bluuebunny/crossref_metadata_2025 huggingface dataset:
Estabilizador de sistemas de potencia digital aplicado a uma unidade geradora da uhe de Tucurui
Authors: Nogueira Fabrício G , Barra Junior Walter , Costa Junior Carlos T. da , Barreiros José A. L , Nascimento Filho Paulo S , Moraes Anderson R. B , Gomes Marcus Ciro , Lana Jânio José de
Published: October 2012

Este trabalho apresenta o desenvolvimento e resultados de testes de campo de um estabilizador de sistemas de potência (ESP) digital, destinado ao amortecimento de oscilações eletromecânicas em sistemas interligados. Os testes experimentais foram efetuados em uma das unidades hidrogeradoras, de 350 MVA, da UHE de Tucuruí. A lei de controle amortecedor do ESP digital foi embarcada em um sistema de hardware baseado em um controlador digital de sinais (DSPIC 30f5011). A estrutura da lei de controle é na forma canónica RST, de tempo discreto, sendo os parâmetros do controlador calculados através da técnica de deslocamento radial de pólos. Para fins de projeto, a dinâmica da planta, no ponto de operação considerado, foi representada por um modelo paramétrico, o qual foi estimado a partir de dados medidos em campo. Os resultados experimentais mostraram um excelente desempenho do ESP digital no amortecimento de um dos modos eletromecânicos observável na UHE de Tucuruí.
A new simplified SVPWM algorithm based on modified carrier signal
Authors: Garcia Raymundo Cordero , Pinto João Onofre Pereira
Published: October 2012

This paper presents a simplified algorithm of space vector pulse width modulation (SVPWM) for a two-level three-phase inverter, which can operate in undermodulation and overmodulation modes. In other simplifications founded in literature, the reference voltages are modified and compared with a triangular carrier to estimate the switching states of the inverter. However, this paper proposes the modification of the carrier signal instead of the references. This procedure reduces the number of mathematical operations and increases the execution speed of SVPWM algorithm in DSPs or FPGAs. The reference voltages are sinusoidal, even for overmodulation mode. Simulation and experimental results proves that the proposed simplification produces the same switching patterns than conventional SVPWM, is simpler and is faster than other simplifications.
Applying global time Petri net analysis on the embedded software context
Authors: Peres Leticia Mara , Künzle Luis Allan , Todt Eduardo
Published: October 2012

This paper presents an application of Global Time technique (GTT) which is an approach to construct class graphs of Time Petri nets based on relative and global time. Besides the constructing of GTT class graph we propose a schedulability analysis of quantitative time type for fixed priority policies and Earliest Deadline First (EDF). We propose that analysis of scenarios, or behavior itineraries duration of a system, can be done using this approach.
Hammer impact test applied for fouling detection in pipelines
Authors: Silva Jaidilson Jó da , Neff Franz Helmut , Lima Antonio Marcus Nogueira , Rocha Neto José Sérgio da
Published: October 2012

The fouling detection in duct systems is a persistent problem and remains a relevant demand for the chemical, oil, food and pharmaceutical industries. The fouling is a deposition process of heavy organic and other dissolved solid materials in the transported fluids or suspensions onto inner wall surfaces in fluid transport systems. This work presents research results of hammer test for vibration analysis using non-invasive tests to fouling detection in pipelines. Data were taken from the vibration in presence of an inner pipe fouling layer using an accelerometer and a microphone for detection. With the analysis of the obtained results is possible to detect the fouling process, in the monitored pipelines, with and without load conditions, using a microphone and an accelerometer as sensors.
Compact yet efficient hardware architecture for multilayer-perceptron neural networks
Authors: Silva Rodrigo Martins da , Mourelle Luiza de Macedo , Nedjah Nadia
Published: October 2012

There are several neural network implementations using either software, hardware-based or a hardware/software co-design. This work proposes a hardware architecture to implement an artificial neural network (ANN), whose topology is the multilayer perceptron (MLP). In this paper, we explore the parallelism of neural networks and allow on-thefly changes of the number of inputs, number of layers and number of neurons per layer of the net. This reconfigurability characteristic permits that any application of ANNs may be implemented using the proposed hardware. In order to reduce the processing time that is spent in arithmetic computation, a real number is represented using a fraction of integers. In this way, the arithmetics is limited to integer operations, performed by fast combinational circuits. A simple state machine is required to control sums and products of fractions. Sigmoid is used as the activation function in the proposed implementation. It is approximated by polynomials, whose underlying computation requires only sums and products. A theorem is introduced and proven so as to cover the arithmetic strategy of the computation of the activation function. Thus, the arithmetic circuitry used to implement the neuron weighted sum is reused for computing the sigmoid. this resource sharing decreased drastically the total area of the system. After modeling and simulation for functionality validation, the proposed architecture synthesized using reconfigurable hardware. The results are promising.
Repercussões do trabalho na saúde dos adolescentes trabalhadores
Authors: Pimenta Aline Alcântara , Freitas Fabiana Cristina Taubert de , Marziale Maria Helena Palucci , Robazzi Maria Lúcia Carmo Cruz
Published: October 2012

OBJETIVO: Identificar as repercussões à saúde em decorrência do trabalho realizado por adolescentes, em uma Fundação de Educação para o Trabalho em sua saúde. MÉTODOS: Estudo transversal, descritivo e quantitativo que investigou, entre abril e maio de 2010, 117 adolescentes trabalhadores da cidade de Ribeirão Preto (SP), por meio de um questionário multidimensional. A análise dos dados ocorreu por meio da estatística descritiva. RESULTADOS: A maioria era do sexo feminino (72,6%), com idade de 15 anos (80,3%), cor parda (60%), cursava o Ensino Médio (74,4%); apresentava renda familiar de até dois salários mínimos; morava com três a quatro membros da família e não havia trabalhado anteriormente (62,4%). A atividade mais exercida foi recepcionista (46,2%) e auxiliar administrativo (37,6%); 92,3% trabalhavam quatro horas por dia ganhando meio salário mínimo. Para 37,6%, o trabalho causava alterações à saúde, tais como, dores em várias regiões do corpo (76,2%) e problemas respiratórios. CONCLUSÕES: Houve repercussões na saúde dos adolescentes, possivelmente, por causa do trabalho.
Shear stiffness of granular material at small strains: does it depend on grain size?
Authors: YANG J. , GU X.Q.
Published: October 2012

The shear stiffness of granular material at small strain levels is a subject of both theoretical and practical interest. This paper poses two fundamental questions that appear to be interrelated: (a) whether this stiffness property is dependent on particle size; and (b) whether the effect of testing method exists in terms of laboratory measurements using resonant column (RC) and bender element (BE) tests. For three uniformly graded types of glass beads of different mean sizes (0·195 mm, 0·920 mm and 1·750 mm), laboratory tests were conducted at a range of confining stresses and void ratios, using an apparatus that incorporates both RC and BE functions and thus allows reliable and insightful comparisons. It is shown that the small-strain stiffness, determined by either the RC or BE tests, does not vary appreciably with particle size, and it may be practically assumed to be size independent. The laboratory experiments also indicate that the BE measurements of small-strain stiffness are comparable to the corresponding RC measurements, with differences of less than 10%. Furthermore, the BE measurements for fine glass beads are found to be consistently higher than the RC measurements, especially at large stress levels, whereas this feature becomes less evident for medium-coarse glass beads, and eventually diminishes for coarse glass beads. The study indicates that the characteristics of output signals in BE tests can be largely affected by the frequency of the input signal, the mean particle size of the material and the confining stress level, and that these factors are interrelated. Improper interpretation of wave signals may lead to shear stiffness measurements that are unreasonably low, either showing a substantial increase with particle size or showing the opposite. A micromechanics-based analysis assuming the Hertz–Mindlin contact law is presented to offer an understanding of the size effect from the grain scale.
Quantifying the evolution of soil fabric during shearing using directional parameters
Authors: FONSECA J. , O'SULLIVAN C. , COOP M.R. , LEE P.D.
Published: October 2012

Over the past 50 years, experimental studies have repeatedly demonstrated that the mechanical behaviour of sand is sensitive to the material fabric, that is, the arrangement of the grains. Up until now there have been relatively few attempts to describe this fabric quantitatively. Much of our understanding of the link between the particle movements and interactions and the macro-scale response of granular materials, including sand, comes from discrete-element modelling and experiments on ‘analogue' sands with simple, idealised shapes. This paper investigates methods of quantifying the directional fabric of a real sand and its evolution under loading. Statistical analyses of the distribution of fabric directional data in terms of particle, contact normal, branch vector and void orientations were carried out at different stages of shearing deformation. The data show that the initial particle orientation fabric that develops during the deposition of the material tends to persist during shearing, while in the post-peak regime the contact normals seem to be reoriented along the direction of the major principal stress. Different patterns were observed within the shear band, as both the particles and the contact normal vectors appeared to rotate along the shear plane.
Facilitating feedbacks between field measurements and ecosystem models
Authors: LeBauer David S. , Wang Dan , Richter Katherine T. , Davidson Carl C. , Dietze Michael C.
Published: October 2012

Ecological models help us understand how ecosystems function, predict responses to global change, and identify future research needs. However, widespread use of models is limited by the technical challenges of model–data synthesis and information management.

To address these challenges, we present an ecoinformatic workflow, the Predictive Ecosystem Analyzer (PEcAn), which facilitates model analysis. Herein we describe the PEcAn modules that synthesize plant trait data to estimate model parameters, propagate parameter uncertainties through to model output, and evaluate the contribution of each parameter to model uncertainty. We illustrate a comprehensive approach to the estimation of parameter values, starting with a statement of prior knowledge that is refined by species‐level data using Bayesian meta‐analysis; this is the first use of a rigorous meta‐analysis to inform the parameters of a mechanistic ecosystem model.

Parameter uncertainty is propagated using ensemble methods to estimate model uncertainty. Variance decomposition allows us to quantify the contribution of each parameter to model uncertainty; this information can be used to prioritize subsequent data collection. By streamlining the use of models and focusing efforts to identify and constrain the dominant sources of uncertainty in model output, the approach used by PEcAn can speed scientific progress.

We demonstrate PEcAn's ability to incorporate data to reduce uncertainty in productivity of a perennial grass monoculture (Panicum virgatum L.) modeled by the Ecosystem Demography model. Prior estimates were specified for 15 model parameters, and species‐level data were available for seven of these. Meta‐analysis of species‐level data substantially reduced the contribution of three parameters (specific leaf area, maximum carboxylation rate, and stomatal slope) to overall model uncertainty. By contrast, root turnover rate, root respiration rate, and leaf width had little effect on model output; therefore trait data had little impact on model uncertainty.

For fine‐root allocation, the decrease in parameter uncertainty was offset by an increase in model sensitivity. Remaining model uncertainty is driven by growth respiration, fine‐root allocation, leaf turnover rater, and specific leaf area. By establishing robust channels of feedback between data collection and ecosystem modeling, PEcAn provides a framework for more efficient and integrative science.
The behavior of multiple independent managers and ecological traits interact to determine prevalence of weeds
Authors: Coutts Shaun R. , Yokomizo Hiroyuki , Buckley Yvonne M.
Published: October 2012

Management of damaging invasive plants is often undertaken by multiple decision makers, each managing only a small part of the invader's population. As weeds can move between properties and re‐infest eradicated sites from unmanaged sources, the dynamics of multiple decision makers plays a significant role in weed prevalence and invasion risk at the landscape scale. We used a spatially explicit agent‐based simulation to determine how individual agent behavior, in concert with weed population ecology, determined weed prevalence. We compared two invasive grass species that differ in ecology, control methods, and costs: Nassella trichotoma (serrated tussock) and Eragrostis curvula (African love grass). The way decision makers reacted to the benefit of management had a large effect on the extent of a weed. If benefits of weed control outweighed the costs, and either net benefit was very large or all agents were very sensitive to net benefits, then agents tended to act synchronously, reducing the pool of infested agents available to spread the weed. As N. trichotoma was more damaging than E. curvula and had more effective control methods, agents chose to manage it more often, which resulted in lower prevalence of N. trichotoma. A relatively low number of agents who were intrinsically less motivated to control weeds led to increased prevalence of both species. This was particularly apparent when long‐distance dispersal meant each infested agent increased the invasion risk for a large portion of the landscape. In this case, a small proportion of land mangers reluctant to control, regardless of costs and benefits, could lead to the whole landscape being infested, even when local control stopped new infestations. Social pressure was important, but only if it was independent of weed prevalence, suggesting that early access to information, and incentives to act on that information, may be crucial in stopping a weed from infesting large areas. The response of our model to both behavioral and ecological parameters was highly nonlinear. This implies that the outcomes of weed management programs that deal with multiple land mangers could be highly variable in both space and through time.
Genetic and ecological assessment of population rehabilitation: walleye in Lake Superior
Authors: Garner Shawn R. , Bobrowicz Steven M. , Wilson Chris C.
Published: October 2012

Sustainable management of exploited species is an ongoing challenge, particularly where populations have collapsed or been depleted by overharvest and habitat alteration. The walleye (Sander vitreus) population in Lake Superior's Black Bay historically supported more than 90% of the commercial walleye harvest from the entire lake, but collapsed in 1968 and has still not recovered despite long‐term closure of the fishery. In an effort to rehabilitate this population, hatchery‐origin walleye from exogenous sources were released into Black Bay between 2003 and 2005. We used individual‐based analysis of genetic data collected between 2007 and 2010 to examine the contributions of different wild sources and hatchery stocking events to the contemporary walleye population in Black Bay. We found that 75% of the walleye in Black Bay originated from above‐ and below‐barrier native populations in the Black Sturgeon River. The hatchery stocking events differed considerably in their effectiveness: the 2003 release of fry had no measurable contribution, whereas the 2004 and 2005 releases of fingerlings contributed 71% and 45% of the fish in their respective age classes. Hatchery and wild fish were similar in size, but hatchery fish rarely utilized the river habitat where Black Bay walleye historically spawned, and there was little genetic evidence of interbreeding or natural recruitment of stocked fish. Overall, our results suggest that restoring habitat connectivity to facilitate wild recruitment has greater potential than further exogenous stocking to contribute to the recovery of walleye in this system.
Improved Health, Safety and Environmental Profile of a New Field Proven Stimulation Fluid
Authors: Braun W. , de Wolf C. A. , Nasr-El-Din H. A.
Published: October 2012

Acidizing treatments can help significantly improve the productivity of a well. Safe handling of commonly used corrosive acids, however, is a significant challenge to properly manage during the execution of the treatments. The additives, such as corrosion inhibitors, iron control agents, etc., typically used to mitigate the corrosive impact of acids and other un-wanted reactions during the treatments adds to the complexity of safe handling, while further aggravating the environmental impact of the overall treatment. Higher dosages of additives that are needed at higher treatment temperatures and pressures further compound the challenge. With the industry needs trending to high temperatures & pressures, and stricter health, safety & environmental (HSE) considerations, an alternative stimulation fluid that is suited for all the challenging conditions and be globally applicable with an acceptable environmental profile would be ideal.

Recent studies and field applications with a new stimulation fluid based on glutamic acid diacetic acid (GLDA) has shown that GLDA can improve permeability in carbonate and sandstone formations even at tough field conditions and can maintain the integrity of wells made of various tubular metallurgies. In the present paper the health, safety and environmental profile of GLDA is reviewed and compared against conventional stimulation fluids such as hydrochloric acid, acetic acid, hydrofluoric, etc., along with the commonly used additives.

GLDA is to a large extent based on a natural amino acid made from sustainable resources. It is biodegradable in both fresh and seawater. GLDA has a very favorable eco-tox profile and very low toxicity levels. In contrast to other stimulation fluids and frequently used additives, GLDA does not have any hazard classification and therefore requires no adverse safety labeling. GLDA can be handled easily and safely in the field with just standard chemical handling precautions in place. Overall, GLDA is a safe, environmentally friendly and effective stimulation solution that can help improve productivity of a well with the least possible well integrity or HSE concerns.
Design and Status of the Only Underground Gas Storage Project in Turkey after Three Years of Operation
Authors: Sahin Secaeddin , Abravci Suleyman , Tirek Ali
Published: October 2012

More than ninety eight percent of natural gas used in Turkey is imported predominantly from Russian Federation, Azerbaijan and Iran by pipeline, and Algeria and Nigeria as LNG. As in most developing gas consuming countries, Turkey's natural gas consumption varies in seasonal basis. Therefore, the country has had to work consistently to develop its transmission and storage systems. As a solution to this, Turkish Petroleum Corporation (TPAO) decided to convert the producing two gas fields, Kuzey Marmara (off-shore) and Degirmenkoy (on-shore) into underground gas storage facilities to accommodate seasonal variations in natural gas consumption.

The main reasons in choosing the Kuzey Marmara (K. Marmara) and Degirmenkoy fields as gas storage are the proximity of the fields to the gas pipeline network and Istanbul, and their suitability for gas storage because of their reservoir characteristics. The project area, however, is located in an environmentally sensitive region, which is also popular with its recreational and residential areas. Authority requirements regarding emissions, noise and other aspects were extremely severe.

The Silivri (K. Marmara and Degirmenkoy fields) underground natural gas storage (UGS) facilities with a storage capacity of 1.9 billion m3 were became operational on 13th of April 2007. Gas from the existing supply pipeline is currently being injected into the storage reservoirs and subsequently reproduced into the supply pipeline during the periods of high demand.

This paper provides the design and development process of the first and the only underground gas storage project of Turkey and also presents the status quo after the first three complete cycles.
Case Study of an East Siberian Field: A Holistic Review of Drilling Performance Enhancement
Authors: Buchan Andrew , Fazletdinov Marat , Okafor Zimuzor , Shulga Vladimir
Published: October 2012

The Verkhnechonskoye (VCNG) oilfield located in Eastern Siberia is developed on pad clusters, with in excess of 200 wells drilled to date. Typical well geometry consists of a vertical 13 3/8in. conductor followed by directional 12 ¼ in. and 8 ½ in. sections ran with subsequent 9 5/8in. and 7in. casing strings. Production hole is drilled in 6in. with a 4 ½in. liner set prior to completion. The predominant well design incorporates a double build profile which lands horizontally in the Verknechonskiy reservoir with an approximate 600m lateral drilled in the productive zone.

VCNG field has evolved of key strategic importance to deliver oil through the Eastern Siberia Pacific Ocean (ESPO) pipeline from Russia to the vast Asia-Pacific market located to its South East. Increasing production targets have been required to deliver hydrocarbons to fulfill aggressive pipeline commitments. Meeting these requirements have in turn initiated a relentless drive to enhance operational efficiency since the inception of development drilling phase in 2007; leading to a significant increase in drilling performance and reduction in overall well construction time in the period to date. This improvement has been achieved against the backdrop of an environment which is extremely challenging on several distinct fronts; remoteness of the project with >600km from the nearest major conurbation, harshness of an extreme continental climate with temperatures seasonally dropping to -50°C and coupled with a unique and problematic lithological column all serve to make drilling, logistics and general operations a complex undertaking.

The purpose of this paper will be to take a holistic review of drilling performance in the field and to chronicle the numerous incremental technological and procedural advancements which have led to a reduction in average well construction time from 58 to 21 days between 2007 and 2011. Incorporated into this dramatic efficiency improvement includes a 465% increase in average well ROP along with a corresponding increase in meters drilled per circulating hour (MPCH) of 390%.
A Glass Micromodel Experimental Study of Hydrophilic Nanoparticles Retention for EOR Project
Authors: Hendraningrat Luky , Shidong Li , Torsœter Ole
Published: October 2012

A number of researchers put on attention on nanoparticles suspension (nanofluids) as part of nanotechnology application in enhanced oil recovery (EOR) nowadays. This experimental study is preliminary stage of nanofluids for EOR project at NTNU. This paper presents the investigation of interfacial tension reduction, nanoparticles retention and permeability impairment in porous media by injecting nanoparticles suspension into glass micromodel. The deposition and pore-blockage of nanoparticles in glass micromodel were investigated and microscopically visualized by taking sequential images. A hydrophilic nanoparticles and synthetic seawater (brine, NaCl 3 wt. %) as base fluid were chosen in this study. The nanofluids were made with various concentration from 0.1 to 1.0 wt. %. The sonicator as liquid homogenization tool was used just before injecting the nanofluids into glass micromodel to avoid agglomeration.

A dynamic interfacial tension (IFT) phenomenon has observed during this experiment. Introducing dispersed nanoparticles in brine has reduced dynamic IFT. It will decrease when increasing nanoparticles concentration. Theoretically, it makes oil easier to move out since the friction force between water-phase and oil-phase will also decrease (Afrapoli, 2010).

Based on microscopic visualization from glass micromodel, it observed nanoparticle has deposited and adsorbed at surface pore network. In permeability measurement, it reduced 41–72% after injected with nanoparticles. Dynamic light scattering analysis is also performed for nanoparticles entrapment analysis. Another nanoparticles which has bigger average size and lower specific surface area, showed similar behavior with previous nanoparticles suspension. However the permeability reduction is less around 17–21% at similar nanofluids concentration.

In conclusion, this phenomenon of nanoparticles transport process possibly occurs due to its deposition on pore surface and blockage in pore throat of glass micromodel. This study provides essential knowledge for us of nanoparticles behavior in pore media before going further experiment stage to as EOR method.
Building a Roadmap for Enhanced Oil Recovery Prefeasibility Study
Authors: Lefebvre Ch. , Lemouzy P. , Sorin D. , Roy G. , Serbutoviez S.
Published: October 2012

This paper describes an easy-to-use and fast-track roadmap for Enhanced Oil Recovery (EOR) Prefeasibility Study including (1) screening of EOR suitable methods 2) estimating of additional recovery with mechanistic 3D models 3) evaluating preliminary economics (NPV) for field scale application 4) assessing the main uncertainties to reservoir, fluids and economical parameters.

Oil-production from EOR projects represents currently about 4% of the worldwide production; this ratio is expected to increase significantly in the near future. EOR projects require in general important investments often in matured fields. It is therefore important for a decision maker to have a global view of the main technical and economical expectations and risks ahead of an EOR project decision.

This roadmap helps identify ahead of an EOR project the main technical and economic challenges and provides a first Go/No-Go taking into account the main uncertainties and risks associated to this type of project.

The main results of this roadmap are a set of pre-defined mechanistic 3D models with different reservoir geometries and suitable for 7 EOR methods (polymer, surfactant, SP flooding, steam injection, SAGD, in situ combustion, gases injection) and a simple but robust economic model providing a set of default technical and economical input values. Risk analysis is performed on these technical and economical results using either a deterministic or a probabilistic approach.

The outcome of this roadmap is at field scale, for a given EOR method, an expected additional recovery factor and the corresponding discounted NPV with an uncertainty analysis on the main technical and economical parameters.
New Coiled-Tubing-Deployed Multizone Hydraulic Fracturing: An Unconventional Process for Unconventional Reservoirs
Authors: van Gijtenbeek Klaas , McNeil Fraser , Massaras Leon
Published: October 2012

Abstrac

Operators in the US have been producing from shale for decades, which places Europe and other continents with shale reservoirs in a unique position to benefit from the sharing of knowledge and technology already in use. However, Europe is faced with unique challenges that include the following: Rapid production decline.Water usage/disposal.Small pad size.Equipment limitations.High cost of nonproductive time (NPT).

To truly optimize a multizone stimulation treatment of unconventional reservoirs, one should not adopt the premise that the speed of the operation and initial production are all that determine success. Formation evaluation should be the primary determining factor in selecting the optimum completion technique, which must also provide a low-risk, operationally efficient solution designed to increase the reservoir contact and ultimately improve long-term production.

This paper discusses a new coiled-tubing (CT-) deployed hydraulic fracturing process, which is expected to have a considerable impact on advancing economic recovery of shale gas in Europe by fracturing one interval at a time using downhole mixing of proppant into the fracturing fluid. The downhole mixing rate can be manipulated in real-time to customize the placement and downhole-proppant concentration instantly. The combination of downhole mixing and microseismic fracture mapping provides unprecedented control of the fracturing treatment execution to facilitate branch fracturing. At the end of the final treatment stage, the well is simply cleaned out, with the entire operation completed with only one CT trip in hole. This paper reviews this technique, comparing it directly to conventional processes. In addition, background information is supplied from a combined CT/jointed-tubing (CT/JT) deployed hydraulic fracturing process.
Ranking of Hydrocarbon Reserves for the Management Them
Authors: Shandrygin A. N. , Smagina T. N. , Diakonov I. I. , Dubrovskiy D. A.
Published: October 2012

A method for ranking hydrocarbon reservoir with the zoning objects on the basis of geological knowledge and the economic efficiency of hydrocarbons production is proposed. For a ranking of hydrocarbon reserves, they are conventionally divided into four categories: profitable, contingently profitable, potential and non-commercial. Hydrocarbon reserves of reservoirs and fields are allocated to the categories, taking into account the geological, technological and economic criteria. The result is a ranking of information about the structure of the reserves for the planning of drilling, well intervention and the allocation of areas for pilot projects. The same information can be used to calculate the possible profiles of oil production in a different order involvement in the development zones of various categories of reserves and, thereby, to determine the optimal scenario of field development.
Petrophysical Base of Reservoir Saturation Type Prediction in Interwell Space
Authors: Kozhevnikov Dmitry , Kovalenko Kazimir , Deshenenkov Ivan
Published: October 2012

The integration of petrophysical and seismic data is a key technology for reservoir characterization and subsurface fluids monitoring. Rock physics as a link between seismic and logging data, it's applied to predict reservoir parameters, such as lithologies and pore fluids, from seismically derived attributes. Fluid substitution procedure is the rock physics technique for understanding how seismic velocity and impedance depend on pore fluids. The conventional fluid substitution model (Gassmann's model, 1951) assumes homogeneous water saturation without dividing on free and residual water shares.

On the base of petrophysical model of effective porosity we establish a new way of Gassmann's relation application for fluid effect on elastic properties simulation. This fluid substitution model takes into account free and residual water volumes and properties separately and cement swelling as well. Developed model was applied for Western Siberia sandstones and Eastern Siberia carbonates investigations. Seismic responses on oil and gas reservoirs characteristics were modeled with presented approach. Reservoir parameters such as saturation type, residual water features, reservoir properties were studied in seismic field with AVO modeling and simultaneous inversion of synthetic seismograms. The determination of conventional and developed model accuracy characteristics is carried out with Monte-Carlo technique. The outcomes indicate that the estimated error of proposed model is in 1.3–1.5 times less than conventional one.

The results of stated work could be the petrophysical base of the technique for reservoir saturation type prediction from seismic data, which provides identification of pay-zones, reservoir saturation mapping and three-dimensional modeling in order to drill for oil and gas.
Additional Acoustic Method for Measuring Formation Permeability in the Presence of Mudcake Achieved
Authors: Sinev A. V. , Dorovsky V. N. , Romensky E. I.
Published: October 2012

The interest in Stoneley waves in wellbores drilled through porous media comes from the dependence of its attenuation on formation permeability. This property makes the Stoneley waves an important tool for measuring the permeability of the porous medium [Xianyun, Hezhu, 2007; Dorovsky V. et al. 2010]. Drilling technology induces mudcake buildup between the borehole fluid and the porous formation with permeability of the latter being our main subject of this paper. Therefore what are the distinguishing properties of mudcake buildup during the permeability-measuring process while using the Stoneley wave properties, and what influence does mudcake thickness and rheology have on the attenuation length? There seems to be no obvious answer to these questions. Another important fact is dependence of the characteristics of the radial oscillations of the borehole fluid on formation permeability [Dorovsky et al. 2010; Dorovsky V. et al. 2012]. This fact allows one to measure formation permeability, and it should be evaluated for the case of mudcake presence. An issue of changes in the measuring procedure for permeability in the presence of radial oscillations of the borehole fluid arises in case of radial oscillations. The main property of radial oscillations is the dependence of the relative velocity of the formation matrix and formation fluid on the permeability of the porous medium at the interface between the media. Measuring the relative velocity at the interface between the media on the borehole side, one can use this dependence to calculate formation permeability. In the presence of mudcake, relative velocity dependence on permeability is retained, but only between the formation and mudcake, which cannot be measured directly on the side of the "mudcake-borehole fluid" interface. However, because the relative velocity in the formation beyond the borehole retains its dependence on permeability, it serves as a means of effective attenuation of borehole fluid waves. This can also serve as a tool for measuring formation permeability in the presence of mudcake and seems to be the foundation for numerical attenuation studies of the Stoneley waves and radial waves in the presence of mudcake. Therefore it should be noted that the influence of mudcake on the Stoneley waves was investigated by Liu, Maximov, etc. [Liu, Johnson, 1997; Maximov, Merkulov, 2002] drew the conclusion based on the theoretical analysis within the framework of the Biot theory that mudcake appears to reduce the influence of permeability on the attenuation length of the Stoneley waves.
Fluid Mechanical Aspects of Wet Gas Metering
Authors: Gryzlov A. , Nyfors E. , Jordaan L. , Undheim E. , Braaten N. A. , Gregersen S. E. , Steinsland E.
Published: October 2012

Current trends in hydrocarbon production are driven by improved oilfield management with various control and optimization strategies. These strategies rely on the efficiency of monitoring equipment which is used to obtain real-time oil and gas production rates with sufficient spatial and temporal resolution. Consequently considerable efforts have been put in the development of reliable flow measurement techniques dedicated to real-time monitoring of hydrocarbon flow rates without separation of the phases.

Multiphase metering at an upper limit of gas volume fraction (mostly above 95% GVF) is referred to as wet gas metering. Usually the metering of a wet gas flow is performed using standard dry gas meters which are supplemented by additional corrections in order to account for the impact of a liquid phase. These correction algorithms use explicit information on the measured fractions of oil, water and gas and can either be based on empirical correlations or employ mechanistic flow models. In contrast, issues related to installation effects of various components (such as pressure/temperature gauges and ad-hoc sensors) cannot usually be handled using simple flow models and should be assessed using extensive experimental analysis.

As a general solution, more fundamental physical background is put into the design and development of a new generation of a wet gas meter. The usage of general flow models both on micro and macro scales reduces uncertainty relevant to empirical modelling and promises more robust flow metering performance. In this work, the issues related to the optimal salinity sensor location have been studied via computational fluid dynamics. In particular, different variants of sensor placement scenarios have been analyzed in order to identify the location, which will have the maximum water volume fraction to achieve as high sensitivity as possible.
Preventing Annular Water Flow in Primary Cement Jobs Utilizing Swellable Packers
Authors: Takhodinov S. F. , Ibragimov N. G. , Khisamov R. S. , Ibatullin R. R. , Mitchell R. K. , Davis T. W.
Published: October 2012

Cement has been the main form of annular zone isolation for oil well construction since the beginning of the industry. It is a science in its own right comprised of technical experts continually improving materials and processes. Often the failure of cement to achieve zonal isolation can be traced to the lack of best practices. When the cement does not provide required annular isolation, the result can be one of the following: Excessive water productionLost production from cross flowGas migration revealed as sustained casing pressure / sustained casing flowContamination of shallow water zones

Excessive water production diminishes the value of an asset and results in extra capex/opex for remedial operations. It can also result in delayed oil production. By concentrating on the zonal isolation process during the completion phase, many zonal isolation issues can be mitigated. A detailed evaluation of the cement program can highlight areas of improvement in both materials and operations. This is especially critical for areas where there are multiple stacked productive zones (oil on water) and varying reservoir pressures. An approach to improve annular integrity and the overall cementing process is the use of swellable packers. This practice has become more commonly accepted over the past few years.

This paper will discuss the best practices adopted to mitigate water production up to the time of implementing swellable packers followed by the additional improvement achieved by including swellable packers with the best practices.
Drilling Support Center -in its True Sense - A Russian Operator Experience
Authors: Bakici Ali M , Sarkisov Ivan I , Garifullin Azat A , Aker Gokhan H
Published: October 2012

Operators and service companies are considering alternative methods to remedy shortage of qualified and experienced staff to manage increasing activity and complexity. TNK-BP's approach has been creation of Drilling Support Center (DSC) as part of upstream peer review and technology center in Tyumen. The Company has eleven subsidiaries spread across Russia, and operations are managed by 6 regional drilling teams. DSC is centrally located to ensure geographical coverage of both eastern and western regions, with a mission to improve drilling performance, as well as support new technology implementation.

Main drivers for creating DSC were: –Increasing complexity of wells and wide geographical spread,–Limited drilling personnel with experience and expertise,–Commencing international operations requiring central support,

The center currently provides support in three main directions; firstly, monitoring complex and critical operations using realtime link from rigs by experienced staff with relevant expertise, including regular contact with operations teams to provide proactive feedback. Second direction is engineering support to well planning and new technology implementation by experienced specialists in directional drilling, cementing, drilling fluids, completions and drillbits. Third direction is Geosteering support of horizontal wells including real-time update of sector models. The center is active over a year now and subsidiaries regularly contact DSC for critical operations review.
Reducing the Loss of Energy in Transport Pipeline for Viscous Oil
Authors: Radulescu Renata , Sin Marius C. , Clain Bogdan M.
Published: October 2012

The variation of temperature over a pipeline has a major influence over viscous oil pumping.

Viscous oil transportation in non-isothermal regime, through buried pipelines, is a flow process in which intensive energy exchanges occur. Heated oil loses heat in the environment where the pipeline is assembled, but at the same time due to its friction with the pipeline's walls and to dissipated viscosity which produces in turbulent flow mechanical energy, this turns into heat.

Given such a context, the purpose of the paper is to assess the efficiency of oil transportation in non-isothermal state, and in order to achieve it we will make use of the entropic analysis of the process. Entropy is a state measurement of the process that enables the analysis of energy loss.

Entropy generation during a process is directly proportional to the available lost power.

We will show the dynamic variation of pressure and temperature in the transport process, the analysis of hydrodynamic and heat losses, as well as the entropic analysis.
Fracturing Completion System Optimization through Advanced Hydraulic Modeling
Authors: Deshpande K. M. , Simpkins D. , Gandikota R. , Ring L.
Published: October 2012

Openhole, multi-stage fracturing systems are commonly used today in many applications, including unconventional shale gas reservoirs. As many as forty stages have been successfully completed in a single horizontal well and the industry is aiming even higher. One problem that has a major impact on job success is the ability to accurately calculate maximum pump rates for a given surface pump pressure. When frac fluid is pumped through a downhole multi-stage fracturing system, each time a new stage is completed, the flow splits at different sleeves in the completion string.

To determine minimum surface pump pressure and maximum pump flow rate, predicting split flow rate and the resulting pressure loss at each stage is essential. Traditionally, laboratory tests and field experience are used to predict these values. However, these types of predictions are not possible for hydraulic fracturing jobs that use a multiple sliding sleeve system, as is commonly employed. To simulate the hydraulic fracturing process, the Computational Fluid Dynamics (CFD) approach has been used, as it is a proven methodology. However, extensive CFD analysis requires computational overhead and significant software and hardware costs.

This paper presents a methodology which combines CFD and theoretical approaches to calculate split flow rate and pressure loss for non-Newtonian frac fluids in a multiple sliding sleeve system. These methods are incorporated into the multiple sliding sleeve design process and hydraulic fracturing plan optimization. The method can also be extended as a general solution for calculating pressure loss due to split flow.
IT Governance and Organization in Smart Oil Fields
Authors: Guldemond Ewoud , Acda Léon , Andronov Mikhail
Published: October 2012

Several major oil companies have brought in specific Information Technology (IT) to implement the Smart Oil Fields concept in practice. They did so to reduce costs, to increase productivity and for recovery purposes. However, implementing IT for Smart Oil Fields does not automatically imply that you have actually implemented a Smart Oil Field with all its benefits. Alignment of the IT to the specific business needs is often lacking. In order to successfully operate Smart Oil Fields, and getting most of the value, oil companies need to have an adequate IT Governance and Organization framework in place, which bridges the gap between business and IT.

In order to develop such a framework, a PhD research was conducted at three different Operating Units of a major oil company. The research focused on the organizational structure of oil production locations, which had already implemented Smart Oil Fields. During our field research, interviews with staff & management were conducted, company documents were analyzed and observations were made.

We combined our research findings with our project experience on IT Governance and Organization in major oil companies in The Netherlands, Russia and South America. Our research findings combined with our project experience has resulted into an integrated, hands-on IT Governance and Organization framework for oil & gas companies who are implementing or planning to implement Smart Oil Fields operations.
Operational Performance Analysis of Mature Oilfields
Authors: Turchin Sergey
Published: October 2012

Analysis of field performance is a critical step in improving the production efficiency and optimizing the cost of operations. However, existing methodologies of analysis have limitations, particularly in the size of the analysis set and the inability to compare different types of assets. The new methodology was designed to overcome these limitations.

This paper explains the methodology of field performance assessment and shares some high-level results of the analysis. Operational performance is compared with results within a peer group. It allows the operator to obtain insightful information on how to improve the efficiency and reliability of production operations. The methodology is characterized by high quality performance indicators – the large amounts of data were collected from the operators and public sources, including cost, production, and technical field data. The detailed analysis is conducted for 12 standard operating cost classifications across seven oil and two gas peer groups, based on similar geological and operational characteristics. The methodology focuses on operations cost performance, production efficiency and production reliability performance, efficiency and cost driver analysis, and gives a suggested action plan. The paper also demonstrates how the results may be utilized to improve efforts by operators in the environment of mature oil fields with declining production levels.

The described methodology was applied to an analysis of the Permian Basin, which contains a large number of maturing oil fields. The study assessed 90 fields, including 35 waterfloods, 20 primary, 15 tertiary, and 20 gas fields for the period of mid-year 2010 to mid-year 2011. Trends and correlations between production efficiency and cost driver factors were found. This led to the issuing of recommendations to the producers.

The proposed methodology can be applied to an analysis of the operations performance of mature oilfields in Russia, which will result in low operating costs and higher production volumes.