bluuebunny/crossref_metadata_2025 huggingface dataset:
Myelination and Axonal Electrical Activity Modulate the Distribution and Motility of Mitochondria at CNS Nodes of Ranvier
Authors: Ohno Nobuhiko , Kidd Grahame J. , Mahad Don , Kiryu-Seo Sumiko , Avishai Amir , Komuro Hitoshi , Trapp Bruce D.
Published: May 2011

Energy production presents a formidable challenge to axons as their mitochondria are synthesized and degraded in neuronal cell bodies. To meet the energy demands of nerve conduction, small mitochondria are transported to and enriched at mitochondrial stationary sites located throughout the axon. In this study, we investigated whether size and motility of mitochondria in small myelinated CNS axons are differentially regulated at nodes, and whether mitochondrial distribution and motility are modulated by axonal electrical activity. The size/volume of mitochondrial stationary sites was significantly larger in juxtaparanodal/internodal axoplasm than in nodal/paranodal axoplasm. With three-dimensional electron microscopy, we observed that axonal mitochondrial stationary sites were composed of multiple mitochondria of varying length, except at nodes where mitochondria were uniformly short and frequently absent altogether. Mitochondrial transport speed was significantly reduced in nodal axoplasm compared with internodal axoplasm. Increased axonal electrical activity decreased mitochondrial transport and increased the size of mitochondrial stationary sites in nodal/paranodal axoplasm. Decreased axonal electrical activity had the opposite effect. In cerebellar axons of the myelin-deficient rat, which contain voltage-gated Na+channel clusters but lack paranodal specializations, axonal mitochondrial motility and stationary site size were similar at Na+channel clusters and other axonal regions. These results demonstrate juxtaparanodal/internodal enrichment of stationary mitochondria and neuronal activity-dependent dynamic modulation of mitochondrial distribution and transport in nodal axoplasm. In addition, the modulation of mitochondrial distribution and motility requires oligodendrocyte–axon interactions at paranodal specializations.
Excitatory Modulation in the Cochlear Nucleus through Group I Metabotropic Glutamate Receptor Activation
Authors: Chanda Soham , Xu-Friedman Matthew A.
Published: May 2011

Activation of group I metabotropic glutamate receptors (mGluRs) has been suggested to modulate development of auditory neurons. However, the acute effects of mGluR activation on physiological response properties are unclear. To address this, we studied the effects of mGluRs in bushy cells (BCs) of the mammalian anteroventral cochlear nucleus (AVCN). Activation of mGluRs with dihydroxyphenylglycine (DHPG) caused depolarization of BCs in mice as old as P42, but did not affect neurotransmitter release by presynaptic auditory nerve (AN) fibers. Application of mGluR antagonists indicated that mGluRs are tonically active, and are highly sensitive to small elevations in ambient glutamate by the glutamate reuptake blockerthreo-β-benzyloxyaspartic acid (TBOA). mGluR-mediated depolarization enhanced the firing probability in response to AN stimulation, and reduced the latency and jitter. Furthermore, excitation through postsynaptic mGluRs can significantly counterbalance the inhibitory effects of presynaptic GABABreceptors. Thus, interaction between these two modulatory pathways may provide additional flexibility for fine-tuning the BC relay.
Synapsin I Is an Oligomannose-Carrying Glycoprotein, Acts As an Oligomannose-Binding Lectin, and Promotes Neurite Outgrowth and Neuronal Survival When Released via Glia-Derived Exosomes
Authors: Wang Shiwei , Cesca Fabrizia , Loers Gabriele , Schweizer Michaela , Buck Friedrich , Benfenati Fabio , Schachner Melitta , Kleene Ralf
Published: May 2011

Oligomannosidic glycans play important roles in nervous system development and function. By performing a phage display screening with oligomannose-specific antibodies, we identified an oligomannose-mimicking peptide that was functionally active in modulating neurite outgrowth and neuron–astrocyte adhesion. Using the oligomannose-mimicking peptide in crosslinking experiments, synapsin I was identified as a novel oligomannose-binding protein in mouse brain. Further analyses not only verified that synapsin I is an oligomannose-binding lectin, but also indicated that it is a glycoprotein carrying oligomannose and Lewisx. We also found that synapsin I is expressed in glia-enriched cultures and is released from glial cells via exosomes. Incubation of glial-derived exosomes in the presence of high KCl concentrations or subjecting glial cell cultures to either oxygen/glucose deprivation or hydrogen peroxide resulted in release of synapsin I from exosomes. Application of synapsin I promoted neurite outgrowth from hippocampal neurons and increased survival of cortical neurons upon hydrogen peroxide treatment or oxygen/glucose deprivation. Coculture experiments using wild-type hippocampal neurons and wild-type or synapsin-deficient glial cells showed enhanced neurite outgrowth when synapsin was expressed by glial cells. Synapsin-induced neurite outgrowth was dependent on oligomannose on synapsin I and the neural cell adhesion molecule NCAM at the neuronal cell surface. The data indicate that, under conditions of high neuronal activity and/or oxidative stress, synapsin can be released from glial-derived exosomes and promotes neurite outgrowth and neuronal survival by modulating the interactions between glia and neurons.
Nuclear Factor Erythroid 2-Related Factor 2 Facilitates Neuronal Glutathione Synthesis by Upregulating Neuronal Excitatory Amino Acid Transporter 3 Expression
Authors: Escartin Carole , Joon Won Seok , Malgorn Carole , Auregan Gwennaelle , Berman Ari E. , Chen Pei-Chun , Déglon Nicole , Johnson Jeffrey A. , Won Suh Sang , Swanson Raymond A.
Published: May 2011

Astrocytes support neuronal antioxidant capacity by releasing glutathione, which is cleaved to cysteine in brain extracellular space. Free cysteine is then taken up by neurons through excitatory amino acid transporter 3 [EAAT3; also termed Slc1a1 (solute carrier family 1 member 1)] to supportde novoglutathione synthesis. Activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) pathway by oxidative stress promotes astrocyte release of glutathione, but it remains unknown how this release is coupled to neuronal glutathione synthesis. Here we evaluated transcriptional regulation of the neuronal cysteine transporter EAAT3 by the Nrf2-ARE pathway. Nrf2 activators and Nrf2 overexpression both produced EAAT3 transcriptional activation in C6 cells. A conserved ARE-related sequence was found in theEAAT3promoter of several mammalian species. This ARE-related sequence was bound by Nrf2 in mouse neuronsin vivoas observed by chromatin immunoprecipitation. Chemical activation of the Nrf2-ARE pathway in mouse brain increased both neuronal EAAT3 levels and neuronal glutathione content, and these effects were abrogated in mice genetically deficient in either Nrf2 or EAAT3. Selective overexpression of Nrf2 in brain neurons by lentiviral gene transfer was sufficient to upregulate both neuronal EAAT3 protein and glutathione content. These findings identify a mechanism whereby Nrf2 activation can coordinate astrocyte glutathione release with neuronal glutathione synthesis through transcriptional upregulation of neuronal EAAT3 expression.
Olfactory Trace Conditioning inDrosophila
Authors: Galili Dana Shani , Lüdke Alja , Galizia C. Giovanni , Szyszka Paul , Tanimoto Hiromu
Published: May 2011

The neural representation of a sensory stimulus evolves with time, and animals keep that representation even after stimulus cessation (i.e., a stimulus “trace”). To contrast the memories of an odor and an odor trace, we here establish a rigorous trace conditioning paradigm in the fruit fly,Drosophila melanogaster. We modify the olfactory associative learning paradigm, in which the odor and electric shock are presented with a temporal overlap (delay conditioning). Given a few-second temporal gap between the presentations of the odor and the shock in trace conditioning, the odor trace must be kept until the arrival of electric shock to form associative memory. We found that memories after trace and delay conditioning have striking similarities: both reached the same asymptotic learning level, although at different rates, and both kinds of memory have similar decay kinetics and highly correlated generalization profiles across odors. In search of the physiological correlate of the odor trace, we usedin vivocalcium imaging to characterize the odor-evoked activity of the olfactory receptor neurons in the antennal lobe. After the offset of odor presentation, the receptor neurons showed persistent, odor-specific response patterns that lasted for a few seconds and were fundamentally different from the response patterns during the stimulation. Weak correlation between the behavioral odor generalization profile in trace conditioning and the physiological odor similarity profiles in the antennal lobe suggest that the odor trace used for associative learning may be encoded downstream of the olfactory receptor neurons.
Mind the Gap: Olfactory Trace Conditioning in Honeybees
Authors: Szyszka Paul , Demmler Christiane , Oemisch Mariann , Sommer Ludwig , Biergans Stephanie , Birnbach Benjamin , Silbering Ana F. , Galizia C. Giovanni
Published: May 2011

Trace conditioning is a form of classical conditioning, where a neutral stimulus (conditioned stimulus, CS) is associated with a following appetitive or aversive stimulus (unconditioned stimulus, US). Unlike classical delay conditioning, in trace conditioning there is a stimulus-free gap between CS and US, and thus a poststimulus neural representation (trace) of the CS is required to bridge the gap until its association with the US. The properties of such stimulus traces are not well understood, nor are their underlying physiological mechanisms. Using behavioral and physiological approaches, we studied appetitive olfactory trace conditioning in honeybees. We found that single-odor presentation created a trace containing information about odor identity. This trace conveyed odor information about the initial stimulus and was robust against interference by other odors. Memory acquisition decreased with increasing CS–US gap length. The maximum learnable CS–US gap length could be extended by previous trace-conditioning experience. Furthermore, acquisition improved when an additional odor was presented during the CS–US gap. Using calcium imaging, we tested whether projection neurons in the primary olfactory brain area, the antennal lobe, contain a CS trace. We found odor-specific persistent responses after stimulus offset. These post-odor responses, however, did not encode the CS trace, and perceived odor quality could be predicted by the initial but not by the post-odor response. Our data suggest that olfactory trace conditioning is a less reflexive form of learning than classical delay conditioning, indicating that odor traces might involve higher-level cognitive processes.
Long-Term Effects of Repetitive Transcranial Magnetic Stimulation on Markers for Neuroplasticity: Differential Outcomes in Anesthetized and Awake Animals
Authors: Gersner Roman , Kravetz Elena , Feil Jodie , Pell Gaby , Zangen Abraham
Published: May 2011

Long-term effects of repetitive transcranial magnetic stimulation (rTMS) have been associated with neuroplasticity, but most physiological studies have evaluated only the immediate effects of the stimulation on neurochemical markers. Furthermore, although it is known that baseline excitability state plays a major role in rTMS outcomes, the role of spontaneous neural activity in metaplasticity has not been investigated. The first aim of this study was to evaluate and compare the long-term effects of high- and low-frequency rTMS on the markers of neuroplasticity such as BDNF and GluR1 subunit of AMPA receptor. The second aim was to assess whether these effects depend on spontaneous neural activity, by comparing the neurochemical alterations induced by rTMS in anesthetized and awake rats. Ten daily sessions of high- or low-frequency rTMS were applied over the rat brain, and 3 d later, levels of BDNF, GluR1, and phosphorylated GluR1 were assessed in the hippocampus, prelimbic cortex, and striatum. We found that high-frequency stimulation induced a profound effect on neuroplasticity markers; increasing them in awake animals while decreasing them in anesthetized animals. In contrast, low-frequency stimulation did not induce significant long-term effects on these markers in either state. This study highlights the importance of spontaneous neural activity during rTMS and demonstrates that high-frequency rTMS can induce long-lasting effects on BDNF and GluR1 which may underlie the clinical benefits of this treatment in neuroplasticity-related disorders.
Assessment of Epidermal Growth Factor Receptor and K-Ras Mutation Status in Cytological Stained Smears of Non-Small Cell Lung Cancer Patients: Correlation with Clinical Outcomes
Authors: Lozano Maria D. , Zulueta Javier J. , Echeveste Jose I. , Gúrpide Alfonso , Seijo Luis M. , Martín-Algarra Salvador , Barrio Anabel , Pio Ruben , Idoate Miguel Angel , Labiano Tania , Perez-Gracia Jose Luis
Published: May 2011

Objective.

Epidermal growth factor receptor (EGFR) and K-ras mutations guide treatment selection in non-small cell lung cancer (NSCLC) patients. Although mutation status is routinely assessed in biopsies, cytological specimens are frequently the only samples available. We determined EGFR and K-ras mutations in cytological samples.

Methods.

DNA was extracted from 150 consecutive samples, including 120 Papanicolau smears (80%), 10 cell blocks (7%), nine fresh samples (6%), six ThinPrep® tests (4%), and five body cavity fluids (3.3%). Papanicolau smears were analyzed when they had >50% malignant cells. Polymerase chain reaction and direct sequencing of exons 18–21 of EGFR and exon 2 of K-ras were performed. EGFR mutations were simultaneously determined in biopsies and cytological samples from 20 patients. Activity of EGFR tyrosine kinase inhibitors (TKIs) was assessed.

Results.

The cytological diagnosis was adenocarcinoma in 110 samples (73%) and nonadenocarcinoma in 40 (27%) samples. EGFR mutations were identified in 26 samples (17%) and K-ras mutations were identified in 18 (12%) samples. EGFR and K-ras mutations were mutually exclusive. In EGFR-mutated cases, DNA was obtained from stained smears in 24 cases (92%), pleural fluid in one case (4%), and cell block in one case (4%). The response rate to EGFR TKIs in patients harboring mutations was 75%. The mutation status was identical in patients who had both biopsies and cytological samples analyzed.

Conclusion.

Assessment of EGFR and K-ras mutations in cytological samples is feasible and comparable with biopsy results, making individualized treatment selection possible for NSCLC patients from whom tumor biopsies are not available.
Phase III Multicenter Clinical Trial of the Sialyl-TN (STn)-Keyhole Limpet Hemocyanin (KLH) Vaccine for Metastatic Breast Cancer
Authors: Miles David , Roché Henri , Martin Miguel , Perren Timothy J. , Cameron David A. , Glaspy John , Dodwell David , Parker Joanne , Mayordomo José , Tres Alejandro , Murray James Lee , Ibrahim Nuhad K. ,   the Theratope® Study Group
Published: May 2011

Purpose.

This double-blind, randomized, phase III clinical trial evaluated time to progression (TTP) and overall survival in women with metastatic breast cancer (MBC) who received sialyl-TN (STn) keyhole limpet hemocyanin (KLH) vaccine. Secondary endpoints included vaccine safety and immune response.

Experimental design.

The study population consisted of 1,028 women with MBC across 126 centers who had previously received chemotherapy and had had either a complete or a partial response or no disease progression. All women received one-time i.v. cyclophosphamide (300 mg/m2) 3 days before s.c. injection of 100 μg STn-KLH plus adjuvant (treatment group) or 100 μg KLH plus adjuvant (control group) at weeks 0, 2, 5, and 9. Subsequently, STn-KLH without adjuvant or KLH without adjuvant was then administered monthly for 4 months, and then quarterly until disease progression, without cyclophosphamide.

Results.

STn-KLH vaccine was well tolerated; patients had mild to moderate injection-site reactions and reversible flu-like symptoms. Week-12 antibody testing revealed high specific IgG titers and a high rate of IgM-to-IgG seroconversion; the median IgG titers in STn-KLH recipients were 320 (anti-ovine submaxillary mucin) and 20,480 (anti-STn), with no detectable antimucin antibodies in the control group. The TTP was 3.4 months in the treatment group and 3.0 months in the control group. The median survival times were 23.1 months and 22.3 months, respectively.

Conclusions.

Although STn-KLH was well tolerated in this largest to date metastatic breast cancer vaccine trial, no overall benefit in TTP or survival was observed. Lessons were learned for future vaccine study designs.
Selective Application of Routine Preoperative Axillary Ultrasonography Reduces Costs for Invasive Breast Cancers
Authors: Turaga Kiran K. , Chau Alec , Eatrides Jennifer M. , Kiluk John V. , Khakpour Nazanin , Laronga Christine , Lee M. Catherine
Published: May 2011

Learning Objectives

After completing this course, the reader will be able to: Identify patients likely to benefit from preoperative axillary ultrasound.Define the clinical implications of a preoperative axillary ultrasound and FNA in patient care.

CME This article is available for continuing medical education credit at CME.TheOncologist.com

Purpose.

Preoperative axillary sonography with fine needle aspiration (FNA) in patients with invasive breast cancer identifies patients with nodal metastasis who can be spared further surgery. Indiscriminate use of the diagnostic modality can increase costs and yield inaccurate results. We evaluate the costs associated with the use of highly sensitive axillary ultrasonography in patients with stage ≥T2 tumors.

Patients and Methods.

We constructed a decision analysis tree using TreeAge Pro 2009 software comparing direct hospital charges between patients with and without routine use of axillary ultrasound. Base case estimates were derived from our institutional data and compared with those derived from the literature. One- and two-way sensitivity analyses were performed to check the validity of our inferences.

Results.

We found that, for the base case estimate with 35% lymph node positivity in stage ≥T2 tumors and sensitivity of the axillary ultrasound set at 86% with a specificity of 40%, the strategy to perform preoperative axillary ultrasound yielded rollback costs of $15,215, compared with $15,940 for surgery plus sentinel lymph node biopsy (cost difference, $725 per patient favoring axillary ultrasound). On two-way sensitivity analysis, the cost benefit for axillary ultrasound was not seen in patients with a low risk for nodal metastasis.

Conclusion.

The adoption of routine preoperative axillary sonography with FNA is a lower-cost strategy than conventional strategies in patients with stage ≥T2 invasive breast cancer.
Coping with Being New in the Hematology/Oncology Department
Authors: Then Cornelia
Published: May 2011

A perspective on patients in the hematology/oncology department is presented from a newcomer's point of view.
Hydropower and panel engineers – a lasting legacy. Part 2
Authors: Cowie John
Published: May 2011

This is the second part of the 11th Geoffrey Binnie lecture presented at the 16th biennial BDS conference held at Strathclyde University in 2010. The first part was published in the previous edition of Dams and Reservoirs. The lecture is about the development of hydroelectric power in Scotland focusing on the careers of the panel engineers involved.
Reservoir safety in Scotland – The Reservoirs (Scotland) Bill – an overview
Authors: Macdonald Alex
Published: May 2011

The Reservoirs (Scotland) Bill was passed by the Scottish parliament in March 2011. The Bill sets out the requirements for the registration, control and enforcement of reservoir safety in Scotland in the future. This article summarises some of the major differences compared to current legislation. The most significant of these is the move to a risk-based approach to future inspection and supervision, all reservoirs with a minimum retained volume of 10 000 m3 being covered by the Bill requirements. There are also some important changes to the role of the supervising engineer for the reservoir, in the requirements to identify regular maintenance required in the interests of safety, and in the process for monitoring and certification of safety measures. The Bill also introduces new requirements for mandatory incident reporting and for the preparation of on-site emergency plans. The article provides an indicative timescale for phased enactment of the legislation.
Biohydrogen from sugar industry waste and sewage
Authors: Balin Radjaram , Raman Saravanane
Published: May 2011

Anaerobic co-digestion of press mud and sewage for biohydrogen production was performed in an upflow anaerobic sludge blanket reactor (20 l). Experiments were conducted under three dilution ratios 1∶7·5 (series I), 1∶10 (series II) and 1∶12·5 (series III) by diluting press mud with sewage and filtering all fibres. Total solids, dissolved solids, suspended solids, volatile solids, volatile dissolved solids, volatile suspended solids, chemical oxygen demand, volatile fatty acid and alkalinity were tested at regular time intervals. Daily biohydrogen produced and hydrogen percentage were also monitored. A maximum biohydrogen yield of 7985 ml/day at the rate of 4990 ml/kg press mud added with a specific biohydrogen production rate of 187 ml/g volatile solids reduced/day was evaluated in series II (dilution 1∶10). A volatile suspended solids/total suspended solids ratio of 0·82–0·92 and a volatile fatty acid/alkalinity ratio of 0·01 were estimated to be the optimum parameters for press mud co-digestion at a pH of 5–6 under ambient conditions.
Briefing: Concentrating solar power compared with flat-plate collectors, south-east Asia
Authors: Napier-Moore Philip
Published: May 2011

Since late 2009 Thailand has been experiencing a surge in large-scale deployment of solar power. Over 3 GW of solar power plants have been proposed to the national electricity authorities under the concessional power tariff, equivalent to approximately 10% of current installed national power generation capacity. Operating solar plants to date mainly use ‘flat-plate collector’ photovoltaic panels. However, a significant majority of the new proposed plants are based on various concentrating solar thermo-electric power technologies, where moving reflective collector surfaces concentrate the direct component of sunlight onto a thermal receiver, for subsequent conversion of heat to electric power. This briefing article compares key solar technology types for application in climates similar to Thailand, including consideration of newly commercial technologies.
Briefing: Good news, bad news: the UK public spending review
Authors: Bedford Mark
Published: May 2011

The effects of the UK’s public spending review and national infractructured plan announcements on a range of issues – from the renewable heat incentive and feed-in tariffs to investment in carbon capture and storage and changes to the carbon reduction commitment scheme – are considered in this article. The UK government has pledged to ‘prioritise investment ruthlessly in green energy infrastructure’. It has committed to invest £200 billion in economic infrastructure over the next five years, the majority in transport and energy. Imaginative new thinking is needed on infrastructure investment and sustainable energy, supported by viable ways of making it happen.
Providing community energy for the London 2012 Olympic Park
Authors: Maybank Ruari , Carr Mike , Guest Ian , Laidlaw Bruce
Published: May 2011

The UK Olympic Delivery Authority is responsible for providing infrastructure to serve the biggest sporting event in the world and support the long-term regeneration of east London. The scale of development for the London 2012 Olympic and Paralympic Games presented an opportunity to implement a sustainable, ‘low carbon’ development, central to which are two large energy centres and an extensive district heating and cooling network. This paper describes the challenges to implementing the community energy network and how these have been overcome to deliver utilities i#nfrastructure to a tight programme and with significant private sector investment.
Lessons learnt from recent nuclear build projects
Authors: Garnsey Richard , Nickson Ian , Joyce Malcom J.
Published: May 2011

The results of a recent study into the lessons learnt from recent nuclear build projects are described. Six projects have been investigated by means of literature review and interview with expertise on these projects. The results of this research have been analysed in terms of the principal engineering issues that will benefit future new-build nuclear projects in the UK. Five key lessons have emerged including: that follow-on replica projects are cheaper than first-of-a-kind projects; the design must be mature and licensing issues resolved before the start of construction; a highly qualified team must be established to develop the design, secure the safety case and plan the procurement and build schedules in collaboration with the main contractors; subcontractors must be of high quality and experienced in nuclear construction or otherwise taught the necessary skills; good communications with the community local to the site must be established and maintained.
Compaction of fills in land reclamation by rapid impact
Authors: Watts Ken S. , Cooper Adrian
Published: May 2011

It is necessary to apply high levels of energy to fill materials, using heavy compaction plant with material placed in thin layers, to achieve performance that is compatible with most development specifications. Site geometry or programme constraints often render this traditional approach inappropriate. A technique originally developed for military use and hitherto applied in a limited range of civil projects in the UK has been adopted internationally for a much wider range of materials and applications. The rapid impact compactor has been used to successfully compact a wide range of both placed and in situ granular materials, including rockfills, as well as to stabilise naturally occurring loess sand and silt deposits in seismic zones. A brief explanation of the technique is followed by a number of case histories from around the world, in which the design, execution and verification of compaction are presented. As with any compaction, quality control is of paramount importance, and in-built process controls and typical field testing are described. The advantages of this technique for thicker layer compaction and discrete small area compaction are highlighted.
Field permeability at shallow depth in a compacted fill
Authors: Li Lisa J. H. , Zhang Limin , Kwong Ben C. P.
Published: May 2011

This paper presents a series of field double-ring infiltration tests (DRTs) for investigating the hydraulic conductivity of a compacted silty clay fill that contains some desiccation cracks. These field tests were conducted at three different depths in the fill, to characterise the variations of conductivity with depth. The hydraulic conductivity of the fill was also measured in the laboratory on block samples using a three-directional permeability cell (sample size: 200 mm × 200 mm × 200 mm) and a one-dimensional permeameter (sample size: 70 mm in diameter and 45 mm high). A perched water table was detected in the fill using tensiometers shortly after the start of each DRT, showing the presence of preferential flow paths in the fill. The hydraulic conductivity decreases with increasing depth. The larger hydraulic conductivity of the surface soil indicates the possible presence of macropores and cracks at shallow depths of the fill. The coefficients of variation of the hydraulic conductivity measured from the DRTs (influence volume: 300 mm in diameter and 450 mm high) and the three-directional permeability cell tests are smaller than those measured from the small-size, one-dimensional permeameter tests. The variability of the measured hydraulic conductivity increases as the sample size decreases.
Hydrolysis and Precipitation of Polyacrylamides in Hard Brines at Elevated Temperatures
Authors: Moradi-Araghi Ahmad , Doe Peter H.
Published: May 2011

Laboratory data are used to show that commercial polyacrylamides hydrolyze to an equilibrium degree that depends on the temperature of hydrolysis but is largely independent of the brine composition. At greater than 20 ppm hardness levels, polyaerylamide solutions pass through a sharp cloud point as their temperature is raised. This cloud-point temperature depends primarily on the hardness level of the brine and the degree of hydrolysis of the polymer, with lesser dependency on polymer molecular weight and polymer concentration. Indications are that these cloudy solutions cause plugging of porous media. Therefore, a polymer solution is potentially useful only below its cloud-point temperature. For application in a given reservoir, the temperature and frequently the hardness of the water are fixed. If a polyaerylamide hydrolyzes at reservoir conditions to where its cloud point in the field water falls below the reservoir temperature, it is not suitable for polymer flooding in that reservoir.

Cloud-point data, in conjunction with rate-of-hydrolysis data, indicate a "safe" limit of approximately 75°C [167°F] for brines containing 2,000 ppm hardness and above, increasing to around 88°C [190°F] at 500 ppm, 96°C [205°F] at 270 ppm, and at least 204°C [400°F] at 20 ppm and below. Most unsoftened injection waters will limit polyacrylamide use to below 93 °C [200°F]. Most produced waters will limit applicability to below 82°C [180°F].
Azimuth Preservation in Pre-Stack Time Migration using Offset Vector Tiles
Authors: Rowe R. Wilson , Al-Najjar Mohammed H.
Published: May 2011

Wide azimuth (WAZ) land 3D seismic recording geometry typically generates data that is spatially well sampled with a wide range of azimuths and a regular distribution of offsets at those azimuths. Unfortunately, the azimuth information is lost in the pre-stack time migration (PSTM) using traditional processing techniques. Preserving azimuth (the angle measured clockwise from north of a geometric ray that starts at the source point and passes through the receiver point) and offset (the distance between a trace's source and receiver points) information in image gathers is desirable so that the attributes can be used in the detection of horizontal transverse isotropy (HTI), which can provide insight into reservoir fracture orientation. This paper describes the Offset Vector Tile (OVT) processing approach, a new industry trend in seismic data processing to preserve shot-receiver azimuth on image gathers.

OVT, also commonly refered to as Common Offset Vector (COV) gathers, are minimal data sets that are linked to patch dimensions and repeat patterns observed in WAZ 3D recording geometry. The OVT method is used to produce single fold pre-stack data volumes that cover the full 3D survey area. All of the traces in a single OVT volume share similar offset and azimuth attributes. Additionally, they provide new opportunities for noise attenuation, trace interpolation, and data regularization. These signal enhancements lead to less migration noise and an overall image improvement. Migration is performed on all of the OVT volumes resulting in an equivalent number of pre-stack migrated data sets, each with their respective azimuth and offset preserved. Traces from each common image point of the numerous migrated OVT volumes are grouped to form image gathers, which can then be analyzed for azimuthal anisotriopy.

The OVT method is demonstrated as a case history on a WAZ land 3D survey in the Eastern Province of Saudi Arabia.
Workflow Automation of a 5-Stage Gate Upstream Technology Pilot Process
Authors: Alsayari Saleh M. , Lauritzen Jon E. , Alqurtas Abdulrahman M.
Published: May 2011

The introduction of new completion technologies in Saudi Aramco has historically undertaken a lengthy manual process for approval of use in Saudi Aramco wells. During this process, Petroleum Engineers develop and support production technologies based on analysis of lab and field studies. When the technology is deemed fit for purpose and beneficial to Saudi Aramco, the analysis is formalized and processed through management. Specialist engineers steward these assessment studies through multiple parties for their input. Because the process is manual and inconsistent, process and technology reliability — along with project time duration — cannot be easily estimated and quality assured. The solution is to automate, simplify and optimize the technology piloting process, by introducing a standardized 5-Stage Gate process, and implementing it through an electronic workflow system. The new solution will improve process transparency, tracking and monitoring. It also strengthens the organization's commitment in ensuring transparency and accountability; thus enabling a fair competitive market for technology introduction.
The Rock Physicochemical Basis for Time-Lapse Seismic Reservoir Monitoring of CO2 Injection
Authors: Vanorio Tiziana , Nur Amos , Diaz Elizabeth
Published: May 2011

This paper springs from a series of laboratory experiments and high-resolution imaging techniques assessing the changes in microstructure, transport, and seismic properties of brine-saturated sandstones and carbonates when injected with CO2. Results show that the injection of CO2 into a brine-rock system induces chemo-mechanical mechanisms, which permanently change the rock frame. The injection of CO2 into brine-saturated-sandstones induces salt precipitation primarily at grain contacts and/or within small pore throats. Salt precipitation decreases permeability and increases P- and S- wave velocities particularly in sandstones characterized by porosity lower than 10%. On the other hand, the injection of CO2-rich brine into carbonates induces dissolution of the microcrystalline matrix (i.e., micrite) leading to porosity enhancement. Dissolution counteracts and overwhelms a pressure-dependent, chemo-mechanical creeping of the rock leading to compaction. The overall result is the decrease of the elastic moduli of the dry rock frame. These findings demonstrate that monitoring the time-lapse seismic response of chemically stimulated systems is far from being a pure fluid-substitution problem.
Non-Linear Model for Evaluation of Elastomer Seals Subjected to Differential Pressure
Authors: Al-Kharusi M.S.M. , Qamar S.Z. , Pervez T. , Akhtar M.
Published: May 2011

Abstract

The present paper discusses performance evaluation of swelling elastomer seals used in oil well applications under different field conditions. Swelling elastomers are a new type of advanced polymers, and have started to play an important role in improving existing wells, and in aiding oil recovery from difficult or abandoned fields. On the other hand, failure of these swell packers can lead to significant losses in terms of time and money. Performance evaluation of swelling-elastomer packers and other sealing elements prior to being put to use is therefore critically important. Theoretical investigation of the elastomer seal bonded between a metal tube and a rigid casing is carried out in the present paper. Numerical modeling and simulation for swelling-elastomer seals is also conducted using a Finite Element (FE) package such as ABAQUS. All Theoretical and numerical results of this study will help in predicting the seal behavior under different well conditions and the parameter that will affect on the sealing performance. Also, the study investigates both the effect of the material and geometrical properties of the elastomer on its sealing performance under different loading conditions. For the sealing environment, the study investigates the effect of radial strain (tubular expansion ratio) and the annular fluid pressure on the sealing performance under different seal geometries.

Introduction

Due to the continued forecast of increasing energy demand (oil and gas in particular), oil companies are stepping up their efforts in meeting the global demand. Drilling to increasing depths and producing from difficult reservoirs are already posing serious challenges to the petroleum development industry. Apart from this, there is a continued effort towards performance improvement, cost reduction and innovation for new tools and techniques to make the dream of a mono-bore diameter well a reality. Solid expandable tubular (SET) technology achieved quite a few milestones in this direction.
Extending the Life of a Mature Oil Field by Applying Innovative Squeeze Cementing Solutions
Authors: Neto N. Bianchi , Salehpour A. , Hadiaman F. , Biyanni H. M. , Jamal M. N. , Setyawan H.
Published: May 2011

After decades of field and laboratory studies, when compared to primary cementing, squeeze cementing defies standardization as a general practice. Each candidate for remedial cementing presents a unique challenge to the engineer, therefore, to address the variety of problems that may occur, a wide range of techniques has been developed combining placement methods, specific slurry formulations, and execution procedures.

Recent advancement in workover techniques in brown fields which requires well intervention without pulling out or replacing the existing completion mostly for economic reasons, have added extra complications to the remedial cementing operations that makes the job success more challenging. It is a multidisciplinary field requiring knowledge and skills in geo-mechanics, fluid mechanics, and of course, cement-slurry systems.

Handil field is a giant mature oil field in Indonesia that has been producing since 1975 with the current recovery factor of 49% for oil and 57% for gas. Cumulatively, the total oil produced is around 855 MMstb and gas around 1.68 Tcf with the current production of oil at 20,000 bopd, gas at 75 mmscfd and water at 130,000 bwpd. Applying enhanced oil recovery techniques, infill well drilling and light workover operations performed on existing wells are key elements to maintain field production.

This paper outlines the field study analysis with the focus of improving the squeeze cementing success rate from the previous campaigns and will cover innovative solutions specially a novel placement technique that was adopted on a recent campaign. Successful results helped the operator to extend the life of the mature field by maintaining the production at its best level. Also a case history will be covered for the aim of better understanding the challenges being faced for properly isolating the compartmentalized sand reservoirs with different characteristics where proper analysis and innovative approach helped the operator achieving the objectives.
Accurate Prediction of Pressure Drop in Two-Phase Vertical Flow Systems using Artificial Intelligence
Authors: Al-Shammari Ahmed
Published: May 2011

One of the significant parameters affecting flow rate in oil production wells is the pressure drop between the well bottom-hole and tubing head. The pressure drop calculation in two-phase flow systems is very complicated due to the variations in gas and liquid flow rates across the two-phase flow stream. As the pressure of crude decreases while climbing a well tubular, more gas comes out of solution. This gradual increase in gas volumes leads to the reduction of liquid slip velocity and creating new flow patterns that are not only different in shape, but also complicated in pressure drop calculations. To overcome this difficulty in calculating pressure drop in two-phase flow systems, scientists came up with two main approaches: flow correlations and mechanistic models. These two approaches are applicable within certain conditions and their accuracy in pressure drop prediction degrades outside their design boundary ranges.

The raising popularity of Artificial Intelligence (AI) techniques during the past two decades proved that AI can be an alternative solution to many of the complicated problems where physics and classic statistics fail to provide satisfactory solutions. These techniques applied in different upstream fields have provided fast, robust and reliable numerical models in a variety of areas, e.g., geological modeling, reservoir engineering, petrophysics and well testing. This paper describes the utilization of Fuzzy Logic, which is one of the famous AI techniques, in predicting flowing bottom-hole pressure in oil producer wells. Real well testing data from the Middle East were used in constructing the Fuzzy Logic model. After training the model using 596 well testing data samples, it was successfully able to predict the flowing bottom-hole pressure at 199 well testing samples with an average absolute error of 4.9%. A comparison analysis was conducted to evaluate multiple flow correlation in predicting flowing bottom-hole pressure and compare their results with the developed Adaptive Neuro-Fuzzy Inference System (ANFIS) model.
Fracture Imaging Using Azimuthal Prestack Depth Migration
Authors: Sliz Krzysztof (Kris)
Published: May 2011

A major uncertainty in fracture analysis based on the azimuthally variant seismic velocities is the interference from structural effects. Structural dip induces azimuthal variation in velocity, which can mask the influence on travel–times caused by the presence of fractures. In situations where the subsurface geology is complex, Prestack Depth Migration (PreSDM) should be used to correct for the dip prior to the azimuthal velocity analysis. PreSDM is sensitive to velocity variation, thereby making it a good tool for detection of subtle velocity changes. This paper focuses on a fracture detection methodology using a 3D azimuthal depth imaging workflow. The workflow presented here utilizes scanning of azimuthally dependent residual moveout volumes for three-dimensional (3D) mapping of zones with a higher probability of fractures. This analysis can also be used to help determine the fracture style (single or multiple set of fractures). The workflow was successfully applied to wide azimuth, high-fold land seismic data acquired over a fractured formation in the northern part of Saudi Arabia.
Facilities Planning Using Coupled Surface and Reservoir Simulation Models
Authors: Hayder M. Ehtesham , Munoz Alberto , Al-Shammari Ahmed
Published: May 2011

We will discuss issues in developing a production-injection surface facility model to optimize both oil production and water injection strategy in a mature giant oil field. Surface facility modeling was done using commercially available software, which was coupled to Saudi Aramco's in-house reservoir simulator POWERS1. Multiple integrated strategies for analyzing production can be considered with such models. In this paper, we evaluate a facility optimization perspective where many wells are rerouted between multiple gas-oil separation plants (GOSPs) to maintain adequate reservoir pressure to deliver required oil production volumes at the lowest operating cost. We also consider cases where the objective is to evaluate injection allocation strategies, which honors surface constraints, especially surface flow lines’ maximum operating pressure restrictions. Results presented in this paper include a subsurface reservoir coupled surface facility model where proposed strategies are designed to reroute wells from five existing GOSPs producing at high water cuts to two remaining GOSPs for production consolidation. Such strategy allows for an immediate cost savings, since it reduces the number of plants while at the same time producing the required volumes of oil, at reduced water cut, while at the same time maintaining reservoir sweep and recovery since wells which otherwise might have been shut-in are kept on active production. Simultaneously with the option of optimizing oil production, rerouting offers the opportunity to examine water disposal strategies since water can be injected near locations where there might be either a need for additional sweep or simply for reservoir pressure control and redistribution without compromising overall oil production.

We built a surface facility model consisting of five active GOSPs with a few hundred producers and injector (disposal) wells. The surface model is coupled to an over a million-cell reservoir model, containing a sub-set of all the wells available in the POWERS simulation model. Previous work had relied on describing exclusively the production system, leaving the injection system to be handled by POWERS’ well management rules and not subject to optimization or reconfiguration based on reservoir strategies. In this study, both the production and injection model have been constructed and calibrated using the latest available field data and history matched to field performance current at the time of calibration. Model calibration has been assisted by using automated scripts that transfer the relevant production and technical data from a corporate database to the individual model well files and which provide initial estimates for appropriate calibration parameter, such as productivity index, gradient curve matching or reservoir pressure at the time of a rate test, to current or historical field data. Those initial matches are later reviewed and validated on a well by well basis prior to use for prediction runs.
Sensitivity Analysis of Interfacial Tension on Saturation and Relative Permeability Model Predictions
Authors: Abdallah Wael , Zhao Weishu , Gmira Ahmed , Negara Ardiansyah , Buiting Jan
Published: May 2011

Interfacial tension (IFT) measurements of Dodecane/brine systems at different concentrations and Dodecane/deionized water subject to different Dodecane purification cycles were taken over extended durations at room temperature and pressure to investigate the impact of aging. When a fresh droplet was formed, a sharp drop in IFT was observed assumed to be a result of intrinsic impurity adsorption at the interface. The subsequent measurements exhibited a prolonged equilibration period consistent with diffusion from the bulk phase to the interface. Our results indicate that minute amounts of impurities present in experimental chemical fluids "used as received" have a drastic impact on the properties of the interface. Initial and equilibrium IFT are shown to be dramatically different, therefore it is important to be cautious of utilizing IFT values in numerical models. The study demonstrates the impact these variations in IFT have on relative permeability relationships by adopting a simple pore network model simulation.