bluuebunny/crossref_metadata_2025_split huggingface dataset:
Understanding Permeability Measurements in Tight Shales Promotes Enhanced Determination of Reservoir Quality
Authors: Suarez-Rivera Roberto , Chertov Maxim , Willberg Dean , Green Sidney , John Keller 
Published: October 2012

Abstract
Proper characterization of reservoir quality of tight shales is critical for evaluating reservoir potential. These reservoir quality properties typically include hydrocarbon filled porosity, permeability, organic content and maturation, and pore pressure. Of these, permeability measurements are among the most complex to obtain, and have been subject to much discussion. Key concerns are the lack of analytic modeling, poor reliability, poor consistency, and ignoring stress sensitivity in the measurements. This paper reviews the pressure decay permeability method using crushed rock, and includes laboratory test results to validate the findings. Part of the review is a numerical model for the pressure decay method. This model includes significant processes of pipe flow in the equipment, thermal effects, diffusion into rock fragments, Klinkenberg effects, and size, shape and anisotropic permeability of the fragments.
The paper shows that the measured permeability stress dependence, in tight shales, arises from coring induced microcracks. These result from failure of weak contact planes that are naturally occurring within tight shales and fail during coring and core retrieval. Permeability stress dependence in-situ is slight, as is show by compression test measurements to greater than thirty thousand psi. Crushing the rock to create small fragments for permeability measurements effectively removes these microcracks, and allows evaluation of real in-situ properties. Alternatively, closing microcracks by applying confining stress on plug samples, as routinely done for steady state and pulse decay measurements, is possible, but problematic because the critical stress required for microcrack closure changes from rock to rock facies.
The pressure decay permeability method on crushed rock is shown to provide very consistent results that agree with other measurement techniques. The numerical model relates specific ranges of fragment sizes and testing conditions, to measured ranges of permeability. This allows permeability measurements and numerical model analysis for a broad range of variability in permeability that can be measured in heterogeneous tight shales. With some exceptions (e.g., Cui et.al. 2009), the fundamental understanding of the petrophysical properties of tight shales have not previously included rigorous confirmation of experimental measurements by analytical methods.
New Multistage Fracturing Process Offers Real-Time Control of Rate and Proppant Concentration at the Perforations
Authors: Mcneil Fraser , Harbolt William 
Published: October 2012

Abstract
The demand for more efficient, effective, and environmentally acceptable hydraulic fracturing solutions will continue into the future as shale reservoirs play more of a critical role in meeting the rising energy demand. The measurement of success for tomorrow’s wells will not just be improved operational efficiency and initial production, but will include long-term well performance and reduced environmental impact. Operators and service companies must remove the uncertainty associated with conventional hydraulic fracturing techniques and aim simply to generate the desired number of fractures while ensuring that proppant is placed accurately to achieve good conductivity for the life of the well. Some of the disadvantages of conventional well stimulation methods include the following: Uncertainty of the number of fractures initiated within cluster perforations.Uncertainty of proppant distribution along multiple fractures.Proppant schedules designed to avoid screenout and not provide optimum conductivity.Overflushing of the near-wellbore (NWB) region.NWB damage as a result of conventional perforating.
This paper presents a coiled tubing (CT) fracturing solution designed to eliminate these issues, while also delivering a new level of treatment flexibility by using real-time control of rate and proppant concentration at the perforations. This new approach to hydraulic fracturing reduces hydraulic horsepower requirements and reduces overall water usage significantly, while maximizing the return on investment (ROI) for the operator.
The Effect of Hole Angle and Cementing Complications on HPHT Well Integrity
Authors: Yuan Zhaoguang , Schubert Jerome , Teodoriu Catalin 
Published: October 2012

Abstract
The failure probability of wellbore is high in HPHT gas wells because of the effect of the hole angle, the cementing complications and the high pressure high temperature environment. However, most of the researches about the cement problems are studied by two dimensional modeling. The effect of hole angle and cement complications on HPHT well integrity in three dimension is hardly studied.
In the analysis, the finite element method was used to build a three dimension simulation model where the hole angle, casing eccentricity, and cement channels are considered. One cement system (118-lbm/ft3) commonly applied in oil field is used to study the effect of cement complications on the wellbore integrity. The hole angle, cement channel angle, and casing eccentricity are the variables taken into account and an attempt is made to which parameter is the most important and its effects on wellbore failure.
In the cement channeling, the casing has highest von Mises stress at the hole angle of 90°, and the cement tends to fail in tension. The casing eccentricity tends to reduce cement shear stress, and tensile stress but increase cement compressive stress. The cement has the highest compressive failure probability in casing eccentricity condition. At the casing eccentricity lower than 40%, for different hole angle, the casing eccentricity has minor effect on the casing.
This paper presents the sensitivities of the variables and gives a better understanding of the effect of hole angle and cement complications on the HPHT well integrity.
Play-Wide Well Performance Analysis in Montney Siltstone
Authors: Okouma V. , Vitthal S. , Nair Narayan , Miller Mark A. 
Published: October 2012

Abstract
Multi-stage fractured horizontal wells (MFHW) in unconventional resource plays often present formidable reservoir management challenges, particularly with regard to capital utilization and allocation. In this study, well performance histories of some 74 wells in the Montney siltstone play were investigated with a common and consistent analytical framework. Parameters determined from the analyses are key indicators of the combined result of reservoir quality and hydraulic fracture performance (subsurface and completions). The analytical approach utilized in this study was then used to provide robust physics-based forecasts that directly recognize and incorporate interpretation non-uniqueness. Through a forecasting regimen that explicitly provides expected ranges of results, insights and conclusions in field optimization, well spacing and completions design have been drawn.
A real distribution of well productivity and predicted recovery enabled identification of "sweet spots". Openhole completions technique did not show poorer performance compared to limited entry style completions, though further evaluation and surveillance would seem warranted. Wells that were flowing under a "high-drawdown" showed a lower productivity, higher completion resistance (skin) to flow, and lowest predicted final recovery.
Wells completed at 50 m fracture spacing and 30 tonnes of proppant per cluster performed similarly to 100 m spacing and 60 tonnes per cluster, suggesting no apparent difference in capital efficiency between these two completion styles. Results indicate that the frac half lengths in the 50 m cluster spacing wells are shorter compared to wells with 100 m cluster spacing (based on the reduction in the amount of proppant pumped per cluster). Trends of estimated original gas-in-place inside the SRV and predicted 30-year recovery for wells drilled at close well spacings, (closer than 400 m between wellbores) indicate effects of inter-well interference. Performance of wells at 200 m well spacing seem to be affected the most by inter-well interference.
A consistent workflow for analyzing well performance and predicting future performance of MFHW in unconventional gas wells is presented that provides a means to assess the impact of business and development decisions and determining practices worth replicating across the Montney play.
Unique Solution to Repair Casing Failure in a HTHP Wellbore Allows for Successful Multi-Stage Stimulation Treatment in an Unconventional Reservoir
Authors: Wellhoefer Ben , Stegent Neil , Tunstall Michael , Veillette Christian , Frazier Garrett 
Published: October 2012

Abstract
Horizontal shale completions require multi-stage high-pressure hydraulic fracturing stimulation treatments in order to deliver commercially viable production in low permeability reservoirs. Unconventional shale plays, such as the Eagle Ford and Haynesville Shale, often can require stimulation treatments that must be implemented in high pressure and high temperature (HPHT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So what happens when the pre-frac casing pressure integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will frac stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled tubing completions. Unfortunately, these solutions can have pressure limitations, and in addition, can be cost prohibitive.
The authors of this paper will discuss how design of a 4-in. tie-back string with flush joint connections equal to the properties of the casing was capable of repairing a 5-1/2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable packer technology was used to anchor the casing in place. A special flow-thru frac plug was designed so that it could be pumped through the 4-in. tie-back casing and set in the 4-1/2-in. lateral, allowing a plug-and-perf fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated 1), that the pressure isolation integrity of the casing system was satisfactory; and 2), that the flow-thru frac plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford Shale. True vertical depth (TVD) was ~ 13,000 ft, bottomhole temperature (BHT) was ~325°F with a 0.95 psi/ft frac gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.
Re-injecting Produced Water into Tight Oil Reservoirs
Authors: Yong Chen , Wu Oliver , Xiao Jon H , Klotz Eric 
Published: October 2012

Abstract
The technical challenges regarding re-injection of produced water into tight oil reservoirs are discussed based on commercial experience. This paper demonstrates a successful case study based on a project that launched in 2005. The objective was to treat 320 m3/day of produced wastewater for tight oil reservoir re-injection. The effluent requirements were less than 1ppm oil, less than 1ppm TSS, and less than 0.8 micron particle size. The performance during the past 5 years of operation will be reviewed. Due to the unique composition of the influent water and very strict treatment requirements, this process was designed to overcome significant technical challenges. The process includes dissolved air flotation, micro-media filtration and UF membrane technology.
This paper discusses the process configuration with an emphasis on actual operating results. The improvement in oil production and other significant findings will also be presented and reviewed.
Market efficiency and welfare effects of inter-sectoral water allocation in South Africa
Authors: Juana James S. , Strzepek Kenneth M. , Kirsten Johann F. 
Published: October 2012

The need for increased agricultural production to meet the growing demand for food, coupled with concerns for environmental sustainability, economic growth and poverty reduction has increased demand on the already scarce water in South Africa. At the same time, because of agriculture's minimal contribution, compared to the industrial and mining sectors, to South Africa's GDP and employment, the call to reallocate water from agriculture to non-agricultural use has been intensified.
This study updates the 1998 Social Accounting Matrix (SAM) for South Africa and uses the computable general equilibrium model to analyze the impact of water reallocation from agriculture to the non-agricultural sectors on output growth, value added at factor cost, which captures the payments from the production sectors to the factors of production, and households' welfare.
Using different water reallocation scenarios, the simulation results indicate that water reallocation from agriculture to non-agricultural sectors beyond the level of a market allocation scenario will lead to a decline in sectoral output and a significant deterioration in the welfare of poor households. It thus undermines development efforts aimed at reducing the existing level of poverty in the country.
Auditors' Consideration of Material Income-Increasing versus Material Income-Decreasing Items during the Audit Process
Authors: Desai Naman K. , Gerard Gregory J. 
Published: October 2012

SUMMARY:
We examine how auditors' consideration of material items is affected by each item's directional impact on income. Prior research indicates that auditors face greater litigation risk for non-detection of fraudulent income-increasing items compared to income-decreasing items. Therefore, we expect that auditors will spend greater cognitive effort evaluating material income-increasing (as opposed to income-decreasing) items, resulting in superior memories for such items. However, in an effort to direct auditors' attention to both increasing and decreasing material items, we manipulate whether or not auditors were asked to form expectations about the future effects of material items. Our results indicate that auditors' memories for income-increasing items are significantly greater than that for income-decreasing items when auditors are not asked to form expectations about the future effects of the items. However, this difference is not observed when auditors are asked to form expectations about future effects of each item. Furthermore, our results indicate that auditors are less likely to refer back to the work papers to verify the accuracy of income-decreasing items compared to income-increasing items. This suggests that auditors are not inclined to compensate for their poor memory of income-decreasing items by referring to working papers. However, it also suggests that auditors compensate for the greater risk associated with income-increasing items by requiring greater verification of such items.
Data Availability: Contact the authors.
Lessons From the Mixed-Meal Tolerance Test
Authors: Besser Rachel E.J. , Shields Beverley M. , Casas Rosaura , Hattersley Andrew T. , Ludvigsson Johnny 
Published: October 2012

OBJECTIVE
Mixed-meal tolerance test (MMTT) area under the curve C-peptide (AUC CP) is the gold-standard measure of endogenous insulin secretion in type 1 diabetes but is intensive and invasive to perform. The 90-min MMTT-stimulated CP ≥0.2 nmol/L (90CP) is related to improved clinical outcomes, and CP ≥0.1 nmol/L is the equivalent fasting measure (FCP). We assessed whether 90CP or FCP are alternatives to a full MMTT.

RESEARCH DESIGN AND METHODS
CP was measured during 1,334 MMTTs in 421 type 1 diabetes patients aged &lt;18 years at 3, 9, 18, 48, and 72 months duration. We assessed: 1) correlation between mean AUC CP and 90CP or FCP; 2) sensitivity and specificity of 90CP ≥0.2 nmol/L and FCP ≥ 0.1 nmol/L to detect peak CP ≥0.2 nmol/L and the equivalent AUC CP; and 3) how the time taken to reach the CP peak varied with age of diagnosis and diabetes duration.

RESULTS
AUC CP was highly correlated to 90CP (rs = 0.96; P &lt; 0.0001) and strongly correlated to FCP (rs = 0.84; P &lt; 0.0001). AUC CP ≥23 nmol/L/150 min was the equivalent cutoff for peak CP ≥0.2 nmol/L (98% sensitivity/97% specificity). A 90CP ≥0.2 nmol/L correctly classified 96% patients using AUC or peak CP, whereas FCP ≥0.1 nmol/L classified 83 and 85% patients, respectively. There was only a small difference seen between peak and 90CP (median 0.02 nmol/L). The CP peak occurred earlier in patients with longer diabetes duration (6.1 min each 1-year increase in duration) and younger age (2.5 min each 1-year increase).

CONCLUSIONS
90CP is a highly sensitive and specific measure of AUC and peak CP in children and adolescents with type 1 diabetes and offers a practical alternative to a full MMTT.
Diabetes Impairs Stem Cell and Proangiogenic Cell Mobilization in Humans
Authors: Fadini Gian Paolo , Albiero Mattia , Vigili de Kreutzenberg Saula , Boscaro Elisa , Cappellari Roberta , Marescotti Mariacristina , Poncina Nicol , Agostini Carlo , Avogaro Angelo 
Published: October 2012

OBJECTIVE
Diabetes mellitus (DM) increases cardiovascular risk, at least in part, through shortage of vascular regenerative cells derived from the bone marrow (BM). In experimental models, DM causes morphological and functional BM alterations, but information on BM function in human DM is missing. Herein, we sought to assay mobilization of stem and proangiogenic cells in subjects with and without DM.

RESEARCH DESIGN AND METHODS
In a prospective trial (NCT01102699), we tested BM responsiveness to 5 μg/kg human recombinant granulocyte colony–stimulating factor (hrG-CSF) in 24 individuals with DM (10 type 1 and 14 type 2) and 14 individuals without DM. Before and 24 h after hrG-CSF, we quantified circulating stem/progenitor cells and total and differential white blood cell counts. We also evaluated in vivo the proangiogenic capacity of peripheral blood mononuclear cells using the Matrigel plug assay.

RESULTS
In response to hrG-CSF, levels of CD34+ cells and other progenitor cell phenotypes increased in subjects without DM. Patients with DM had significantly impaired mobilization of CD34+, CD133+, and CD34+CD133+ hematopoietic stem cells and CD133+KDR+ endothelial progenitors, independently of potential confounders. The in vivo angiogenic capacity of peripheral blood mononuclear cells significantly increased after hrG-CSF in control subjects without DM, but not in patients with DM. DM was also associated with the inability to upregulate CD26/DPP-4 on CD34+ cells, which is required for the mobilizing effect of granulocyte colony–stimulating factor.

CONCLUSIONS
Stem and proangiogenic cell mobilization in response to hrG-CSF is impaired in DM, possibly because of maladaptive CD26/DPP-4 regulation. These alterations may hamper tissue repair and favor the development of cardiovascular complications.
Prevalence of serum antibody titers against feline panleukopenia virus, feline herpesvirus 1, and feline calicivirus in cats entering a Florida animal shelter
Authors: DiGangi Brian A. , Levy Julie K. , Griffin Brenda , McGorray Susan P. , Dubovi Edward J. , Dingman Patricia A. , Tucker Sylvia J. 
Published: October 2012

Abstract
Objective—To determine the proportion of cats entering a Florida animal shelter with serum antibody titers against feline panleukopenia virus (FPV), feline herpesvirus 1 (FHV1), and feline calicivirus (FCV) and to identify factors associated with seropositivity.
Design—Cross-sectional study.
Animals—347 cats admitted to a Florida animal shelter.
Procedures—Within 24 hours after admission to the animal shelter, blood samples were collected from all cats ≥ 8 weeks of age. Serum antibody titers against FPV were determined via a hemagglutination inhibition assay, and those against FHV1 and FCV were determined via virus neutralization assays. Age, sex, environment (urban or rural), source (stray or previously owned), evidence of previous caregiving, health status (healthy or not healthy), and outcome (adoption, transfer, return to owner, or euthanasia) were evaluated as potential factors associated with antibody seropositivity.
Results—Of 347 cats, 138 (39.8%), 38 (11.0%), and 127 (36.6%) had antibody titers ≥ 40, ≥ 8, and ≥ 32 (ie, seropositive) against FPV, FHV1, and FCV, respectively. Factors associated with seropositivity included being neutered, age ≥ 6 months, and being relinquished by an owner. On multivariable analysis, health status at shelter admission, environment, vaccination at shelter admission, and outcome were not associated with seropositivity.
Conclusions and Clinical Relevance—Most cats were seronegative for antibodies against FPV, FHV1, and FCV at the time of admission to an animal shelter. These findings supported current guidelines that recommend vaccination of all cats immediately after admission to animal shelters, regardless of the source or physical condition.
Evaluation of heart murmurs in chinchillas (Chinchilla lanigera): 59 cases (1996–2009)
Authors: Pignon Charly , Sanchez-Migallon Guzman David , Sinclair Kristen , Baey Charlotte , Pignon Jean-Pierre , Mayer Joerg , Kittleson Mark D. , Paul-Murphy Joanne 
Published: October 2012

Abstract
Objective—To determine the prevalence of heart murmurs in chinchillas (Chinchilla lanigera) and determine whether heart murmurs were associated with cardiac disease.
Design—Retrospective multi-institutional case series.
Animals—260 chinchillas.
Procedures—Medical records of all chinchilla patients evaluated at the Tufts University Foster Hospital for Small Animals between 2001 and 2009, the University of California-Davis William R. Pritchard Veterinary Medical Teaching Hospital between 1996 and 2009, and the University of Wisconsin Veterinary Medical Teaching Hospital between 1998 and 2009 were reviewed.
Results—Prevalence of heart murmurs was 23% (59/260). Of 15 chinchillas with heart murmurs that underwent echocardiography, 8 had echocardiographic abnormalities, including dynamic right ventricular outflow tract obstruction, mitral regurgitation, hypertrophy of the left ventricle, tricuspid regurgitation, and hypovolemia. Echocardiographic abnormalities were approximately 29 times as likely (OR, 28.7) to be present in chinchillas with a murmur of grade 3 or higher than in chinchillas without a murmur.
Conclusions and Clinical Relevance—Results suggested that heart murmurs are common in chinchillas and that chinchillas with heart murmurs often have echocardiographic abnormalities, with valvular disease being the most common. On the basis of these results, we believe that echocardiography should be recommended for chinchillas with heart murmurs, especially older chinchillas with murmurs of grade 3 or higher. Further prospective studies are needed to accurately evaluate the prevalence of cardiac disease in chinchillas with heart murmurs.