bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reducing Reservoir Prediction Uncertainty by Updating a Stochastic Model Using Seismic History Matching
Authors: Stephen Karl D. , MacBeth Colin 
Published: January 2009

SummaryWe have developed a method in which spatial and dynamic information offered by time-lapse, or 4D, seismic surveys is used in history matching of reservoir simulations. Improved predictions of both recovery and areal sweep are then obtained by reducing uncertainty. Flow simulations are converted to predictions of seismic-impedance attributes using a petroelastic transform and suitable rescaling. The resulting misfit between the model and observed data is combined with an equivalent measure for well data, and these are used to constrain simulations by iteratively updating the model. Updated-model probabilities can then be used to analyze uncertainty.The method has been applied to the Schiehallion UK Continental Shelf (UKCS) reservoir. We first found a good match to production and seismic data in the field. From the updated probability distribution of the parameters, we then took the best models from the history-matching process and made predictions to determine the most likely outcomes.We have found that the 4D data reduces uncertainty in predictions of the areal sweep and the pressure distribution. The seismic response is strongest at the injector wells but also helps in the interwell regions. Conventional history matching often struggles to constrain parameters in these regions because of the inherent nonuniqueness of the problem. The uncertainty of permeability- and fault-transmissibility multipliers was also determined in those areas.
Modeling Low-Salinity Waterflooding
Authors: Jerauld Gary R. , Lin C. Y. , Webb Kevin J. , Seccombe Jim C. 
Published: January 2009

Summary
Low-salinity waterflooding is an emerging enhanced-oil-recovery (EOR) technique in which the salinity of the injected water is controlled to improve oil recovery vs. conventional, higher-salinity waterflooding. Corefloods and single-well chemical-tracer tests have shown that low-salinity waterflooding can improve basic waterflood performance by 5 to 38%. This paper describes a model of low-salinity flooding that can be used to evaluate projects; shows the implications of that model and demonstrates its use to represent corefloods, single-well tests, and field-scale simulations; and gives insight into the reservoir engineering of low-salinity floods.
The model represents low-salinity flooding using salinity-dependent oil/water relative permeability functions resulting from wettability change. This is similar to other EOR modeling, and conventional fractional-flow theory can be adapted to describe the process in 1D for secondary and tertiary low-salinity waterflooding. This simple analysis shows that while some degree of connate-water banking occurs, it need not hinder the process.
Mixing of injected water with in-situ water delays the attainment of low salinity, potentially preventing attainment of low salinity all together if very small slugs of low-salinity water are used. This paper demonstrates the importance of mixing to modeling of low-salinity flooding and suggests addressing it in engineering calculations. Care must be taken in representing mixing appropriately in interpreting data and in constructing models. The use of numerical dispersion to represent physical dispersion in 1D, radial, and pattern simulations of this process is demonstrated (i.e., coarse-grid simulations are shown to give the same result as fine-grid simulations with an appropriately large physical dispersion). In many applications, the fine-grid simulation necessary to represent appropriate levels of dispersion is not practical, and pseudoization is necessary. We demonstrate that this can be achieved by changing the salinity dependence and shapes of relative permeability curves.
Relative Permeability Coupled Saturation-Height Models on the Basis of Hydraulic (Flow) Units in a Gas Field
Authors: Amabeoku Maclean O. , Kersey David G. , BinNasser Rami H. , Al-Belowi Ali R. 
Published: January 2009

Summary
Saturation/height functions on the basis of unique flow units have been developed as part of an integrated petrophysical analysis of a gas field. Furthermore, coupling the saturation/height functions with appropriate relative permeability models has effectively quantified hydrocarbon saturation, classified producibility of intervals, and defined critical water saturation. The results show that linking depositional and diagenetic rock fabric with flow units and then linking the flow units with zones that have similar core capillary pressure and relative permeability relationships have enhanced the utility of the saturation models. The saturation/height functions provided more-accurate water saturation in the study field, and potentially they can overcome uncertainties associated with log interpretation by use of Archie or shaly-sand models.
The saturation/height models were developed from core capillary pressure (Pc) data to calculate water saturation vs. depth, which is independent of logs. The relative permeability models were obtained from special-core analysis (SCA). Consequently, the core-based saturation/height functions can be useful in the calibration of log-based petrophysical models and with relative permeability can also be used to estimate water/gas ratios (WGRs) and critical water saturation.
Capillary pressure and relative permeability curves from SCA studies were distributed into corresponding flow units, on the basis of the calculated flow-zone indicators(FZIs). Saturation/height functions were then developed for each unit and were used to calculate water saturation in the study field. The most accurate flow-unit-based saturation model that evolved is a function only of porosity and of height above the free-water level; it does not require permeability in its application; and it performed better than the Leverett J-function in this field.
Coupled with hydraulic unit (HU)-based relative permeability curves, the saturation models may provide more comprehensive petrophysical interpretation in gas-bearing formations and may highlight potential differences in reservoir producibility.
Using Laboratory Flow Experiments and Reactive Chemical Transport Modeling for Designing Waterflooding of the Agua Fria Reservoir, Poza Rica-Altamira Field, Mexico
Authors: Birkle P. , Pruess K. , Xu T. , Hernández Figueroa R. A. , Díaz López M. , Contreras López E. 
Published: January 2009

Summary
Waterflooding for enhanced oil recovery requires that injected waters must be chemically compatible with connate reservoir waters, in order to avoid mineral dissolution-and-precipitation cycles that could seriously degrade formation permeability and injectivity. Formation plugging is a concern especially in reservoirs with a large content of carbonates, such as calcite and dolomite, as such minerals typically react rapidly with an aqueous phase, and have strongly temperature-dependent solubility. Clay swelling also can pose problems. During a preliminary waterflooding pilot project, the Poza Rica-Altamira oil field, bordering the Gulf coast in the eastern part of Mexico, experienced injectivity loss after 5 months of reinjection of formation waters into Well AF-847 in 1999. Acidizing with hydrochloric acid (HCl) restored injectivity.
We report on laboratory experiments and reactive-chemistry modeling studies that were undertaken in preparation for long-term waterflooding at the Agua Fría reservoir. Using analogous core plugs obtained from the same reservoir interval, laboratory core-flood experiments were conducted to examine the sensitivity of mineral-dissolution and -precipitation effects to water composition. Native reservoir water, chemically altered waters, and distilled water were used, and temporal changes in core permeability, mineral quantities, and aqueous concentrations of solutes were monitored. The experiments were simulated with the multiphase, nonisothermal reactive transport code TOUGHREACT™ (Lawrence Berkeley National Laboratory, Berkeley, California, 2004), and reasonable-to-good agreement was obtained for changes in solute concentrations. Clay swelling caused an additional impact on permeability behavior during coreflood experiments, whereas the modeled permeability depends exclusively on chemical processes. TOUGHREACT was then used for reservoir-scale simulation of injecting ambient-temperature water (30°C, 86°F) into a reservoir with initial temperature of 80°C (176°F). Untreated native reservoir water was found to cause serious porosity and permeability reduction because of calcite precipitation, which is promoted by the retrograde solubility of this mineral. Using treated water that performed well in the laboratory flow experiments was found to avoid excessive precipitation and allowed injection to proceed.
An Integrated Geologic and Engineering Assessment of Fracture-Flow Potential in the Ratawi Reservoir of the Wafra Field, Partitioned Neutral Zone
Authors: Whitaker A. E. , Kabir C. S. , Narr W. 
Published: January 2009

SummaryThe extent to which fractures affect fluid pathways is a vital component of understanding and modeling fluid flow in any reservoir. We examined the Wafra Ratawi grainstone for which production extending for 50 years, including recent horizontal drilling, has provided some clues about fractures, but their exact locations, intensity, and overall effect have been elusive. In this study, we find that a limited number of total fractures affect production characteristics of the Ratawi reservoir. Although fractures occur throughout the Wafra field, fracture-influenced reservoir behavior is confined to the periphery of the field where the matrix permeability is low. This work suggests that for the largest part of the field, explicit fractures are not necessary in the next-generation Earth and flow-simulation models.The geologic fracture assessment included seismic fault mapping and fracture interpretation of image logs and cores. Fracture trends are in the northeast and southwest quadrants, and fractures are mineralized toward the south and west of the field. Pressure-falloff tests on some peripheral injectors indicate partial barriers, and most of these wells lie on seismic-scale faults in the reservoir, suggesting partial sealing. A few wells show fractured-reservoir production characteristics, and rate-transient analysis on a few producers indicates localized dual-porosity behavior. Producers proximal to dual-porosity wells display single-porosity behavior, however, to attest to the notion of localized fracture response. The spatially restricted fracture-flow characteristics appear to correlate with fracture or vug zones in a low-permeability reservoir.Presence of fracture-flow behavior was tested by constructing the so-called flow-capacity index (FCI), the ratio of khwell (well test-derived value) to khmatrix (core-derived property). Data from 80 wells showed khmatrix to be consistently higher than khwell, a relationship that suggests insignificant fracture production in these wells.
Economic Decision Making and the Application of Nonparametric Prediction Models
Authors: Attanasi E. D. , Coburn T. C. , Freeman P. A. 
Published: January 2009

Summary
Sustained increases in energy prices have focused attention on gas resources in low-permeability shale or in coals that were previously considered economically marginal. Daily well deliverability is often relatively small, although the estimates of the total volumes of recoverable resources in these settings are often large. Planning and development decisions for extraction of such resources must be areawide because profitable extraction requires optimization of scale economies to minimize costs and reduce risk. For an individual firm, the decision to enter such plays depends on reconnaissance-level estimates of regional recoverable resources and on cost estimates to develop untested areas.
This paper shows how simple nonparametric local regression models, used to predict technically recoverable resources at untested sites, can be combined with economic models to compute regional-scale cost functions. The context of the worked example is the Devonian Antrim-shale gas play in the Michigan basin. One finding relates to selection of the resource prediction model to be used with economic models. Models chosen because they can best predict aggregate volume over larger areas (many hundreds of sites) smooth out granularity in the distribution of predicted volumes at individual sites. This loss of detail affects the representation of economic cost functions and may affect economic decisions. Second, because some analysts consider unconventional resources to be ubiquitous, the selection and order of specific drilling sites may, in practice, be determined arbitrarily by extraneous factors. The analysis shows a 15-20% gain in gas volume when these simple models are applied to order drilling prospects strategically rather than to choose drilling locations randomly.
Key Aspects of Project Design for Polymer Flooding at the Daqing Oilfield
Authors: Wang Dongmei , Seright R. S. , Shao Zhenbo , Wang Jinmei 
Published: January 2009

Summary
This paper describes the design procedures that led to favorable incremental oil production and reduced water production during 12 years of successful polymer flooding in the Daqing oil field. Special emphasis is placed on some new design factors that were found to be important on the basis of extensive experience with polymer flooding. These factors include (1) recognizing when profile modification is needed before polymer injection and when zone isolation is of value during polymer injection, (2) establishing the optimum polymer formulations and injection rates, and (3) time-dependent variation of the molecular weight of the polymer used in the injected slugs.
For some Daqing wells, oil recovery can be enhanced by 2 to 4% of original oil in place (OOIP) with profile modification before polymer injection. For some Daqing wells with significant permeability differential between layers and no crossflow, injecting polymer solutions separately into different layers improved flow profiles, reservoir sweep efficiency, and injection rates, and it reduced the water cut in production wells. Experience over time revealed that larger polymer-bank sizes are preferred. Bank sizes grew from 240–380 mg/L.PV during the initial pilots to 640 to 700 mg/L.PV in the most recent large-scale industrial sites [pore volume (PV)]. Economics and injectivity behavior can favor changing the polymer molecular weight and polymer concentration during the course of injecting the polymer slug. Polymers with molecular weights from 12 to 35 million Daltons were designed and supplied to meet the requirements for different reservoir geological conditions. The optimum polymer-injection volume varied around 0.7 PV, depending on the water cut in the different flooding units. The average polymer concentration was designed approximately 1000 mg/L, but for an individual injection station, it could be 2000 mg/L or more. At Daqing, the injection rates should be less than 0.14–0.20 PV/year, depending on well spacing.
The Application of Cutoffs in Integrated Reservoir Studies
Authors: Worthington Paul F. 
Published: January 2009

Summary
Methodologies have been developed for applying net reservoir and thence net pay cutoffs in cases of primary and waterflood depletion. The cutoffs are dynamically-conditioned to be reservoir-specific (i.e., they are tied back to a reference permeability parameter in a way that is driven by the reservoir data themselves). They also honor scale, where feasible, and are conformable with any pertinent rock-typing. For primary depletion, the Leverett equivalent circular pore diameter has been used to distinguish between reservoir and nonreservoir rock. This composite parameter can incorporate mobility for multiphase work. It is linked to a discrete core porosity under simulated reservoir conditions, so the adopted net reservoir cutoff is expressed as a limiting porosity. For waterflood depletion, an extrapolated endpoint relative permeability to oil has proved effective for the same purpose. Here, the zero endpoint relative permeability is linked to a conventional "absolute" core permeability corrected to reservoir conditions. Porosity is tied back to this limiting absolute permeability so that the net reservoir cutoff is again expressed in terms of porosity. Consequently, in both cases, the discrete porosity cutoffs have a dynamic significance. Other cutoff parameters, such as shale volume fraction and water saturation, can be tied back to these. A proposed workflow for applying dynamically-conditioned cutoffs allows data character to drive their use in integrated reservoir studies. The workflow constitutes a basis for greater technical consistency in the estimation of ultimate hydrocarbon recovery. However, the treatment is not exclusive, and other approaches to the determination of net pay will emerge as more reservoirs are considered.
Incremental Value of the Pancreas Allograft to the Survival of Simultaneous Pancreas-Kidney Transplant Recipients
Authors: Salvalaggio Paolo R. , Dzebisashvili Nino , Pinsky Brett , Schnitzler Mark A. , Burroughs Thomas E. , Graff Ralph , Axelrod David A. , Brennan Daniel C. , Lentine Krista L. 
Published: January 2009

OBJECTIVE
To quantify the incremental survival benefit of the pancreas allograft in simultaneous pancreas-kidney (SPK) transplant recipients.

RESEARCH DESIGN AND METHODS
Data from the national transplant database from 2000 to 2007 were analyzed. SPK recipients who had functioning allografts to 1-year post transplant (n = 3,304) were compared with those who had failure of the renal (n = 233) or pancreatic (n = 112) graft. The main outcome was a projection of 10 life-years of patient survival beyond the first transplant anniversary.

RESULTS
Recipients with function of both organs accrued 9.4 life-years following transplantation. Projected survival in patients with kidney failure was reduced to 2.5 life-years. Pancreas failure reduced predicted survival to 8 life-years. Renal allograft failure impacts life expectancy significantly (adjusted hazard ratio [aHR] 12.13). However, pancreas allograft failure was also associated with reduced survival (aHR 2.62).

CONCLUSIONS
Although the majority of the survival benefit of SPK transplant is due to the renal transplant, pancreas allograft function does contribute to patient survival.
Synergy Between Adiposity, Insulin Resistance, Metabolic Risk Factors, and Inflammation in Adolescents
Authors: Huang Rae-Chi , Mori Trevor A. , Burke Valerie , Newnham John , Stanley Fiona J. , Landau Louis I. , Kendall Garth E. , Oddy Wendy H. , Beilin Lawrence J. 
Published: January 2009

OBJECTIVE
The purpose of this study was to investigate relationships between inflammatory markers and components of a metabolic syndrome cluster in adolescents.

RESEARCH DESIGN AND METHODS
This was a cross-sectional analysis of an Australian childhood cohort (n = 1,377) aged 14 years. Cluster analysis defined a “high-risk” group similar to adults with metabolic syndrome. Relevant measures were anthropometry, fasting insulin, glucose, lipids, inflammatory markers, liver function, and blood pressure.

RESULTS
Of the children, 29% fell into a high-risk metabolic cluster group compared with 2% by a pediatric metabolic syndrome definition. Relative to the “low-risk” cluster, they had higher BMI (95% CI 19.5–19.8 vs. 24.5–25.4), waist circumference (centimeters) (95% CI 71.0–71.8 vs. 83.4–85.8), insulin (units per liter) (95% CI 1.7–1.8 vs. 3.5–3.9), homeostasis model assessment (95% CI 1.7–1.8 vs. 3.5–3.9), systolic blood pressure (millimeters of mercury) (95% CI 110.8–112.1 vs. 116.7–118.9), and triglycerides (millimoles per liter) (95% CI 0.78–0.80 vs. 1.25–1.35) and lower HDL cholesterol (millimoles per liter) (95% CI 1.44–1.48 vs. 1.20–1.26). Inflammatory and liver function markers were higher in the high-risk group: C-reactive protein (CRP) (P &lt; 0.001), uric acid (P &lt; 0.001), alanine aminotransferase (ALT) (P &lt; 0.001), and γ-glutamyl transferase (GGT) (P &lt; 0.001). The highest CRP, GGT, and ALT levels were restricted to overweight children in the high-risk group.

CONCLUSIONS
Cluster analysis revealed a strikingly high proportion of 14 year olds at risk of cardiovascular disease–related metabolic disorders. Adiposity and the metabolic syndrome cluster are synergistic in the pathogenesis of inflammation. Systemic and liver inflammation in the high-risk cluster is likely to predict diabetes, cardiovascular disease, and nonalcoholic fatty liver disease.
Affine compact almost-homogeneous manifolds of cohomogeneity one
Authors: Guan Daniel 
Published: January 2009

AbstractThis paper is one in a series generalizing our results in [12, 14, 15, 20] on the existence of extremal metrics to the general almost-homogeneous manifolds of cohomogeneity one. In this paper, we consider the affine cases with hypersurface ends. In particular, we study the existence of Kähler-Einstein metrics on these manifolds and obtain new Kähler-Einstein manifolds as well as Fano manifolds without Kähler-Einstein metrics. As a consequence of our study, we also give a solution to the problem posted by Ahiezer on the nonhomogeneity of compact almost-homogeneous manifolds of cohomogeneity one; this clarifies the classification of these manifolds as complex manifolds. We also consider Fano properties of the affine compact manifolds.
Stable outer conjugacy and strong Morita equivalence of group actions on pro-C *-algebras
Authors: Joiţa Maria 
Published: January 2009

AbstractWe show that two continuous inverse limit actions α and β of a locally compact group G on two pro-C *-algebras A and B are stably outer conjugate if and only if there is a full Hilbert A-module E and a continuous action u of G on E such that E and E *(the dual module of E) are countably generated in M(E)(the multiplier module of E), respectively M(E *) and the pair (E, u) implements a strong Morita equivalence between α and β. This is a generalization of a result of F. Combes [Proc. London Math. Soc. 49(1984), 289–306].
Gastrocnemius-Soleus Muscle Tendon Unit Changes Over the First 12 Weeks of Adjusted Age in Infants Born Preterm
Authors: Grant-Beuttler Marybeth , Palisano Robert J , Miller Debra P , Reddien Wagner Barbara , Heriza Carolyn B , Shewokis Patricia A 
Published: January 2009

Background and PurposeDifferences in the gastrocnemius-soleus muscle and tendon have been documented shortly after birth in infants born preterm compared with infants born at term. Knowledge of muscle tendon unit lengths at term age to 12 weeks of age in infants born preterm may be useful in understanding motor development.Participants and MethodGastrocnemius-soleus muscle tendon unit lengths were compared at term age, at 6 weeks of age, and at 12 weeks of age (preterm adjusted age) in 20 infants born full term and 22 infants born preterm.ResultsSignificant differences were found between the 2 groups on taut tendon, relaxed muscle length (AO); taut tendon, stretched muscle length (AMax); and muscle stretch (AO to AMax). Infants born preterm demonstrated measures of AO and AMax in positions of greater plantar flexion compared with infants born full term. Significant differences in measurements of AO were found between term age and 12 weeks of age, indicating that the tendon lengthens during this period for both groups.Discussion and ConclusionThese results provide knowledge of musculoskeletal development of the gastrocnemius-soleus muscle and tendon. Differences in musculoskeletal measurements are consistent with uterine confinement in the last weeks of full-term gestation. These findings have implications when examining the musculoskeletal system in infants born preterm who are demonstrating functional changes.