bluuebunny/crossref_metadata_2025 huggingface dataset:
Refining the foam index test for use with air-entrained fly ash concrete
Authors: McCarthy Michael J. , Islam G. M. Sadiqul , Csetenyi Laszlo J. , Jones M. Roderick
Published: October 2012

The paper describes a study aimed at improving the foam index test method for evaluating the interaction between air-entraining admixtures (AEAs) and fly ash in the production of concrete. Ten fly ashes, two commercial AEAs and a standard reagent (sodium dodecyl benzene sulfonate surfactant) were considered. Initial tests, using manual (hand) shaking, indicated that the foam index was prone to high variability between operators (coefficients of variation 19·6–27·0% for three fly ashes with loss-on-ignition (LOI) up to 7·6%) compared with that of a single operator (coefficient of variation 11·6%). In an attempt to address this, a simple automatic shaker was considered. Tests with this demonstrated that the foam index was influenced by the shaking speed and duration, suggesting that differences in the former during manual shaking contributed to the variability noted between operators. The automatic shaker also gave a more uniform foam, making the test end point (established visually) easier to determine. This approach was then examined to establish suitable working conditions and the operator variability tests were repeated. The automatic shaker reduced the coefficients of variation for the test to about half of those for manual shaking between operators, with slight reductions for the single operator. A comparison of foam index, obtained by automatic shaking, with sorptivity-related properties of fly ash indicated better correlations with specific surface area (N2 adsorption using the BET method) than LOI. The study then progressed to investigate relationships between the foam index and AEA doses to achieve target air contents in both mortar and concrete. The results indicated very good correlations between these for both (cement-based) systems. Similar behaviour was also obtained in the various tests carried out for the commercial AEAs and standard reagent. Means of using the refined foam index test in practical situations are explored.
Shear behaviour of ultra-high-performance fibre-reinforced concrete beams without stirrups
Authors: Yang In-Hwan , Joh Changbin , Kim Byung-Suk
Published: October 2012

The experimental results of shear strength and deformation tests for 12 ultra-high-performance fibre-reinforced concrete (UHPFRC) beams without stirrups are presented in this paper. I-beam specimens with a depth of 700 mm were cast using UHPFRC with the compressive strength of 160–190 MPa. The experimental parameters were the shear span to effective depth ratio, the volume fraction of steel fibres, and the presence or absence of prestress. The failure mode, indicating tensile failure in the web of the beam, was accompanied by fibre pull-out along the major diagonal crack. The test results indicated that the first cracking and ultimate shear strengths increased as the volume fraction of steel fibres increased. The ultimate shear strength decreased as the shear span to effective depth ratio increased. The increase in ultimate shear strength resulted from the instability of arch action at the shear span to effective depth ratio. In addition, the ultimate shear strength of prestressed beams increased compared with that of non-prestressed beams. The test results of this study provide valuable data that can be used in future studies to develop computational models of the shear behaviour of UHPFRC.
Durability performance of self-compacting concrete
Authors: Venkateswara Rao S. , Seshagiri Rao M. V. , Ramaseshu D. , Rathish Kumar P.
Published: October 2012

The methodological shift in the thinking about concrete from a strength-based concept to a durability-based design has led to the development of self-compacting concrete (SCC). This paper presents a systematic experimental programme on durability studies conducted, covering three grades of SCC from low strength (M20 grade) to high strength (M70 grade). The durability studies include acid attack, corrosion, sorptivity and thermal studies. The main objective of this investigation is to develop SCC mixes that are resistant to acid attack and suitable for Indian temperature conditions compared with vibrated normal concrete. Other durability factors such as capillary absorption and corrosion resistance of three such grades of SCC mixes have also been investigated. It was noted from the durability studies that in almost all cases the loss in durability is reduced with increase in grade of concrete. Furthermore, a comparison of SCC and normal concrete mixes has shown a good performance of SCC specimens as against normal concrete specimens.
Durability-related properties of mortar and concrete containing copper tailings as a cement replacement material
Authors: Onuaguluchi Obinna , Eren Özgur
Published: October 2012

This paper reports the results of research investigating the impact of copper tailings on some durability properties of cement pastes, mortars and concretes. Four mixtures incorporating copper tailings at 0% to 15% cement substitution levels by mass were used. Minor reductions in sulfate resistance of mortars and improved performance against autoclave expansion of pastes were observed in mixtures containing copper tailings. Despite increased water absorption and total permeable voids in concrete samples containing copper tailings, sample compressive and tensile strengths comparable to those of the control specimens were obtained. Resistance to acid attack and chloride penetration improved as the copper tailings content of mixtures increased. Moreover, chloride penetration depths obtained from immersion tests suggest that because the rapid chloride permeability test is an indicator of sample conductivity rather than chloride permeability, it may not be appropriate for evaluating mixtures with high-conductivity copper tailings. The high conductivity of concretes containing copper tailings could potentially be utilised in the de-icing of roadways and electromagnetic shielding of electrical and electronic devices.
Prediction of FRP debonding using the global-energy-balance approach
Authors: Achintha Mithila , Burgoyne Chris J.
Published: October 2012

A major research programme was carried out to analyse the mechanism of fibre-reinforced polymer (FRP) debonding from concrete beams using the global-energy-balance approach (GEBA). The analyses developed in the study provide an essential tool that will enable fracture mechanics to be used to determine the load at which FRP plates will debond from concrete beams. This obviates the need for finite-element analyses in situations where reliable details of the interface properties and crack-tip stress fields are not obtainable for an accurate analysis. This paper presents an overview of the GEBA analyses that is described in detail elsewhere, and explains the slightly unconventional assumptions made in the analyses.
Photocatalysis with hybrid Co-coated WS2 nanotubes
Authors: Tsverin Y. , Livneh T. , Rosentsveig R. , Zak A. , Pinkas I. , Tenne R.
Published: October 2012

Inorganic fullerene-like (IF) nanoparticles (NP) and inorganic nanotubes (INT) of layered compounds, such as WS2, have been of particular interest due to their unique structural characteristics. Recently, the catalytic decomposition of thiophene using INT of WS2 decorated with Co NP was demonstrated. This finding also suggests that these materials could be also suitable for the photocatalytic treatment of pollutants in wastewaters. In the present work, the photocatalytic decomposition of methyl orange (MO) in aqueous solution using Co-coated INT-WS2 as well as other NP was investigated. The photocatalytic reactivity under visible light illumination of this photocatalyst was measured and compared with that of various IF and INT and TiO2 (P25). The Co NP-coated INT-WS2 exhibited the highest photodegradation of MO among the studied NP. The significant enhancement in the photoactivity of the hybrid nanostructure can be attributed to the combination of the metallic Co NP and the semiconducting WS2 nanotubes. The hybrid nanostructure enables the efficient light absorption by the INT and the subsequent charge separation of the hybrid semiconductor-metal NP under visible light illumination. In addition, Raman spectroscopy technique was used to verify that the MO was decomposed by Co-coated nanotubes and not adsorbed in large amounts on the hybrid NP surface.
A highly efficient 2D flood model with sub-element topography
Authors: Jamieson Sam R. , Lhomme Julien , Wright Grant , Gouldby Ben
Published: October 2012

The need for large-scale and regional probabilistic simulations means that two-dimensional (2D) inundation models are still limited by computational requirements. In addition to parallelisation and physical process simplification, attempts to reduce runtimes typically involve coarsening the computational mesh, which can smooth important topographic features and hence limit accuracy. This paper presents a new 2D flow model that uses an enhanced diffusion-wave algorithm, and incorporates sub-element topography in a computational mesh that adapts to the terrain features. The model utilises a fine topographic resolution without having to use a fine computation mesh, and so achieves fast computational runtimes. The model has been tested against the UK Environment Agency's 2D benchmarking tests, and even though the model is designed to operate at larger spatial scales than those in the benchmarking tests, it is shown to provide comparable accuracy relative to a selection of conventional 2D models, at significantly faster computational speeds. The model therefore has the potential to offer a step change in performance of large-scale probabilistic flood mapping and systems flood risk analysis modelling.
Loss of native herbaceous species due to woody plant encroachment facilitates the establishment of an invasive grass
Authors: Alofs Karen M. , Fowler Norma L.
Published: October 2012

Although negative relationships between diversity (frequently measured as species richness) and invasibility at neighborhood or community scales have often been reported, realistic natural diversity gradients have rarely been studied at this scale. We recreated a naturally occurring gradient in species richness to test the effects of species richness on community invasibility. In central Texas savannas, as the proportion of woody plants increases (a process known as woody plant encroachment), herbaceous habitat is both lost and fragmented, and native herbaceous species richness declines. We examined the effects of these species losses on invasibility in situ by removing species that occur less frequently in herbaceous patches as woody plant encroachment advances. This realistic species removal was accompanied by a parallel and equivalent removal of biomass with no changes in species richness. Over two springs, the nonnative bunchgrass Bothriochloa ischaemum germinated significantly more often in the biomass‐removal treatment than in unmanipulated control plots, suggesting an effect of native plant density independent of diversity. Additionally, significantly more germination occurred in the species‐removal treatment than in the biomass‐removal treatment. Changes in species richness had a stronger effect on B. ischaemum germination than changes in plant density, demonstrating that niche‐related processes contributed more to biotic resistance in this system than did species‐neutral competitive interactions. Similar treatment effects were found on transplant growth. Thus we show that woody plant encroachment indirectly facilitates the establishment of an invasive grass by reducing native diversity. Although we found a negative relationship between species richness and invasibility at the scale of plots with similar composition and environmental conditions, we found a positive relationship between species richness and invasibility at larger scales. This apparent paradox is consistent with reports from other systems and may be the result of variation in environmental factors at larger scales similarly influencing both invasibility and richness. The habitat loss and fragmentation associated with woody plant encroachment are two of many processes that commonly threaten biodiversity, including climate change. Many of these processes are similarly likely to increase invasibility via their negative effects on native diversity.
Phase Trapping Damage in Use of Water-Based and Oil-Based Drilling Fluids in Tight Gas Reservoirs
Authors: Bahrami Hassan , Rezaee Reza , Saeedi Ali , Murickan Geeno , Tsar Mitchel , Mehmood Sultan , Jamili Ahmad
Published: October 2012

Low matrix permeability and significant damage mechanisms are the main signatures of tight gas reservoirs. During drilling and fracturing of tight formations, the wellbore liquid invades the tight formation, increases liquid saturation around wellbore and eventually reduces permeability at near wellbore. The liquid invasion damage is mainly controlled by capillary pressure and relative permeability curves.

Water blocking and phase trapping damage is one of the main concerns in use of water based drilling fluid in tight gas reservoirs, since due to high critical water saturation, relative permeability effects and strong capillary pressure, tight formations are sensitive to water invasion damage. Therefore, use of oil based mud may be preferred in drilling or fracturing of tight formation. However invasion of oil filtrate into tight formations may result in introduction of an immiscible liquid hydrocarbon drilling or completion fluid around wellbore, causing entrapment of an additional third phase in the porous media that would exacerbate formation damage effects.

This study focuses on phase trapping damage caused by liquid invasion using water-based drilling fluid in comparison with use of oil-based drilling fluid in water sensitive tight gas sand reservoirs. Reservoir simulation approach is used to study the effect of relative permeability curves on phase trap damage, and results of laboratory experiments core flooding tests in a West Australian tight gas reservoir are shown in which the effect of water injection and oil injection on the damage of core permeability are studied. The results highlights benefits of using oil-based fluids in drilling and fracturing of tight gas reservoirs in term of reducing skin factor and improving well productivity.
Real Time Drilling Geomechanics: Successful Application in an Inclined Well in Ultra-Deepwater off East Coast of India
Authors: Kumar Devendra , Singh Hemant , Kumar Rajeev , Rao Dhiresh G. , Sundaram K. M.
Published: October 2012

Assurance of wellbore stability (WBS) is of utmost concern and a key challenge in drilling an inclined well in ultra deep water of the East Coast of India. The WBS analysis requires accurate modeling of earth stresses and rock mechanical properties. These processes are primarily based on sonic logs (compressional and shear slowness), bulk density and lithological distribution. To understand and address drilling complications in the study area, post-drill (offset well analysis) and real-time drilling geomechanics is carried out in this well.

1D mechanical earth model (MEM) and WBS model is constructed for offset wells, which is calibrated with caliper log, pressure test and leak-off data sets. WBS analysis suggested drilling with lower mud weight in the zones of shear failure and pack-off. Disparity in resistivity values is also observed when wireline logs and Logging-While-Drilling (LWD) logs are analyzed. This might be due to mud invasion or fluid-shale interaction in the open hole, as it is resolved by changing mud system from water based mud (WBM) to synthetic oil base mud (SOBM). The post-drill analysis of offsets wells established parameters for the upcoming inclined well.

The planned well is the first inclined well (horizontal drift more than ∼2000m) in ultra deepwater of the East Coast of India to avoid the drilling risks; real-time drilling geomechanics is first time put into operation. Required sonic and density data is received in reasonable time intervals to perform real-time analysis. Timely updates on rock mechanical properties are provided to client, which helped in optimizing drilling parameters. As a result, first inclined well in ultra deep water in the East Coast of India was drilled successfully.
Positive Psychology and the Company Man
Authors: Hase Stewart , Phin Simon
Published: October 2012

This discussion paper concerns the critical role leadership plays on safety behaviour in the innately hazardous environment of oil and gas installations. It has been demonstrated on a number of occasions that safety culture is a major determinant of either positive or negative safety behaviour. In turn it is clear that managers at all levels on a rig can determine the safety culture though the emphasis they place on safety in all that they do. It has also been shown that transformational and transactional leadership styles are much more effective in developing a positive safety culture than authoritarian and passive styles. Positive psychology is a relatively new concept in psychology that emphasises an optimistic view of people and the world, of possibilities and what can be done. The approach provides a number of easily learned techniques that can improve leadership style and safety culture as part of the essential war on fatalities and injuries.
New Practices for Cement Integrity Evaluation in the Complex Environment of Xinjiang Oil Field
Authors: Hongzhi Guo , Guobin Wang , Zhi Wang
Published: October 2012

Junggar basin in west China is rich in oil and gas reserves in different geological structures that range in depth from 800 m to 7000 m. A variety of cement slurries is used to ensure the cement integrity in the wells. For instance, low-density cement as light as 1.1 g/cm3 with hollow glass microspheres has been used for low-pressure-gradient formations in long openhole wellbores, whereas high-density cement as heavy as 2.5 g/cm3 with iron mineral powder and other additives has been applied in high-pressure deep wells. This variety poses challenges to performing cement evaluation with traditional acoustic techniques that have limitations in providing unambiguous answers, and in some instances it is not possible to assess implications to zonal isolation behind casing.

A new-generation ultrasonic imaging tool was deployed to increase the confidence in cement evaluation in Xinjiang oil field over the past 2 years. This technique combines the traditional pulse-echo ultrasonic measurement with a new flexural wave measurement. The analysis allows a better discrimination of solid, liquid and gas for density-independent cement evaluation behind casing, additional information on casing centering, annulus geometry, and accurate casing inspection at high resolution in one logging trip. Based on this improved zonal isolation information, well testing design improved, and the testing success rate was significantly increased over previous operations. Moreover, the cementing technique improved from proper post evaluation. The examples in this paper demonstrate the value of the high-quality logging data that were acquired in different downhole conditions. This paper presents a new way to look at cement quality and placement.
Artificial Neural Networks for Corrosion Rate Prediction in Gas Pipelines
Authors: Supriyatman Deden , Sumarni Sumarni , Sidarto Kuntjoro Adji , Suratman Rochim
Published: October 2012

Artificial Neural Network (ANN) is adopted from the human neural network systems and is among many tools to understand complex model including corrosion. Such predictive model can be developed through corrosion rate. By ANN application, one may update its model iteratively, hence it will be adaptable for all decisions. It can be learned from the previous data and recognize patterns of data always changing and dynamic, like the ones in oil and gas fields.

Based on the characteristics of ANN methods, corrosion rate model will update iteratively during the training phase leading to the best (more accurate) model target. Using a number of data input and output characteristics of the fluid, the result of corrosion rate model will be able to predict the corrosion rate in the range of the entered input data. With models that are adaptive and can adjust to changes in the dynamic data, one will be able to obtain predictions with a great degree of accuracy.

Research methodology on the subject using crude oil was developed by Hernandez and Nesic (2005). Some crude oil characteristic associated with the corrosion rate are, among others, sulfur, vanadium, nickel contents, total acid number and API. A correlation analysis between the crude oil characteristics vs corrosion rate, then a regression model of percentage of inhibiton which is a function of characteristics of crude oil were obtained. Percentage of inhibition in this regard is the number of ratio between the corrosion rate of the fluid-carrying pipe and corrosion rate in the blank pipe.

This paper will describe ANN that creates a program to determine the corrosion rates of the carbon-steel materials containing flowing fluid (gas). The characteristics evaluated are gas composition, temperature and pressure then regression equation of inhibition percentage will be made in the characteristics function of earlier inputs. Only data having a high level of significance will be used, and the ones of very low level of significances will be excluded in the equation. The next step is building models with ANN for which significant data based on the regression test will be used as input data to the corrosion prediction program in gas pipelines.

The deliverable of this study is getting the prediction program of gas pipeline corrosion of carbon steel using MATLAB software. The program accuracy of the program is compared with the actual data.
Simulation of Formation Damage after Long Term Water Flooding
Authors: He Liu , Guoxin Li , Yiliang Li
Published: October 2012

Water flooding is a commonly used technology for enhancing oil recovery. Its mechanism is to maintain higher pressure in reservoir and to sweep the oil from the reservoir and push it towards production wells. However the strong water flooding will cause higher compression pressure around the injection wellbore. This high pressure in the reservoir causes stress redistribution and higher stress near the wellbore which induces material damage and permeability change. We developed a fluid-solid coupling finite element model to simulate and quantitatively analyze the pressure evolution in the reservoir as well as damage and permeability change in the formation during long term water flooding process. The obtained results offer theoretical understanding on the benefits (pore pressure increase in the simulation domain), rock damage, permeability change of long term water flooding and the insights of how to detect and prevent wellbore failure and collapse due to water flooding.
Direct Averaging Estimates of Separate Zone Production in Gas Wells Based on Pressure and Temperature Profiles
Authors: Barrett E. , Abbasy I. , Wu C.-R. , You Z. , Bedrikovetsky P.
Published: October 2012

Accurate and reliable flow rate estimation along the wellbore plays an important role in reservoir development and production management. Traditional methods are expensive, particularly in high temperature wells; and they usually involve running production logsging tools (PLT) together with flowmeters. Deployment of PLTs into a well can be operationally difficult and typically requires flow to be suspended temporarily to allow the tools to be run in hole. This can have a negative impact on the quality of data collected, potentially making it un-representative of normal producing conditions. Alternatively, a simple direct averaging method of the gas flow rate estimation from temperature and pressure data is proposed in this paper, compared to the iterative approach. Solution of the inverse problem allows predicting the flow rate and formation thermal conductivity by matching the gas pressure and temperature profiles with field data. The results of data treatment show good agreement with the model prediction and are consistent with flowmeter (PLT) data, which validates the method developed in this work.
Stimulation of Natural Cleats for Gas Production From Coal Beds by Graded Proppant Injection
Authors: Bedrikovetsky P. , Keshavarz A. , Khanna A. , Kenzie K. M. , Kotousov A.
Published: October 2012

Graded injection of proppant particles with increasing size and decreasing concentration, proposed in the previous paper results in deep percolation of proppant into the natural fracture system, expansion of the stimulated zone and enhanced well productivity index. The mathematical model developed describes the proppant-free water injection stage, the capture kinetics of proppant particles in the natural fractures and the change in well index due to graded proppant injection. Computational fluid dynamics and classical Hertz theory have been used to determine the hydraulic resistance due to proppant plugging in the fracture system and the deformation of fractures during the production stage.

An optimal injection schedule, i.e. the timely dependence of the injected proppant size and concentration that avoids fracture closure during production stage and provides minimum hydraulic resistance in the system of fractures plugged by proppant particles has been developed. The model is used to predict the change in well productivity index allowing estimating the feasibility of the graded particle injection for well stimulation in natural fractured systems.

The aim of the current paper is to analyse the feasibility of application of the proposed graded proppant injection method for stimulation of the natural fracture system in 3 field cases of large coal bed methane reservoirs.
Fracture Growth and Injectivity Issues for Produced Water Reinjection Wells - Case Studies with Fields from Australia and the UK North Sea
Authors: Rahman Khalil , Khaksar Abbas
Published: October 2012

Produced water reinjection is gradually becoming a preferable option for water disposal because of increasing stringent environmental regulations. During long-term injection, a fracture usually initiates from the injection well and then grows deep into the formation. The growth of this fracture and the long-term injectivity are mainly influenced by formation properties, solids loading in water, in-situ stresses and well trajectory. Fracture growth and injectivity during produced water reinjection are influenced by long-term leak-off processes, thermo-poroelastic changes within the formation and the intermittent injection nature.

This paper presents an approach for systematic considerations of critical issues that greatly influence the well trajectory, completion, fracture growth and long-term injectivity. The approach was applied recently to two field cases for planning and decision-making: one field in Australia and the other field in the UK North Sea. The effects of the following issues on fracture growth and injectivity were addressed in the North Sea field case: in-situ stress magnitudes and direction; thermo-poro-elasticity; solids loading; perforations, tubing strength and pump capacity; and operational issues to maintain injectivity. Although the above issues were common to the Australia case, the special challenge came from high solids loading in water requiring a very large fracture to store solids particles.

Highlights of the study results include (1) potential fracture growth complexity and injectivity loss, (2) high pressure loss requiring high pump capacity, (3) undesirable fracture growth risking well completion and surrounding structures, and (4) fracture tip plugging by formation debris during intermittent injection. Mitigation strategies for all these complexities are also addressed in the paper.

The paper will guide engineers when addressing geomechanical, fracture growth and injectivity issues at the planning and designing stages of a produced water reinjection well.
Best Practices in Developing Deep Tight Gas Reservoirs for Maximum Recovery, Sultanat of Oman
Authors: Busaidi R. , Diamond L. , Mugheiry S. , Abri Z. , Rendon J. , Lukmanov R.
Published: October 2012

The Main Sultanat of Oman Gas Field is comprised of two deep tight gas clastic reservoirs, separated by thick shale layer, and has been on production since 1999. These reservoirs are encountered at depth ranges of 14,000 - 17,000 ft and the top reservoir is a rich gas condensate followed by a lean gas for the lower reservoir. Permeability is in the range of 0.01 to 10 mD, porosities of 1 % to 14% and this field being a swing producer, actual production is in the range of 700 - 1,000 MMsfcd.

To ensure achieving a maximum value, from such complex reservoirs, the field has gone through several development stages. The first stage has focused mainly on appraisal and development wells to obtain better understanding of well and reservoir performance and further data acquisition for better reservoir characterisation.

The second stage of the Field Development Plan (FDP), in 2005, was an update of the FDP reflecting all the information that have become available since the commission of the field as well as the production performance gained from the previous 5 years of production. Further optimization of total number of wells, better prediction of the field performance and firming up the first stage of depletion compression were the key elements of the FDP update. Hence, first stage depletion compression plant was pursued and commissioned in 2010. In addition, velocity strings from 51/2" to 27/8", for maximum utilisation of low producing wells, were evaluated and more appraisals activities, for further scope maturation, were assigned.

The third stage of the FDP update has been completed. The key objectives were to validate the previous FDP, in particular, wells and reservoir performance as a result of stage-1 depletion compression. Besides, phase-2 depletion compression was proposed and the remaining development drilling were re-evaluated, optimised and confirmed.

Furthermore, a plan to mature contingency reserves, from poor reservoir intervals, was initiated and associated studies, such as geomechanical models and fracturing optimisation were performed.

In this paper, a case study of developing a complex and tight deep gas reservoir will be discussed. The experience of applying phase approach and associated value will be shared and how the multidisciplinary team came up with the best Field Development Plan taking into consideration the different challenges and options taken by every discipline to put the best development strategy to get the optimum ultimate recovery from the field.
An Innovative Static Modeling Approach to handle a Complex Giant Mature Field within a Compressed Timeframe; A Case Study of the Baram Oil Field, Offshore Sarawak, East Malaysia
Authors: Latief Agus Izudin , Ridzuan Ahmad Idriszuldin , Faehrmann Paul Andrew , MacDonald Alister , Nasir Wardah Arina , Rahman Gozali , Rahman Mohd Elzrey
Published: October 2012

Baram is a giant mature field situated, offshore Sarawak Malaysia. Reservoirs consist of an approximately 7000 ft thick-stacked sequence of shallow marine sands, distributed in excess of 200 zones. The field is extensively faulted. Early Growth faulting followed by a later compressional phase has led to complex fault geometries. The field has been producing for over 40 years and presently has 175 wells.

Although the reservoirs are generally of good quality, the field currently has relatively low production rates, a low recovery factor, and a significant amount of remaining reserves. The geological complexity poses a key challenge, and a robust static reservoir model is a prerequisite for efficient reservoir management and for identifying viable Improved Oil Recovery (IOR) measures.

Static models of the Baram field had previously been constructed. This modelling took in excess two years to complete and the models were segmented into 10 pieces, as technology during this period was unable to tackle complex fault geometries. Due to the results of the static / dynamic modelling being insufficiently robust when tested during a drilling campaign in 2009, the decision was made to remodel.

The Baram subsurface team was challenged with building a static model which could be used for field management and IOR/EOR process selection and optimization within a six month timeframe. This is to allow for early investment decisions and an accelerated reversal of production decline. The key aspects of the fixed timeframe static model construction are described below. They consist of:

The subdivision of the field into independent models. The utilization of a modern algorithm to model complex fault geometry. Nested stratigraphic modeling. Parallel property modeling and the re-combining of results into a single simulation grid to enable integrated reservoir simulation.

A full focus on the importance of the timeline and early investment, plus the adoption of a variety of strategic project management measures and use of "state of the art" modeling technology can allow fit-for-purpose static models to be delivered on time.
Simulation of Multiphase Fluid-Hammer Effects during Well Shut-In and Opening
Authors: Han Guoqing , Ling Kegang , Khor Siew Hiang , Zhang He , Company Ryder Scott , Thakur Ram Kinkar
Published: October 2012

In this study, a transient multiphase simulator has been used to characterize the fluid-hammer effects of well shut-in and start-up on the coupled subsurface and surface systems. The original work was performed by applying sensitivity analysis on a typical production system that includes well completion, wellbore, downhole equipment like packer etc., and the associated surface equipment like flowline, riser and valves. The data used in the study was taken from the published literature to summarize the general course of key factors that worsen the fluid-hammer effects. Fluid-hammer is also known as water hammer, a shock wave produced by the sudden stoppage or reduction in fluid flow.

Field operations such as pressure transient analysis, facility maintenance and workover require well shut-in process. For a typical production system, the resulted sudden rises in pressure can be critical because it has direct impact on equipment including unsetting of packer and may also cause possible damages to instrumentations. This paper provides estimates of the typical ratio of transient shock in pressure and flowrate over pre-condition values, and the duration of such pressure shocks. It also proposes the best location of the shut-in valve and the length of flowline to reduce the fluid-hammer effects.

This is a pioneering approach to integrate multiphase flow modeling of transient fluid-hammer effects, targeting flow assurance issues. This approach also can be applied to surface facility design and served as guidance in field operation to avoid hydrocarbon leaks.
Optimizing the Value of Reservoir Simulation through Quality-assured Initialization
Authors: Worthington Paul F. , Hattingh Shane K.
Published: October 2012

The initialization of a reservoir simulator calls for the populating of a three-dimensional dynamic grid-cell model using subsurface data and interrelational algorithms that have been synthesized to be fit for purpose. These prerequisites are rarely fully satisfied in practice. This paper sets out to strengthen initialization through four key thrusts. The first addresses representative data acquisition, which includes the key-well concept as a framework for the cost-effective incorporation of free-fluid porosity and permeability within an initialization database. The second concerns the preparation of these data and their products for populating the static and dynamic models. Important elements are dynamically-conditioned net-reservoir cut-offs, recognition of primary flow units, and establishing interpretative algorithms at the simulator grid-cell scale for application over net-reservoir zones. The third thrust is directed at the internal consistency of capillary character, relative permeability properties and petrophysically-derived hydrocarbon saturations over net reservoir. This exercise is central to the simulation function and it is an integral component of hydraulic data partitioning. The fourth concerns the handling of formation heterogeneity and anisotropy, especially from the standpoint of directional parametric averaging and interpretative algorithms. These matters have been synthesized into a workflow for optimizing the initialization of reservoir simulators. In so doing, a further important consideration is the selection of the appropriate procedures that are available within and specific to different software packages.

The implementation of these thrusts has demonstrably enhanced the authentication of reservoir simulators through more readily attainable history matches with less required tuning. This outcome is attributed to a more systematic initialization process with a lower risk of artefacts. Of course, these benefits feed through to more assured estimates of ultimate recovery and thence hydrocarbon reserves.
An Innovative Approach to Understanding Shale Gas Well Behavior Based on a Performance Catalogue Fingerprint
Authors: Boulis Anastasios , Jayakumar Ram , Araque-Martinez Aura , Rai Rakesh
Published: October 2012

Shale gas wells performance is governed by the interaction between reservoir rock and the completion. However, external factors such as liquid loading, inefficient completion, and in some cases offset wells, can also influence performance. The large volume of shale gas wells necessitates the development of quick diagnostic tools. The linear transient flow behavior is well documented in shale gas wells; however, the post-linear transient flow behavior and the impact of non-reservoir phenomena are not. The objective of this paper is to provide a signature catalogue based on well performance fingerprints to quickly diagnose well history for dominant production mechanisms. To build the catalogue, both synthetic models and actual well history were used. All the data generated were analyzed using a consistent in-house shale gas workflow.

This paper documents well performance signatures for various reservoir and non-reservoir phenomena. The synthetic models provided a controlled basis to study for aspects of reservoir and completion phenomena difficult to measure in the field such as the sequence of flow regimes, the impact of different completion configurations, pressure dependent permeability and conductivity, as well as fracture complexity. Actual field histories from various shale gas plays were used to study the impact of processes that are normally observed in field data but are difficult to predict by a model such as liquid loading, fracture cleanup, data quality and impact of artificial lift. The signature catalogue shows impact of different completion configuration and reservoir phenomena during the periods of constant linear transient productivity index and on the decline in productivity index once the fracture interference starts. The impact of inadequate completion cleanup is captured on the linear flow plot as a completion resistance factor. The impact of shut-in, diagnostics for liquid loading, and inconsistent or questionable data has also been analyzed. The behavior of the wells with complex fracture geometries, pressure dependent permeability and pressure dependent completion properties is also catalogued. This fingerprint catalogue is a valuable resource for the engineer as it allows for prompt identification of abnormal well behaviors and provides a diagnostic method for identifying various production mechanisms.
Local, Regional and National Responses for Medical Management of a Radiological/Nuclear Incident
Authors: Dainiak Nicholas , Skudlarska Beata , Albanese Joseph
Published: October 2012

Radiological and nuclear devices may be used by terrorists or may be the source of accidental exposure. A tiered approach has been recommended for response to a terrorist event wherein local, regional, state and federal assets become involved sequentially, as the magnitude in severity of the incident increases. State-wide hospital plans have been developed and published for Connecticut, New York and California. These plans address delineation of responsibilities of various categories of health professionals, protection of healthcare providers, identification and classification of individuals who might have been exposed to and/or contaminated by radiation and, in the case of Connecticut response plan, early management of victims. Regional response programs such as the New England Regional Health Compact (consisting of 6 member states) have been developed to manage consequences of radiation injury. The Department of Homeland Security is ultimately responsible for managing both health consequences and the crisis. Multiple US national response assets may be called upon for use in radiological incidents. These include agencies and programs that have been developed by the Department of Energy, the Environmental Protection Agency and the Department of Defense. Coordination of national, regional and state assets with local response efforts is necessary to provide a timely and efficient response.
Effect of Red Cell Transfusions on Future Kidney Transplantation
Authors: Obrador Gregorio T. , Macdougall Iain C.
Published: October 2012

Red cell transfusions, erythropoiesis-stimulating agents (ESAs), and intravenous iron therapy all have a place in the treatment of anemia associated with CKD. Their relative merits and uses are subject to many clinical and nonclinical factors. New concerns associated with the use of ESA therapy make it likely that the use of blood transfusions will increase, refueling previous debates about their associated risks. Data on whether red cell transfusions increase sensitization to HLA antigens, rendering subsequent transplantation more problematic, are mainly derived from older literature. Older data suggested that women were more at risk of HLA sensitization than men, particularly those with previous multiple pregnancies, although recent U.S. Renal Data System data have challenged this. HLA sensitization prolongs the waiting time for transplantation and reduces graft survival. Leukocyte depletion of red cells does not appear to reduce the risk of HLA sensitization. This review summarizes much of the data on these issues, as well as highlighting the need for further research on the potential risks for blood transfusion in patients with CKD.
Association of Circulating Fibroblast Growth Factor-23 with Renal Phosphate Excretion among Hemodialysis Patients with Residual Renal Function
Authors: Wang Mengjing , You Li , Li Haiming , Lin Yong , Zhang Zhijie , Hao Chuanming , Chen Jing
Published: October 2012

Background and objectives

High serum levels of fibroblast growth factor-23 (FGF-23) are associated with mortality in patients with ESRD, but whether it still acts as a phosphaturic factor is unknown. This study aimed to explore the role of circulating FGF-23 on urinary phosphate excretion and phosphate balance in maintenance hemodialysis (MHD) patients with residual renal function (RRF).

Design, setting, participants, & measurements

There were 134 MHD patients enrolled in this cross-sectional study from June to July 2010. Demographics, laboratory data, and excretion capacity of phosphate were recorded. Multivariable linear regression was used to analyze the relationship of serum phosphate and the tubular reabsorption rate of phosphate with other factors.

Results

The median age of the patients was 61.0 years and 47.8% were male. Thirty percent of the patients had high urinary output (>200 ml/d) accompanied by lower serum levels of phosphate, calcium, intact parathyroid hormone, and FGF-23 compared with those with low urine output (≤200 ml/d). The independent predictors of serum phosphate were normalized protein nitrogen appearance, intact parathyroid hormone, and FGF-23 in the low urine output group and female sex and GFR in the high urine output group. The tubular reabsorption rate of phosphate decreased to 50% of the normal level in patients with RRF. Elevated circulating FGF-23 was significantly associated with lower tubular phosphate reabsorption after adjusting for GFR.

Conclusions

RRF is associated with significant capacity to excrete phosphate in MHD patients and high levels of serum FGF-23 may promote phosphate excretion by remnant nephrons.
Early Dialysis Initiation and Rates and Timing of Withdrawal From Dialysis in Canada
Authors: Ellwood Amanda D. , Jassal S. Vanita , Suri Rita S. , Clark William F. , Na Yingo , Moist Louise M.
Published: October 2012

Background and objectives

The number of elderly patients and those with higher estimated GFR (eGFR) initiating dialysis have recently increased. This study sought to determine rates of withdrawal from dialysis and variables associated with withdrawal.

Design, setting, participants, & measurements

Canadian Organ Replacement Registry data were used to examine withdrawal rate and identify variables associated with withdrawal among the total cohort, patients age < 75 years, and patients age ≥ 75 years, along with those with early (eGFR > 10.5 ml/min per 1.73 m2) and those with late (eGFR ≤ 10.5 ml/min per 1.73 m2) initiation of dialysis, using a Cox proportional hazard model in patients starting dialysis between 2001 and 2009, with follow-up to December 31, 2009.

Results

Median follow-up duration was 23.0 (interquartile range [IQR], 34.3) months. Rate of withdrawal per 100 patient-years doubled from 1.5 to 3.0, and withdrawal as cause of death increased from 7.9% to 19.5% between 2001 and 2009. Early initiation of dialysis was associated with increased withdrawal risk (hazard ratio, 1.17; 95% confidence interval, 1.06–1.30; P=0.002), as were older age, female sex, white race, and late referral to nephrologist. Patients age ≥ 75 years withdrew earlier after dialysis initiation (median, 15.9 [IQR, 27.9] months) compared to those age < 75 years (21.6 [IQR, 35.2] months). Early-start patients withdrew earlier (median, 15.6 [IQR, 28.5] months) compared with late-start patients (20.2 [IQR, 32.9] months).

Conclusions

In Canada, withdrawal from dialysis has increased significantly over recent years, especially among patients starting with higher eGFRs and in the elderly.
Association of Epitope Spreading of Antiglomerular Basement Membrane Antibodies and Kidney Injury
Authors: Chen Jun-liang , Hu Shui-yi , Jia Xiao-yu , Zhao Juan , Yang Rui , Cui Zhao , Zhao Ming-hui
Published: October 2012

Background and objectives

Antiglomerular basement membrane autoantibodies are pathogenic in antiglomerular basement membrane disease with two major epitopes, EA and EB, on α3 chain of type IV collagen. This study investigated the epitope spectrum of antiglomerular basement membrane autoantibodies, aiming to identify the association between epitope specificity and kidney injury.

Design, setting, participants, & measurements

All 108 patients with antiglomerular basement membrane disease and complete clinical data were divided into three groups according to renal dysfunction: mild group (n=20) with serum creatitine≤1.5 mg/dl; moderate group (n=22) with serum creatinine=1.5–6.8 mg/dl; severe group (n=66) with serum creatitine≥6.8 mg/dl. Epitope spectrums of antibodies were determined by ELISA, and their associations with kidney damage were analyzed. Sequential serum samples in 40 patients were examined during disease courses.

Results

EA and EB were recognized in 79.6% and 72.2% of patients, respectively. EA and EB reactions were the lowest in the mild group and higher in the moderate group (EA: 35.0% versus 81.8%, P=0.002; EB: 15.0% versus 68.2%, P=0.001). They were the highest in the severe group (EA: 92.4%, P=0.31; EB: 90.9%, P=0.02). Close association was observed between renal injury and EA and EB reactions. Multivariate Cox regression analysis showed that EB reaction was an independent risk factor for renal failure (hazard ratio=6.91, P=0.02). The recognition for non-EAB remained low among groups. No augmentation of epitope spectrum was shown in serial serum samples.

Conclusions

Intramolecular epitope spreading might occur before the onset of human antiglomerular basement membrane disease. The autoimmunity to EA and EB, especially EB, was crucial for kidney dysfunction.