bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unstructured CVD-MPFA Reduced-Dimensional DFM Models for Two-Phase Flow, Coupled with Higher Resolution Hybrid Upwind Methods
Authors: Xie Yawei , Edwards Michael G. 
Published: March 2019

Abstract
A novel discrete fracture model (DFM) approximation is presented and coupled with the control-volume distributed multi-point flux approximation (CVD-MPFA) formulation. The reduced-dimensional discrete discontinuous pressure model for intersecting fractures is extended to two-phase flow, including gravity and discontinuous capillary pressure. A novel higher resolution hybrid upwind method provides improved flow resolution on unstructured grids.
Novel discontinuous fracture models together with appropriate interface conditions, essential for application to cases involving continuous and discontinuous capillary pressure, and for fractures with permeability barrier effects are presented. The CVD-MPFA based discontinuous DFM models are coupled with higher resolution methods on unstructured grids, including an extended higher resolution hybrid upwind method for gravity driven flow and a novel higher resolution capillary flux approximation. A special DFM approximation is presented for fracture intersection cells located in flow fields where viscous and gravity forces interact.
Performance comparisons are presented for tracer and two-phase flow and fracture problems involving discontinuous capillary pressure and gravity on unstructured meshes. The results demonstrate the importance of the discontinuous DFM model to resolve flow problems including oil trapping in fractures. In addition comparison between the standard lower order method and the higher resolution hybrid upwind scheme shows that the higher resolution method yields significantly improved flow resolution in gravity driven flow fields.
A novel DFM approximation is presented and coupled with the CVD-MPFA formulation on unstructured grids. The method includes a discontinuous discrete fracture model with appropriate interface conditions for application to discontinuous capillary pressure fields, and a new method for treatment of intersecting fractures is also introduced for viscous-gravity driven flow. The method is also coupled with a higher resolution hybrid upwind scheme which yields improved flow resolution.
Thermodaynamic Stability Analysis for Multi-Component Mixtures with Capillary Pressure
Authors: Neshat Sajjad Sadeghi , Okuno Ryosuke , Pope Gary Arnold 
Published: March 2019

Abstract
Despite the great interest and importance of modeling hydrocarbon production from tight oil reservoirs, the thermodynamic stability of multicomponent mixtures with capillary pressure has not been studied sufficiently. This paper introduces a practical algorithm for phase stability analysis of multi-component mixtures with capillary pressure. The capillary pressure is determined from a realistic saturation-dependent function which is representative of pore size distributions as well as other petrophysical properties such as wettability and water saturation in tight oil reservoirs. The new stability procedure is coupled with calculations of the phase behavior. The significance and robustness of the new method is shown in several examples with realistic tight oil and gas-condensate mixtures.
A Geomechanically-Constrained Dynamic Fractal Wormhole Growth Model for Simulating Cold Heavy Oil Production with Sand
Authors: Yu Haisheng , Leung Juliana Y. 
Published: March 2019

Abstract
Cold heavy oil production with sand (CHOPS) is a non-thermal primary process that is widely adopted in many weakly consolidated heavy oil deposits around the world. However, only 5 to 15% of the initial oil in place is typically recovered. Several solvent-assisted schemes are proposed as follow-up strategies to increase the recovery factor in post-CHOPS operations. The development of complex, heterogeneous, high-permeability channels or wormholes during CHOPS renders the analysis and scalability of these processes challenging. One of the key issues is how to properly estimate the dynamic growth of wormholes during CHOPS. Existing growth models generally offer a simplified representation of the wormhole network, which, in many cases, is denoted as an extended wellbore. Despite it is commonly acknowledged that wormhole growth due to sand failure is likely to follow fractal statistics, there are no established workflows to incorporate geomechanical constraints into the construction of these fractal wormhole patterns.
A novel dynamic wormhole growth model is developed to generate a set of realistic fractal wormhole networks during the CHOPS operations. It offers an improvement to the Diffusion Limited Aggregation (DLA) algorithm with a sand-arch-stability criterion. The outcome is a fractal pattern that mimics a realistic wormhole growth path, with sand failure and fluidization being controlled by geomechanical constraints. The fractal pattern is updated dynamically by coupling compositional flow simulation on a locally-refined grid and a stability criterion for the sand arch: the wormhole would continue expanding following the fractal pattern, provided that the pressure gradient at the tip exceeds the limit corresponding to a sand-arch-stability criterion. Important transport mechanisms including foamy oil (non-equilibrium dissolution of gas) and sand failure are integrated.
Public field data for several CHOPS fields in Canada is used to examine the results of the dynamic wormhole growth model and flow simulations. For example, sand production history is used to estimate a practical range for the critical pressure gradient representative of the sand-arch-stability criterion. The oil and sand production histories show good agreement with the modeling results.
In many CHOPS or post-CHOPS modeling studies, constant wormhole intensity is commonly assigned uniformly throughout the entire domain; as a result, the ensuing models are unlikely to capture the complex heterogeneous distribution of wormholes encountered in realistic reservoir settings. This work, however, proposes a novel model to integrate a set of statistical fractal patterns with realistic geomechanical constraints. The entire workflow has been readily integrated with commercial reservoir simulators, enabling it to be incorporated in practical field-scale operations design.
A Numerical Method for Hydraulic Fracture Propagation Using Embedded Meshes
Authors: Ren Guotong , Younis Rami M. 
Published: March 2019

Abstract
Fracture propagation (FP) occurs in extensive applications including hydraulic fracturing, underground disposal of liquid waste, CO2 sequestration etc. It is crucial to develop a simulator that is able to reflect physics behind FP and capture the FP path. This work is an extension of the previous developed model (Ren et al. (2018), Ren & Younis (2018)) to the simulation of FP. One of the remarkable benefits using the coupled XFEM-EDFM scheme allows FP free of the remeshing. In this work, the onset of FP is controlled by a single parameter, the equivalent stress intensity factor (SIF). A domain integral method, J integral is applied to extract the SIF information. A time marching scheme is performed to ensure the SIF criterion satisfied everytime fracture propagates. The developed simulator is verified by the analytical solutions and shows the capability of FP simulation in poroelastic materials.
Modelling of Electromagnetic Heating Process and its Applications in Oil Sands Reservoirs
Authors: Ji Dongqi , Harding Thomas , Chen Zhangxin , Dong Mingzhe , Liu Hui 
Published: March 2019

Abstract
For thermal heavy oil recovery, conventional steam injection processes are generally limited to reservoirs of relatively shallow depth, high permeability, thick pay zone and homogeneity. An alternative approach of applying Electromagnetic (EM) energy may be used to generate heat in reservoirs that are not suitable for steam injection or to improve the economics of the heavy oil recovery compared with steam injection. EM in-situ heating of oil reservoirs, in the form of EM energy absorption by dielectric materials, leads to an increase in temperature, a reduction in oil viscosity and an improvement in oil mobility. Recent studies have shown that EM heating is capable of reducing carbon emissions and water usage. However, the existing EM field simulators are limited to modeling of homogeneous media with respect to dielectric properties, which affects EM wave propagation and in-situ heat generation. For oil sands recovery where reservoir heating by EM energy is promising, it is desirable to simulate reservoirs in inhomogeneous formations, in which dielectric properties vary according to specific location. In this work, important background information regarding the EM wave propagation in inhomogeneous media is provided. A Helmholtz equation for the magnetic field by deformation of Maxwell's equations is presented that makes it feasible to find EM field solutions for such inhomogeneous media. Solution of only the magnetic field makes this work execution faster than the classical methods in which both magnetic and electric fields need to be calculated. By solving the equations of EM wave propagation and fluid flow in oil sands reservoirs simultaneously, this work provides a fully-implicit modelling method for the EM heating process. The feasibility of EM heating in oil sands is examined in two case studies: a) a horizontal well containing an antenna within and b) a horizontal well-pair with an antenna located in the upper well.
Model-Order Reduction of Coupled Flow and Geomechanics in Ultra-Low Permeability ULP Reservoirs
Authors: Florez Horacio , Gildin Eduardo 
Published: March 2019

Abstract
This work focuses on the development of accurate and fast simulation models for Ultra-Low Permeability (ULP) reservoirs, i.e., tight-sands and shales. ULP plays are the main unconventional resources that concentrate the bulk of production activity in the US. ULP challenge conventional simulators because they require multiphysics couplings, e.g., flow and geomechanics couplings, which poses a severe burden regarding computational efforts. We, thus address these challenges by developing accurate reduced-order models for coupled flow and geomechanics.
We rely on projection-based Model-Order Reduction (MOR) and hyper-reduction (POD-DEIM) techniques to reduce the ULPs computational cost. More specifically, we perform the standard offline training stage on displacements as primary variables to create local basis using Proper Orthogonal Decomposition (POD). During the online phase, we project the residual and Jacobian that arise from both poroelasticity and rate-independent poroplasticity into the given basis to reduce one-way coupled flow and geomechanics computations. We approximate the tensors, for the energy equation, to minimize the serial-time. We consider the role of the heterogeneity and material models such as Von Mises and investigate the benefits of hyper-reduction (POD-DEIM) on the non-linear functions.
Preliminary results, that focus on linear and nonlinear thermo-poroelasticity, show that our MOR algorithm provides substantial single and double digits speedups, up to 50X if we combine with multi-threading assembling and perform MOR on both physics. We highlight the remarkable MOR compression ratio above 99.9% for mechanics. The approach is particularly useful to speed up solving the sparse system for the inner iteration in convolution like problems which produces significant time savings compared to the serial full-order model (FOM). The latter is also true for problems that exhibit long serial times, for instance, while assembling the Jacobian and Residual for both physics and post-processing to compute stresses, if the serial-time per iteration is shorter that solving the sparse system of equations. These MOR results are promising in the sense that for most coupled flow and mechanics problems, the above condition holds. We formally compare FOM and reduced-order model (ROM) and provide time data to demonstrate the speedup of the procedure. Examples cover elasticity and rate-independent plasticity one-way coupled with the two-phase flow and the energy equation. We employ continuous Galerkin finite elements for the mechanics.
A Three-Dimensional Symmetric Positive Definite Control-Volume Distributed Multi-Point Flux Approximation for Flow Computation on Tetrahedral Grids
Authors: Ahmed Raheel , Edwards Michael G. 
Published: March 2019

Abstract
A three-dimensional symmetric positive definite (SPD) cell-centred control-volume distributed multi-point flux approximation (CVD-MPFA) is presented for porous media flow simulation on tetrahedral grids. The scheme depends on a single degree of freedom per control-volume and is derived in physical space where the continuous fluxes are resolved directly along the face normals of the tetrahedra. We believe this is the first and possibly only general three-dimensional full-tensor finite-volume scheme that is flux- continuous and SPD in physical space, while depending on a single degree of freedom per control-volume. The equivalent general two-dimensional CVD-MPFA scheme that is SPD in physical space is presented in (Friis et al., 2008).
Optimization Based Well Management for Coupling Giant Reservoir Models
Authors: Middya Usuf , Crumpton Paul , Tariq Qasim 
Published: March 2019

Abstract
The objective is to couple tens of full-field giant reservoirs and apply optimized-based well management system to the all the flowing wells to manage a high level production plateau and injection system.
In this work each individual reservoir simulation model is a giant field, with a large historical (70y) and prediction (200y) time periods, 10s of millions of cells and thousands of wells, many injection and production constraints and drilling targets. Each of these giant fields requires a parallel supercomputer to run each individual model in a reasonable time. To couple many of these models they are all executed as one combined parallel job, which is subdivided in groups of processes dedicated for individual reservoirs. A layered communication hierarchy is used, which facilitates coordination and synchronization of the individual reservoirs and the optimization and allocation of the production and injection targets of every well and group of wells in the coupled system. Great effort was placed on making the user workflow very simple; having established a history and prediction field-scale model, the coupling can be achieved by a straightforward manipulation of the individual field-scale models, and high-level constraints and targets can be added to the coupled system. To alleviate some run time/resource issues, the level of detail required for each model was chosen by activating a coarsening facility within the reservoir simulator. This reduced the simulation resources needed for individual fields, but exacerbated the potential bottleneck of the optimization engine, as all well and group constraints were preserved in the coupled model.
To stress test this system, up to 15 giant models were coupled, with over 15 thousand wells managed by an optimized based well management system. The single node responsible for allocation of all the wells was not found to be a bottleneck in the system.
The journey from the detailed full-field giant model to a coupled super-giant coupled model has many challenges. Here, these are alleviated by tight and efficient integration of the coupling optimized-based well management system and the massively parallel reservoir simulator. This paper demonstrates a new industry high water mark for the coupling of reservoir models.
Quasi-K-Orthogonal Grid Generation
Authors: Manzoor Shahid , Edwards Michael G. , Dogru Ali H. 
Published: March 2019

Abstract
Quasi K-orthogonal grid generation is presented, to improve grid quality and method stability with respect to flux approximation in the presence of strongly anisotropic full-tensor permeability fields.K-orthogonal grid generation is only possible for low anisotropy ratios. Quasi K-orthogonal grid generation involves satisfying the K-orthogonal condition approximately, resulting in grids that place less demand on an approximation with respect to stability conditions, and therefore improve grid quality with respect to flux approximation in the presence of anisotropic permeability fields. The method employed enables Delaunay grid generation principles to be employed in a locally transformed system according to local permeability tensor variation. The resulting method has great flexibility for handling complex geometries and can handle jumps in permeability tensor principal axes orientation and jumps in coefficients and details will be presented. Results are presented that demonstrate the benefit of a quasi K-orthogonal grid. Highly challenging cases involving strong full-tensor permeability fields where control-volume distributed multi-point flux approximation (CVD-MPFA) schemes exceed their stability limits and yield solutions with spurious oscillations when using conventional grids, are solved using the new grid generation method. CVD-MPFA schemes are still required as the grids are only approximately K-orthogonal in such cases, however the schemes retain a discrete maximum principle on the new quasi-K-orthogonal grids and yield well resolved solutions that are free of spurious oscillations. While the two-point flux approximation (TPFA) requires strict K-orthogonality, results using both CVD-MPFA and TPFA will be presented. New Quasi K-orthogonal grid generation methods are presented that satisfy the K-orthogonal condition approximately, resulting in practical grids that restore a discrete maximum principle (stability) for the CVD-MPFA schemes when applied to cases involving general full-tensor permeability fields. Results are presented for a variety of test cases that confirm the validity of the grids.
Microbiota and Chemical Compounds in Fermented Pinelliae Rhizoma (Banxiaqu) from Different Areas in the Sichuan Province, China
Authors: SHU BO , YING JING , WANG TAO , XIA MENGQIAN , ZHAO WENYU , YOU LING 
Published: March 2019

Abstract
This study focused on the microbiota and chemical compounds of the fermented Pinelliae Rhizoma produced in Longchang (LC), Zizhong (ZZ) and Xindu (XD), in Sichuan Province (China). High-throughput sequencing was used to analyze the microbiota. GC-MS and LC-MS were used to detect the compounds produced during the three different Pinelliae Rhizoma fermentation processes. The bacteria and fungi of the three fermented Pinelliae Rhizoma differed substantially, with the bacterial content mainly composed of the Bacillus genus, while the common fungi were only included in four OTUs, which belong to three species of Eurotiomycetes and Aspergillus cibarius. 51 volatile compounds were detected; they varied between LC, XD, and ZZ fermented Pinelliae Rhizoma. C10 and C15 terpenes were most frequently detected, and only curcumene and β-bisabolene were detected in the three fermented Pinelliae Rhizoma. 65 non-volatile compounds were detected by LC-MS, most were of C16, C18, C20, C21 and C22 structures. Cluster analysis showed more similarity between LC and XD fermented Pinelliae Rhizoma with regards to volatile compound content, but more similarity between the XD and ZZ fermented Pinelliae Rhizoma for non-volatiles. Moreover, no correlation between geographical distance and microflora or compounds of fermented Pinelliae Rhizoma was observed. These results showed that hundreds of compounds are produced by the natural mixed fermentation of Pinelliae Rhizoma, and may mostly relate to the microorganisms of five species.
Evaluation of future runoff variations in the north–south transect of eastern China: effects of CMIP5 models outputs uncertainty
Authors: Sun Guodong , Peng Fei 
Published: March 2019

AbstractRunoff is an important water flux that is difficult to simulate and predict due to lacking observation. Meteorological forcing data are a key factor in causing the uncertainty of predicted runoff. In this study, climate projections from ten general circulation models of the Coupled Model Intercomparison Project 5 (CMIP5) with high resolution under the Representative Concentration Pathway (RCP) 4.5 scenario are employed to estimate the future uncertainty range of predicted runoff in the North–South Transect of Eastern China (NSTEC) from 2011 to 2100. It is found that the range of future annual runoff is from 268.9 mm (Meteorological Research Institute coupled GCM, MRI-CGCM3) to 544.2 mm (Model for Interdisciplinary Research on Climate, MIROC5). The precipitation and the annual actual evapotranspiration are two key factors that affect the variation of runoff. The low annual runoff for the MRI-CGCM3 model may be caused by low precipitation and high annual actual evapotranspiration (466.9 mm). However, the high annual runoff for the MIROC5 may be caused by the high precipitation, although there is high annual actual evapotranspiration (544.2 mm). The above results imply that the forcing data and the model physics are important factors in the numerical simulation and prediction about runoff.
Emergence of Heteroresistance Mycobacterium Tuberculosis in Saudi Arabia
Authors: Abakur Eltayib H. Ahmed , Alnour Tarig M.S. , Abuduhier Faisel , Albalawi Fahad M.A. , Alfifi Khalid A.S. 
Published: March 2019

Purpose:Heteroresistant Mycobacterium tuberculosis (MTB) is defined as a group of drug-susceptible and resistant bacteria in a single clinical specimen from tuberculosis (TB) patients. Heteroresistance of MTB is considered a preliminary stage to full resistance. The present study aimed to determine the heteroresistance in Mycobacterium tuberculosis in Tabuk province, in the north of the Kingdom of Saudi Arabia.Method:GenoType MTBDRplus assay was used to determine mutations associated with isoniazid and rifampicin resistance.Results:A total number of 46 confirmed M. tuberculosis positive sputum samples were scanned for heteroresistance. The present study revealed 3 (6.5%) heteroresistant mutations to either rpoB gene alone, 2 (4.4%) to rpoB and 1 (2.2%) to inhA genes.Conclusion:The detection of heteroresistant mutations could guide the initiation of an appropriate regimen of treatment.
Subacromial Balloon Interpositional Arthroplasty for the Management of Irreparable Rotator Cuff Tears: Five-year Results
Authors: Bakti Nik , Bhat Mahendar , Gulihar Abhinav , Prasad Vellala , Singh Bijayendra 
Published: March 2019

Background:
Management of massive irreparable rotator cuff tears can be a source of significant dilemma for the treating surgeon. This is especially true when dealing with patients with poor physiological reserves where options of tendon transfer, superior capsular repair or arthroplasty might be unsuitable. We report the five-year outcomes of 26 patients who underwent balloon interpositional arthoplasty for the management of massive irreparable rotator cuff tears.

Methods:
Fifty-four consecutive patients underwent balloon interpositional arthroplasty in our institution. Of these, 26 patients completed at least two postoperative functional outcome measures over a five-year period, which included the Visual Analogue Score (VAS), Oxford Shoulder Score (OSS) and the SF12 score. Outcome scores were obtained prospectively.

Results:
The average age at implantation was 67 years old. Our result shows statistically significant improvement in pain up to five years post-implantation of the device (p = 0.012). Function measured by the OSS and SF12 (PCS) score showed improvement up to two years post-implantation (p = 0.006). Three of the 54 patients in our cohort went on to have arthroplasty surgery for their rotator cuff tears. None of the patients in our cohort suffered from any adverse reactions following implantation.

Discussion/Conclusion:
Results from our study identify the spacer device as an option in the management of irreparable rotator cuff tears with statistical improvement in pain and function. It may also delay the need for arthoplasty surgery.