bluuebunny/crossref_metadata_2025 huggingface dataset:
O methohexital sódico (Brevital®) no teste de Wada: relato de dois casos
Authors: Rocha Samanta F. Blattes da , Meneses Murilo S. , Kowacs Pedro A. , Simão Cristiane , Larocca Heraldo , Hunhevicz Sonival C.
Published: June 2012

RESUMO INTRODUÇÃO: O teste de Wada® continua sendo um exame freqüentemente utilizado, para a avaliação qualitativa e quantitativa da lateralidade das funções de linguagem e das funções de memória verbal, e do possível déficit residual, uma vez que simula o efeito da cirurgia na investigação pré-operatória de candidatos a lobectomia temporal. No Brasil, há consideráveis dificuldades impostas pelas autoridades sanitárias para obtenção do Amytal® (amobarbital sódico). OBJETIVOS: Descrever o protocolo do teste de Wada realizado com Brevital® (methoexital sódico) em dois candidatos a lobectomia temporal, comentar sua eficácia e suas diferenças em relação ao realizado com o Amytal®. MÉTODOS: Relatamos o uso do Brevital® em dois pacientes submetidos a determinação da lateralidade da linguagem e da memória através de protocolo adaptado para tal. RESULTADOS: O Brevital®, um anestésico de ação curta, mostrou-se eficiente em ambos os casos como substituto ao Amytal®. CONCLUSÕES: O Brevital® pode ser utilizado no Brasil para a realização do teste de Wada, com a vantagem de possibilitar um exame mais breve, assim como uma investigação abrangente das funções de memória.
A disfunção do lobo frontal em crianças e adolescentes com epilepsia de lobo temporal e sua possível correlação com a ocorrência de transtornos psiquiátricos
Authors: Rzezak Patrícia , Fuentes Daniel , Guimarães Catarina A. , Guerreiro Marilisa , Valente Kette D. R.
Published: June 2012

Introdução: Há evidências de que pessoas com alguns tipos de epilepsia podem apresentar prejuízos cognitivos, sendo que para alguns pacientes, tais déficits cognitivos podem ser mais debilitantes do que suas crises epilépticas. A disfunção do lobo frontal é relatada em adultos com epilepsia do lobo temporal, caracterizada pela disfunção executiva. Objetivo: Rever a literatura sobre a ocorrência de disfunção de lobo frontal em crianças e adolescentes com epilepsia do lobo temporal. Métodos: Revisão sistemática da literatura compulsada no PUBMED. Resultados: A disfunção do lobo frontal tem sido pouco estudada em crianças com epilepsia, em especial com epilepsia do lobo temporal. No único estudo sobre este assunto, demonstrouse que há um déficit executivo, sendo que as crianças com esclerose mesial têm maiores déficits de execução/ planejamento do que aquelas com lesões neocorticais temporais ou frontais. A presença de uma disfunção do lobo frontal nos pacientes com epilepsia parcial e generalizada pode corroborar as evidências de que epilepsia e transtorno psiquiátrico são epifenômenos e não fenômenos com relação causa efeito. Conclusões: Há uma escassez de artigos sobre a disfunção do lobo frontal em crianças com epilepsia do lobo temporal, sendo de interesse saber se esta ocorre e se pacientes com etiologias distintas apresentam diferentes graus de comprometimento destas funções.
Dissociação entre alterações de linguagem e preservação da musicalidade em uma criança com epilepsia refratária
Authors: Fontoura Denise Ren da , Tisser Luciana , Espírito Santo Júlia Lima do , Portuguez Mirna Wetters , Palmini André
Published: June 2012

Introdução: Estabelecer uma relação entre epilepsia e linguagem é uma tarefa bastante complexa, visto que existem muitas variáveis envolvidas. Dessa forma, podem ocorrer alterações de linguagem expressiva e compreensiva, e em alguns casos a preservação da musicalidade e da prosódia podem estar presentes. Objetivos: O objetivo deste estudo foi descrever o caso de uma criança com crises epilépticas refratárias multifocais que mostrou uma intrigante dissociação entre o comprometimento de funções de linguagem e a preservação da musicalidade. Métodos: Relato do caso de um menino de 9 anos, internado no Programa de Cirurgia de Epilepsia (PCE) do Hospital São Lucas (HSL) da PUCRS, em novembro de 2004, por apresentar crises epilépticas refratárias. Foram realizados exames clínicos, neurofisiológicos, de neuroimagem e avaliação neuropsicológica. Resultados: Os aspectos lingüísticos do paciente caracterizam uma disfasia, com alterações significativas de expressão e de compreensão da linguagem oral (lobo temporal esquerdo), mas adequação nos aspectos prosódicos da fala e do canto (hemisfério direito). Além disso, a avaliação mostrou um importante atraso global de desenvolvimento neuropsicomotor e alterações comportamentais. Conclusão: Os dados deste trabalho evidenciam a interferência da epilepsia refratária na infância nas habilidades cognitivas, sendo o foco epileptogênico determinante nas alterações lingüísticas. Ressalta-se a importância da avaliação neuropsicológica para mensurar alterações provenientes desta patologia, assim como, identificar áreas da linguagem preservadas, como a musicalidade neste caso, permitindo um elo de ligação para comunicação, avaliação e reabilitação cognitiva.
Mesial temporal lobe epilepsy syndrome: an updated overview
Authors: Cendes Fernando
Published: June 2012

Mesial temporal lobe epilepsy (MTLE) is the most common form of partial epilepsy in young adults and also the most frequent type of epilepsy reported in surgical series worldwide. Mesial temporal lobe sclerosis (MTS) is the major underlying cause of MTLE, and it is present in 60-70% of patients with MTLE who undergo surgery for treatment of medically refractory seizures. Pathogenetic mechanisms underlying this distinct hippocampal pathology remains undetermined. Recent findings suggest a developmental malformation of hippocampus (inherited or acquired) that in association with subsequent injury (e.g. trauma, infection, complex febrile seizures) could develop ongoing seizures, resulting in the full-blown neuropathological features of MTS. Genetic background, age and type of initial precipitating injury, and vulnerability related to programmed cell death pathways are probable mechanisms involved in the development of MTS. Definitions for medical intractability may vary among centers, but usually include failure to achieve seizure control with two or more AEDs with adequate dosage and posology. The decision as to when one should perform surgery in patients with MTLE is a relevant issue that needs more investigation. Recent evidence discussed in this review indicates that longer duration of uncontrolled seizures is associated with an increased risk of unsuccessful surgery.
Determining Gas Flow Rate and Formation Thermal Conductivity from Pressure and Temperature Profiles in Vertical Well
Authors: Barrett E. , Abbasy I. , Wu C. R. , You Z. , Bedrikovetsky P.
Published: June 2012

The gas flow rate and the formation thermal conductivity distributions along the gas well have been determined from the measured pressure and temperature profiles using production logging tools, which is much cheaper and more precise than the traditional procedures of direct flow metering. An effective and robust method is proposed in this work: the system of governing equations for non-isothermal gas flow in vertical well is solved using the Runge-Kutta method; then the flow rate and formation thermal conductivity are obtained by optimising the modelled profiles of pressure and temperature based on the measured profiles. Application of the algorithm to field case shows good agreement between the directly measured and modelled pressure and temperature profiles; the flow rate prediction is consistent with flowmeter (PLT) data; the thermal conductivity profile is also in a good agreement with that obtained from lithology log. It validates the proposed method.
GPU-based Parallel Reservoir Simulation for Large-scale Simulation Problems
Authors: Yu Song , Liu Hui , Chen Zhangxin John , Hsieh Ben , Shao Lei
Published: June 2012

Reservoir simulation for a full field heterogeneous model with millions of grid blocks demands significant computational time so improving the computational efficiency becomes crucial in designing a reservoir simulator. Graphics Processing Unit (GPU), a new high-profile parallel processor with hundreds of microprocessors, stands out in parallel simulation because of its efficient power utilization and high computational efficiency. Also, its cost is relatively low, making large-scale parallel reservoir simulation possible for most of desktop users.

In this paper several GPU-based parallel preconditoners, in conjunction with a new GPU-based GMRES algorithm, are proposed and coupled with an in-house black-oil simulator to speedup reservoir simulation. In particular, massively parallel ILU preconditioners (ILU(0), ILUT, block ILU(0), block ILUT), which are usually regarded as data dependence and highly sequential preconditioners, are developed on GPUs.

In the numerical experiments performed, the SPE 10 problem, a 3D heterogeneous benchmark model with over one million grid blocks, is selected to test the speedup of our GPU solver and preconditioners. On the state-of-the-art CPU and GPU platform, the new GPU implementation can achieve a speedup of over eight times in solving linear systems arising from this SPE 10 problem compared with the CPU based serial solver. Moreover, our GPU solver is successfully coupled with the in-house black-oil simulator to test the performance of the whole parallel simulation process, with a speedup of about six times. The excellent speedup and accurate results demonstrate that the GPU-based parallel linear solver and preconditioners have the great potential in parallel reservoir simulation.
Challenges in High Performance Computing for Reservoir Simulation
Authors: Hayder Ehtesham M , Baddourah Majdi
Published: June 2012

High resolution reservoir modeling is necessary to analyze complex flow phenomena in reservoirs. As more powerful computing platforms become available, reservoir simulation engineers are building larger and higher resolution reservoir models to study giant fields. Large number of simulations is necessary to validate the model and to lower uncertainty in prediction results. It is a challenge to accurately model complex processes in the reservoir and also efficiently solve high resolution giant reservoir models on rapidly evolving hardware and software platforms. There are many challenges to get high performance in reservoir simulations on constantly evolving computing platforms. There are constraints which limit performance of large scale reservoir simulation. In this study, we review some of these constraints and show their effects on practical reservoir simulation. We review emerging computing platforms and highlight opportunities and challenges for reservoir simulation on those platforms. It is anticipated that management of data locality by the simulator will become very important on emerging computing platforms and there will be needs to manage locality to achieve good performance. Heterogeneity in the computing platform will make it difficult to get good performance without adoption of a hybrid parallelization style in the simulator. In this study, we analyze many benchmark results to illustrate challenges in high performance computations of reservoir simulation on current and emerging computing platforms.
Risk Evaluation Technique for Tubing-Conveyed Perforating
Authors: Baumann Carlos , Dutertre Antoine , Martin Andy , Williams Harvey
Published: June 2012

This paper presents one application of a simulation tool that predicts tubing-conveyed perforating gunshock loads reliably. The tool enables completion engineers to evaluate the sensitivity of gunshock loads to changes in gun type, charge type, shot density, tubing size and length, rathole length, use of shock absorbers, and placement of packers, among others.

The simulation tool described in this paper helps engineers to identify perforating jobs that have a risk of gunshock related damage, such as bent tubing and unset packers. When predicted gunshock loads are large, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads and the associated risks.

Comparisons between predicted wellbore pressure and actual fast-gauge pressure data are available in related SPE articles. These comparisons show that predicted wellbore pressure transients are very reliable both in magnitude and time. Peak sustained pressure amplitudes at the gauges are on average within 10% of software-simulated values. For cases where shock absorbers were used, residual deformations of crushable elements correlate well with the peak axial loads predicted by the software. The software is able to simulate perforating job designs in a short time, which allows engineers to optimize perforation jobs by reducing gunshock loads and equipment costs.

The ability to predict and reduce gunshock-induced damage in perforating operations is very important because of the high value of typical wells. With the software tool described in this paper engineers can optimize perforation jobs by minimizing the risk of gunshock-related damage and the associated non-productive time (NPT).
The Adaptive Well Log Data Interpretation in Geological Modeling
Authors: Kozhevnikov D. A. , Kovalenko K. V. , Deshenenkov I. S.
Published: June 2012

Widespread application of 3D geological modeling in oil and gas field development practices resulted in substantiation of the transition from the traditional concept of "absolute pore space?? to the concept of "effective pore space??. This could be achieved with the geophysical and well logging data interpretation algorithms and procedures focused on the determination of reservoirs dynamic characteristics with high vertical resolution and based on principles of adaptability and petrophysical invariance.

The adaptive log data interpretation technology provides analytical relations between log interpretative parameters and reservoir rocks properties in the generalized form. Proposed interpretative algorithms are implemented in the geological modeling software package and combined with standard geological modeling procedures to develop the three-dimensional distribution of reservoir properties.

Adaptive petrophysical models make possible the quantitative estimation of effective porosity and effective/phase/relative permeability. Formation parameters, which characterize the content of bound water in the framework and cement, maximum total porosity and effective porosity. Dependencies between effective porosity and effective permeability are estimated according to outcomes of petrophysical modeling. Effective porosity is calculated with the interpretation of standard log data. The distribution of reservoir properties in three-dimensional space is carried out with geostatistical simulation techniques. Application of effective porosity for prediction of relative permeability and capillary pressures with log data was realized as an important task for field development design.

The test of the proposed technology is conducted on a large number of wells worldwide (Western and Eastern Siberia, Caspian region, Middle East, Alaska, etc.). Formations consist of clastic fine-grained sandstones with cement and framework complex mineral composition. Application of proposed technology in geological modeling software packages represents an innovative direction of geological information technologies. It does not require any special capital expenditure with a significant economy of forces and operational time.
Will Gas Hydrate Lying On Oceanic Floors In India Solve Its Energy Problem? A Futuristic Approach
Authors: Jha Ashutosh Kumar , Bansal Gopal , Joshi Abhishek , Sangwai Jitendra Shital
Published: June 2012

India with the largest gas hydrate deposits in the world have potential of being the biggest global producer of NGH (a solidified form of gas lying on oceanic floors). 1.08 trillion cubic metres of the proven conventional natural gas reserves in India is around 1700 times less than the prognosticated gas hydrate resources of 1,894 trillion cubic metres lying in the deep water regions. Even the extraction of minor fraction of this resource can be the energy hunters for decades.This paper discusses the geological and geophysical aspects of marine gas hydrate distribution in India. Through a wide literature survey authors have shown the hurdles which are imposing constraints on the wide scale extraction of natural gas from NGH. The Indian exploration strategies to identify and quantify the gas hydrates by various seismic tools (e.g. seismic reflectors coincidence with the base of the gas hydrate stability zone (BGHSZ)) with its limitations are described in lucid manner. Also, the technical advancements are presented to eliminate the mentioned limitations. Well- based extraction technology (a drilling program) is discussed for safe and economically viable production of gas from gas hydrate reservoirs.India's 7500 km of coastline having a vast fuel reserve in the form of NGH can be a next generation energy source if mature extraction technology is developed to extract the gas from gas hydrate reservoirs.
A Comparative Studies and a Sensitivity Analysis for a Heavy-Oil Reservoir in GCC Region
Authors: Alajmi Haifaa , King Peter
Published: June 2012

In this paper we are continuing our previous works (SPE-143142 and WHOC11-353) to investigate the best development options for a major heavy oil reservoir within the GCC region. In the early stage of this work the most applicable EOR methods were selected, and several simulation runs were conducted to find the optimal injection scenarios and rank them based on the oil recovery factor (ORF). In this paper a comparative study and a sensitivity analysis of various operational conditions and reservoir parameters were conducted in order to (1) find the optimum conditions to achieve a high RF and (2) understand the effect of reservoir heterogeneity on the reservoir performance. The investigated operational parameters are the Steam injection rate, injection swapping time and the perforation location. The investigated reservoir parameters are oil viscosity, initial water saturation, porosity and permeability. In addition to investigating these reservoir parameters, the oil price sensitivity was investigated to evaluate the financial feasibility of the selected recovery methods within a historical and forecasted oil price range.

The preliminary results show that the RF is very sensitive to the oil viscosity value and the relation between them is a nonlinear relation. The Simulation results also indicate that the increase in the porosity and permeability accelerates performance; however, the opposite is not true for the initial water saturation value. From an economic perspective, production acceleration would improve overall project economics by mitigating the negative impact of discounting on the revenue stream due to the low oil price. Economically, all successive scenarios support a successful investment at the lowest (expected) oil price; in contrast, the continuous steam and hot-water flooding development options show a high economic risk after the second year, at all oil price scenarios.
Building Trust in History Matching: The Role of Multidimensional Projection
Authors: Hajizadeh Yasin , Amorim Elisa Portes , Costa Sousa Mario
Published: June 2012

Assisted history matching frameworks powered by stochastic population-based sampling algorithms have been a popular choice for real-life reservoir management problems for the past decade. These methods provide an ensemble of history-matched models which can be used to quantify the uncertainty of future field performance. As a critique, population-based algorithms are generally considered black-boxes with little knowledge of their performance during history matching. In most cases, the misfit value is used as the only criteria to monitor the sampling algorithms and assess their quality.

This paper applies three recently developed multidimensional projection schemes as a novel interactive, exploratory visualization tool for gaining insights to the sampling performance of population-based algorithms and comparing multiple runs in history matching. We use Least Square Projection (LSP), Projection by Clustering (ProjClus) and Principle Component Analysis (PCA) to examine the relationship between exploration of search space and the uncertainty in predictions of reservoir production. These projection techniques provide a mapping of the high dimensional search space into a 2D space by trying to maintain the distance relationships between sampled points. The application of multidimensional projection is illustrated for history matching of the benchmark PUNQ-S3 model using ant colony, differential evolution, particle swarm and the neighbourhood algorithms.

We conclude that multi-dimensional projection algorithms are valuable diagnostic tools that should accompany assisted history matching workflows in order to evaluate their performance and compare ensembles of history-matched models. Using the projection tools, we show that misfit value - as an indicator of match quality - is not the only important factor in making reliable predictions. We demonstrate that exploration of the search space is also a critical element in the uncertainty quantification workflow which can be monitored with multidimensional projection schemes.
Pressure Transient Analysis in Multiphase Multi Layer Reservoirs with Inter Layer Communication
Authors: Nikjoo Ehsan , Hashemi Abdolnabi
Published: June 2012

The focus of this study is on the investigation of multiphase flow effects on the pressure transient analysis in layered reservoirs with cross flow. Virtually all studies on the subject of multiphase well test analysis have been carried out in single layer reservoirs. However, many reservoirs are found to be composed of number of layers whose characteristics are different from each other and the wells in such reservoirs may be completed and produced from more than one layer.

A novel technique is proposed based on replacing multi-phase multi-layer reservoirs with cross flow with an equivalent single phase single layer reservoir. To validate the proposed method, several reservoirs with different saturations were studied numerically and were compared with the results of the proposed model. The reservoir parameters such as phase mobilities, skin factor and average reservoir pressure are compared with actual values. It was found that reservoir parameters can be obtained accurately with the equivalent single phase single layer model. However, care should be exercised when horizontal saturation gradient is significant.
A New Approach To Fracturing And Completion Operations In The Eagle Ford Shale
Authors: Fulks Robert , Smythe Steve
Published: June 2012

Completions and multizone fracturing operations in the Eagle Ford Shale are complex undertakings. Effectively managing hydraulic fracturing projects becomes even more complex when multiple service providers and suppliers are required to work in a coordinated sequential fashion. By late 2009 daylight completions work in the Eagle Ford evolved into 24 hour a day operations to maximize asset availability – primarily hydraulic horsepower.

Completions were accomplished in fewer days using the 24 hour approach, but efficiencies and safety suffered. However, a select group of Eagle Ford operators were concerned with the drop in performance. These operators chose to adopt an integrated services approach where one service company provided the majority of equipment and personnel on completions jobs. This new approach achieved both fewer days per completion and high KPI efficiency (e.g. stages per day, fewer safety incidents, etc.) as well as improving communication and teamwork. An explanation of this new approach is detailed here.
Vector Scanning: Hydro-fracture Monitoring With Surface Microseismic Data
Authors: Ma Licheng , Wang Lei , Shen Yiping , Zhou Yongsheng , Liang Beiyuan
Published: June 2012

For monitoring hydraulic fracture (HF) in oil/gas fields the most reliable seismic method to avoid the adverse effect of strong surface noises is using downhole microseismic surveys. Nevertheless, downhole measurement is more expensive and limited by the availability of suitable boreholes in the vicinity of the hydro-fracture site.By all means seismic surveys conducted on land surface bear the largest flexibility and are more economic than downhole measurements. As a significant progress in hydro-fracture monitoring Duncan et al developed a surface monitoring system using seismic arrays centered at the hydro-fracture point. This monitoring method requires large-scale and prolonged operations; thus the cost-effectiveness is still less than ideal. In this paper we present a novel approach for land monitoring of hydro-fractures that uses only sparse seismic stations far from fracturing vehicles; and the total number of seismic stations is much less than previous approaches; so that the cost-effectiveness is significantly improved. With a small-scale seismic array on land surface we have monitored the hydro-fracture processes using a vector scanning technique for imaging hydro-fractures and determining rupture focal mechanisms. The applications of this technique to a synthetic data set based on numerical modeling and the real-world field data show that it is able to trace the tempo-spatial development of hydro-fractures even when the signal to noise ratio (S/N) is lower than 0.5. The vector scanning technique significantly shows the fracture imaging quality, and provides us a costeffective approach for monitoring flow-enhancement hydro-fracture processes.
In-Depth Evaluation of Deep-Rock Hydrajet Results Shows Unique Jetted Rock Surface Characteristics
Authors: Stockhausen Harald W. , García Sanchez Daniel G. , Luongo Sergio A. , Surjaatmadja Jim B. , Loghry Ray A.
Published: June 2012

The use of hydrajetting for perforating of wells has been commonplace since the 1960s. During those early years, wells were relatively shallow, and jetting success was consistently demonstrated. However, as wells became deeper, where rock formations tend to be harder, hydrajetting performance became less dependable; subsequently, stimulation failures more often occur as a result of the lack of fracture initiation.

To remedy this situation, a series of tests were performed to define new best practices for hydrajet perforating of hard rock under high ambient pressure environments. Various rocks were subjected to these tests, which were performed using different jetting pressures and different abrasives. The perforation surfaces were then dissected and evaluated using photographic and chemical means. Further assessments were then made to determine what actually occurred during the hydrajetting process.

This paper discusses various test results, and new constraints for hydrajetting are defined and presented.
Condensate Recovery from a Fractured Carbonate Field
Authors: Paraschiv Catalin , Abdev Joseph , Clemens Torsten
Published: June 2012

Fractured reservoirs are characterised by a large difference in permeability of the fracture and matrix system. Usually, the matrix contains the bulk of the hydrocarbons while the fractures are the flow paths. These characteristics are challenging for projects aiming at increasing hydrocarbon liquid recovery from gas condensate fields by gas injection. While in fractured oil reservoirs capillary forces (imbibition) or gravity forces can be utilised to improve oil recovery, for gas injection into gas condensate reservoirs, these forces are less important.

The recovery mechanisms were investigated using the properties of a rich gas condensate field located in the Middle East. A fine grid sector simulation model was created in which the fractures and matrix were introduced explicitly.

Without taking diffusion into account, the injected gas breaks through at the producer very fast. The concentration in the produced gas is closely linked to the effective permeability of the fracture divided by the effective permeability of the matrix.

However, taking diffusion into account, the increase in injected gas concentration is much slower. The speed of the increase (for the same pore volume injected) depends on matrix porosity, velocity of the front, fracture spacing and permeability contrast.

The molecules of the injected gas are diffusing into the matrix while the components of the reservoir gas are diffusing towards the fracture. The various components have different diffusion coefficients. Dependent on the injection gas, the dew point pressure in the matrix can be reached (despite the reservoir pressure being constant) and condensate drops out. Hence, the condensate recovery depends on the injected gas.

The results of the study show that neglecting diffusion in fractured reservoirs can result in errors in the condensate recovery of more than 50 %. In addition, the shape of the condensate recovery curve will be incorrect if diffusion is not accounted for.
Predicting water in the crest of a giant gas field: Ormen Lange Hydrodynamic Aquifer Model
Authors: Boya Ferrero M. , Price S. , Hognestad J.
Published: June 2012

Hydrodynamic aquifer conditions have been described in many basins around the world since first introduced by Hubbert1 in 1953. The hydrodynamic aquifer concept in Ormen Lange has been assessed using iso-potential mapping1 and dynamic simulation of the fluid fill development (i.e. imbibition) over geological time. Simulation shows2,3 the hydro-dynamically tilted/stepping contacts depend on rate of water flow across the aquifer, stratigraphic baffling and faulting, effective aquifer area and reservoir quality (NTG and effective permeability). The role of sealing faults over geological time scale is downplayed in terms of justifying the fluid distribution. Baffling during production is, however, expected. In Ormen Lange the hydrodynamic aquifer has pushed the gas from the crest of the structure into the south of the field leaving behind a northward-thickening prism of residual gas which is imaged by a seismic DHI. Confirmation of the hydrodynamic aquifer scenario in this field was achieved after drilling an appraisal well in the north of the structure that corroborated fluids (water with residual gas) and pressures as prognosed by the hydrodynamic aquifer model.
New Data Retrieval Application Significantly Improves Asset Management in Digital Oilfields with Intelligent Completions
Authors: Allen Cifford , Smith Robert
Published: June 2012

In digital oil fields in which intelligent completions are used, information that can be provided by the intelligent completion technology is increasing in importance, as intelligent well completions can minimize the need for additional custom data-gathering solutions. Thus, industry-data interfacing standards for multiple devices and systems can be reduced. For assets using intelligent completions, solutions are attained by a combination of subsurface and surface or subsea sensors provided by several vendors.

Challenges arise when attempting to manage the interfaces required for providing real-time data from all points of interest (i.e., subsurface choke positions, flow, pressures and temperatures, wellhead positions, subsea facility readings, etc.). The design and implementation of an integrated data-applications system that can integrate data from multiple workflow sources for the purpose of maximizing field performance is the focus of this paper. The asset optimization applications acquire operating parameters from all points of interest, making them available to software modules designed to estimate key wellperformance indicators.

The asset-optimization application discussed here is an integrated system that performs five services: A data-interfacing methodology acquires data from multiple sources or directly from downhole devices.The integration service converts the subsurface and surface data to engineering units of measured well parameters.The well performance service uses well PVT and device-integration service values to execute complex calculations, like virtual flow metering, water-cut estimates, etc.The human/machine/interface service provides visualization, trending, and querying.The connectivity service facilitates structured data transfer to field historians.

The paper will explain how the system works and its implementation into fields of different scales and types to reduce information technology (IT) customization, simplify interfacing of multiple devices or systems, and accommodate evolutions in IT. Additional system benefits that include more efficient management of real-time data security, quality, redundancy, and mirroring will also be provided.
Understanding Uncertainties in Deepwater Depositional Facies Modeling for Better Reservoir Conditioning
Authors: Chen Jiajie (Jeff)
Published: June 2012

In deepwater reservoir modeling, the proportions of various facies being modeled have a significant impact on the distribution of reservoir properties, total reserve, reservoir connectivity, and hence recoverable reserve. Generally, facies modeling can be achieved by deterministic or stochastic approaches, or a combination of both. When seismic data have sufficient quality or resolution, the data may serve as certain reservoir property indicators, and the approach for facies modeling can be more deterministic. When seismic data are not available or do not have sufficient resolution, a stochastic approach is usually needed. In either case, the uncertainties in facies distribution must be fully assessed. This paper presents a case study and workflow in which different sand-shale proportions (more optimistic, basic, and less optimistic) are considered in facies modeling, in order to investigate the range of deepwater turbidite facies distribution and its effect on reservoir property variations. The facies models are constructed by different methods, including deterministic, stochastic, and a combination of both. Comparison of the deterministic and stochastic models provides certain insight into the distribution of depositional facies. Further, in each facies scenario, the range of reservoir property distribution is assessed. In addition, for different reservoir zones, the ranges of oil-water contacts are incorporated in the reservoir model. As a result, the entire spectrum of in-place hydrocarbon volumes is captured, and various stacking patterns as well as connectivity issues can be conditioned in the simulation model, leading to a more robust understanding on the resource to be developed.
Reducing the Dimensionality of Geophysical Data in Conjunction with Seismic History Matching
Authors: Rezaie Javad , Sætrom Jon , Smørgrav Eivind
Published: June 2012

Seismic history matching (HM) has attracted increasing attention the last few years. As more repeated seismic surveys are acquired, the more apparent the shortcomings in modern HM tools and algorithms become. A common conception seems to be that the amount of data represented by geophysical observations and the complexity of working with 3D fields make the updating procedure hard. We investigate the nature of geophysical observations from a HM point of view by testing several data reduction techniques such as Principal Component Analysis (PCA), regression techniques such as forward stepwise, as well as state-of-the-art techniques based on neural networks. We argue that simulated geophysical fields from the prior models are prone with spatial correlations and that their information content and effective dimensionality is much smaller than the dimensionality of the observed field. The techniques are tested on a reservoir model of an anonymous North Sea oil field, using the seismic time shift, i.e. the difference travel time integrated over the reservoir between two surveys. We find that PCA is particularly promising, resulting from the versatility and robustness of the method. In practice this means that high dimensional geophysical data, e.g. 2-D seismic images or 3-D seismic cubes, can often be described using only a handful of scalars. We show how to assess the information content in the data, compress the data, and use this compressed data in a reservoir conditioning setting. The methods we present are generic; they apply equally well to all geophysical attributes regardless of representation and can be applied with any history matching algorithm, although they are mainly designed for ensemble based techniques.
Simulation of Drilling Fluid Filtrate Invasion Near an Observation Well
Authors: Chassagne Romain L. , Hammond Paul S.
Published: June 2012

We used a commercial reservoir simulator to study first the dissipation of aqueous drilling fluid filtrate invasion around a cased observation well in an oil-saturated formation under the action of capillary pressure, and then the interaction of a waterflood front with the cased well and remaining invaded zone. Hysteretic behavior of the capillary pressure and relative permeabilities is critically important to these processes and is taken into account using the Killough model, with the various bounding drainage and imbibition curves computed from a pore network model.

Filtrate invasion into a hydrocarbon formation influences the readings of well logging tools. Although this phenomenon has been known, and corrected for, for many years, uncertainty remains with regard to the long-time behavior of invasion around observation wells where no flow in or out of the formation occurs after completion, and also with regard to the influence of formation wettability. We find that after sufficient time the invaded zone dissipates completely in a water-wet formation, but some invasion always remains in the oil/mixed-wet case. Non-wetting-phase trapping, manifested through relative permeability hysteresis, is the cause. Because trapping affects the values and the end points of the relative permeability curves, a waterflood front passing across an observation well is more distorted in the oil/mixed-wet case. The simulation results allow us to understand how logging tool measurements made in cased observation wells are influenced by drilling fluid invasion and will therefore lead to improved interpretation. This study shows strong links between the wettability of the formation and persistence of invaded zone saturation and between invaded zone saturation and the distortion of subsequent flood fronts.
Developing a Toolbox for Evaluating Water Injection Performance on the Norne Field
Authors: Atabay Shahram , Drønen Ole Magnar , Flo Hvidsten Jon Magne , Fawke Anna
Published: June 2012

The Norne Field is a mature subsea oil field located on the Norwegian continental shelf and it has been on production since November 1997. The reservoir drainage strategy is mainly based on water injection with an early phase of WAG injection. Pressure support is successfully achieved, however, currently (at early tail phase), the major challenge is to increase the macroscopic (vertical and areal) sweep efficiency in the upper part of the main reservoir.

Different methods and techniques have been applied to understand the current water flow pattern in order to optimize the macroscopic sweep efficiency:

1) Review of the historical data.

2) Use of Hall plot technique to evaluate the injectivity and vertical sweep.

3) Full field and conceptual simulation models.

4) Spearman’s rank correlation to investigate injectior - producer relationships.

5) Tracer data to evaluate the areal sweep.

Improving the water injection strategy is important for maximizing the field recovery factor.

This paper presents the methods used to evaluate the water injection strategy and the results of these evaluations for improvement.
Applications of Harmonic Pulse Testing to Field Cases
Authors: Fokker Peter A. , Renner Joerg , Verga Francesca
Published: June 2012

Harmonic pulse testing is a well testing technique in which the injection or production rate is varied in a periodic way. The pressure response to the imposed rates, both in the pulser well and in the observer wells, can be analyzed in the frequency domain to evaluate the reservoir properties. The advantages of this type of test are that dedicated well testing surface equipment is not required and that the test can be performed during ongoing field operations. In an earlier study we demonstrated that the harmonic pulse testing methodology can be used to evaluate the effective permeability to hydrocarbons and the reservoir total compressibility even for such a heterogeneous case as in a water injection scenario. The analysis can be performed using a numerical simulator in the Fourier domain, by which heterogeneities can be explicitly taken into account. As time-stepping is not required in such a simulation, calculations are much faster than calculations in the time domain.

In the present paper we report on the application of the methodology to two field cases. The first case is a gas storage reservoir, operated with a day‒night injection‒shut in scenario. Data analysis proved that the reservoir was homogeneous and that a minor fault identified by the seismic was not hindering hydraulic communication between the pulser and the observer wells. The second case is a set of harmonic test experiments on three groundwater wells, the details of which have been published earlier together with a first attempt to interpret the data. The previous analysis was based on the hypothesis of homogeneous formation, but could not consistently explain all the measurements. With our novel methodology it was possible to investigate the effects of heterogeneity and we demonstrated that the presence of a fault zone with reduced permeability may explain the observations.
Application of Integrated Production and Asset Modeling for Sour Field Development Planning
Authors: Alkindi A. , Linthorst S.
Published: June 2012

A key and challenging issue in the oil and gas industry is Integrated Asset Management, which encompasses efforts from various disciplines to build a single integrated model that describes the whole system. This paper presents an integrated production model (IPM), forecasting workflow and decision making philosophy to develop two complex sour fields comprising three reservoirs in South of Oman. The study involves two sour oil reservoirs (of different PVT properties, H2S concentrations) and drive mechanisms and one sour gas condensate reservoir that is used to complement associated gas to give a constant gas rate for export. Water injection and water handling are parts of the model.

The modelling couples subsurface dynamic 3D models (built using Shell's MoReS reservoir simulator), well models and surface network (built in GAP) and the interactions that occur in the production system. The configuration involves three reservoirs, 19 oil and 3 gas producers, 12 water injectors, one production station, three separators (low, medium and high pressure) and several flow lines of different sizes. The main objective of the study is to optimize the developments of these reservoirs by assessing the best design of surface network (plant capacity). The integration allows to assess the impact of various station capacities; either liquid or/and gas, on the project profitability under different operational scenarios such as injection rate, off-take, artificial lift and well phasing and their impact on CAPEX and OPEX. The model also helps in identifying system bottle-necks, effects of back pressure, mixing of fluids and flow assurance. The use of jet pumps as artificial lift mechanism was successfully imbedded and optimized.

The paper describes the structure of the modelling, surface components, optimization strategy, benefits and challenges of IPM deployment to choose the optimum field design. The results demonstrate the importance and merit of field management in addition to accuracy and rapidness of production forecast.
Assisted History Matching Using Three Derivative-Free Optimization Algorithms
Authors: Chen Chaohui , Jin Long , Gao Guohua , Weber Daniel , Vink Jeroen C. , Hohl Detlef F. , Alpak Faruk O. , Pirmez Carlos
Published: June 2012

Gradient-based optimization algorithms can be very efficient in history matching problems. Since many commercial reservoir simulators do not have an adjoint formulation built in, exploring capability and applicability of derivative-free optimization (DFO) algorithms is crucial. DFO algorithms treat the simulator as a black box and generate new searching points using objective function values only. DFO algorithms usually require more function evaluations, but this obstacle can be overcome by exploiting parallel computing.

This paper tests three DFO algorithms, Very Fast Simulated Annealing (VFSA), Simultaneous Perturbation and Multivariate Interpolation (SPMI) and Quadratic Interpolation Model-based (QIM) algorithm. Both SPMI and QIM are model-based methods. The objective function is approximated by a quadratic model interpolating points evaluated in previous iterations, and new search points are obtained by minimizing the quadratic model within a trust region. VFSA is a stochastic search method. These algorithms were tested with two synthetic cases (IC fault model and Brugge model) and one deepwater field case. Principal Component Analysis is applied to the Brugge case to parameterize the reservoir model vector to less than 40 parameters.

We obtained good matches with all three derivative-free methods. In terms of number of iterations used for converging and the final converged value of the objective function, SPMI outperforms the others. Since SPMI generates a large number of perturbation and search points simultaneously in one iteration, it requires more computer resources. QIM does not generate as many interpolation points as SPMI, and it converges more slowly in terms of time. VFSA is a sequential method and usually requires hundreds of iterations to converge.
A Modified Version of the Aziz et al. Multiphase Flow Correlation Improves Pressure Drop Calculations in High-Rate Oil Wells
Authors: Al-Attar Hazim H. , Mohamed Mohamed Y. , Amin Mohamed E.
Published: June 2012

The prediction of multiphase pressure drop during the simultaneous flow of oil, gas and water in vertical tubing strings is crucial in the development and optimum exploitation of an oil field.

In this paper a method is proposed to improve pressure drop predictions by Aziz et al. multiphase vertical-flow correlation. This correlation is theoretically justified as compared to the traditional empirical methods. The present method suggests combining several flow pattern maps with the Aziz et al. correlation in an attempt to achieve the improvement sought. Two field data sets comprising 32 production tests gathered from three different sources in the Middle East and North Africa were used to examine the performance of the various combinations.

The results of this work indicate that the performance of Aziz et al. multiphase correlation can be best improved by replacing its original flow-pattern map with the traditional Duns-Ros flow-regime map and for both data sets used. A significant improvement has been observed giving an overall absolute average percent deviation of 2.16% compared with 5.33% for the original correlation. Also, with this combination the relative performance factor has been reduced to 1.33 from 2.90 for the original Aziz et al. correlation. The efficiency of the Aziz et al.-Duns and Ros combination at high oil production rates, when compared with the original Aziz et al. correlation, was further examined by noticing the improvement gained in statistical measures at higher levels of liquid superficial velocity.

This work represents an addition to the technology of multiphase behavior in vertical pipes and its results will help in a more accurate design of tubing strings in high-rate producing oil wells.