bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorescence and Electron Microscopic Localization of F-actin in the Ependymocytes
Authors: Li Yan-Chao , Bai Wan-Zhu , Sakai Kazuhisa , Hashikawa Tsutomu
Published: April 2009

The organization of F-actin in the ventricular system has been reported to display pronounced regional differences with respect to shape, size, and development. However, the real roles played by F-actin in these cells cannot be understood unless the precise localization of F-actin is defined. In the present study, we used double-fluorescence labeling to further examine the localization of F-actin in the ependymocytes and its spatial relation to the other two cytoskeletal components, microtubules and intermediate filaments. Then we converted fluorescence signals for F-actin to peroxidase/DAB reaction products by use of a phalloidin-based FITC-anti-FITC system. This detection technique provided an overview of the distribution of F-actin in the ependymocytes at the ultrastructural level, and has been proven to be helpful in correlating light and electron microscopic investigations.
Numerical Simulation of the Mechanical Properties of Cr12 Steel during Gas Quenching
Authors: Li Ziliang , Cheng Heming , Li Jianyun , Hou Lijun
Published: April 2009

Heat treatment is one method to improve mechanical properties of metal, but each heat treatment method has its advantages and disadvantages, therefore, different requirements regarding size, shape, and properties with respect to different heat treatment processes should be considered. Gas quenching is a heat treatment process used in various industries such as the aerospace, automotive, machine tool, and other advanced manufacturing processes. The use of gas quenching can significantly improve the mechanical and physical properties of a material. Simulation of gas quenching processes is becoming increasingly important, although not common, for the investigation of mechanical properties and their effects on quality. This paper is based on the theory of phase transformation, computational mechanics, thermal nonelasticity, and the character of the gas quenching process. A nonlinear heat conduction equation considering phase transformation is developed and a model of the relationship between the phase transformation products and the properties of Cr12 steel are established and solved using the finite element method (FEM). By comparing calculated results with those of experiments, satisfying agreement is found. It is anticipated that this model will be valuable for further theoretical development and practical applications.
Evolution of New Disease Specificity at a Simple Resistance Locus in a Crop–Weed Complex: Reconstitution of theLr21Gene in Wheat
Authors: Huang Li , Brooks Steven , Li Wanlong , Fellers John , Nelson James C , Gill Bikram
Published: April 2009

The wheat leaf-rust resistance gene Lr21 was first identified in an Iranian accession of goatgrass, Aegilops tauschii Coss., the D-genome donor of hexaploid bread wheat, and was introgressed into modern wheat cultivars by breeding. To elucidate the origin of the gene, we analyzed sequences of Lr21 and lr21 alleles from 24 wheat cultivars and 25 accessions of Ae. tauschii collected along the Caspian Sea in Iran and Azerbaijan. Three basic nonfunctional lr21 haplotypes, H1, H2, and H3, were identified. Lr21 was found to be a chimera of H1 and H2, which were found only in wheat. We attempted to reconstitute a functional Lr21 allele by crossing the cultivars Fielder (H1) and Wichita (H2). Rust inoculation of 5876 F2 progeny revealed a single resistant plant that proved to carry the H1H2 haplotype, a result attributed to intragenic recombination. These findings reflect how plants balance the penalty and the necessity of a resistance gene and suggest that plants can reuse “dead” alleles to generate new disease-resistance specificity, leading to a “death–recycle” model of plant-resistance gene evolution at simple loci. We suggest that selection pressure in crop–weed complexes contributes to this process.
Distal Recognition Sites in Substrates Are Required for Efficient Phosphorylation by the cAMP-Dependent Protein Kinase
Authors: Deminoff Stephen J , Ramachandran Vidhya , Herman Paul K
Published: April 2009

Protein kinases are important mediators of signal transduction in eukaryotic cells, and identifying the substrates of these enzymes is essential for a complete understanding of most signaling networks. In this report, novel substrate-binding variants of the cAMP-dependent protein kinase (PKA) were used to identify substrate domains required for efficient phosphorylation in vivo. Most wild-type protein kinases, including PKA, interact only transiently with their substrates. The substrate domains identified were distal to the sites of phosphorylation and were found to interact with a C-terminal region of PKA that was itself removed from the active site. Only a small set of PKA alterations resulted in a stable association with substrates, and the identified residues were clustered together within the hydrophobic core of this enzyme. Interestingly, these residues stretched from the active site of the enzyme to the C-terminal substrate-binding domain identified here. This spatial organization is conserved among the entire eukaryotic protein kinase family, and alteration of these residues in a second, unrelated protein kinase also resulted in a stable association with substrates. In all, this study identified distal sites in PKA substrates that are important for recognition by this enzyme and suggests that the interaction of these domains with PKA might influence specific aspects of substrate binding and/or release.
Psychiatric Characteristics in a Self-Selected Sample of Boys With Klinefelter Syndrome
Authors: Bruining Hilgo , Swaab Hanna , Kas Martien , van Engeland Herman
Published: April 2009

BACKGROUND. Klinefelter syndrome is the most frequent chromosomal aneuploidy with a prevalence of 1 in 700. Klinefelter syndrome has been widely associated with cognitive impairment and language problems. No previous studies have systematically investigated the association of Klinefelter syndrome with psychiatric disorders in children and adolescents. To our knowledge, the only data available are from psychiatric inventories of adults with Klinefelter syndrome.

OBJECTIVE. To explore the extent of psychiatric morbidity in children with Klinefelter syndrome.

METHOD. Fifty-one subjects with Klinefelter syndrome aged 6 to 19 years were included through the Dutch Klinefelter association and 2 university medical centers. The sample was screened by using structured and standardized assessment procedures covering the full range of psychiatric problems and disorders. In addition, all boys were formally evaluated for the presence of a language disorder.

RESULTS. A wide range of classifications could be applied, with language disorder (65% [33 of 51]) as the most prevalent disorder, followed by attention-deficit disorders (63% [32 of 51]) and autism spectrum disorder (27% [14 of 51]). Behavioral impairment was most evident among cases classified as autism spectrum disorder and psychotic disorder (12% [6 of 51]).

CONCLUSIONS. Children with Klinefelter syndrome seem to be at risk for problems in social and language development, as well as for problems in regulation of emotion and behavior. This is reflected in the broad spectrum of psychiatric classifications applicable in the present selected sample. Health care professionals should be aware of an increased a priori possibility of psychiatric problems when confronted with a child with Klinefelter syndrome.
Managing Iron Overload in Patients with Myelodysplastic Syndromes with Oral Deferasirox Therapy
Authors: Jabbour Elias , Garcia-Manero Guillermo , Taher Ali , Kantarjian Hagop M.
Published: April 2009

Patients with myelodysplastic syndromes (MDS) often require chronic RBC transfusions, which can lead to iron overload. Without adequate management, this may cause progressive damage to hepatic, endocrine, and cardiac organs, significantly affecting overall survival. Recent retrospective analyses have suggested that iron chelation provides a survival advantage in iron-overloaded patients with MDS who are given chelation therapy compared with those who are not. Nonetheless, it is evident that iron overload in many patients with MDS is not adequately managed. Clinical evaluation of the once-daily, oral iron chelator deferasirox in MDS populations has indicated that it provides dose-dependent reductions in body iron burden and is generally well tolerated, with a manageable safety profile in adult and pediatric patients. The most common treatment-related adverse events (AEs) included transient, mild-to-moderate gastrointestinal disturbances and skin rash, which rarely required drug discontinuation and resolved spontaneously in most cases. Adequate management of AEs and practical approaches such as patient education and counseling are necessary to ensure that patients remain compliant with therapy. Regular monitoring of serum ferritin levels is key to identifying patients who require iron chelation therapy, and to ensure maintenance of iron levels below the critical level of 1,000 μg/l. The flexible dosing regimen of deferasirox allows dose adjustments to be made in response to trends in serum ferritin, to changes in a patient’s transfusional iron intake, and to the objectives of treatment, allowing the full benefit of transfusion therapy without the risks associated with iron overload.
Vision and Will: The Future of the FDA
Authors: Epstein David
Published: April 2009

This commentary urges the U.S. Food and Drug Administration to facilitate collaboration among themselves, the industry, and the National Cancer Institute to deliver the best therapies and diagnostics for cancer patients.
Forensic engineering of fire-damaged structures
Authors: Ingham Jeremy
Published: April 2009

There has never been a greater need for buildings, tunnels and other infrastructure to be assessed for damage following fires. Even after a severe fire, structures are often capable of being repaired rather than demolished. This paper describes the role of forensic engineers in the investigation of fire-damaged structures constructed in concrete, steel and masonry. Forensic-engineering procedures described include on-site inspection and testing techniques, laboratory testing and structural fire analysis. The design and implementation of repairs is also discussed.
Learning lessons from forensic investigations of corrosion failures
Authors: John Gareth , Edwards Tony , Wright Adrian , Broadhurst Mike , Newton Chris
Published: April 2009

Lessons and solutions learned from the forensic investigation of corrosion failures need to be applied throughout the lifecycle of structures. Avoiding misplaced solutions during both design and operating phases relies upon a disciplined and professional forensic approach for all corrosion failure investigations. This paper sets out the elements of the approach and explains how lessons can be learned to prevent future corrosion failures. In particular it describes the macroscopic and microscopic methods required for accurate identification of corrosion failure mechanisms and successful root-cause analysis.
Forensic investigation of fluvial flood damage in the Czech Republic
Authors: Holický Milan , Sýkora Miroslav
Published: April 2009

A number of structures in the Czech Republic were affected by flooding in August 2002. In particular, damage to structures adjacent to the Vltava River in Prague was on an unprecedented scale. This paper reports on a forensic investigation to assess whether the flooding was exceptional and to identify the main causes of structural failure. The work included statistical analysis of hydrological data dating back to 1827, from which it was shown the 2002 event had a considerably long return period. However, the investigation also revealed that lack of structural robustness may have contributed to disproportionate failure.
A systematic approach to forensic foundation engineering
Authors: Poulos Harry
Published: April 2009

Forensic geotechnical engineering is gaining increasing importance in many countries where foundation failures may lead to litigation and even criminal action. This paper sets out a framework for forensic geotechnical assessments of foundation failures, involving a systematic consideration of the various factors that may have influenced the failure. One or more credible hypotheses are then formulated and tested for consistency with the observed behaviour. A case study of a tilting office block in Indonesia is presented to illustrate the approach.
Forensic investigation of blast damage to British buildings
Authors: Keane Bill , Esper Philip
Published: April 2009

Buildings in mainland Britain have suffered from several serious blast incidents over the past two decades, from the 1992 St Mary Axe bomb in the City of London to the Buncefield oil depot explosion in 2005. This paper is based on the authors' experiences of investigating and repairing the resulting damage to many of the major buildings involved in these incidents. It describes how forensic investigation – including laboratory and on-site testing and computer modelling and analysis techniques – was vital to these investigations to assess dynamic response, extent of damage and residual strength of the buildings and structural elements.
Forensic structural engineering practice in the USA
Authors: Ratay Robert T.
Published: April 2009

Structural failures during construction or in service nearly all result in claims and litigation, the outcome of which is strongly influenced by forensic investigations. Identifying causes of failure and the party responsible, plus technical presentation of subsequent claims and defences, generally requires all parties to engage forensic engineers as witnesses. This paper is an overview of the highly active professional practice of forensic structural engineering in the USA, possibly the world's most litigious environment for construction. It discusses the origins and causes of failures, the process of forensic investigation, the role of expert witnesses and a list of further reading.
Selecting sustainable materials for ceilings in Sri Lanka
Authors: Yasantha Abeysundara U. G. , Babel S.
Published: April 2009

This paper presents a method to select sustainable materials for ceilings (elements) of buildings in Sri Lanka taking into consideration environmental, economic and social assessments of materials in a life-cycle perspective. Two types of elements were selected for this study, namely, asbestos and timber. The environmental burdens associated with these materials were analysed in terms of embodied energy and environmental impacts such as global warming, acidification and nutrient enrichment. It was found that asbestos elements were better than timber elements in environmental scores; acidification and nutrient enrichment. Timber elements were better in terms of global warming and embodied energy. On economic scores asbestos elements were better. On social scores, also, the asbestos element (137·8) was slightly higher than the timber element (134·35) and was thus slightly better. These scores are presented in a matrix which will assist in the selection of sustainable materials for these elements. Similar matrices can also be developed for other building elements, such as roofs, walls, doors, windows and floors.
Fly-ash-blended lean concrete mixes for concrete blocks
Authors: Venkatarama Reddy B. V. , Chander A.
Published: April 2009

Fly ash is used to improve the properties of concrete in both fresh and hardened states. This study was focused on the characteristics of fly-ash-blended lean concrete mixes suitable for production of solid concrete blocks used for masonry walls and for non-structural applications. The influence of superplasticiser and low calcium fly ash on the workability of two lean concrete mixes was examined. Replacement of both cement and sand by up to 50% fly ash was attempted. The compressive strength and fly-ash content relationships for the two lean concrete mixes were obtained. Maximum compressive strength was obtained for 10% cement replacement and 40% sand replacement by fly ash. The strength increased by two to three times when compared with concrete without fly ash. Similar enhanced strength for masonry was also observed for blocks with fly ash. The maximum flexural bond strength of masonry was for masonry couplets using blocks having 10% cement replaced by fly ash. The study showed that addition of fly ash to lean concrete mixes significantly enhanced the strength of the concrete
Environmental properties of pentafluorosulfanyl compounds: Physical properties and photodegradation
Authors: Jackson Derek A. , Mabury Scott A.
Published: April 2009

The pentafluorosulfanyl (SF5) functional group was investigated from an environmental perspective to ascertain its physical properties and photolytic fate. Five aromatic probe compounds were compared with their trifluoromethyl analogs. Water solubilities for SF5 compounds ranged from 78 mg/L to 2.4 g/L. Octanol—water partitioning coefficients ranged from log Kow = 2.9 to 3.6, all of which were approximately 0.5 to 0.6 log units more hydrophobic than their trifluoromethyl analogs. The direct photolytic fate of SF5 compounds was studied, and the SF5 group was found to completely degrade using actinic radiation with hourly half-lives. The reaction was followed by high-performance liquid chromatography with a UV-visible detector, 19F nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. It was found that five equivalents of fluoride were released to form a benzenesulfonate as a final product of photodegradation. Finally, an SF5 analog of fluometuron, a potentially new herbicide, was synthesized and likewise photolyzed. The present study provides the first evidence that pentafluorosulfanyl can degrade under mild, environmentally relevant conditions.
ME Surfactant Increases Production in the Codell Formation of the DJ Basin
Authors: Paterniti M.
Published: April 2009

A Denver-Julesburg (DJ) Basin operator, Anadarko Petroleum Corp., has had success with the optimization of its completions in the Codell formation. The use of a microemulsion additive (ME) is one of the keys that has allowed them to further improve production and increase reserves.

Before the ME surfactant, the operator used a non-emulsifier (NE) as a surfactant in their stimulation treatments. By replacing the surfactant with the ME, their median production has increased by 10%. In addition, lower GOR wells show the most benefit from the use of the ME additive, meaning that margins on wells in lower GOR areas can be improved. Anadarko began testing the ME additive in 2005 while still completing some Codell wells with the NE. After review, the ME additive was run almost exclusively.

This paper compares the wells using ME to those using the conventional NE surfactant. The study wells were chosen to minimize potential production effects caused by other factors, such as job size and depletion. After eliminating these other factors, the sample size consisted of 32 NE wells and 34 ME wells across the basin. The wells were compared on a broad scope and where possible, offset wells were compared.
Development of a Calibrated Fracture-Growth Model and Automated Staging Routine for the Jonah Field
Authors: Malone Scott , Turner Mark , Mayerhofer Mike , Northington Neill , Weijers Leen
Published: April 2009

One of the most important challenges in the Jonah Field in Sublette County, Wyoming, is to obtain effective fracture-height coverage over the entire 2,800+ ft Lance formation. The Lance formation in Jonah Field is composed of a stacked sequence of 20 to 50 fluvial channel sands interbedded with associated overbank siltstone and floodplain shale deposits. Within this interval, the net-to-gross ratio varies from 25 to 40%. Sandstone bodies occur as individual 10- to 25-ft thick channels and stacked-channel sequences greater than 200 ft in some cases.

Tiltmeter and microseismic fracture mapping was conducted on hundreds of propped-fracture treatments in the Jonah Field. These direct height-growth measurements helped to obtain an understanding about the effectiveness of shale barriers. It was found that a standard triple-combo log suite could be used to identify shale barriers for fracture growth.

A calibrated fracture model was developed for the Jonah Field that ties the log analysis to the fracture-growth behavior that was mapped using direct fracture-mapping technologies and to the net-pressure response measured during propped fracture treatments. These improvements in predictive modeling capabilities have lead to better insight into fracture growth behavior in the Lance formation.

A 3D fracture-growth model was modified to determine perforation strategy and fracture-treatment schedules to obtain effective coverage of the Lance formation in new Jonah wells in a semi-automated process. As a result, the entire process for fracture design can now be performed in an integrated software package.
Evaluating the Performance of Hydraulically Fractured Horizontal Wells in the Bakken Shale Play
Authors: Tabatabaei M. , Mack D. , Daniels R.
Published: April 2009

In the last several years, interest in developing unconventional oil and gas reservoirs has grown tremendously. Most of these unconventional reservoirs have very low permeability which makes them unable to produce at economic flow rates without massive stimulation treatments or special recovery processes. Bakken Shale play is one of these reservoirs which horizontal wells with hydraulic fracture treatments have been proven to be an effective method for its development. In this study, to evaluate the performance of hydraulically fractured horizontal wells in the Bakken Shale play, a rigorous analytical model has been developed to predict the productivity of a tight multi-layered reservoir drained by a horizontal well with a longitudinal fracture. This model rigorously couples flow in the matrix to flow in the fracture, and then to flow in the wellbore to account for the fracture conductivity and wellbore hydraulics, respectively.

History matching of production data for Bakken wells reveals that the developed model provides a reliable tool for predicting the productivity of this type of well-reservoir configuration. Moreover, using this model to study the key factors influencing the well performance indicates that length of fractured portion of the lateral is the primary factors affecting the well productivity, while conductivity of fracture has an insignificant effect on productivity, which means using better proppant or fluid has minimal effect on productivity.
Analytical Solutions for the Radial flow Equation with Constant-Rate and Constant-Pressure Boundary Conditions in Reservoirs with Pressure-Sensitive Permeability
Authors: Friedel Torsten , Voigt Hans-Dieter
Published: April 2009

The transient pressure response in stress-sensitive formations is derived by solving analytically the radial flow equation with pressure-dependent rock properties. New solutions are obtained for slightly compressible fluids and real gas flow with constant-rate and constant-pressure wellbore boundary conditions using the Boltzmann transformation. In particular in low-permeability formations, a sensitivity exists to pore pressure changes. Permeability there normally declines with the increase of effective stress. The mathematical model presented here takes into account the reduction in permeability caused by an increase in effective stress for two common parameterized pressure-permeability functions, i.e., a linear and an exponential relationship. The analytical solutions are verified with numerical simulation. They are applicable for well test analysis and prediction of flow rates, as demonstrated in this paper.
Advancing Reservoir Simulation Capabilities for Tight Gas Reservoirs
Authors: Abacioglu Yafes , Sebastian Herbert M. , Oluwa Jubril B.
Published: April 2009

It is critical to identify optimum well spacing to develop cost-effective full field development plans for tight gas reservoirs. Accurate prediction of well performance is a major challenge that arises during the development of such reservoirs. Understanding well performance is needed for both well design and depletion planning. Almost all wells in tight gas fields are hydraulically fractured. We have investigated methods of simulating hydraulic fractures using coarse grids since explicitly gridding these fractures can easily lead to an impractical number of grid blocks for large, full field models with many and complex wells.

We have developed practical solutions for accurately representing both flowing and shut-in performance of hydraulically fractured vertical wells and multiply fractured horizontal wells in full-field models. We have validated these approximations in trials with actual field examples.

We found it necessary to enable wellbore cross-flow in the simulator for coarse grid field-scale models to more accurately simulate observed shut-in pressures. We also found differences in pressure distribution results of finite difference simulation between models using a pressure formulation vs. those using a pseudo-pressure formulation when simulating tight gas reservoirs under certain conditions.

In summary, the existing commercial reservoir simulation tools can be adapted to model challenging tight gas depletion scenarios and optimize well spacing. However, care must be taken to ensure that the models are properly constructed and results frequently checked for consistency.
An Effective Model for Pipe Friction Estimation in Hydraulic Fracturing Treatments
Authors: Barree R. D. , Gilbert J. V. , Conway M. W.
Published: April 2009

An adequate model of pipe friction and fluid hydrostatic head is needed to allow understanding of bottomhole treating pressure trends during pumping. Models currently used by service providers appear to be inadequate, based on observation of field bottomhole treating pressure (BHP) plots. A new model is provided which has been extensively tested for gelled fluids, foams, and slick-water fracs. The model predictions are compared to direct measurements of BHP during typical high-rate treatments in various pipe sizes.

Use of an adequate pipe friction model improves analysis of stimulation treating pressures and allows better decisions to be made regarding on-the-fly design changes and post-job interpretations of created fracture geometry and resulting conductivity. The paper presents a useful model for the estimation of pipe friction, slurry head, and surface treating pressure during hydraulic fracturing treatments.
Estimates of Potential CO2 Demand for CO2 EOR in Wyoming Basins
Authors: Wo S. , Whitman L. D. , Steidtmann J. R.
Published: April 2009

A database of Wyoming oil reservoirs is developed to identify candidate reservoirs suitable for miscible or immiscible CO2 flooding, a method that has already proven to be a viable enhanced oil recovery process at Lost Soldier, Wertz, and Salt Creek fields in Wyoming. Based on the CO2 usage of existing CO2-EOR projects in Wyoming and other regions, the initial and total CO2 demands are estimated for the identified reservoirs and grouped by basins. The simple formulas presented in this paper provide a quick estimation of the required initial and total CO2 volumes with specified reservoir parameters. Wyoming has produced about seven billion barrels of oil from more than 1200 oil producing fields. 98% of the oil was produced from the top 400 fields, evaluated in this study, each with a cumulative production exceeding one million barrels of oil. More than 500 oil reservoirs, by passing either miscible or immiscible screening criteria, are identified as potential CO2-EOR candidates. Large fields often have multiple oil producing reservoirs suitable for CO2 flooding. It is estimated that 1.2 to 1.8 billion barrels of additional oil might be recovered by CO2 flooding and up to 20 trillion cubic feet of CO2 could be sequestrated after CO2 EOR in Wyoming's oil basins.
Haynesville Shale-Petrophysical Evaluation
Authors: Parker Mark , Buller Dan , Petre Erik , Dreher Doug
Published: April 2009

The Haynesville Shale is an unconventional gas reservoir located in east Texas and northwest Louisiana. High gas prices and the success of other shale gas plays have led operators to invest highly in this unconventional reservoir. It has great potential for development by applying all the new technology that is available in the oil and gas industry today.

Petrophysical evaluation of reservoirs has long been used for exploration and reserve estimates. New logging tools and analysis techniques have been developed to provide more precise data about target zones and bounding layers that are important when considering hydraulic fracturing for unconventional reservoirs.

A processed log interpretation calibrated for the Haynesville Shale is computed using a typical triple-combo suite of logs. Other log data, such as borehole imaging, magnetic resonance, dipole sonic, and spectral gamma ray, will improve and verify the interpretation. Core analysis provides accessory data on mineralogy, total organic carbon (TOC), and rock mechanical properties to calibrate this processed log computation and improve the accuracy of the total shale interpretation.

Identification of the following reservoir characteristics provides the starting point for completion-and hydraulic-fracture stimulation design: Identification of free-gas zonesIdentification of rock types and mineralogyTotal organic contentQuantification of effective shale porosityEstimates of shale permeabilityMechanical stress measurement for hydraulic-fracturing designIdentification, classification, and orientation of marginal-class, open-conductive, and drilling-induced fractures

A number of Haynesville Shale examples are presented to highlight all interpretation techniques and variations in the shale itself within its proven productive area. This interpretation can be critical for the hydraulic-fracture design approach for the Haynesville Shale.
A Simple Method to Account for Permeability Anisotropy in Reservoir Models and Multi-Well Pressure Interference Tests
Authors: Yetkin C. , Ramirez B. , Al-kobaisi M. , Kazemi H. , Ozkan E.
Published: April 2009

Permeability anisotropy, via full permeability tensor, has not been accurately accounted for in reservoir models because of the implementation complexity. Specifically, numerical implementation of the off-diagonal components of the permeability tensor is inconvenient and cumbersome. This paper shows how directional permeability, calculated from a full permeability tensor, can be used as a simple replacement both in coding numerical models and in day-to-day engineering analysis. For the former, we have implemented the directional permeability for single-phase flow in a 9-point finite-difference formulation, which is easy to code. This formulation, however, is easily applicable to any control-volume formulation including the perpendicular bisector (PEBI) grid. The implementation of this technique has produced excellent numerical results in numerical simulation of multi-phase flow displacement. For routine engineering applications, we have also applied this technique to generate pressure responses for a four-well interference test in a highly anisotropic system. The analysis of the test results by conventional type-curve matching produced the correct reservoir geometric-average permeability and a very good approximation for the direction of the maximum permeability, which is a testimony to the credibility of the formulation. The use of this formulation should be very useful in determining major natural fracture trends in reservoirs undergoing water or gas injection, and in modeling fracture trends in other fractured reservoir situations, such as tight sands.
Exponential Growth in San Juan Basin Fruitland Coalbed Permeability With Reservoir Drawdown—Model Match and New Insights
Authors: Shi J. -Q. , Durucan S.
Published: April 2009

The exponential growth behaviour of coalbed permeability with reservoir pressure depletion has previously been observed at the Fairway wells in the San Juan Basin. More recently the exponential trend has also been confirmed for a group of 10 wells in a region NE of Fairway. Increase in the absolute permeability of coalbeds is a result of matrix shrinkage caused by gas desorption, which becomes a dominant factor on cleat permeability over the effective stress effect during reservoir production.

A permeability model previously developed by the authors has been re-visited in an effort to match the recently published field permeability data. The Shi and Durucan permeability model makes use of a stress-permeability relationship reported in the literature for an idealised geometry (matchsticks), in which the permeability varies exponentially with changes in the effective horizontal stress through the use of a cleat (pore) compressibility parameter. In this study, a stress-dependent cleat volume compressibility defined by an initial compressibility with a negative exponential decline rate was adopted. By tuning these two parameters, it was possible to achieve a close match to all the field permeability data by using a common set of reservoir properties (elastic properties and matrix shrinkage parameters) that are consistent with the available field and laboratory data in the literature.

The matching of the field permeability data in these two regions of the San Juan Basin has further validated the Shi and Durucan permeability model (with variable cleat volume compressibility). It has also provided theoretical support for the observed near-exponential growth behaviour of coalbed permeability in a producing reservoir. Furthermore, the model has shed new insights into the permeability behavior: 1) the exponential growth occurs when the reservoir pressure is reduced to a level generally below the permeability recovery pressure (the reservoir pressure at which the initial permeability is recovered); 2) the reservoir permeability in these two regions would remain relatively flat at reservoir pressures above the permeability recovery pressure.
Well Production Forecast in a Tight Gas Reservoir—Closing the Loop With Model-Based Predictions in Jonah Field, Wyoming
Authors: Iwere F. O. , Gao H. , Luneau B.
Published: April 2009

This paper presents a closed-loop reservoir study in tight gas fluvial sands of the giant Jonah gas field located in the northwestern part of the Greater Green River Basin, Wyoming. It produces gas from the micro-darcy fluvial channel sandstones of the Upper Cretaceous Lance Formation after multistage hydraulic fracturing. Single sand body pay zones would not be commercially attractive.

Rigorous reservoir modeling and simulation workflows were employed to build a 3D flow model from geology, geophysics, petrophysics and engineering data and interpretation. The stacked, multi-pay, tight gas sandstone reservoirs and their overpressured conditions were modeled and the hydraulic fractures properties were derived from matching initial well performance. The model was calibrated with well and field performance data through 2006. The calibrated model was used to forecast well performance, estimate reserves; investigate optimal well spacing and infill-well patterns.

Production for old wells and infill wells completed during 2007 and 2008 which was not included in the model calibration is compared with our previously forecasted results. The comparison shows that the actual well production of most of the wells is close to our forecasted results. The production-validated results of this closed-loop study clearly demonstrate that well production and field performance can be forecasted using reservoir modeling and simulation in a highly heterogeneous reservoir. Rigorously-constructed reservoir model(s) help us test and determine optimal production techniques to maximize field production goals. It can be confidently used to reduce field development risk and maximize profits.
Controlling Bacteria in Recycled Production Water for Completion and Workover Operations
Authors: Tischler A. , Woodworth T. R. , Burton S. D. , Richards R. D.
Published: April 2009

Reusing flowback water and produced water from active wells becomes more and more important in today's oil and gas operations to control surface water volumes in order to keep surface water disposal costs (reinjection or trucking off the premises) to a minimum – especially in operations that do not require secondary lift support. However, reusing untreated produced and flowback water untreated in workover and completion operations can promote bacteria growth both above and below ground.

Water produced from oil and gas wells is a perfect environment for sulfate reducing bacteria (SRB) and acid forming bacteria (AFB) due to its anaerobic nature (< 2ppm O2 content) and high nutrients content (organics, free iron, etc.). Reuse of water introduces enough oxygen through regular pumping operations to allow aerobic bacteria to grow – mostly slime forming bacteria (SFB). The oxygen content is high enough for aerobic bacteria to grow but too low to kill anaerobic bacteria. The oxygen content will cause the anaerobic bacteria to stay in a biostatic state which does not kill them but prevents them from multiplying.

As soon as the bacteria find an environment that is conducive to their growth, they will become active again and start multiplying. The anaerobic environment in the formation is ideal for growth of bacteria like SRBs and AFBs. The aerobic environment of the wellbore is conducive for SFBs. The growth of SRBs will not only lead to Health and Safety (H&S) concerns due to increased sour gas or hydrogen sulfide (H2S) production but also to a slow souring of the formation. This also increase operation expenses due to added corrosion (H2S pitting, stress cracking etc) in surface and subsurface tubulars and related prevention expenses. Other challenges in production can be related to AFBs (pitting) and SFBs (emulsion like materials may form).

Various different methods can be applied to prevent bacteria growth and reduce operational expenses related to corrosion prevention, remediation of corrosion effects, and remediation of emulsion like produced fluids. This paper will take a closer look at the methods of aeration, chlorine based applications (sodium hypochlorite, calcium hypochlorite, and chlorine dioxide), and biocide application.

The different methods will be compared through laboratory tests, actual field application, and a rating system. The rating system incorporates environmental, health, and safety (EH&S) concerns, operational application/considerations, effectiveness of the method, and cost.

Each method will be discussed and the pros and cons presented. The pros and cons will be supported by laboratory and field data. The conclusion portion of the paper will give reasoning on why and how the current method of application was chosen and discuss future improvements and testing.
Maturity and Impedance Analyses of Organic-Rich Shales
Authors: Prasad Manika , Mba Kenechukwu C. , Elizabeth McEvoy T. , Batzle Michael L.
Published: April 2009

Organic-rich shales (ORS) need to be studied in detail to understand the provenance and the generation of oil from source rocks. In recent years, ORS have become interesting as important hydrocarbon resources as well. Successful exploration and production programs for ORS need reliable identification of the kerogen content and the maturity through indirect seismic methods. However, the seismic properties of kerogen are poorly understood and so, predictions about maturity and rock-kerogen systems remain a challenge. Assessment of maturity from indirect measurements can be greatly enhanced by establishing and exploiting correlations between physical properties, microstructure, and kerogen content.

In this paper we show correlations between the impedance microstructure of ORS and their maturity and elastic properties. We have used scanning acoustic microscopy to analyze and map the impedance microstructure in ORS. We quantified textural properties in the images and related these textural properties to maturity and to impedance from acoustic wave propagation measured at centimeter scales. This combined study of acoustic and microstructures of ORS give important insight in changes due to kerogen maturation. We introduce a modified porosity term and find that (i) there is a significant correlation between velocity and modified porosity of all ORS; (ii) Imaging and quantifying microscale impedance texture and contrast in the images allows us to correlate them with ultrasonic measurements on a cm-scale; and (iii) textural heterogeneity, elastic impedance, velocity, and density increase with increasing shale maturity.

In this paper, we show typical acoustic images of ORS and discuss possible methods to predict maturity from impedance based on understanding the changes due to maturity in well log response, core measurements, and microstructure of organic-rich shales. Our work has important bearing on developing successful production and stimulation methodologies.
Advances in Sand Jet Perforating
Authors: Dotson Thomas , Farr James , Findley Earle
Published: April 2009

Sand jet perforating (SJP) is a process that uses high pressure fluid slurry to perforate tubulars and cement within an oil or gas well, and simultaneously extend a cavity into the reservoir. SJP has its origins in the 1960s with many large scale commercial successes in several international venues. While the SJP process was a technical success at that time, it was not an economic success. Few advancements in technology were attempted until the late 1990s. Advances in metallurgy have allowed major re-designs of sand jet perforating tools and jet orifices. These advances coupled with improvements in pump liner design have made SJP more cost effective today. The use of coiled tubing as a conveyance method further allows fluid pressures to be increased, and higher pressure limits make the SJP process even more effective. Newer modular SJP tool designs ensure near limitless re-configuration of coiled tubing conveyed plugs, packers, hold-down tools, perforation, and fracturing tools for simultaneous use during completion and work-over operations.

Applications for Sand Jet Perforating technology include perforation and re-perforation of vertical and horizontal oil and gas wells and perforation and treatment of coal bed methane wells. SJP can also be used in conjunction with other technologies such as fresh water and foam fracturing and for enhanced performance resulting from chemical injection and acidization. Sand Jet Perforating provides an alternative to widely accepted wire-line or tubing conveyed explosive methods used in most fields today. Hundreds of documented successes are available to confirm that SJP increases communication between well bore and reservoir more effectively with less formation damage and is accomplished in fewer round trips in and out of the well bore than more widely used perforating methods. Added benefits are realized as perforating and fracturing can be accomplished nearly simultaneously with a common work string.

Several papers and studies have recently been published that document the many benefits of Sand Jet Perforating, and recent demand for these services is increasing. This paper discusses the benefits of using Sand Jet Perforating tools and explains some new designs that suggest a broader range of uses.
Effects of High Process-Zone Stress in Shale Stimulation Treatments
Authors: Ramurthy Muthukumarappan , Barree Robert D. , Broacha Earuch , Longwell John D. , Kundert Donald P. , Tamayo Cristina
Published: April 2009

Over the last few years shale plays across North America have received significant attention because of their revenue potential and the supplementary reserves they add to the U.S. natural-gas reserves. However, the flow capacity (i.e., permeability) of these shales is very low and, therefore, requires some sort of stimulation to make them economically viable. Problems during stimulation treatments can lead to "pressure outs" and screenouts. One of the main reasons that lead to "pressure outs" is high process-zone stress (PZS). With high PZS, the chance for pressuring out is higher than screenout (i.e., one can still flush the job at lower rates provided the sand has not settled in the wellbore). The purpose of this work is to show the effects of high PZS in shale stimulation treatments and the associated production from such zones.

Examples are presented from three shale wells in the Rocky Mountain region. Well A provides examples from the Gothic and Hovenweep shales, while Well B consists of an example from the Mancos shale. A Diagnostic Fracture-Injection Test (DFIT) was performed in the Gothic and Hovenweep shales before the stimulation treatment, and the results obtained point to very high PZS. History-match analysis of the Gothic and Upper or Main Hovenweep stimulation treatments using a grid-oriented, fully functional three-dimensional (3D) fracture simulator confirmed the same. Solutions are provided to overcome this effect and successfully "place" the stimulation treatment. However, the production associated with such high PZS zones is not very encouraging. Well A is temporarily abandoned because of poor production, and the Mancos shale well with high PZS (Well B) is one of the poor producers in the field. Finally, another example (Well C) from a successful Mancos test is also included in this work to show the difference in production between high- and low-PZS zones. This paper discusses methods for early identification of high-PZS shale zones to possibly avoid stimulation treatments in order to pay more attention to the low-PZS zones that require stimulation.