bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of Photonic Crystal based Back Reflectors for Light Management and Enhanced Absorption in Amorphous Silicon Solar Cells
Authors: Curtin Benjamin , Biswas Rana , Dalal Vikram 
Published: November 2009

AbstractPhotonic crystal based back-reflectors are an attractive solution for light management and enhancing optical absorption in thin film solar cells, without undesirable losses. We have fabricated prototype photonic crystal back-reflectors using photolithographic methods and reactive-ion etching. The photonic crystal back-reflector has a triangular lattice symmetry, a thickness of 250 nm, and a pitch of 765 nm. Scanning electron microscopy images demonstrate high quality long range periodicity. An a-Si:H solar cell device was grown on this back-reflector using standard PECVD techniques. Measurements demonstrate strong diffraction of light and high diffuse reflectance by the photonic crystal back-reflector. The photonic crystal back-reflector increases the average photon collection by ˜9% in terms of normalized external quantum efficiency, relative to a reference device on a stainless steel substrate with an Ag coated back surface.
Viscoelastic Modeling and Reliability Assessment of Microelectronics Packages
Authors: Karmarkar Aditya , Zhai Charlie , Xu Xiaopeng , Lin Xiao , Rollins Greg , Moroz Victor 
Published: November 2009

AbstractViscoelastic stress relaxation occurs at operating temperature in underfill materials of flip-chip packages with high power devices. Multi-level finite element analysis is performed to study the impact of the viscoelastic relaxation on package reliability. The stress simulations reveal that the relaxation in underfill material leads to higher stress concentration in solder bumps. The failure analysis shows that the induced high stress develops higher crack driving forces. The results demonstrate that the underfill material property such as viscosity can shift failure mode from die corner delamination to near bump delamination. Therefore, the numerical study can be used as a guideline to select underfill material for package reliability improvements.
High Performance Pyrolytic Graphite Heat Spreaders – Near Isotropic Structures and Metallization
Authors: Lemak Richard , Moskaitis Robert , Pickrell David , Kupp Don , Yocum Adam 
Published: November 2009

AbstractManufacturers of modern high performance military and commercial electronics are steadily increasing the power density of the components of their devices. The increase of small component size and/or higher power densities results in large component heat flux levels. In applications from laser diodes, radar transmit/receive (T/R) modules and LED lighting, solutions to thermal issues through advancements in heat spreaders and heat sink design are needed to continue the performance improvement of these devices and structures.Advanced materials for heat spreaders should have high thermal conductivity, a coefficient of thermal expansion (CTE) that matches the electronics die, and a reasonable cost. Diamond, for example, has the highest thermal conductivity of any known solid material at room temperature, combined with a high modulus of elasticity, but has a CTE mismatch with silicon (die material) and a high relative cost.As an alternative material, PYROID® HT pyrolytic graphite has a thermal conductivity of 1700 W/m °K in the x-y plane of the material (7 W/m °K in the z plane), costs more than 250 times less than diamond produced by chemical vapor deposition (CVD), and has a modulus of elasticity much lower than diamond. The lower modulus of elasticity of this material results in an order of magnitude lower thermal stress level between the spreader and the die than diamond.In one case study involving a laser diode cooling application, the spreader/die is nearly two-dimensional. Thus, pyrolytic graphite can be oriented with high conductivity in the direction into the spreader and away from the die (x-y plane), and the low conductivity direction (z direction) along the die where minimal conduction is needed. For the cases where a three-dimensional spreader is required, laminated composite structures of pyrolytic graphite have been developed where the equivalent isotropic conductivity is over two times greater than the conductivity of copper. The graphite layers are metallized so that they can be bonded together by soldering and/or dies can also be attached by soldering. The adhesion of the metal layers to the graphite has been tested with several standard techniques. Graphite metallization techniques, thermal performance modeling and analysis of stress levels due to CTE mismatching will be discussed in this paper.
ZnO Microcrystals for Light Emitting Diode and Photovoltaic Applications with Integration on Flexible Substrates
Authors: Cole Jesse J , Jacobs Heiko 
Published: November 2009

AbstractWe report a new integration approach to produce arrays of ZnO microcrystals for optoelectronic and photovoltaic applications. Demonstrated applications are n-ZnO/p-GaN heterojunction LEDs and photovoltaic cells. The integration process uses an oxygen plasma treatment in combination with a photoresist pattern on Magnesium doped GaN substrates to define a narrow sub-100nm width nucleation region. ZnO is synthesized in the defined areas by a hydrothermal technique using zinc acetate and hexamethylenetetramine precursors. Nucleation is followed by lateral epitaxial overgrowth producing single crystal disks of ZnO. The process provides control over the dimension and location of the ZnO crystals. The quality of the patterned ZnO is high; the commonly observed defect related emission in the electroluminescence spectra is suppressed and a single near-band-edge UV peak is observed. Transfer printing of the ZnO microcrystals onto a flexible substrate is also demonstrated in the context of transparent flexible electronics.
Effective Zonal Isolation for CO2 Sequestration Wells
Authors: Sweatman R. E. , Santra A. , Kulakofsky D. S. , Calvert D. G. J. 
Published: November 2009

Abstract
CO2 geologic-sequestration (GS) via injection wells into suitable subsurface strata is a safe, cost-effective way to mitigate climate change. However, using well cements to zonally isolate CO2 for up to 1,000 years, as required for permanent reservoir storage, may be challenging. Some researchers claim that cement fails when exposed to CO2, leading to potential leakage to the atmosphere or into underground structures that may contain drinking water. Other investigators show cement samples from 30 to 50 year-old wells that have maintained sealing integrity and prevented CO2 leakage, even though some degree of carbonation was found. This paper presents likely reasons for this disparity between research lab test results and actual well performance data, along with best practices to provide efficient cement-based zonal isolation of CO2 storage zones. Also discussed are recent laboratory results from testing cement samples surrounded by formation material treated at two different downhole conditions. In one case, the cement specimens were treated with a 40% humid CO2 at 140°F and 2,000 psi whereas in the second case they were treated with saturated CO2 in water at 200°F and 2,000 psi for various time intervals. Results show that samples of carefully designed cement systems had a mild carbonation without any sign of loss of mechanical or sealing integrity which could lead to zonal isolation failure. A newly-applied laboratory testing method used for decades for other purposes is proposed to determine CO2 sealing performance by cement in a relatively short time period compared to previous methods. In summary, this paper discusses a comprehensive approach that may be taken to help ensure long-term, effective CO2 zonal isolation in new wells, in existing wells (via remedial solutions), and in wells to be plugged and abandoned.
Simulating CO2 EOR Process: Numerical Investigation Based on the Experimental Results
Authors: Berenblyum R. , Calderon G. , Surguchev L. 
Published: November 2009

Abstract
Many experimental and analytical investigations of the CO2 performance at reservoir conditions have been performed world-wide in the recent years. However integrating many of those findings into reservoir simulation models still remains an open issue.
In this manuscript we address only the reservoir aspects of the CO2 injection to Enhance Oil Recovery (EOR) leaving behind transport, metal corrosion and economic issues related to CO2 injection. CO2 is an efficient agent to increase oil recovery, especially, if conditions of oil displacement are miscible. However, CO2"gas like" low viscosity at reservoir conditions may cause severe viscous fingering and displacement front instability resulting in low sweep efficiency. CO2 may boost precipitation of waxes and asphaltenes, thus reducing productivity or completely plugging the wells. CO2, being a chemically active component at reservoir conditions, may provoke chemical reactions and mineralogical changes in situ resulting in increased permeability, loose of sealing properties of the cap rock.
Based on the laboratory investigations we aim at building a consistent model to evaluate CO2 injection performance at reservoir conditions. The laboratory studies were conducted in such a way that a single or several natural phenomena were isolated and individually studied. The experimental results allowed us to gain a better knowledge of the process mechanisms. Doing history matching simulations of the experiments we evaluate critical parameters, validate and calibrate numerical models. The complexity of the simulation model is gradually built up from simple experiments to full scale simulation. The mechanisms addressed investigated are:
Viscous fingering; Multiphase compositional effects; Flow in naturally fractured porous media (diffusive fluxes and gravity segregation); CO2 dissolution in aqueous phase; Chemical interaction between rock and CO2; CO2 mobility control agents.
Special attention in this paper is paid to the viscous effects during CO2 injection at above critical reservoir conditions. The laboratory experiments were performed with different oils. Pure CO2 and CO2 -rich oleic phases were injected to investigate gravitational and viscous effects in the porous medium. It was shown that using relative permeabilities dependant on rate and interfacial tension can improve the accuracy of CO2 injection simulation. Water Alternating Gas (WAG) injection was shown to be an effective way for remediation of viscous fingering.
Conclusions on various CO2 injection phenomena and ability of reservoir modelling tools to handle those phenomena are drawn.
Geologic Heterogeneity in Basin-Scale Geologic Carbon Storage: Examples from the Powder River Basin, NE Wyoming and SE Montana
Authors: Melick Jesse J. , Gardner M. H. , Uland M. J. 
Published: November 2009

AbstractGeologic carbon storage (GCS) requires consideration of storage capacity, injectivity and migration of gigatons of supercritical fluids in sedimentary basins. However, the size of basin-scale GCS models requires simplification that limits retention of geologic heterogeneity. Homogeneous GCS models (uniform and average properties in large cells) facilitate initial basin storage evaluation useful in screening, but cannot account for the actual reservoir architecture affecting both reaction and flow rates in heterogeneous media. The generation and integration of geological and petrophysical models (multi-field, regional aquifers) presented here highlight the uncertainty and risk created by using simplified GCS models to direct research and make policy decisions. This paper emphasizes a workflow that utilizes the natural hierarchy within sedimentary architecture to geologically upscale a family of static geomodels that retain multiple scales and types of heterogeneity. More importantly, geologic controls on heterogeneity can be explicitly manipulated to manage heterogeneity distributions known to change through the life of petroleum reservoirs. There is no reason GCS will not follow a similar path.
Cost-Effective Remediation Strategies for Storing CO2 in Geologic Formations
Authors: Kuuskraa V. A. 
Published: November 2009

Abstract
Because storage of CO2 for climate change mitigation is still an emerging industry, very little has been written on the topic of cost-effective remediation strategies for geological storage of CO2. The purpose of this presentation and paper is to begin to fill this gap in publically available technical information.
Much of the background that serves as the technical and experiential source for remediation of CO2 storage wells and sites has been drawn from our experience with the gas storage and the CO2 enhanced oil recovery industries. This paper compiles these past experiences and adds an overlay of the unique facets of geological storage for establishing a remediation strategy and a workable plan for CO2 storage, particularly in saline formations.
In addition, the paper highlights the importance of thorough site selection, rigorous well design and completion practices and the need for a monitoring system that provides an "early warning" of impending problems. The paper also reviews advanced well remediation strategies used by the gas storage industry to restore well productivity of potential value to establishing cost-effective CO2 storage in lower permeability formations.
Construction of a Mechanical Earth Model and Wellbore Stability Analysis for a CO2 Injection Well
Authors: Lee D. , Singh V. , Berard T. 
Published: November 2009

Abstract
A mechanical earth model (MEM) and wellbore stability analysis were completed for a CO2 injection well in the Eau Claire shale where in offset wells, severe borehole enlargements were experienced. This shale serves as a caprock for the Mt. Simon injection zone in the planned CO2 injection well and therefore, borehole enlargement had to be minimized to provide zonal isolation and containment for injection. After drilling the CO2 injection well, a comparison was made between the predrill prediction and actual results. Borehole enlargement was experienced at depths predicted by the predrill model, but borehole enlargement severity was minimized with improved drilling practices. To determine the formation stability, an MEM was built using offset well data and was calibrated with both borehole and regional data. Multiple stress models were examined, and calibration for unconfined compressive strength (UCS) values was provided from core tests in other wells. After calibration, the data was correlated to the planned well trajectory using formation tops, and the stresses were recalculated. The largest areas of uncertainty in the predrill prediction existed in the Eau Claire shale UCS and the maximum horizontal stress magnitude. Available shale core testing for UCS was likely biased toward stronger intact samples. The principle stress ordering and magnitudes from offset well testing showed a shallow thrust fault environment with deeper strike-slip environment.
Increasing mud weight to reasonable levels would not prevent shear failure in the Eau Claire shale as predicted by the models. Therefore, it was important to monitor the wellbore while drilling through the shale and mitigate borehole enlargement. For monitoring borehole enlargement, material across the shakers from the drilling process was examined for cavings. Digital pictures of the rock cuttings/cavings samples were taken before reaching the Eau Claire shale and through the interval. Mechanical vibration and backreaming were kept to a minimum across the Eau Claire shale while this section was open to minimize borehole enlargement.
Computational Studies of Two-Phase Cement-CO2-Brine Interaction in Wellbore Environments
Authors: Carey J. W. , Lichtner P. C. 
Published: November 2009

Abstract
Wellbore integrity is essential to ensuring long-term isolation of buoyant supercritical CO2 during geologic sequestration of CO2. In this report, we summarize recent progress in numerical simulations of cement-brine-CO2 interactions with respect to migration of CO2 outside of casing. Using typical values for the hydrologic properties of cement, caprock (shale) and reservoir materials, we show that the capillary properties of good quality cement will prevent flow of CO2 into and through cement. Rather, CO2, if present, is likely to be confined to the casing-cement or cement-formation interfaces. CO2 does react with the cement by diffusion from the interface into the cement, in which case it produces distinct carbonation fronts within the cement. This is consistent with observations of cement performance at the CO2-enhanced oil recovery SACROC Unit in West Texas (Carey et al. 2007). For poor quality cement, flow through cement may occur and would produce a pattern of uniform carbonation without reaction fronts. We also consider an alternative explanation for cement carbonation reactions as due to CO2 derived from caprock. We show that carbonation reactions in cement are limited to surficial reactions when CO2 pressure is low (&lt; 10 bars) as might be expected in many caprock environments. For the case of caprock overlying natural CO2 reservoirs for millions of years, we consider Scherer and Huet's (2009) hypothesis of diffusive steady-state between CO2 in the reservoir and in the caprock. We find that in this case, the aqueous CO2 concentration would differ little from the reservoir and would be expected to produce carbonation reaction fronts in cements that are relatively uniform as a function of depth.
Aquifer Management to Accelerate CO2 Dissolution and Trapping
Authors: Anchliya A. , Ehlig-Economides C. 
Published: November 2009

AbstractBulk phase CO2 injection can provide substantive reduction in CO2 emissions only if additional brine is produced out of the system to address relevant risk arising from aquifer pressurization (Anchliya 2009). This approach addresses the pressurization risk, but does not address the problem of CO2 accumulating at the top of the aquifer. The performance of bulk CO2 injection schemes highly depends on the seal integrity assessment and presence of thieve zones. The accumulated pocket of free CO2 would readily leak through a breach in the aquifer seal. Ideally, the aquifer should be monitored as long as the free CO2 is present, but the free CO2 is expected to remain for more than 1000 years. Long term monitoring of the seal integrity and avoiding leakage will be very costly.An engineered system is proposed to avoid aquifer pressurization and accelerate CO2 dissolution and trapping (to avoid free CO2 below the top seal). This system would position a horizontal brine injection well above and parallel to a horizontal CO2 injection well with horizontal brine production wells drilled parallel to the CO2 injection well at a specified lateral spacing. Simulations showed that this configuration prevents CO2 accumulation at the top of the aquifer during injection and that 90% of the CO2 is permanently dissolved or trapped during injection after 50 years, including the 30 years of injection. This approach would greatly reduce the risk of CO2 leakage both during and forever after injection.The controlled injection of CO2 with this technique reduces the uncertainty about the long-term fate of the injected CO2; prevents CO2 from migrating toward potential outlets or sensitive areas; and increases the volume of CO2 that can be stored in a closed aquifer volume during the CO2 injection period.Field scale compositional simulation cases are discussed, and sensitivity studies provide guidelines for well spacing and flow rates depending on aquifer properties and the volume of CO2 to be stored. Although this technique requires additional drilled wells, the engineered case significantly reduces the reservoir volume required to effectively sequester a given volume of CO2 and the increase in the cost due to addition wells is compensated by dramatic reduction in monitoring cost.
Sensitivity Analysis of Salt Precipitation and CO2-Brine Displacement in Saline Aquifers
Authors: Zeidouni M. , Pooladi-Darvish M. , Keith D. 
Published: November 2009

Abstract
Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO2. Among various mechanisms, CO2 can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO2. Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the aquifer in the vicinity of the wellbore, and can lead to reduction in injectivity. In an earlier work, we developed an analytical model to predict the precipitated salt saturation and CO2 displacement around the wellbore. In this study we analyse the effect of different parameters on the salt precipitation and CO2-brine displacement. The parameters include: aquifer pressure, temperature, salinity, relative permeability functions, and volume change upon mixing.
The results indicate that increasing the salinity, increases the CO2 spread due to reduced vaporization and dissolution. Furthermore, it is found that the amount of salt precipitation increases and the maximum plume size decreases with pressure increase. The CO2 plume expands by increasing the temperature. However, the effect of temperature on the salt precipitation depends on the pressure.
Increasing relative permeability of the aqueous phase (or decreasing the relative permeability of the gaseous phase) causes both the amount of precipitated salt saturation and the extent of the CO2 plume to decrease. It is also fond that the effect of volume change upon mixing may be negligible at higher pressures.
For the range of parameters studied, both the solid salt saturation and the plume extent are very sensitive to the relative permeability of the aqueous phase. While the plume size is also very sensitive to the pressure, the salt precipitation is most affected by the brine salinity.
Detecting and Monitoring CO2 With P-Wave Velocity and Resistivity From Both Laboratory and Field Scales
Authors: Xue Z. , Kim J. , Mito S. , Kitamura K. , Matsuoka T. 
Published: November 2009

Abstract
Sequestration of Carbon Dioxide (CO2) into saline aquifers has been proposed as one of the most practical options of all geological sequestration possibilities. When saline aquifers are to be used to sequester CO2 for long periods, it will be necessary to monitor the migration and diffusion of CO2 in those reservoirs. Monitoring of geological sequestration has been identified as one of the highest priority needs in several recent international conferences on greenhouse gas control technologies. Monitoring is necessary to confirm the containment of CO2, to assess leakage paths, and to gain understanding of interactions between CO2, the rock-forming minerals, and formation fluids. Recently CO2 monitoring has moved to next stage for the purpose of leakage detection and quantification of CO2 stored in reservoirs. What kinds of monitoring methods we could use and do the methods have sufficient resolution and detection levels need to be addressed urgently. Seismic surveys provide the most attractive approach for obtaining the spatial coverage required for mapping the location and movement of CO2 in the subsurface. However, from the first Japanese pilot project, time-lapse sonic logging results showed P-wave velocity becomes less sensitive when the CO2 saturation up to 20%, while resistivity kept increasing with increase in CO2 saturation. This paper describes the results of P-wave velocity and resistivity measurements when injecting CO2 into water-saturated porous sandstones at laboratory and the results of comparison between P-wave velocity and resistivity changes obtained from both laboratory-and field-scales.