bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Gas Chromatography/Combustion/Isotope Ratio Mass Spectrometry for Studying Nutrition and Biosynthesis in Plants
Authors: Yamamoto Mayu , Nakashita Rumiko , Suzuki Yaeko , Ichimiya Takahiro , Korenaga Takashi
Published: June 2009

Compound-specific isotope analysis of 15N enrichment of nitrogenous molecules by gas chromatography/isotope ratio mass spectrometry is a potential method for a quantitative access of nitrogen flow in plant nutrition and biosynthesis. Here, as a primary application of this method for plant nutrition studies, we demonstrate high sensitive detection of 15N enrichment of amino acids in white radish cultivated either with very low level of 15N-labeled organic or inorganic nutrients, and evaluate the practical utility of this method.
Self‐deception and the therapist: An interpretative phenomenological analysis of the experiences and understandings of therapists working with clients they describe as self‐deceptive
Authors: Westland Sandra , Shinebourne Pnina
Published: June 2009

Objectives. The aim of this study was to explore how participants experience working with clients they describe as self‐deceptive, as well as the participants' reflections on the experience and their understandings of self‐deception.

Design. Data were collected in two stages. In the first stage, participants were asked to provide a written description of a specific incident or of a set of sessions in which it seemed to the therapist that the client was deceiving him/herself. The second stage consisted of a semi‐structured interview, designed to follow‐up the written description in greater detail.

Methods. Four participants took part in the study. The data were analysed using interpretative phenomenological analysis.

Results. Three superordinate themes were identified in the analysis: therapists' self experiences; engaging with the client; and therapists' experiences and perceptions of the client.

Conclusions. The concept of self‐deception offered participants a perspective for describing and understanding clients who present a range of ‘difficult’ attitudes and behaviours, such as evasion and denial of the ‘truth’ of their predicament as understood by the therapist, conflicting, and contradictory attitudes to the process of self change, avoiding taking responsibility for themselves, lack of self‐understanding, withholding from engagement in therapy, and from relationship with the therapist. The findings also bring to light therapists' experiences of discomfort, frustration and anger, and feelings of incompetence when working with clients they described as self‐deceptive. The construct of client's self‐deception constitutes one possible interpretation but other interpretative possibilities are considered.
Acute Cognitive Therapy in Reducing Suicide Risk Following a Presentation to an Emergency Department
Authors: Catanese Albert Anthony , John Michael Stephen , Di Battista John , Clarke David M.
Published: June 2009

The ACT (Acute Cognitive Therapy) Program was implemented as a patient follow-up initiative to respond to people presenting to emergency departments with suicidal behaviour or ideation, in a psychosocial crisis. Over 12 months 188 patients were referred to the program of which 160 attended at least one appointment and 109 completed the program. Pre- and postmeasures indicated that significant improvement occurred in those who completed the program, that improvements were maintained at 6 months and representation rates were reduced. Immediate short-term directed treatment appears beneficial in the short and medium term, and the rapidity and location of follow-up appears to promote compliance.
Brief Cognitive-Behavioural Therapy for Children with Anxiety Disorders: Initial Evaluation of a Program Designed for Clinic Settings
Authors: Girling-Butcher Robyn D. , Ronan Kevin R.
Published: June 2009

Four anxiety disordered 8- to 11-year-old children and their parents participated in a shortened version of an efficacious cognitive–behavioural program for anxiety in children, designed to reflect therapy conditions found in usual clinical practice. A modified multiple-baseline design was used that combined clinic setting pragmatics with a necessary level of methodological protection. For ongoing evaluation, weekly measures of the child's trait anxiety and coping ability were obtained from the child and parents. In addition, a battery of measures was used to evaluate outcomes following treatment and at two follow-up intervals. Emphasising increased parent involvement and earlier exposure sessions, the program was found to lead to marked changes in child functioning. In particular, all children showed improvement on self-report, parent report, and independent clinician's ratings over the course of treatment. Moreover, scores on relevant indices were all within a nondeviant range following intervention, and all four children no longer qualified for an anxiety diagnosis at posttreatment and at 3- and 12-month followup. Findings are discussed in terms of implementation and evaluation in practice settings (e.g., critical components of treatment, use of pragmatic single case designs). Suggestions for future research include testing the effectiveness of this brief program on a large and diverse sample of children. Additional research is also required to find out to what extent increased parent involvement and earlier exposure sessions enhance the impact of treatment in the larger context of addressing features of the research-practice gap. Overall, findings provide preliminary support for the effectiveness of a brief cognitive–behavioural program for treating anxiety disorders in children, along with an evaluation strategy, compatible with some of the needs of service delivery settings.
Picture Exchange Communication (PECS) Training for Young Children: Does Training Transfer at School and to Home?
Authors: Carré Anna J. M. , Le Grice Bonny , Blampied Neville M. , Walker Dianne
Published: June 2009

The limited communicative abilities of young children with autism and developmental disabilities may be enhanced by augmentative communication systems such as the Picture Exchange Communication System (PECS). Both children and adults can learn to use PECS, but research is inconsistent in establishing the degree to which PECS training transfers reliably from the training setting to other settings, for example, regular classrooms, and home. Three 5–6 year-old children, diagnosed as autistic and/or developmentally disabled, were given 1:1 PECS training at school, structured to enhance generalisation and transfer. Concurrent observations were made in their regular classroom and at home to probe the extent of generalisation. All three acquired the ability to request a preferred object or activity by exchanging a picture symbol with a communicative partner. In tests of transfer and generalisation, a multiple-baseline across subjects design showed no use of PECS symbols either in the classroom or at home prior to training, with spontaneous initiations of picture exchange (transfer) occurring to a slight to moderate degree in the classroom and to a slight degree at home. Even with PECS training structured to enhance transfer, functionally significant degrees of generalisation of training may be difficult to achieve, and cannot be assumed to occur.
Guide on Measuring Uniformity of Furnace Exposure on Specimens Representing Test Samples Used to Determine Fire Resistance Ratings
Authors: Berhinig Robert
Published: June 2009

ASTM E5.11 Subcommittee on fire resistance is responsible for five fire test standards that rely upon furnaces to provide the heat exposure to test samples. These test samples range from floor-ceiling samples having a minimum area of 16.7 m2 to firestop systems that may include a single relatively small penetrating item. All these test standards include a precision and bias clause but none of the standards include a means for documenting the exposure or fire insult conditions imposed by the furnace onto the sample. This paper describes the activity underway within ISO TC92/SC2 to publish a procedure to measure the uniformity of furnace exposure imposed upon test samples. This procedure measures the temperature on a specimen replicating a test sample used to determine fire resistance ratings, the oxygen content in the furnace chamber, and the velocity across the specimen. The ISO method introduces the term “effective area of furnace opening” to identify the area within the furnace opening where the test specimen is not significantly influenced by furnace boundary conditions. The method is applicable to all ASTM fire test standards that use furnaces such as ASTM E119 as well as similar ISO and NFPA standards.
Sistemas de informação oficiais de meningite criptocócica, estado do Rio de Janeiro
Authors: Leimann Beatriz Consuelo Quinet , Koifman Rosalina Jorge
Published: June 2009

O objetivo do estudo foi comparar o perfil epidemiológico de meningite criptocócica em diferentes sistemas de informação, avaliando assim em que medida aquele disponível no Sistema de Informação de Agravos de Notificação refletiria as ocorrências da meningite criptocócica no estado do Rio de Janeiro, de 2000 a 2004. O banco do Sistema de Informação de Agravos de Notificação foi comparado com um novo banco composto pelos casos de meningite criptocócica desse Sistema, da Assessoria de Meningite da Secretaria de Saúde do Estado e dos registros do laboratório do Instituto Estadual de Infectologia São Sebastião. O Sistema captou 65,7% dos casos presentes no novo banco. O percentual de pacientes apresentando Aids como doença preexistente foi semelhante nos dois bancos (26% e 24,9%). Assim, embora a incidência de meningite criptocócica esteja subestimada nesse Sistema, o perfil dos casos notificados reflete o perfil do total de casos.
Numerical modeling of geosynthetic-encased stone column-reinforced ground
Authors: Yoo C. , Kim S.-B.
Published: June 2009

This paper presents the results of a comparative study on different finite element modeling approaches for modeling geosynthetic-encased stone column-reinforced ground for use in rapid embankment construction. The specific models considered include: (1) an axisymmetric unit cell; (2) a three-dimensional (3D) column; and (3) a full 3D model. The validity of the unit cell model was tested by comparison with the results from the 3D models. The applicability of continuum elements for modeling the geosynthetic encasement was also investigated. The results show that the 3D column model yielded practically identical results when compared with those of the full 3D model whereas the two-dimensional axisymmetric unit cell model tended to yield results that were 10 to 20% larger in terms of the vertical effective stress and lateral deformation of the stone column. It is also shown that a layer(s) of continuum elements can be used to model the geosynthetic encasement instead of membrane elements which are not readily available in commercial software for geotechnical analysis, provided that the axial stiffness of the geosynthetic encasement is taken into consideration. Based on the results of analysis, the effect of geosynthetic encasement on the performance of stone columns installed in soft ground under embankment loading is also discussed.
Reductions in swelling pressure of expansive soil stabilized using EPS geofoam and sand
Authors: Ikizler S. B. , Aytekin M. , Vekli M.
Published: June 2009

In the present study, sand and expanded polystyrene (EPS) geofoam were evaluated as potential stabilizers in improving the swelling behaviour of bentonite. A comprehensive laboratory experimental programme was conducted on bentonite with a high swelling potential. Five dosage levels of sand and five different thickness of EPS geofoam were investigated in two stages of the experiments. In the first stage of testing, the effect of sand on the swelling pressure of bentonite was investigated by two series of experiments. In the first series of experiments, bentonite at optimum water content was mixed with sand in proportions of 20, 40, 60 and 80% by weight. In the second series of experiments, the same percentages of sand were used as in the first series of experiments but the sand and bentonite were not mixed together. The sand was placed on the sample of bentonite which was then compacted at optimum water content. In the second stage of testing, the effect of EPS geofoam on the swelling pressure of bentonite was investigated using different thicknesses of EPS geofoam placed on the sample of bentonite. These thicknesses were the same as the thicknesses of sand which was placed on the sample of bentonite in the second series experiments of the first stage. These experiments show that the expansive soil can be successfully stabilized by sand and EPS geofoam.
Seismic displacement analysis of a reinforced soil model wall considering progressive development of reinforcement force
Authors: Huang C.-C. , Wu H.-J.
Published: June 2009

Progressive development of the reinforcement force in a geosynthetic-reinforced model soil retaining wall subjected to irregular ground accelerations was investigated in a pseudo-static-based analytical model. The progressive development of the reinforcement force was expressed as a function of maximum input ground accelerations in the proposed analytical model, which also incorporated a multi-wedge failure mechanism and Newmark's sliding-block theory. This analytical model eliminated a disadvantage inherent in the conventional pseudo-static approach, namely a possible overestimation of the seismic stability of the wall due to the assumption of full mobilization of the reinforcement force regardless of the intensity of ground excitation. It was also found that the value of the critical seismic coefficient [Formula: see text] calculated using a peak internal friction angle (ϕp) and a fully mobilized reinforcement pull-out force can be used to simulate the ultimate state of the model wall when subjected to irregular ground excitations. A softened friction angle of ϕ = 0.9ϕp simulated the wall behavior well when the horizontal displacement of the wall (Dh) was greater than 5% of the wall height (Ht). This finding is consistent with that for a conventional gravity-type soil retaining wall previously reported. A non-uniform distribution of tensile force along the reinforcement, with a peak value at the intersection of the reinforcement and slip surface and a reduced value at the facing-backfill interface was obtained, using a reduction factor of Rr–f = 0.5, based on the calibration of seismic displacements of the tested wall. A reduction factor that accounted for the mobilization of the friction angle along the soil-reinforcement interface, Rr–s, was also calibrated, based on the displacement analysis. It was found that values of Rr–s between 0.7 and 0.8 could be used to represent the pull-out behavior of reinforcement subjected to seismic loading. The proposed method is based on a single set of experimental results and therefore the applicability of the proposed method needs to be verified using more physical tests and/or numerical analyses of various wall geometries and reinforcement configurations.
Lateral oedometer testing of anisotropic clay as affected by surface roughness
Authors: ROHE A. , GAREAU L.F. , MOLENKAMP F.
Published: June 2009

To examine the state of anisotropy of a natural (glaciated) clay sample lateral stress oedometer tests are carried out to determine the magnitude and direction of the principal stresses. Initially, this was done by assuming no slippage along the boundary, thus for a perfectly rough oedometric ring with uniform anisotropic stress state and zero in-plane deformation. Here the other extreme case, the perfectly smooth oedometric ring, is examined by accounting for the analytical solution of a circular cylindrical continuum for isotropic linear elasticity, using appropriate boundary conditions. After determining experimentally the frictional coefficient, this solution is used in a semi-empirical interpolation method for estimating the influence of the roughness of the oedometric ring. For the assumption of a rough oedometric ring for the investigated Potclay the anisotropy ratio decreases in the range 0·58 to 0·30 with increasing axial effective stress in the range 355 ≤ σax≤ 1860 kPa. For the observed reduced wall roughness the anisotropy ratio is shown to increase to the range 0·70 to 0·40, which is a relative increase of 21% to 34%. The relative error in this estimated anisotropy ratio is estimated in the range ±9% to ±13%, increasing with increasing axial effective stress. The orientation of the in-plane anisotropy is shown to be independent of wall roughness.
Paths to statistical fluency for ecologists
Authors: Ellison Aaron M , Dennis Brian
Published: June 2009

Twenty‐first‐century ecology requires statistical fluency. Ecological observations now include diverse types of data collected across spatial scales ranging from the microscopic to the global, and at temporal scales ranging from nanoseconds to millennia. Ecological experiments now use designs that account for multiple linear and non‐linear interactions, and ecological theories incorporate both predictable and random processes. Ecological debates often revolve around issues of fundamental statistical theory and require the development of novel statistical methods. In short, if we want to test hypotheses, model data, and forecast future environmental conditions in the 21st century, we must move beyond basic statistical literacy and attain statistical fluency: the ability to apply statistical principles and adapt statistical methods to non‐standard questions. Our prescription for attaining statistical fluency includes two semesters of standard calculus, calculus‐based statistics courses, and, most importantly, a commitment to using calculus and post‐calculus statistics in ecology and environmental science courses.
Migratory Canada geese cause crash of US Airways Flight 1549
Authors: Marra Peter P , Dove Carla J , Dolbeer Richard , Dahlan Nor Faridah , Heacker Marcy , Whatton James F , Diggs Nora E , France Christine , Henkes Gregory A
Published: June 2009

In the United States alone, over 7400 bird–aircraft collisions (birdstrikes) were reported in 2007. Most of these strikes occurred during takeoff or landing of the flight, and it is during these flight phases that aircraft experience their highest risk of substantial damage after colliding with birds. Birdstrikes carry enormous potential costs in terms of lives and money. Using feather remains and other tissue samples collected from the engines of US Airways Flight 1549, which crash landed in the Hudson River in New York City on 15 January 2009 after a birdstrike, we apply molecular tools and stable hydrogen isotopes to demonstrate that migratory Canada geese were responsible for the crash. Determining whether the geese involved in this birdstrike event were resident or migratory is essential to the development of management techniques that could reduce the risk of future collisions. Currently, the US civil aviation industry is not required to report birdstrikes, yet information on frequency, timing, and species involved, as well as the geographic origin of the birds, is critical to reducing the number of birdstrikes. Integrating this information with bird migration patterns, bird‐detecting radar, and bird dispersal programs at airports can minimize the risk of such collisions in the future.
Managing Uncertainty of Well Log Data in Reservoir Characterization
Authors: Deo P. , Xue C. , Mendez F.
Published: June 2009

Well log data provides valuable information for characterizing reservoirs through seismic analysis, reservoir modeling and fluid substitution. Reliable economic evaluation of a reservoir demands reliable characterization of reservoir properties. It is crucial to have a reliable uncertainty analysis for non-unique solutions of reservoir characterization.

A stochastic petrophysical model based on an inversion algorithm was used to compute reservoir properties. The well log data uncertainty and the resulting impact were studied with an error propagation algorithm. The algorithm was presented to calculate propagated error and manage uncertainties based on Gassmann's fluid substitution. Data control for the input measurement of Gassmann's equation was performed through environmental uncertainties analysis before proceeding with the inversion.

To demonstrate the error propagation in reservoir characterization, we studied both in-situ and dry models before fluid substitution. Then, the uncertainty analysis was performed for the new model with fluid substitution. Moreover, the propagated errors for velocities of the new model were also evaluated. A joint interpretation based on a volumetric mathematical model of various logging measurements was used to analyze data quality. In this paper, we present an important insight into uncertainty analysis and error propagation in fluid replacement modeling. The algorithm provides stable solutions with uncertainty control for reservoir characterization.
Underbalanced Drilling in Depleted Formation Achieves Great Success: Case Study
Authors: Shadravan Arash , Khodadadian Mohammad , Roohi Abbas , Amani Mahmood
Published: June 2009

The PR-70 well, the third well of the National Iranian Drilling Company (NIDC) UBD campaign in Parsi field, is the first well to produce while drilling in a 2-year underbalanced drilling (UBD) project in the field. NIDC and Weatherford selected the UBD technique because of the depleted reservoir pressure, which had dropped to 2,728 psi at depth of 2,755m (5.8 ppg). Drilling such a depleted reservoir with conventional mud would have caused a huge overbalanced state, loss of circulation, and increased possibility of blowouts or damage to the reservoir. Another reason for implementing the UBD technique was to increase productivity of the well by decreasing formation damage that resulted from drilling fluid losses.This paper explains the execution of UBD technique at well PR-70. It also discusses the well design, UBD design parameters, underbalanced modeling considerations and the lessons learned from this job that all led to the success of this project. As soon as the well started to produce oil, UBD conditions were established and continued to TD.
Novel Waterflooding Strategy by Manipulation of Injection Brine Composition
Authors: Ligthelm D. J. , Gronsveld J. , Hofman J. P. , Brussee N. J. , Marcelis F. , van der Linde H. A.
Published: June 2009

As brine composition profoundly influences reservoir wettability and hence microscopic sweep, careful design of injection brine is part of a strategy to improve on oil production in existing and future water flooding projects, in both sandstone and carbonate reservoirs and in combination with follow-up EOR projects.

The following results were found: (1) Formation water with higher salinity level correlates to a higher content of multivalent cations. This causes the (sandstone) reservoir wettability to be more oilwet; (2) The field-observed temporary reduction in watercut during breakthrough of so-called "Designer Waterflood" water in a Middle Eastern sandstone reservoir with highly saline formation water was interpreted to be caused by an oil bank ahead of the slug of injected water; (3) The oil bank results from improved sweep by wettability modification to more waterwet state. The interpretation was confirmed by laboratory experiments; (4) Experiments in limestone core plugs demonstrate similar wettability modification, if the sulphate ion content in the invading brine is far in excess of the calcium ion content.

Based on these results the following conclusions were drawn: (1) Designer Waterflooding may increase the Ultimate Recovery of oil by at least a few percent; (2) There is scope for further improvement in oil production by flood front stabilization by adding low concentration polymer to the optimised slug; (3) If future EOR projects are planned, a Designer Waterflooding pre-flush is recommended to obtain more favourable oil desaturation profiles and savings on polymer costs; (4) In case of seawater injection into reservoirs with formation water of low salinity level, removal of multivalent cations from the seawater should be considered to avoid the potential risk that the reservoir becomes more oilwet, which will result in reduced sweep.
Effects of Fracture and Frequency on Resistivity in Different Rocks
Authors: Sandler Joel , Li Yuzhang , Horne Roland N. , Li Kewen
Published: June 2009

Detection and characterization of fractures in rock is important in many cases for the development of energy resources such as geothermal energy and petroleum. To this end, the effect of frequency on resistivity as a function of water saturation has been studied in rocks with and without fractures. Different rocks (Berea sandstone, greywacke from The Geysers geothermal reservoir) were used in this study. It was found that the effect of frequency on resistivity is different in rocks with and without fractures, especially in the range of low water saturation. The validity of the Archie equation depends on the existence of fractures, frequency, and the range of water saturation.
Gravity Segregation in Gas Improved Oil Recovery of Tilted Reservoirs
Authors: Jamshidnezhad Mohammad
Published: June 2009

The model of Stone for gravity segregation in gas improved oil recovery (IOR) indicates the distance injected gas and water travel together before complete segregation. This model is very useful for co-injection of water and gas into horizontal depleted reservoirs. A proof by Rossen and van Duijn showed that the model of Stone applies to steady-state gas-liquid flow, and also foam flow, in horizontal reservoirs as long as the standard assumptions of fractional flow theory (incompressible flow, Newtonian mobilities, local equilibrium) apply. However, until now, there is no study on application of this model for tilted reservoirs. In this paper, by using a three dimensional finite-difference compositional reservoir simulator, we investigate gravity segregation in tilted reservoirs and then compare the results with the model of Stone. This study shows that the math proof by Rossen and van Duijn provided for the horizontal reservoir doesn't work if the reservoir is tilted, and that the model of Stone should be corrected to apply in tilted reservoirs. There are good agreements between the corrected model and the reservoir simulator results in tilted reservoirs.
Analogous Reservoirs to Chicontepec, Alternatives of Exploitation for this Mexican Oil Field
Authors: Gachuz-Muro Heron , Sellami Hedi
Published: June 2009

The giant Chicontepec field contains oil from 18 to 45 °API in laminated sandstones of 0.1 to 10 mD at a depth of around 2500 meters (8202 ft). Original Oil in Place (OOIP) is estimated to be 140, 900 MMSTB. The complex geology (complicated structural and stratigraphic nature of the reservoirs), lack of reservoir information and lack of technology availability caused a gap between discovery and development. Throughout a period of several decades some exploration wells were drilled based on 2D seismic and log correlations of the reservoirs.

The exploitation of the Paleonchannel was postponed because most of the wells showed poor productivity. The reasons for the low recovery (around 3%) have never been thoroughly understood. Various hypotheses have been proposed to explain the deficient performance such as partial closing of the fractures with declining reservoir pressure (bubble-point pressure is near initial pressure), inadequate comprehension of the geological model, deficiency in the fracturing technology, oil-wetted or intermediate-wetted reservoirs, applicability of unconventional wells (horizontal wells, casing drilling technology), etc. Today, the Chicontepec Paleochannel is an intermediate stage.

Due to the experience of different fields with similar characteristics, this paper describes an analysis of alternatives that may be considered to resolve the problems of exploitation at the Chicontepec field. Advanced technologies, hydraulic fractures, artificial lift systems, all of them combined with secondary and enhanced oil recovery, may be feasible to sustain or increase production. A number of hurdles will have to be overcome. This field, the second most important oil field in Mexico, should take advantage of the experience learned from these analogous reservoirs.
Gas Injection IOR for Widely Varying Initial Compositions
Authors: Singh Kameshwar , Whitson Curtis H.
Published: June 2009

The paper presents the effect of initial reservoir fluid composition on oil recovery for reservoirs under gas injection. To analyze the effect of initial fluid composition, a series of fluid systems were selected based on isothermal gradient calculation from a North Sea field. The systems ranged from low-GOR oils to high-GOR gas condensates, with a continuous transition from gas to oil through a critical mixture.

In this compositional reservoir simulation study, a 3D dipping reservoir with dip angle of 3.8 degree was used. The reservoir layer permeabilities were varied based on Dykstra-Parsons model. Different average reservoir permeability was used to quantify the effect of gravity.

For oil reservoirs, the oil recovery of oil increases with increasing initial solution gas-oil ratio. The oil recovery increases gradually for low-GOR to moderate-GOR oil reservoirs. For moderate-GOR to near-critical oil, the oil recovery increases rapidly. The increase in oil recovery as the reservoir oil becomes more volatile is due to decrease in oil viscosity and the vaporization effects of the injection gas. For gas reservoirs, the condensate recovery increases rapidly from a near-critical gas towards near 100% condensate recovery for high-GOR systems. The oil recovery also depends on the permeability distribution. The oil recovery is higher in the case of high permeability at the bottom than high permeability at the top due to gravity segregation effect. The effect of gravity segregation on oil recovery is more pronounced in high permeability reservoirs. For lean gas condensate the oil recovery is almost independent on the permeability distribution.

The paper shows the variation of oil recovery with initial reservoir fluid composition for different permeability distributions, gas injection period, critical saturation, vertical to horizontal permeability ratio, level of pressure maintenance, and injection gas composition.
Pressure Transient Well Testing Encountered Complexities: A Case Study
Authors: Karami Pooyan , Hashemi Abolfazl
Published: June 2009

Pressure transient testing is one of the most useful reservoir description methods. It provides valuable information about the reservoir/well-bore characteristics (e.g., homogeneity, heterogeneities, phase segregation, stimulation effectiveness, interventions, etc.) and quantitative information about reservoir parameters (e.g., permeability, fracture length, average reservoir pressure, skin, wellbore storage, etc).

The study of pressure transient testing in one of the Iranian giant oilfields was initially undertaken to estimate important well and reservoir flow parameters and characterize heterogeneities in the Fn limestone formation; However, during the course of interpretation, numerous engineering complexities were encountered due to the nature of well behavior and reservoir conditions led to the masking of the actual reservoir response: 1) a high permeable reservoir with high degree of heterogeneities with high skin and high wellbore storage, 2) Partial penetration behavior due to asphaltene plugging on the sand-face/left fish in hole, 3) an obvious hump effect due to phase segregation inside the well 4)Pre and Post acid pressure transient response behaviors in a successful diversion acidizing operation 5)An interference response behavior due to a nearby well bore shut in.

The paper also presents how transient well testing in conjunction with dynamic pressure-production data have helped to clarify the boundary effect on a build up test; the modified build up secondary derivative based on the pseudo-steady state extrapolation of the preceding drawdown period shows a constant trend which recognized as close boundary effect.
The Effect of Oil and Gas Molecular Diffusion in Production of Fractured Reservoir During Gravity Drainage Mechanism by CO2 Injection
Authors: Kazemi A. , Jamialahmadi M.
Published: June 2009

During the primary production of fractured reservoir most of oil is produced from fractures and a lot of oil remains in matrix. Trapped oil in the matrix can be recovered by gas injection by activating gravity drainage mechanism. In addition there is a big impact of molecular diffusion of oil and gas in total oil recovery from fractured reservoir .The experimental work can by used to model this mechanism in combination of numerical simulator to investigate this phenomenon more accurately.

A fully compositional model has been applied to a numerical experiment in literature to investigate the drainage of CO2 from a core with artificial fractures and the effect of molecular diffusion included. The same study has been applied for a synthetic fractured reservoir model to investigate the effect of CO2 injection in oil recovery mechanism in the field scale.

In this work we found that at early stage we have oil swelling and gravity drainage followed by a slow extraction mechanism which recovers the intermediate and heavy components from the residual oil. The combined effect of diffusion and gravity suggests that application of the oil and gas diffusion coefficients is critical in any field scale simulation of a fractured reservoir and the correct diffusion coefficients should be applied.

A lot of oil reservoirs in the world are fractured and with primary recovery we can produce maximum 30 % of original oil in place therefore we need to have an accurate observation of secondary and tertiary oil recovery in these reservoirs. The understanding of oil recovery mechanism also is crucial for reservoir management especially when developing field management plans. A low miscibility-pressure requirement often is a significant advantage of CO2-miscible flooding. This process could have significant future application in areas with economical CO2 supplies from natural deposits or surface sources.
Pumping of Fluids Using Pressure Impulses
Authors: Pierre B. , Gudmundsson J. S.
Published: June 2009

Impulse pumping is a new method to pump fluids. The method is described briefly and then numerical simulations were carried out to illustrate the nature of impulse pumping. The simulations are based on the linear ideal wave equation and the numerical approach is based on a second-order Godunov scheme. The work illustrates how sinusoidal pressure waves are reflected at open and closed boundaries, representing open and closed non-return valves in impulse pumping. An impulse pumping example was presented for 40 m lifting of water. It was shown how the wellhead pressure used determines the lifting depth and flow rate achievable; the greater the wellhead pressure, the greater the lifting and rate. In impulse pumping the wellhead pressure is controlled by the cracking pressure of a non-return outlet valve. Fluid enters the production tubing through a non-return inlet valve downhole. The stroke length of a pressure wave generator determines the wellhead pressures achievable in impulse pumping. It was suggested that the water hammer equation can be used to estimate the flow rate in impulse pumping.
Predicting Water Influx From Common Shared Aquifers
Authors: Shimada Munenori , Yildiz Turhan
Published: June 2009

In this paper, we present 3-dimensional analytical models to forecast water influx from a common shared aquifer to several producing reservoirs. We consider finite aquifers and an arbitrary number and distribution of multiple reservoirs. The new analytical models have been verified by comparing them against the existing analytical models for the special case of symmetrical distribution of multiple identical reservoirs. The computation of the equations representing the analytical models is straightforward.

The new analytical models proposed in this study may be used for aquifer representation in reservoir simulators and material balance based reserve estimate studies. Using the analytical models, we show a sample calculation for irregularlyshaped reservoir on an aquifer.
Low Dosage, High Efficiency and Environment Friendly Inhibitors: A New Horizon in Gas Hydrates Mitigation in Production Systems
Authors: Kannan Krupa , Punase Aarti
Published: June 2009

Presently, gas hydrates formation pose problems, causing flow restrictions, in gas and oil industry including drilling operations (particularly in deep water), production process, well workovers where gas and water come into contact at equilibrium conditions. Traditional hydrate control methods of insulation and/or thermodynamic or chemical inhibition may not provide the desired level of hydrate protection at an economic price. Low-Dosage Hydrate Inhibitors (LDHIs) are a proven technology to control hydrates in numerous applications and are instrumental in reducing the total cost of operations. Low dosage Inhibitors are either kinetic, thermodynamic inhibitors or anti- aglomerants, which either prevent hydrate formation or remove the hydrates that are already formed respectively.

Therefore, this paper focuses on introduction to such low dosage inhibitor which can perform all the functions like prevention of formation of hydrate nuclei (like kinetic or thermodynamic inhibitors) and dispersing the already formed ones in flowlines (like anti- agglomerants). This paper proposes the use of Cationic polymers like cationic starch (from a high amylose carbohydrate source) in low concentration with addition of Polyethylene Oxide (PEO) as a new Gas Hydrates inhibitor.

The polymer with PEO, dissolved in water, can be introduced in petroleum fluid using mechanical equipment or utilized in treating fluid prior to substantial formation of the hydrates. As observed from an experimental analysis, these positively charged polymers interfere with nucleation of hydrates, increase induction time of gas hydrate nucleation, suppress memory effect, and act as antifreeze and thereby controlling hydrates.

With reference to these polymers, their abundant availability, easy application techniques and simple cationization procedure all contribute to its inexpensive and environment friendly usage as gas hydrate inhibitor. This paper provides systematic approach and relevant theoretical explanation for the proposed technique.
Mapping Karst Diagenetic Networks in Carbonate Reservoir Using Seismic Indicators and Well Data
Authors: Hamid A. , Sadeghzadeh F.
Published: June 2009

The diagenetic processes play the most important role on the creation and distribution of the reservoir characteristics. Karstification, by inducing secondary porosity through dissolution and therefore enhancing the porosity of the sedimentary facies, is a distinguished diagenetic process in carbonate reservoir's pore network formation.

The Fahliyan formation's structure is a symmetrical anticline elongated in N-S direction and was developed in a ramp type carbonate platform. The reservoir consists of three separate stacked-up pay zones, and the main production was from the middle and lower zones. Karstification was developed in Fahliyan and created the following two main dissolution events: –Early diagenetic dissolution process created secondary pores, as intercrystaline/ microporosity, molds and vugs (10 μm – 1mm. Size).–Paleokarst event generated secondary pores, as molds, large vugs (up to 2 cm. in size), solution enlarged fractures and solution pipes.

So far, the field was modeled as a layered carbonate reservoir with laterally homogeneous properties. Therefore an integrated seismic stratigraphic-sedimentological study is performed using 3D seismic indicators, log and core data to define a conceptual diagenetic model at the field scale for imaging the karst networks and characterizing their effective properties. The study determines a uniformly distributed early dissolution event without particular geometry or preferential orientation for the top zone and a North-South oriented elliptical porous zone around the structure for the middle and lower zone, which follows the geometry of a freshwater lens and is a result of karstification process. The integration of the seismic stratigraphic interpretation with well data and the results of the seismic inversion, led to the definition of reservoir quality maps for the reservoir layers. Karst network geometries were subsequently incorporated into a deterministic reservoir model and facies properties tested against 8 years of production history in an iterative dynamic simulation workflow.
Capillary Trapping Capacity of Rocks and Sandpacks
Authors: iglauer Stefan , Wülling Wolfgang , Pentland Christopher H , Al Mansoori Saleh K , Blunt Martin J
Published: June 2009

We quantify the influence of the initial non-wetting phase saturation and porosity on the residual non-wetting phase saturation based on data in the literature and our own experimental results from sandpacks and consolidated rocks. The principal application of this work is for carbon capture and storage (CCS) where capillary trapping is a rapid and effective way to render the injected CO2 immobile, guaranteeing safe storage.

We introduce the concept of capillary trapping capacity (Ctrap) which is the product of residual saturation and porosity that represents the fraction of the rock volume that can be occupied by a trapped non-wetting phase. We propose empirical fits to the data to correlate trapping capacity and residual saturation to porosity and initial saturation. We show that trapping capacity reaches a maximum of approximately 7% for rock porosities of 20%, which suggests an optimal porosity for CO2 storage.
Revitalising a Medium Viscous Oil Field by Polymer Injection, Pirawarth Field, Austria
Authors: Poellitzer Stefan , Florian Thomas , Clemens Torsten
Published: June 2009

The Pirawarth Field, located in Austria, has been considered for polymer flooding. The reasons were the good permeabilities, medium viscosity of the oil (50 cP), low reservoir temperature (30 °C) and injection of low salinity water, resulting in low polymer concentration requirements.

Production from this field started in 1964. Until 2008, the recovery factor of the field reached 26 %. The reason for the low recovery factor is the unfavourable mobility ratio between the viscous oil and water.

In addition to conventional history matching, produced water chloride concentration data was implemented as matching parameter. The chloride concentration match revealed that the geological structure of the field was not well represented, although the water cut increase could be matched. This lead to delayed simulated breakthrough of the low salinity injected water. Improving the geological model enabled an improved match of the injected water breakthrough.

Laboratory experiments confirmed high efficiency of polymers in increasing water viscosity for the Pirawarth conditions. A core flood experiment was conducted and showed that adsorption is limited, the water relative permeability will be reduced by polymer injection and that the displacement with polymer after water flooding results in incremental recovery of more than 20 % of oil in place.

The core flood experiment was simulated and the parameters derived from the core flood experiment were used in the dynamic model of the field. The results of the simulation are very promising, indicating an increase in oil recovery in the pilot area of 5 %. It is planned to perform the pilot in 2010.
Oil Recovery From a Tight Fractured Basement Field
Authors: De Kok J. , Neff P. , Clemens T.
Published: June 2009

A tight naturally fractured basement reservoir in the Middle East contains an oil column of at least 2950 ft. The reservoir fluid consists of light oil with viscosities ranging from 0.2 to 0.4 cP and is saturated at the top of the reservoir. The oil is produced through fracture corridors with an effective permeability of approximately 0.1 md. The background fractures have an effective permeability of less than 0.001 md. The average porosity of the field is 1.1%. This paper presents results and setup of a multi-disciplinary study with the aim of optimizing production of this tight reservoir.

Due to the high permeability contrast, a dual-permeability approach has been selected. Fracture characterization was based on outcrop studies, core data, borehole images, production logging results and conventional log interpretation. A discrete fracture network (DFN) was created incorporating all available data and assuming fractal behavior of fault and corridor distributions. The DFN was scaled up for simulation and several feedback loops were performed for dynamic calibration.

The resulting dual-permeability simulation model was used to investigate development strategies. Compositional grading was implemented to correctly describe the fluid properties within the high relief structure. Due to its low permeability, gas/oil segregation caused by gravity hardly plays a role in the background fracture network during depletion. Additionally, because of the low mobility contrast, gas saturation can build up to values exceeding 25%, even whilst assuming straight line relative permeability curves and zero critical gas saturation.

Simulation shows that a recovery of more than 10% is expected for depletion in this tight reservoir, which is exceptionally high for solution gas drive. Gas injection can yield additional recovery, but with larger uncertainties.
A New Skin Factor Formulation for Flow Around Horizontal Wells Including Anisotropy and Partial Penetration
Authors: Ghahri Panteha , Jamiolahmady Mahmoud , Sohrabi Mehran
Published: June 2009

Modelling flow around horizontal wells (HWs) is a complex and challenging task due to the three-dimensional (3D) nature of the flow including the permeability anisotropy. This work is aimed to provide a reliable tool for prediction of the well performance of HWs. The steady state Dracy flow of a single-phase incompressible fluid in a HW was simulated by developing a 3D single HW mathematical model using Comsol multi-physics mathematical package which is based on finite-element methods. In house simulator is validated and verified when comparing its results with the corresponding values obtained from ECLIPSE commercial simulator, and a number of semi-analytical models widely used in the petroleum industry, all for the same prevailing conditions. These semi-analytical equations have been obtained by simplifying the 3D system to two 2D problems. We demonstrate that this assumption is only appropriate if the thickness of reservoir model is small compared to the length of HW. Our results also indicate that these equations may not predict the well performance of HW correctly specially in low permeability anisotropy values. Based on the results of in house simulator, correlation has been developed for calculation of mechanical skin using the efficient statistical Response Surface Method. This skin factor is employed in an open-hole vertical well productivity equation giving the same flow rate as that of the HW. The results of the proposed formulation have been tested against new data points, which have not been used in its development confirming the integrity of the approach. Moreover, a comprehensive sensitivity study on the impact of pertinent parameters (i.e. HW radius, HW length, reservoir dimensions, anisotropy and partial penetration) on the performance of a HW has been conducted with some important practical findings.