bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stochastic Fracture Modelling of the Yufutsu Field
Authors: Anraku T. , Namikawa T. , Herring T. , Jenkins I. , Price N. , Trythall R. 
Published: January 2008

Abstract
The Yufutsu field is a fractured granite, gas condensate reservoir, located on Hokkaido island, in the north of Japan. There is minimal primary porosity and secondary porosity consists of fractures. Fractures are categorised into four types according to size (mega, major, minor and halo fractures). Mega fractures govern the flow, while micro fractures govern gas storage. Gas migrated into the reservoir after the fractures were formed.
The field shows abnormal production behaviour, and this paper attempts to characterise production, by the use of 3D-stochastic geological modelling and reservoir simulation. Incorporating all of the effects that were observed from the Yufutsu field into a reservoir model proved to be an extremely complex process.
A three-stage reservoir study was undertaken:
To build a 3D stochastic geological model. Initially small-scale models were built, with both mega and micro fractures modelled stochastically as objects. Effective permeability (matrix + fracture) was calculated across a 200,000 cell single porosity simulation model, along with tracer efflux rates for relative permeability calculations. The above model behaviour was replicated in a 6 cell dual porosity model, which was substituted into the coarser scale single well and full field models.
The resultant methodology used provided accurate and realistic description of the fracture system, which was then used for well planning and production forecasting.
Identification and Implications of Induced Hydraulic Fractures in Waterfloods: Case History HGEU
Authors: Griffin L. G. , Wright C. A , Demetrius S. L. , Blackburn B. D. , Price D. G. 
Published: January 2008

Abstract
In secondary and enhanced oil recovery projects, it is critical to determine if hydraulic fracturing occurs during water injection and, if fracturing occurs, to understand its associated impacts on oil recovery. If hydraulic fracturing occurs under normal injection operating conditions or, if the production and/or injection wells are fracture stimulated, knowing the orientation and dimensions of the created fractures are critical for determining the proper pattern alignment to optimize sweep efficiency. This paper presents the application and results of tiltmeter mapping techniques used at the Howard Glasscock East Unit (HGEU). Tiltmeter mapping was used to determine the existence, orientation, and geometry of created hydraulic fractures, as well as, the dependence of fracture length on the water injection rate. Tiltmeter fracture mapping identified that hydraulic fracturing occurs even at very low water injection rates (less than 250 BWPD) at the HGEU creating significant fractures (exceeding 400 feet of half-length). The mapping also showed that the length of the fractures was relatively rate independent over the range of rates tested. The HGEU waterflood pattern orientation, pattern spacing and injection rate guidelines were established based on these results.
Gas-Well Testing: Changing Requirements, Changing Perspective
Authors: Pridie D. J. 
Published: January 2008

Abstract
In Western Canada at the turn of the century, most gas discoveries are less than 10 106m3 (~3 bcf) in volume and the question has evolved from the simple "At what rate will it flow?" to the complex "How long will it remain commercial?". As a result, reserves measurement and production forecasting have become an integral part of the initial production test. In the planning and fieldwork stages, it is fortunate that a few simple adjustments to accepted testing techniques are all that are required to yield good reserves numbers. In the analysis stage, it has become apparent that pressure responses can be categorized to yield expected production profiles. Some production forecasts depend as much on the profile to be commercial as they do on the reserves. With respect to "rules of thumb", there have grown up some quick formulas for estimating reserves numbers and for forecasting the results of stimulations. The concept of skin factor has metamorphosed in the latter process.
Coiled Tubing Scale Removal of Iron Sulfide - A Case Study of the Kaybob field in Central Alberta
Authors: Bittner S. D. , Zemlak K. R. , Korotash B. D. 
Published: January 2008

Abstract
Iron sulfide scale deposition occurs throughout the Kaybob South field in Central Alberta. The scale typically forms directly on the tubular walls and generally results in corrosion of the metal beneath the scale crystallites. Under normal conditions, iron sulfide is soluble in hydrochloric acid. However, in sour gas and condensate environments, an asphaltene binder forms over the crystallites to limit, if not completely eliminate, the efficiency of chemical removal treatments. In such cases, the scale can only be effectively removed by mechanical means. A number of different methods of scale removal have been attempted, with an inconsistent record of success. For example, on some wells HCl Blends (7%-22% HCl) with xylene have been successful on the first attempt, on other wells this mixture required several attempts, and in some cases this technique resulted in no success. Mechanical options to resolve the problem include a tubing replacement (with an average cost of $150K - $550K CDN depending on completion complexity) or a milling treatment. The milling process, using coiled tubing, a motor and a mill, is costly and carries an element of risk. Well workovers are completed as required in this area on a regular basis - typically one per year.
This case study will define and present the Blaster scale removal system that has been developed to clean tubulars. The techniques have been continually improved and modified since their introduction in January 1998. Amoco Canada participated in the beta test of the system where several modifications to the process were made. Nineteen wells have been completed as part of the test program, the results of which has added valuable data to this case study.
This paper will demonstrate that coiled tubing technology has provided an effective, efficient and economic method of scale removal.
Theoretical Analysis and Design Modification of PDM for Air Drilling
Authors: Samuel G. Robello , Miska Stefan 
Published: January 2008

Abstract
This paper outlines three design modifications of the conventional power section of PDM operating on air. Theoretically, an increase in power output can be achieved by using motor power section with variable cross sectional area. The paper discusses the energy relationships for the various design modifications. Also the paper offers insights to the advantages and disadvantages of various designs.
Efficient Design of Reservoir Simulation Studies for Development and Optimization
Authors: Kalla S. , White C. D. 
Published: January 2008

Abstract
Development studies examine the importance of geologic, engineering, and economic parameters to formulate and optimize production plans. If there are many factors, these studies are prohibitively expensive unless simulation runs are chosen and analyzed efficiently.
Experimental design and response models can improve study efficiency, and have been widely applied in reservoir engineering. To approximate nonlinear oil and gas reservoir responses accurately, designs must consider factors at more than two levels, not just high and low values. However, multilevel designs require many simulations, especially if many factors are being considered. Partial factorial and mixed designs are more efficient than full factorials, but multilevel partial factorial designs are difficult to formulate and have not been used in reservoir engineering.
Orthogonal arrays and nearly orthogonal arrays provide the required design properties and can handle many factors. These arrays span the design space with fewer runs, can be manipulated easily, and are appropriate for computer experiments.
The proposed methods have been applied to a model of a gas well with water coning. Eleven geologic were varied while optimizing three engineering factors (total of fourteen factors). A nearly orthogonal array was specified with three levels for eight factors and four levels for the remaining six geologic and engineering factors. The proposed design required 36 simulations compared to 46 × 38 = 26,873,856 runs for a full factorial design.
Kriged response surfaces can approximate the relationship between the parameters and responses; these are compared to polynomial regression surfaces. Polynomial response surfaces are used to optimize completion length, tubing head pressures, and tubing diameters for a partially penetrating well in a gas reservoir with uncertain properties.
Compared with full and partial factorials, the nearly orthogonal array design improves flexibility, requires fewer simulation runs, and yields more accurate response models. Thus, orthogonal arrays allow more efficient optimization and straightforward sensitivity and uncertainty assessment.
Creating Value by Improving the Operator/Nonoperator Partner Relationship
Authors: van Driel J. P. , Pederson T. 
Published: January 2008

Abstract
Our industry is uniquely characterised by fierce competition to gain access to opportunities such as exploration acreage or participation rights in redevelopment opportunities, and once access is secured cooperation among competitors turned partners is common. In practice, the motivation for the formation of these partnerships is to reduce financial exposure and not to create value. As operators typically assume a dominant role, they drive investment decisions with little, if any, value-creating input from partners. The ultimate development plans therefore may not be attractive to the nonoperating partners, but the alternative of nonparticipation is even worse. These behaviors create a lose-lose situation. For operators, "partner-drag" extends cycle time and increases costs. For nonoperators, value creation opportunities are lost and their control over the future of their investments is less than they are entitled to, based on their equity.
This paper explores some critical questions: Do partnerships create or destroy value? What role should a non-operating partner play in a venture, and what competency does it require to be able to make positive contributions? Should partners focus on errors of omission (i.e., missing high-value opportunities, doing the wrong project) or on errors of commission (i.e., not getting full value from execution, doing the project wrong)? The authors, drawing on Petoro case studies, will share lessons learned and best practices developed from implementing a business model based entirely on creating value as a nonoperating partner. Novel work processes are presented, based on these learnings, that improve the relationship between operators and nonoperating partners from lose-lose to win-win.
Numerical Simulation of Steam Displacement of Oil in Naturally Fractured Reservoirs Using Fully Implicit Compositional Formulation: A Comparative Analysis of the Effects of Capillary and Gravitational Forces in Matrix/Fracture Exchange Term
Authors: Cicek O. 
Published: January 2008

Abstract
A numerical simulator for steam displacement of oil from naturally fractured reservoirs is developed and tested. The three-dimensional and three phase field scale model employs a compositional dual-porosity/dual-permeability mathematical formulation. Capillary, gravitational and viscous forces are accounted for in the mathematical model. Using a fully implicit solution scheme, the model solves for (2nHC+10) primary variables simultaneously, where nHC is the number of hydrocarbon components. All reservoir parameters are formulated as functions of all the primary variables. The model is linearized using Newton-Raphson method, and the system of linear equations is solved by a direct and an iterative solver. The model is verified against the Fourth and Sixth SPE Comparative Solution Projects. The model is highly stable for the studied extremely dynamic and stiff problems, accommodating large time steps with two to three Newtonian iterations. The simulations are carried out up to ten years to test the features of the model for long periods of steam injection in naturally fractured systems.
Fluid exchange between the fracture and the matrix blocks due to the gravitational, capillary and viscous forces is investigated for a range of naturally fractured reservoirs with different matrix block sizes and capillary pressures. Relative effects and relative magnitutes of these acting forces on the displacement of the matrix oil are analysed in these naturally fractured systems undergoing steam injection. This comprehensive and comparative analysis is conducted using different realizations of the studied naturally fractured systems such as the dual-permeability and the dual-porosity models.
The steam injection operations are carried out for long periods of time. The low initial pressures in the studied fractured systems facilitate zooming in on and observing how, in particular, the capillary and gravitational forces work, and testing the model under more strained conditions in a naturally fractured reservoir undergoing a steam injection operation.
Effect of Oil and Flue-Gas Compositions on Oil Recovery in the Flue-Gas/Light-Oil Injection Process
Authors: Shokoya O. S. , Mehta S. A. , Moore R. G. , Maini B. 
Published: January 2008

Abstract
Flue gas injection is becoming more attractive as a feasible and environmentally friendly process for improving oil recovery from light oil reservoirs. When obtained from surface sources, the flue gas process has an added advantage of preventing carbon dioxide (CO2), a greenhouse gas, from being disposed into the atmosphere. Flue gas can also be generated in-situ by the spontaneous ignition of oil when air, a readily available gas, is injected into high temperature, high pressure (light oil) reservoirs. The availability of flue gas and/or air and the observed high oil recovery potential make the flue gas process an economically attractive process. Oil recovery efficiency and displacement characteristics were studied in the laboratory with nitrogen and two flue gas compositions having CO2 content of 16% and 30% and two light oils obtained from two different reservoirs. The recombined light oils were displaced by the flue gases in a 2.44 m long, 5.1 cm diameter Berea sandstone core at irreducible brine saturation. The studies were conducted at reservoir pressures up to 41.58 MPa and temperatures of 80.6°C and 116°C, corresponding to the reservoir temperature of the oils studied. The experimental data was history-matched with a fully compositional simulator and the results show that oil recovery efficiency has a direct relationship to the paraffin and naphthene content of the oil. It was found during the core flood that the displacement of the oil with lower paraffin (higher naphthene) content produced more oil than the displacement with higher paraffin at one pore volume of flue gas injected, even at lower operating pressure.
HNF4α and the Ca-Channel TRPC1 Are Novel Disease Candidate Genes in Diabetic Nephropathy
Authors: Niehof Monika , Borlak Jürgen 
Published: January 2008

OBJECTIVE—The nuclear receptor hepatic nuclear factor 4α (HNF4α) is a master regulatory protein and an essential player in the control of a wide range of metabolic processes. Dysfunction of HNF4α is associated with metabolic disorders including diabetes. We were particularly interested in investigating molecular causes associated with diabetic nephropathy.
RESEARCH DESIGN AND METHODS—Novel disease candidate genes were identified by the chromatin immunoprecipitation–cloning assay and by sequencing of immunoprecipitated DNA. Expression of candidate genes was analyzed in kidney and liver of Zucker diabetic fatty (ZDF) and of streptozotocin (STZ)-administered rats and after siRNA-mediated silencing of HNF4α.
RESULTS—We identified the calcium-permeable nonselective transient receptor potential cation channel, subfamily C, member 1 (TRPC1) as a novel HNF4α gene target. Strikingly, TRPC1 is localized on human chromosome 3q22-24, i.e., a region considered to be a hotspot for diabetic nephropathy. We observed a significant reduction of TRPC1 gene expression in kidney and liver of diabetic ZDF and of STZ-administered rats as a result of HNF4α dysfunction. We found HNF4α and TRPC1 protein expression to be repressed in kidneys of diabetic patients diagnosed with nodular glomerulosceloris as evidenced by immunohistochemistry. Finally, siRNA-mediated functional knock down of HNF4α repressed TRPC1 gene expression in cell culture experiments.
CONCLUSIONS—Taken collectively, results obtained from animal studies could be translated to human diabetic nephropathy; there is evidence for a common regulation of HNF4α and TRPC1 in human and rat kidney pathologies. We propose dysregulation of HNF4α and TRPC1 as a possible molecular rationale in diabetic nephropathy.
B-Cells Promote Intra-Islet CD8+ Cytotoxic T-Cell Survival to Enhance Type 1 Diabetes
Authors: Brodie Gillian M. , Wallberg Maja , Santamaria Pere , Wong F. Susan , Green E. Allison 
Published: January 2008

OBJECTIVE—To determine the role of B-cells in promoting CD8+ T-cell—mediated β cell destruction in chronically inflamed islets.RESEARCH DESIGN AND METHODS—RIP-TNFα-NOD mice were crossed to B-cell–deficient NOD mice, and diabetes development was monitored. We used in vitro antigen presentation assays and in vivo administration of bromodeoxyuridine coupled to flow cytometry assays to assess intra-islet T-cell activation in the absence or presence of B-cells. CD4+Foxp3+ activity in the absence or presence of B-cells was tested using in vivo depletion techniques. Cytokine production and apoptosis assays determined the capacity of CD8+ T-cells transform to cytotoxic T-lymphocytes (CTLs) and survive within inflamed islets in the absence or presence of B-cells.RESULTS—B-cell deficiency significantly delayed diabetes development in chronically inflamed islets. Reintroduction of B-cells incapable of secreting immunoglobulin restored diabetes development. Both CD4+ and CD8+ T-cell activation was unimpaired by B-cell deficiency, and delayed disease was not due to CD4+Foxp3+ T-cell suppression of T-cell responses. Instead, at the CTL transition stage, B-cell deficiency resulted in apoptosis of intra-islet CTLs.CONCLUSIONS—In inflamed islets, B-cells are central for the efficient intra-islet survival of CTLs, thereby promoting type 1 diabetes development.
COOH-Terminal Clustering of Autoantibody and T-Cell Determinants on the Structure of GAD65 Provide Insights Into the Molecular Basis of Autoreactivity
Authors: Fenalti Gustavo , Hampe Christiane S. , Arafat Yasir , Law Ruby H.P. , Banga J. Paul , Mackay Ian R. , Whisstock James C. , Buckle Ashley M. , Rowley Merrill J. 
Published: January 2008

OBJECTIVE—To gain structural insights into the autoantigenic properties of GAD65 in type 1 diabetes, we analyzed experimental epitope mapping data in the context of the recently determined crystal structures of GAD65 and GAD67, to allow “molecular positioning” of epitope sites for B- and T-cell reactivity.RESEARCH DESIGN AND METHODS—Data were assembled from analysis of reported effects of mutagenesis of GAD65 on its reactivity with a panel of 11 human monoclonal antibodies (mAbs), supplemented by use of recombinant Fab to cross-inhibit reactivity with GAD65 by radioimmunoprecipitation of the same mAbs.RESULTS—The COOH-terminal region on GAD65 was the major autoantigenic site. B-cell epitopes were distributed within two separate clusters around different faces of the COOH-terminal domain. Inclusion of epitope sites in the pyridoxal phosphate–and NH2-terminal domains was attributed to the juxtaposition of all three domains in the crystal structure. Epitope preferences of different mAbs to GAD65 aligned with different clinical expressions of type 1 diabetes. Epitopes for four of five known reactive T-cell sequences restricted by HLA DRB1*0401 were aligned to solvent-exposed regions of the GAD65 structure and colocalized within the two B-cell epitope clusters. The continuous COOH-terminal epitope region of GAD65 was structurally highly flexible and therefore differed markedly from the equivalent region of GAD67.CONCLUSIONS—Structural features could explain the differing antigenicity, and perhaps immunogenicity, of GAD65 versus GAD67. The proximity of B- and T-cell epitopes within the GAD65 structure suggests that antigen-antibody complexes may influence antigen processing by accessory cells and thereby T-cell reactivity.
Activation of Central Lactate Metabolism Lowers Glucose Production in Uncontrolled Diabetes and Diet-Induced Insulin Resistance
Authors: Chari Madhu , Lam Carol K.L. , Wang Penny Y.T. , Lam Tony K.T. 
Published: January 2008

OBJECTIVE—Hypothalamic lactate metabolism lowers hepatic glucose production and plasma glucose levels in normal rodents. However, it remains unknown whether activation of hypothalamic lactate metabolism lowers glucose production and plasma glucose levels in rodents with diabetes and obesity.
RESEARCH DESIGN AND METHODS—We performed intracerebroventricular (ICV) administration of lactate to enhance central lactate metabolism in 1) early-onset streptozotocin-induced uncontrolled diabetic rodents, 2) experimentally induced hypoinsulinemic normal rodents, and 3) early-onset diet-induced insulin-resistant rodents. Tracer-dilution methodology was used to assess the impact of ICV lactate on the rate of glucose production in all three models.
RESULTS—We first report that in the absence of insulin treatment, ICV lactate administration lowered glucose production and glucose levels in rodents with uncontrolled diabetes. Second, ICV lactate administration lowered glucose production and glucose levels in normal rodents with experimentally induced hypoinsulinemia. Third, and finally, ICV lactate administration lowered glucose production in normal rodents with diet-induced insulin resistance.
CONCLUSIONS—Central lactate metabolism lowered glucose production in uncontrolled diabetic and normal rodents with hypoinsulinemia and in rodents with diet-induced insulin resistance. These data suggest that insulin signaling is not required for central lactate to lower glucose production and that the activation of hypothalamic lactate metabolism could consequently bypass insulin resistance and lower glucose levels in early-onset diabetes and obesity.
Effect of Polishing Techniques and Time on Surface Roughness, Hardness and Microleakage of Resin Composite Restorations
Authors: Venturini D. , Cenci M. S. , Demarco F. F. , Camacho G. B. , Powers J. M. 
Published: January 2008

Clinical RelevanceThe effects of polishing techniques on surface roughness, microhardness and microleakage of resin composites are material dependent. In general, since immediate polishing has not had a negative influence on the tested properties of the two composites compared to delayed polishing, this procedure could be preferred, reducing the number of clinic sessions and bringing more comfort and satisfaction to the patient.
Effect of Restorative Procedures and Occlusal Loading on Cuspal Deflection
Authors: González-López S. , De Haro-Gasquet F. , Vílchez-Díaz MÁ , Ceballos L. , Bravo M. 
Published: January 2008

Clinical Relevance
The progressive elimination of dental tissue, especially removal of marginal ridges and dentin above the pulp chamber and application of increasing occlusal loads, were related to a higher cuspal deflection.
Use of Two Surface Analyzers to Evaluate the Surface Roughness of Four Esthetic Restorative Materials After Polishing
Authors: Joniot S. , Salomon J. P. , Dejou J. , Grégoire G. 
Published: January 2008

Clinical RelevanceAll esthetic restorative materials do not have the same polishing characteristics. Nanofilled composites and fluid materials containing microfiller give the best surface states. Results with posterior composites and compomers are less effective.