bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability in Dopamine Genes Dissociates Model-Based and Model-Free Reinforcement Learning
Authors: Doll Bradley B. , Bath Kevin G. , Daw Nathaniel D. , Frank Michael J.
Published: January 2016

Considerable evidence suggests that multiple learning systems can drive behavior. Choice can proceed reflexively from previous actions and their associated outcomes, as captured by “model-free” learning algorithms, or flexibly from prospective consideration of outcomes that might occur, as captured by “model-based” learning algorithms. However, differential contributions of dopamine to these systems are poorly understood. Dopamine is widely thought to support model-free learning by modulating plasticity in striatum. Model-based learning may also be affected by these striatal effects, or by other dopaminergic effects elsewhere, notably on prefrontal working memory function. Indeed, prominent demonstrations linking striatal dopamine to putatively model-free learning did not rule out model-based effects, whereas other studies have reported dopaminergic modulation of verifiably model-based learning, but without distinguishing a prefrontal versus striatal locus. To clarify the relationships between dopamine, neural systems, and learning strategies, we combine a genetic association approach in humans with two well-studied reinforcement learning tasks: one isolating model-based from model-free behavior and the other sensitive to key aspects of striatal plasticity. Prefrontal function was indexed by a polymorphism in theCOMTgene, differences of which reflect dopamine levels in the prefrontal cortex. This polymorphism has been associated with differences in prefrontal activity and working memory. Striatal function was indexed by a gene coding forDARPP-32, which is densely expressed in the striatum where it is necessary for synaptic plasticity. We found evidence for our hypothesis that variations in prefrontal dopamine relate to model-based learning, whereas variations in striatal dopamine function relate to model-free learning.

SIGNIFICANCE STATEMENTDecisions can stem reflexively from their previously associated outcomes or flexibly from deliberative consideration of potential choice outcomes. Research implicates a dopamine-dependent striatal learning mechanism in the former type of choice. Although recent work has indicated that dopamine is also involved in flexible, goal-directed decision-making, it remains unclear whether it also contributes via striatum or via the dopamine-dependent working memory function of prefrontal cortex. We examined genetic indices of dopamine function in these regions and their relation to the two choice strategies. We found that striatal dopamine function related most clearly to the reflexive strategy, as previously shown, and that prefrontal dopamine related most clearly to the flexible strategy. These findings suggest that dissociable brain regions support dissociable choice strategies.
DendritesIn VitroandIn VivoContain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation
Authors: Yau Kah Wai , Schätzle Philipp , Tortosa Elena , Pagès Stéphane , Holtmaat Anthony , Kapitein Lukas C. , Hoogenraad Casper C.
Published: January 2016

In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules. Rather than non-uniform microtubules, uniparallel minus-end-out microtubules are the signature of dendrites inDrosophilaandCaenorhabditis elegansneurons. To determine whether mixed microtubule organization is a conserved feature of vertebrate dendrites, we used live-cell imaging to systematically analyze microtubule plus-end orientations in primary cultures of rat hippocampal and cortical neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neurons in the somatosensory cortex of living mice.In vitroandin vivo, all microtubules had a plus-end-out orientation in axons, whereas microtubules in dendrites had mixed orientations. When dendritic microtubules were severed by laser-based microsurgery, we detected equal numbers of plus- and minus-end-out microtubule orientations throughout the dendritic processes. In dendrites, the minus-end-out microtubules were generally more stable and comparable with plus-end-out microtubules in axons. Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.

SIGNIFICANCE STATEMENTLive-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice.In vitroandin vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations. Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.
Resolution of High-Frequency Mesoscale Intracortical Maps Using the Genetically Encoded Glutamate Sensor iGluSnFR
Authors: Xie Yicheng , Chan Allen W. , McGirr Alexander , Xue Songchao , Xiao Dongsheng , Zeng Hongkui , Murphy Timothy H.
Published: January 2016

Wide-field-of-view mesoscopic cortical imaging with genetically encoded sensors enables decoding of regional activity and connectivity in anesthetized and behaving mice; however, the kinetics of most genetically encoded sensors can be suboptimal forin vivocharacterization of frequency bands higher than 1–3 Hz. Furthermore, existing sensors, in particular those that measure calcium (genetically encoded calcium indicators; GECIs), largely monitor suprathreshold activity. Using a genetically encoded sensor of extracellular glutamate andin vivomesoscopic imaging, we demonstrate rapid kinetics of virally transduced or transgenically expressed glutamate-sensing fluorescent reporter iGluSnFR. In both awake and anesthetized mice, we imaged an 8 × 8 mm field of view through an intact transparent skull preparation. iGluSnFR revealed cortical representation of sensory stimuli with rapid kinetics that were also reflected in correlation maps of spontaneous cortical activities at frequencies up to the alpha band (8–12 Hz). iGluSnFR resolved temporal features of sensory processing such as an intracortical reverberation during the processing of visual stimuli. The kinetics of iGluSnFR for reporting regional cortical signals were more rapid than those for Emx-GCaMP3 and GCaMP6s and comparable to the temporal responses seen with RH1692 voltage sensitive dye (VSD), with similar signal amplitude. Regional cortical connectivity detected by iGluSnFR in spontaneous brain activity identified functional circuits consistent with maps generated from GCaMP3 mice, GCaMP6s mice, or VSD sensors. Viral and transgenic iGluSnFR tools have potential utility in normal physiology, as well as neurologic and psychiatric pathologies in which abnormalities in glutamatergic signaling are implicated.

SIGNIFICANCE STATEMENTWe have characterized the usage of virally transduced or transgenically expressed extracellular glutamate sensor iGluSnFR to perform wide-field-of-view mesoscopic imaging of cortex in both anesthetized and awake mice. Probes for neurotransmitter concentration enable monitoring of brain activity and provide a more direct measure of regional functional activity that is less dependent on nonlinearities associated with voltage-gated ion channels. We demonstrate functional maps of extracellular glutamate concentration and that this sensor has rapid kinetics that enable reporting high-frequency signaling. This imaging strategy has utility in normal physiology and pathologies in which altered glutamatergic signaling is observed. Moreover, we provide comparisons between iGluSnFR and genetically encoded calcium indicators and voltage-sensitive dyes.
Regulation of ATP13A2 via PHD2-HIF1α Signaling Is Critical for Cellular Iron Homeostasis: Implications for Parkinson's Disease
Authors: Rajagopalan Subramanian , Rane Anand , Chinta Shankar J. , Andersen Julie K.
Published: January 2016

We previously reported that pharmacological inhibition of a class of enzymes known as prolyl hydroxylase domain proteins (PHDs) has neuroprotective effects in variousin vitroandin vivomodels of Parkinson's disease (PD). We hypothesized that this was due to inhibition of the PHD2 isoform, preventing it from hydroxylating the transcription factor hypoxia inducible factor 1 α (HIF1α), targeting it for eventual proteasomal degradation. HIF1α itself induces the transcription of various cellular stress genes, including several involved in iron metabolism. Although all three isoforms of PHD are expressed within vulnerable dopaminergic (DAergic) substantia nigra pars compacta neurons, only select downregulation of the PHD2 isoform was found to protect againstin vivoneurodegenerative effects associated with the mitochondrial neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These findings were corroborated in induced pluripotent stem cell-derived neurons, providing validation in a pertinent human cell model. PHD2 inhibition was found to result in increased expression ofATP13A2, mutation of which is responsible for a rare juvenile form of PD known as Kufor-Rakeb syndrome. Knockdown ofATP13A2expression within human DAergic cells was found to abrogate restoration of cellular iron homeostasis and neuronal cell viability elicited by inhibition of PHD2 under conditions of mitochondrial stress, likely via effects on lysosomal iron storage. These data suggest that regulation of ATP13A2 by the PHD2-HIF1α signaling pathway affects cellular iron homeostasis and DAergic neuronal survival. This constitutes a heretofore unrecognized process associated with loss ofATP13A2function that could have wide-ranging implications for it as a therapeutic target for PD and other related conditions.

SIGNIFICANCE STATEMENTReductions in PHD2 activity within dopaminergic neuronsin vivoand in cultured human induced pluripotent stem cell-derived neurons protects against mitochondrial stress-induced neurotoxicity. Protective effects are dependent on downstreamHIF-1α expression. Knockdown ofATP13A2, a gene linked to a rare juvenile form of Parkinson's disease and recently identified as a novel HIF1α target, was found to abrogate maintenance of cellular iron homeostasis and neuronal viability elicited by PHD2 inhibitionin vivoand in cultured dopaminergic cells under conditions of mitochondrial stress. Mechanistically, this was due toATP13A2's role in maintaining lysosomal iron stores. This constitutes a novel mechanism by which alterations inATP13A2activity may be driving PD-related neuropathology.
Female-Specific Intergenerational Transmission Patterns of the Human Corticolimbic Circuitry
Authors: Yamagata Bun , Murayama Kou , Black Jessica M. , Hancock Roeland , Mimura Masaru , Yang Tony T. , Reiss Allan L. , Hoeft Fumiko
Published: January 2016

Parents have large genetic and environmental influences on offspring's cognition, behavior, and brain. These intergenerational effects are observed in mood disorders, with particularly robust association in depression between mothers and daughters. No studies have thus far examined the neural bases of these intergenerational effects in humans. Corticolimbic circuitry is known to be highly relevant in a wide range of processes, including mood regulation and depression. These findings suggest that corticolimbic circuitry may also show matrilineal transmission patterns. Therefore, we examined human parent–offspring association in this neurocircuitry and investigated the degree of association in gray matter volume between parent and offspring. We used voxelwise correlation analysis in a total of 35 healthy families, consisting of parents and their biological offspring. We found positive associations of regional gray matter volume in the corticolimbic circuit, including the amygdala, hippocampus, anterior cingulate cortex, and ventromedial prefrontal cortex between biological mothers and daughters. This association was significantly greater than mother–son, father–daughter, and father–son associations. The current study suggests that the corticolimbic circuitry, which has been implicated in mood regulation, shows a matrilineal-specific transmission patterns. Our preliminary findings are consistent with what has been found behaviorally in depression and may have clinical implications for disorders known to have dysfunction in mood regulation such as depression. Studies such as ours will likely bridge animal work examining gene expression in the brains and clinical symptom-based observations and provide promising ways to investigate intergenerational transmission patterns in the human brain.

SIGNIFICANCE STATEMENTParents have large genetic and environmental influences on the offspring, known as intergenerational effects. Specifically, depression has been shown to exhibit strong matrilineal transmission patterns. Although intergenerational transmission patterns in the human brain are virtually unknown, this would suggest that the corticolimbic circuitry relevant to a wide range of processes including mood regulation may also show matrilineal transmission patterns. Therefore, we examined the degree of association in corticolimbic gray matter volume (GMV) between parent and offspring in 35 healthy families. We found that positive correlations in maternal corticolimbic GMV with daughters were significantly greater than other parent–offspring dyads. Our findings provide new insight into the potential neuroanatomical basis of circuit-based female-specific intergenerational transmission patterns in depression.
Orthogonal intercellular signaling for programmed spatial behavior
Authors: Grant Paul K , Dalchau Neil , Brown James R , Federici Fernan , Rudge Timothy J , Yordanov Boyan , Patange Om , Phillips Andrew , Haseloff Jim
Published: January 2016

Bidirectional intercellular signaling is an essential feature of multicellular organisms, and the engineering of complex biological systems will require multiple pathways for intercellular signaling with minimal crosstalk. Natural quorum‐sensing systems provide components for cell communication, but their use is often constrained by signal crosstalk. We have established new orthogonal systems for cell–cell communication using acyl homoserine lactone signaling systems. Quantitative measurements in contexts of differing receiver protein expression allowed us to separate different types of crosstalk between 3‐oxo‐C6‐ and 3‐oxo‐C12‐homoserine lactones, cognate receiver proteins, and DNA promoters. Mutating promoter sequences minimized interactions with heterologous receiver proteins. We used experimental data to parameterize a computational model for signal crosstalk and to estimate the effect of receiver protein levels on signal crosstalk. We used this model to predict optimal expression levels for receiver proteins, to create an effective two‐channel cell communication device. Establishment of a novel spatial assay allowed measurement of interactions between geometrically constrained cell populations via these diffusible signals. We built relay devices capable of long‐range signal propagation mediated by cycles of signal induction, communication and response by discrete cell populations. This work demonstrates the ability to systematically reduce crosstalk within intercellular signaling systems and to use these systems to engineer complex spatiotemporal patterning in cell populations.
The dynamic steroid landscape of equine pregnancy mapped by mass spectrometry
Authors: Legacki Erin L , Scholtz Elizabeth L , Ball Barry A , Stanley Scott D , Berger Trish , Conley Alan J
Published: January 2016

Liquid chromatography–tandem mass spectrometry (LC–MS/MS) allowed comprehensive analysis of various steroids detectable in plasma throughout equine gestation. Mares (n=9) were bled serially until they foaled. Certain steroids dominated the profile at different stages of gestation, clearly defining key physiological and developmental transitions. The period (weeks 6–20) coincident with equine chorionic gonadotropic (eCG) stimulation of primary corpora lutea and subsequent formation of secondary luteal structures was defined by increased progesterone, 17OH-progesterone and androstenedione, all Δ4 steroids. The 5α-reduced metabolite of progesterone, dihydroprogesterone (DHP) paralleled progesterone secretion at less than half the concentration until week 12 of gestation when progesterone began to decline but DHP concentrations continued to increase. DHP exceeded progesterone concentrations by week 16, clearly defining the luteo-placental shift in pregnane synthesis from primarily ovarian to primarily placental. The period corresponding to the growth of fetal gonads was defined by increasing dehydroepiandrosterone and pregnenolone (Δ5 steroids) concentrations from week 14, peaking at week 34 and declining to term. Metabolites of DHP (including allopregnanolone) dominated the steroid profile in late gestation, some exceeding DHP by weeks 13 or 14 and near term by almost tenfold. Thus Δ4 steroids dominated during ovarian stimulation by eCG, inversion of the ratio of progesterone: DHP (increasing 5α-pregnanes) marked the luteo-placental shift, Δ5 steroids defined fetal gonadal growth and 5α-reduced metabolites of DHP dominated the steroid profile in mid- to late-gestation. Comprehensive LC–MS/MS steroid analysis provides opportunities to better monitor the physiology and the progress of equine pregnancies, including fetal development.
A study on the design and material costs of tall wind turbine towers in South Africa
Authors: Way A , van Zijl G
Published: January 2016

The aim of this project was to study the structural design and material costing of various designs of tall wind turbine towers and the associated foundations in a South African context. Design guidelines are proposed for the design of tubular steel, concrete and concrete-steel hybrid towers and foundations for hub heights of 80, 100 and 120 m. The results indicate that concrete and hybrid towers become viable alternatives to the conventional steel towers at hub heights equal to and above 100 m. Three heights - 80 m, 100 m and 120 m - of each type of tower (steel, concrete and hybrid) and their foundations were designed according to the relevant design standards. The designs were verified using the Abaqus CAE finite element software (SIMULIA 2010). The material costs of the designs were calculated for a South African environment, according to the increases in material cost with increasing hub height. In this paper, the required foundation sizes for the concrete and hybrid towers were found to be smaller than for the steel towers. The material costs of the concrete and hybrid towers were shown to be lower than for the steel towers, especially at hub heights above 100 m. An increase in hub height caused an increase in energy generation of 3.52% and 6.28% for 80 m to 100 m, and for 80 m to 120 m hub heights, respectively. It is postulated that the concrete and hybrid towers become viable alternatives to the conventional steel towers at hub heights above 100 m.
As patients get older, we should be aware of salt levels in factor products
Authors: Alavian Sharon , Hutchinson Wendy
Published: January 2016

Hypertension is a well-known risk factor for ischaemic heart disease and cerebrovascular events. Globally, there is a drive to try to reduce salt intake. In an older population, where hypertension is likely to have a high prevalence, are health care professionals aware of the sodium content in replacement factor?
Management of an uncommon form of type 2M VWD: a single centre experience
Authors: Rashid Sabia , Bignell Patricia , Keeling David , Curry Nicola
Published: January 2016

We report a single centre’s experience of the diagnosis and management of an uncommon form of type 2 von Willebrand disease (VWD) in members of two unrelated families. The affected patients presented with mild to moderate bleeding phenotypes and accompanying MCMDM-1 VWD bleeding assessment tool scores of 5 or less. Genetic analysis in both families confirmed a missense mutation in exon 30 of the von Willebrand factor (VWF) gene, a single base substitution T>A at nucleotide 5282 which led to change at codon 1761 from methionine to lysine (M1761K). This mutation lies within the A3 domain of the VWF protein, a region that is important for collagen binding. All affected patients were found to have normal coagulation profiles, normal VWF multimers and normal VWF assays except the VWF collagen-binding (VWF: CB) assay levels, which were significantly reduced. Desmopressin effected a good response in all treated patients, with a 3- to 5-fold rise of VWF:CB levels. However, there was variability in the degree to which VWF:CB levels remained elevated. Surgical procedures, including the delivery of one patient, were able to be managed with either desmopressin and/or tranexamic acid alone, with little need for recourse to VWF factor concentrate therapy.
On the Number of Overlapping Words in Patterns
Authors: Фурлетова Е.И. , Furletova E.I.
Published: January 2016

The aim of the paper is to estimate the number of overlaps in the given pattern. The pattern is a set of words of same length m
in an alphabet A. We present theoretical and experimental bounds for overlaps number in two types of patterns. Firstly, we
considered random patterns which relate to uniform probability model, i.e. all letters in the alphabet and, correspondently, all words of same length are
equiprobable. We proved that the average number of overlaps P for random patterns consisting of n words
of length m linearly depends on pattern size n and is independent of length of pattern words.
In performed computer experiments the ratio P/n ranged from 0.33 till 1.06; the theoretical evaluations of the ratio for
the patterns do not exceed 1.67. The secondly, we studied the patterns described by position weight matrices (PWM) from the data base HOCOMOCO and various
cut-offs. For such patterns the ratio P/n in experiments ranged from 0.004 till 1, for most of the patterns it is smaller then 0.1.
What Is the Best Neovascular Age-related Macular Degeneration Treatment Regime for 2016?
Authors: Gale Richard P ,   Consultant Medical Ophthalmologist and Honorary Senior Clinical Lecturer, Academic Unit of Ophthalmology, York Hospital, York, UK,   Clinical Research Fellow, Academic Unit of Ophthalmology, York Hospital, York, UK, Gupta Reema
Published: January 2016

The management of neovascular age-related macular degeneration (nvAMD) has evolved significantly over the last few years with a significant step forward being taken with the advent of intravitreal therapy. Many different treatment regimens can be used, and the goal of treatment is shifting away from just salvaging vision to include reducing treatment burden on patients, carers and healthcare systems. This editorial discusses the common treatment regimens and proposes a pragmatic way of treating patients in three steps: (1) initiating a treatment, (2) finding the appropriate re-treatment interval and (3) fixing the re-treatment interval.
Diabetic Retinopathy Screening Methods and Programmes Adopted in Different Parts of the World – Further Insights
Authors: Pieczynski Janusz ,   Chair of Ophthalmology, University of Warmia and Mazury, Olsztyn, Warszawska, Poland,   Chair of Ophthalmology, University of Warmia and Mazury, Olsztyn, Warszawska, Poland,   The Voivodal Specialistic Hospital, Olsztyn, Zolnierska, Poland, Grzybowski Andrzej ,   Department of Ophthalmology, Poznan City Hospital, Poznan, Poland
Published: January 2016

This editorial provides supplementary information to our recently published article titled ‘Review of Diabetic Retinopathy Screening Method Programmes Adopted in Different Parts of the World’ inEuropean Ophthalmic Review, 2015;9(1):49–55.
Tempos críticos: intelectuais e imprensa nas páginas de Le Monde Diplomatique
Authors: Ogassawara Juliana Sayuri
Published: January 2016

Este artigo aborda questões midiáticas presentes na crítica de Le Monde Diplomatique. Fundado em 1954, em Paris, por Hubert Beuve-Méry, Le Monde Diplomatique teve suas páginas e suas ideias alastradas por diversos países – em 2013, o magazine contava mais de 40 edições internacionais, considerado um fenômeno único na imprensa internacional. Ao longo de sua trajetória, Le Monde Diplomatique teve sua linha editorial marcada por diretrizes politizadas, declaradamente antiimperialistas e antineoliberais. Ancorado na história dos intelectuais, na história política e na história do tempo presente, este artigo pretende analisar as críticas destinadas à mídia nas edições de Le Monde Diplomatique.
Lumbar Microdiscectomy
Authors: Truumees Eeric , Geck Matthew , Stokes John K. , Singh Devender
Published: January 2016

In most patients, the radiculopathy associated with lumbar disc herniation resolves nonoperatively. For patients in whom nonsurgical management has failed, microdiscectomy can be considered. Today, an operating microscope is preferred because of the collinear light and magnification offered. Alternatively, loupes and a headlight may be employed. The major steps of the procedure are (1) making a 2-cm vertical incision and then developing the corridor to the lamina subperiosteally or by using serial dilation techniques; (2) confirming the level of surgery radiographically prior to incision and once the lamina has been reached and then detaching the lateral attachments of the flavum; (3) making a small laminotomy, resecting any superior facet osteophytes, then mobilizing the compressed traversing nerve root, and, in some cases, making a small annulotomy; and (4) removing loose disc fragments and performing wound closure.

Most outcomes reports after microdiscectomy have been favorable for radicular symptoms. Associated back pain typically decreased as well. Common complications include recurrent disc herniation or disc herniation at another level, wound infections, and durotomy with spinal headache.
Mechanistic Modeling of Low-Salinity Waterflooding Through Coupling a Geochemical Package With a Compositional Reservoir Simulator
Authors: Korrani Aboulghasem Kazemi , Jerauld Gary R. , Sepehrnoori Kamy
Published: January 2016

Low-salinity waterflooding is an emerging enhanced-oil-recovery (EOR) technique in which the salinity of the injected water is substantially reduced to improve oil recovery over conventional higher-salinity waterflooding. Although there are many low-salinity experimental results reported in the literature, publications on modeling this process are rare. Although there remains some debate regarding the mechanisms of low salinity waterflooding process (LoSal EOR®)*, the geochemical reactions that control the wetting of crude oil on the rock are likely to be central to a detailed description of the process. Because no comprehensive geochemical-based modeling has been applied in this area, it was decided to couple a state-of-the-art geochemical package, IPhreeqc (Charlton and Parkhurst 2011), developed by the US Geological Survey, with UTCOMP (Chang 1990), the compositional reservoir simulator developed by The University of Texas at Austin.

A step-by-step algorithm is presented for integrating IPhreeqc with UTCOMP. Through this coupling, we are able to simulate homogeneous and heterogeneous (mineral dissolution/precipitation), irreversible, and ion-exchange reactions under nonisothermal, nonisobaric, and both local-equilibrium (away from the wellbore) and kinetic (near wellbore) conditions. Consistent with the literature, there are significant effects of water-soluble hydrocarbon components—e.g., carbon dioxide (CO2), methane (CH4), and acidic/basic components of the crude—on buffering the aqueous pH value and more generally, on the crude oil, brine, and rock reactions. Thermodynamic constraints are used to explicitly include the effect of these water-soluble hydrocarbon components. Hence, this combines the geochemical power of IPhreeqc with the important aspects of hydrocarbon flow and compositional effects to produce a robust, flexible, and accurate integrated tool capable of including the reactions needed to mechanistically model low-salinity waterflooding.

Different geochemical-based approaches to modeling wettability change in sandstones (e.g., interpolation on the basis of total ionic strength and multicomponent ion exchange through surface complexation of the organometallic components) were implemented in UTCOMP-IPhreeqc, and the integrated tool is then used to match and interpret a low-salinity experiment published by Kozaki (2012) and the field trial performed by BP at the Endicott field.
Low Solids Shear Dependent Fluid System to Plug Zones for Preventing Fluid Influx and Loss
Authors: Javier Urdaneta , Krishna Ravi , Jaime Pacheco , Oscar Jaramillo , John Patiño
Published: January 2016

Lost circulation and influx from sections of high-pressure zones is a recurrent challenge and high-cost event within the oil industry, particularly in mature fields or weak-fracture-gradient zones. These can significantly increase operational costs, non-productive time (NPT), the possibility of stuck pipe, and well integrity challenges. Lost circulation can be defined in a variety of ways, from partial to total loss, and in a variety of formations, including highly-permeable, fractured, or cavernous formations. Loss circulation materials, such as particulates, have been successfully used to plug smaller fractures and permeable zones. Challenges arise when the losses cannot be stopped using particulates because of the loss magnitude. The industry has used various chemical solutions to overcome this challenge with mixed results. Particulates are usually unsuccessful in terms of plugging high-pressure zones to help prevent fluid influx.

This paper presents a low-solids loss circulation solution that develops rapid gel strength when shear rate decreases. The gel strength buildup is based on polymers and nanomaterials in the fluid system. This helps prevent fluid from continuously flowing into the zone or being expelled from the zone. Once gel strength has developed, the system develops nominal compressive strength to adhere to the formation and thus helps prevent displacement during subsequent well operations. The fluid is shear thinning and hence easily enters the formation zone and does not flow continuously, as it gels upon entering the formation. The low solids and low rheology under shear means that it can be easily pumped through the drill bit without having to pull out of the hole (POOH).

This paper describes a system that was pumped into a high-pressure zone to isolate an unconsolidated sand formation. Initial attempts to isolate the zone included a bradenhead squeeze operation, which was unsuccessful, and fluid influx from the zone was observed during subsequent well operations. The fluid system and process described in this paper should help the industry in terms of shutting off streaks of high-pressure zones and curing fluid lost into the formation.
Size Degradation Studies of Lost Circulation Materials in a Flow Loop
Authors: Grant Patrick , Lassus Laurent , Savari Sharath , Whitfill Donald L.
Published: January 2016

Recently, there has been significant interest in understanding the material properties of lost circulation materials (LCM), including size degradation studies from mechanical compression tests and from shear flow. These types of tests are currently of particular importance because of increased drilling activity in mature fields, which often require LCMs as a background material. The objective of this work is to present the size degradation of LCMs from flow loop tests.

A flow loop test was performed to study the size degradation of LCMs, mainly ground marble (GM) and resilient graphitic carbon (RGC). A predetermined amount of GM and RGC was added to an 80-bbl synthetic-oil-based drilling fluid. The flow loop consisted of 3-in. diameter flow lines. One circulation through this flow loop required approximately 8 minutes, which is equivalent to one circulation in the actual field application. The fluid with LCM was circulated through the flow loop at a 400-gal/min flow rate. Fluid samples were collected at different stages, and a wet sieve analysis was performed to determine the amount of material in the drilling fluid retained on each sieve. Comparing the amount after the flow with the amount before flow allowed estimations of the LCM size degradation. This provided the size degradation the LCM would experience as a result of flow through the loop.

Another objective was to study the effect of a turbine, which was anticipated to be part of the bottomhole assembly (BHA) on the size degradation rate of LCMs. To evaluate this, a turbine was incorporated in the flow loop, and the fluid with LCM was again circulated at a 400-gal/min flow rate. Again, samples were collected at different times, with a wet sieve analysis performed to determine the size degradation of LCMs when flowing through the turbine and the flow loop.

GM was subjected to a 35% size reduction resulting from the flow loop alone, compared to only a 16% size reduction of the RGC. When the turbine was added to the flow loop, GM was almost completely degraded (a total of 75% reduction) to a smaller size after only one circulation through the loop. Concurrently, the RGC experienced only a 20% reduction in size even after 160 minutes of flow (20 circulations) through the loop and the turbine.

Size degradation studies of LCMs were conducted for the first time in a flow loop at a 400-gal/min circulation rate. The results show the importance of using a resilient LCM, such as RGC as part of a LCM background package when drilling lost circulation problem zones in mature fields.
Offshore Drilling Improvement Through Automating the Rig State Detection Process - Implementation Process History and Proven Success
Authors: de Oliveira Gabriel L. , Zank Cristiano A. , Costa André F. , Mendes Henrique M. , Henriques Luiz F. , Mocelin Márcio R. , de Oliveira Neto Jorcy
Published: January 2016

A rigorous initiative was undertaken in Brazil 3 years back to identify invisible lost time with the objective to improve safety and performance of the pre-salt drilling program.

This was only possible by combining the following:

Rigorous drilling data quality assurance and recording. Use of automation to correctly identify the rig state using a proven known product. Using an appropriate commercial algorithms and web reporting systems to clearly help analyze the results on both safety and invisible lost time. Building a team of performance engineers to analyze and work with the contractor to help identify areas of safety and performance improvement – the data shows that these two items go hand in hand. A safe crew works consistently well that directly affects performance. Constant re-training and interacting with contractors to ensure that they get to see and understand the variability in their routine operations and perform route cause analysis with the aid of the automation tool.

Among many of the examples presented in the paper will be one on weight to weight connection time of an entire fleet of rigs (23 rigs) that reduced in 19% from 2012 to 2014 through the elimination of unnecessary reaming (that wasn't clearly measured before this effort). Also the variability among contractors is 50% in a wellbore conditioning time per connection that is a huge difference when comparing how similar these operations really were. The paper will also present actual total savings considering several KPIs of about 350 offshore rig days that translates in more than ¼ of a billion dollars.

The conclusion is that a lot can be saved by combining automation, processes, and management commitment at the appropriate mix level – just throwing money at problems isn't necessarily the solution.
Effective Operational Collaboration Delivers Substantial Real-Time Service Quality Improvements
Authors: Sadlier Andreas , Blue Duncan , Halland Thomas
Published: January 2016

Real-time solutions provide a critical decision support and collaboration platform that enable better decisions throughout the well construction and production lifecycle. Operators, drilling contractors, and service companies use these real-time capabilities to improve operations service quality, monitor efficiencies, understand formation geology, and enhance overall reservoir knowledge.

Real-time operating centers are typically staffed with domain experts; they can provide surveillance to support less experienced wellsite personnel, provide advice and guidance, and support remotely performed operations. Data systems must acquire, process, aggregate, distribute, and present relevant real-time information quickly and accurately to ensure a rapid assessment of the current situation. However, their effectiveness depends on adequate real-time service quality and standardized data delivery.

Many factors can contribute to either poor data quality or inconsistent, untimely data distribution. In addition to the most obvious technology limitations, such as available bandwidth, latency, or overall system performance, many nontechnical influences can also negatively affect performance. All too often, technology is relied upon to provide these solutions, and the human factor is taken for granted or ignored. These human factors can include failing to set pre-job expectations, setup and configuration, monitoring protocols, or communication protocols. Other human factors issues can include a lack of data standardization or established governance regarding the management of the data and its underlying quality.

This paper presents a case history that describes how the collaborative effort between a major NOC and service company was used to substantially improve the value delivered from consistent real-time data and service quality. Specifically, this paper addresses the identification of the problem, root cause analysis, and specific remedies that were implemented, as well as clear real-time key performance indicators that could be used to measure and monitor improved performance.
Enhanced Extended Reach Well Design in Saudi Arabia Leads to Optimized Drilling Performance and Significant Cost Reduction
Authors: Muñoz German , Balseiro Prudencio , Dhafeeri Bader , Im Ahmad Ba
Published: January 2016

The Saudi Arabian Oil Company (Saudi Aramco) operates one of the principal high profile extended reach drilling (ERD) projects in the world. This is accomplished through the development of a sizable number of horizontal wells categorized according to the total depth. Wells with the shortest vertical displacement have been significantly optimized during the project execution thereby reducing the room for enhancement. The drilling engineering team conducted a comprehensive evaluation of the existing casing scheme and problematics along the M field. A new approach was devised to redesign wells with a total depth up to 17,600 ft. The aim was to achieve a substantial improvement in drilling performance and potential savings for the remainder of the project.

ML-1 and MO-1 were selected as candidates to implement the novel alternative; both drilled from different platforms where several wells have been previously completed using the standard design. Drilling troubles, such as loss of circulation and hole instability, occurred during the execution of such wells leading to major lost time. The solution comprised the optimization of the well trajectory, slim-down the upper hole sections and combine the lower ones, drill longer intervals and set casings deeper to cover problematic zones without compromising the well integrity. The detailed engineering study included a probabilistic analysis to evaluate the economic viability of the landmark application.

Two wells were successfully drilled and completed applying the downsizing strategy. The impact of anticipated challenging events in both 12 1/4-in and 8 1/2-in holes was decreased as a result of the new design. The implemented preventive plans led to a rapid elimination of encountered challenges. This optimization produced a combined 27% reduction in drilling time, and minimal non-productive time (NPT) with associated global cost savings of 39% compared to a large hole string design.

Finally, this new approach in a still ongoing project along with the feasibility of extending it to other areas will lead to potential improvement in well delivery and operating cost.
Fully Mechanical Vertical Drilling System Delivers RSS Performance in Vertical Drilling Applications While Providing an Economical Alternative to Conventional Rotary Steerable Systems Set-Up for Vertical Hold Mode
Authors: Jones Steve , Feddema Chad , Castro Juan , Sugiura Junichi
Published: January 2016

Deviation control in a vertical well (or the vertical portion of a directional well) can be challenging, especially when pushing the limits for maximum penetration rate. Over the years rotary steerable systems (RSS) have been adapted to fit the vertical drilling market. These electro-mechanical directional control systems are set-up to seek low-side but they come at a relatively high cost of RSS.

This paper describes a purpose-built 100% mechanical vertical drilling system. The vertical drilling system has been developed to drill vertical wells economically with the accuracy and borehole quality of a rotary steerable system. The intelligent mechanical control system has been instrumented to analyze response in different drilling environments throughout North America land. Compact measurement sensors embedded into key components of the tool record system behavior and response.

Through case studies, the effectiveness of the mechanical control system to eliminate deviation on vertical wells will be demonstrated. Onboard memory data from the sensors will be used to examine the stability of the system and prove that simple mechanical control is an efficient and effective method for vertical drilling.
Modeling Real-Time ECD during Transient Pumping and/or Tripping Using Time-Dependent Fluid Properties
Authors: Kulkarni Sandeep D. , Jamison Dale E. , Pereira Vitor Lopes , Porter Aidan
Published: January 2016

Drilling operational parameters, such as pump rate, pipe tripping speed, and drilling fluid time-dependent rheological characteristics can impact wellbore pressure management and equivalent circulating density (ECD). It is important that ECD at any instant remain between fracture and pore pressure gradients (drilling window). This paper presents modeling ECD for transient wellbore conditions, which demonstrates the model predictions match pressure while drilling (PWD) measurements obtained from several wells.

Drilling fluids exhibit time-dependent rheological response particularly at static or low-shear conditions. The fluids develop gel microstructure attributed to interaction between polymers, colloidal particles, and emulsion droplets. As pumping is initiated or pipe moved, ECD spikes occur because of the developed gel microstructure; then, the microstructure breaks down gradually with shearing. Understanding the mechanism of gel formation and breakdown under various shear, temperature, and pressure conditions improves accuracy of the ECD modeling for transient fluid characteristics.

Pump rate can accelerate or decelerate during several operations (e.g., during pipe connections). Another operational parameter, tripping speed, can exhibit variation. For example, pipe speed can accelerate from static to the highest speed; then, decelerate to static. Furthermore, the fluid can be pumped during tripping operations to help manage wellbore pressure. In addition, such pumping helps speed up tripping; thus, saving rig time. The coupled effect of momentum change during these transient operational parameters in addition to time-dependent fluid properties on ECD response is investigated, exhibiting improved understanding of transient effects improves ECD modeling accuracy for such conditions.

The developed models for ECD response were validated on several wells. Fluid properties, real-time pump rate, and tripping speed information were used as model inputs, while outputs were compared with PWD data obtained from the wells. With successful validation, these models can now be used for improved design of operational parameters and fluid characteristics for wellbore management.
A New Friction Reduction Tool with Axial Oscillation Increases Drilling Performance: Field-Testing with Multiple Vibration Sensors in One Drill String
Authors: Jones Steve , Feddema Chad , Sugiura Junichi , Lightey Jeff
Published: January 2016

Weight transfer problems, hanging-up, poor toolface control and diminishing ROP are all problems that are encountered with steerable motors in high angle and horizontal wells. A number of oscillation devices have been introduced to the market over the years to aid these common problems.

Both axial and lateral vibration tools have proven to provide improvements to drilling performance and toolface control. However, as with any device, there are always limiting factors, and oscillation devices could cause unwanted vibrations that interfere with measurement-while-drilling (MWD) systems and even cause component failures.

This paper describes the operation and field-test results from a new axial oscillation tool. The tool uses a mud valve to generate pressure pulses in the string. These pressure pulses are magnified using a specifically designed stroke tool referred to as an amplifier. The mud valve is driven with a short power section from a Positive Displacement Motor (PDM).

The lobe configuration of the power section is directly related to the frequency of the tool, while nozzles in the tool allow for variable pressure regimes of differing applications. The system was tested with specific MWD systems in a flow loop prior to the job to confirm compatibility. Key components in the string were instrumented to gather critical information on vibration frequency levels throughout the BHA in an effort to optimize system performance.

A compact, self-contained 3-axis inclinometers and 3-axis shock sensors (¾-in diameter and 3.8-in length) have been deployed during field testing to capture downhole dynamics. These sensors were strategically positioned in the BHA to gain understanding of vibration propagation distance/pattern and vibration frequency changes over the course of the run.

Downhole instrumented sensors were used to confirm the value of the axial vibration mechanism. The use of multiple compact downhole dynamics recording devices has provided new insights in challenging steerable motor drilling applications, assisted with an axial friction reduction tool.