bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Water Injectivity Model and Experimental Validation using CT Scanned Core-floods
Authors: Yerramilli Ramesh Chandra , Zitha P. L. , Yerramilli Sanjay Surya , Bedrikovetsky Pavel 
Published: June 2013

Abstract
Injectivity decline is an issue during Produced Water Re-Injection (PWRI) for water disposal in aquifers, water flooding, chemical EOR and geothermal energy exploitation. A novel model for injectivity decline under flow conditions reminiscent of Produced Water Re-Injection (PWRI) was developed taking into account deep-bed filtration and build-up of external filter cake. A distinct feature of the model is that it describes particle retention kinetics responsible for internal filtration by an exponential decaying function of the retained particle concentration. The corresponding non-linear governing partial differential equations were solved numerically and coupled with a known analytical model for external filtration using the concept of transition time. Core-flood experiments consisting of the injection of brine containing suspended hematite particles (volume fractions in the range 1–5 ppm) were also performed. CT scans of the core were done to obtain deposition profiles along the core at different times. Effect of various parameters (particle concentration, number of grids) on injecitivty was investigated. From CT scans, Scanning Electron Microscopic (SEM) analyses and optical microscopy photographs, it was found that surface deposition in the porous medium and face plugging at the inlet of the core were responsible for decline in injectivity. A transition time from pure internal filtration and external filtration was accurately determined from the CT scan and pressure data. Newly proposed model and experiments were found to be in excellent agreement indicating that the adopted retention function is good heuristic description of particle retention.
Iron Sulfide Removal: A Nonacidic Alternative to Hydrochloric Acid Treatment
Authors: Wang Xiaolan , Qu Qi , Berry Sandra , Cutler Jennifer 
Published: June 2013

Abstract
Iron sulfide scale deposition is a common problem in sour oil and gas wells. Accumulation of iron sulfide in the production tubing causes reduction of well deliverability. Conventional chemical means to remove Iron sulfide scale usually involve hydrochloric acid and other mineral acids. The composition and crystalline structure of iron sulfide scales varies significantly. Although iron disulfide (FeS2), which is found in the minerals such as marcasite and pyrite, is not soluble in acid, pyrrhotite (Fe7S8) has a high solubility in hydrochloric acid. Therefore, although hydrochloric acid and other acids can be applied to remove iron sulfide scales, their effectiveness in different treatments could be quite different depending on the scale composition. Even in cases where hydrochloric acid could be applied for iron sulfide removal, the applied hydrochloric acid is very corrosive to downhole tubulars especially at high temperatures and high acid concentrations. In the meantime, the generated H2S poses a great threat because of its high toxicity and enhanced corrosion tendency due to the combination of hydrochloride acid and H2S.
To overcome the drawbacks of hydrochloric acid treatment, i.e., the risk of H2S evolution and the corrosion tendency in standard carbon steel, an alternative chemical treatment to hydrochloric acid treatment is preferred. This paper illustrates the development of a new chemical treatment solution for iron sulfide removal. This polymer-based system demonstrated high dissolving capacity for iron sulfide scales in neutral or nearly neutral pH environments. Testing related to its performance also has revealed advantages such as low corrosion rate, and low H2S evolution. Additionally, laboratory testing demonstrated this polymer-based system is an effective general purpose stimulation fluid to stimulate carbonate and dolomite formations.
Field Wide Implementation of Proppant-Based Scale Control Technology in the Bakken Field
Authors: Kalfayan Leonard J. , McAfee Clyde A. , Cenegy Lawrence M. 
Published: June 2013

Abstract
Bakken well activity and oil production has increased dramatically in recent years, largely because of technological advancements in drilling, completion, and hydraulic fracturing. For one North Dakota operator experiencing downhole calcium carbonate scaling in the pump and production tubing, an innovative inhibition program has been implemented and shown to reduce well scaling frequency. The new scale inhibition program utilizes a solid proppant-based additive from which the scale inhibitor gradually desorbs. With expansion of the development into new fields which exhibit lower scaling risk, the scale inhibition program was then limited to the higher scaling risk fields, reducing cost and simplifying operations.
Bakken wells are completed to vertical depths of approximately 10,000 feet with horizontal laterals up to 10,000 feet and produced via multi-zone completions. The operator initially applied high concentrations of liquid scale inhibitor as an additive to fracturing fluid; nevertheless scaling remained a recurring problem. A postmortem of the failed wells was conducted to eliminate failures not directly attributable to calcium carbonate scale and to identify the factors affecting the scale deposition. The postmortem considered the method of hydraulic fracturing, pump intake pressure, scale inhibitor residual, calcium carbonate scaling index, geographic failure concentration, production time to failure, and cumulative water production to failure. Results of this study are detailed in paper SPE 140977 (Cenegy et al. 2011).
This paper continues the study and describes the subsequent scale management program initiated. It details the technology implemented and results in effecting downhole failures due primarily to scale. The paper additionally discusses the solid scale inhibitor technology selection, the inhibitor placement process and the steps taken to further optimize and manage costs of the field-wide Bakken scale inhibition program.
A Heuristic Production Model for Cyclic Steam Stimulation in a Fractured Heavy Oil Carbonate Reservoir
Authors: Qin Kent , MacDonald Jeff 
Published: June 2013

AbstractThe Upper Devonian Grosmont formation is considered to be Canada's next largest unconventional oil resource play, with an estimated 406 billion barrels of heavy oil in place. A number of production pilots targeting the Grosmont formation have tested various thermal enhanced oil recovery techniques, which include steam flood, combustion, and cyclic steam stimulation (CSS). To date, the CSS process has demonstrated considerable promise based on performance from the Unocal Buffalo Creek Phase 2 pilot and through the application of C-SAGD, a CSS variant designed for the Grosmont, at the Laricina-Osum joint-venture pilot in Saleski. While the methodologies for forecasting CSS production profiles are well understood for clastic oil sands reservoirs, no direct analogue exists for carbonate reservoirs such as the Grosmont. The current profiling model for clastics appears to be suitable for matching and forecasting the production characteristics of CSS and the early cycles of C-SAGD in the Grosmont. However, a few extensions to the current profiling models are required to address differences in cycle length, bitumen ramp up, and oil cut characteristics. For instance, oil cuts are typically low initially and increase with time for the majority of cycles in clastic oil sands, whereas in the Grosmont, there is observed cycle-to-cycle variability. The first few cycles typically show high initial oil cuts, decreasing with time; in subsequent cycles, the oil cuts behave similarly to clastic reservoirs. These differences can be attributed to the presence of secondary porosity and permeability systems in the carbonate formation, such as vugs and fracture networks, and their interactions with the matrix. This paper will describe the modification to existing models for profiling production, based on field observations from the aforementioned pilots.
Implementing Swellable Packer Technology for Well Intervention in Steam Recovery Operations
Authors: Takhodinov S. F. , Ibragimov N. G. , Mitchell R. K. , Davis T. , Greenan I. 
Published: June 2013

Abstract
In the Tatarstan Republic of Russia approximately 1000km southeast of Moscow, there are large deposits of bitumen and heavy oil. These wells are shallow in heavy oil reservoirs with 100 meters TVD. A process similar to SAGD operations is used; however there are also some specialty injector/producer wells with two well heads, one vertical, and a slant at 45 degrees. Through the bitumen layer filters or screens are deployed at the top of the bitumen layer on each side a stage tool is installed with casing back to surface. It was determined from temperature surveys and observation wells that the stage tool in well Ashalchinskoye 241 was leaking on the slant side, potentially creating a surface event. The stage tool leak needed to be plugged off and eliminated.
The proposed solution was to pump thermally stable cement with accelerator in two stages to assist in zonal isolation across the stage tool. To prevent cement from falling down to the screens or filters downhole, an inflatable bridge plug (figure 5) was required to be set below the stage tool.. It was also decided to use a steam injection swellable packer set across the stage tool to provide additional assurance the leak was eliminated. After the cement was drilled out, the swell packer was run across the stage tool and allowed to swell for two days. Once confirmed it was anchored, the work string was retrieved by actuating the HR which is a hydraulic release tool that can be functioned with or without dropping a ball (see figure 4) and the inflatable plug retrieved.
The value created was in re-establishing well integrity, and made it possible to pump steam down both well heads, making steam injection more efficient, allowing maximized production. The well was returned to production and has been successfully operated for three years now.
Auditor Choice and Audit Fees in Family Firms: Evidence from the S&P 1500
Authors: Ho Joanna L. , Kang Fei 
Published: June 2013

SUMMARY
We examine auditor choice and audit fees in family firms using data from Standard & Poor's (S&P) 1500 firms. We find that, compared to non-family firms, family firms are less likely to hire top-tier auditors due to the less severe agency problems between owners and managers. Our results also show that family firms, on average, incur lower audit fees than non-family firms, which is driven by family firms' lower demand for external auditing services and auditors' perceived lower audit risk for family firms. Our additional analysis indicates that the tendency of family firms to hire non-top-tier auditors and to pay lower audit fees is stronger when family owners actively monitor their firms.
Comorbid Diabetes and COPD
Authors: Caughey Gillian E. , Preiss Adrian K. , Vitry Agnes I. , Gilbert Andrew L. , Roughead Elizabeth E. 
Published: June 2013

OBJECTIVETo identify if there is a dose-dependent risk of diabetes complications in patients treated with corticosteroids who have both diabetes and chronic obstructive pulmonary disorder (COPD).RESEARCH DESIGN AND METHODSA retrospective study of administrative claims data from the Australian Government Department of Veterans’ Affairs, from 1 July 2001 to 30 June 2008, of diabetes patients newly initiated on metformin or sulfonylurea. COPD was identified by dispensings of tiotropium or ipratropium in the 6 months preceding study entry. Total corticosteroid use (inhaled and systemic) in the 12 months after study entry was determined. The outcome was time to hospitalization for a diabetes-related complication. Competing risks and Cox proportional hazard regression analyses were conducted with adjustment for a number of covariates.RESULTSA total of 18,226 subjects with diabetes were identified, of which 5.9% had COPD. Of those with COPD, 67.2% were dispensed corticosteroids in the 12 months from study entry. Stratification by dose of corticosteroids demonstrated a 94% increased likelihood of hospitalization for a diabetes complication for those who received a total defined daily dose (DDD) of corticosteroids ≥0.83/day (subhazard ratio 1.94 [95% CI 1.14–3.28], P = 0.014), by comparison with those who did not receive a corticosteroid. Lower doses of corticosteroid (&lt;0.83 DDD/day) were not associated with an increased risk of diabetes-related hospitalization.CONCLUSIONSIn patients with diabetes and COPD, an increased risk of diabetes-related hospitalizations was only evident with use of high doses of corticosteroids. This highlights the need for constant revision of corticosteroid dose in those with diabetes and COPD, to ensure that the minimally effective dose is used, together with review of appropriate response to therapy.
Insulin Resistance, Incident Cardiovascular Diseases, and Decreased Kidney Function Among Nondiabetic American Indians
Authors: Zhang Ying , Lee Elisa T. , Howard Barbara V. , Best Lyle G. , Umans Jason G. , Yeh Jeunliang , Wang Wenyu , Yeh Fawn , Ali Tauqeer , Devereux Richard B. , de Simone Giovanni 
Published: June 2013

OBJECTIVE
Prevalence of insulin resistance is high in the American Indian population, likely as a result of the high prevalence of obesity. This condition may be influential for clinical outcomes such as cardiovascular disease (CVD) and decreased kidney function.

RESEARCH DESIGN AND METHODS
Normal glucose tolerant (NGT) participants free of hypertension and CVD at the baseline examination (1989–1992) (N = 964) of the Strong Heart Study were selected to explore the cross-sectional association between insulin resistance quantified by homeostasis model assessment (HOMA-IR) and demographic, behavioral, and cardiometabolic variables. The longitudinal association between baseline HOMA-IR and the development of CVD was also explored. The longitudinal association between baseline HOMA-IR and the development of high urinary albumin-to-creatinine ratio was explored among nondiabetic participants (N = 1,401).

RESULTS
Cross-sectionally, HOMA-IR was associated with sex, residence location, smoking, and high-risk cardiometabolic profile. Prospectively, insulin resistance is associated with the development of CVD and decreased kidney function in this population.

CONCLUSIONS
Insulin resistance may have an important role in the pathogenesis of CVD and chronic kidney disease. Since obesity contributes to the development of insulin resistance, intervention focusing on modifiable factors such as physical activity and weight control may reduce the development of these diseases.
In Vitro Performance of Class I and II Composite Restorations: A Literature Review on Nondestructive Laboratory Trials—Part I
Authors: Dietschi D , Argente A , Krejci I , Mandikos M 
Published: June 2013

ABSTRACTPosterior adhesive restorations are a basic procedure in general dental practices, but their application remains poorly standardized as a result of the number of available options. An abundant number of study hypotheses corresponding to almost unlimited combinations of preparation techniques, adhesive procedures, restorative options, and materials have been described in the literature and submitted to various evaluation protocols. A literature review was thus conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review discusses the selected literature related to photoelasticity, finite element analysis (FEM), and microleakage protocols. Based on the aforementioned evaluation methods, the following parameters proved influential: cavity dimensions and design, activation mode (light or chemical), type of curing light, layering technique, and composite structure or physical characteristics. Photoelasticity has various limitations and has been largely (and advantageously) replaced by the FEM technique. The results of microleakage studies proved to be highly inconsistent, and the further use of this technique should be strictly limited. Other study protocols for adhesive Class II restorations were also reviewed and will be addressed in part II of this article, together with a tentative relevance hierarchy of selected in vitro methods.
Fractional Maximal Functions in Metric Measure
Spaces
Authors: Heikkinen Toni , Lehrbäck Juha , Nuutinen Juho , Tuominen Heli 
Published: June 2013

Abstract
We study the mapping properties of fractional maximal operators
in Sobolev and Campanato spaces in metric measure
spaces. We show that, under certain restrictions on the underlying
metric measure space, fractional maximal operators
improve the Sobolev regularity of functions and map functions
in Campanato spaces to Hölder continuous functions. We
also give an example of a space where fractional maximal
function of a Lipschitz function fails to be continuous.
Analysis of Immersed Interface Difference Schemes for Reaction-diffusion Problems with Singular Own Sources
Authors: Kandilarov Juri D. , Vulkov Lubin G. 
Published: June 2013

AbstractThis paper analyzes immersed interface difference schemes for onedimensional reaction-diffusion equations with singular own linear and nonlinear sources.
Error bounds in the infinity norm based on the maximum principle are derived. Sharper bounds and a more detailed structure of the error are obtained using the asymptotic
error expansion analysis method. Numerical examples confirm the theoretical results.
Monotone and Economical Difference Schemes on Nonuniform Grids for a Multidimensional Parabolic Equation with Third Kind
Authors: Matus Piotr , Martsynkevich Grigorii 
Published: June 2013

AbstractMonotone economical difference schemes of the second order of local
approximation with respect to space variables on nonuniform grids for the heat con-
duction equation with the boundary conditions of the third kind in a p-dimensional
parallelepiped are constructed. The a priori estimates of stability and convergence of
the difference solution in the norm C are obtained by means of the grid maximum
principle.
Solving Nonlinear Volterra | Fredholm Integro-differential Equations Using the Modified Adomian Decomposition Method
Authors: Araghi M. A. Fariborzi , Behzadi Sh. Sadigh 
Published: June 2013

AbstractIn this paper, a nonlinear Volterra | Fredholm integro-differential
equation is solved by using the modified Adomian decomposition method (MADM).
The approximate solution of this equation is calculated in the form of a series in which
its components are computed easily. The accuracy of the proposed numerical scheme
is examined by comparison with other analytical and numerical results. The existence,
uniqueness and convergence and an error bound of the proposed method are proved.
Some examples are presented to illustrate the efficiency and the performance of the
modified decomposition method.
Magma–sediment interaction during the emplacement of syn-sedimentary silicic and mafic intrusions and lavas into and onto Triassic strata (Circum-Rhodope Belt, northern Greece)
Authors: Asvesta Argyro , Dimitriadis Sarantis 
Published: June 2013

Abstract
Within the Circum-Rhodope Belt in northern Greece, Middle Triassic neritic carbonate metasediments are locally intercalated with quartz-feldspar-phyric metarhyolites. In the same belt, Upper Triassic pelagic lime-marl-layered metasediments are similarly intercalated with low-grade metamorphosed basalt, dolerite and minor andesite and trachydacite. We interpret these sequences as due to magmatism active during the rifting event that eventually led to the opening of the Vardar Ocean. Despite the overprint of Late Jurassic deformation and low greenschist metamorphism, peperitic textures produced by magma-wet sediment interaction are well preserved at the contacts between the silicic volcanic rocks and the originally wet unconsolidated neritic carbonate sediments, suggesting contemporaneous magmatism and sedimentation. The mafic and intermediate volcanic rocks lack peperitic textures at their contacts with the pelagic sedimentary rocks. Thin margin parallel banding in the sedimentary members of the sequence indicates thermally affected original contacts with the mafic volcanic rocks only locally and at a microscopic scale. The absence of peperite in this case is attributed to the consolidated state of the sediments at the time of the mafic magma emplacement.
Calpionellid distribution and microfacies across the Jurassic/ Cretaceous boundary in western Cuba (Sierra de los Órganos)
Authors: López-Martínez Rafael , Barragán Ricardo , Reháková Daniela , Cobiella-Reguera Jorge Luis 
Published: June 2013

Abstract
A detailed bed-by-bed sampled stratigraphic section of the Guasasa Formation in the Rancho San Vicente area of the “Sierra de los Órganos”, western Cuba, provides well-supported evidence about facies and calpionellid distribution across the Jurassic/Cretaceous boundary. These new data allowed the definition of an updated and sound calpionellid biozonation scheme for the section. In this scheme, the drowning event of a carbonate platform displayed by the facies of the San Vicente Member, the lowermost unit of the section, is dated as Late Tithonian, Boneti Subzone. The Jurassic/Cretaceous boundary was recognized within the facies of the overlying El Americano Member on the basis of the acme of Calpionella alpina Lorenz. The boundary is placed nearly six meters above the contact between the San Vicente and the El Americano Members, in a facies linked to a sea-level drop. The recorded calpionellid bioevents should allow correlations of the Cuban biozonation scheme herein proposed, with other previously published schemes from distant areas of the Tethyan Domain.
Organic-walled dinoflagellate cyst biostratigraphy of the Well Höflein 6 in the Cretaceous–Paleogene Rhenodanubian Flysch Zone (Vienna Basin, Austria)
Authors: Mohamed Omar , Wagreich Michael 
Published: June 2013

Abstract
Palynological analysis of the Rhenodanubian Flysch Zone section recovered from Well Höflein 6 north of Vienna allows the successful application of non-calcareous dinoflagellate biostratigraphy to the deep-water sediments of the Greifenstein Nappe. All 62 cuttings samples contained organic-walled dinoflagellate cysts (dinocysts) and some of them allow age-assessment. The results corroborated the presence of two thrust slices. The upper thrust unit A comprises a Campanian to Lower Eocene succession including, from old to young, the Röthenbach Subgroup, Perneck Formation, Altlengbach Formation and Greifenstein Formation. The lower thrust unit B contains in addition a pre- Campanian base, probably the Wolfpassing Formation of Early to mid-Cretaceous age.