Modeling of Before Closure Zero Slope Pressure Derivative in a Diagnostic Fracture Injection Test DFIT

Recent diagnostic fracture injection test (DFIT) data presented on a Bourdet log-log diagnostic plot showed derivative slope of 0 in the before closure (BC) portion of the DFIT response. Some works qualitatively describe it as radial flow. This behavior has not been quantitatively analyzed, modeled and matched. The present work disagrees with the hypothesis of radial flow and successfully matches the relatively flat trend in the Bourdet derivative with a model dominated by friction dissipation coupled with tip extension. The flat trend in Bourdet derivative occurs shortly after shut-in during the before closure period. Because a flat derivative trend suggests diffusive radial flow, our first approach was to consider the possibility that an open crack at a layer interface stopped the fracture propagation and caused the apparent radial flow behavior observed in falloff data. However, a model that coupled pressure falloff from diffusive flow into a layer interface crack with pressure falloff from closure of a fracture that propagated up to the layer interface failed to reproduce the observed response. Subsequently, we discovered that existing models could match the data without considering the layer interface crack. We found that data processing is very important to what is observed in derivative trends and can mislead the behavior diagnosis. We succeeded to match one field DFIT case showing an obvious early flat trend. The presence and dominance of geomechanics, coupled with diffusive flow, disqualify the description of the flat trend in Bourdet derivative as radial flow. Instead, flow friction coupled with tip extension can completely match the observed behavior. Based on our model, cases with a long flat trend have large magnitude near-wellbore tortuosity friction loss and relatively long tip extension distance. Further, we match the near wellbore tortuosity behavior with rate raised to a power lower than the usually assumed 0.5. The significance of these analyses relates to two key factors. First, large magnitude near wellbore tortuosity friction loss increases the pressure required for fracture propagation during pumping. Second, tip extension is a way to dissipate high pumping pressure when very low formation permeability impedes leakoff. Matching transient behavior subject to the presence of both of these factors requires lowering the near-wellbore tortuosity exponent.

Construction of barrier heterostructures based on carbon and organometallic compounds

This paper presents the results of using hybrid-organic zinc complex C24H24N6O3Zn as a component for creating fullerene C60-based heterostructures. The synthesis technique of the complex compound, the microscopy of the film surfaces obtained, their optical and luminescence properties are described in the paper. The introduction of zinc complex to fullerene shows that there occurs a potential barrier at the active layer interface. The obtained thin-film structures have rectifying light volt-ampere characteristics.

Predicting Solvation Thermodynamics in Water and Ionic Liquids using the Multi-Scale Solvation Layer Interface Condition (SLIC)

We highlight the most recent developments of the solvation-layer interface condition (SLIC) continuum dielectric model in predicting solvation thermodynamics of neutral small molecules in water and multiple ionic liquids. We demonstrate that a simple temperature-dependent solvent-accessible-surface-area (SASA) correlation and a cavity-dispersion-combinatorial (CDC) theory, combined with the SLIC electrostatics model, provide highly accurate predictions of Gibbs solvation energies, solvation entropies, and solvation heat capacities. The SLIC/SASA model parameters are temperature dependent, whereas the SLIC/CDC parameters are constant. To address the lack of experimental data pertaining to the accuracy of the models, we conducted an extensive literature search and data compilation to obtain credible experimental solvation data. This yielded 159 and 123 data points for hydration entropies and heat capacities of neutral small molecules, respectively. Compared to experimental data, the SLIC/SASA and SLIC/CDC models, respectively, achieve an RMS error 1.39 (1.24) and 1.15 (1.76) kcal/mol for hydration free energy (hydration entropy) predictions. Solvation heat capacities are predicted with RMS errors 24.42 and 46.17 cal/mol/K. Most remarkably, the SLIC/CDC predictions of solvation entropies and heat capacities are made without apriori knowledge of experimental solvation entropies. In addition, the SLIC/SASA predictions of Gibbs solvation energies (solvation entropies) of 12 amino acid side-chain analogs in seven (three) ionic liquids are compared to the available explicit-solvent simulation data from Paluch et al.~\cite{Paluch12} and Latif~\cite{Latif14} et al.