bluuebunny/crossref_metadata_2025 huggingface dataset:
Sand Management Methodologies for Sustained Facilities Operations
Authors: Rawlins C. Hank
Published: April 2013

Facilities sand management is tasked with the goal of ensuring sustained hydrocarbon production when particulate solids (i.e. sand or proppant) are present in well fluids, while minimizing the impact of these produced solids on surface equipment. Particle size and total concentration of formation sand or proppant determines their net effect on production and the resulting operability of surface facilities. Conventional sand management control focuses on sand exclusion from the wellbore, either by production limits or completion design. Completions may adversely affect inflow due to skin buildup and both controls impede maximum hydrocarbon production. Alternatively, co-production of fluids and solids, with subsequent sand handling at surface facilities, is an inclusion paradigm that allows sustained hydrocarbon production. Produced solids are removed at the wellhead upstream of the choke using fit-for-purpose equipment. This methodology allows for increased or recovered hydrocarbon production, while their removal upstream of the choke protects facilities operations.

A description of the design, performance, operation, and effect on production rate is provided for sand inclusive production through application examples in the Caspian Sea, Indonesia, and South China Sea. Specific reference is given towards wellhead desanding, which forms the greater part of this approach, and has expanded from the first field installation in 1995 in the UK to every major oilfield producing region. Implementation of dedicated facilities sand management technology has resulted in increased hydrocarbon production from sand producing wells, extension of well life on marginal fields, and re-start of shut in wells.
Formation Silicate Scale Inhibition during Alkaline Flooding: Static Model
Authors: Basbar Ashraf E. , Elraies Khaled A. , Osgouei Reza E.
Published: April 2013

Scanning electron microscopy (SEM), X-RAY diffraction (XRD) and X-RAY Fluorescence (XRF) were employed to investigate the silicate scale during alkaline flooding. The formation of silicate scale is a multi-step process, involving silica dissolution, silica polymerization, and precipitation with other ions. It is a massive headache burdened to the oil and gas industry today. The aim of this study is to come out with a static model based on series of experiments to investigate the silicate dissolution ratio using quartz sand core samples. Synthetic brine with different salinities ranged from 5,000 ppm to 60,000 ppm and different alkali concentrations ranged from 0.4% to 1.2% were utilized to determine the change in soluble silica concentrations. In addition, two inhibitors; namely, Boric acid (BA) and Ploy Acrylic Acid (PAA) were screened and the optimum concentration for each inhibitor was identified. Based on the results from this experimental work, the silica dissolution ratio increased significantly with the increase in the the alkali concentration. The silica dissolution ratio increased from 1.1% at 0.4% alkali concentration to 4.6% with alkali concentration of 1.2 %. By introducing BA and PAA as inhibitors separately, significant improvement was observed in both cases. Using 50 mg/l of BA and PAA, 3.1% and 11.2% of the dissolved silica was inhibited, respectively. However, only 37.2% was inhibited when the BA concentration was increased to 350 mg/l, while 72% of the dissolved silica was inhibited when 350mg/l of PAA was utilized. The outcome from this research indicates that the best inhibitor does not prevent the silicate scale, but it might reduce it. This study may assist in understanding the mechanism of silica dissolution process and its effect against alkaline flooding.
Improving Production Using a Unique Self-Positioning Tool to Deliver Four Types of Acid Stimulations in a Well: Matrix Penetration, Acid Washing, Many Micro/Mini Fractures, and Large Fractures
Authors: Surjaatmadja Jim B. , AL Hamad Abdullah M. , Waheed Arshad
Published: April 2013

The use of coiled tubing (CT) to distribute acid for stimulation has shown good results in the past. Use of CT allows the acid to be delivered evenly throughout the well. This is especially true for openhole wells in which bullheading acid into it will only acidize the heel of the well. While often used, such approaches will create massive enlargements at the entry point where the acid first contacts the acid soluble rock, causing ineffective treatments and re-entry issues. Wellbore collapse often follows. The use of CT as a pinpoint delivery method is therefore preferred.

An even better approach with CT is to add a jetting tool to the bottomhole assembly (BHA). With this configuration, it is an option for different treatments that can be completed in a single trip, such as simple matrix acidizing, acid wash, or even hydrajet assisted acid fracturing (HJAAF). This latter one can be used to place many microfractures or minifractures in the well; and by increasing the bottomhole pressure with annular injection, the HJAAF can create medium to very large fractures for sustained productivity.

This paper discusses the implementation of this combined process in the Middle East. The wells in the discussions have large openhole sections to be stimulated. Moreover, as often found in the brownfields, a small production tubing that has been weakened by corrosion and erosion is present and cannot be removed for many reasons, such as losing the well and related costs. The CT and associated tools in such cases must therefore be very small to enter through this tubing and its associated "no-go" restrictions. A small OD unique jetting mechanism that places the jet nozzles closer to the wellbore wall was therefore necessary to perform this task. Excellent results were obtained using this process and are presented in this paper.
High Resolution Seismic Imaging and Fault Detection using Walkabove and Rig VSPs in Ras Budran and Ras Fanar Fields in The Gulf of Suez
Authors: El-Hateel Mohamed S. , Ahmad Parvez , Ismail Ahmed H. , Ashraf Ahmed , El-Fadeel Mohamed A.
Published: April 2013

The Gulf of Suez is well known for complex geological setting due to salt plays, complex faulting, high dips etc. Surface seismic is typically affected by strong multiple activity and heavy energy losses resulting in low resolution seismic, making the seismic imaging a big challenge for Geophysicists. Consequently, the geophysicists face problems while planning and drilling new development wells due to unexpected events i.e. faults, missing targets etc. Suez Oil Company conducted standard rigside borehole seismic surveys to address some of the seismic issues in their concessions. Such surveys also resulted in uncertainties in time-depth relation and poor imaging even in wells with low inclination.

The paper presents case studies where VSP surveys were conducted in Zero Offset geometry in vertical and Walkabove in low and highly deviated well sections in Ras Budran and Ras Fanar offshore fields. VSP programs were designed after pre-survey modeling simulating different scenarios to meet the objectives as well as ensuring safety and cost effectiveness. Accurate time-depth relations were derived in wells with low as well as high inclination. Three-component full waveform data were processed leading to high resolution 2D images beneath the deviated well trajectories. The results helped in reducing surface seismic uncertainties for shallow as well as deep targets, and refining interpretation. Additionally, VSP image helped to control the structural boundary as new faults were delineated successfully, which were not detected in low resolution 3D surface seismic.
Non-intrusive Corrosion Erosion Monitoring For Subsea Applications
Authors: Instanes G.. , Kristiansen S. H. , Pedersen A. O.
Published: April 2013

The oil and gas industry has a need for reliable monitoring of changes in wall thickness both topside and subsea. It is important to detect and monitor the effect of corrosion and erosion as this may reduce the life-cycle cost and increase the lifetime of industrial infrastructure, ships, aircrafts, ground vehicles, pipelines, oil installations, etc. Even topside the conditions of operation can be extremely hostile, facing problems like surface roughness, fluid loading issues, temperature variations, and a host of other factors that make development of a robust wall thickness assessment tool a challenging task. Deploying a monitoring system subsea makes the application even more demanding when you have to take into account factors like high pressure and limited access. Over the last years ClampOn have offered a topside corrosion-erosion monitor (CEM) for monitoring changes in the wall thickness of such infrastructure. Major advantages of this technology have been its non-invasiveness, high repeatability, high coverage and the lack of any transducer movement, also making it an excellent candidate for subsea use. The measurement principle is based on dispersion of ultrasonic guided wave modes, and by using electromagnetism these waves can be transmitted through the pipe wall without the sensor being in direct contact with the metallic surface. It is installed on the outer pipe wall to produce real-time wall thickness information – not as a spot measurement, but as a unique average path-wall thickness. With several successful installations topside, the technology has now also been made available for subsea installation.
Dual ESP as a Solution for Cross-flow Challenges. Case Study, Well A-06, Muglad Basin, Sudan
Authors: Fadl Abdalla Tajeldin , Ahmed Ahmed Elrufai , Osman Younis Mohd , Abdelrahman Hatim Muhallab
Published: April 2013

Field H has several wells producing commingled with different pressure regimes. PLT runs have been carried to assess the layer-wise pressure and fluid contribution. The results revealed the problem of cross-flow in shut-in condition between the two producing reservoirs in well A-06 among other wells. The PLT also confirmed there is no contribution from lower pressure zone alongside the high pressure zone even in the highest drawdown. In such case commingled production by single ESP will not be optimized and alternatively, one zone must be isolated and production from that layer is sacrificed. This situation mandates quest for a solution that offer total separation of production from each layer. In search for a solution to the problem the Dual ESP application was explored. Dual ESP technology can be used to separate production from two zones of the well where commingled production is not possible. Several Dual ESP configurations were explored and opt for the concentric configuration. Installation of Dual ESP in well A-06 provided solution to enhance oil production from multiple layers where commingled production is not possible. This paper discusses the application of Dual ESP in well A-06 as a case study and shows the valuable results achieved and the way forward.
Optimization Of Horizontal Well Length: A Case Study In The Fractured Basement Reservoir Of The South-east Dragon Oil Field In Viet Nam.
Authors: Lu Vi Dinh , Nguyen Quy Minh , Mai Lan Cao , Tran Dao Xuan
Published: April 2013

After several discoveries of oil and gas in fractured basement reservoir such as White Tiger, Dragon, Aurora and Ruby in 1990s, the basement on the continental shelf of Vietnam has become a major target for domestic and foreign oil companies. Oil produced from basement is accounted for more than 90% of the total produced oil. Due to lesser and lesser new discoveries and most of the big oil fields are in declining phase, the Improved Oil Recovery (IOR) methods are bringing advanced technological solutions to boost oil recovery from mature fields, geologically complex low permeable and fractured reservoirs in the future. Among the IOR techniques, horizontal wells appeared to be a promising one in both short and long term of reservoir life.

Horizontal well (HW) has a higher productivity and pay contact as increase the length of well, thereby reducing the number of wells required to drain the reservoir. In the case study presented, the efficiency of horizontal well will be evaluated by analyzing horizontal well performance. Both analytical and numerical solutions will be investigated. A 3D numerical model of the South-East Dragon field was set up with five production wells and one injection well that is known as a base case. Then running base case is to find the appropriate places for putting new well. Ten interesting scenarios are presented in this paper where the horizontal well is analysised both HW location sensitivities and HW length sensitivities. In addition, this research described a step-by-step procedure that can be used when performing an economic analysis of a horizontal well project. The results from the case study indicate that a combination of factors including total economic, analytical and numerical simulation is required to optimum horizontal well length in the fractured basement reservoir of South-East Dragon oil field in Viet Nam.
Hydraulic Unit Estimation From Predicted Permeability and Porosity Using Artificial Intelligence Techniques
Authors: Shujath Ali Syed , Hossain M. Enamul , Hassan Md. Rafiul , Abdulraheem Abdulazeez
Published: April 2013

Rock classification or assigning a type or class to a specific rock sample based on petrophysical characteristics is a fundamental technique to reduce the uncertainty in prediction of reservoir properties due to heterogeneity. One of the popular approaches is to classify a reservoir rock from the fundamentals of geology and the physics of flow at pore network scale. In this approach, rocks of similar fluid conductivity are identified and grouped into classes. Each grouping is referred to as a hydraulic flow unit (HU). HUs are estimated for the uncored section of the wells from wire line log data received from field using three popular artificial intelligence (AI) techniques such as (i) Adaptive Network Fuzzy Inference Systems (ANFIS); (ii) Functional Networks; and (iii) Support Vector Machines. HUs can either be predicted directly from wire line log data as a classification model or can be estimated indirectly from predicted permeability and porosity. In the present study, HUs were predicted employing both approaches. The comparison of the two approaches shows that it is a better practice to estimate HUs by directly relating them to well logs. Calculation of HUs from predicted permeability and porosity results in inferior accuracy. This is due to the accumulation of errors during the estimation of permeability and porosity. The Knowledge of HUs acquired from well logs can significantly help in determining ultimate hydrocarbon recovery, optimal well placement, and well stimulation. Thus, the finding of this research will impact the economy of the development and operations of a field.
Enhancing Oil Recovery through High Level Data Mining Technology
Authors: Adeyemi B. J. , Ajilo V. I. , Falode O. A. , Falobi E. O.
Published: April 2013

The world's energy consumption has risen geometrically over the last three decades due to advancement in technology. In response to this ever increasing rising demand, other sources of energy have been explored. Reports show that fossil fuels (crude oil and natural gas) continue to take the lead despite these efforts. Hence, the Oil and Gas industry has put in a lot of technical measures to meet up with this high energy demand. Many works have been done on how to increase reserves and ultimately increase recovery but little has been achieved in this area. Therefore, a more reliable, efficient and effective way of enhancing recovery is necessary to make headway in countering this challenge. This research seeks to provide the feasibility of enhanced oil recovery (EOR) projects using high level data mining technology in the African Oil Producing Regions.

Data mining is a process which finds useful patterns from large amount of data. Data analysis process involves data exploration, pattern identification and pattern deployment to make accurate judgement necessary for EOR investment decisions. It provides a significant reduction in the level of uncertainty when compared with other existing techniques. In our concept, artificial intelligence and genetic algorithm was employed and recommendation made.

Results show that data mining technique is a robust tool for making EOR investment decisions, right from the early life of a field. Thus, this concept makes it more economical to execute EOR projects with lower level of uncertainties. Marginal fields can also be invested upon using data mining techniques.
Polymer-Locked, Crush-Free Wireline composite Cables Reduce Tool Sticking and HSE Risk in Emerging Deepwater Reservoirs
Authors: Sarian Serko , Varkey Joseph , Protasov Vadim , Turner Jennifer
Published: April 2013

The recent breakthrough developments of polymer-filled armor cables with crush-free electrical cores, effectively eliminate inherent limitations of wireline logging cables. These novel cables deployed with a complete high-tension conveyance package have effectively reduced deepwater-wireline tool sticking occurrences and the subsequent lengthy fishing operations in emerging Deepwater and depleting reservoirs.

Unique composite polymer technology locks the normally unbound cable armors to the core. Further Coldflow and crush resistant protection is added to the cable core itself. The result is a mechanically rigid, torque-balanced and crush-free wireline cable that effectively eliminates known issues with core codlflow, cable rotation & plastic stretch, armor stranding & bird-caging, while enabling high-tension spooling on a drum without the use of tension relief system (Capstan). With spooling tensions up to 13,000 lbf, instantaneous pulls of 18,000 lbf and a safety margin of 9,000 lbf, the complete high tension package offers tool sticking mitigation capabilities only possible previously with a Capstan package. Additional benefits include but not limited to fully seasoned new cable and reduced frequency of cable maintenance. Furthermore, the elimination of the dual drum Capstan eliminates significant operational risk.

TuffLINE 18000 - a composite cable was deployed successfully without Capstan in Deepwater Australia for an operation including formation pressure and sampling in a reservoir with a high tool sticking potential. In a particularly challenging situation in the Mediterranean where Capstan could not be deployed, TuffLINE 18000 was used in 5 descents resulting in 96 hrs of rig time savings while reducing HSE and operational risk.

With the proven financial and HSE benefits, polymer filled composite wreline cables and the high-tension conveyance package reduce wireline tool sticking risk.
An Integrated Approach to Managing Risks and Uncertainties: Combining Technical and Commercial Analysis
Authors: Lakani Ramin , Brown Daniel
Published: April 2013

As engineers and scientists, we are very familiar with analysing technical risks, developing mitigation plans and implementing the plans that are safe and technically feasible. At the same time, dealing with subsurface projects has made us adept at analysing and understanding technical uncertainties. Furthermore, because of the large investments involved in upstream projects we are regularly exposed to commercial issues. However, the optimum situation is when the technical and commercial risks and uncertainties are evaluated in an integrated fashion.

Although many organisations combine technical and commercial evaluations, there are many examples that such integration is either superficial or is done in a series. Often the economic evaluation is performed at the end of the process, by which time it may be too late to influence the decisions or the changes may be too expensive to implement.

Techno-economic integration becomes absolutely essential when our industry faces "game-changing" technologies, for example: Unconventional resource developments: Shale gas/oilIsolated gas monetisation: Gas to Liquid (GtL), Floating Liquefied Natural Gas (FLNG)Heavy oil developments: In-situ combustion, Steam Assisted Gravity Drainage (SAGD), Cold Heavy Oil Production with Sand(CHOPS)

Examples will be given to demonstrate the successes and failures of game changing technologies, where the failures are generally less advertised. It is important to discuss the ‘lessons learnt’ from these important events in our recent history: How can we apply techno-economic evaluation in an integrated fashion (and at an earlier stage) to better evaluate risks and uncertainties associated with implementing game-changing technologies? How can we influence the outcome of these projects?

This discussion is particularly relevant to the North Africa region as governments, National Oil Companies (NOCs) and International Oil Companies (IOCs) try to harness unconventional resources and seek alternative ways to monetise their gas resources.
Conduits Mapping for Naturally Fractured Reservoirs Using 3D Template Matching Model for Sub Seismic Faults Convergence
Authors: El Fouly Adel
Published: April 2013

Fractured reservoirs are more complicated than matrix reservoirs and they do require to be evaluated correctly. Information on the accurate characterization of fault zones and on the way in which faults and fractures affect fluid flow are needed. In this study, a 3D multi component and multi directional deterministic operator is designed and developed to detect sub-seismic faults from seismic data that converge at a point, to map conduits in naturally fractured reservoirs. This operator is cubic and composed of nine symmetrical two dimensional plane templates. They are designed to search all possible directions and angles, to detect and match any two sub-seismic faults that meet at its center. It covers seventy two detection directions, and angles range from 22.5° to 157.5°. Three binary decisions are performed with each of the nine symmetrical planes. the first is for detecting a sub seismic fault at a point, the second is for evaluating a linear arrangement of these points and the third is to verify if two linear arrangements exist on the same plane.

The case study is presenting conduits maps to demonstrate the behavior of three different sub-seismic fault size ranges. The conduits intensities vary within and for each formation. They are minimal to absent in reservoirs top seal. This technique detects only small scaled faults. It can't detect primary sedimentary structures and random noises. It provides an output related to the variation of dual porosity and permeability and can be considered a supporting input for more realistic reservoir simulation. This technique helps determine the effect of natural fractures in the reservoirs as early as possible so that the evaluations and planning can be done correctly from day one. It is a reliable tool for reservoir top seal fracturing evaluation, sweet spots in fractured reservoirs delineation and potential compartments identification.
Radial Drilling Technique for Improving Well Productivity in Petrobel-Egypt
Authors: Ragab Adel M. , Kamel Amr M.
Published: April 2013

With growing global energy demand and depleting reserves, oil well stimulation has become more important. In all of these reservoirs, formation damage is a headache problem which needs to be treated. One of the proposed techniques is to bypass the damaged zone. Radial drilling can provide a solution with lowest costs than the others.

Radial drilling technique utilizes hydraulic energy to create several lateral holes in different directions and levels with several lengths. These lateral holes are made by milling the casing with small bit then by extending these holes laterally using high pressure hydraulic jetting.

The current paper presents a very good analysis and an evaluation of the radial drilling techniques that have been made in one of the Egyptian oil field, and presents screening criteria about the optimum parameters for performing these techniques. A number of pilot tests was performed and analyzed in Egypt in Belayim oil field. Radial drilling performed only on three wells in Egypt; the results obtained from these wells are monitored and analyzed. The reservoir depth varies from 2172 meter to 2481 meter. The first well was laterally drilled with 50 m long by seven laterals and the angle between each two is 90 degrees. The second well was laterally drilled with 50 and 90 m long by 6 laterals in two different levels. The third well was radially drilled by 4 laterals of 50 m long.

From the production point of view, the first well was improved by more than 12.5% increase in production, and the second shows an improvement by about 47% increase. The third well shows an improvement by about 12.5 % but for short period. Several experiences have been learned and registered from drilling these 17 laterals which will help generally for the future radial drilling operational around the world.
Potential of Nitrogen Gas Miscible Injection in South East Assets, Abu Dhabi
Authors: Belhaj Hadi , Khalifeh Hadil Abu , Javid Khalid
Published: April 2013

This study evaluated the potential for application of miscible nitrogen injection to South East assets in Abu Dhabi which include three giant onshore oil fields. MMP (Minimum miscibility pressure) for different N2- oil systems was determined as a key criterion for screening. CMG simulation and correlations approaches were employed for determining pure N2 MMP.

Results of the study demonstrated that pure nitrogen miscible injection is promising for some reservoirs in the SE fields when reservoir pressure is higher than the MMP. Different correlations have been investigated for suitability to Abu Dhabi crude oils. Investigated MMP correlations are applied to the available data sets and a comprehensive error analysis is performed based on a comparison of the predicted value using published correlations with the simulated value using CMG simulator. Two simulation methods were employed to calculate MMP's: cell to cell and key tie line.

The Hudgins and Sebastian correlations are in a good agreement with the simulated MMP indicated by small absolute deviation of 10.9% and 2.9% respectively. Glaso, Hanssen, and Firoozabadi correlations produced unrealistic results. The impact of critical parameters such as C1 fraction, C2-C5 fraction, and molecular weight of C7+, API, and temperature on the MMP of nitrogen injection was investigated.
What Can Tell, What's Uncertain? In Depth Decline Curve Analysis
Authors: Rahuma Khulud , Belhaj Hadi
Published: April 2013

DCA (Decline curve analysis) is one of the most powerful tools used in defining well/reservoir worth. DCA aims at estimating reservoir production performance at any time (of production) post plateau period providing realistic and well documented production data. DCA helps in developing production-rate/reservoir-pressure distributions to determine well/reservoir productivity scheme. Forecasting well/reservoir production rate, estimating remaining reserves, monitoring GOR & WC behaviors, deciding on reservoir pressure support and determining economic limits are among the many befits of DCA as well.

In this study the AOR (Actual Oil Rate) method has been implemented utilizing the DCA, FASTRTA™ and Ecrin packages to calculate remaining and recoverable reserves in particular. The remaining reserves depend on the production data that are selected to represent the actual well/reservoir behavior. This technique allows eliminating misrepresenting production data due to human error, imposed production rates caused by internal company policy or external factors (politics, natural disasters, etc.) during production life of the field.

A case study has been used as a pilot for the proposed method. Analyses have been performed on both well and whole reservoir scale. The outcome yielded more realistic results using AOR and generated very useful development recommendations. The proposed AOR-DCA adopted technique can assist in accurate decisive parameters estimate of both mature and under-development oil reservoirs worldwide.
Low H2S Concentration Sampling Using Wireline Formation Tester and Well Testing: Case Studies
Authors: Samir Magdy , Cañas Jesus , Stankiewicz Artur , Ayan Cosan , Ferguson Richard , Colacelli Santiago Esteban
Published: April 2013

Knowing the H2S concentration early in the exploration and appraisal phase of a potential hydrocarbon discovery is critical for proper planning of the development phase. Production from a newly discovered accumulation often requires tie-in to an existing pipeline or facility, which usually has an upper limit on how much H2S can be handled, if any. The presence of H2S also affects the design of the completion and the production systems. Not discovering H2S until the production phase can halt production while the surface facilities are upgraded to handle the sour gas, which can be very expensive.

Several publications have shown that using standard wireline formation testing (WFT) to obtain fluid samples without adequate planning and preparation may result in H2S being scavenged during sampling or during transfer. In addition, standard gas chromatography (GC) analysis may measure small H2S concentrations inaccurately. Alternative methods for sampling and conserving small H2S concentrations have been proposed, but they are supported only by laboratory tests with no actual field data published.

In this paper, we present case studies of applying low H2S concentration sampling in the field. The wireline formation sampling was designed to capture samples with very small amounts of H2S under field conditions. This includes selection of the materials used in the sampling tool, tool string setup, choice of coating material for the sampling bottles, transfer of samples and analysis. The flow path inside the sampling tool was reduced to minimize the potential loss of H2S. In addition to wireline formation testing, the wells were also tested using a traditional drillstem test (DST). The results of the well test and the wireline sampling agreed well in both cases.
Petroleum Prospectivity of the Jurassic Strata of the Jeffara Basin, Tunisia
Authors: Haddad S.. , Echihi O.. , Jemia H. Ben
Published: April 2013

Integrated study was carried out on the Jeffara basin in order to understand and discuss the geometry and the key levels as well as Petroleum System elements on the Jurassic strata.

The studied area lies as N140-130 trending down faulted area roughly parallel to the coastline; it was developed mainly in response stage of Tethyan rifting. The subsurface data reveal that most of the structuring is amplified by halokinesis and the salt piercement of the entire sedimentary cover in the southeast area.

The Mrabtine Formation, which is represented by a mixed siliciclastic and carbonate deposits, is considered to be the best Jurassic potential reservoir rock in the Jeffera basin.

The Callovian shales appear to contain the best potential for source rock off all units in the Jurassic, showing poor to good TOC contents (up to 3.27% TOC) and good petroleum potential up to 10 kg of HC/ton of rock. The kerogens are mainly type II algal material and mix type II and III with locally higher type III organic material in El Bibane and Jerba area.

Several prospects and leads have been identified at the top of the Mrabtine Formation, these structures are extensional fault related (horsts or tilted fault blocks) with a NW-SE orientation. The northern part of the Jeffara basin shows several attractive fault related traps but sedimentological and stratigraphic studies indicate that there would be a risk of poor reservoir characteristics, a lack of source facies and top seal. The southern domain contains fewer structures and leads but more attractive plays with the proven hydrocarbon accumulations of the Ezzaouia and El Biban Fields.
Agroclimatology‐Based Yield Model for Carrot Using Multiple Linear Regression and Artificial Neural Networks
Authors: Thiagarajan Arumugam , Lada Rajasekaran R. , Muthuswamy Sivakami , Adams Azure
Published: April 2013

Understanding the relationship between root bulking and agroclimatological factors can aid in predicting the yield and quality of processing carrot (Daucus carota L.). Field trials (four field seasons) with selected cultivars at various seeding rates, seeding dates, and harvest dates were conducted for three carrot types, viz., baby, diced, and sliced, and yield components were monitored. The corresponding weather data, such as minimum and maximum temperature, solar radiation, and rainfall, were recorded. Data from the 2006, 2007, and 2009 field seasons were used for model development, while 2008 data were reserved for the validation. Following a forward‐stepwise regression procedure to identify highly correlated input factors, feed‐forward back‐propagated artificial neural network (ANN) and multiple linear regression (MLR) models were developed. After validation, the best performing models were identified based on a ranking system that weighed the root mean square error (RMSE) and the fitness of the model (R2). For baby carrots, the Sugarsnax‐based MLR model exhibited 23% lower RMSE than the ANN for the desirable yield component. In diced carrots, predictions from both models (ANN and MLR) exhibited a good fit, with high R2 values (0.80–0.90). For sliced carrots, Topcut‐based ANN models predicted the majority of the yield components consistently better than MLR models. When MLR and ANN models were compared, their efficiencies differed with carrot type and yield component. The MLR models underperformed in modeling processes that were inherently nonlinear compared with ANN. Nonetheless, ANN models suffered from overfitting and consequently at times failed to demonstrate extrapolation capabilities.
Relevance of Sprinkler Irrigation Time and Water Losses on Maize Yield
Authors: Urrego‐Pereira Yenny Fernanda , Martínez‐Cob Antonio , Cavero Jose
Published: April 2013

Daytime sprinkler irrigation with a solid‐set system can result in higher water losses, lower uniformity, and lower maize (Zea mays L.) yield compared with nighttime irrigation. We studied the relevance of irrigation time (daytime or nighttime) and water losses (compensating them or not in the irrigation applied) for the growth and yield of maize during 2 yr. The seasonal average sprinkler water losses compensated ranged from 14 to 19% for daytime irrigation and from 5 to 11% for nighttime irrigation. The average Christiansen coefficient of uniformity (CU) was similar for daytime and nighttime irrigation in 2009 (84%) but lower for daytime irrigation (78%) than nighttime irrigation (84%) in 2010. Daytime irrigation decreased the maize grain yield by 9% in the year that the CU was reduced. Increasing the water applied to compensate the water losses increased the soil matric potential but did not increase maize yield. The lower irrigation uniformity for daytime sprinkler irrigation compared with nighttime sprinkler irrigation seems to be a relevant reason for the yield reduction. Solid‐set sprinkler irrigation systems for maize should be designed to minimize daytime irrigation or to allow a high daytime irrigation uniformity (>84%).
Writing in the Accounting Curriculum: A Review of the Literature with Conclusions for Implementation and Future Research
Authors: Riley Tracey J. , Simons Kathleen A.
Published: April 2013

Accounting practitioners, faculty, and professional organizations agree that good writing skills are imperative to success in accounting, yet successful implementation of writing in the accounting curriculum continues to be a concern. Accounting faculty can benefit from an overview of the literature addressing writing in the accounting curriculum. Thus, this review of the literature is offered to assist both faculty who wish to implement or enhance such a writing program, and researchers who wish to further contribute to this discussion. We have read, categorized, and summarized over 100 published articles. In this paper, we review survey data among practitioners, academics, and students that examine the extent to which writing skills are important, or perceived to be important, to practicing accountants, and how effectively those skills are being addressed in the curriculum. We then review articles discussing writing within and across the accounting curriculum. We have categorized these articles into three sections: writing to learn versus learning to write, types of assignments, and implementation considerations. Throughout, we offer research questions and suggestions for future research. We conclude with a discussion and critical analysis of the current state of writing within the accounting curriculum and suggestions for where we go from here.
The Effect of Perioperative Ibuprofen Use on Tooth Sensitivity Caused by In-Office Bleaching
Authors: Paula E , Kossatz S , Fernandes D , Loguercio A , Reis A
Published: April 2013

Objective:

This study determined the effect of the administration of perioperative ibuprofen 400 mg on tooth sensitivity caused by in-office bleaching.

Methods:

A triple-blind, parallel-design, randomized clinical trial was conducted on 30 adults who received placebo or ibuprofen before and after bleaching. The drugs were administered three times per day for 48 hours; the first dose was given one hour prior to the bleaching treatment. Two bleaching sessions with 35% hydrogen peroxide gel were performed with a one-week interval. Tooth sensitivity was recorded on two scales: visual analogue and five-point verbal rating scale up to 48 hours after bleaching. The shade evaluation was performed with a visual shade guide and spectrophotometer, before and 30 days after bleaching. The absolute risk of tooth sensitivity and its intensity were evaluated by Fisher exact and Mann-Whitney tests, respectively. The shade changes were evaluated by Student's t-test.

Results:

Both groups showed similar absolute risk of tooth sensitivity (p>0.05). Lower tooth sensitivity was observed in the experimental group only up to one hour postbleaching (p=0.04). Similar tooth sensitivity was observed in the other periods of time.

Conclusion:

The perioperative use of the anti-inflammatory ibuprofen was not able to avoid tooth sensitivity but reduced its intensity up to one hour after bleaching.
Evaluation of Resin Bond Strength to Yttria-stabilized Tetragonal Zirconia and Framework Marginal Fit: Comparison of Different Surface Conditionings
Authors: Vanderlei A , Bottino MA , Valandro LF
Published: April 2013

The purpose of this study was to evaluate the effect of different surface treatments of yttria-stabilized tetragonal zirconia (Y-TZP) on bond strength durability and marginal discrepancies. For adhesion testing, 144 specimens of VITA In-Ceram YZ ceramic for InLab were obtained (5.25×3.75×4.5 mm) and divided into six groups (n=24) according to the surface treatment: 1) Control (CRTL): untreated; 2) SIL: tribochemical silica coating (CoJet system, 3M/ESPE AG); 3) V1+HF: spray application of low-fusing porcelain glaze (V1, VITA Akzent Spray Glaze) followed by etching with hydrofluoric acid (HF) (one minute); 4) V1+SIL: V1 glazing (VITA Akzent Spray Glaze) followed by tribochemical silica coating; 5) V2+HF: brush application of low-fusing porcelain glaze (VITA Akzent Glaze) plus etching with HF (one minute); and 6) V2+SIL: V2 glazing (VITA Akzent Glaze) plus tribochemical silica coating. After all treatments, the surfaces were silanized for five minutes (ESPE-SIL) and cementation was performed using Panavia F (Kuraray). Half of the specimens in each treatment were tested 24 hours after cementation (dry), with the other half subjected to storage (150 days) and thermocycling (12,000×) (aging), and then a shear test was carried out (1 mm/min). The micromorphological (digital optical profilometry and scanning electron microscopy) and elemental analyses of the treated surfaces were performed. The inner surfaces of 60 Y-TZP infrastructures were conditioned and marginal fit was evaluated. The statistical analysis revealed that the groups treated via surface glaze application followed by hydrofluoric acid etching and silanization showed the highest bond strength (in dry and aging conditions), but the bond strengths were affected by aging. The highest marginal discrepancies were observed in the groups receiving glaze (117.4 ± 29.6 to 105.8 ± 12.2 μm) when compared to other groups (55.3 ± 8.7 and 55 ± 8.5 μm). Low-fusing porcelain glaze + hydrofluoric acid etching changed the morphology of the Y-TZP ceramic and improved the adhesion to the resin cement, but obtaining high and stable bond values to Y-TZP remains challenging. Marginal discrepancies increased with glazing.
Tıp fakültesi ve konservatuvar öğrencilerinde fibromiyalji sıklığının karşılaştırılması.
Authors: Demirdal Ümit Seçil , Şensoy Nazlı , Darıcı Didem , Türemenoğulları Bengü , Sezen Mehmet , Kenanoğlu Ömer
Published: April 2013

Fibromiyalji sendromu (FMS), eklem dışı tutulumla giden, yaygın vücut ağrısı ve hassas noktaların varlığı ile karakterize kronik bir hastalıktır. FMS’nin patogenezinde psikososyal stres risk faktörleri arasında yer almaktadır. Son yıllarda kronik ağrının tedavi basamakları içerisinde sakinleştirici ve dinlendirici etkisi nedeniyle müzik ile tedavi yer almaktadır. Bu çalışmanın amacı uzun süreli ve yoğun bir eğitim programı sebebiyle stres faktörünün daima hissedildiği Tıp Fakültesi öğrencilerinde ve müziğin olumlu etkisinin hissedilebileceği Devlet Konservatuvarı öğrencilerinde FMS sıklığının saptanması ve karşılaştırılmasıdır.Yöntem: Bu tanımlayıcı çalışmaya Tıp Fakültesi’nden 258 ve Devlet Konservatuarı’ndan 184 öğrenci dahil edildi. FMS tanısı Amerikan Romatoloji Derneği'nin (ACR) 1990 kriterlerine göre kondu. Veriler ki-kare, student t testi ve Mann-Whitney U testi ile değerlendirildi.Bulgular: Tıp Fakültesi’nde %2.3, Devlet Konservatuarı’nda %5.4 öğrenci FMS tanısı aldı. İki öğrenci grubu arasında istatistiksel fark yoktu (p=0.123).Sonuç: Bu çalışmada diğer üniversite eğitimlerine göre daha uzun ve zor olan tıp eğitimi nedeniyle stres faktörünün yüksek olduğu Tıp Fakültesi öğrencilerinde FMS sıklığı, Devlet Konservatuvarı öğrencilerinden farklı bulunmadı. Diğer yandan, FMS sıklığını etkileyebilecek sosyoekonomik düzey gibi diğer faktörlerinde araştırıldığı ileri çalışmalar farklı verilere ulaşmamızı sağlayabilir.
Designing, Construction, Assessment, and Efficiency of Local Exhaust Ventilation in Controlling Crystalline Silica Dust and Particles, and Formaldehyde in a Foundry Industry Plant
Authors: Morteza Mortezavi Mehrizi , Hossein Kakooi , Amirhossein Matin , Naser Hasheminegad , Gholamhossein Halvani , Hossein Fallah
Published: April 2013

The purpose of the present study was to design and assess the efficiency of a local exhaust ventilation system used in a foundry operation to control inhalable dust and particles, microcrystal particles, and noxious gases and vapours affecting workers during the foundry process. It was designed based on recommendations from the American Conference of Governmental Industrial Hygiene. After designing a local exhaust ventilation system (LEV), we prepared and submitted the implementation plan to the manufacturer. High concentrations of crystalline silica dust and formaldehyde, which are common toxic air pollutants in foundries, were ultimately measured as an indicator for studying the efficiency of this system in controlling inhalable dust and particles as well as other air pollutants. The level of occupational exposure to silica and formaldehyde as major air pollutants was assessed in two modes: first, when the LEV was on, and second, when it was off. Air samples from the exposure area were obtained using a personal sampling pump and analysed using the No. 7601 method for crystal silica and the No. 2541 method for formaldehyde of the National Institute for Occupational Safety and Health (NIOSH). Silica and formaldehyde concentrations were determined by visible absorption spectrophotometry and gas chromatography. The results showed that local exhaust ventilation was successful in preserving the crystal silica particles in the work environment at a level below the NIOSH maximum allowed concentration (0.05 mg m-3). In contrast, formaldehyde exceeded the NIOSH limit (1 ppm or 1.228 mg m-3).
Effects of Smoking during Pregnancy on DNA Damage and ROS Level Consequences in Maternal and Newborns’ Blood
Authors: Aydogan Umit , Durmaz Emre , Ercan Cihangir Mutlu , Eken Ayse , Ulutas Onur Kenan , Kavuk Serkan , Gursel Orhan , Alanbay Ibrahim , Akay Cemal , Kurekci Ahmet Emin , Aydin Ahmet , Sayal Ahmet , Saglam Kenan , Cok Ismet
Published: April 2013

Some of the genotoxic/carcinogenic substances or metabolites in cigarette smoke are capable of passing through the placenta and harming a newborn’s health. Smoking is also known as a factor in the formation of oxidative damage and the main mechanism involved in the carcinogenic process. Predetermining this genotoxic risk can be successfully achieved by measuring certain parameters of oxidative stress. The comet assay is considered an important biomarker for the evaluation of genotoxic substances and is effective for detecting DNA damage caused by smoking. This study examined third trimester bloods and the cord blood of 28 actively smoking and 22 non-smoking mothers in terms of DNA damage and oxidative stress parameters. Cu/Zn superoxide dismutase (CuZn-SOD), malondialdehyde (MDA), catalase (CAT), plasma nitrite/nitrates (NO2 -/NO3 -), selenium-dependent glutathione peroxidase (Se-GPx), Cu, and Zn levels were measured as indicators of oxidative damage. There were no significant increases in DNA damage of the actively smoking pregnant group in comparison with the non-smoking pregnant group, either in the third trimester or cord blood. Oxidative stress parameters of smoker and non-smoker groups were statistically different for MDA (p<0.05), CuZn-SOD (p<0.01), Se-GPx (p<0.05) values while the difference was not significant for NO2 -/NO3 -, CAT, Zn, and Cu values. The same values were also investigated in cord blood, and only NO2/NO3 -(p<0.01), Se-GPx (p<0.01 and CAT (p<0.001) values were found statistically different. Smoking mothers may have been exposed to more oxidative stress than non-smoking mothers.
Comparative Analysis of Environmental Impacts of Selected Products
Authors: Fedoryszyn A. , Brzeziński M.
Published: April 2013

The purpose of the present study is to demonstrate that environmental impacts exerted by manufactured products throughout their entire life cycle are major aspects to be considered, alongside their functional features and cost-effectiveness. One of the available methods to evaluate environmental impacts is known to as the Life Cycle Assessment (LCA) method. The study summarises the reports from the literature on the subject of environmental impact assessment. In conclusions, the authors indicate the need for assessing the environmental impact of cast products made from conventional and newly introduced alloys.
Modeling of the Formation of AlN Precipitates During Solidification of Steel
Authors: Kalisz D. , Rzadkosz S.
Published: April 2013

The study was carried out computer simulations of the formation process of AlN precipitates in the solidification of steel. The chemical composition of steel and non-metallic inclusions formed was determined using the commercial software FactSage. Calculated amount of precipitates formed during cooling of steel between the liquidus and solidus temperatures under conditions of thermodynamic equilibrium. In parallel, the computations were performed using your own computer program. It was found that aluminum nitride is formed at the final stage of solidification, and the condition of its formation is low oxygen content in steel.