bluuebunny/crossref_metadata_2025 huggingface dataset:
Contractility-dependent actin dynamics in cardiomyocyte sarcomeres
Authors: Skwarek-Maruszewska Aneta , Hotulainen Pirta , Mattila Pieta K. , Lappalainen Pekka
Published: May 2009

In contrast to the highly dynamic actin cytoskeleton in non-muscle cells, actin filaments in muscle sarcomeres are thought to be relatively stable and undergo dynamics only at their ends. However, many proteins that promote rapid actin dynamics are also expressed in striated muscles. We show that a subset of actin filaments in cardiomyocyte sarcomeres displays rapid turnover. Importantly, we found that turnover of these filaments depends on contractility of the cardiomyocytes. Studies using an actin-polymerization inhibitor suggest that the pool of dynamic actin filaments is composed of filaments that do not contribute to contractility. Furthermore, we provide evidence that ADF/cofilins, together with myosin-induced contractility, are required to disassemble non-productive filaments in developing cardiomyocytes. These data indicate that an excess of actin filaments is produced during sarcomere assembly, and that contractility is applied to recognize non-productive filaments that are subsequently destined for depolymerization. Consequently, contractility-induced actin dynamics plays an important role in sarcomere maturation.
IP-10 induces dissociation of newly formed blood vessels
Authors: Bodnar Richard J. , Yates Cecelia C. , Rodgers Margaret E. , Du Xiaoping , Wells Alan
Published: May 2009

The signals that prune the exuberant vascular growth of tissue repair are still ill defined. We demonstrate that activation of CXC chemokine receptor 3 (CXCR3) mediates the regression of newly formed blood vessels. We present evidence that CXCR3 is expressed on newly formed vessels in vivo and in vitro. CXCR3 is expressed on vessels at days 7-21 post-wounding, and is undetectable in unwounded or healed skin. Treatment of endothelial cords with CXCL10 (IP-10), a CXCR3 ligand present during the resolving phase of wounds, either in vitro or in vivo caused dissociation even in the presence of angiogenic factors. Consistent with this, mice lacking CXCR3 express a greater number of vessels in wound tissue compared to wild-type mice. We then hypothesized that signaling from CXCR3 not only limits angiogenesis, but also compromises vessel integrity to induce regression. We found that activation of CXCR3 triggers μ-calpain activity, causing cleavage of the cytoplasmic tail of β3 integrins at the calpain cleavage sites c'754 and c'747. IP-10 stimulation also activated caspase 3, blockage of which prevented cell death but not cord dissociation. This is the first direct evidence for an extracellular signaling mechanism through CXCR3 that causes the dissociation of newly formed blood vessels followed by cell death.
Automatic straightness measurement of a linear guide using a real-time straightness self-compensating scanning stage
Authors: Liu C H , Jeng Y-R , Jywe W Y , Deng S-Y , Hsu T-H
Published: May 2009

In this paper a method is developed for straightness measurement of a linear guide by using a straightness self-compensating stage with an optical straightness measuring system, an eddy current sensor, and a cross-roller type compensation stage. Both the compensation stage and the optical straightness system were set up on a scanning stage to measure the straightness error of the scanning stage. The measured straightness error was fed back to the control system to compensate directly in real time. Thus, straightness of a linear guide without the added straightness error of the scanning stage could be measured. The Hewlett Packard laser straightness calibration system was used to verify the real-time compensated results. Straightness error of the scanning stage was compensated from the worst straightness error of 20 μm/150 mm to 0.9 μm/150 mm. The eddy current sensor measured straightness of the linear guide and the measured result matched the result obtained by the coordinate measuring machine.
Interfacial features of polyamide 6 composites filled with oxidation modified carbon fibres
Authors: Li J
Published: May 2009

Polyacrylonitrile (PAN)-based carbon fibres were surface treated by ozone modification method and air-oxidation treatment. The interfacial properties of carbon fibre reinforced polyamide 6 (CF/PA6) composites were investigated by means of the single fibre pull-out tests. The surface characteristics of carbon fibres were characterized by X-ray photoelectron spectroscopy (XPS). As a result, it was found that interfacial shear strength values of the composites with ozone-treated carbon fibre are greatly increased. XPS results show that ozone treatment increases the amount of carboxyl groups on the carbon fibre surface, thus the interfacial adhesion between carbon fibre and PA6 matrix is effectively promoted. The effect of surface treatment of carbon fibres on the tribological properties of CF/PA6 composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fibre and PA6 matrix. Thus the wear resistance was significantly improved.
Non-linear analysis of body responses to functional electrical stimulation on hemiplegic subjects
Authors: Yu W-W , Acharya U R , Lim T-C , Low H W
Published: May 2009

Functional electrical stimulation (FES) is a method of applying low-level electrical currents to restore or improve body functions lost through nervous system impairment. FES is applied to peripheral nerves that control specific muscles or muscle groups. Application of advanced signal computing techniques to the medical field has helped to achieve practical solutions to the health care problems accurately. The physiological signals are essentially non-stationary and may contain indicators of current disease, or even warnings about impending diseases. These indicators may be present at all times or may occur at random on the timescale. However, to study and pinpoint these subtle changes in the voluminous data collected over several hours is tedious. These signals, e.g. walking-related accelerometer signals, are not simply linear and involve non-linear contributions. Hence, non-linear signal-processing methods may be useful to extract the hidden complexities of the signal and to aid physicians in their diagnosis. In this work, a young female subject with major neuromuscular dysfunction of the left lower limb, which resulted in an asymmetric hemiplegic gait, participated in a series of FES-assisted walking experiments. Two three-axis accelerometers were attached to her left and right ankles and their corresponding signals were recorded during FES-assisted walking. The accelerometer signals were studied in three directions using the Hurst exponent H, the fractal dimension (FD), the phase space plot, and recurrence plots (RPs). The results showed that the H and FD values increase with increasing FES, indicating more synchronized variability due to FES for the left leg (paralysed leg). However, the variation in the normal right leg is more chaotic on FES.
“But Doctors do it…”: Nurses' Views of Gifts and Information from the Pharmaceutical Industry
Authors: Jutel Annemarie , Menkes David B
Published: May 2009

Background

Most nurses, like their physician counterparts, lack education regarding pharmaceutical marketing strategies, and little is known of their beliefs and practices regarding this industry. Nurses are increasingly targeted by pharmaceutical companies as they become more involved in prescription and as policies restrict pharmaceutical companies' contact with physicians.

Objective

To assess nurses' beliefs and reported practices concerning pharmaceutical marketing and sponsorship strategies.

Methods

We conducted parallel Web- and paper-based surveys of a sample of senior registered nurses employed by government-funded health boards in 2 regions of New Zealand to explore their contact with the pharmaceutical industry as well as their beliefs and practices regarding information, gifts, and sponsorship provided by pharmaceutical companies. Returns were tested using Fisher's exact test to determine consistency in response between regions. Results for key outcome variables, including attitude toward the value of industry-derived information, were analyzed by region and in aggregate.

Results

Most nurses had contact with pharmaceutical sales representatives (69/106), accepted gifts from representatives (79/105), and believed information from the pharmaceutical industry probably improved their practice (71/106). Half believed that they would be able to detect misleading information if it were present, and 35% believed that accepting gifts and sponsorship was ethically acceptable. We found positive associations between the belief that information from the industry improved practice and reported acceptance of conference funding (OR 3.63; 95% CI 1.41 to 11.55), free food (OR 3.24; 95% CI 2.03 to 7.55), or gifts (OR 3.52; 95% CI 1.38 to 8.95). Nurses generally acknowledge the presence of pharmaceutical marketing in the hospital and the ethical challenges it presents; nonetheless, they also generally accept marketing gifts and may underestimate both the ethical challenges and their own susceptibility to persuasion.

Conclusions

Given the increasing role that nurses may play in pharmaceutical marketing strategy, the profession should consider its position vis-à-vis the industry.
Issues About the Physiological Functions of Prolyl Oligopeptidase Based on Its Discordant Spatial Association With Substrates and Inconsistencies Among mRNA, Protein Levels, and Enzymatic Activity
Authors: Myöhänen Timo T. , García-Horsman J. Arturo , Tenorio-Laranga Jofre , Männistö Pekka T.
Published: May 2009

Prolyl oligopeptidase (POP) is a serine endopeptidase that hydrolyses proline-containing peptides shorter than 30 amino acids. POP may be associated with cognitive functions, possibly via the cleavage of neuropeptides. Recent studies have also suggested novel non-hydrolytic and non-catalytic functions for POP. Moreover, POP has also been proposed as a regulator of inositol 1,4,5-triphosphate signaling and several other functions such as cell proliferation and differentiation, as well as signal transduction in the central nervous system, and it is suspected to be involved in pathological conditions such as Parkinson's and Alzheimer's diseases and cancer. POP inhibitors have been developed to restore the depleted neuropeptide levels encountered in aging or in neurodegenerative disorders. These compounds have shown some antiamnesic effects in animal models. However, the mechanisms of these hypothesized actions are still far from clear. Moreover, the physiological role of POP has remained unknown, and a lack of basic studies, including its distribution, is obvious. The aim of this review is to gather information about POP and to propose some novel roles for this enzyme based on its distribution and its discordant spatial association with its best known substrates.
Distinct Effects of Hedgehog Signaling on Neuronal Fate Specification and Cell Cycle Progression in the Embryonic Mouse Retina
Authors: Sakagami Kiyo , Gan Lin , Yang Xian-Jie
Published: May 2009

Cell-extrinsic signals can profoundly influence the production of various neurons from common progenitors. Yet mechanisms by which extrinsic signals coordinate progenitor cell proliferation, cell cycle exit, and cell fate choices are not well understood. Here, we address whether Hedgehog (Hh) signals independently regulate progenitor proliferation and neuronal fate decisions in the embryonic mouse retina. Conditional ablation of the essential Hh signaling componentSmoothened(Smo) in proliferating progenitors, rather than in nascent postmitotic neurons, leads to a dramatic increase of retinal ganglion cells (RGCs) and a mild increase of cone photoreceptor precursors without significantly affecting other early-born neuronal cell types. In addition,Smo-deficient progenitors exhibit aberrant expression of cell cycle regulators and delayed G1/S transition, especially during the late embryonic stages, resulting in a reduced progenitor pool by birth. Deficiency inSmofunction also causes reduced expression of the basic helix-loop-helix transcription repressorHes1and preferential elevation of the proneural geneMath5. InSmoandMath5double knock-out mutants, the enhanced RGC production observed inSmo-deficient retinas is abolished, whereas defects in the G1/S transition persist, suggesting thatMath5mediates the Hh effect on neuronal fate specification but not on cell proliferation. These findings demonstrate that Hh signals regulate progenitor pool expansion primarily by promoting cell cycle progression and influence cell cycle exit and neuronal fates by controlling specific proneural genes. Together, these distinct cellular effects of Hh signaling in neural progenitor cells coordinate a balanced production of diverse neuronal cell types.
Lineage and Birth Date Specify Motor Neuron Targeting and Dendritic Architecture in AdultDrosophila
Authors: Baek Myungin , Mann Richard S.
Published: May 2009

Locomotion in adultDrosophiladepends on motor neurons that target a set of multifibered muscles in the appendages. Here, we describe the development of motor neurons in adultDrosophila, focusing on those that target the legs. Leg motor neurons are born from at least 11 neuroblast lineages, but two lineages generate the majority of these cells. Using genetic single-cell labeling methods, we analyze the birth order, muscle targeting, and dendritic arbors for most of the leg motor neurons. Our results reveal that each leg motor neuron is born at a characteristic time of development, from a specific lineage, and has a stereotyped dendritic architecture. Motor axons that target a particular leg segment or muscle have similar dendritic arbors but can derive from different lineages. Thus, althoughDrosophilauses a lineage-based method to generate leg motor neurons, individual lineages are not dedicated to generate neurons that target a single leg segment or muscle type.
Visualization of Dopamine Transporter Trafficking in Live Neurons by Use of Fluorescent Cocaine Analogs
Authors: Eriksen Jacob , Rasmussen Søren G. F. , Rasmussen Trine Nygaard , Vaegter Christian Bjerggaard , Cha Joo Hwan , Zou Mu-Fa , Newman Amy Hauck , Gether Ulrik
Published: May 2009

The dopamine transporter (DAT) mediates reuptake of dopamine from the synaptic cleft and is a target for widely abused psychostimulants such as cocaine and amphetamine. Nonetheless, little is known about the cellular distribution and trafficking of natively expressed DAT. Here we use novel fluorescently tagged cocaine analogs to visualize DAT and DAT trafficking in cultured live midbrain dopaminergic neurons. The fluorescent tags were extended from the tropane N-position of 2β-carbomethoxy-3β-(3,4-dichlorophenyl)tropane using an ethylamino-linker. The rhodamine-, OR Green-, or Cy3-labeled ligands had high binding affinity for DAT and enabled specific labeling of DAT in live neurons and visualization by confocal imaging. In the dopaminergic neurons, DAT was uniformly distributed in the plasma membrane of the soma, the neuronal extensions, and varicosities along these extensions. FRAP (fluorescence recovery after photobleaching) experiments demonstrated bidirectional movement of DAT in the extensions and indicated that DAT is highly mobile both in the extensions and in the varicosities (immobile fraction less than ∼30%). DAT was constitutively internalized into vesicular structures likely representing intracellular transporter pools. The internalization was blocked by lentiviral-mediated expression of dominant-negative dynamin and internalized DAT displayed partial colocalization with the early endosomal marker EGFP-Rab5 and with the transferrin receptor. DAT internalization and function was not affected by activation of protein kinase C (PKC) with phorbol-12-myristate-13-acetate (PMA) or by inhibition with staurosporine or GF109203X. These data are in contrast to findings for DAT in transfected heterologous cells and challenge the paradigm that trafficking and cellular distribution of endogenous DAT is subject to regulation by PKC.
Dopamine Depletion Induces Distinct Compensatory Gene Expression Changes in DARPP-32 Signal Transduction Cascades of Striatonigral and Striatopallidal Neurons
Authors: Meurers Bernhard H. , Dziewczapolski Gustavo , Shi Tao , Bittner Anton , Kamme Fredrik , Shults Clifford W.
Published: May 2009

Functional alterations in striatal projection neurons play a critical role in the development of motor symptoms in Parkinson's disease (PD), but their molecular adaptation to dopamine depletion remains poorly understood. In particular, type and extent of regulation in postsynaptic signal transduction pathways that determine the responsiveness of striatal projection neurons to incoming stimuli, are currently unknown. Using cell-type-specific transcriptome analyses in a rodent model of chronic dopamine depletion, we identified large-scale gene expression changes, including neurotransmitter receptors, signal transduction cascades, and target proteins of dopamine signaling in striatonigral and striatopallidal neurons. Within the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) cascade of enzymes that plays a central role in signal integration of dopaminoceptive neurons multiple catalytic and regulatory subunits change their mRNA expression levels. In addition to the number of genes the fact that the alterations occur at multiple levels stresses the biological relevance of transcriptional regulation for adaptations of postsynaptic signaling pathways. The overall pattern of changes in both striatonigral and striatopallidal neurons is compatible with homeostatic mechanisms. In accordance with the distinct biological effects of dopamine D1and D2receptor stimulation, the alterations of the transcriptional profiles most likely result in prodopaminergic phosphorylation patterns. Our data provide insight into the disease-related plasticity of functional genomic networksin vivothat might contribute to the protracted preclinical phase of PD. In addition, the data have potential implications for the symptomatic treatment of the disease.
Pannexin 1: The Molecular Substrate of Astrocyte “Hemichannels”
Authors: Iglesias Rodolfo , Dahl Gerhard , Qiu Feng , Spray David C. , Scemes Eliana
Published: May 2009

Purinergic signaling plays distinct and important roles in the CNS, including the transmission of calcium signals between astrocytes. Gap junction hemichannels are among the mechanisms proposed by which astrocytes might release ATP; however, whether the gap junction protein connexin43 (Cx43) forms these “hemichannels” remains controversial. Recently, a new group of proteins, the pannexins, have been shown to form nonselective, high-conductance plasmalemmal channels permeable to ATP, thereby offering an alternative for the hemichannel protein. Here, we provide strong evidence that, in cultured astrocytes, pannexin1 (Panx1) but not Cx43 forms hemichannels. Electrophysiological and fluorescence microscope recordings performed in wild-type and Cx43-null astrocytes did not reveal any differences in hemichannel activity, which was mostly eliminated by treating Cx43-null astrocytes with Panx1-short interfering RNA [Panx1-knockdown (Panx1-KD)]. Moreover, quantification of the amount of ATP released from wild-type, Cx43-null, and Panx1-KD astrocytes indicates that downregulation of Panx1, but not of Cx43, prevented ATP release from these cells.
Evaluating the Power to Detect Temporal Trends in Fishery-Independent Surveys: A Case Study Based on Gill Nets Set in the Ohio Waters of Lake Erie for Walleyes
Authors: Wagner Tyler , Vandergoot Christopher S. , Tyson Jeff
Published: May 2009

Fishery-independent (FI) surveys provide critical information used for the sustainable management and conservation of fish populations. Because fisheries management often requires the effects of management actions to be evaluated and detected within a relatively short time frame, it is important that research be directed toward FI survey evaluation, especially with respect to the ability to detect temporal trends. Using annual FI gill-net survey data for Lake Erie walleyes Sander vitreus collected from 1978 to 2006 as a case study, our goals were to (1) highlight the usefulness of hierarchical models for estimating spatial and temporal sources of variation in catch per effort (CPE); (2) demonstrate how the resulting variance estimates can be used to examine the statistical power to detect temporal trends in CPE in relation to sample size, duration of sampling, and decisions regarding what data are most appropriate for analysis; and (3) discuss recommendations for evaluating FI surveys and analyzing the resulting data to support fisheries management. This case study illustrated that the statistical power to detect temporal trends was low over relatively short sampling periods (e.g., 5–10 years) unless the annual decline in CPE reached 10–20%. For example, if 50 sites were sampled each year, a 10% annual decline in CPE would not be detected with more than 0.80 power until 15 years of sampling, and a 5% annual decline would not be detected with more than 0.8 power for approximately 22 years. Because the evaluation of FI surveys is essential for ensuring that trends in fish populations can be detected over management-relevant time periods, we suggest using a meta-analysis–type approach across systems to quantify sources of spatial and temporal variation. This approach can be used to evaluate and identify sampling designs that increase the ability of managers to make inferences about trends in fish stocks.
Clinical and imaging follow-up after exhaustive liver resection of endocrine metastases: a 15-year monocentric experience
Authors: Scigliano S , Lebtahi R , Maire F , Stievenart J L , Kianmanesh R , Sauvanet A , Vullierme M P , Couvelard A , Belghiti J , Ruszniewski P , Le Guludec D
Published: May 2009

Liver metastases are common in gastroenteropancreatic neuroendocrine tumors and significantly impair survival. Hepatic resection is the only potential curative treatment. The records of 41 consecutive patients undergoing exhaustive resection of liver-only endocrine metastases and followed between 1992 and 2006 were reviewed. Patient's outcome and diagnostic accuracy of somatostatin receptor scintigraphy (SRS) and morphological imaging (MI) for detection of recurrences during post-operative follow-up were assessed. All identified primary had been resected. MI studies including abdominal computed tomography (CT) and/or liver magnetic resonance imaging and thoracic CT if indicated were performed every 6 months; SRS timing was decided by referring clinician. Tumor recurrences were confirmed by pathology or subsequent imaging studies. The results of 136 MI and SRS examinations performed within a 30-day interval from each other were retrospectively compared. Median post-operative follow-up was 51 months (7–165). Recurrences developed in 32 patients (78%), mainly in the liver (n=24) after a median of 19 months (2–79). Five-year overall and disease-free survival rates were 79 and 3% respectively. For recurrence detection, sensitivity, specificity, and accuracy were 89, 94, and 91% for SRS, 68, 91, and 74% for MI respectively. In 11 out of 32 patients (34%), abdominal or extra-abdominal metastases were detected 15.5 months earlier by SRS than MI. In conclusion, despite exhaustive liver surgery for endocrine metastases, hepatic or extra-hepatic recurrences are frequent and develop early. SRS is highly accurate for the detection of recurrences during post-operative follow-up and permitted early diagnosis in one third of patients; therapeutic implications of this early diagnosis remain to be determined.
Effects of temperature on ventilatory behavior of fish exposed to sublethal concentrations of endosulfan and chlorpyrifos
Authors: Patra Ronald W. , Chapman John C. , Lim Richard P. , Gehrke Peter C. , Sunderam Ramasamy M.
Published: May 2009

The ventilation amplitude and frequency of silver perch Bidyanus bidyanus, and the ventilation frequency of rainbow fish Melanotaenia duboulayi and rainbow trout Oncorhynchus mykiss, were determined at different temperatures upon exposure to endosulfan and chlorpyrifos, respectively. Silver perch and rainbow fish were tested at 15, 20, 25, 30, and 35°C, while rainbow trout was tested at 10, 15, 20, and 25°C. Although some trend of increasing amplitudes with increasing temperature was evident; there was no significant temperature response of ventilation frequency rates over time in silver perch pre-exposed to 10 μg L−1 endosulfan for 18 h. The rate of ventilation frequency of rainbow fish pre-exposed to 200 μg L−1 of chlorpyrifos for 96 h was lower in treatments than in the control at 15°C. However, between 20 and 35°C, rates were significantly higher in the treatments than those of the control. In rainbow trout pre-exposed to 100 μg L−1 of chlorpyrifos, the rates of frequency were significantly lower than those of controls in temperatures between 10 and 20°C but higher at 25°C. The amplitude of silver perch seemed to increase with the increase in temperature; however, the corresponding temperature quotient values at various temperature regimes and over exposure time showed no significant differences. The ventilation frequency of rainbow fish and rainbow trout significantly increased at the higher test temperatures, and their corresponding temperature quotient values for both fish also increased at the elevated temperatures.
Winning Productivity and Injectivity in Sabiriyah Upper Burgan: Life-of-field Approach to Tackle Development Challenges
Authors: Chetri H. B. , Baroon Bodoor , Al-Anzi Ealian
Published: May 2009

Sabiriyah Upper Burgan (UB) is a giant clastic reservoir in North Kuwait undergoing development efforts with water flood. Productivity indices as per historical data indicated these to be less than adequate and mismatching with the intrinsic reservoir permeabilities. This was a puzzle till a comprehensive review of the past pressure build up data was made and the results integrated with the-then perforation practices. More than 85% of the wells showed formation damage with a positive skin of +2 to +7, as per PBU data. Efforts were made to perform mud acid jobs without much success. After detailed review and performance analysis, recommendations were made to perforate new producers with TCP under balance, in addition to improvements in drilling mud chemistry. Subsequent PBU results of these wells indicated negative skin, which was also supported by better PIs.

The situation became a serious issue during initial phase of water flood and Injectivity tests. Injectors showed poor Injectivity indices. Though there had been multiple reasons for poor Injectivity, formation damage due to progressive plugging of pore throats was one of the major contributors. Detailed review of the dynamic behavior of the injectors led to the recommendations for improving the injection water quality by proper filtration, back flowing of the injectors prior to injection start-up and performing proppant frac jobs, if warranted. The implementation led to significant improvement in Injectivity. Phase-1 injection in the pressure depleted crestal area is in progress since last 3 years, thus sustaining production staying above the bubble point pressure.

Simultaneous to above, pore throat studies were conducted, leading to the conclusion that the pore throat size is very small with inherent risk of progressive plugging of injectors with time. In order to have life-of-field solution to Injectivity issues, recommendation was made to inject above parting pressure during the full field expansion of the water flood in 2010–11, on the basis of the results of Step Rate tests.

The case history of understanding and combating the formation damage in UB was a giant leap for rationalizing the way forward for its full fledged development.
Reservoir Pressure Depletion and Water Flooding Influencing Hydraulic Fracture Orientation in Low-Permeability Oilfields
Authors: Kuzmina S. , Butula K. K. , Nikitin A.
Published: May 2009

Hydraulic fracture azimuthal orientation depends on stress distribution in the formation and is considered to coincide with the maximal horizontal stress azimuth. Knowledge of the hydraulic fracture orientation is of critical importance in field development planning, including well spacing and pattern, the location of water injectors that will lead to a desired line drive mechanism, optimized reservoir drainage, and maximized recovery factor. This information is not less critical for infill drilling, fracturing "old" wells, refracturing, fracturing of sidetracks, and the knowledge of hydraulic fracture orientation of the water injector wells that are fractured by the mere injection process. It is also known that refracturing and pore pressure re-distribution will reorient the stress field not only in the near wellbore area but also in the far field.

Theoretical modeling and field experience suggest that hydraulic fractures do reorient under the influence of pore pressure changes because of reservoir fluid production and water injection. Field sector formation pressure distribution makes the fracture offset from maximal stress direction towards injection wells and this effect of local stress reorientation is more likely to occur in low permeable formations with low diffusivity and low horizontal stress anisotropy.

A number of complex fracture geometry orientation investigations were performed on low permeability formations in Siberia to understand the phenomenon. This included acoustic measurements and micro-seismic monitoring. Though the main purpose was to optimize fracture geometry by comparing measured and modeled fracture parameters, the importance of fracture orientation for reservoir development was even more significant.

The results undeniably indicate that a significant deviation of the field sector fracture azimuth from the maximal regional stress direction exists. It was discovered that the degree of deviation from the regional preferred fracture azimuth is affected by water injection and reservoir fluid production in the sector of the monitored well. Observations regarding the effect of fracture wing length asymmetry may also be explained by the disturbance of initial stress conditions. The results of this investigation will be used to further optimize hydraulic fracture design, reservoir pressure maintenance, including well spacing and well pattern, and water flooding strategies.
Recovery of an Oil Producer Severely Damaged by OBM Using an Advanced Barite Dissolver System
Authors: Davies C. , Twynam A. , Bulgachev R. , Harrington R.
Published: May 2009

BP in the U.K. North Sea attempted to drill a horizontal oil producer in the Harding field in 2006. Designed to produce an initial 10,000 blpd from 2000 feet of reservoir section before water break through, the well was compromised by the collapse of the lower hole due to chronic shale instability. This also resulted in the pre-drilled liner being stuck and set higher than initially planned. With less than 200 feet of reservoir sand exposed at the heel of the well (in close proximity to the water leg), the initial expectations were of 4,000 blpd. However the well was found to be badly impaired and produced 400 blpd. Although the well had been displaced to a carbonate based low solids oil based mud (LSOBM) prior to completion, a significant quantity of the barite weighted drilling system was still in the well.

The damaging mechanism was determined to be synthetic oil based mud compressed around the screen completion as well as the mud from the uncompleted horizontal lower hole being squeezed into the screens as the open hole gradually collapsed with time. A Coiled tubing (CT) intervention was carried out in late 2006 with solvents and multiple attempts with an acidic nano wash solvent system, this was not successful in restoring well productivity.

In 2007 BP chose to use an advanced chelate based barite/carbonate dissolver system behind a proprietary pre-flush system in an attempt to recover well productivity. Four operations have now been performed since September 2007 without CT, all as simple bull head operations. As a result of these treatments the well productivity (PI) has increased from 1.5 up to 12 blpd/psi. Current well rates are between 4000 to 6000 blpd depending on well stability and slugging caused by increasing water cuts.
Potential Increase of Formation Damage at Horizontal Wells as a Result of Changing Dynamic Filter Cake Properties with the Shear Rate
Authors: Dangou Mohamad , Chandler Howard
Published: May 2009

The invasion of drilling fluid filtrate into the region around the wellbore has long been recognized as one of the major factors contributing to damaging the reservoir formation. The volume of filtrate has a significant effect on the degree of damage, which is usually evaluated in API or HPHT static filtrate. Basically, filtration volume is a function of filter cake implementation, filtrate character, wellbore conditions and formation parameters. Under static conditions, as filtration proceeds a filter cake is formed and its solid content represents the particle size distribution of the whole drilling fluid. Under dynamic conditions, filter cake deposition mechanisms differ from those under static conditions due to the influence of hydrodynamic forces caused by drilling fluids flow. Consequently, the constitution of the dynamic filter cake is varies from that formed under static conditions, giving it different characteristics and filtration behaviour.

The scope of this study was to investigate the influence of the shear rate applied to the cake surface during dynamic filter cake deposition, on the filter cake constituents and dynamic filtration behaviour along horizontal wells. Extensive dynamic filtration experiments were conducted to test the filter cake and filtration parameters at the equilibrium dynamic stage. Three muddles of three different particle size distributions of Calcium Carbonate water-based drilling fluids were tested at different shear rates up to 400 sec-1.

The experimental results showed significant variations in dynamic filter cake parameters and filtration behaviour under different shear rates applied to the horizontal cake surface. Dynamic cake constituents and behaviour were also seen to differ from those of cakes formed under static conditions and one state cannot be taken to represent the other. Moreover, a critical value of shear rate can be detected from the dynamic cake parameters. The results also clearly demonstrated that a better cake quality was obtained at high shear rate values and a poor cake quality at low shear rates
First Regional Selective Packerless Acid-Fracture Stimulation With Coiled Tubing: A Documented Case History From Saudi Arabia
Authors: Sierra Leopoldo , Bustin Robert
Published: May 2009

A review of the stimulation methods used in the Hanifa formation (primarily a combination of diesel-emulsified acid/visco-elastic diverting systems) performed during the first two quarters of 2005 revealed that while initial post-stimulation vertical or deviated well-performance was typically improved, it was also short-lived (Surjaatmadja et al. 2001; Surjaatmadja et al. 2001; Surjaatmadja et al. 2002). All the wells exhibited a gradual loss in productivity after the stimulation treatments. Furthermore, in horizontal wells, the problem was aggravated because there was not enough control of acid placement over long openhole carbonate intervals where permeability or damage contrast existed; requiring a deeper matrix stimulation.

Exploring improved methods for stimulation, a multidisciplinary team composed of Saudi Aramco and service-company representatives were brought together to review various stimulation methods. After looking at conventional hydraulic-fracturing as a method of deeper-formation stimulation than matrix acidizing, it was concluded that over the long open-wellbore intervals, there would not be sufficient control of fracture placement, fracture growth and propagation, and interaction with the natural fracturing present in the Hanifa. Additionally, the typical Hanifa completion strings have completion size restrictions which limit the options for rigless stimulations.

After the review of several options, including coiled tubing (CT) proppant fracs, and stimulation using multiple and discrete mechanical-isolation devices like plugs or packers, the team selected the packerless selective acid fracture (PLSAF) stimulation using CT as the stimulation method most desirable for the limitations intrinsic to the Hanifa formation for the following reasons:

PLSAF with CT offers control of fracture placement in an openhole environment. PLSAF can achieve multiple treatments without mechanical isolation. PLSAF can provide moderately deep, controlled fractures with reduced risk to connect the generated fracture with the water sources.

PLSAF was applied successfully in one well during the third quarter of 2005, where ten selective acid fractures were placed along the openhole section. This paper presents the long-term evaluation and benefits of the first regional application of the PLSAF in Saudi Arabia.
Successful Field Application of a High-Temperature Conformance Polymer in Mexico
Authors: Mercado Modesto , Acuna Juan Carlos , Vasquez Julio , Caballero Carlos , Soriano Eduardo
Published: May 2009

Conformance-polymer systems have been successfully applied for many years to control undesired water production from hydrocarbon wells. However, currently available polymers present a number of limitations for high-temperature wells (>250°F) in terms of providing longer gelation times and acceptable thermal stability. This paper presents the successful field implementation of an organically crosslinked polymer (OCP) for high-temperature applications in southern Mexico.

The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneamine (PEI). To date, more than 450 jobs have been performed with the OCP system around the world to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel pack isolation, fracture shutoff, and/or casing-leak repair. Originally, the OCP system had a limited working temperature range from 100° to 250°F. The upper placement temperature of the system was ~250°F because, above this temperature, pumping times were too short. A recently developed carbonate retarder allows reasonable placement times up to 350°F, without the need for cooling down the formation to obtain enough pumping time. The retarder is not detrimental to the thermal stability of the system.

An overview of case histories that used OCP in southern Mexico is presented in this paper. In addition, the development results of the high-temperature conformance polymer are discussed in terms of (1) gelation-time measurement and (2) effectiveness to limit permeability to water and thermal stability in sandpack flow tests at elevated temperatures. To date, more than 70 jobs have been successfully performed worldwide with the OCP at temperatures higher than 250°F.
Horizontal Well Deliverability with Turbulence Effects
Authors: Wang Xiuli , Economides Michael J.
Published: May 2009

It is well known that in higher-permeability natural gas reservoirs turbulence, at times referred to as non-Darcy effects, may become the dominant influence on production. For vertical wells turbulence has been relatively well understood, deliverability equations have been adjusted to account for the phenomenon and, correlations have been presented a long time ago. Furthermore, field-testing techniques have been established to obtain the non-Darcy coefficient.

Surprisingly, similar work has not been done for horizontal wells. One of the reasons is that horizontal wells have been the completion of choice in North America primarily for very low permeability reservoirs where turbulence effects are of no consequence.

However, as the international petroleum industry starts looking at high-permeability gas reservoirs, turbulence effects in horizontal wells can no longer be ignored. Past work on the subject has been sketchy and in the one or two literature sources where it was addressed, the calculations are demonstrably wrong, not taking into account the crucial near-well effects. Also, quite important is that the few turbulence correlations used in the past, for some unexplainable reason have ignored the porosity.

We present here appropriate correlations to account for turbulence effects in horizontal wells and show that while horizontal wells, even with turbulence, provide considerably higher performance than vertical wells, the reduction from ideal expectations can be substantial. For example, at a permeability of 100 md, while for vertical wells the reduction between real and ideal production may approach 40%, for horizontal wells, it may approach 30%. The influence of porosity is considerable and can account for another 30% deviation among reasonable porosity values

We finally offer a large range of parametric studies that involve reservoir thickness, permeability anisotropy and horizontal well length. Turbulence effects have a tendency to reduce the expected beneficial ideal effects from longer wells or permeability isotropy because of the implicit "suicide" effects deriving from higher production rates.
Case Study: Water Shut-off Mechanism in Small, Remote Platform-Process & Challenge
Authors: Noordin F. M. , Razak M. H. A. , Ismail M.
Published: May 2009

Malong is part of an integrated marginal field developed in 1999 called MASA. Hydrocarbon is evacuated to a nearby Floating Production, Storage and Offloading (FPSO) facility for export. Its produced water system is currently being used up to its maximum design limit and hindering additional oil production.

Malong main reservoir J2 contributes about 97% of the total production. Currently, 7 wells are producing at 7.7 kbopd with average water cut of 70 percent. 88 percent of 18 kbwpd comes from 5 deviated wells while the rest is from 2 horizontal wells. J2 is a water injected reservoir with moderate to strong aquifer. This high permeability sand is distributed fairly well across the field and is subdivided into upper and lower lobes.

A comprehensive diagnostic of water flow entry mechanisms begins with compilation of critical information such as geological and reservoir data, production and injection data, cased hole data and well history. Subsequently, several analytical techniques such as material balance analysis, water control diagnostic plot, bubble maps and nodal analysis are applied.

The water production mechanisms are primarily dynamic contact movement due to production and possibly accompanied by flow behind casing. In all the wells, the lower lobe is mostly flushed leaving some oil from upper lobe only. Screening of suitable water shut-off methods gets complex considering tubing integrity issue, i.e. multiple tubing leaks, poor cement bond and possible deep invasion due to high permeability formation.

Detail evaluation is performed to weigh the pros and cons of mechanical type (cement squeeze) and chemical type (polymer gel). Finally, polymer gel is selected on the basis of less operational risk, controlled depth of invasion and easier removal. Additionally, coil tubing with packer is selected as the deployment method to ensure accurate placement of gel and to evade chemical loss through leaks.
The Optimum Injection Rate for Wormhole Propagation: Myth or Reality?
Authors: Glasbergen Gerard , Kalia Nitika , Talbot Malcolm
Published: May 2009

The success in matrix acidizing carbonate-formations depends entirely on the ability to create long wormholes that bypass the damaged near-wellbore region. Recently, much work has been performed to understand the wormhole propagation. This has led to various criteria and models to optimize matrix-acid treatment design for volumes, fluids, and flow rates. In many publications, the existence of an optimum flow rate for wormhole propagation has been described and efforts have been made to design treatments around these criteria.

This paper will discuss several of the criteria and models that can be used to determine the optimum flow rate in both radial and linear flow and will introduce a new and simple criterion for both radial and linear flow that is based on diffusivity, reactivity, porosity, and surface area. Most of the criteria have been developed based on laboratory results or simulations in controlled and idealized environments.

Under field conditions, many additional factors must be considered. Because of certain parameters such as significant heterogeneities in the formation, uncertainties in formation data, uncertainties in fluid placement, and operational constraints, the environment is neither controlled nor ideal. This paper will discuss the impact of these field conditions on the criteria and models to determine the optimum injection rate and verify their validity under field conditions. Examples and a case history are included to emphasize the need for consideration of these parameters. In addition, constraints are given to the validity of the criteria for the optimum flow rate under field conditions. This paper will further discuss the best practices and recommendations for cases where these constraints cannot be easily met or in cases where the data is uncertain.
Water and Sand Control Through Linear-Gel Frac Pack and Relative Permeability Modifier Techniques: Case Histories From the Casanare Basin, Colombia
Authors: Escobar V. , Rodriguez L. , Zambrano P. , Martinez O.
Published: May 2009

The C7 reservoir, located in Casanare Basin, not only exhibits serious formation consolidation problems, but the producing zone is also close to the oil/water contact. Most of the workover interventions have been focused on sand- and water-production issues. A solution developed to obtain hydrocarbon production that combines sand-control and water-control techniques, without additional services to clean the sand or change the production pump, is presented in this paper.

Numerous methods for this purpose exist in the industry, such as mechanical sand control methods, chemical treatments, and combinations of both. These are typically applied according to best practices with consideration of the associated costs.

The sand-control technique presented in this paper has been applied for three consecutive years in the area of Casanare, Colombia and has proven to be successful. This technique consists of pumping linear gel at high rates to place the proppant into the formation; in some cases, up to 40 sacks/ft (experiences in other regions mention 3.5 sacks/ft). In some cases, because of the proximity of the water, it was decided not to fracture to prevent the influx of water.

To increase the amount of proppant placed in the formation, a combination of two techniques, which have each proven to be successful individually, has been implemented. These techniques are: (1) use of a relative permeability modifier (RPM) to control the water influx and (2) high-rate pumping of linear gel to place proppant.

The combination of the RPM treatment and sand-control technologies designed for each particular area has set a new standard for sand-control operations in the area.