bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accurate Inflow Profile Prediction of Horizontal Wells through Coupling of a Reservoir and a Wellbore Simulator
Authors: Kabir Akim , Sanchez Gerardo 
Published: February 2009

Abstract
Predicting accurate inflow pressure and flow profile of horizontal laterals is one of the biggest impediments in achieving their optimum performance. Reservoir simulators are capable of simulating flow in the reservoir up to the fluid entry points in the well reasonably well. Wellbore simulators can simulate flow from the fluid entry points up to the surface delivery system. The integrated system can be simulated numerical reservoir simulators adequately assuming a single point fluid entry to the well. However, accurate foot by foot prediction of pressure and flow profile at the reservoir/well interface of long horizontal wells is a challenge. Some simulators attempt to simulate this detailed inflow profile using some simplified approach. A few semi-analytical modeling approach is also available in the literature. They use average parameter values in their calculation. These simplifying assumptions result in less than accurate inflow profile prediction to the extent that they are inadequate for some design optimization studies.
In this paper we describe coupling of a 3-D numerical reservoir simulator with a wellbore simulator in a simple manner which is capable of predicting a detailed inflow profile along long horizontal wells. Flow and pressure along the laterals are iterated between the simulators at each point of interface until they converge. This convergence is repeated at desired time intervals ultimately resulting in a fully converged integrated reservoir-wellbore simulation with the detailed and accurate inflow profile. The algorithm was initially tested manually and later automated. Results of the work is presented along with an application (designing Inflow Control Devices) aimed at achieving uniform flow profile along horizontal laterals. This is a powerful capability which will enable us optimize horizontal completions to the extent which was not possible before.
Closed Loop Reservoir Management Using the Ensemble Kalman Filter and Sequential Quadratic Programming
Authors: Lorentzen Rolf J. , Shafieirad Ali , Naevdal Geir 
Published: February 2009

Abstract
As part of the SPE-ATW"Closed-loop reservoir management" held in Bruges, June 2008, a synthetic data set was made available to the participants. This paper describes our workflow and results for closed-loop reservoir management using this synthetic model. The closed-loop exercise is divided into two cycles, each consisting of data assimilation and production optimization. The data assimilation is done using the ensemble Kalman filter, and the optimization is done using sequential quadratic programming after a reformulation of the problem to reduce the number of variables.
The methodology performs well on the case considered here, and high NPV values are obtained. In particular we have proposed a new strategy for production optimization that makes a large scale optimization problem feasible through a proper reduction of control variables based on analysis of the properties of the field and application of a state of the art optimization method.
An EOS-Based Compositional Thermal Reservoir Simulator
Authors: Varavei Abdoljalil , Sepehrnoori Kamy 
Published: February 2009

Abstract
In the past thirty years, the development of compositional reservoir simulators using various equations of state (EOS) has been addressed in the SPE literature. However, the development of compositional thermal simulators in conjunction with EOS formulation has been ignored, in particular. Therefore, a fully implicit, parallel, compositional EOS-based simulator has been developed. In this model, an equation of state is used for equilibrium calculations among all phases (oil, gas, and aqueous). Also, the physical properties are calculated based on an EOS, hence obviating the need for using steam tables for calculation of water/steam properties. The governing equations for the model comprise fugacity equations between the three phases, material balance, pore volume constraint and energy equations. The governing partial differential equations are solved using finite difference or finite volume approximations. In the steam injection process, the solubility of oil in water-rich phase and the solubility of water in oil phase can be high. This model takes into account the solubility of water in oil phase and the solubility of hydrocarbon components in water-rich phase, using three-phase flash calculations.
This simulator can be used in various thermal flooding processes (i.e. hot water or steam injections). Since the simulator was implemented for parallel computers, it is capable of solving large-scale thermal flooding problems. The simulator is successfully validated using analytical solutions. Also, simulations are carried out to compare this model with commercial simulators.
The use of an EOS for calculation of various properties for each phase automatically satisfies the thermodynamic consistency requirements. On the other hand, using the K-value approach, which is not thermodynamically robust, may lead to results that are thermodynamically inconsistent. This simulator accurately tracks all components and mass transfer between phases using an EOS; hence, it will produce thermodynamically consistent results and project accurate prediction of thermal recovery processes.
Dynamic Upscaling of Multiphase Flow in Porous Media via Adaptive Reconstruction of Fine Scale Variables
Authors: Lee S. H. , Wang X. , Zhou H. , Tchelepi H. A. 
Published: February 2009

Abstract
We propose an upscaling method that is based on dynamic simulation of a given model in which the accuracy of the upscaled model is continuously monitored via indirect error-measures. If the indirect error measures are bigger than a specified tolerance, the upscaled model is dynamically updated with approximate fine scale information that is reconstructed by a multi-scale finite volume method (Jenny et al., JCP 217: 627–641, 2006). Upscaling of multi-phase flow entails a detailed flow information in the underlying fine scale. We apply adaptive prolongation and restriction operators for flow and transport equations in constructing an approximate fine scale solution. This new method eliminates inaccuracy associated with the traditional upscaling method which relies on prescribed inaccurate boundary conditions in computing upscaled variables. The new upscaling algorithm is validated for two-phase, incompressible flow in two dimensional porous media with heterogeneous permeabilities. It is demonstrated that the dynamically upscaled model achieves high numerical efficiency than the fine-scale models and also provides an excellent agreement with the reference solution computed from fine-scale simulation.
Higher Order Multidimensional Wave Oriented Upwind Schemes for Flow in Porous Media on Unstructured Grids
Authors: Lamine Sadok , Edwards Michael G. 
Published: February 2009

Abstract
Standard reservoir simulation schemes employ single-point upstream weighting for convective flux approximation. These schemes introduce both coordinate-line numerical diffusion and cross-wind diffusion into the solution that is grid and geometry dependent.
New locally conservative higher-order multi-dimensional upwind schemes that minimize both directional and cross-wind diffusion are presented for convective flow approximation. The new schemes are comprised of two steps; (a) Higher-order approximation that corrects the directional diffusion of the approximation, (b) Truly multi-dimensional upwind approximation, which involves flux approximation using upwind information obtained by upstream tracing along wave-vector paths where wave information travels in multiple dimensions. This approximation reduces cross-wind diffusion. Conditions on tracing direction and CFL number lead to a local maximum principle that ensures stable solutions free of spurious oscillations. The schemes are coupled with full-tensor Darcy flux approximations.
Benefits of the resulting schemes are demonstrated for classical convective test cases in reservoir simulation including cases with full tensor permeability fields, where the methods prove to be particularly effective. The test cases involve a range of unstructured grids with variations in orientation and permeability that lead to flow fields that are poorly resolved by standard simulation methods. The higher dimensional formulations are shown to effectively reduce numerical cross-wind diffusion effects, leading to improved resolution of concentration and saturation fronts.
Convergence of MPFA on Hexahedra
Authors: Matringe S. F. , Juanes R. , Tchelepi H. A. 
Published: February 2009

Abstract
We present a new mixed finite element for hexahedra, conforming in H(div). The new velocity space is similar in construction to that of BDDF of order one, but has four degrees of freedom per face instead of three. The natural degrees of freedom defining the velocity field are the components of the velocity normal to each face at the vertices of that face. We apply the new element to the numerical solution of second order elliptic equations with full tensor coefficients. We prove convergence of the method and provide optimal error estimates for the scalar and vector fields. We use an appropriate numerical quadrature to localize the mixed finite element method into a cell-centered finite difference method. For diagonal tensor coefficients, we recover the usual 7-point stencil. For full tensors, the method leads to a 27-point stencil of multipoint flux approximation (MPFA) methods—specifically the well-known O-method. Our construction allows us to prove, for the first time, convergence of the MFPA O-method on three-dimensional rectangular hexahedra. The results of the error analysis are confirmed by numerical experiments. Although our analysis is restricted to rectangular parallelepipeds, our implementation allows for distorted elements and unstructured grids.
Linear Solver Performance Optimization in Reservoir Simulation Studies
Authors: Mishev Ilya , Beckner Bret , Fedorova Nelli , Terekhov Serge 
Published: February 2009

Abstract
The numerical simulation of oil and gas reservoirs requires the solution of many large linear systems at each time step. The performance of the linear solver depends strongly on the proper choice of parameters for the iterative method and preconditioner. We describe a suite of adaptive algorithms to optimize solver performance that systematically adjusts solver parameters during a simulation. These algorithms are implemented into a software system called Intelligent Performance Assistant (IPA) that has been successfully integrated into ExxonMobil's proprietary reservoir simulator, EMpower™.
The IPA system consists of three parts: IPALight, IPADataBase, and IPAFactory. IPALight implements an online adaptive control mechanism to provide parameters for each linear solver in a simulation. IPALight selects an initial parameter set from IPADataBase of solved cases and manipulates parameters based on the performance of the solver (e.g., solver CPU time, number of iterations, memory usage) using multi-objective optimization algorithms. This strategy improves the CPU time of the solver (frequently by 30% or more) for realistic simulation models when compared to default solver settings.
Runtime solver performance statistics gathered by IPALight for different parameter combinations are stored in IPADataBase. This data can be used by the IPA offline data analysis system, IPAFactory, to exclude all combinations that generated unsatisfactory solver performance including CPU time, memory costs and/or convergence rate. In addition, IPAFactory is used to generate good initial sets of solver parameter combinations that can be used by IPALight for similar cases. This gives improved robustness of reservoir simulations and an additional 10-20% CPU time savings.
First Application of Concentric Nitrogen Injection Technique for a Managed Pressure Drilling Depleted Well in Southern Mexico
Authors: Urbieta A. , Tellez C. Perez , Lupo C. , Castellanos J. M. , Ramirez O. , Puerto G. , Bedoya J. 
Published: February 2009

Abstract
Samaria field in southern Mexico is one of the oldest light oil producers. Reservoir pressures can be classified as highly depleted in cretaceous, the use of nitrogen injection thru the drill pipe to lighten the mud column is a common practice to reach low equivalent circulating densities and avoid massive loss circulation and related hole cleaning problems. Large amounts of nitrogen injection rates are also a common scenario in this specific field many times reaching the technical limit of a multiphase Managed Pressure Drilling application avoiding the friction dominated side of pressure curves. Natural tendency to achieve more production is to drill horizontal wells as demonstrated by the production results of a number of attempts made in the past. However, the presence of high N2 injection rates thru the drill pipe represents a serious challenge for measuring and logging while drilling pulse type downhole tools frustrating the possibility of achieving a full directional control in the reservoir section. Dowhole temperatures are also higher than conventional drilling because of the presence of high gas vs liquid ratios, reaching very fast the technology limits. This document presents the engineering process, planning and design for the drilling with concentric casing nitrogen injection technique in a horizontal well with directional control in real time, into a low pressure reservoir. The technique allowed building up and correcting the well trajectory successfully reaching the proposed targets. (Horizontal length, Drain Area) The steady stable and transient simulations to validate stabilization are also presented along with the final results in terms of production and skin damage.
Evaluation of Well Productivity Loss due to Formation Damage Caused by Spontaneous Imbibition in Underbalanced Drilling
Authors: Khansari Alireza Naziri 
Published: February 2009

Abstract
Under balanced drilling (UBD) is a drilling operation in which effective bottom hole pressure caused by circulation of drilling fluid is taken under near well bore formation pressure. As a result influx of water from aqueous drilling fluid into the formation is prevented. Even though UBD is expected to prevent formation damage and improve well productivity, in some low permeability cases with high capillary pressure counter-current imbibition occurs and reduces well productivity specially for open hole completed horizontal wells. In this paper a new approach to model possible spontaneous imbibition during UBD are presented and the related formation damage is taken into account. The impact of this type of formation damage on well productivity is simulated using a commercial reservoir simulator coupled with a developed toolbox. The simulation result is compared against the absence of spontaneous imbibition in reservoir models with lower capillary pressure. Sensitivity analysis shows that formation damage caused by UBD depends on various reservoir parameters and drilling conditions. Different cases of ROP, hydrostatic pressure of drilling fluid, initial water saturation, and porosity in low permeability reservoir caused by capillary pressure are considered. Surface tension can vary with pressure and temperature; however, it is assumed as negligible in this study. Results show this formation damage should be considered during economics and feasibility studies.
Genetic Deficiency of Itgb2 or ItgaL Prevents Autoimmune Diabetes Through Distinctly Different Mechanisms in NOD/LtJ Mice
Authors: Glawe John D. , Patrick D. Ross , Huang Meng , Sharp Christopher D. , Barlow Shayne C. , Kevil Christopher G. 
Published: February 2009

OBJECTIVEInsulitis is an important pathological feature of autoimmune diabetes; however, mechanisms governing the recruitment of diabetogenic T-cells into pancreatic islets are poorly understood. Here, we determined the importance of leukocyte integrins β2(Itgb2) and αL (ItgaL) in developing insulitis and frank diabetes.RESEARCH DESIGN AND METHODSGene-targeted mutations of either Itgb2 or ItgaL were established on the NOD/LtJ mouse strain. Experiments were performed to measure insulitis and diabetes development. Studies were also performed measuring mutant T-cell adhesion to islet microvascular endothelial cells under hydrodynamic flow conditions. T-cell adhesion molecule profiles and adoptive transfer studies were also performed.RESULTSGenetic deficiency of either Itgb2 or ItgaL completely prevented the development of hyperglycemia and frank diabetes in NOD mice. Loss of Itgb2 or ItgaL prevented insulitis with Itgb2 deficiency conferring complete protection. In vitro hydrodynamic flow adhesion studies also showed that loss of Itgb2 completely abrogated T-cell adhesion. However, ItgaL deficiency did not alter NOD T-cell adhesion to or transmigration across islet endothelial cells. Adoptive transfer of ItgaL-deficient splenocytes into NOD/Rag-1 mice did not result in development of diabetes, suggesting a role for ItgaL in NOD/LtJ T-cell activation.CONCLUSIONSTogether, these data demonstrate that genetic deficiency of Itgb2 or ItgaL confers protection against autoimmune diabetes through distinctly different mechanisms.
Medium-Chain Fatty Acids Improve Cognitive Function in Intensively Treated Type 1 Diabetic Patients and Support In Vitro Synaptic Transmission During Acute Hypoglycemia
Authors: Page Kathleen A. , Williamson Anne , Yu Namyi , McNay Ewan C. , Dzuira James , McCrimmon Rory J. , Sherwin Robert S. 
Published: February 2009

OBJECTIVE
We examined whether ingestion of medium-chain triglycerides could improve cognition during hypoglycemia in subjects with intensively treated type 1 diabetes and assessed potential underlying mechanisms by testing the effect of β-hydroxybutyrate and octanoate on rat hippocampal synaptic transmission during exposure to low glucose.

RESEARCH DESIGN AND METHODS
A total of 11 intensively treated type 1 diabetic subjects participated in stepped hyperinsulinemic- (2 mU · kg−1 · min−1) euglycemic- (glucose ∼5.5 mmol/l) hypoglycemic (glucose ∼2.8 mmol/l) clamp studies. During two separate sessions, they randomly received either medium-chain triglycerides or placebo drinks and performed a battery of cognitive tests. In vitro rat hippocampal slice preparations were used to assess the ability of β-hydroxybutyrate and octanoate to support neuronal activity when glucose levels are reduced.

RESULTS
Hypoglycemia impaired cognitive performance in tests of verbal memory, digit symbol coding, digit span backwards, and map searching. Ingestion of medium-chain triglycerides reversed these effects. Medium-chain triglycerides also produced higher free fatty acids and β-hydroxybutyrate levels compared with placebo. However, the increase in catecholamines and symptoms during hypoglycemia was not altered. In hippocampal slices β-hydroxybutyrate supported synaptic transmission under low-glucose conditions, whereas octanoate could not. Nevertheless, octanoate improved the rate of recovery of synaptic function upon restoration of control glucose concentrations.

CONCLUSIONS
Medium-chain triglyceride ingestion improves cognition without adversely affecting adrenergic or symptomatic responses to hypoglycemia in intensively treated type 1 diabetic subjects. Medium-chain triglycerides offer the therapeutic advantage of preserving brain function under hypoglycemic conditions without causing deleterious hyperglycemia.
Changes in Insulin Sensitivity and Insulin Release in Relation to Glycemia and Glucose Tolerance in 6,414 Finnish Men
Authors: Stančáková Alena , Javorský Martin , Kuulasmaa Teemu , Haffner Steven M. , Kuusisto Johanna , Laakso Markku 
Published: February 2009

OBJECTIVE
We evaluated insulin sensitivity and insulin secretion across the entire range of fasting (FPG) and 2-h plasma glucose (PG), and we investigated the differences in insulin sensitivity and insulin release in different glucose tolerance categories.

RESEARCH DESIGN AND METHODS
A total of 6,414 Finnish men (aged 57 ± 7 years, BMI 27.0 ± 3.9 kg/m2) from our ongoing population-based METSIM (Metabolic Syndrome in Men) study were included. Of these subjects, 2,168 had normal glucose tolerance, 2,859 isolated impaired fasting glucose (IFG), 217 isolated impaired glucose tolerance (IGT), 701 a combination of IFG and IGT, and 469 newly diagnosed type 2 diabetes.

RESULTS
The Matsuda index of insulin sensitivity decreased substantially within the normal range of FPG (−17%) and 2-h PG (−37%) and was approximately −65 and −53% in the diabetic range of FPG and 2-h PG, respectively, compared with the reference range (FPG and 2-h PG &lt;5.0 mmol/l). Early-phase insulin release declined by only approximately −5% within the normal range of FPG and 2-h PG but decreased significantly in the diabetic range of FPG (by 32–70%) and 2-h PG (by 33–51%). Changes in insulin sensitivity and insulin secretion in relation to hyperglycemia were independent of obesity. The predominant feature of isolated IGT was impaired peripheral insulin sensitivity. Isolated IFG was characterized by impaired early and total insulin release.

CONCLUSIONS
Peripheral insulin sensitivity was already decreased substantially at low PG levels within the normoglycemic range, whereas impairment in insulin secretion was observed mainly in the diabetic range of FPG and 2-h PG. Obesity did not affect changes in insulin sensitivity or insulin secretion in relation to hyperglycemia.
Long-Term Prognosis of Diabetic Patients With Critical Limb Ischemia
Authors: Faglia Ezio , Clerici Giacomo , Clerissi Jacques , Gabrielli Livio , Losa Sergio , Mantero Manuela , Caminiti Maurizio , Curci Vincenzo , Quarantiello Antonella , Luppattelli Tommaso , Morabito Alberto 
Published: February 2009

OBJECTIVE
To evaluate the long-term prognosis of critical limb ischemia (CLI) in diabetic patients.

RESEARCH DESIGN AND METHODS
A total of 564 consecutive diabetic patients were hospitalized for CLI from January 1999 to December 2003; 554 were followed until December 2007.

RESULTS
The mean follow-up was 5.93 ± 1.28 years. Peripheral angioplasty (PTA) was performed in 420 (74.5%) and bypass graft (BPG) in 117 (20.6%) patients. Neither PTA nor BPG were possible in 27 (4.9%) patients. Major amputations were performed in 74 (13.4%) patients: 34 (8.2%) in PTA, 24 (21.1%) in BPG, and 16 (59.2%) in a group that received no revascularization. Restenosis occurred in 94 patients, bypass failures in 36 patients, and recurrent ulcers in 71 patients. CLI was observed in the contralateral limb of 225 (39.9%) patients; of these, 15 (6.7%) required major amputations (rate in contralateral compared with initial limb, P = 0.007). At total of 276 (49.82%) patients died. The Cox model showed significant hazard ratios (HRs) for mortality with age (1.05 for 1 year [95% CI 1.03–1.07]), unfeasible revascularization (3.06 [1.40–6.70]), dialysis (3.00 [1.63–5.53]), cardiac disease history (1.37 [1.05–1.79]), and impaired ejection fraction (1.08 for 1% point [1.05–1.09]).

CONCLUSIONS
Diabetic patients with CLI have high risks of amputation and death. In a dedicated diabetic foot center, the major amputation, ulcer recurrence, and major contralateral limb amputation rates were low. Coronary artery disease (CAD) is the leading cause of death, and in patients with CAD history the impaired ejection fraction is the major independent prognostic factor.