bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acid Fracturing: The Effect of Formation Strength on Fracture Conductivity
Authors: Gomaa A. M. , Nasr-El-Din H. A. 
Published: January 2009

Abstract
A few studies considered the role of rock strength on fracture conductivity retained at elevated closure strengths. Based on experimental results and field data, many correlations were derived with a consideration of both the surface roughness and rock mechanical properties. These studies found that acid fracture conductivity is sometimes lower with longer acid contact times than with shorter ones. This is apparently the result of the weakening of the rock structure along the face of the fracture with increased acid exposure, such that the conductivity decreases more rapidly with increasing the closure stress.
Based on extensive literature survey of three types of carbonate rocks, it was found that chalk has the lowest rock embedment strength and the fractures closed at much lower stresses compared with limestone or dolomite. Dolomite has the highest rock embedment strength and best conductivity results compared with other rocks tested.
A sensitivity analysis was performed to determine the effect of rock embedment strength, and dissolved rock equivalent conductivity on the fracture conductivity. The results of this analysis showed that dissolved rock equivalent conductivity determines the maximum conductivity at a closure stress equal to zero, while the value of rock embedment strength determines the decline in conductivity with increasing the closure stress. This analysis shows that the value of dissolved rock embedment conductivity doesn't affect the difference that exists in some of the developed correlations, while the value of rock equivalent strength has a significant impact on this difference. Finally, the rock embedment strength is a key parameter that affects the fracture conductivity. This paper discusses current correlations to predict fracture conductivity, and addresses the influences of several key parameters on the fracture conductivity.
Successful Optimization of Viscoelastic Foamed Fracturing Fluids with Ultra-Lightweight Proppants for Ultra Low Permeability Reservoirs
Authors: Cawiezel Kay E. , Gupta D. V. S. 
Published: January 2009

Abstract
Successful fracturing treatments in ultra low permeability reservoirs require combining the most recent innovations in fracturing technologies. Viscoelastic surfactants, foams and ultra lightweight proppants have specific properties that when combined offer the unique performance required by the demands of fracturing these reservoirs. Inexpensive, logistically simple, polymer-free viscoelastic surfactants provide exceptionally high viscosity under low shear conditions required for proppant transport. They also provide excellent cleanup characteristics. Foamed viscoelastic surfactants provide increased viscosity for frac width, better leak off control and further improve fluid cleanup characteristics, particularly in low pressure reservoirs. Ultra-lightweight proppants provide excellent transport properties in conventional fracturing fluids with minimal viscosity, which ensures desired effective propped fracture conductivity. Utilization of these revolutionary ultra lightweight proppants in foamed viscoelastic fluids provides fracturing treatments with optimum proppant placement and excellent cleanup. As with all successfully applied fracturing fluids the fluid systems must be optimized. These combined systems require significant laboratory testing to successfully characterize and optimize the fluid system for the demands of ultra low permeability reservoirs. This paper focuses on small and large scale laboratory testing performed to optimize these viscoelastic-foamed systems in an effort to test the technical limit of this new technology for future field developments.
Simultaneous Hydraulic Fracturing of Adjacent Horizontal Wells in the Woodford Shale
Authors: Waters George , Dean Barry , Downie Robert , Kerrihard Ken , Austbo Lance , McPherson Bruce 
Published: January 2009

Abstract
Hydraulic fracturing of horizontal wells in shale gas reservoirs is now an established, commercially successful technique. The evolution of the completion technique has reached the point that numerous stimulation stages through multiple perforation clusters in wellbores with some form of annular isolation is now an accepted practice. The objective is to place multiple closely spaced hydraulic fractures. This has proven to be a viable development strategy for many shale reservoirs in North America.
To further enhance the recovery factor in these ultra low permeability reservoirs simultaneously hydraulically fracturing of adjacent wellbore is increasingly being tested. Most of the time this is performed in horizontal wellbores paralleling each other. The goal is to create hydraulic fractures more closely spaced than can be achieved from a single wellbore. When real time microseismic monitoring of the stimulation treatments is incorporated changes can be made "On-the-Fly" to improve the effective stimulated reservoir volume.
Continental Resources has employed simultaneous hydraulic fracturing as a development strategy for their Woodford Shale acreage in the Arkoma Basin of Eastern Oklahoma. To monitor the effectiveness of the stimulations geophones have been deployed into horizontal wellbores to record microseismic events when offsetting vertical wellbores are unavailable. Cased hole sonic logs have also been run to quantify cement bond quality, estimate stress variation along the lateral, and to pick optimum perforating points.
This paper reviews the methodology employed in the completion design and process. The impact of the simultaneous stimulations and geologic structure on the fracture geometry are shown as well as the impact on well productivity.
Modeling Simultaneous Growth of Multiple Hydraulic Fractures and Their Interaction With Natural Fractures
Authors: Olson Jon E. , Dahi-Taleghani Arash 
Published: January 2009

Abstract
Hydraulic fracture diagnostics have highlighted the potentially complex natural of hydraulic fracture geometry and propagation. This has been particularly true in the cases of hydraulic fracture growth in naturally fractured reservoirs, where the induced fractures interact with pre-existing natural fractures. A simplified numerical model has been developed to account for mechanical interaction between pressurized fractures, and to examine the simultaneous propagation of multiple (&gt;2) hydraulic fracture segments. Fracture intersection is presumed to communicate the hydraulic fracturing fluid to the natural fracture, which then takes up the continued propagation. Simulations for multi-stage horizontal well treatments and single stage vertical well treatments show that fracture pattern complexity is strongly controlled by the magnitude of the hydraulic fracture net pressure relative to the in situ horizontal differential stress as well as the geometry of the natural fractures. Analysis of the neartip stress field around a hydraulic fracture also indicates that induced stresses may be high enough to debond sealed natural fractures ahead of the arrival of the hydraulic fracture tip.
Surface Etching Pattern and its Effect on Fracture Conductivity in Acid Fracturing
Authors: Antelo Luis Fernando , Pournik M. , Zhu D. , Hill A. D. 
Published: January 2009

Abstract
Conductivity in acid fracturing after fracture closure depends on the contact of the non-uniformly etched fracture surfaces created by the acid. The surface topography of the fracture faces after acid injection is rarely investigated and, therefore, poorly described. The concept of average fracture width has been used in the fracture conductivity models to predict fracture conductivity in acid fracturing. Previous study showed that the characterization of fracture faces after acid etching plays an important role in fracture conductivity. If channels and wormholes are created, fracture conductivity cannot be described by the conventional model. For more evenly distributed etching, surface topography characteristic strongly influences the resulting conductivity. With a surface profilometer, a laser device that accurately measures the height of the asperities on the rock surface, we obtain a digital image that can be used to quantitatively characterize the etched surface topography after acidizing. Using this data we are able to define the channel geometry and etching patterns as numerical values. The distribution of these numerical values is later converted and analyzed as surface texture parameters and standard statistical variables for rough surface characterization. When two roughness parameters of each corresponding fracture surface are superposed, the fracture conductivity can be related to the statistical parameters of etching.
In this paper we present experimental results for a wide range of acid fracturing conditions that provide the variables and controlling parameters relating roughness of the fractures surface to fracture conductivity measurements. The findings of this study is important to understanding the effect of etcing pattern of fracture face on fracture conductivity behavior, and it also helps to develop lab scale fracture conductivity correlations in acid fracturing.
Method and Apparatus for Simultaneous Stimulation of Multi-Well Pads
Authors: Tolman R. C. , Simons J. W. , Petrie D. H. , Nygaard K. J. , Clingman S. R. , Farah A. M. 
Published: January 2009

Abstract
Progressively, the oil and gas industry is producing from unconventional reservoirs with low permeability in numerous small pay zones that require close well spacing and multiple stimulations in each well. To effectively produce from such reservoirs and reduce the surface footprint, ExxonMobil has drilled multiple wells from single pads, and new technologies have been developed to efficiently stimulate the multiple pay zones in each well.
ExxonMobil has developed and licensed Multi-Zone Stimulation Technologies (MZST), which are designed to efficiently stimulate wells with multiple pays zones. The technologies have been applied in fracturing tight gas reservoirs with numerous lenticular sands in the Rocky Mountains. We have also developed a technology that enables the simultaneous stimulation of multiple wells on the same or different well pads, and while drilling additional wells. The benefits of this technology include reduced environmental impact, time saving, and improved production rates. Most importantly we have demonstrated that these simultaneous operations can be conducted in a safe and responsible manner to ensure the highest standards of operations integrity.
This paper introduces the method and apparatus for this technology and discusses the results from several years of field applications, including the Piceance Basin. Some specific elements of the simultaneous operations safety plan will also be provided.
Residential water demand under block rates – a Portuguese case study
Authors: Martins Rita , Fortunato Adelino 
Published: January 2009

A residential water demand equation is estimated using a panel data sample of five Portuguese local communities and 72 months, corresponding to a total number of 360 observations. Because of the presence of multi-part tariffs, we use the two common price-related variables: marginal price and difference as explanatory variables. To prevent the simultaneity bias from using observed quantities to determine the values of marginal price and difference directly from the rate schedule, we use an instrumental variable approach to create a constant marginal price and difference parameters for each rate structure.
The price elasticity values obtained fall within the range of those found in other case studies. Thus, although presenting weak elasticity, price seems to play a role in water demand management. However, we do not confirm the expected influence of difference on residential water demand. This can be a consequence of the complexity of the Portuguese water tariffs and the confusing signs that come from the simultaneous use of fixed quotas and increasing block tariffs. So, it is imperative to clarify water tariffs objectives by reviewing the Portuguese water tariffs design processes.
PPP – policies, practices and problems in Ghana's urban water supply
Authors: Fuest Veronika , Haffner Stefan A. 
Published: January 2009

Since the beginning of the 1990s, comprehensive reforms of the Ghanaian water sector were initiated by the Bretton Woods Institutions. The Government of Ghana was obliged to restructure the sector by establishing regulatory bodies, opening the sector to private sector participation and separating responsibilities for urban water supply from rural water supply. The parastatal Ghana Water Company Limited (GWCL) was created to be solely in charge of urban water supply. In spite of external assistance, GWCL continued to suffer from massive financial, managerial and technical problems. The gap between supply and demand increased while demand for potable water in the cities was on the rise and the supply systems were degenerating.
In order to introduce greater efficiency, two options for public–private partnerships (PPP) were developed and contested, over a period of 10 years. At first private companies were invited to take over the GWCL by a lease contract. Numerous factors, among them a massive anti-privatisation campaign and global economic trends unfavourable to private investment, particularly in the water sector, caused a comprehensive revision of the policy and the modification of the PPP programme from lease to short-term management contract with an ensuing affermage concession in 2004. This process was to be supported by external donor agencies substantially upgrading the water supply infrastructure. However, it seemed doubtful if the recent policy would lead to a sustainable system of urban water supply and substantial improvements in the supply situation of the poor. Patronage relations were not sufficiently addressed and alternative PPP options based on local potential had not been considered. The case of Ghana raises issues of imposed PPP policies that are not based on adequate information about local, national and international framework conditions.
Virtual Instrumentation Based Active Fin Control for Roll Stabilization
Authors: Subramanian V Anantha , Asokumar G , Mohamed Thaju 
Published: January 2009

The objective of this work is to develop a non-traditional strategy for providing control of ship roll motion in a seaway using active fins. This is based on a multidisciplinary approach. It consists of the assessment of the hydrodynamic coefficients of a ship using a numerical package [SEDOS], representation of the hydrodynamic coefficients by suitable polynomial functions, identification of the time dependent fundamental frequency in the roll disturbance signal sample, generation of control signal for an appropriate fin angle based on the fin lift characteristics of the chosen fin and employment of feedback control to maintain the fin at the appropriate angle for maximum control. Once the ship based hydrodynamic coefficients are generated, the entire control algorithm is developed in the virtual instrumentation mode using LabVIEW environment. One of the disadvantages of the traditional stabilizer system is the enormous hardware involved in the controllers and instrumentation panels, which makes maintenance and troubleshooting difficult. With the help of virtual instrumentation, design of the stabilization controller and instrumentation panels can be carried out much more effectively, in comparison with the traditional hardware approach. Key words: Roll stabilization, Active fin control, Virtual instrumentation doi:10.3329/jname.v2i2.1869 Â Journal of Naval Architecture and Marine Engineering 2(2005) 11-24
Balancing role of nitric oxide in complement‐mediated activation of platelets frommCd59aandmCd59bdouble‐knockout mice
Authors: Qin Xuebin , Hu Weiguo , Song Wenping , Blair Price , Wu Gongxiong , Hu Xuemei , Song Yanli , Bauer Selena , Feelisch Martin , Leopold Jane A. , Loscalzo Joseph , Halperin Jose A. 
Published: January 2009

AbstractCD59 is a membrane protein inhibitor of the membrane attack complex (MAC) of complement.mCd59knockout mice reportedly exhibit hemolytic anemia and platelet activation. This phenotype is comparable to the human hemolytic anemia known as paroxysmal nocturnal hemoglobinuria (PNH), in which platelet activation and thrombosis play a critical pathogenic role. It has long been suspected but not formally demonstrated that both complement and nitric oxide (NO) contribute to PNH thrombosis. UsingmCd59aandmCd59bdouble knockout mice (mCd59ab−/−mice) in complement sufficient (C3+/+) and deficient (C3−/−) backgrounds, we document thatmCd59ab−/−platelets are sensitive to complement‐mediated activation and provide evidence for possible in vivo platelet activation inmCd59ab−/−mice. Using a combination of L‐NAME (a NO‐synthase inhibitor) and NOC‐18 or SNAP (NO‐donors), we further demonstrate that NO regulates complement‐mediated activation of platelets. These results indicate that the thrombotic diathesis of PNH patients could be due to a combination of increased complement‐mediated platelet activation and reduced NO‐bioavailability as a consequence of hemolysis. Am. J. Hematol. 2009. © 2009 Wiley‐Liss, Inc.
A randomized controlled trial evaluating an alternative mouse or forearm support on change in median and ulnar nerve motor latency at the wrist
Authors: Conlon Craig F. , Krause Niklas , Rempel David M. 
Published: January 2009

AbstractBackgroundThe purpose of this study was to determine the effects of an alternative mouse and/or a forearm support board on nerve function at the wrist among engineers.MethodsThis randomized controlled intervention trial followed 206 engineers for 1 year. Distal motor latency (DML) at baseline and follow‐up was conducted for the median and ulnar nerves at the right wrist.ResultsOne hundred fifty‐four subjects agreed to a nerve conduction study at the beginning and end of the study period. Those who received the alternative mouse had a protective effect (OR = 0.47, 95% CI 0.22–0.98) on change in the right ulnar DML. There was no significant effect on the median nerve DML. The forearm support board had no significant effect on the median or ulnar nerve DML.ConclusionsIn engineers who use a computer for more than 20 hr per week, an alternative mouse may have a protective effect for ulnar nerve function at the wrist. No protective effect of a forearm support board was found for the median nerve. Am. J. Ind. Med. 52:304–310, 2009. © 2009 Wiley‐Liss, Inc.
Mesothelioma in a worker who spun chrysotile asbestos at home during childhood
Authors: Yano Eiji , Wang Zhi‐Ming , Wang Xiao‐Rong , Wang Mian‐Zheng , Takata Ayako , Kohyama Norihiko , Suzuki Yasunosuke 
Published: January 2009

AbstractBackgroundMalignant mesothelioma has a long latency period and more commonly found in those exposed to amphibole than chrysotile asbestos.MethodA 35 years old asbestos worker in an asbestos textile plant in Chongqing, China, developed mesothelioma after only 4 years of employment. He was born and bred in a company residence of an asbestos plant and manually spun asbestos thread during school age. In the plant, not amphibole but only chrysotile has been used.ResultsDiagnosis of malignant mesothelioma was confirmed by comprehensive approaches including gross appearance, histology, histochemistry, and immunocytochemistry. In the lung and tumor tissues, huge number of tremolite with exceptional chrysotile was observed despite the reverse proportion in the work environment.DiscussionResidential exposure and home spinning of asbestos seemed contributed to the early development of mesothelioma in this subject. Although only chrysotile was used and contamination of tremolite was low in the work environment, chrysotile seemed to be cleared leaving tremolite remain in the tissue.ConclusionChrysotile with little contamination of tremolite can lead to early development of malignant mesothelioma when heavily exposed from childhood at a company residence with household exposure. There can be several mechanisms for tremolite to remain in the lung tissue, far exceeding chrysotile in number. Am. J. Ind. Med. 52:282–287, 2009. © 2009 Wiley‐Liss, Inc.
A scoring system for coat and tail condition in ringtailed lemurs, Lemur catta
Authors: Berg Wiebke , Jolly Alison , Rambeloarivony Hajarimanitra , Andrianome Vonjy , Rasamimanana Hantanirina 
Published: January 2009

AbstractCoat condition can be influenced by a wide variety of disorders and thus provides a useful tool for noninvasive health and welfare assessments in wild and captive animals. Using Lemur catta as an exemplar, we offer a 6‐step scoring system for coat and tail condition, ranging from perfectly fluffy to half or more of body and tail being hairless. The categories are described in detail and illustrated with sample pictures from a wild population in Berenty Reserve, Madagascar. Furthermore, we elaborate on intermediate conditions and discoloration of fur. Coat condition scoring allows the comparison between years, seasons, and the effect of toxin, disease or stress. Although this system was developed for wild L. catta, we believe it can also be of value for other species. We recommend scoring coat condition in healthy wild mammal populations to give a baseline on yearly and seasonal variations vs. deteriorating health conditions or pathology. Am. J. Primatol. 71:183–190, 2009. © 2009 Wiley‐Liss, Inc.
Folinic acid–responsive seizures are identical to pyridoxine‐dependent epilepsy
Authors: Gallagher Renata C. , Van Hove Johan L. K. , Scharer Gunter , Hyland Keith , Plecko Barbara , Waters Paula J. , Mercimek‐Mahmutoglu Saadet , Stockler‐Ipsiroglu Sylvia , Salomons Gajja S. , Rosenberg Efraim H. , Struys Eduard A. , Jakobs Cornelis 
Published: January 2009

AbstractObjectiveFolinic acid–responsive seizures and pyridoxine‐dependent epilepsy are two treatable causes of neonatal epileptic encephalopathy. The former is diagnosed by characteristic peaks on cerebrospinal fluid (CSF) monoamine metabolite analysis; its genetic basis has remained elusive. The latter is due to α‐aminoadipic semialdehyde (α‐AASA) dehydrogenase deficiency, associated with pathogenic mutations in the ALDH7A1 (antiquitin) gene. We report two patients whose CSF showed the marker of folinic acid–responsive seizures, but who responded clinically to pyridoxine. We performed genetic and biochemical testing of samples from these patients, and seven others, to determine the relation between these two disorders.MethodsCSF samples were analyzed for the presence of α‐AASA and pipecolic acid. DNA sequencing of the ALDH7A1 gene was performed.ResultsBoth patients reported here had increased CSF α‐AASA, CSF pipecolic acid, and known or likely pathogenic mutations in the ALDH7A1 gene, consistent with α‐AASA dehydrogenase deficiency. Analysis of CSF samples from seven other anonymous individuals diagnosed with folinic acid–responsive seizures showed similar results.InterpretationThese results demonstrate that folinic acid–responsive seizures are due to α‐AASA dehydrogenase deficiency and mutations in the ALDH7A1 gene. Thus, folinic acid–responsive seizures are identical to the major form of pyridoxine‐dependent epilepsy. We recommend consideration of treatment with both pyridoxine and folinic acid for patients with α‐AASA dehydrogenase deficiency, and consideration of a lysine restricted diet. The evaluation of patients with neonatal epileptic encephalopathy, as well as those with later‐onset seizures, should include a measurement of α‐AASA in urine to identify this likely underdiagnosed and treatable disorder. Ann Neurol 2008
Übergangsmetall‐katalysierte Diaminierung von Alkenen
Authors: de Figueiredo Renata Marcia 
Published: January 2009

AbstractAls leistungsstarke Methode zum Aufbau relativ komplexer Moleküle, die eine 1,2‐Diamineinheit enthalten, haben sich neue Transformationen auf dem Gebiet der Übergangsmetall‐katalysierten Diaminierung von Alkenen erwiesen (siehe Schema). In diesem Highlight wird ein Überblick über entsprechende Methoden inklusive asymmetrischer Varianten gegeben.magnified image