bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations on the Damage Potential of Drilling Fluids: HT/HP-Return-Permeability Tests Under Dynamic Conditions
Authors: Freese Carsten 
Published: October 2017

In view of the increasing scarcity of energy resources, wells are being drilled to progressively greater depths for the production of liquid and gaseous hydrocarbons. Economical exploitation of these HT/HP reservoirs is possible only with the application of drilling and completion methods which do not damage the formation. Here, the reservoir-saving exposure of these deposits is an essential contribution.
The damage potential of drilling fluids and treatment fluids is usually assessed on the basis of return permeability (RP) tests. An impairment of the effective rock permeability through appropriate candidate fluids (drill in fluids, etc.) can be measured with special laboratory tests. In addition to the RP-Tests further investigations should be made to estimate the formation damage such as high-resolution digital photography, mercury porosimetry, scanning electron microscopy as well as microsection analyses.
Within the framework of the German Society for Petroleum and Coal Science and Technology a project was carried out to evaluate common formation damage test facilities and to define the “best practice” meeting the requirements of RP-measurements under borehole-like conditions. After a thorough evaluation an advanced HT/HP facility for formation damage testing was designed and built. By using of this set-up, systematic return-permeability tests were performed under dynamic conditions for temperatures up to 180 °C, for a flow pressure up to 250 bar, and a mantle pressure up to 350 bar.
This paper presents results from a study on the filtration and formation damage behaviour of drilling fluids under variation of the concentration and of the weighting material particle size distribution. Furthermore, promising results from changing dynamic and static filtration experiments are discussed.
On the Numerical Modeling of Slug and Intermittent Flows in Oil and Gas Production
Authors: Nieckele Angela O. , Carneiro João N. E. 
Published: October 2017

Recent advances on the modeling of two-phase flows in pipes have shown that the accurate modeling of Two-Fluid equations allow the dynamic simulation of various regimes within a single numerical framework, diminishing the empiricism associated with the flow-pattern dependent closure relations. Such “Regime-Capturing” approaches have been traditionally called “Slug-Capturing”, as a reference to dynamic simulations of stratified-to-slug transition. In this paper, we will outline several examples of applications, ranging from horizontal stratified wavy, slug and annular flows, to vertical annular and intermittent flows. Vertical flow has been a bottleneck in Slug Capturing due to ill-posedness of the Two-Fluid Model. Ill-posedness of the model equations will be briefly addressed along with different regularization methods and stabilizing terms based on physical behavior, such as shape profile factors and dynamic pressure contributions. In order to numerically solve the governing system of equations, the finite volume method is employed with Upwind and second order TVD spatial discretization schemes, along with first order time discretization.
Flow parameters such as temperature and pressure drop are determined as well as film thickness and wave characteristics of both annular and stratified flow, and slug velocity, length and frequency in slugging cases. Comparison with experimental data for annular, slug and stratified flows, with different fluids and pipeline configurations are presented, illustrating the good performance of the methodology.
Study of Local Ice Loads Measured at Norströmsgund Lighthouse
Authors: Zvyagin Petr , Ziemer Gesa 
Published: October 2017

It is believed that ice loading can be a stationary process at least sometimes during the state of continuous brittle crushing. Confidence in the distribution law, stationarity in time, and autocorrelation function of local ice loads is the key factor for assessment of such loads and their successful simulation. Good understanding of the load process on the level of a single transducer record can be helpful in future analysis and simulation of loads on wider contact areas.
In this paper local loads, simultaneously measured by two middle subpanels at the Norströmsgrund lighthouse in March 2001, are studied. Stationary time series of lognormal origin of 50 seconds duration are extracted from both of the subpanel records. From the studied data, stationarity was not observed simultaneously at different subpanels. The correlation of one stationary subpanel record with simultaneous record of the other subpanel found to be weak.
A simple function with good fit to the observed autocorrelation curve of stationary load fragments is suggested. The findings are compared with parameters obtained for local loads in previous studies. A transition from autocorrelation function for raw lognormal data to autocorrelation function of logarithmic normal data is performed.
Low Cycle Fatigue of Subsea Mechanically Lined Pipeline With Liner Imperfections
Authors: Pépin Aurélien , Tkaczyk Tomasz , O’Dowd Noel , Nikbin Kamran 
Published: October 2017

There is an ever-increasing demand for subsea transport of corrosive constituents which requires the use of corrosion resistant pipelines. This has generated interest in mechanically lined pipe (MLP) which consists of carbon steel pipe lined with a thin layer of corrosion resistant alloy (CRA), typically stainless steel. The CRA liner is adhered to the backing pipe by means of an interference fit.
MLPs have been traditionally installed subsea using low strain methods such as towing, S-lay or J-lay. More recently, the efficient reel-lay method, typically used for pipelines up to 18” (457.2 mm) in diameter, has also been considered. To prevent damage to the MLP during high strain bending (i.e. wrinkling of CRA the liner) and thus allow reel-lay installation, TechnipFMC has qualified reeling of MLPs at ambient and elevated pressures. The ambient reeling approach, where the liner thickness is increased to prevent wrinkling during reeling, is appropriate for smaller diameter MLPs. For larger pipelines, it is generally more cost-effective to pressurise the MLP during reeling.
Concerns have been expressed that liner imperfections such as small dents or wrinkles, introduced during manufacturing, installation or service, may compromise the integrity of the MLP subjected to high in-service cyclic loading. Therefore, this study was undertaken to examine the criticality of such flaws and determine the low cycle fatigue endurance of reeled MLPs with imperfections. First, a numerical study was undertaken to estimate in-service stress/strain ranges in the MLPs with liner flaws. Subsequently, small scale tests were carried out to quantify the fatigue performance of such MLPs. The obtained results confirmed that there is a negligible risk of failure of MLP flowlines due to crack initiation at liner imperfections and subsequent breach of the CRA layer, even for pipelines subjected to very severe inservice cyclic loading.
Modelling of the Dynamic Behavior of the Power Transmission of an Automatic Small Scale Drilling Rig
Authors: Cayeux Eric , Skadsem Hans Joakim 
Published: October 2017

The automatization of the drilling process opens the opportunity to faster reactions in case of unexpected drilling conditions, therefore reducing the risk that a drilling incident escalates to a serious situation. It also allows to push the drilling performance to be as close as possible to the limits of drillability as a function of the varying drilling conditions. But to achieve high level of drilling process automation, it is necessary to have access to accurate mathematical models of the complex physical system that is composed of the drilling rig, the drill-string, the drilling fluid and the borehole itself.
As the development of accurate heat transfer, mechanical and hydraulic models and their utilization in full scale drilling applications is a huge and complex task, it is tempting to recreate drilling automatization problems in a laboratory scale setup.
Because of sudden variations of the downhole drilling conditions, like when transitioning from soft to hard rock or when the bit is subject to large torque variations induced by interbedded rock layers, the boundary conditions at the bit change suddenly and require quick response from the automatic top-drive and hoisting system controllers. At a small laboratory scale, the necessary reaction times are of the order of milliseconds and therefore exclude any manual intervention. It is therefore crucial that the automatic control methods utilize precise mathematical models of the physical system to accurately estimate the limits by which the drilling process can be managed under safe conditions. For that reason, a general purpose mathematical model of small-scale drilling rigs has been developed.
First, the Rayleigh-Ritz method is used to determine the deflection of the drill-string and to estimate the side forces at the contact points along the drill-string and BHA (Bottom Hole Assembly). Then the dynamic response of the power transmission system is modelled for both variable frequency drive controlled tri-phase motors and for stepper motors, including friction effects at the contact points. Friction is modelled using Stribeck theory rather than the classical Coulomb laws of friction. Finally, the expected response of 3D accelerometers, that could be placed on the outside of a BHA component, is modelled to retrieve possible inclination variations and potential vibration modes such as torsional oscillations, forward or backward whirl.
The generality of the model is such that it can be used for many small-scale drilling rig designs.
Full Cycle Resource Evaluation of SMS Deposits Along the Arctic Mid Ocean Ridge
Authors: Ellefmo Steinar Løve , Ludvigsen Martin , Frimanslund Erik Kristian Thon 
Published: October 2017

Several hydrothermal vent sites have been discovered along the portion of the Arctic Mid-Ocean Ridge (AMOR) inside the extended Norwegian continental shelf (NCS). Seafloor massive sulfide (SMS) deposits are associated with these hydrothermal vent sites. These deposits contain significant amounts of valuable metals, such as copper, zinc, gold, and silver. Loki’s Castle is one of the most promising sites along the AMOR, with two 20–30 m high and 100 m wide mound-shaped SMS deposits. It is located at a water depth of 2,400 m. A production system concept is proposed for a deep-sea mining operation at Loki’s Castle based on the Nautilus Minerals’ Solwara 1 project. The overall cost structure and design of the Nautilus’ concept is in this study regarded feasible in AMOR in spite of the difference between the operating environment for the two locations. As the only relevant operational experience is De Beers’ shallow-water diamond mining off the coast of South Africa and Namibia, most of the environmental criteria used are taken from offshore drilling. Based on the net operating time, and accounting for scheduled maintenance and waiting-on-weather time, an estimate for annual average production rate and an annual production volume are estimated. Significant downtime is expected in January and July.
Significant uncertainties are associated with early phases of projects. Probabilistic cost, grade and price estimates allow dealing quantitatively with uncertainties by giving input variables as probability distributions. Monte Carlo simulations are in this study run for different sets of variables, and the resulting key performance indicators are given as distributions.
This paper adapts and presents a methodology normally used to assess technological and economic feasibilities of oil and gas projects. The methodology is adapted to the assessment of deep-sea mining projects and is illustrated through the assessment of the case based on Loki’s Castle ore characteristics and technologies planned for the Solwara 1 project with a cost structure adjusted according to AMOR conditions. Costs for processing, refining, waste disposal and logistics after ore arrival at onshore port is not included. The ore uncertainties are huge and the resources are with the present deposit knowledge speculative. Therefore, this study do not attempt to define any reserves.
pH-Sensor Under Consideration for Multi-Sensor-Chip in Downhole Drilling Fluid Monitoring
Authors: Kühne Jonathan , Güth Frederic , Strauß Heike , Joseph Yvonne , Árki Pál 
Published: October 2017

Modern drill strings for the exploration of oil and gas are equipped with a variety of sensor carrying devices such as Measurement While Drilling (MWD), Logging While Drilling (LWD), and Formation Testing While Drilling (FTWD). These devices generate a large amount of downhole data, such as the orientation of the well, drilling parameters e.g. weight on bit and torque, and formation properties. Appropriate telemetry systems are included in the drill string to transfer relevant downhole data in real time to the surface. Other data is stored in memories downhole for subsequent evaluation. However, drilling fluid properties are still monitored at the surface and their behavior under borehole conditions is predicted with hydraulic models. Commercial solutions for a direct downhole measurement of various drilling fluid parameters are rare, though they would increase drilling process safety and the knowledge about the behavior of drilling fluids under real bottomhole conditions.
The pH has a significant influence on the properties of water-based muds and plays a role in the chemistry of oil-based muds as the water cut in the emulsion increases. Commercial pH-sensing devices, such as the glass electrode, and optical sensors are not appropriate for the pH measurement under bottomhole conditions. Fragility, the insufficient degree of miniaturization, the low temperature and pressure resistance due to the liquid reference electrolyte, and phenomena such as the alkaline error are certain drawbacks of glass electrodes. Often optical sensors often will not capture the whole pH scale and require the medium to be at least slightly transparent for light. The usage of pH-sensors based on EIS (electrolyte-isolator-semiconductor) structures is a possible application of chemical sensors for drilling fluid monitoring under in situ borehole conditions.
This paper presents results from a study on the behavior of an EIS structure as a pH sensitive electrode measured vs. a commercial Ag/AgCl reference electrode in comparison with a commercial glass electrode. EIS structures are capacitive pH sensors where the sensing layer is generally a metal oxide on a semiconductor substrate.
Measurements in basic drilling muds were conducted under constant temperature and atmospheric pressure while the drilling mud was steadily stirred. The mud was titrated from alkaline to acidic conditions with hydrochloric acid and the pH was measured after potential equilibration at the electrodes. The results show a general feasibility for the usage of the proposed sensor. There are still certain challenges to be overcome in the development of a robust and reliable pH-sensing device for complex fluids, such as drilling muds under high pressure/high temperature (HP/HT) conditions.
Investigation of EGR With EGB (Exhaust Gas Bypass) on Low Speed Marine Diesel Engine Performance and Emission Characteristics
Authors: Wang Zhanguang , Zhou Song , Feng Yongming , Zhu Yuanqing 
Published: October 2017

In 2016, the International Maritime Organization (IMO) has enforced stricter nitrogen oxide (NOx) emission standards. Exhaust gas recirculation (EGR) technology is an effective way to achieve IMO Tier III standards for two-stroke marine diesel engines. This paper selected the 6S50ME-C8.2 diesel engine for the study, by making use of GT-POWER simulation software. In this paper, three different types of EGR were built to investigate the effects of EGR on engine performance and NOx emissions.
The results show that both the high pressure EGR system and the low pressure EGR system can reduce NOx emissions with the power drop and BSFC risen.
While in the high pressure EGR system combined with EGB, more NOx can be reduced with less power drop and BSFC risen. What is more, the running points of the compressor are still in the high efficient area and away the surge margin.
Based on the conclusions, the results obtained in this paper can offer reference for the turbocharged diesel engines with EGR system to reduce NOx emissions and improve engine performance.
Prof. Torgeir Moan and the Record Breaking Fjord Crossings in Norway
Authors: Skorpa Lidvard , Jakobsen Bernt , Østlid Håvard 
Published: October 2017

Technology and competence from offshore structures, which were developed to serve in the harsh environment of the North Sea, have played a major role in developing technology for extreme fjord crossings in Norway. The Høgsfjord Project, and later the E39 Fjord Crossings Project, have taken advantage of the existing competence and experience from offshore structures. To a great extent, it has been a question of adapting offshore technology and combining it with advanced bridge technology to new types of structures. These new bridges are in many respects very different from offshore structures, mainly due to their length, slenderness, long resonance periods and complex dynamic behavior.
Professor Torgeir Moan has been heavily involved in the technology development for the fjord crossings. First, in the Høgsfjord submerged floating tunnel project, and now in the Fjord Crossings project with the bold aim of making the E39 Coastal Highway along the west-coast of Norway free of ferries. He has always showed genuine interest in the challenges, and have always been willing to help identifying and solving the problems. His contribution has been vital to the outcome of the work.
Sustained
Ex Vivo
Susceptibility of Plasmodium falciparum to Artemisinin Derivatives but Increasing Tolerance to Artemisinin Combination Therapy Partner Quinolines in The Gambia
Authors: Amambua-Ngwa Alfred , Okebe Joseph , Mbye Haddijatou , Ceesay Sukai , El-Fatouri Fatima , Joof Fatou , Nyang Haddy , Janha Ramatoulie , Affara Muna , Ahmad Abdullahi , Kolly Olimatou , Nwakanma Davis , D'Alessandro Umberto 
Published: October 2017

ABSTRACT

Antimalarial interventions have yielded a significant decline in malaria prevalence in The Gambia, where artemether-lumefantrine (AL) has been used as a first-line antimalarial for a decade. Clinical
Plasmodium falciparum
isolates collected from 2012 to 2015 were analyzed
ex vivo
for antimalarial susceptibility and genotyped for drug resistance markers (
pfcrt
K76T,
pfmdr1
codons 86, 184, and 1246, and
pfk13
) and microsatellite variation. Additionally, allele frequencies of single nucleotide polymorphisms (SNPs) from other drug resistance-associated genes were compared from genomic sequence data sets from 2008 (
n
= 79) and 2014 (
n
= 168). No artemisinin resistance-associated
pfk13
mutation was found, and only 4% of the isolates tested in 2015 showed significant growth after exposure to dihydroartemisinin. Conversely, the 50% inhibitory concentrations (IC
50
s) of amodiaquine and lumefantrine increased within this period.
pfcrt
76T and
pfmdr1
184F mutants remained at a prevalence above 80%.
pfcrt
76T was positively associated with higher IC
50
s to chloroquine.
pfmdr1
NYD increased in frequency between 2012 and 2015 due to lumefantrine selection. The TNYD (
pfcrt
76T and
pfmdr1
NYD wild-type haplotype) also increased in frequency following AL implementation in 2008. These results suggest selection for
pfcrt
and
pfmdr1
genotypes that enable tolerance to lumefantrine. Increased tolerance to lumefantrine calls for sustained chemotherapeutic monitoring in The Gambia to minimize complete artemisinin combination therapy (ACT) failure in the future.
ABCI3 Is a New Mitochondrial ABC Transporter from Leishmania major Involved in Susceptibility to Antimonials and Infectivity
Authors: Arcari Talia , Manzano José Ignacio , Gamarro Francisco 
Published: October 2017

ABSTRACT

We have identified and characterized ABCI3 as a new mitochondrial ABC transporter from
Leishmania major
. Localization studies using confocal microscopy, a surface biotinylation assay, and trypsin digestion after digitonin permeabilization suggested that ABCI3 presents a dual localization in both mitochondria and the plasma membrane. From studies using parasites with a single knockout of
ABCI3
(
ABCI3
+/−
), we provide evidence that ABCI3 is directly involved in susceptibility to the trivalent form of antimony (SbIII) and metal ions. Attempts to obtain parasites with a double knockout of
ABCI3
were unsuccessful, suggesting that
ABCI3
could be an essential gene in
L. major
.
ABCI3
+/−
promastigotes were 5-fold more resistant to Sb
III
than the wild type, while
ABCI3
+/−
amastigotes were approximately 2-fold more resistant to pentavalent antimony (Sb
V
). This resistance phenotype was associated with decreased Sb
III
accumulation due to decreased Sb
III
uptake.
ABCI3
+/−
parasites presented higher ATP levels and generated less mitochondrial superoxide after Sb
III
incubation. Finally, we observed that
ABCI3
+/−
parasites showed a slightly higher infection capacity than wild-type and add-back
ABCI3
+/−
::3×FABCI3 parasites; however, after 72 h the number of
ABCI3
+/−
intracellular parasites per macrophage increased significantly. Our results show that ABCI3 is responsible for Sb
III
transport inside mitochondria, where it contributes to enhancement of the general toxic effects caused by Sb
III
. To our knowledge, ABCI3 is the first ABC transporter which is involved in susceptibility toward antimony, conferring Sb
III
resistance to parasites when it is partially deleted.
A Cohort Study of Risk Factors That Influence Empirical Treatment of Patients with Acute Pyelonephritis
Authors: Bosch-Nicolau Pau , Falcó Vicenç , Viñado Belén , Andreu Antonia , Len Oscar , Almirante Benito , Pigrau Carles 
Published: October 2017

ABSTRACT

The aim of the current study was to compare community-acquired acute pyelonephritis (CA-APN) with health care-associated acute pyelonephritis (HCA-APN), describe the outcomes, and identify variables that could predict antimicrobial susceptibility. We conducted an observational study that included all consecutive episodes of acute pyelonephritis (APN) in adults during 2014 at a Spanish university hospital. From each episode, demographic data, comorbidities, clinical presentation, microbiological data, antimicrobial therapy, and outcome were recorded. A multivariable logistic regression model was performed to define the variables associated with antimicrobial resistance. A total of 607 patients, 503 (82.9%) with CA-APN and 104 (17.1%) with HCA-APN, were included in the study. Patients with HCA-APN were older than patients with CA-APN (70.4 versus 50.6 years;
P
< 0.001) and had higher rates of previous urinary tract infections (UTIs) (56.5% versus 24.5%;
P
< 0.001) and previous antibiotic use (56.8% versus 22.8%;
P
< 0.001).
Escherichia coli
was more frequently isolated from patients with CA-APN than from patients with HCA-APN (79.9% versus 50.5%;
P
< 0.001). The rates of resistance of
Escherichia coli
strains from CA-APN patients versus HCA-APN patients were as follows: amoxicillin-clavulanic acid, 22.4% versus 53.2% (
P
= 0.001); cefuroxime, 7.7% versus 43.5% (
P
= 0.001); cefotaxime, 4.3% versus 32.6% (
P
< 0.001); ciprofloxacin, 22.8% versus 74.5% (
P
< 0.001); and co-trimoxazole, 34.5% versus 58.7% (
P
= 0.003). The site of acquisition, recurrent UTIs, and previous antibiotic use were independent risk factors for antimicrobial resistance. Relapse rates were significantly higher when definitive antimicrobial treatment was not adequate (37.1% versus 9.3% when definitive antimicrobial treatment was adequate;
P
< 0.001). Our study reflects the rise of resistance to commonly used antibiotics in acute pyelonephritis. In order to choose the adequate empirical antibiotic therapy, risk factors for resistance should be considered.