bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feasibility of CO2-EOR in Shale-Oil Reservoirs: Numerical Simulation Study and Pilot Tests
Authors: Alfarge Dheiaa , Wei Mingzhen , Bai Baojun 
Published: August 2017

Abstract
Shale oil reservoirs such as Bakken, Niobrara, and Eagle Ford have become the main target for oil and gas investors as conventional formations started to be depleted and diminished in number. These unconventional plays have a huge oil potential; however, the predicted primary oil recovery is still low as an average of 7.5 %. Injecting carbon dioxide (CO2) to enhance oil recovery in these poor-quality formations is still a debatable issue among investigators. In this study, three steps of research have been integrated to investigate the parameters which control the success of CO2 huff-n-puff process in the field scale of shale oil reservoirs. Firstly, a numerical simulation study was conducted to upscale the reported experimental studies outcomes to the field conditions. The second step was to validate these numerical models with the field data from some of CO2-EOR pilots which were performed in Bakken formation, in North Dakota and Montana regions. Finally, statistical methods for Design of Experiments (DOE) have been used to rank the most important parameters affecting CO2-EOR performance in these unconventional reservoirs.
The Design of Experiments approved that the intensity of natural fractures (the number of natural fractures per length unit in each direction, I-direction, J direction, and K direction) and the conductivity of oil pathways (the average conductivity for the entire oil molecules path, from its storage (matrix) to the wellbore) are the two main factors controlling CO2-EOR success in shale oil reservoirs. However, the fracture intensity has a positive effect on CO2-EOR while the later has a negative effect. Furthermore, this study found that the porosity and the permeability of natural fractures in shale reservoirs are clearly changeable with the production time, which in turn, led to a clear gap between CO2 performances in the lab conditions versus to what happened in the field pilots. This work reported that the molecular diffusion mechanism is the key mechanism for CO2 to enhance oil recovery in shale oil reservoirs. However, the conditions of the candidate field and the production well criteria can enhance or downgrade this mechanism in the field scale. Accordingly, the operating parameters for managing CO2-EOR huff-n-puff process should be tuned according to the candidate reservoir and well conditions. Moreover, general guidelines have been provided from this work to perform successful CO2 projects in these complex plays.
Applicability of CO2-EOR in Shale-Oil Reservoirs Using Diagnostic Plots
Authors: Alfarge Dheiaa , Wei Mingzhen , Bai Baojun 
Published: August 2017

Abstract
Unconventional resources have played a significant role in changing oil industry plans recently. Shale formations in North America such as Bakken, Niobrara, and Eagle Ford have huge oil in place, 100–900 Billion barrels of recoverable oil in Bakken only. However, the predicted primary recovery is still below 10%. Therefore, seeking for techniques to enhance oil recovery in these complex plays is inevitable. In this paper, two engineering-reversed approaches have been integrated to investigate the feasibility of CO2 huff-n-puff process in shale oil reservoirs. Firstly, a numerical simulation study was conducted to upscale the reported experimental-studies outcomes to the field conditions. As a result, different forward diagnostic plots have been generated from different combinations of CO2 physical mechanisms with different shale-reservoirs conditions. Secondly, different backward diagnostic plots have been produced from the history match with CO2 performances in fields' pilots which were performed in Bakken formation of North Dakota and Montana. Finally, fitting the backward with the forward diagnostic plots was used to report and diagnose some findings regarding the injected-CO2 performance in field scale.
This study found that the porosity and permeability of natural fractures in shale reservoirs are significantly changed with production time, which in turn, led to a clear gap between CO2 performances in lab-conditions versus to what happened in field pilots. As a result, although experimental studies reported that CO2 molecular-diffusion mechanism has a significant impact on CO2 performance to extract oils from shale cores, pilot tests performances indicated a poor role for this mechanism in field conditions. Therefore, the bare upscaling process for the oil recovery improvement and the CO2-molecualr diffusion rate, which are obtained from CO2 injection in lab-cores, to the field scale via numerical simulations needs to be reconsidered. In addition, this study found that kinetics of oil recovery process in productive areas and CO2-diffusivity level are the keys to perform a successful CO2-EOR project. Furthermore, general guidelines have been produced from this work to perform successful CO2 projects in these complex plays. Finally, this paper provides a thorough idea about how CO2 performance is different in field scale of shale oil reservoirs as in lab-scale conditions.
North Atlantic Deep Water formation inhibits high Arctic contamination by continental perfluorooctane sulfonate discharges
Authors: Zhang Xianming , Zhang Yanxu , Dassuncao Clifton , Lohmann Rainer , Sunderland Elsie M. 
Published: August 2017

AbstractPerfluorooctane sulfonate (PFOS) is an aliphatic fluorinated compound with eight carbon atoms that is extremely persistent in the environment and can adversely affect human and ecological health. The stability, low reactivity, and high water solubility of PFOS combined with the North American phaseout in production around the year 2000 make it a potentially useful new tracer for ocean circulation. Here we characterize processes affecting the lifetime and accumulation of PFOS in the North Atlantic Ocean and transport to sensitive Arctic regions by developing a 3‐D simulation within the MITgcm. The model captures variability in measurements across biogeographical provinces (R2 = 0.90, p = 0.01). In 2015, the North Atlantic PFOS reservoir was equivalent to 60% of cumulative inputs from the North American and European continents (1400 Mg). Cumulative inputs to the Arctic accounted for 30% of continental discharges, while the remaining 10% was transported to the tropical Atlantic and other regions. PFOS concentrations declined rapidly after 2002 in the surface mixed layer (half‐life: 1–2 years) but are still increasing below 1000 m depth. During peak production years (1980–2000), plumes of PFOS‐enriched seawater were transported to the sub‐Arctic in energetic surface ocean currents. However, Atlantic Meridional Overturning Circulation (AMOC) and deep ocean transport returned a substantial fraction of this northward transport (20%, 530 Mg) to southern latitudes and reduced cumulative inputs to the Arctic (730 Mg) by 70%. Weakened AMOC due to climate change is thus likely to increase the magnitude of persistent bioaccumulative pollutants entering the Arctic Ocean.
Seismically invisible fault zones: Laboratory insights into imaging faults in anisotropic rocks
Authors: Kelly C. M. , Faulkner D. R. , Rietbrock A. 
Published: August 2017

AbstractPhyllosilicate‐rich rocks which commonly occur within fault zones cause seismic velocity anisotropy. However, anisotropy is not always taken into account in seismic imaging and the extent of the anisotropy is often unknown. Laboratory measurements of the velocity anisotropy of fault zone rocks and gouge from the Carboneras fault zone in SE Spain indicate 10–15% velocity anisotropy in the gouge and 35–50% anisotropy in the mica‐schist protolith. Greater differences in velocity are observed between the fast and slow directions in the mica‐schist rock than between the gouge and the slow direction of the rock. This implies that the orientation of the anisotropy with respect to the fault is key in imaging the fault seismically. For example, for fault‐parallel anisotropy, a significantly greater velocity contrast between fault gouge and rock will occur along the fault than across it, highlighting the importance of considering the foliation orientation in design of seismic experiments.
The characteristics and generation mechanism of small‐amplitude and large‐amplitude ESF irregularities observed by the C/NOFS satellite
Authors: Huang Chao‐Song 
Published: August 2017

AbstractIt is well understood that equatorial plasma bubbles are initiated in the bottomside F region and grow into the topside F region, producing equatorial spread F (ESF) irregularities in both bottomside and topside F regions. However, it is not known whether small‐amplitude and large‐amplitude irregularities have the same occurrence pattern and how the generation of small‐amplitude and large‐amplitude irregularities is related to the postsunset vertical plasma drift and potential seeding processes. In this study, we use ion density and velocity data measured by the Communications/Navigation Outage Forecasting System satellite during May 2008 to July 2014 to derive the longitude‐month distributions of the occurrence probability of ESF irregularities at different amplitudes. It is found that the occurrence probability of large‐amplitude irregularities is well correlated with the postsunset vertical plasma drift and that small‐amplitude irregularities do not show a clear pattern at low solar activity but is anticorrelated with that of large‐amplitude irregularities at moderate solar activity. That is, the months and longitudes with high occurrence probability of large‐amplitude irregularities are exactly those with low occurrence probability of small‐amplitude irregularities, and vice versa. ESF irregularities are mostly limited below 500 km during low solar activity in 2008–2010, but large‐amplitude irregularities can reach 700–800 km in altitude during moderate solar activity in 2011–2014. The generation of large‐amplitude ESF irregularities is controlled by the postsunset vertical plasma drift at both low and moderate solar activities. In contrast, small‐amplitude ESF irregularities at moderate solar activity occur more frequently in the areas where the postsunset vertical plasma drift is small.
The dependence of magnetospheric plasma mass loading on geomagnetic activity using Cluster
Authors: Sandhu J. K. , Yeoman T. K. , Rae I. J. , Fear R. C. , Dandouras I. 
Published: August 2017

AbstractUnderstanding changes in the magnetospheric mass density during disturbed geomagnetic conditions provides valuable insight into the dynamics and structure of the environment. The mass density plays a significant role in a variety of magnetospheric processes, such as wave propagation, magnetic reconnection rates, and radiation belt dynamics. In this study, the spatial variations of total plasma mass density are explored through the analysis of Cluster observations. Data from the WHISPER (Waves of High frequency and Sounder for Probing of Electron density by Relaxation) and CODIF (ion Composition and Distribution Function analyzer) instruments, on board the four Cluster spacecraft for a time interval spanning 2001–2012, are used to determine empirical models describing the distribution of the total plasma mass density along closed geomagnetic field lines. The region considered covers field lines within 5.9≤L< 9.5, corresponding to the outer plasmasphere, plasmatrough, and near‐Earth plasma sheet. This study extends previous work to examine and quantify spatial variations in the electron density, average ion mass, and total plasma mass density withDstindex. The results indicate that during periods of enhanced ring current strength, electron density is observed to decrease and average ion mass is observed to increase, compared with quiet geomagnetic conditions. The combination of these variations shows that although heavy ion concentration is enhanced, the decrease in plasma number density results in a general decrease in total plasma mass density during disturbed geomagnetic conditions. The observed decrease in mass density is in contrast to prevailing understanding and, due to the dependence of the Alfvén speed on mass density, has important implications for a range of plasma processes during storm time conditions (e.g., propagation of wave modes).
Detailed characteristics of radiation belt electrons revealed by CSSWE/REPTile measurements: Geomagnetic activity response and precipitation observation
Authors: Zhang K. , Li X. , Schiller Q. , Gerhardt D. , Zhao H. , Millan R. 
Published: August 2017

AbstractEarth's outer radiation belt electrons are highly dynamic. We study the detailed characteristics of relativistic electrons in the outer belt using measurements from the Colorado Student Space Weather Experiment (CSSWE) mission, a low Earth orbit (LEO) CubeSat, which traverses the radiation belt four times in one orbit (~1.5 h) and has the advantage of measuring the dynamic activities of the electrons including their rapid precipitation. We focus on the measured electron response to geomagnetic activity for different energies to show that there are abundant sub‐MeV electrons in the inner belt and slot region. These electrons are further enhanced during active times, while there is a lack of >1.63 MeV electrons in these regions. We also show that the variation of measured electron flux at LEO is strongly dependent on the local magnetic field strength, which is far from a dipole approximation. Moreover, a specific precipitation band, which happened on 19 January 2013, is investigated based on the conjunctive measurement of CSSWE, the Balloon Array for Radiation belt Relativistic Electron Losses, and one of the Polar Operational Environmental Satellites. In this precipitation band event, the net loss of the 0.58–1.63 MeV electrons (L = 3.5–6) is estimated to account for 6.8% of the total electron content.
Revisiting the structure of low‐Mach number, low‐beta, quasi‐perpendicular shocks
Authors: Wilson III L. B. , Koval A. , Szabo A. , Stevens M. L. , Kasper J. C. , Cattell C. A. , Krasnoselskikh V. V. 
Published: August 2017

AbstractA study of the structure of 145 low‐Mach number (M≤3), low‐beta (β≤1), quasi‐perpendicular interplanetary collisionless shock waves observed by the Wind spacecraft has provided strong evidence that these shocks have large‐amplitude whistler precursors. The common occurrence and large amplitudes of the precursors raise doubts about the standard assumption that such shocks can be classified as laminar structures. This directly contradicts standard models. In 113 of the 145 shocks (∼78%), we observe clear evidence of magnetosonic‐whistler precursor fluctuations with frequencies ∼0.1–7 Hz. We find no dependence on the upstream plasma beta, or any other shock parameter, for the presence or absence of precursors. The majority (∼66%) of the precursors propagate at ≤45° with respect to the upstream average magnetic field and most (∼87%) propagate ≥30° from the shock normal vector. Further, most (∼79%) of the waves propagate at least 20° from the coplanarity plane. The peak‐to‐peak wave amplitudes (δBpk‐pk) are large with a range of maximum values for the 113 precursors of ∼0.4–13 nT with an average of ∼2 nT. When we normalize the wave amplitudes to the upstream averaged magnetic field and the shock ramp amplitude, we find average values of ∼40% and ∼220%, respectively.
A fluid‐rich layer along the Nankai trough megathrust fault off the Kii Peninsula inferred from receiver function inversion
Authors: Akuhara Takeshi , Mochizuki Kimihiro , Kawakatsu Hitoshi , Takeuchi Nozomu 
Published: August 2017

AbstractInvestigation of fluid distribution along megathrust faults is an important issue, since the fluid affects frictional properties and thus slip behavior on faults. Scattered teleseismic phases, or receiver functions (RFs), have made significant contributions to understanding the fluid content of subducting plates beneath the onshore regions but have been rarely applied in offshore settings. In this study, we conducted receiver function inversion analysis to investigate detailed seismic properties near the megathrust fault using ocean bottom seismometers deployed off the Kii Peninsula, southwest Japan. RFs were calculated at high frequencies (up to 4 Hz), removing the effect of water reverberations from vertical component records. Our inversion was performed in two steps: first, we modeled sediment layer by a simple stacking method and then solved for deeper structure by a waveform inversion. The results indicate the presence of a thin low‐velocity zone (LVZ) of a thickness of 0.2–1.2 km with a S wave velocity of 0.7–2.4 km/s along the plate interface. We interpret this LVZ as thin fluid‐rich sediment layer between the overriding and subducting plates that acts as a pathway of fluid migration.
Estimating network effect in geocenter motion: Theory
Authors: Zannat Umma Jamila , Tregoning Paul 
Published: August 2017

AbstractGeophysical models and their interpretations of several processes of interest, such as sea level rise, postseismic relaxation, and glacial isostatic adjustment, are intertwined with the need to realize the International Terrestrial Reference Frame. However, this realization needs to take into account the geocenter motion, that is, the motion of the center of figure of the Earth surface, due to, for example, deformation of the surface by earthquakes or hydrological loading effects. Usually, there is also a discrepancy, known as the network effect, between the theoretically convenient center of figure and the physically accessible center of network frames, because of unavoidable factors such as uneven station distribution, lack of stations in the oceans, disparity in the coverage between the two hemispheres, and the existence of tectonically deforming zones. Here we develop a method to estimate the magnitude of the network effect, that is, the error introduced by the incomplete sampling of the Earth surface, in measuring the geocenter motion, for a network of space geodetic stations of a fixed size N. For this purpose, we use, as our proposed estimate, the standard deviations of the changes in Helmert parameters measured by a random network of the same size N. We show that our estimate scales as
and give an explicit formula for it in terms of the vector spherical harmonics expansion of the displacement field. In a complementary paper we apply this formalism to coseismic displacements and elastic deformations due to surface water movements.
Estimating network effect in geocenter motion: Applications
Authors: Zannat Umma Jamila , Tregoning Paul 
Published: August 2017

AbstractThe network effect is the error associated with the subsampling of the Earth surface by space geodetic networks. It is an obstacle toward the precise measurement of geocenter motion, that is, the relative motion between the center of mass of the Earth system and the center of figure of the Earth surface. In a complementary paper, we proposed a theoretical approach to estimate the magnitude of this effect from the displacement fields predicted by geophysical models. Here we evaluate the effectiveness of our estimate for two illustrative physical processes: coseismic displacements inducing instantaneous changes in the Helmert parameters and elastic deformation due to surface water movements causing secular drifts in those parameters. For the first, we consider simplified models of the 2004 Sumatra‐Andaman and the 2011 Tōhoku‐Oki earthquakes, and for the second, we use the observations of the Gravity Recovery and Climate Experiment, complemented by an ocean model. In both case studies, it is found that the magnitude of the network effect, even for a large global network, is often as large as the magnitude of the changes in the Helmert parameters themselves. However, we also show that our proposed modification to the definition of the center of network frame to include weights proportional to the area of the Earth surface that the stations represent can significantly reduce the network effect in most cases.
Evaluating the effectiveness of induced seismicity mitigation: Numerical modeling of wastewater injection near Greeley, Colorado
Authors: Brown Megan R. M. , Ge Shemin , Sheehan Anne F. , Nakai Jenny S. 
Published: August 2017

AbstractMitigation of injection‐induced seismicity in Greeley, Colorado, is based largely on proximity of wastewater disposal wells to seismicity and consists of cementation of the bottom of wells to eliminate connection between the disposal interval and crystalline basement. Brief injection rate reductions followed felt events, but injection rates returned to high levels, >250,000 barrels/month, within 6 months. While brief rate reduction reduces seismicity in the short term, overall seismicity is not reduced. We examine contributions to pore pressure change by injection from 22 wells within 30 km of the center of seismicity. The combined injection rate of seven disposal wells within 15 km of the seismicity (Greeley Wells) is correlated with the seismicity rate. We find that injection from NGL‐C4A, the well previously suspected as the likely cause of the induced seismicity, is responsible for ~28% of pore pressure increase. The other six Greeley Wells contribute ~28% of pore pressure increase, and the 15 Far‐field Wells between 15 and 30 km from the seismicity contribute ~44% of pore pressure increase. Modeling results show that NGL‐C4A plays the largest role in increased pore pressure but shows that the six other Greeley Wells have approximately the same influence as NGL‐C4A. Furthermore, the 15 Far‐field Wells have significant influence on pore pressure near the seismicity. Since the main mitigation action of cementing the bottom of wells has not decreased seismicity, mitigation based on reduced injection rates and spacing wells farther apart would likely have a higher potential for success.
Statistical distribution of polarization ratio for radar sea clutter
Authors: Yang Y. , Xiao S. P. , Wang X. S. , Zhang W. M. , Li Y. Z. 
Published: August 2017

AbstractAnalyzing the statistical property of polarization ratio of radar sea clutter provides a reference for radar detection. In this paper, statistical distributions of the amplitude and phase of polarization ratio for radar sea clutter are analyzed. The sea clutter amplitude distributions in horizontal and vertical polarization channels are analyzed with real sea clutter data at first. Based on this, statistical distributions of the amplitude of the polarization ratio are derived. Analysis results of real sea clutter data are coincident with the theoretical derivation of the distribution of polarization ratio amplitude for sea clutter and show that the distribution of polarization ratio phase approximates to Gaussian distribution.
Supervised Learning
Authors: Zhang Hao Helen 
Published: August 2017

AbstractSupervised learning is a central topic in statistics and machine learning. Two major types of supervised learning tasks are regression and classification. There is a rich literature of methods, algorithms, and theory developed for both regression and classification, including classical results for low‐dimensional problems and modern techniques for high‐dimensional data analysis. This article provides a review on supervised learning in terms of its basic principles, decision theory, and methods and tools. Model selection is a critical issue in supervised learning, and recent results in variable selection are also discussed.
Bayesian Networks in Project Management
Authors: Yet Barbaros 
Published: August 2017

AbstractBayesian networks (BNs) offer unique benefits for combining data and expert knowledge to model complex joint probability distributions. Recent advances in inference algorithms enabled efficient computation of BNs with both discrete and continuous variables that are also calledhybrid BNs. Consequently, BNs have been widely used as risk assessment and decision support tools in various domains including project management. This article illustrates the use of BNs in different aspects of project management and gives an overview of the relevant studies in this domain.