bluuebunny/crossref_metadata_2025_split huggingface dataset:
Splitting the Heptanes-Plus Fraction of Condensate and Volatile systems: Application of the Gamma Distribution Model
Authors: Imo-Jack Otavie O. , Uche Ifeanyi N. 
Published: August 2012

Abstract
Gas condensates and volatile fluids require detailed Equation-Of-State (EOS) characterization to account for compositional variations with pressure, volume and temperature changes. Proper characterization is important in determining the in-place volumes of gas condensates and volatile systems. These volumes are important in determining reserves which play an important role in driving a company's share value. The in-place volumes also drive sales contracts as well as surface equipment design. Gas condensate reservoirs also pose a serious challenge to well productivity especially below the dewpoint in tight reservoirs due to condensate banking. As this situation may lead to expensive stimulation projects, it is important to optimally define operating standards early in the life of the asset. Accurate PVT characterization of gas condensate fluid is key to defining these standards. It is therefore important to get these fluids properly characterized so as to make the right investment decisions.
EOS characterization of heptanes-plus requires extended analysis beyond the C7+ fraction. In several instances, we do not have True Boiling Point (TBP) data for these heavy components. In cases where available, experimental data still remains the most reliable source of heptanes-plus properties.
Heptanes –Plus in reservoir fluids contains hundreds of different components which are impossible to identify by chemical separation techniques. Even if it were possible to identify them, it would not be possible to measure the critical properties and other EOS parameters for fluids heavier than C20. This problem is solved practically by making approximate characterization of the heavier compounds with experimental and mathematical methods.
A molar distribution model can be used to estimate the properties of heptanes-plus. A molar distribution model is a relationship between cumulative molar quantity and some expression for Cumulative molecular weight. Different methods are used to describe molar distribution. Some methods employ a consistent separation of fractions (e.g., by SCN) thus leading to the expression of the molar fraction as a direct relationship between mole fraction and molecular weight of individual cuts. Most methods in this category assume that C7+ molecular weights decrease exponentially. A more general approach uses the three-parameter gamma probability function to describe molar distribution.
The Gamma distribution model is used in this work to study the splitting scheme of the C7+ and compare this with experimental data from extended analysis to see how they compare. If the results prove to be acceptable, then the three-parameter gamma model becomes an alternative in the absence of hard data to split heavy ends to improve their characterization.
Petrophysical Characterization of Radioactive Sands - Integrating Well Logs and Core Information: A Case Study in the Niger Delta
Authors: Chudi Obinna , Simon Roya 
Published: August 2012

Abstract
The gamma ray (GR) tool responds to the amount of radioactive material contained within the rocks adjacent to the borehole. These rocks emit gamma rays with enough energy to get to the detector in the tool. GR log is used for correlation, lithologic identification, and as a shaliness indicator. This is because GR have a high affinity for radioactive mineral like potassium (K40), uranium (UR) and thorium (Th), which are contained in shale and would flag off as a high radioactive count on the log. In contrast, sands are characterized by low radioactive content, giving rise to low GR count. If the sources of the sediments are near-by granitic highlands, the sands and gravel may contain zircon or may be highly arkosic (high feldspar content), with high content of K40. The question in this case is whether or not the natural gamma ray log can be used as a sand/shale or reservoir/non reservoir discriminator and how it impacts on picking reservoir tops and bases for net pay calculation.
This paper presents an example of reservoir characterization of radioactive sands from the J5000 reservoir complex of the Bemu field, Niger Delta. It discusses the methodology applied using all available data in the field to fully characterise the reservoir. On the average, radioactive sands make up part of the upper 105ft of the J5000 reservoir complex that is further subdivided into two reservoir zones, J51 and J52, separated by intra-reservoir shale. These two zones form the majority of the productive interval in nearly all the existing 49 wells, with an average porosity of 24 and 26% respectively. Average permeability values of 900 and 1800 mD based on core data-derived equation.
Net pay criteria were determined by applying a cut-off to volume of shale (Vshale), generated from a combination of neutron and density log. These methods were further compared to the conventional method of Vshale from GR. Furthermore, Saturation height modelling generated from brine-oil cap-curves was performed which served as an input in calculating in-place hydrocarbon volumes.
The results from this study shows that an in-place volume of 114 and 280 MMstb for J51and J52 was achieved using a net-to-gross of 0.79 and 0.89 based on a cut-off on Vsh generated from a combination of Neutron and Density log. In comparison a net-to-gross of 0.47 and 0.46 were estimated by applying a cut-off to Vsh from GR, thus resulting to a lower in-place volume of 70.5 and 144 MMstb for J51 and J52 reservoirs respectively.
Novel Application of QuantiMin SQP Methodology for Improved Reservoir Characterization in a Deepwater Turbidite Field Development
Authors: Arogun Olubunmi , Nwokolo Christopher 
Published: August 2012

Abstract
The success of any green as well as mature field development planning and execution lies in the ability to recreate the environment of deposition with the appropriate spatial and temporal facies interdependencies. This, when done with proper application of the varied suite of geotechnical software/knowhow, often leads to the creation of a finite number of high resolution and equiprobable reservoir models within a macro and micro sedimentological framework, that readily lends itself to optimized risk and uncertainty management. This becomes even more critical in deepwater turbidite systems where the impact of geologic uncertainties can significantly reduce project value and does often prevent marginal field developments in the absence of a low cost tie-in option.
This paper presents the novel application of one such technique; the QuantiMin methodology approach improves aspects of reservoir characterization and facilitates various aspects of well and reservoir management in the waterflood development of a Miocene deepwater turbidite system in the Gulf of Guinea.
The QuantiMin technique is a sequential quadratic program that solves non-linear problems by series of quadratic programming steps. When applied in this context, it assesses the mineral and fluid content around the near wellbore area, based on their unique well log responses, and returns with a finite volume distribution of mineral and fluid distribution around the wellbore, using the mineral and fluid distribution input from appraisal well cores as the calibration or control variable.
The results from QuantiMin analysis have been used in this field to:
Evaluate the potential impact of mineralogy on the performance of water injection wells. Apply understanding of mineral types around the wellbore to the design of acid stimulation recipes. Develop a framework for understanding the field scale distribution of heterogeneities by establishing the interdependencies between log-scale QuantiMin and microscopic core petrography data, and hence facilitate high resolution reservoir characterization. Establish realistic flow potentials for development wells.
Effect of Cement Contamination on Some Properties of Drilling Mud
Authors: Joel O. F , Ndubuisi E. C , Ikeh L. 
Published: August 2012

ABSTRACT
Drilling of oil well is a capital intensive project; hence, the importance of selection of proper mud system that is free from contamination cannot be overemphasized. A poor design and contaminated drilling fluid can be very costly in the life of any well. Therefore, during drilling operations care must be taken to avoid contamination of mud with cement among others. This project details experimental work and findings associated with mud contamination with cement. Also, solutions were proffered on how to manage contaminated mud systems with cement during drilling operations. The result of this work will in no small way help not only the operators but Engineers to manage this concern with dispatch when it arises, thereby minimizing down time and associated costs which affect drilling operations negatively.
Predicting Wax Formation Using Artificial Neural Network
Authors: Adeyemi B. J , Sulaimon A. A 
Published: August 2012

Abstract
Wax formation is a problematic phenomenon in petroleum production operations especially in deep offshore fields. Wax begins to form when temperature falls below the cloud point of the oil as it travels from reservoir to surface lines. Wax deposition may lead to increased pumping power to maintain smooth flow, blockage of flow lines, production delay and even total abandonment of the entire flow line system. A reliable prediction of the onset conditions for wax formation is an important step towards prevention and mitigation of the resultant wax deposition.
Prediction of WAT by most of the existing models deviate from the experimental results due to simplifying assumptions. In this work, Artificial Neural Network (ANN) approach was used to predict the WAT for various hydrocarbon mixtures. The model was trained using different combinations thermodynamic properties of twelve different hydrocarbon fluids subsequently validated with experimental data. Results show that the ANN approach predicts the WAT more accurately than the existing models. The Average Absolute Deviations (AAD%) for the ANN are less than those of the existing models. A combination of molecular weight, density and activation energy as input parameters provided the best prediction.
Investigating the Effect of Electrolytes and Temperature on Rheological Properties of Jatropha Oil Based Mud
Authors: Fadairo A. S. , Tozunku K. S. , Kadiri T. M. , Falode O. A 
Published: August 2012

Abstract
Numerous studies have been carried out on diesel as base fluid in oil-based drilling fluids, and have concluded that diesel oil-based mud is highly environmentally unfriendly and expensive to dispose. One of the ways to avoid these problems while keeping the advantages of oil-based muds is to substitute diesel in muds with environmentally friendly oils, such as Jatropha oil.
This study examined the rheological properties of Jatropha oil based mud in the presence of sodium chloride and potassium chloride salts, and at increasing temperature of the muds. The results showed that salinity and temperature have negative effects on flow properties of oil-based drilling fluids. It also showed that jatropha oil based mud exhibits less adaptability than diesel oil based mud under high salinity and temperature condition, hence there is the need to improve the rheological properties of jatropha oil based mud under this condition. Finally it was revealed that Jatropha oil-based mud possesses great chances of being a technically viable replacement for Diesel oil-based mud.
Economic Investigation and Statistical Database Development for the Oil and Gas Industry
Authors: Dosunmu Adewale , Chimaroke Anyanwu , Evelyn Ekeinde , Oluwayomi Ogurinde , Paul Fekete 
Published: August 2012

Abstract
Nigeria's oil and gas industry is in its budding stage of development and thus requires high technological drive for growth and sustainability. Most operations done in the past have not been preceded by proper appraisal and review to ascertain if there might have been areas for optimization as well as improving on future operations. This has led to huge financial losses in oil business, of which Nigeria takes a substancial percenage of this loss.
In this work, areas of business operations where these losses can be mitigated are identified through thorough economic investigation. The investigations are conducted under professional consultancy services, whose inputs are technology based and reliable at all times.
In this investigation method, statistical data are developed that make history matches as well as identify regularly repeating trends in operations vivid. With the results from this analysis, new decisions can be made to better the outcome of future operations. Key areas for performance improvement are identified and optimized as well.
Finally a database of various findings is developed to properly document useful data for future purposes by consultants as well as industry professionals.
The Nigerian oil and gas business will benefit immensely from this project especially in management issues and in planning future business operations
Interference Tests Analyses of Horizontal and Vertical Well Combinations in a Reservoir Subject to Double-Edged Water Drive
Authors: Adewole E. S. 
Published: August 2012

Abstract
When a reservoir is subject to double-edged water drive mechanism, another well completion may be utilized to (1) intervene in an already watered-out well, for the purpose of optimizing oil production, (2) deliver material through one well to the other, or (3) strengthen confidence on earlier results of reservoir characterization. In all these applications, communication between the wells must not be in doubt. Procedures for analyzing interference tests data to determine the degree of communication between points in such a reservoir system is the main objective of this paper.
Source and Green's functions are utilized in deriving appropriate dimensionless pressure expressions for a reservoir, bounded laterally by double-edged water, and consisting of horizontal and vertical well combinations. To strengthen analyses, dimensionless pressure derivatives are computed from the dimensionless pressure expressions derived. As a late time flow test, external distances between wells are considered in the computations. Well combinations considered are (1) horizontal-vertical; (2) horizontal-horizontal and (3) vertical-vertical. Analytical expressions for analyzing interference test data for each well combination are derived, even if well functions are reversed to strengthen the validity of results.
Results show that, if the reservoir is isotropic, interference test duration should be less than water breakthrough time tDbr ≥ x2eD/Π2 for valid results. Flow time beyond this limit gives only an indication of the strength and responsiveness of the encroaching aquifer. Furthermore, analytical expressions for calculating fluid and reservoir properties depend on the type of well used as active well during the test. Horizontal well combinations would produce earlier interference than vertical-vertical well combinations, given the same anisotropy and rate history. An active horizontal well at interference produces variation of slopes on dimensionless pressures and their derivatives plots between early flow period and commencement of irreversible steady state, while a slope of 1.151 is observed for an active vertical well during the same period. In addition to type curve matching, parameter matching is required for estimating complete reservoir properties. Finally, time of occurrence of interference is directly proportional to area between interfering wells.
A Model Approach of Controlling Coning in Oil Rim Reservoirs
Authors: Onwukwe S. I , Obah B , Chukwu G. A. 
Published: August 2012

Abstract
Water and gas coning in oil rim reservoirs pose serious hindrance to optimizing oil production in the thin oil beds as unwanted fluids tend to replace the oil in the production stream. This invariably limits the ultimate oil recovery. In this study, Semi-Analytical models of estimating critical rate and optimum horizontal well placement was developed to control coning tendencies in oil rim reservoirs. The models was developed through semi-analytical analysis of applying the principle of Nodal analysis to graphically combine gas-oil reservoir system and oil-water reservoir system respectively; with a view to controlling gas and water coning phenomena in gas-oil-water reservoir system. The result was compared with an existing correlation with field data obtained from the Niger Delta oil field.
The models are simple for fast calculations for reservoirs with thin oil zones sandwiched between gas cap and bottom water. It is concluded that the developed models can be used as a tool to make a first pass assessment in the development of oil rim reservoirs anticipated to experience water and/or gas coning during production.
The Nigerian Marginal Field Initiative: Recent Developments
Authors: Adetoba Leye A. 
Published: August 2012

Abstract
The marginal field initiative has come to stay within the Nigerian oil industry since the signing of farm out agreements in 2003 between the multinational oil companies, the Nigerian National Petroleum Corporation and the indigenous companies.
Some challenges such as security of operations, funding, lack of technical know-how, Quota restriction, Lack of infrastructure, Collaboration, Fiscal terms & incentives, Inconsistency in government policies, Gas development, Non availability of rigs, Violation of agreement terms were earlier reported as affecting the progress of the initiative.
This paper discusses the recent updates in the industry as it affects the marginal field initiative especially the improvements and set backs on some of these earlier challenges and new challenges such as the PIB, the Nigerian content law and the call for another bid round.
A Flow Assurance Evaluation of Gas Storage in Depleted Reservoirs
Authors: Alim Chimereucheya N. , Tohidi Bahman 
Published: August 2012

Abstract
Global demand for gas is seasonal, mainly due to fluctuations in its demand at different times of the year. Due to this seasonal variation in demand, gas is often stored during the off-peak period and produced during the peak period.
However, one of the major challenges associated with gas storage in depleted reservoirs is salt precipitation around the wellbore. The dry gas in contact with connate water in the reservoir causes some of the connate water to evaporate to satisfy thermodynamic equilibrium and as a result, salt precipitates when the solubility product of the dissolved ions is exceeded. This deposition of salt potentially leads to pore throats plugging, hence a reduction in the original properties of the reservoir such as porosity, permeability etc over time.
Conventional reservoir simulators do not take this dynamic change in the reservoir properties into account, which leads to inaccurate estimation of the reservoir performance over time. This also results in wrong estimation of the amount of chemical inhibitors required to mitigate flow assurance problems such as gas hydrates, corrosion, scales etc.
This study shows that these changes in the reservoir parameters have an effect on the prediction of conventional models. Hence, reservoir performance should be monitored during the entire field life and the injection/ production data obtained from one cycle should be used to re-define the main reservoir parameters and refine the model for successive cycles.
This study proposes a method of modelling the reservoir performance by taking into account the changes in reservoir and fluid properties over time. It also proposes that in the long term, commercial simulators should be integrated to account for changes in reservoir and fluid properties over time in order to obtain better predictions of reservoir performance.
Surgical treatment modality for facial esthetics in an obstructive sleep apnea patient with protrusive upper lip and acute nasolabial angle
Authors: Ahn Hyo-Won , Cho Il-Sik , Cho Keun-Chul , Choi Jin-Young , Chung Jin-Woo , Baek Seung-Hak 
Published: August 2012

ABSTRACT
For patients with severe obstructive sleep apnea syndrome (OSAS), maxillomandibular advancement (MMA) offers a good treatment option by physically expanding the skeletal framework. However, facial esthetics can be aggravated by MMA in patients with OSAS who have a normally positioned maxilla, a protrusive upper lip, and an acute nasolabial angle. Therefore, surgical treatment planning should be customized according to diverse skeletodental and soft-tissue patterns to produce a favorable change in facial esthetics and sleep function in patients with OSAS. In this case report, good treatment results were achieved in a young female patient with OSAS and skeletal Class II, a normally positioned maxilla, a protrusive upper lip, and acute nasolabial angle by impaction of the maxilla, autorotation/advancement of the mandible, and advancement of the chin. A customized flowchart for surgical treatment planning in OSAS that considers facial esthetics was suggested.
On local convexity of nonlinear mappings between Banach spaces
Authors: Banakh Iryna , Banakh Taras , Plichko Anatolij , Prykarpatsky Anatoliy 
Published: August 2012

Abstract
We find conditions for a smooth nonlinear map f: U → V between open subsets of Hilbert or Banach spaces to be locally convex in the sense that for some c and each positive ɛ < c the image f(B
ɛ(x)) of each ɛ-ball B
ɛ(x) ⊂ U is convex. We give a lower bound on c via the second order Lipschitz constant Lip2(f), the Lipschitz-open constant Lipo(f) of f, and the 2-convexity number conv2(X) of the Banach space X.
Delamination of impacted composite structures by cohesive zone interface elements and tiebreak contact
Authors: Dogan Fatih , Hadavinia Homayoun , Donchev Todor , Bhonge Prasannakumar 
Published: August 2012

Abstract
Maximising impact protection of fibre reinforced plastic (FRP) laminated composite structures and predicting and preventing the negative effects of impact on these structures are paramount design criteria for ground and space vehicles. In this paper the low velocity impact response of these structures will be investigated. The current work is based on the application of explicit finite element software for modelling the behaviour of laminated composite plates under low velocity impact loading and it explores the impact, post impact and failure of these structures. Three models, namely thick shell elements with cohesive interface, solid elements with cohesive interface, and thin shell elements with tiebreak contact, were all developed in the explicit nonlinear finite element code LS-DYNA. The FEA results in terms of force and energy are validated with experimental studies in the literature. The numerical results are utilized in providing guidelines for modelling and impact simulation of FRP laminated composites, and recommendations are provided in terms of modelling and simulation parameters such as element size, number of shell sub-laminates, and contact stiffness scale factors.