bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Inflow Prediction Model for Open Hole Gravel Pack and Frac & Pack Completions
Authors: Tovar Juan J. , Moreno Ferney , Haider Syed R. 
Published: May 2009

Abstract
Predicting gravel pack performance is a complex and difficult task. Current practices account for expectation of performance by assigning a range of skin values that consider all the mechanisms that generate formation damage in the gravel pack. Other methods of identifying damage in the gravel pack include pressure build up analysis and the use of logging tools to investigate gravel placement. Using techniques such as NODAL® analysis, overall well performance can be validated and the level of damage within the gravel pack estimated. This practice assumes that other damaging mechanisms present at the sand face are part of the overall gravel pack damage.
This paper presents a methodology that integrates near wellbore damage, such as solid's invasion and mechanical damage during drilling, with damage caused to the gravel pack by solid particles as the well is started up for the first time. The model developed is supported by a laboratory test program of granular filter media to determine the various pore blocking mechanisms present during well start up. The results of this work indicate that impairment of the granular filter media is a function of flow rate, particle concentration and particle sizes. The final inflow model developed takes into account the volume of solids (mud cake and sand particles) that will be dragged into the gravel pack causing impairment. The result is an inflow profile from the gravel pack to the wellbore on a foot-by-foot basis that will dictate the final reservoir contribution and flow rates at the internal side of the screen.
Reactive Perforating: Conventional and Unconventional Applications, Learnings and Opportunities
Authors: Bell M. R. G. , Hardesty J. T. , Clark N. G. 
Published: May 2009

Abstract
A new class of shaped charge was introduced to the industry in late 2007 that generates a secondary reaction in the perforation tunnel immediately after it has been formed. The reaction is highly energetic and drives the break up and expulsion of crushed zone material and compacted debris. This profoundly alters the geometry and quality of the resulting tunnels when compared to conventional perforators and underbalanced perforating techniques. This leads to significant improvements in the percentage of open, effective tunnels, the productivity of the perforated interval, and the ease and reliability with which the perforated formation can be stimulated.
Since their launch, reactive perforating systems have been applied to a variety of well and formation types – both conventional and unconventional – under a wide range of pressure and effective stress conditions. As a result, the applicability of the reactive perforating concept is being demonstrated and accepted for an increasing number of situations. Nevertheless, the industry is only just beginning to understand how reactive perforating can be applied and how well and completion designs should be optimized to take full advantage of the benefits this new technology affords.
This paper describes the application of reactive perforators to a number of geographically and lithologically different situations, for the purpose of transferring generic learnings and identifying opportunities for further study. Several clear opportunity areas are already emerging, such as perforating prior to hydraulic fracturing – notably in unconventional gas plays – and re-perforation of depleted or damaged intervals. Other areas are still to be properly explored, such as perforation prior to acidization – especially in carbonates, perforation of unconsolidated sandstones, and perforation of injection wells.
In conclusion the paper identifies those areas where the technology has shown greatest success and summarizes the key learnings that will assist operators in shortening their own learning curve when applying reactive perforator technology.
Prevention of Production Breakdown Caused by Formate Drilling Fluid
Authors: Schulze Kai , Kersten Christoph , Verient Gery , Oswald Wolfgang , Dammerer-Kerbl Michael , Empl Christoph , Marchel Christian , Karsch Harold 
Published: May 2009

Abstract
The Rotliegend sandstone reservoir of Voelkersen (Northwest Germany) is a low permeability (kabs 2–4 mD), high pressure high temperature gas field (650 bar, 160°C). Its formation water is of high salinity (250 g/l) and characterised by its very high calcium content (≥ 40 g/l). The reservoir section of a partly depleted acceleration well was drilled using saturated water based sodium/potassium formate brine. For corrosion protection the pH value of the brine was adjusted to pH 10.5 using a bicarbonate/carbonate buffer. After gas production of 70 million m3(Vn) the production collapsed as a result of an unexpected build-up of calcium carbonate scale in the well bore area and the tubing. Two mechanisms have been identified as the cause of this scale formation. First the interaction of the caustic filtrate of the formate brine with the calcium rich formation water leading to a direct calcium carbonate precipitation. Second the enrichment of the formation water with bicarbonate by interaction with the caustic mud filtrate. This has resulted in calcium carbonate precipitation caused by the rise of the pH value of the water. The latter is resulting from decarbonisation caused by the pressure relief in the well bore area as a result of production. After subsequent mechanical and chemical scale removal, the gas production was even higher than at the initial state of production. However, having additionally produced 90 million m3(Vn) the production dropped again. This breakdown is attributable to an increase of bicarbonate in the formation water by a slow process of decomposition of formate left in the formation. This has resulted in subsequent scale formation following the decarbonisation process described above. To minimise the scaling potential of the formate brine while maintaining sufficient corrosion protection, careful adjustment of the pH value of the formate brine while drilling the reservoir section was implemented for successive wells. For already damaged wells several potential treatments have been identified and introduced, such as scale inhibition treatment integrated in hydraulic fracturing.
Analysis of Fracture Growth Induced by the Injection of Water Above the Fracture Pressure in Nonconsolidated Sandstones and Soft Carbonates – Deviations from the Linear Elastic Elastic Model or Why Can't I Inject Even Above the Fracture Pressure?
Authors: Pedroso Carlos Alberto , Marques Luiz Carlos do Carmo , Paixão Luiz Carlos Alves da , Pires Paulo Roberto da Motta , Luz Eurípedes Barsanulpho 
Published: May 2009

Abstract
The Injection Above the Fracture Pressure (IAFP) has became one of the most important alternatives to guarantee high injection rates, even when the quality of the injected water is below the minimum requirements for not damaging the rockreservoir. For this reason IAFP has found a vast application in both, the discard or re-injection of oily water or water with high solid content and to maintain the injectivity index of injector wells.
In Campos Basin, an interesting application of IAFP to assure the injection rate has been done in a pair of parallel horizontal wells completed with HOHGP (horizontal open hole gravel pack) in a Maastrichtian reservoir, where the fracture growth has been monitored through Hall Plots. In the first group (IAFP for water discard) some new projects have been planned, such as an "ecological well" (so called because the reduction of discard) which plan to inject large amount of water in dolomites.
All these projects were preceded by a fracture growth analysis. Usually, these analyses are carried-out by using simulators which are based in Linear Elastic Fracture Model theory (LEFM) and consider a single planar fracture. However, in the case of IAFP in non-consolidated sandstones or soft carbonates, these assumptions can be quite unrealistic. Effects of plastic deformation in the fracture tip, compacting or fluidization of porous media, multiple fractures and pore-elastic effects can be predominant in these cases.
An example that ratifies this was the attempt to re-inject produced water above the fracture pressure in an unconsolidated Miocene reservoir. Even with injection pressure 800 psi above the fracturing pressure (measured through a previous minifrac), it was impossible to propagate the fracture. In another well, the IAFP was aborted when a completely unexpected fracture gradient greater than 0.83 psi/ft was attained (it was expected 0.52 psi/ft). This behavior can only be explained if we consider the occurrence of any different phenomena of those foreseen by LEFM.
This work details the IAPF projects here mentioned and depicts the deviations of LEFM observed in IAFP wells in Campos’ Basin.
A Novel Timer Activated Sandface Valve to Improve Wellbore Productivity
Authors: Russell Leigh-Ann , Elliott Grahame , Graham John , Wallace Alex , Coull David , Forsyth David 
Published: May 2009

Abstract
A novel timer activated sandface valve was developed that has significant impact on wellbore productivity by enabling improved wellbore clean up, particularly in high angle and open hole completions. This technology has been field trialled and proven in three wells in a North Sea field. The tool was developed from concept to installation in less than nine months including detailed engineering review and assurance.
Negative impact to productivity due to inefficient wellbore clean up of high angle completions is a common situation for production wells. The current solution can be complex completion architecture or extensive clean up procedures that are both expensive and difficult to implement. The consequence of a poor clean up can be loss in well productivity, access to reserves or a requirement to sidetrack the well.
Poor clean up was observed in several wells in a North Sea field. The wells exhibited high skin and no flow from the toe sections of the well due to the dominance of high productive intervals subject to high drawdown at the heel of the well. The timer activated sand face valve was developed with the key objective to deliver sequential clean up from the toe of the reservoir section without intervention or incremental rig time. The valves also deliver the functionality of a sliding side door for future water shut-off capability along the well bore.
The paper will present an overview of the technical challenge, detail development of the tool and processes used for assurance and include results of the field trial. The valve development combines a field proven timer activation mechanism with conventional sliding sleeve technology. The tool was developed without incremental resource and cost often required for product development utilising specifically designed lean technical assurance tools and failure mode and effects analysis processes. The result is a successfully field proven completion tool that is the basis for a new completion technique that has application in high angle wells in all oilfield applications.
Models and Methods for Understanding of Early Acid Breakthrough Observed in Acid Core-floods of Vuggy Carbonates
Authors: Izgec O. , Zhu D. , Hill A. D. 
Published: May 2009

Abstract
Previously, we have studied the acidization of vuggy carbonates with acid core flood experiments in 4-inch diameter by 20-inch long cores, high resolution computerized tomography imaging, image processing and geostatistical characterization. The obvious major finding from these tests is that acid propagates wormholes through vuggy carbonates much more rapidly than occurs in more homogeneous rocks. Acid-created wormholes were observed to break through to the end of the cores an order of magnitude more rapidly than occurs in more homogeneous cores, highlighting the necessity of understanding the flow and transport in vuggy carbonates. The fact that acid channeled through the vugular cores, following the path of the vug system, was underlined with computerized tomography scans of the cores before and after acid injection. This observation proposes that local pressure drops created by vugs are more dominant in determining the wormhole flow path than the chemical reactions occurring at the pore level. Following this idea, we are presenting a modeling study in order to understand flow in porous media in the presence of vugs. Use of coupled Darcy and Stokes flow principles, known as the Darcy-Brinkman formulation, underpins the proposed approach. The power of the Darcy-Brinkman formulation lies in its natural ability to represent both porous media and tube flow in a single equation with variable coefficients.
The methods presented here shows that acid injected into vuggy limestones follows a preferential pathway guided by the vug network. The PVbt (pore volumes to break through) for vuggy limestone correlates inversely with the fraction of total porosity comprised by vugs – the higher the vuggy fraction of porosity, the lower the pore volumes to breakthrough. Local pressure drops created by vugs are more dominant in determining the wormhole flow path than the chemical reactions occurring at the pore level. The results from the developed model demonstrate that the total injection volume to breakthrough is affected by the spatial distribution, the amount and the connectivity of vuggy pore space.
Taking Advantage of Injectivity Decline for Sweep Enhancing during Waterflood with Horizontal Wells
Authors: Bedrikovetsky P. , Muhammad A. W. , Chang G. , de Souza A. L. S. , Furtado C. 
Published: May 2009

Abstract
Injectivity formation damage with waterflooding using sea/produced water has been widely reported in the North Sea, the Gulf of Mexico and the Campos Basin in Brazil. The damage is due to the capture of solid/liquid particles by the rock with consequent permeability decline; it is also due to the formation of a low permeable external filter cake. Yet, moderate injectivity decline is not too damaging with long horizontal injectors where the initial injectivity is high. In this case, injection of raw or poorly treated water would save money on water treatment, which is not only cumbersome but also an expensive procedure in offshore projects.
In this paper we investigate the effects of injected water quality on waterflooding using horizontal wells. It was found out that induced injectivity damage results in increased sweep efficiency. The explanation of the phenomenon is as follows: injectivity rate is distributed along a horizontal well non-uniformly; water advances faster from higher rate intervals resulting in early breakthrough; the retained particles plug mostly the high permeability channels and homogenize the injectivity profile along the well.
An analytical model for injectivity decline accounting for particle capture and a low permeable external filter cake formation has been implemented into the Eclipse 100 reservoir simulator. It is shown that sweep efficiency in a heterogeneous formation can increase by up to 5% after one pore volume injected, compared to ‘clean’ water injection.
Proinflammatory Cytokines Activate the Intrinsic Apoptotic Pathway in β-Cells
Authors: Grunnet Lars G. , Aikin Reid , Tonnesen Morten F. , Paraskevas Steven , Blaabjerg Lykke , Størling Joachim , Rosenberg Lawrence , Billestrup Nils , Maysinger Dusica , Mandrup-Poulsen Thomas 
Published: May 2009

OBJECTIVE
Proinflammatory cytokines are cytotoxic to β-cells and have been implicated in the pathogenesis of type 1 diabetes and islet graft failure. The importance of the intrinsic mitochondrial apoptotic pathway in cytokine-induced β-cell death is unclear. Here, cytokine activation of the intrinsic apoptotic pathway and the role of the two proapoptotic Bcl-2 proteins, Bad and Bax, were examined in β-cells.

RESEARCH DESIGN AND METHODS
Human and rat islets and INS-1 cells were exposed to a combination of proinflammatory cytokines (interleukin-1β, interferon-γ, and/or tumor necrosis factor-α). Activation of Bad was determined by Ser136 dephosphorylation, mitochondrial stress by changes in mitochondrial metabolic activity and cytochrome c release, downstream apoptotic signaling by activation of caspase-9 and -3, and DNA fragmentation. The inhibitors FK506 and V5 were used to investigate the role of Bad and Bax activation, respectively.

RESULTS
We found that proinflammatory cytokines induced calcineurin-dependent dephosphorylation of Bad Ser136, mitochondrial stress, cytochrome c release, activation of caspase-9 and -3, and DNA fragmentation. Inhibition of Bad Ser136 dephosphorylation or Bax was found to inhibit cytokine-induced intrinsic proapoptotic signaling.

CONCLUSIONS
Our findings demonstrate that the intrinsic mitochondrial apoptotic pathway contributes significantly to cytokine-induced β-cell death and suggest a functional role of calcineurin-mediated Bad Ser136 dephosphorylation and Bax activity in cytokine-induced apoptosis.
Prevalence and Predictors of Breast and Cervical Cancer Screening Among Spanish Women With Diabetes
Authors: Jiménez-Garcia Rodrigo , Hernandez-Barrera Valentin , Carrasco-Garrido Pilar , Gil Angel 
Published: May 2009

OBJECTIVE
To examine the use of mammography and Papanicolaou (Pap) smear among women with diabetes and to identify predictors of adherence to these tests.

RESEARCH DESIGN AND METHODS
We analyzed data of a nationally representative sample of Spanish women. Diabetes status was self-reported. Screenings were assessed asking whether they had a mammography (≥40 years) and a Pap smear (18–69 years) within the previous 2 and 3 years, respectively.

RESULTS
Women with diabetes were less likely to receive mammography (57.9%) or have a Pap smear (61.5%) than women without diabetes (mammography 61.9%, P &lt; 0.05; Pap smear 65.6%, P &lt; 0.05). After adjusting for age, educational level, income, comorbidity, tobacco use, obesity, and physician visits, the corresponding odds ratios remained significant (0.84, 95% CI 0.72–0.97) and (0.82, 95% CI 0.66–0.98). Higher educational level was a positive predictor for both tests among diabetic women.

CONCLUSIONS
Spanish women with diabetes underuse breast and cervical cancer screening tests.
∞-jets of diffeomorphisms preserving orbits of vector fields
Authors: Maksymenko Sergiy 
Published: May 2009

Abstract
Let F be a C
∞ vector field defined near the origin O ∈ ℝn, F(O) = 0, and (Ft) be its local flow. Denote by the set of germs of orbit preserving diffeomorphisms h: ℝn → ℝn at O, and let , (r ≥ 0), be the identity component of with respect to the weak Whitney Wr topology. Then contains a subset consisting of maps of the form Fα(x)(x), where α: ℝn → ℝ runs over the space of all smooth germs at O. It was proved earlier by the author that if F is a linear vector field, then = .
In this paper we present a class of examples of vector fields with degenerate singularities at O for which
formally coincides with , i.e. on the level of ∞-jets at O.
We also establish parameter rigidity of linear vector fields and “reduced” Hamiltonian vector fields of real homogeneous polynomials in two variables.
On oscillation and nonoscillation properties of Emden-Fowler difference equations
Authors: Cecchi Mariella , Došlá Zuzana , Marini Mauro 
Published: May 2009

Abstract
A characterization of oscillation and nonoscillation of the Emden-Fowler difference equation $$
\Delta (a_n \left| {\Delta x_n } \right|^\alpha sgn\Delta x_n ) + b_n \left| {x_{n + 1} } \right|^\beta sgnx_{n + 1} = 0
$$ is given, jointly with some asymptotic properties. The problem of the coexistence of all possible types of nonoscillatory solutions is also considered and a comparison with recent analogous results, stated in the half-linear case, is made.
On the Drazin index of regular elements
Authors: Patrício Pedro , Costa António 
Published: May 2009

Abstract
It is known that the existence of the group inverse a
# of a ring element a is equivalent to the invertibility of a
2
a
− + 1 − aa
−, independently of the choice of the von Neumann inverse a
− of a. In this paper, we relate the Drazin index of a to the Drazin index of a
2
a
− + 1 − aa
−. We give an alternative characterization when considering matrices over an algebraically closed field. We close with some questions and remarks.
Wahl’s conjecture holds in odd characteristics for symplectic and orthogonal Grassmannians
Authors: Lakshmibai Venkatramani , Raghavan Komaranapuram , Sankaran Parameswaran 
Published: May 2009

Abstract
It is shown that the proof by Mehta and Parameswaran of Wahl’s conjecture for Grassmannians in positive odd characteristics also works for symplectic and orthogonal Grassmannians.
Sarcoidosis of the Thyroid Gland and Concomitant Hürthle Cell Adenoma: Case Report
Authors: Stojanoski Siniša , Gjorceva Daniela , Gruev Todor , Ristevska Svetlana , Ristevska Nevena , Tripunovski Toni 
Published: May 2009

Sarcoidosis of the Thyroid Gland and Concomitant Hürthle Cell Adenoma: Case Report
Sarcoidosis is a multisystem disorder, characterized by the presence of noncaseating epithelioid-cell granulomas. The etiology remains unclear, although it is recognized as a disease of activated T lymphocytes. There is a diverse range of possible presentations with respiratory, gastrointestinal, reproductive, endocrine and other complications. The thyroid is an uncommon site of the disease with only 4% incidence according to some autopsy series. We present a case of a 55-year-old female patient with sarcoidosis of the thyroid gland and concomitant Hürthle cell adenoma. Upon performing a routine thyroid scintigraphy, a cold nodule has been observed. The diagnosis of the underlying disease was established by correlating the anamnesis data, patient's clinical history, fine needle aspiration biopsy and pathological examination of the thyroidectomy specimen. To our knowledge, the association has rarely been previously reported, indicating that thyroid involvement should be suspected in sarcoidosis patients who present with cold nodules.
Thrombosis of difficult intracranial aneurysms by the endovascular placement of platinum-Dacron microcoils
Authors: Knuckey Neville W. , Haas Richard , Jenkins Ross , Epstein Mel H. 
Published: May 2009

✓ Patients with symptomatic aneurysms that are not excluded from the cerebral circulation have a poor prognosis. Standard treatment is surgical exploration with direct clipping of the aneurysm. Because of their large size or relationship to the base of the skull, some aneurysms may not be suitable for direct surgical clipping and may require alternative treatment modalities. A prospective clinical and radiological study of seven patients treated with the endovascular placement of platinum-Dacron microcoils to exclude the aneurysm from the cerebral circulation is reported.
The seven patients ranged in age from 37 to 63 years; four were women. At completion of the endovascular procedure, total occlusion of the aneurysm with preservation of the parent artery had been achieved in four patients and 90% occlusion of the aneurysm in two. In the seventh patient, occlusion of the internal carotid artery resulted in the patient's death. At the 6-month follow-up review, both patients with an aneurysm less than 20 mm in size had persistent aneurysm thrombosis; however, the two patients with giant aneurysms had partial recanalization. Both required repeat thrombosis of their aneurysm with the placement of additional microcoils, one at 6 weeks and one at 6 months. These two patients have persistent aneurysm thrombosis at 12 months following their second procedure. The patient mortality rate for this study was 14%, while the procedure mortality/morbidity rate was 9%. It is concluded that thrombotic aneurysm therapy of difficult aneurysms is a safe procedure and will have a place in the treatment of selected aneurysms.