Browsing by Author "Isehunwa, S. O."

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An analysis of formation damage during the drilling of deviated wells
(Taylor and Francis, 2013) Akinsete, O. O.; Isehunwa, S. O.
Filtrate losses and filter cake properties of drilling fluids are of concern in the oil industry because they alter near well bore permeability and can reduce well productivity. Therefore, it is desirable to accurately characterize filtration process during oil well drilling. A mathematical model for analyzing mud filtration in deviated wells was developed in this study. The model determined solid pressure distribution within cake, cake thickness, cumulative volume of filtrate and extent of invasion under different conditions. Results show assumptions of isotropy in previous studies greatly overestimate the magnitude of the damage. It was also confirmed that mud filtration tend to be higher in deviated than in vertical wells. The model was validated with experimental data.
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.
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.
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.
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 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.
Effect of temperature and contamination on the surface tension of Niger Delta crude oils
(2011) Isehunwa, S. O.; Udeagbara, S. G.; Akpabio, J. U.
Surface tension is an important property that affects the behavior and characteristics of reservoir fluids. It impacts the capillary pressure and fluid dynamics in porous media. This study investigated the surface tension of Contaminated Niger Delta crude oil at varying temperatures. Laboratory tests were carried out on samples from four fields in the Niger Delta using DuNouy Tensiometer under standard conditions. The results show that for Niger Delta Crudes of gravity between 25 - 49 API, Surface Tension varies between 25.8 - 31.2 dynes/em at 29°C and decreases to between 21.5-26.6 dynes/em at 90°C. Surface Tension of the crudes was also affected by salt contamination, bentonite and mud filtrate and surfactant contamination. Contamination by bentonite also increased the surface tension from about 28 to 34 dynes/em. Predictive models have been developed as a quick-look tool for estimating surface tension of Niger Delta crude oil and similar reservoir fluids.
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.
Estimation of the refractive indices of some binary mixtures
(AcademicJournals, 2015-04) Isehunwa, S. O.; Olanisebe, E. B.; Ajiboye, O. O.; Akintola, S. A.
Refractive index is a useful fluid characterization parameter with widespread industrial applications. The value for many pure liquids are known or readily available in literature. However, when experimental literature are not available, the refractive indices of binary and multicomponent liquid are often estimated from the pure components using mixing rules which are sometimes not accurate. This study was designed to measure the refractive indices and evaluate the accuracy of some commonly used mixing rules when applied to benzene-toluene, heptane-hexane, hexane-acetone, heptane-acetic acid and acetic acid-acetone binary mixtures at varying volume fractions and temperatures between 20 and 60˚C. A simpler relation based on modified Kay or Arago-Biot mixing rule was demonstrated to have wider range of applicability because of the explicit temperature-dependence term.
Evaluation of drilling muds enhanced with modified starch for HPHT well applications
(Springer, 2020-10) Sulaimon, A. A.; Akintola, S. A.; Johari, M. A. B. M.; Isehunwa, S. O.
The use of carboxymethyl cellulose (CMC) in oil and gas well drilling operations has improved the filtration loss and mud cake properties of drilling muds. The introduction of starch has also reduced, for example, the viscosity, fluid loss, and mud cake properties of the drilling fluids. However, normal starch has some drawbacks such as low shear stress resistance, thermal decomposition, high retrogradation, and syneresis. Hence, starch modification, achieved through acetylation and carboxymethylation, has been introduced to overcome these limitations. In this study, modified starches, from cassava and maize, were used to enhance the properties of water-based muds under high-pressure high temperature (HPHT) conditions, and their performances were compared with that of the CMC. The mud samples added with acetylated cassava or maize starch exhibited the smallest filtrate volumes and filtrate losses within the American Petroleum Institute specification. Therefore, these modified starch-added muds could replace CMC as fluid loss agents since, unlike it, they can withstand HPHT conditions.
Evaluation of produced water discharge in the Niger-Delta
(Asian Research Publishing Network, 2011-08) Isehunwa, S. O.; Onovae, S.
Water produced during petroleum production often contains chemicals, oil and sometimes, naturally occuring radioactive materials which could harm the environment. Management, which involves significant cost and is guided by strict regulations, is normally aimed at minimizing or reducing the toxicity of discharged volumes. This study evaluated the physio-chemical properties and constituents of produced water from three selected flowstations and two oil terminals in the Niger Delta to determine the extent of compliance with standard and global best practices in the treatment and discharge. It was observed that while physio-chemical properties like pH (8.4±0.25) and BOD (6.2±2.0) were within recommended limits, oil and grease content (60±20), TDS (6200±700) and others exceedded limits. Similarly, ion concentrations of Lead, NIckel, Zinc and Sulphates were within acceptable limits while Chloride ions (4 100 ±500) exceeded limits. There is therfore the nedd to improve treatment facilities and procedures, while regulatory agencies must improve current guidelines, ensure proper monitoring and enforcing compliance.
Experimental determination of the molecular weight of some binary mixtures and petroleum liquids
(SENRA Academic Publishers. British Columbia, 2013-02) Isehunwa, S. O.; Adetoyi, G. A.; Oguamah, I. A.
Accurate molecular weights of pure compounds are available and can be readily obtained in the literature. However, those of binary and multi-component mixtures are not readily available and are usually obtained from pure components by applying mixing rules, which may not be very accurate. The molecular weights of n-Nonane+n-Tetradecane. n-Hexane+n-Nonane. n-Hexane+Toluene. Toluene+n-Tetradecane and some petroleum liquids were experimental I: determined using a cryoscope. The results were compared with estimates from Kay's mixing rule and the observed deviations used to modify Kay's equation in order to obtain an improved mixing rule for the molecular weight of binary mixtures. A simple relation was also established for predicting molecular weight of petroleum liquids from API gravity. The average absolute deviation (AAD) of 0.04 and 0.40 for the molecular weight of heavy and light petroleum liquids respectively represents an improvement over most of the existing correlations.
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.
Interfacial tension of crude oil-brine systems in the Niger Delta
(2012-03) Isehunwa, S. O.; Olanisebe, O.
Interfacial tension in crude oil - brine systems is becoming very important with increasing global efforts for increased oil reserves from enhanced oil recovery projects. Interfacial tension has direct impact on multiphase flow and displacement processes in porous media. It also affects the behaviour of oil field emulsions. Most published two-phase flow and displacement processes carried out under different interfacial tension have been performed for either oil-gas or water-gas two-phase systems. This work investigated the effect of salinity, temperature and oil viscosity on the interfacial tension of oil brine systems from five different Niger Delta reservoirs. The results show that there is a strong relationship between temperature, salinity, oil viscosity and interfacial tension in heavy crude-brine systems (R2 ˃ 0.88 and P ˂ 0.05), between temperature, salinity and interfacial tension in light crude-brine systems (R2 = 0.91 and P ˂ 0.05), but no conclusive relationship in medium crudes-brine systems.
A model for predicting sand production in horizontal wells
(Nova Science Publishers, Inc., 2012) Isehunwa, S. O.; Nwokeke, N.; Olanrewaju, O.
Sand produced along with oil and gas causes operational, safety, environmental and severe economic challenges. The cost of installing sand control facilities which may not really be needed could also be substantial. Therefore, determining the critical flow rate for the onset of sand production is very important. There are several published studies on sanding in vertical wells, but few on horizontal wells, which have now become very prominent in the industry. The aim of this study was to develop a simple but robust model for predicting sand rates in horizontal wells. A novel geomechanical model incorporating gravity, buoyancy, drag and lift forces was developed and validated with data from 3 oil fields in the Niger Delta. The results showed that sand production could take place in horizontal wells even at low production rates but increases at high production rates in the fields of study. Critical sand rate is also affected by horizontal well length, fluid viscosity and diameter of the sand particles.
New referencing technique for reservoir oil viscosity estimation
(EuroJournals Publishing, Inc., 2012) Isehunwa, S. O.
Reservoir oil viscosity is important in understanding reservoir flow behaviour, facilities design and sizing and in the computation of recovery performance, well' productivity and lift requirements. Direct viscosity measurements are expensive or sometimes unavailable hence empirical correlations are often used for predictions. However, several published correlations are either too simplistic or complex for routine operational use and improved methods continue to receive attention. This study used a semi-theoretical approach to relate reservoir oil viscosity to well-head oil viscosity which can easily be obtained. Results were analyzed statistically and tested with field data obtained from the Niger Delta. The viscosity relation factors developed gave an absolute average relative error (AARE) of 14.1% for undersaturated reservoirs and an AARE of 2.4% for saturated oil reservoirs. It is concluded that measured well-head oil viscosity can be used with good accuracy, as reference liquid instead of dead oil viscosity that has been commonly used for estimating reservoir viscosity.
Prediction of flowing bottomhole pressure in gas-condensate wells
(Nova Science Publishers, Inc., 2013) Akinsete, O. O.; Isehunwa, S. O.
Bottom-hole pressures in gas and condensate wells are frequently measured at a great cost and with operational challenges. On the other hand, most analytical estimation procedures either use trial and error or neglect liquid holdup in condensate wells. Using the mechanical energy balance approach, an approximate model was developed to estimate bottom-hole pressure from wellhead pressures in condensate wells without neglecting liquid holdup. The results show that treating gas condensate like dry gas wells lead to over prediction (10-15%) of flowing bottom-hole pressures, with serious consequences on phase behaviour, reservoir characterization and production management.
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.
The prospect of using palm wine as a fluid loss control agent in water based drilling mud
(Avanti Publishers, 2016) Akintola, A. S.; Isehunwa, S. O.; Oboh, S. M.
The need to advance and project the use of local materials as suitable drilling fluid additive in the oil and gas industry in Nigeria led to the research on the possible use of palm wine and potash as additives in a water base drilling mud. A comparative study of these local materials (palm wine and potash) with imported foreign materials (lignite and caustic soda) as control were used in investigating the properties of a water base drilling fluid. A laboratory investigation of the effects of temperature and aging time on the properties of water-base drilling fluid is made with Fann Model 800 High Temperature and a High Pressure (HTHP) Viscometer, according to the API recommended standard practice. The results obtained showed similarity in the drilling fluid’s rheological and filtration properties; mud weight and pH values for both local and foreign additives. The result from the mud sample prepared from the palm wine and potash had apparent viscosity, plastic viscosity and yield point decreasing steadily with increase in temperature for all aging time just as shown with the control sample, while the aging effect diminishing as the aging time increases. The potash was seen to have increased the mud pH from 7.0 to 12.9 pH units. The results, shows that both palm wine and potash can be used as suitable in water base drilling mud additive.
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.