society of Petroleum Engineers, 2009) Daniel, A.; Isehunwa, S. O.Reliable estimates of petroleum reserves are invaluable in reservoir management decisions and economic evaluation. Classical decline curve analysis techniques have been routinely used and are generally accepted in the industry to reliably estimate developed reserves up to a predetermined economic limit qec in oil wells. However Decline curve analysis techniques are based on the assumption that past production trends and their controlling factors will continue in the future and therefore can be extrapolated for predictions. During gas lifting, production trends could be distorted hence there is need to modify the classical decline curve analysis equation. In this study, the principle of superposition has been applied to the entire duration of production (t) of wells producing under gas lift. This resulted in the so called Double Semi log equation for well decline analysis. Model validation with two fields in the Niger Delta area show excellent results and the economic advantage of gas lifting. The Models showed excellent correlation coefficients with available field data. It is concluded that gas lift could increase the reserves in some wells. Furthermore the Double Semi log technique provides a better and more reliable theoretical foundation, easier and more reliable technique for decline analysis in gas lifted wells.Item 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.Item 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.Item 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.Item 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.