bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tuning the influence of metal nanoparticles on ZnO photoluminescence by atomic-layer-deposited dielectric spacer
Authors: Liu Monan , Chen Rui , Adamo Giorgio , MacDonald Kevin F. , Sie Edbert J. , Sum Tze Chien , Zheludev Nikolay I. , Sun Handong , Fan Hong Jin 
Published: April 2013

Abstract
There is increasing interest in tuning the optical and optoelectronic properties of semiconductor nanostructures using metal nanoparticles in their applications in light-emitting and detection devices. In this work we study the effect of a dielectric Al2O3 gap layer (i.e., spacer) on the interaction of ZnO nanowires with metal nanoparticles. The Al2O3 spacer thickness is varied in the range of 1–25 nm using atomic layer deposition (ALD) in order to tune the interaction. It is found that ~5 nm is an optimum spacer thickness common for most metals, although the enhancement ratio of the near-bandedge emission differs among the metals. Consistent results are obtained from both photoluminescence (PL) and cathodoluminescence (CL) spectroscopies, with the latter being applied to the optical properties of individual semiconductor/metal nanoheterostructures. The interaction is primarily proposed to be related to coupling of ZnO excitons with local surface plasmons of metals, although other mechanisms should not be ruled out.
Early- and late-arriving photons in diffuse optical tomography/Früh und spät ankommende Photonen in der diffusen optischen Tomographie
Authors: Proskurin Sergey G. , Potlov Anton Y. 
Published: April 2013

AbstractA method of diffuse optical tomography (DOT) is described for the direct detection of absorbing and scattering inhomogeneities such as cysts, hematoma, or tumors. DOT can also be used to detect small changes in the oxygenation and deoxygenation of blood in designated regions of the heads of neonates, and in breast cancer. In contrast to the early part of time-resolved transmittance of a femtosecond pulse, late-arriving photons are used for this purpose. A 2D numerical simulation is used for quantitative matching of diffuse model curves to experimental data. The finite difference method is used for computer simulation of movements of a cloud of photons from the surface of an object to its center. The 3D representations of the time point spread functions (TPSF) represent a flat surface in a homogeneous case. Lower parts of the surface indicate the presence of inhomogeneities at the corresponding angles.
Optimization of the "Fractured Triangle" to Determine Matrix/Fracture Permeability Ratio, Fracture Partitioning Coefficient and Intensity Index Derived from the Fractured Triangle of Pressure Transient Analyses
Authors: Elkewidy Tarek Ibrahim 
Published: April 2013

Abstract
In a previous research (IPTC 14187) a new technique was introduced to characterize all kinds of naturally fractured reservoirs on the Megascopic scale of pressure transient analyses. The technique is optimized through application of pressure derivative methods to yield a very characteristic graphical representation (triangle) of each hydraulic "flow" unit in the fractured reservoir.
The graphical technique along with newly derived formulas yield the most important petrophysical and engineering parameters about the heterogeneous naturally fractured reservoir including effective fractures, matrix and skin systems volumes, partitioning coefficient, fracture intensity index, formation resistivity factor, formation tortuosity, effective drainage radius, damage radius, effective cementation exponent, fracture porosity, matrix porosity, storativity ratio, in addition to fracture permeability, matrix permeability, damaged permeability, average permeability, pressure drop across the damage area, skin factor, damage permeability, average/dimensionless diffusivity factor, flow efficiency, damage ratio/factor, economic implication of formation damage, average hydraulic "flow" unit quality index.
The technique is extended to derive the fracture partitioning coefficient and intensity index in terms of storativity ratio generated from the fractured triangle of pressure transient analyses along with new fracture/matrix permeability ratio and fracture/matrix porosity ratio are introduced to aid describing the degree of reservoir heteroginity. Again the graphical technique of the fractured triangle has proven to be successful for all kinds of fractured reservoirs including clastics, carbonates and basement rocks. This study will present the theory along with successful field application with the results.
On the Accuracy of Dimensionless Inflow Performance Relationships for Gas wells
Authors: Kalantariasl A.. , Farhadi I.. , Nasriani H. R. 
Published: April 2013

AbstractUsually four-point backpressure test, an isochronal test or a modified isochronal test is conducted to predict gas well deliverability. During past decades several simple dimensionless inflow performance relationships (IPRs) have been developed to eliminate the need for conducting multi-point test by using only data from a single drawdown or build-up test. The capability and accuracy of these models should be evaluated with measured field data using wide range of fluid and rock properties. This paper addresses the limitations, accuracy and optimal use of proposed dimensionless inflow performance correlations (Mishra and Caudle, 1984, Al-Attar and Al-Zuhair, 2009) based on back-pressure field test data of 53 wells that cover a broad range of AOF, reservoir pressure, well stabilized rate and pressure. The results show that both methods lose their accuracy at high rate and low drawdown conditions with unacceptable overprediction of AOFs. None of the studied models are recommended to use when dimensionless pressure (ratio of the well pressure to the reservoir pressure) is above 0.9. Advantages and ranges of optimal use of different models are discussed through error analysis.
Effective Analytical Approaches to Enhance Productivity of Low Producing Gas Wells
Authors: Rahim Zillur , Waspada Dwi , Al-Anazi Hamoud , Al-Kanaan Adnan , Pacheco Eduardo 
Published: April 2013

Abstract
Hydraulic fracturing is a widely used technology in the industry to enhance oil and gas production, particularly in tight formations. Tight gas and shale cannot sustain commercial production rates without fracturing. Although the technique has been used in the industry for many years and vast improvements have been made in upgrading fluid chemistry, proppant types, pump schedule sequence, and overall well completion system, a close evaluation is always required to ascertain that the fracturing has provided the level of productivity expected from the candidate well. Such evaluation and analysis will help improve and optimize the stimulation technique for any given reservoir and field conditions, address specific challenges in that area, and determine remedial plans on any well that did not show expected results in terms of productivity enhancement.
Saudi Arabian gas wells are usually stimulated to enhance and sustain production. Wells drilled in the R-1 reservoir in Field-A, that exhibit low to moderate permeability, are routinely hydraulically fractured. Many of these wells produce a high, sustained rate after a successful stimulation treatment. Some others do not perform up to expectation as seen from the rate decline. This can be caused mainly by inefficient fracture treatments such as achieving short half-length, limited vertical coverage, and poor post-frac cleanup. A critical and intense work on numerous wells has been performed using available data from geology, open hole logs, cores, pressure transient tests, etc., to understand and quantify reservoir characteristics, fracture properties, and flow capacity of these wells to come up with plans to improve productivity. Such plans include remedial treatments such as refracturing, placing additional perforations in previous unperforated intervals, initiating hydraulic fractures in different layers, and sidetracking the well to change its trajectory and geometry to contact new producing intervals. This paper summarizes the well conditions, complete evaluation processes, and suggests remedial procedures for each well to ensure full potential.
High Quality Images while Drilling
Authors: Bazara Magdi , Al Sharafi Mohamed , Maalouf Janine , Kindi Zainab Al 
Published: April 2013

Abstract
Drilling highly deviated wells in heavily fractured and complex heterogeneous carbonate formations is a challenging process that requires a real time monitoring and utilizing an MWD and LWD technology. Currently PDO is developing X field and drilling horizontal wells for gas in A formation in which the reservoir compromises a heterogeneous vuggy limestone and fractures network that is distributed all over the field. The challenge faced during drilling is the total drilling mud losses due to presence of major fractures, consequently those fractures represent a threat for early water break through and shortening the life of the well. PDO has utilized the Ultra high resolution LWD resistivity images in several wells to tackle this problem, which successfully helped to identify the fractures zones that contributed to the drilling mud losses and design completion to isolate those fractures zones. As well as selecting a proper perforation zones away from the fractures.
Having different depths of investigation can help to analyses invasion, provide inputs for petrophysical formation evaluation and to differentiate between features that appears near wellbore or deep in the formation. After drilling, memory data which has better sampling and data density was processed and quick geological interpretation was performed, The interpretation included complete structural borehole features identification such as (Structural dip computation by picking bed boundaries intersected while drilling), Detailed fractures characterization.
To identify type of fractures(conductive, resistive), morphology and geometry of each fractures (continuous, discontinuous) and fractures density and distribution along the logged interval. Minor sub-seismic faults were also identified from the images. The geological interpretation of the high resolution resistivity images revealed the presence of a few major conductive fractures that were possibly enhanced by drilling and a large number of partial discontinuous conductive and resistive fractures.
Importance of Checking Quality Control of Data in Describing Oil and Gas Reservoirs and Its Effect in Calculating Important Reservoir Parameters and Thus, Oil and Gas Reserves
Authors: Zaafran Zaher M. 
Published: April 2013

AbstractThis paper discusses more than 30 years of experience in auditing and evaluating oil and gas fields and its value in managing risks/uncertainties around the globe. These activities are highly dependent on the quality of the data utilized, especially those of well log data, together with the techniques used in measuring the physical and the fluid properties of both the core data, the interpretation of the well logs, the pressure transient analysis, and the Pressure Volume Temperature (PVT) data of the associated reservoirs.The importance of using correct data by checking its quality has become one of the most challenging and important tools in reducing risks and uncertainties in recent years. This conclusion has been based on the fact that while auditing and evaluating oil and gas fields around the globe in the past 30 years, a vast majority of the data that I have observed has been found to be compromised. Moreover, it was also observed that while analysis was highly dependent on the quality of the data utilized, the interpretation procedures accordingly requires accurate input data (like in the case of log interpretation, pressure transient analysis or even core and PVT analysis), and these analysis were found to have serious errors on parameters involved in calculating important reservoir parameters and constructing geological models required for future reservoir development and reservoir management.Field examples to show the size of the damages created by using unchecked data quality will be exhibited in this study especially in heterogeneous reservoirs. How to accurately calculate important reservoir parameters with field examples will also be illustrated, and the effects of such techniques in reducing uncertainties by calculating oil and gas reserves will also be addressed.Summary and suggestions of ideal methods will be included in our assessment of data to better describe reservoirs, constructing better geological models, calculating oil and gas reserves and reducing risk and uncertainties; and thus, calculating accurate overall recovery factors.It may be concluded from this publication that since these techniques has been a significant factor in either enhancing or reconstructing a better and accurate geological model used in most of the studies which were carried out by the author in each field evaluation around the globe, I am highly confident that Egypt might benefit by using the same principals to better describe their reservoirs and accurately construct their geological models.
Uncertainty Analysis by Model Selection Technique and Its Application in Economic Valuation of a Large Field
Authors: Singh Harpreet , Srinivasan Sanjay 
Published: April 2013

Abstract
Uncertainty assessment for economic valuation of a field generally involves developing multiple subsurface realizations combined with different development scenarios, thereby rendering the task computationally expensive and time consuming. In addition, the task of updating the models with new information is equally daunting leading to enormous and unreasonable simplifications to the economic valuation procedure.
This paper presents a novel approach that renders the uncertainty assessment less cumbersome and more efficient/accurate with the help of a new uncertainty assessment approach. The proposed approach makes use of a model selection algorithm to reduce the number of subsurface realization necessary for uncertainty assessment. A model selection framework does the work of refining an initial suite of reservoir models to a final set of reservoir models that depict production characteristics close to the observed field history. Model selection algorithm attempts to group reservoir models based on the common connectivity characteristics exhibited by them and then retrieve the group exhibiting characteristics that are closest to the observed response for a reservoir. The model selection technique is thus an efficient way to reduce number of realizations and save computational time for doing uncertainty analysis, and yet be optimally constrained to the available data.
An illustrative example with a dataset for a large field is used to show the proposed methodology for economic valuation of a large field. Well testing data from two wells is used as two sets of history data for the model selection procedure. Real option valuation (ROV), a probabilistic approach, is used to infer the economics of the reservoir. The case described will demonstrate that the proposed approach is systematic, reduces the time of computation, and allows the rigorous application of economic analysis without making any undue simplifications and assumptions.
Modeling of the Change of Rock Petrophysical Properties Due to Sulfur Deposition in Sour Gas Reservoirs
Authors: Mahmoud M. A. , Gadallah M. A. 
Published: April 2013

AbstractDeposition of sulfur as a solid phase will result in plugging the pore space available for gas flow and reduce the reservoir productivity. For the isothermal conditions in the reservoir, the reduction in reservoir pressure below a critical value will cause the elemental sulfur to deposit in the formation. Sulfur deposition can cause severe loss in the pore space available for gas, and in will affect the gas well productivity.In this paper a new analytical was developed to predict the effect of sulfur deposition on the damage of the near- wellbore. The damage will be quantified through the investigation of the effect of sulfur deposition on the reservoir porosity, permeability, relative permeability, and the change in rock wettability due to sulfur deposition especially in the near-wellbore region. The developed model considered the change in reservoir gas properties with the change in reservoir pressure which has been neglected by previous investigators. The main objective of these models is to investigate the effect of radial distance on formation damage. Different rock and fluid properties accurate correlation were used in this model for better results prediction. Coreflood experiment was performed to determine the effect of sulfur deposition on the carbonate rock permeability, porosity, and wettability. The experiment was used to determine the effect of sulfur adsorption on the rock petrophysical properties.Model predictions showed that sulfur deposition depends on the radial distance from the well bore. The analytical model can be used to predict the sulfur deposition in the near-wellbore region. Sulfur deposition was found to have a great effect on the rock wettability, and in turn the gas production will be affected. It was confirmed experimentally that the sulfur deposition reduced the carbonate core porosity, permeability, and changed the contact angle. The contact angle increased which means sulfur adsorption on the rock surfaces changed the rock towards more gas wet rock.
Experimental Investigations of CO2 Solubility and Variations in Petrophysical Properties due to CO2 Storage in Carbonate Reservoir Rocks
Authors: Shedid Shedid A. , Salem Adel M. 
Published: April 2013

AbstractThe carbon dioxide (CO2) sequestration and storage in aquifers and depleted oil and gas reservoirs is eminently a feasible solution to provide substantial cut in overall emission into the atmosphere. The current need is to understand the factors affecting the CO2 sequestration potential and capacity of particular formation/reservoir.The purpose of this study is to investigate the CO2 storage in carbonate reservoir rocks under different conditions of pressure and temperature. Two groups of experiments were undertaken including; (1) investigating the CO2 solubility under different brine salinities, and different pressure and temperature conditions, and (2) studying the effect of CO2 storage time interval on porosity and permeability of carbonate reservoir rocks. Core storage experiments were undertaken using actual and similar core samples saturated with 25, 000 ppm NaCl brine. The potential of the CO2 storage capacity and variations in porosity and permeability are evaluated and quantified.The results showed that solubility of carbon dioxide decreases with increase in brine salinity and/or temperature. The increase of pressure causes a decrease in carbon dioxide solubility. In addition, the effect of temperature on carbon dioxide solubility diminishes above 120 °F and 4,000 psi pressure. The results also indicated that storage of carbon dioxide increases the petrophysical properties of porosity and permeability of carbonate rocks when the storage period is more than 150 days. On the other side, the CO2 storage for short time &lt; 7 days causes reduction in porosity and permeability of carbonate reservoir rock.The application of the attained results of this study is expected to have good impact on design storage process of carbon dioxide, validation of developed mathematical models, and improving our understanding of the process.
New Insights into Evaluating the Damage due to Calcium Sulfate Scale Precipitation during Low and High Salinity Water Injection
Authors: Mahmoud M. A. , Gadallah M. A. 
Published: April 2013

AbstractScale deposition is one of the most serious oilfield problems when two incompatible waters interact chemically and precipitate minerals. Typical examples are sea water, with high concentration of sulfate ions and formation waters with high concentrations of calcium, barium, and strontium ions. Mixing of these waters could cause precipitation of calcium sulfate, barium sulfate and/or strontium sulfate. Sea water treatment does not remove the entire sulfate ions from the injected water, at least 100 ppm sulfate will remain and even this low concentration may cause damage.This study was conducted to investigate the damage caused by deposition of calcium sulfate precipitation, describing the damage using material balance method, and then a new technique will be proposed to prevent the damage due to calcium sulfate. The result of the experimental data showed the reduction of permeability at least by 20% from its initial value due to sea water injection. The results from field data showed a reduction of the water injection rate from 25,000 to 5000 bbl/day in one month due to calcium sulfate precipitation. The results of the new analytical model showed that in about one month the injection rate will stop or the injection pressure will exceeds the fracture pressure of the formation.High salinity water injection caused severe formation damage and the injectivity declined faster compared to the low salinity water injection. The material balance calculations showed a good match between the experimental, field, and predicted data. The new method was very effective in preventing and removing sulfate precipitation. The cost of the new method was lower compared to the sulfate removal process and this method can be used with the injected water and no sulfate will precipitate.
Low-Productivity Sand Characterization and Identification of Bypassed Oil and Water Source with Advanced Production and Pulsed Neutron Logging, A Unique Key for Improving Field Productivity
Authors: Van Steene Marie , Abugren Yosra , Joshi Sameer , Thabet Enas , Ahmed Mohamed Mostafa 
Published: April 2013

Abstract
An oil well with two perforated zones had an initial production rate of ~2,400 BOPD with water traces. Within 3 months, production decreased to ~1,000 BOPD and water cut increased to &gt;25%. It was critical to identify the cause of decreasing productivity and increasing water cut to plan for remedial action.
The reservoir was evaluated by integrating several answers obtained from reservoir saturation characterization through use of pulsed neutron capture and water-flow log data, as well as from conventional and advanced production logging.
Production logging showed that water was sourced from the lower perforated interval, while only a small proportion of the flow came from the upper reservoir layer. Pulsed neutron logging confirmed a high amount of depletion in the zone below the lower perforation, with oil remaining in the upper part of the lower perforated zone and in the upper perforated zone. Bypassed oil was also found below the water-producing zone, confined between the oil/water contact and a thin shale break. This shale break is a major permeability barrier and allows lateral water movement through the high-permeability lower zone.
A multilayer test carried out with production logging tools showed that the productivity index of the upper zone was only one-tenth that in the lower zone, due to either intrinsically low permeability or high skin factor. The multilayer testing also showed that of the two comingled layers, the upper layer had approximately one hundredth the permeability of the lower layer. Reperforation of the upper zone resulted in only minor improvement in well production, thus confirming that the low productivity was not caused by high skin factor, but was due to low permeability.
From the testing, it is clear that to produce the oil from the upper zone, it will be necessary to produce the two zones separately, with different drawdown. Since similar conclusions were obtained in other wells in the field, these results provide a fieldwide strategy for improving field productivity.