Recent Submissions

  • Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

    Karuthedath, Safakath; Gorenflot, Julien; Firdaus, Yuliar; Chaturvedi, Neha; De Castro, Catherine S. P.; Harrison, George T.; Khan, Jafar Iqbal; Markina, Anastasia; Albalawi, Ahmed; Peña, Top Archie Dela; Liu, Wenlan; Liang, Ru-Ze; Sharma, Anirudh; Paleti, Sri Harish Kumar; Zhang, Weimin; Lin, Yuanbao; Alarousu, Erkki; Anjum, Dalaver H.; Beaujuge, Pierre; De Wolf, Stefaan; McCulloch, Iain; Anthopoulos, Thomas D.; Baran, Derya; Andrienko, Denis; Laquai, Frédéric (Nature Materials, Springer Science and Business Media LLC, 2020-10-26) [Article]
    In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor–acceptor interface should equally control exciton dissociation. Here, we demonstrate that in low-bandgap non-fullerene acceptor (NFA) BHJs ultrafast donor-to-acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover, sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies, since energy level bending at the donor–NFA interface caused by the acceptors’ quadrupole moments prevents efficient exciton-to-charge-transfer state conversion at low IE offsets. The same bending, however, is the origin of the barrier-less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA-based blends, and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low-bandgap NFAs.
  • Electrification at water–hydrophobe interfaces

    Nauruzbayeva, Jamilya; Sun, Zhonghao; Gallo Junior, Adair; Ibrahim, Mahmoud; Santamarina, Carlos; Mishra, Himanshu (Nature Communications, Springer Science and Business Media LLC, 2020-10-20) [Article]
    Abstract The mechanisms leading to the electrification of water when it comes in contact with hydrophobic surfaces remains a research frontier in chemical science. A clear understanding of these mechanisms could, for instance, aid the rational design of triboelectric generators and micro- and nano-fluidic devices. Here, we investigate the origins of the excess positive charges incurred on water droplets that are dispensed from capillaries made of polypropylene, perfluorodecyltrichlorosilane-coated glass, and polytetrafluoroethylene. Results demonstrate that the magnitude and sign of electrical charges vary depending on: the hydrophobicity/hydrophilicity of the capillary; the presence/absence of a water reservoir inside the capillary; the chemical and physical properties of aqueous solutions such as pH, ionic strength, dielectric constant and dissolved CO2 content; and environmental conditions such as relative humidity. Based on these results, we deduce that common hydrophobic materials possess surface-bound negative charge. Thus, when these surfaces are submerged in water, hydrated cations form an electrical double layer. Furthermore, we demonstrate that the primary role of hydrophobicity is to facilitate water-substrate separation without leaving a significant amount of liquid behind. These results advance the fundamental understanding of water-hydrophobe interfaces and should translate into superior materials and technologies for energy transduction, electrowetting, and separation processes, among others.
  • How Humidity and Light Exposure Change the Photophysics of Metal Halide Perovskite Solar Cells

    Ugur, Esma; Alarousu, Erkki; Khan, Jafar Iqbal; Vlk, Aleš; Aydin, Erkan; de Bastiani, Michele; Albalawi, Ahmed; Gonzalez Lopez, Sandra P.; Ledinský, Martin; De Wolf, Stefaan; Laquai, Frédéric (Solar RRL, Wiley, 2020-09-24) [Article]
    Metal halide perovskites exhibit outstanding optical and electronic properties, but are very sensitive to humidity and light-soaking. In this work, the photophysics of perovskites that have been exposed to such conditions are studied and, in this context, the impact of excess lead iodide (PbI2) is revealed. For exposed samples, the formation of subbandgap states and increased trap-assisted recombination is observed, using highly sensitive absorption and time-resolved photoluminescence (TRPL) measurements, respectively. It appears that such exposure primarily affects the perovskite surface. Consequently, on n–i–p device level, the spiro-OMeTAD/perovskite interface is more rapidly affected than its buried electron-collecting interface. Moreover, both stoichiometric and nonstoichiometric MAPbI3-based solar cells show reduced device performance mainly due to voltage losses. Overall, this study brings forward key points to consider in engineering perovskite solar cells with improved performance and material stability.
  • Coarse-fine mixtures subjected to repetitive Ko loading: Effects of fines fraction, particle shape, and size ratio

    Kim, Sang Yeob; Park, Junghee; Lee, Jong Sub (Powder Technology, Elsevier BV, 2020-09-19) [Article]
    This study explores the effects of fines fraction, particle shape, and size ratio on the long-term response of sand-silt mixtures with fines fraction FF = 0-to-100% during Ko-loading cycles i = 104. The void ratio for all specimens evolves toward the asymptotic terminal void ratio eT that captures the transition from coarse-to-fine controlled behavior. Shear wave velocity versus intergranular eC and equivalent intergranular (eC)eq void ratios estimates the participation rate of fines-in-sand for the force chain. More fine particles contribute to the load-carrying skeleton as the particle shape becomes rounder and the size ratio decreases. In contrast, shear wave velocity against interfine eF and equivalent interfine (eF)eq void ratios reflects the reinforcing effect of coarse grains floating in the load-carrying fines matrix. The rounder sand in the fine-dominant matrix leads to more significant fabric changes. Clearly, there is a transition from coarse-to-fine controlled repetitive load-deformation response that promotes the reassessment of current soil classification systems.
  • Text Analysis Reveals Major Trends in Exploration Geophysics

    Eltsov, Timofey; Yutkin, Maxim; Patzek, Tadeusz (Energies, MDPI AG, 2020-09-02) [Article]
    Evolution of professional language reveals advances in geophysics: researchers enthusiastically describe new methods of surveying, data processing techniques, and objects of their study. Geophysicists publish their cutting-edge research in the proceedings of international conferences to share their achievements with the world. Tracking changes in the professional language allows one to identify trends and current state of science. Here, we explain our text analysis of the last 30 annual conferences organized by the Society of Exploration Geophysicists (SEG). These conferences are among the largest geophysical gatherings worldwide. We split the 21,864 SEG articles into 52 million words and phrases, and analyze changes in their usage frequency over time. For example, we find that in 2019, the phrase “neural network” was used more often than “field data.” The word “shale” became less commonly used, but the term “unconventional” grew in frequency. An analysis of conference materials and metadata allows one to identify trends in a specific field of knowledge and predict its development in the near future.
  • A Physics Based Model of Enhanced Gas Production in Mudrocks

    Haider, Syed; Patzek, Tadeusz (American Association of Petroleum Geologists, 2020-08-20) [Conference Paper]
    Gas flow in mudrocks depends on the complex, multiscale connectivity among nanopores, microfractures and macrofractures. Hydraulic fractures stimulate reservoir volume near a horizontal well and create other fractures at all scales. Elsewhere, we have described the Stimulated Reservoir Volume (SRV) as a fractal with its own fracture network that accesses the organic-rich matrix. In the practically impermeable mudrock, the known volume of fracturing water (and proppant) must create an equal volume of fractures at all scales. Thus, we can constrain the physical structure of SRV, i.e., the number of macrofractures and surface area created after hydrofracturing. Nanopores in the organic matrix act as the source of almost all gas. Here, we present a comprehensive, physics-based microscale model of (a) the increased permeability to gas flow in a mudrock and (b) the effects of smallest nanopores on well production rates and gas storage capacity in this mudrock.
  • Implications for controls on Upper Cambrian microbial build-ups across multiple-scales, Mason County, Central Texas, USA

    Khanna, Pankaj; Pyrcz, Michael; Droxler, André W.; Hopson, Heath H.; Harris, Paul M.(Mitch); Lehrmann, Daniel J. (Marine and Petroleum Geology, Elsevier BV, 2020-07-18) [Article]
    The morphological architecture and distribution of modern and ancient carbonate systems has been shown to follow spatial-self-organization, however, limited studies describe the morphometrics of microbial carbonates. Upper Cambrian microbial-build-ups outcropping in Central Texas, are exposed laterally (plan view), enabling a study of their morphological architecture and spatial distribution. Drone imagery was acquired to capture the outcrop features and develop a digital terrain model (cm scale resolution) for a bedding plane outcrop (600 × 200 m in size). Four scales of microbial growth (S1- few dm, S2- few m, S3- few tens of m, and S4- few hundreds of m) were identified and mapped. A series of morphometric analysis including Ripley's k, univariate, multivariate, and grouping were conducted and results demonstrate that, the scales S1, S2, and S3 display clustering and the spatial organization of microbial-buildups is naturally organized and not random. Further, as the size of the build-ups increases (from S1–S4), the anisotropy (length/width) increases, their shape becomes oblong, and they become aligned (S2–S4) with the inferred regional winds and tide-associated currents (NE-SW according to the present geography). The S1 scale does not align itself with the regional currents; instead, the build-ups behaved as a baffle during growth, and modified the currents locally, leading to preferential alignment at the edges within S2. As the scales increases in sizes (S2, S3, S4), there is competition for space, and due to regional currents, the larger scales preferentially align parallel to high-energy currents. The trends and spatial relationships identified in this study are particularly relevant and provide a scenario for sub-seismic scale heterogeneities for subsurface microbial hydrocarbon reservoirs.
  • Chemical Compositions in Salinity Waterflooding of Carbonate Reservoirs: Theory

    Yutkin, Maxim; Radke, Clayton J.; Patzek, Tadeusz (American Chemical Society (ACS), 2020-06-18) [Preprint]
    Higher oil recovery after waterflood in carbonate reservoirs is attributed to increasing water wettability of the rock that in turn relies on complicated surface chemistry. However, calcite mineral reacts withaqueous solutions, and can alter substantially the composition of injected water by mineral dissolution. Care-fully designed chemical and/or brine flood compositions in the laboratory may not remain intact while theinjected solutions pass through the reactive reservoir rock. This is especially true for a low-salinity waterfloodprocess, where some finely-tuned brine compositions can improve flood performances, whereas others cannot.We present a 1D reactive transport numerical model that captures the changes in injected compositions dur-ing water flow through porous carbonate rock. We include highly coupled bulk aqueous and surface carbonate-reaction chemistry, detailed reaction and mass transfer kinetics, 2:1 calcium ion exchange, and axial dispersion.At typical calcite reaction rates, local equilibrium is established immediately upon injection. Using an open-source algorithm (Charlton and Parkhurst 2011), we present a design tool to specify chemical/brine floodingpackages that correct for composition alteration by carbonate rock.Here, we present a comprehensive 1D reactive transport model and validate it against analytic solutionsfor rock dissolution, ion exchange, and longitudinal dispersion, each considered separately. A companion papercompares the proposed theory against experiments on core plugs of Indiana limestone that serve as high velocityprobes for reaction-controlled and mass-transfer-controlled dissolution. Finally, in another companion paper,we give examples of how injected salinity compositions deviate from those designed in the laboratory for water-wettability improvement based on contact angles, zeta potentials, surface charge densities, and ion exchange.How to correct the design chemical packages for exposure to reactive rock is also discussed in there.
  • A pseudo-kinetic model to simulate phase changes in gas hydrate bearing sediments

    Teymouri, Mehdi; Sánchez, Marcelo; Santamarina, Carlos (Marine and Petroleum Geology, Elsevier BV, 2020-06-12) [Article]
    Modeling of the phase transitions anticipated in gas hydrate bearing sediments (GHBS) is critical for a proper understanding of time-dependent changes in states and volumes (e.g. the production of methane from this type of soils). We propose a new pseudo-kinetic approach to simulate the typical phase changes anticipated in GHBS, using published experimental results involving gas hydrate dissociation that are the basis of a widely used kinetic model. The proposed pseudo-kinetic model is formulated in the pressure-temperature (P-T) plane and assumes a rate of gas hydrate dissociation (or formation) proportional to the distance between the current state and the phase boundary. The model consists of only one parameter and is simple to implement in numerical simulators. A similar concept is used to model ice formation/thawing phenomena, but based on the ice/liquid-water phase boundary. We implemented the pseudo-kinetic model in a fully coupled thermo-hydro-chemo-mechanical (THCM) finite element code and validated it against experimental results performed on the dissociation of synthetic gas hydrate. We also evaluated the pseudo-kinetic model using synthetic cases covering several scenarios associated with gas hydrate formation/dissociation and ice formation/thawing. The model successfully reproduced the gas production test from a natural GHBS core from Korea (scaled gas venting experiment over 14 h), and also the formation of gas hydrate and ice in permafrost in Alaska (over 2 × 106 years). -The analyses show the versatility of the proposed pseudo-kinetic approach by applying it to model the different types of phase transitions typically encounter in GHBS. The simple formulation, easy implementation in numerical simulator, and reduced number of parameters (only one per phase change) make this model an attractive option for simulating phase transformations in problems involving GHBS.
  • Extraction, Characterization, and Anticoagulant Activity of a Sulfated Polysaccharide from Bursatella leachii Viscera

    Dhahri, Manel; Sioud, Salim; Dridi, Rihab; Hassine, Mohsen; Boughattas, Naceur A.; Almulhim, Fatimah; Al-Talla, Zeyad; Jaremko, Mariusz; Emwas, Abdul-Hamid M. (ACS Omega, American Chemical Society (ACS), 2020-06-10) [Article]
    Bioactive compounds for drug discovery are increasingly extracted and purified from natural sources including marine organisms. Heparin is a therapeutic agent that has been used for several decades as an anticoagulant. However, heparin is known to cause many undesirable complications such as thrombocytopenia and risk of hemorrhage. Hence, there is a need to find alternatives to current widely used anticoagulant drugs. Here, we extract a sulfated polysaccharide from sea hare, that is, Bursatella leachii viscera, by enzymatic digestion. Several analytical approaches including elemental analysis, Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and high-performance liquid chromatography–mass spectrometry analysis show that B. leachii polysaccharides have chemical structures similar to glycosaminoglycans. We explore the anticoagulant activity of the B. leachii extract using the activated partial thromboplastin time and the thrombin time. Our results demonstrate that the extracted sulfated polysaccharide has heparin-like anticoagulant activity, thus showing great promise as an alternative anticoagulant therapy.
  • Visualization of Polymer Retention Mechanisms in Porous Media UsingMicrofluidics

    Sugar, Antonia; Serag, Maged F.; Torrealba, Victor A.; Buttner, Ulrich; Habuchi, Satoshi; Hoteit, Hussein (Society of Petroleum Engineers, 2020-06-04) [Conference Paper]
    Understanding polymer transport through porous media is key to successful field implementations,including well conformance control and EOR processes. Polymer retention is typically assessed indirectlythrough its effect on pressure drops and effluent concentrations. Microfluidic techniques representconvenient tools to observe and quantify polymer retention in porous media. In this paper, we demonstratehow a soft-lithography microfluidics protocol can be used to gain insights into polymer transportmechanisms through rocks. The design of the microfluidic chips honors typical pore-size distributions of oil-bearing conventionalreservoir rocks, with pore-Throats ranging from 2 to 10 um. The fabrication technology enables the designtransfer on a silicon wafer substrate using photolithography. The etched wafer holding the negative patternof the pore-network served as a mold for building the microfluidics chip body out of polydimethylsiloxane(PDMS). The oxygen plasma bonding of the PDMS to a thin glass slide resulted in a sealed microfluidic chip,conceptually referred to as "Reservoir-on-A-Chip". We conduct single-phase polymer flooding experimentson the designed chips to understand how polymer-rock interactions impact polymer transport behavior inrocks. These experiments allow for polymer transport visualization at the molecule-scale owing to the useof polymer tagging and single-molecule tracking techniques. This study presents, for the first time, a direct visualization of polymer retention mechanisms in porousmedia. We identified three mechanisms leading to polymer retention: Adsorption, mechanical entrapment,and hydrodynamic retention. Polymer adsorption on the chip surfaces resulted in flow conductivityreduction in specific pathways and complete blockage in others, inducing alterations in the flowpaths. Thismechanism occurred almost instantaneously during the first minutes of flow then, dramatically diminishedas adsorption was satisfied. In addition to static adsorption, flow-induced adsorption (entrapment) wasalso distinguished from the binding of flowing polymer molecules to the already adsorbed polymer layer.Evidence of polymer desorption was observed, which consents with the presumed reversibility character of polymer retention mechanisms. The narrowest channels along with the reduced area due to adsorption,created favorable conditions for polymer entrapment. Both mechanical and hydrodynamic trapped polymerswere successfully imaged. These phenomena led to polymer clogging of the porous network, which is oneof the major concerns for operational aspects of polymer flooding processes. Better understanding and quantification of polymer retention in porous media can help to make betterdecisions related to field-scale implementations of polymer-based processes in the subsurface. In this study,we used a soft-lithography fabrication technique and single-molecule imaging, to show, for the first time,polymer transport insights at the molecule-and pore-scales. This approach opens a new avenue to improveour understanding of the first principals of polymer retention while flowing through porous media.
  • The Key Factors That Determine the Economically Viable, Horizontal Hydrofractured Gas Wells in Mudrocks

    Haider, Syed; Saputra, Wardana; Patzek, Tadeusz (Energies, MDPI AG, 2020-05-08) [Article]
    We assemble a multiscale physical model of gas production in a mudrock (shale). We then tested our model on 45 horizontal gas wells in the Barnett with 12–15 years on production. When properly used, our model may enable shale companies to gain operational insights into how to complete a particular well in a particular shale. Macrofractures, microfractures, and nanopores form a multiscale system that controls gas flow in mudrocks. Near a horizontal well, hydraulic fracturing creates fractures at many scales and increases permeability of the source rock. We model the physical properties of the fracture network embedded in the Stimulated Reservoir Volume (SRV) with a fractal of dimension D < 2 . This fracture network interacts with the poorly connected nanopores in the organic matrix that are the source of almost all produced gas. In the practically impermeable mudrock, the known volumes of fracturing water and proppant must create an equal volume of fractures at all scales. Therefore, the surface area and the number of macrofractures created after hydrofracturing are constrained by the volume of injected water and proppant. The coupling between the fracture network and the organic matrix controls gas production from a horizontal well. The fracture permeability, k f , and the microscale source term, s, affect this coupling, thus controlling the reservoir pressure decline and mass transfer from the nanopore network to the fractures. Particular values of k f and s are determined by numerically fitting well production data with an optimization algorithm. The relationship between k f and s is somewhat hyperbolic and defines the type of fracture system created after hydrofracturing. The extremes of this relationship create two end-members of the fracture systems. A small value of the ratio k f / s causes faster production decline because of the high microscale source term, s. The effective fracture permeability is lower, but gas flow through the matrix to fractures is efficient, thus nullifying the negative effect of the smaller k f . For the high values of k f / s , production decline is slower. In summary, the fracture network permeability at the macroscale and the microscale source term control production rate of shale wells. The best quality wells have good, but not too good, macroscale connectivity.
  • Nano-characterization of silicon-based multilayers using the technique of STEM-EELS spectrum-imaging

    Anjum, Dalaver H.; Qattan, I. A.; Patole, Shashikant; Diallo, Elhadj; Wei, Nini; Heidbreder, Henry (Materials Today Communications, Elsevier BV, 2020-05-06) [Article]
    Silicon (Si) and its compounds are still actively being used by electronic and solar-energy industries. In this work, we focus on one-stop-instrument (OSI) for the characterization of silicon (Si)-based thin-films namely Si, silicon nitride (SiNx), and silicon oxide (SiO2). The goal of performing the characterization of Si-based compounds with OSI has been achieved by carrying out their nanoscale-characterization (Nano-Characterization) with a modern transmission electron microscope (TEM). The presented results demonstrate that TEM is proven to be a powerful OSI for carrying out the Nano-Characterization of Si-based multilayer stacks. It does that via electron microscopy imaging (EMI), and electron spectroscopic imaging (ESI) routes. The presented results show that while EMI allows imaging the structure and morphology of thin-films at nanoscale, the ESI, by combining imaging and spectroscopy techniques, enables distinguishing the pure Si regions from its oxide and nitride regions. Moreover, for the first time, we show that the ESI is sensitive enough to differentiate the crystalline Si regions from that of amorphous Si ones.
  • A Review of Integrated On-Board EV Battery Chargers: Advanced Topologies, Recent Developments and Optimal Selection of FSCW Slot/Pole Combination

    Metwly, Mohamed Y.; Abdel-Majeed, Mahmoud S.; Abdel-Khalik, Ayman S.; Hamdy, Ragi A.; Hamad, Mostafa S.; Ahmed, Shehab (IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2020-05-06) [Article]
    Integrated on-board battery chargers (OBCs) have been recently introduced as an optimal/elegant solution to increase electric vehicle (EV) market penetration as well as minimize overall EV cost. Unlike conventional off-board and on-board battery chargers, integrated OBCs exploit the existing propulsion equipment for battery charging without extra bulky components and/or dedicated infrastructure. OBCs are broadly categorized into three-phase and single-phase types with unidirectional or bidirectional power flow. This paper starts with surveying the main topologies introduced in the recent literature employing either induction or permanent magnet motors to realize fully integrated slow (single-phase) and fast (three-phase) on-board EV battery charging systems, with emphasis on topologies that entail no or minimum hardware reconfiguration. Although, permanent magnet (PM) motors with conventional double-layer distributed winding layouts have been deployed in most commercial EV motors, the non-overlapped fractional slot concentrated winding (FSCW) has been the prevailing choice in the most recent permanent magnet motor designs due to its outstanding operational merits. Hence, a thorough investigation of the impact different FSCW stator winding designs have on machine performance under the charging process is presented in this paper. To this end, the induced magnet losses, which represent a challenging demerit of the FSCW, have been used to compare different topologies under both propulsion and charging operation modes. Based on the introduced comparative study, the optimal slot/pole combinations that correspond to the best compromise under both operational modes have been highlighted.
  • An advanced discrete fracture model for variably saturated flow in fractured porous media

    Koohbor, Behshad; Fahs, Marwan; Hoteit, Hussein; Doummar, Joanna; Younes, Anis; Belfort, Benjamin (Advances in Water Resources, Elsevier BV, 2020-05-06) [Article]
    Accurate modeling of variably saturated flow (VSF) in fractured porous media with the discrete fracture-matrix (DFM) model is a computationally challenging problem. The applicability of DFM model to VSF in real field studies at large space and time scales is often limited, not only because it requires detailed fracture characterization, but also as it involves excessive computational efforts. We develop an efficient numerical scheme to solve the Richards equation in discretely fractured porous media. This scheme combines the mixed hybrid finite element method for space discretization with the method of lines for time integration. The fractures are modeled as lower-dimensional interfaces (1D), within the 2D porous matrix. We develop a new mass-lumping (ML) technique for the fractures to eliminate unphysical oscillations and convergence issues in the solution, which significantly improves efficiency, enabling larger field applications. The proposed new scheme is validated against a commercial simulator for problems involving water table recharge at the laboratory scale. The computational efficiency of the developed scheme is examined on a challenging problem for water infiltration in fractured dry soil, and compared with standard numerical techniques. We show that the ML technique is crucial to improve robustness and efficiency, which outperforms the commonly used methods that we tested. The applicability of our method is then demonstrated in a study concerning the effect of climate change on groundwater resources in a karst aquifer/spring system in El Assal, Lebanon. Simulations, including recharge predictions under climate change scenarios, are carried out for about 80 years, up to 2099. This study demonstrates the applicability of our proposed scheme to deal with real field cases involving large time and space scales with high variable recharge. Our results indicate that the water-table level is sensitive to the presence of fractures, where neglecting fractures leads to an overestimation of the available groundwater amount. The proposed numerical approach is generic for DFM model and can be extended to different 2D and 3D finite-element frameworks.
  • Physical Scaling of Oil Production Rates and Ultimate Recovery from All Horizontal Wells in the Bakken Shale

    Saputra, Wardana; Kirati, Wissem; Patzek, Tadeusz (Energies, MDPI AG, 2020-04-21) [Article]
    A recent study by the Wall Street Journal reveals that the hydrofractured horizontal wells in shales have been producing less than the industrial forecasts with the empirical hyperbolic decline curve analysis (DCA). As an alternative to DCA, we introduce a simple, fast and accurate method of estimating ultimate recovery in oil shales. We adopt a physics-based scaling approach to analyze oil rates and ultimate recovery from 14,888 active horizontal oil wells in the Bakken shale. To predict the Estimated Ultimate Recovery (EUR), we collapse production records from individual horizontal shale oil wells onto two segments of a master curve: (1) We find that cumulative oil production from 4845 wells is still growing linearly with the square root of time; and (2) 6401 wells are already in exponential decline after approximately seven years on production. In addition, 2363 wells have discontinuous production records, because of refracturing or changes in downhole flowing pressure, and are matched with a linear combination of scaling curves superposed in time. The remaining 1279 new wells with less than 12 months on production have too few production records to allow for robust matches. These wells are scaled with the slopes of other comparable wells in the square-root-of-time flow regime. In the end, we predict that total ultimate recovery from all existing horizontal wells in Bakken will be some 4.5 billion barrels of oil. We also find that wells completed in the Middle Bakken formation, in general, produce more oil than those completed in the Upper Three Forks formation. The newly completed longer wells with larger hydrofractures have higher initial production rates, but they decline faster and have EURs similar to the cheaper old wells. There is little correlation among EUR, lateral length, and the number and size of hydrofractures. Therefore, technology may not help much in boosting production of new wells completed in the poor immature areas along the edges of the Williston Basin. Operators and policymakers may use our findings to optimize the possible futures of the Bakken shale and other plays. More importantly, the petroleum industry may adopt our physics-based method as an alternative to the overly optimistic hyperbolic DCA that yields an ‘illusory picture’ of shale oil resources.
  • Quantification of Photophysical Processes in All-Polymer Bulk Heterojunction Solar Cells

    Albalawi, Ahmed; Kan, Zhipeng; Gorenflot, Julien; Guarracino, Paola; Chaturvedi, Neha; Privitera, Alberto; Liu, Shengjian; Gao, Yajun; Franco, Lorenzo; Beaujuge, Pierre; Laquai, Frédéric (Solar RRL, Wiley, 2020-04-14) [Article]
    All-polymer solar cells lag behind the state-of-the-art in small molecule nonfullerene acceptor (NFA) bulk heterojunction (BHJ) organic solar cells (OSCs) for reasons still unclear. Herein, the efficiency-limiting processes in all-polymer solar cells are investigated using blends of the common donor polymer PBDT-TS1 with different acceptor polymers, namely P2TPD[2F]T and P2TPDBT[2F]T. Combining data from steady-state optical spectroscopy and time-resolved photoluminescence, transient absorption, and time-delayed collection field experiments, provides not only a concise but also quantitative assessment of the losses due to limited photon absorption, geminate and nongeminate charge carrier recombination, field-dependent charge generation, and inefficient carrier extraction. Although both systems exhibit a similar charge separation efficiency in the absence of external bias, charge separation is significantly enhanced in P2TPDBT[2F]T-based blends when biased. Kinetic parameters obtained via pulsed laser spectroscopy are used to reproduce the experimentally measured device current–voltage (J–V) characteristics and indicate that low fill factors originate either from nongeminate recombination competing with charge extraction, or from a pronounced field dependence of charge generation, depending on the acceptor polymer. The methodology presented here is generic and can be used to quantify the loss processes in BHJ OSCs including both all-polymer and small molecule NFA systems.
  • IoT-Based Supervisory Control of an Asymmetrical Nine-Phase Integrated on-Board EV Battery Charger

    Metwly, Mohamed Y.; Abdel-Majeed, Mahmoud S.; Abdel-Khalik, Ayman S.; Torki, Marwan; Hamdy, Ragi A.; Hamad, Mostafa S.; Ahmed, Shehab (IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2020-04-01) [Article]
    Electric vehicles (EVs) play a major role in the evolution towards sustainable transportation. The integration of information and communication technology (ICT) into the electric vehicle (EV) charging process has witnessed rapid progress. Wireless communication between EVs has become commercially viable, supporting vehicle-to-sensor, vehicle-to-vehicle, and vehicle-to-internet regimes. However, EVs still have limited market penetration due to charging process constraints such as charging time and the availability of charging points. This paper considers an asymmetrical nine-phase smart integrated on-board charging (OBC) system with a reduced cost, size and weight. All the propulsion components are utilized in the charging process. Both zero machine average torque production and unity power factor operation at the grid side can simultaneously be obtained during the charging process. Additionally, no hardware reconfiguration is required to allow the transition between propulsion and charging modes for this system topology. Furthermore, the proposed integrated on-board charger is completely monitored, and the charging rate is controlled through a smartphone application via internet of things (IoT) technology, thus optimizing the user experience. A 1.5 kW prototype is implemented to validate the proposed system by rewinding a three-phase induction motor (IM).
  • Soil Response to Repetitive Changes in Pore-Water Pressure under Deviatoric Loading

    Park, Junghee; Santamarina, Carlos (Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers (ASCE), 2020-03-10) [Article]
  • Estimation of Effective Permeability, Fracture Spacing, Drainage Area, and Incremental Production from Field Data in Gas Shales with Nonnegligible Sorption

    Eftekhari, B.; Marder, M.; Patzek, Tadeusz (SPE Reservoir Evaluation & Engineering, Society of Petroleum Engineers (SPE), 2020-03-04) [Article]
    In a previous work, we introduced a three-parameter scaling solution that models the long-term recovery of dry gas from a hydrofractured horizontal well far from other wells and the boundaries of a shale reservoir with negligible sorption. Here, we extend this theory to account for the contribution of sorbed gas and apply the extended theory to the production histories of 8,942 dry-gas wells in the Marcellus Shale. Our approach is to integrate unstructured big data and physics-based modeling. We consider three adsorption cases that correspond to the minimum, median, and maximum of a set of measured Langmuir isotherms. We obtain data-driven, independent estimates of unstimulated shale permeability, spacing between hydrofractures, well-drainage area, optimal spacing between infill wells, and incremental gas recovery over a typical well life. All these estimates decrease to varying extents with increasing sorption. We find that the average well with median adsorption has a permeability of 250 nd, fracture spacing of 16 m, 30-year drainage length of 79 m, and a 30-year incremental recovery of 67%

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