bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Characterization of a Tetracopper(II) Complex Having a [Cu4(µ4-O)] Framework Stabilized by the Tetranucleating Macrocyclic Ligand
Authors: Miyazato Yuji , Asato Eiji , Ohba Masaaki , Wada Tohru 
Published: August 2012

Abstract
A tetranucleating macrocyclic ligand bearing four acetate pendants, L6−, was newly yielded by a stepwise synthesis from [Zn4(L′)(AcO)2(OH)2](ClO4)2·H2O (1), which was prepared from [2 + 2] Schiff-base condensation of 2,6-diformyl-4-methylphenol and 1,2-bis(2-aminoethoxy)ethane in the presence of Zn(ClO4)2·6H2O, sodium acetate, and triethylamine. A µ4-oxo tetracopper(II) complex [Cu4(L)(µ4-O)]·H2O (2) was obtained from the reaction of Cu(ClO4)2·6H2O and Na2H4L in methanol under basic conditions, and characterized by X-ray crystallography. Two adjacent copper centers were bridged by the phenoxo oxygen of L6− to form [Cu2(µ-OPh)] unit, two pairs of which were further linked by an oxo anion with a distorted tetrahedral geometry, finally creating a tetracopper core [{Cu2(µ-OPh)}2(µ4-O)]. Cryomagnetic measurements of 2 in the range of 2–300 K exhibited antiferromagentic behavior. Magnetic analysis of 2 was carried out by the four spin-exchange interactions model based on the bridging mode and the Cu–(µ4-O)–Cu angles, JA: Cu1/Cu4, JB: Cu2/Cu3, JC: Cu1/Cu2 and Cu3/Cu4, and JD: Cu1/Cu3 and Cu2/Cu4 pairs. The estimated four magnetic exchange interactions (JA, JB, JC, and JD) were −17, −161, −108, and −109 cm−1, respectively.
Synthesis, Characterization, and Small Hydrocarbon Encapsulation of Dicavitand-Porphyrins
Authors: Nakazawa Jun , Hagiwara Jun , Shimazaki Yuichi , Tani Fumito , Naruta Yoshinori 
Published: August 2012

Abstract
New host molecules “Dicavitand-Porphyrins” [H2C2P(syn,syn) (3), H2C2P(syn,anti) (4)] with small cavities on one or both sides of the porphyrin plane were synthesized from 5,10-bis(2,6-dihydroxyphenyl)-15,20-diphenylporphyrin and bis(chloromethyl)cavitand in 15 and 34% yield, respectively. Similarity of guest size selectivity of the host 4 in comparison with the reported “Cavitand-porphyrin” [H2CP(syn) (1)] suggests that these hosts have the same cavity size. The 1:1 and 1:2 association constants (K11 and K12) of the guest encapsulations into 3 were also obtained by 1H NMR titration and nonlinear least square fittings. The guest size dependences of K11 and K12 values of 3 show that the initial cavity prefers larger guests such as ethane, while the second one does not. The induced-fit type very small structural changes (estimated within 1 Å) upon first guest encapsulation of the host 3 affects the guest encapsulation of the other cavity through the covalent linkages.
The Numerical Approach for Predicting Productivity from Mutiple-fractured Horizontal Wells under Non-Darcy Conditions
Authors: Feng Yang , Ning Zhengfu , Liao Xinwei , Liu Huiqing 
Published: August 2012

Abstract
Horizontal wells with multiple fractures are becoming more prevalent in tight gas reservoir. However, it is uneasy to obtain the applicable deliverability formula of multiple-fractured horizontal wells using analytical method in consideration of multiple factors, such as the non-Darcy effect, interference between fractures, the coupling effect with reservoir, and formation heterogeneity.
This project investigates the deliverability formula of multiple hydraulically fractured horizontal wells in tight gas reservoir using a special numerical method with a focus on the existence of non-Darcy effect and formation heterogeneity. Numerical model expected from daily production data, including wellhead pressure history and production history, is obtained using the numerical well test method, which has an advantage in considering reservoir heterogeneity and complex boundary. The effect of non-Darcy in gas well is discussed using rate dependent skin when constructing the numerical model. The parameters of the numerical model on multiple fractured horizontal well are validated compared with analysis of real pressure build-up well test data. Productivity well test is then simulated based on the previous numerical model, and binomial deliverability equation is obtained from simulated productivity well test curve. The error of absolutely flow rate which derives from the simulation results and modified isochronal test from the field is less than 6%. This paper provides a fast and reliable numerical tool to multifractured horizontal well performance prediction in tight gas reservoir, especially considering non-Darcy effect and reservoir heterogeneous.
Casing ERD Wells to Target the New Improved Casing Flotation - A New Solution
Authors: Uzokwe F.C. 
Published: August 2012

Abstract
Getting casing to total depth is one of the most important operation in extended reach drilling (ERD) as increased casing depth increases recovery efficiency hence the need to ensure as much casing as possible is deployed into the wellbore. This paper proposes a new method of casing deployment in ERD wells termed New Improved Casing Flotation (NICF). This method is based on the principle of buoyancy and utilizes multiple fluids to deploy different sections of the casing string into the wellbore. This proposed method is validated using a base case extended reach well and the maximum measured depth attained for the 95/8?? production casing compared against other casing installation techniques. From the result of the simulation, the measured depth attained using the NICF method is 29,400 ft. When compared to partial flotation (23,300 ft), full flotation (12,300 ft) and conventional method (12,300 ft), the measured depth obtained using the proposed NICF method exceed that of partial flotation by 6,100 ft, and that of conventional method and full flotation by 17,100 ft.
Introduction
The need to get hydrocarbons from ultra deep and complex wells have indeed pushed the limits of well engineering. Critical technologies have led to the advent of rotary steerable systems (RSS) and steerable motors assemblies which have enabled drilling with controlled dog legs thereby minimizing drag as the BHA proceeds through its complex trajectory (Thomas et al 2008).
The development and use of low torque drill pipes, specialty equipments like NRDPP, DSTR subs, DPB subs, bi-directional rollers, lubricating beads, spot pills and hard banding of tool joints have all proved to reduce the effect of torque and drag thereby extending the limit of drilling in their different applications (Rae, Williams and Hamilton 2003).
It becomes obvious that these successes in drilling have to be complimented by successful casing running to total depth (TD) to enhance optimum production from the reservoir. These have led to great advances in the subject of casing design and running techniques. The onus being to develop casing running techniques that can match up the advances of complex drilling as well as being able to withstand all design loads and operational constraints in the most cost effective way (Jaffe et al 1997).
Accurate Estimation of Equivalent Circulating Density During High Pressure High Temperature (HPHT) Drilling Operations
Authors: Ataga E. , Ogbonna Joel 
Published: August 2012

Abstract
Error in equivalent circulating density estimation can be disastrous because of the narrow margin between pore and fracture pressure in HPHT wells. High temperature conditions cause the fluid in the wellbore to expand, while high pressure conditions in deep wells cause fluid compression. Failure to take these two opposing effects into account can lead to errors in the estimation of bottom-hole pressure on the magnitude of hundreds of psi. This study involves the development of a simulator called HPHT-Density Simulator to simulate the wellbore(drillpipe and annulus) during circulation as well as the temperature and pressure profiles of a wellbore during circulation.
A Bingham plastic model was incorporated into a simulator called HPHT-density Simulator which was developed using Visual Basic to simulate the wellbore during circulation. The developed HPHT-density Simulator program interface is executed with a series of user forms, which will accept data pertaining to the wellbore, drilling fluid and formation parameters and return the temperature profiles in the wellbore and formation, pressure losses in the wellbore and ECD of the circulating fluid. The user can navigate between forms and input data at leisure using the "back" and "next" input bottons. Once values of all the necessary parameters have been entered into the program, the results are displayed on a "results" forms.
The successful simulation of HPHT-Density Simulator shows a significant difference in the equivalent circulating density and bottom hole pressure profile for fluid circulation parameters of a Niger Delta well when the rheological properties were assumed to be constant as compared with when temperature-pressure varied. This can be adapted to drilling operations and thereby preventing downtime arising from kicks, blow-outs, lost circulation and formation damage due to wrong estimation of equivalent circulating density while drilling within narrow margin between pore and fracture pressure in HPHT wells.
Selection of Alternatives for Oil Field Development; Nonlinear Optimization Approach
Authors: Ohia N. P , Omeke J. E. , Achumba I. G 
Published: August 2012

Abstract
In the petroleum Industry, the major task is to develop a strategy to maximize the hydrocarbon production within existing physical and economic constrains. The major entities involved in solving this problem are: the oil reservoir and the oil wells. Each of these entities has a number of variables and parameters. Searching for the best configuration of these parameters, for optimum return on investment, constitute an optimization problem. In other to apply the optimization approach, an objective function must be involved. In this study, Net Present Value (NPV) was selected as the profit indicator for return on investment (ROI).
Optimization is complicated when more parameters are involved and needed to be optimized simultaneously. Major success will rely on the ability to incorporate effectively, factors (physical and economic) that influence the entire production process in an economic model called the Objective function with or without constraints. A suitable optimization method is also required.
In this work, a robust NPV objective function was developed for a reservoir under production. Reservoir, production and economic uncertainties where fully captured.
A multivariate nonlinear optimization approach was employed in determining the best configuration of the decision variable and their effect on NPV. Nonlinear optimization methods based on Newton's technique locate the extrema by approximating the objective function with a nonlinear quadratic model. The quadratic model is solved for the stationary point where its gradient goes to zero. If the quadratic model is a good approximation of the objective function, then the stationary point of the quadratic model should be near a stationary point of the objective function. The stationary point of the quadratic model is taken as the new estimate of the objective function's stationary point and the process is repeated until some form of convergence criteria is satisfied.
Sensitivity plots where generated for diagnostic purposes as well as to strengthen decision processes. Field application of the NPV model was carried out and reliable results where obtain.
Pipeline Vandalism in Nigeria: Recommended Best Practice of Checking the Menace
Authors: Udofia O. O , Joel O. F 
Published: August 2012

Abstract
Pipeline vandalism, in the context of this paper, refers to the willful or deliberate act of damaging petroleum pipelines with the sole aim of stealing crude oil and associated petroleum products. In the Nigerian oil & gas industry, the effects of pipeline vandalism among others include huge economic losses from pipeline & plant shutdown, environmental pollution, fire outbreaks usually resulting in loss of lives. Scarcity & shortage of petroleum products as well as decrease in electricity supply with the attendant socio-economic problems can also be attributed to pipeline vandalism. In Nigeria petroleum and associated products are transported through extensive network of pipelines that run across different locations throughout the country from remote to populated areas. These pipelines are however poorly secured thereby making them targets of repetitive attacks by vandals. Various steps have been taken by government for efficient service delivery but the problems appear to be on the increase. This paper presents an overview of the existing arrangement of pipeline monitoring protocols and recommended Best Practice for prudent pipeline management in Nigeria.
A New Analytical Method for Predicting Dew Point Pressures for Gas Condensate Reservoirs
Authors: Godwin Okpo Nnadozie 
Published: August 2012

Abstract
This study presents a new analytical method for predicting dew point pressures for gas condensate reservoir as a function of routinely measured gas analysis and reservoir temperature. The proposed model was developed using experimentally measured and collected data of 259 gas condensate sample covering a wide range of gas properties and reservoir temperatures obtained from the literature. The proposed correlation has an average relative deviation (ARD) of 0.0488% and absolute deviation (AAD) of 0.099%.
The accuracy of this model was tested with 14 data sets that were not used in developing the correlation, and the accuracy of the new model was compared to order existing correlations from the literature. The result shows that the newly proposed model performed better than popular, and presently being used in the oil and gas industry such as the Nemeth and Kennedy, and A.M. El-sharkawy correlations.
Well Predictive Material Balance Evaluation: A Quick Tool for Reservoir Performance Analysis
Authors: Nwaokorie Chukwuemeka , Ukauku Ikwan 
Published: August 2012

Abstract
Hydrocarbon reservoirs require steady evaluation in terms of performance prediction and resource volume estimation. These evaluations are planned and carried out from point of discovery till maturation and abandonment.
Full field reservoir simulation model is the conventional tool for reservoir performance analysis via planned or existing wells. Material balance models were developed to carry out simple reservoir analysis on tank basis for resource volume estimation and prediction.
Well predictive material balance model has proved to be a quick and handy tool capable of doing reservoir analysis both at reservoir and well levels. In this paper, we will be discussing the methodologies, basic workflows and technical principles of building a simple well predictive material balance model. This tool is not a replacement of more robust reservoir simulation model but a quick win in terms of time and cost.
The study shows the implementation of this tool for a resource volume estimation and well performance prediction. It covered evaluation of saturated reservoirs with concurrent oil and gas production.
The results were compared with reservoir simulation and conventional decline curve analysis results for robustness check. Important data such as relative permeability, well models (IPR and vertical lift curves), current fluid contact and PVT data are some of the essential data required to build a good predictive material balance model.
Keys steps taken in building this model are:
Data gathering and validations Model Construction History Matching/ Simulation Prediction (reservoir and well) Result analys
The Results show good comparison with other methodologies (Simulation and DCA). The wells predictions were good and compare closely with actual well production.
Comparative Performance Analysis of Petroleum Sharing Contracts in Angola, Equatorial Guinea, Gabon And Nigeria
Authors: Echendu Joseph C. , Iledare Omowumi O. , Onwuka Emmanuel I. 
Published: August 2012

Abstract
Petroleum Fiscal System (PFS) is a key determinant of investment decision in the exploration and production (E&P) of oil and gas. It describes the relationship between the host governments, the investors, and community stakeholders with respect to how costs are recovered and profits are shared equitably. A comparative economics of the performance of fiscal regimes becomes imperative as it affects stakeholders in making informed decisions on the oil and gas business investments worldwides.
This paper evaluates the structure, conduct and performance of PFS in Gabon, Equatorial Guinea, Angola and Nigeria in the Gulf of Guinea (GOG). These countries hold about 90% of the GOG proved reserves. Economic analysis of the same E&P phases using hypothetical field and cost data under the different PFS are presented and discussed for comparative PFS performance evaluations. Comparison of the effects of production delay, front loaded government take and taxation shows that petroleum sharing contract fiscal terms and instruments in Gabon, Equatorial Guinea, Angola and Nigeria are relatively competitive. We found that as the risk in deepwater investment increases with water depth, return on investment rises in these GOG countries. Monte Carlo simulation process incorporated to account for risk and uncertainties reveal early discounted payout for investors in these GOG countries with significant degree of ceteris paribus.
Improving Efficiency of Oil & Gas Development through Lean Concept
Authors: Mustapha Adetoun , Ageh Ebenezer , Maduekwe Emeka , Ojulari Bayo 
Published: August 2012

Abstract
Population and economy are two key factors considered in global energy demand projections. With rapidly growing world population, energy security is a global concern. The 2011 World Energy Outlook projected that from the 2010 levels, global oil demand will grow by 14% while gas use will rise by more than 50% as well as account for over 25% of world energy demand by 2035. With hydrocarbons no longer easily accessible, success in the future of oil and gas will require meeting various challenges, including ensuring that both discovered and new resources can be produced in economically and environmentally sound manner to offset the natural field decline. Also, shareholders, non-government organizations and local communities are seeking for more value and demonstration of social responsibilities from the industry. Additionally, governments and policymakers are imposing stricter regulations that impact reserve maturation and production.
One of the ways stakeholders' expectations can be addressed is by making the most use of resources to lower costs and improve operational efficiency. Lean is a business improvement technique with a collection of tools to eliminate ‘'waste" in an operation and reduce cycle time. Cost reduction is achieved by improving the flow of material and information through the system and continuously finding ways to reduce the amount of work by taking out unnecessary or "waste" steps in processes. Originally developed by the Japanese automobile company, Toyota and widely employed in the manufacturing industry, more industries are adopting the Lean concept.
This presentation will showcase Lean application in hydrocarbon development and production. Case studies will be provided to demonstrate how Lean implementation has helped and can be used to eliminate wastes in processes and bring about a culture change. Business results are faster hydrocarbon maturation, enhanced production, sustainable cost reduction and stakeholders reaching mutual agreement faster on sustainable development/environmental issues.
Minimum Shut-In Time Prediction Model for Pressure Build-Up Survey for a Niger Delta Onshore Field
Authors: Ejere Ekeoma , Omeke James Emeka 
Published: August 2012

Abstract
Allowing a well to stabilise is an important part of both pressure drawdown and build-up test. If stabilization is overlooked or is impossible, standard data analysis techniques may provide erroneous information about the formation. One of the principal objectives of pressure build-up analysis is to determine the static reservoir pressure without waiting weeks for the pressure in the entire reservoir to stabilize. The fact remains that no matter how we try to avoid long shut-in period, the shut-in time must exceed the transient and well bore storage period if a reliable result is sought. The bulk of the analysis is done at the middle transient period (MTP) which, sometimes, due to the complex nature of the reservoir, may be appreciable enough to invalidate the intention of shutting-in the well for just a short time. A minimum shut in time of six hours has been a common conventional practice in our land locations. This brings us to the question - "is this shut-in period enough or too small to provide a reliable analysis?" This shut-in period remains a paradox as long as complexities and uncertainties are present in the reservoir under study. Some reservoir with varying degree of complexities has varying shut in time. For example, the presence of faults and complex barriers may prolong the time of the reservoir to reach its middle or late transient state during build-up; hence, it becomes necessary to predict the minimum time of stabilization in the presence of these complexities so as to minimize cost. This was the focus of this paper.
The general formulas used in analyzing pressure build-up data came from a solution of the diffusivity equation with homogenous, isotropic and slightly compressible single phase fluid conditions. This equation is in its simplest form and due to the assumptions made; it is obvious that the major uncertainties that may affect the shut in time is not captured; hence a need for a robust modelling.
In this paper, a semi-analytical model for the Niger Delta onshore field was developed for optimum shut in time prediction for each well in the reservoir selected for study. A correction function which encapsulates the real reservoir complexities was introduced based on the well data under study. This correction function was modelled using Gompertz, 4 parameter Sigmoidal equation1 with the correlating constant determined by the method of least square for the specific well considered. A constrained nonlinear optimisation technique was applied to the newly developed model which serves as the objective function with the aim of minimizing the shut-in time as well as attaining an effective stabilization pressure. This procedure will, in no doubt, improve our optimism of accurate shut-in time prediction, a cost effective approach.
Evaluation of Thermal Effects on Drillability in HPHT Wells in Niger Delta
Authors: Ngwu G. I. , Dosunmu A. , Osokogwu U. 
Published: August 2012

Abstract
Overcoming wellbore drilling instability presents one of the major challenges to drilling engineers mostly in high pressure and high temperature wells. These are wells with reservoir pressure in excess of 10,000 psi and bottom-hole temperature exceeding 300°F, the temperature gradient between the drilling mud and the formation leads to induced thermal stresses and pore pressure responses. The aim of this work is to design an optimum mud weight at different depths and investigate the effect of temperature on wellbore stresses as it affects drillability performance. Improper mud design is one of the major causes of instability problems and also increasing temperature of the mud leads to increase in wellbore stresses which enhances the likelihood of breakouts and inhibits tensile fracture formation, and on the other hand, cooling the mud inhibits breakouts and which increases the likelihood of development of tensile wall fractures. A model was developed in this work, which was used to analyze the thermal effects on wellbore stresses and the optimum mud weight at different depth as it affect drillabilty performance. Analyses reveal that at bottom hole temperature of 300°F, the tangential stress was 7,378psi at the depth of 10,000ft. when the temperature increased to 438°F, the tangential stress was 10,025psi at the depth of 16,000ft for shale formation.