bluuebunny/crossref_metadata_2025 huggingface dataset:
Rough I2-Lacunary Statistical Convergence of Double Sequences
Authors: Kişi Ömer , Dündar Erdinç
Published: June 2018

In this paper, we introduce and study the notion of rough I2-lacunary statistical convergence of double sequences in normed linear spaces. We also introduce the notion of rough I2-lacunary statistical limit set of a double sequence and discuss about some properties of this set.
Compound Glass Microsphere Resonator Devices
Authors: Yu Jibo , Lewis Elfed , Farrell Gerald , Wang Pengfei
Published: June 2018

In recent years, compound glass microsphere resonator devices have attracted increasing interest and have been widely used in sensing, microsphere lasers, and nonlinear optics. Compared with traditional silica resonators, compound glass microsphere resonators have many significant and attractive properties, such as high-Q factor, an ability to achieve high rare earth ion, wide infrared transmittance and low phonon energy. This review provides a summary and a critical assessment of the fabrication and the optical characterization of compound glasses and the related fabrication and applications of compound glass microsphere resonators.
Satellite and Ground Remote Sensing Techniques to Trace the Hidden Growth of a Lava Flow Field: The 2014-15 Effusive Eruption at Fogo Volcano (Cape Verde)
Authors: Calvari Sonia , Ganci Gaetana , Victória Sónia Silva , Hernandez Pedro A. , Perez Nemesio , Alfama Vera , Barrancos José , Cabral Jeremias , Cardoso Nadir , Dionis Samara , Fernandes Paulo , Melian Gladys , Pereira José , Semedo Hélio , Padilla Germán , Rodriguez Fátima
Published: June 2018

Fogo volcano erupted in 2014-15 producing an extensive lava flow field in the summit caldera that destroyed two villages, Portela and Bangaeira. The eruption started with powerful explosive activity, lava fountains, and a substantial ash column accompanying the opening of an eruptive fissure. Lava flows spreading from the base of the eruptive fissure produced three arterial lava flows. By a week after the start of the eruption, a master lava tube had already developed within the eruptive fissure and along the arterial flow. In this paper, we analyze the emplacement processes on the basis of observations carried out directly on the lava flow field, remote sensing measurements carried out with a thermal camera, SO2 fluxes, and satellite images, in order to unravel the key factors leading to the development of lava tubes. These were responsible for the rapid expansion of lava for the ~7.9 km length of the flow field, as well as the destruction of the Portela and Bangaeira villages. The key factors leading to the development of tubes were the low topography and the steady magma supply rate along the arterial lava flow. Comparing time-averaged effusion rates (TADR) obtained from satellite and Supply Rate (SR) derived from SO2 flux data, we estimate the amount and timing of the lava flow field endogenous growth, with the aim of developing a tool that could be used for hazard assessment and risk mitigation at this and other volcanoes.
Microbial Endophytes That Live within Seeds of Two Tomato Hybrid Cultivated in Argentina
Authors: López Silvina , Pastorino Graciela , Franco Mario , Medina Rocio , Lucentini Gustavo , Saparrat Mario , Balatti Pedro
Published: June 2018

Tomato (Solanum lycopersicum L.) is widely consumed around the world is mostly affected by stresses and diseases that reduce yield and production. Research on sustainable technologies like the use of beneficial microorganismsis crucial to development sustainable management strategies. Endophytic bacteria might increase production as well as plant health.. In this work we studied the endobiome of tomato seeds of different cultivars since the plant genotype might affect the microbial community structure in terms of plant growth promoters as well as organisms for biocontrol. The conditions prevailing within seeds along the maturation period might have affected bacterial survival. This is such that seed endophytes share features, which are different from those of bacteria from other plant tissues. The community associated with different cultivars reflects the different resources available in the seed and its potential to prevent the attack of pathogens and to promote plant growth.
Structural Evolution of Two-Phase Blends of Polycarbonate and PMMA by Simultaneous Biaxial Stretching
Authors: Kobayashi Takumi , Saito Hiromu
Published: June 2018

We investigated the structural evolution of the two-phase blends of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) at various blend compositions by simultaneous biaxial stretching using optical microscopy and SEM observation. The spherical PMMA domains and PC matrix in 30/70 PC/PMMA were enlarged uniformly at all in-plane direction, while the anisotropic-shaped co-continuous structure in 50/50 PC/PMMA was deformed to crosshatched one by in-plane bimodal orientation. In 70/30 PC/PMMA, the phase inversion was found to occur by simultaneous biaxial stretching; i.e., the spherical PMMA domains were changed to crosshatched matrix by in-plane bimodal orientation due to coalescence of the PMMA domains during the stretching. Owing to the phase inversion, the surface hardness estimated by pencil hardness test became harder from 2B to 2H with increasing the strain from 1.0 to 2.0.
Analysis of the Process Parameter Influence in Laser Cladding of 316L Stainless Steel
Authors: Alvarez Piera , Montealegre M. Ángeles , Pulido-Jiménez Jose F. , Arrizubieta Jon I.
Published: June 2018

Laser Cladding is one of the leading processes within Additive Manufacturing technologies, a fact which has concentrated an important amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting laser cladding in single clads, meanwhile overlap percentage and overlapping strategy become also relevant when dealing with multiple clads. By means of setting appropriate values of each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and substrate is obtained, trying simultaneously to maintain processing times in their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads for dilution analysis, height and width for the values of overlap between contiguous clads and layers, and also to analyze them for physical defects such as porosity and cracks. The resulting solid piece was 8 mm high at 800 mm/min.
The Role of the Primary Cell Wall in Plant Morphogenesis
Authors: Lamport Derek T , Tan Li , Held Michael , Kieliszewski Marcia J.
Published: June 2018

Morphogenesis remains a riddle, wrapped in a mystery, inside an enigma. It remains a formidable problem viewed from many different perspectives of morphology, genetics, and computational modelling. We propose a biochemical reductionist approach that shows how both internal and external physical forces contribute to plant morphogenesis via mechanical stress-strain transduction from the primary cell wall tethered to the plasma membrane by a specific arabinogalactan protein (AGP). The resulting stress vector with direction defined by Hechtian adhesion sites, has a magnitude of a few picoNewtons amplified by a hypothetical Hechtian growth oscillator. This paradigm shift involves stress activated plasma membrane Ca2+channels and auxin-activated H+-ATPase. The proton pump dissociates periplasmic AGP-glycomodules that bind Ca2+. Thus, as the immediate source of cytosolic Ca2+ an AGP-Ca2+ capacitor directs vectorial exocytosis of cell wall precursors and auxin efflux (PIN) proteins. In toto these components comprise the Hechtian Oscillator and also the gravisensor. Thus interdependent auxin and Ca2+ morphogen gradients account for the predominance of AGPs. The size and location of a cell surface AGP-Ca2+ capacitor is essential to differentiation and explains AGP correlation with all stages of morphogenetic patterning from embryogenesis to root and shoot. Finally, evolutionary origins of the Hechtian Oscillator in the unicellular Chlorophycean algae reflect the ubiquitous role of chemiosmotic proton pumps that preceded DNA at the dawn of life.
Chiroptical Symmetry Analysis (CSA): on the Way from the Understanding of Highly Symmetric Systems to the Development of Chiroptical Applications
Authors: Castro-Fernández Silvia , Peña-Gallego Ángeles , Mosquera Ricardo A. , Alonso-Gómez José Lorenzo
Published: June 2018

The high sensitivity of chiroptical responses to conformational changes and supramolecular interactions has prompted an increasing interest in the development of chiroptical applications. However, prediction and understanding the chiroptical responses of the necessary large systems may not be affordable for calculations at high levels of theory. In order to facilitate the development of chiroptical applications, methodologies capable of evaluating the chiroptical responses of large systems are necessary. Exciton chirality method has been extensively used for the interaction between two independent chromophores through the Davydov model. For systems presenting C2 or D2 symmetry one can get to the same results by applying the selection rules. In the present article, analysis of the selection rules for systems with symmetries Cn and Dn with n = 3 and 4 is used to uncover the origin of their chiroptical responses. We hope that the use of the chiroptical symmetry analysis (CSA) for systems presenting the symmetries explored herein as well as for systems presenting higher symmetries will serve as a useful tool for the development of chiroptical applications.
Molecular characterization of divergent closterovirus isolates infecting Ribes species
Authors: Koloniuk Igor , Thekke-Veetil Thanuja , Reynard Jean-Sébastien , Mavrič Pleško Irena , Přibylová Jaroslava , Brodard Justine , Kellenberger Isabelle , Sarkisova Tatiana , Špak Josef , Lamovšek Janja , Massart Sebastien , Ho Thien , Postman Joseph , Tzanetakis Ioannis
Published: June 2018

Five isolates of a new putative member of the genus Closterovirus, tentatively named blackcurrant leafroll associated virus 1 (BcLRaV-1), were identified in currant. The 17 kb long genome of BcLRaV-1 contained 10 open reading frames (ORFs). The replication associated polyprotein has two papain-like leader proteases, a methyltransferase, a helicase and an RNA-dependent RNA polymerase domain. Additional ORFs coded for heat shock protein 70 homolog, heat shock protein 90 homolog, two divergent copies of coat protein, and three accessory proteins without identifiable functions. Phylogenetic analysis showed that BcLRaV-1 is related to members of the genus Closterovirus and recombination analysis of the isolates showed clear evidences of intraspecies recombination.
Equilibrium and Kinetic study of lead and copper ions adsorption on Chitosan-grafted-poly acrylic acid synthesized by Surface-initiated Atomic Transfer Polymerization
Authors: Grande Carlos , Vallejo William , Zuluaga Fabio
Published: June 2018

In this work, we synthesized chitosan grafted-poly acrylic acid (CS-g-PA) through surface-initiated atom transfer radical polymerization (SI-ATRP). We also studied the adsorption process of copper and lead ions onto CS-g-PA surface. Adsorption equilibrium studies indicated pH 4.0 as the best pH for the adsorption process, while the maximum adsorption capacity for Pb2+ ions was 98 mg*g-1 and for Cu2+ was 164 mg*g-1, higher adsorption capacities than chitosan alone (CS), where Pb2+ was only 14.8 mg*g-1and Cu2+ was 140 mg*g-1, respectively. Furthermore, the adsorption studies indicated that Langmuir model describes all the experimental data. All these results suggest that the new CS-g-PA polymers had potential as adsorbent for hazardous and toxic metal ions produced by different industries.
Can Stemness and Chemoresistance be Therapeutically Targeted via Signaling Pathways in Ovarian Cancer?
Authors: Roy Lynn , Cowden Dahl Karen
Published: June 2018

Ovarian cancer is the most lethal gynecological malignancy. Poor overall survival, particularly for patients with high grade serous (HGS) ovarian cancer, are often attributed to late stage at diagnosis and relapse following chemotherapy. HGS ovarian cancer is a heterogenous disease in that few genes are consistently mutated between patients. Additionally, HGS ovarian cancer is characterized by high genomic instability. For these reasons personalized approaches may be necessary for effective treatment and cure. Understanding the molecular mechanisms that contribute to tumor metastasis and chemoresistance are essential to improve survival rates. One favored model for tumor metastasis and chemoresistance is the cancer stem cell (CSC) model. CSCs are cells with enhanced self-renewal properties that are enriched following chemotherapy. Elimination of this cell population is thought to be a mechanism to increase therapeutic response. Therefore, accurate identification of stem cell populations that are most clinically relevant is necessary. While many CSC identifiers (ALDH, OCT4, CD133, and side population) have been established, it is still not clear which population(s) will be most beneficial to targeted in patients. Therefore, there is a critical need to characterize CSCs with reliable markers and find their weaknesses that will make the CSCs amenable to therapy. Many signaling pathways are implicated for their roles in CSC initiation and maintenance. Therapeutically targeting pathways needed for CSC initiation or maintenance may be an effective way of treating HGS ovarian cancer patients. In conclusion, the prognosis for HGS ovarian cancer may be improved by combining CSC phenotyping with targeted therapies for pathways involved in CSC maintenance.
Modeling and Analyzing Multi-tier Millimeter/Micro Wave Hybrid Caching Networks
Authors: Zhao Jihong , Zhao Shuyuan , Qu Hua , Ren Gongye
Published: June 2018

In the fifth generation communication system, millimeter wave (mmWave) networks will coexist with traditional micro wave (μWave) networks, which allows for higher data transmission rate and better user experience. In this paper, we give a comprehensive framework of mathematical models and analytical methods for multi-tier mmWave and μWave hybrid caching networks based on stochastic geometry. We propose an association strategy by assuming average biased-received power association and Rayleigh fading. Accordingly, by using a D-ball approximating blockage model of mmWave networks, expressions of the cell association probability and the coverage probability of the hybrid networks are derived. Also, we use the average successful delivery probability as the performance metric to analyze the existing caching placement strategies. Simulation results validate the accuracy of our analytical conclusions.
Development of Bio-Inspired Low-Noise Propeller for a Drone
Authors: Noda Ryusuke , Nakata Toshiyuki , Ikeda Teruaki , Chen Di , Yoshinaga Yuma , Ishibashi Kenta , Rao Chen , Liu Hao ,   Department of Mechanical Engineering, Kanto Gakuin University 1-50-1 Mutsuura-Higashi, Kanazawa-ku, Yokohama-shi, Kanagawa 236-8501, Japan,   Graduate School of Engineering, Chiba University 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba 263-8522, Japan
Published: June 2018

Multicopter-type unmanned aerial vehicles, called drones, have been attracting wide attention because of their immense potential for use in various missions such as surveillance, reconnaissance, and delivery service. For the application of drones, however, their noise will be a serious issue especially when operating in urban areas, and to our knowledge, it has not been resolved yet. In this study, inspired by the unique wing structures of insects and birds, we have developed new low-noise-type propellers for drones. The various bio-inspired attachments of drones such as the serrations at the leading edge, velvet-like surface, and fringes at the trailing edge were tested, and their acoustic and aerodynamic performances were evaluated experimentally and numerically. Our results indicate that an attachment at the trailing edge can suppress the noise level while maintaining the aerodynamic efficiency of the proposed propeller close to that of the basic propeller.
Position and Posture Measurement Method of the Omnidirectional Camera Using Identification Markers
Authors: Hatakeyama Naoya ,   Graduate School of Science and Engineering, University of Toyama 3190 Gofuku, Toyama-shi, Toyama 930-8555, Japan, Sasaki Tohru , Terabayashi Kenji , Funato Masahiro , Jindai Mitsuru
Published: June 2018

Recently, many studies on unmanned aerial vehicle (UAVs) that perform position control using camera images have been conducted. The measurements of the surrounding environment and position of the mobile robot are important in controlling the UAV. The distance and direction of the optical ray to the object can be obtained from the diameter and coordinates in the image. In these studies, various camera systems using plane cameras, fisheye cameras, or omnidirectional cameras are used. Because these camera systems have different geometrical optics, one simple image position measurement method cannot yield the position and posture. Therefore, we propose a new method that measures the position from the size of three-dimensional landmarks using omnidirectional cameras. Three-dimensional measurements are performed by these omnidirectional cameras using the distance and direction to the object. This method can measure three-dimensional positions from the direction and distance of the ray; therefore, if the optical path such as the reflection or refraction is known, it can perform measurements using a different optical system’s camera. In this study, we construct a method to obtain the relative position and relative posture necessary for the self-position estimation based on an object with an omnidirectional camera; further, we verify this method by experiment.
Integrated Navigation for Autonomous Drone in GPS and GPS-Denied Environments
Authors: Suzuki Satoshi ,   Faculty of Textile Science and Technology, Shinshu University 3-15-1 Tokida, Ueda-shi, Nagano 386-8567, Japan
Published: June 2018

In this study, a novel robust navigation system for a drone in global positioning system (GPS) and GPS-denied environments is proposed. In general, the drone uses position and velocity information from GPS for guidance and control. However, GPS cannot be used in several environments; for example, GPS exhibits huge errors near buildings and trees, indoor environments. In such GPS-denied environments, a Laser Imaging Detection and Ranging (LIDAR) sensor-based navigation system has generally been used. However, the LIDAR sensor also has a weakness, and it cannot be used in an open outdoor environment where GPS can be used. Therefore, it is advantageous to develop an integrated navigation system that operates seamlessly in both GPS and GPS-denied environments. In this study, an integrated navigation system for the drone using GPS and LIDAR was developed. The design of the navigation system is based on the extended Kalman filter, and the effectiveness of the developed system is verified by numerical simulation and experiment.
Acquisition of Disaster Emergency Information Using a Terrain Database by Flying Robots
Authors: Miyazaki Yasuki , Hirano Takafumi , Kobayashi Takaaki , Imai Yoshihiro , Usuki Shin , Kobayashi Yuichi , Terabayashi Kenji , Miura Kenjiro T. ,   Shizuoka University 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan,   Yokohama National University 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan,   University of Toyama 3190 Gofuku, Toyama-shi, Toyama 930-8555, Japan
Published: June 2018

Because of the frequent occurrence of large-scale disasters, such as earthquakes, tsunamis, volcanic eruptions, and river floods, there is an increased demand for emergency response, restoration, and disaster prevention using robotic technology. One such technology involves assessment of the damage status using flying robots, which have undergone rapid development in recent years. In this study, using images of the disaster site obtained from a flying robot and a terrain database consisting of predisaster 3-D data, we aim to detect efficiently the collapse of electric utility poles, which are man-made objects, and the water level difference before and after river flooding, which is part of the natural landscape. By detecting these disaster-related events, we show the validity of the proposed method to assess the damage situation using the terrain database.
Development of Educational Service Robot and Practical Training
Authors: Yabu Atsuo ,   Osaka Prefecture University College of Technology 26-12 Saiwaicho, Neyagawa-city, Osaka 572-8572, Japan, Kaneda Tadahiro , Maeda Issei , Sakurai Wataru
Published: June 2018

As robot workshops for elementary and junior-high school students are being held across Japan, there is a large variety of teaching-material robots available for them. An increasing number of freshmen at colleges or universities already undertake some basic education on robotics before they enter a college or a university. On the other hand, as research and development of service robots is being promoted as a part of the measures to cope with the declining birthrate and the aging population of Japan, service robots are expected to come into much wider use. Under these circumstances, it is imperative for universities and technical colleges to enrich the contents of their robotics education, especially on service robots. However, there are no robots available as teaching materials. Therefore, we developed an educational service robot and used it to conduct practical trainings with the aim of motivating students to develop robots, as well as enhancing their motivations. This paper reports on the details of this project.
Sosyal Medya Kullanım Bozukluğu Ölçeği’nin Türk Kültürüne Uyarlanması: Geçerlik ve Güvenirlik Çalışması
Authors: SARIÇAM Hakan , ADAM KARDUZ Fatıma Firdevs
Published: June 2018

Bu çalışmada Sosyal Medya Kullanım Bozukluğu Ölçeği’nin (SMKBÖ-9) Türk
ergenlerde geçerlik ve güvenirliğini test etmek ve psikometrik özelliklerini
incelemek amaçlanmıştır. Araştırma kapsamına yaşları 13 ile 18 arasında değişen
üç farklı çalışma grubunda yer alan toplam 586 (202+204+180) ergen alınmıştır. Açımlayıcı
faktör analizi sonuçlarına göre SMKBÖ’nün Türkçe formunun orijinalindeki gibi
tek boyuta sahip olduğu ve bu tek boyutlu yapının ölçtüğü özellikle ilgili
toplam varyansın %48.11’ini açıkladığı görülmüştür. Doğrulayıcı faktör analizi
sonucu ölçeğin uyum iyiliği değerleri χ²/sd=1.87, RMSEA=.066, CFI=.98, GFI=.98,
IFI=.98, NFI=.96, RFI=.97 ve SRMR=.039 olarak hesaplanmıştır. Ayrıca madde
faktör yükleri de .35 ile .76 arasında sıralanmaktadır. Eşdeğer ölçek (ölçüt)
geçerliği çalışmasında Sosyal Medya Kullanım Bozukluğu Ölçeği ile Young
İnternet Bağımlılığı Testi-Kısa Formu ve Ergenler için Akıllı Telefon
Bağımlılığı-Kısa Formu arasında sırasıyla r=
.64, .66 ilişkiler tespit edilmiştir. Cronbach alfa iç tutarlık katsayısı .75,
Guttman iki yarı test güvenirlik katsayısı .64 olarak bulunmuştur. Düzeltilmiş
madde toplam korelasyon katsayıları .29 ile .73 arasında değişmektedir. Tüm bu
sonuçlar, Sosyal Medya Kullanım Bozukluğu Ölçeği’nin Türk ergenlerde
kullanılabilecek geçerli ve güvenilir bir ölçme aracı olduğunu göstermiştir.
Merkezsizleştirme Becerisini Değerlendirme: Yaşantılar Ölçeğinin Türkçe Formunun Psikometrik Özellikleri
Authors: ÜNLÜ KAYNAKÇI Fatma Zehra
Published: June 2018

Bu çalışmada, bilinçli
farkındalığa dayalı yaklaşımların ortak unsuru olarak görülen merkezsizleştirme
becerisini ölçen Yaşantılar Ölçeğinin 
(Fresco ve diğ., 2007) Türkçeye uyarlamasının yapılması amaçlanmıştır.
Katlımcılar, Ankara’da bir devlet üniversitesinde okumakta olan 363 üniversite
öğrencisinden (251 kadın, 112 erkek) oluşmaktadır. Yaşantılar Ölçeğinin tek faktörlü
yapısını test etmek için Doğrulayıcı Faktör Analizi (DFA) yapılmıştır. DFA bulguları,
ölçeğin tek faktörlü yapısının doğrulandığını göstermiştir (Satorra-Bentler χ2/df = 3.05 (p < .001), RMSEA = .07, NNFI = .93, CFI = .94, SRMR = .06, NFI = .92 ). Yaşantılar Ölçeğinin, merkezsizleştirme boyutunun Cronbach-α
katsayısı .80 olarak bulunmuştur. Ayrıca ölçeğin ölçüt bağıntılı geçerliğini test etmek için Ruminasyon Ölçeği Kısa Formu
(Treynor, Gonzealez ve Nolen-Hoeksama, 2003) ve Yaşantılar Ölçeği –
Merkezsizleştirme arasındaki ilişki 620 üniversite öğrencisinin katılımıyla
incelenmiştir. Ruminasyon ve merkezsizleştirme arasında negatif yönde anlamlı
ilişki bulunmuştur. Sonuç olarak, üniversite öğrencilerinin katılımı ile gerçekleştirilen bu çalışmada
Yaşantılar Ölçeği - Merkezsizleştirme Türkçe formunun geçerli ve güvenilir bir
ölçme aracı olduğuna dair bulgular elde edilmiştir. Elde edilen
bulgular,  alan yazın ışığında tartışılmıştır.
Discitis in Adults
Authors: Shenoy Kartik , Singla Amit , Krystal Jonathan D. , Razi Afshin E. , Kim Yong H. , Sharan Alok D.
Published: June 2018

* Discitis is a bacterial infection of the intervertebral disc that is commonly caused by direct inoculation from surgery or hematogenous seeding.

* Rapid diagnosis and treatment are essential to preserve spinal stability and neurological function.

* Discitis is usually treated nonoperatively with antibiotics. However, when surgical intervention is indicated, debridement and intervertebral fusion are often performed to promote healing, limit neurological impairment, and restore spinal stability.
Water Performance in Toe-Point Injection Wellbores at Supercritical State
Authors: Sun Fengrui , Yao Yuedong , Li Guozhen , Zhao Lin , Liu Hao , Li Xiangfang
Published: June 2018

Most of the previous works were focused on the saturated/superheated steam flow in wellbores coupled with conventional single-tubing injection method. With the rapid development of technology. Supercritical water coupled with toe-point injection technique is proposed.

Compared with conventional method, supercritical water could heat the reservoir to a higher temperature, obtain a larger heated radius, and obtain a higher thermal cracking efficiency etc. Besides, toe-point alternating heel-point injection could release the phenomenon of unequal absorption of steam when the horizontal wellbore is extremely long or the reservoir is of serious heterogeneity.

This paper presents a model for estimating thermal properties of supercritical water along the inner tubing (IT) and annuli in the horizontal section of the wellbores with toe-point injection technique. Firstly, a flow model in wellbores is proposed based on the mass, energy and momentum conservation equations. Secondly, coupled with flow model in reservoir, a comprehensive mathematical model is proposed. Thirdly, type curves of supercritical water flow in horizontal wellbores with toe-point injection technique is obtained by finite difference method on space and iteration technique. Finally, sensitivity analysis is conducted.

Results show that: (a) supercritical water temperature decreases rapidly from heel-point to toe-point in IT. The temperature decrease rate near toe-point of wellbores becomes smaller. (b) The larger the pressure difference, the larger the mass injection rate from annuli to oil layer. (c) When the mass injection rate is small, heat loss from fluid to reservoir plays an important role on temperature drop. (d) When the injection rate is high enough, the effect of heat loss on temperature drop becomes weak. (e) The pressure of supercritical water at a certain place in IT or annuli decreases with injection rate.
Alternate Imbalance Operating-Pressure Process Improving SAGD Performance of Foamy Extra-Heavy Oil Reservoirs in the Eastern Orinoco Belt, Venezuela
Authors: Yang Zhaopeng , Li Xingmin , Chen Heping , Liu Zhangcong , Luo Yanyan , Fang Lichun
Published: June 2018

The foamy extra-heavy oil reservoirs in the eastern Orinoco Belt, Venezuela with high initial dissolved gas oil ratio and flow ability in situ, have been exploited by the Cold Heavy Oil Production (CHOP) method, with recovery of only 8%-12% OOIP. SAGD has proved to be one of commercially active post-CHOP processes. Whereas during the SAGD process the dissolved gas as non-condensable gas accumulated at the edges of the steam chamber causes a resistance to heat transfer between steam and oil, thus slowing down growth of the steam chamber and oil recovery. Therefore a novel SAGD process using alternate imbalance operating-pressure (AIOP-SAGD) is studied for the purpose of improving foamy oil SAGD performance.

The novel SAGD process involves multi SAGD well pairs, and with the growth of steam chambers, a significant pressure gradient is deliberately created between two steam injection wells. Moreover the higher and lower operation pressure of the two injection wells is periodically alternate. In this work, the potential evaluation and optimization of foamy oil AIOP-SAGD are studied, through extensive simulations utilizing a sector model, which is from a sector with representative oil and reservoir characteristics of Eastern Orinoco Belt, considering the mechanism of foamy oil and thermal recovery.

Simulation results indicate that the AIOP-SAGD process shows significant improvement in oil recovery, at least 10% higher than traditional SAGD. The mechanism includes two aspects: firstly the pressure gradient between two adjacent SAGD well pairs brings a sweep of dissolved gas from steam chambers; secondly, based on the flow ability of foamy extra-heavy oil, the pressure gradient helps to exploit oil between two SAGD pairs which is typically difficult to be recovered with conventional SAGD. The optimization of operating parameters shows that the optimal start time of AIOP-SAGD is when the oil rate of SAGD reaches the peak and the steam chamber extends to the top of the reservoir. High steam quality helps improve the performance of AIOP-SAGD. Moreover the parameters of alternate time, imbalance time, imbalance pressure difference were optimized.
Formation Damage Characterization of Horizontal Well in Extra-Heavy Oil Reservoir and Methods of Remedy
Authors: Liu Zhangcong , Chen Changchun , Lv Xue , Yang Zhaopeng , Shen Yang , Luo Yanyan , Li Xingmin
Published: June 2018

Primary production using horizontal wells has been successfully applied in extra-heavy oil reservoirs, heavy oil belt, Orinoco, Venezuela. During drilling period, formation damage due to drilling fluid invasion lowers the effective permeability around the well, leads to higher pressure drop and has detrimental impact on well productivity in such pressure depleted reservoirs.

In this study, laboratory experiments of drilling fluid invasion are conducted to identify damage mechanism. The oil sample used in the test is taken from Block J, Orinoco Belt and the formation temperature is restored in the lab to mimic the process of drilling fluid mixing with crude oil in horizontal drilling. The stable emulsion is formed by mixing the crude oil with drilling fluid in different proportions. Furthermore, damage level is quantified by well test interpretation. Skin factor, wellbore storage and other formation parameters are estimated by deconvolution method based on three build-ups. Finally, acid washing and well bottomhole electric heating, two methods of remedy are applied in oilfield.

Experiment results show that low productivity of the horizontal wells is due to the presence of highly viscous emulsion system stabilized by large amount of calcium carbonate in drilling fluid. The emulsion system restricts reservoir fluid flowing from the formation to the slotted liner. In Block J, constrained by the operational problems, the effective shut-in time is commonly short. Conventional well test method can hardly give the reliable results. Compared with the conventional method, deconvolution method can solve the data limitation, minimize the initial distortion caused by wellbore storage and get more reliable results. The production can be improved temporarily after the acid washing while declines rapidly. Electric heating can obviously improve the oil mobility near wellbore and maintain stable production.

This paper combines both lab studies and well test interpretation to characterize the formation damage, provides guidance for the remedial operations to improve well productivity.
EUR Prediction for Unconventional Reservoirs: State of the Art and Field Case
Authors: Mahmoud Omar , Ibrahim Mazher , Pieprzica Chester , Larsen Shane
Published: June 2018

Forecasting future production and estimating ultimate recovery (EUR) in supertight reservoirs and shale plays has long been problematic. Developing a reliable and more accurate production forecast have always been a main goal of any petroleum operation. Effectively assessing the reservoir volume and well producing life is instrumental for creation of development scenarios and strategies to maximize the value to the company. Different models have been introduced and used for reserves estimation and production forecast of unconventional reservoirs. This work is intended to review and compare the methods and models currently used in the industry.

Reserves estimation is a process that is constantly updated during the life of a reservoir. Its accuracy depends on the amount of data available and the method of forecast. Analytical models or rate transient analysis (RTA) methods are widely used for history matching and production forecast of unconventional reservoirs. Numerical simulation is also used for estimating ultimate recovery. Different relations have been introduced to model the rate/time behavior in unconventional plays as an alternative to the Arps’ decline curve analysis to address shortcomings when matching production history. Modified hyperbolic decline, power-law exponential decline (PLED), stretched-exponential decline (SEPD), Duong's method, and logistic-growth model (LGM) are developed for forecasting the production in shale reservoirs, but all are based on empirical observations of a particular scenario.

In this study, different methods of history matching the production of hydraulically fractured unconventional reservoirs were investigated by forecasting future production and predicting EUR's to quantify the differences between them. The traditional Arps’ decline for low permeability reservoirs over-forecasts reserves. PLED, SEPD, LGM, and Duong's method were intended to represent the character of rate/time production data for the standard well completion in a multiple-fractured horizontal well in a shale play. These methods provide different forecasts as they have different equation forms. Unfortunately, all of them are not satisfactorily sufficient to forecast production for all unconventional reservoirs. The RTA analytical models required certain modifications of the reservoir and fracture parameters to provide optimistic EUR when compared to the numerical simulation.

Different methods for forecasting unconventional well data have been reviewed and compared in this work based on the production forecast and EUR prediction. Field case production data has been used to reveal the accuracy of the models, the similarity of reserves estimation, and the relationship to the reservoir theory.
An investigation into the Combination of Cyclic Steam Stimulation and Cyclic CO2 Stimulation for Heavy Oil Recovery in Trinidad and Tobago
Authors: Bobb Janos , Hosein Raffie
Published: June 2018

More than four billion barrels of heavy oil remain in the oil fields of Trinidad. If these oil fields are exploited, the country's total oil production can increase significantly. However, heavy oil is difficult to produce, due to its high viscosity, and only a small fraction is recovered after primary recovery. Therefore, it is necessary to implement enhanced oil recovery (EOR) techniques to increase heavy oil production. Two of the most commonly used EOR techniques are cyclic steam stimulation (CSS) and cyclic CO2 stimulation (CCO2S). These processes have a long history of successful heavy oil recovery in Trinidad and Tobago when applied individually. However, very little research was found regarding the combination of both processes which was the basis for this study

A test reservoir, located in the southern basin on land Trinidad was selected and a computer simulation model was built, using the Computer Modelling Group (CMG) software to determine the production analysis. Sand, structure and pay maps were obtained and digitized, using the Didger Five software and then uploaded into the CMG software. Reservoir properties and production data were also uploaded. Wells were then added to the model at the exact location indicated on the structure map. Simulations were conducted using varying injection rates, slug size and soak times for CSS, CCO2S and combined CSS and CCO2S to determine optimal EOR performance and production.

The combination of CSS and CCO2S show an increase in recovery by 8.6% and to be profitable at oil prices higher than USD 14/bbl. It is also best used as a first step for other enhanced oil recovery techniques to further increase recovery. In addition, the results show that 8 out of 17 wells were more responsive to CSS and CCO2S when applied individually than when combined.
Bio-Oil Dispersants Effectiveness on AsphalteneSludge During Carbonate Acidizing Treatment
Authors: Alrashidi Hessah , Farid Ibrahim Ahmed , Nasr-El-Din Hisham
Published: June 2018

Matrix acidizing is a remedial well stimulation that done to overcome formation damage near wellbore or improve the permeability. Although acidizing treatments are proven and abundant there is still inherit from formation damage when pumped. Acid-induced asphaltene sludging is becoming an increasing cause of oil well stimulation Failure.

The objective of the paper is to evaluate the performance of coconut oil as a bio-oil dispersant against commercial dispersants in preventing asphaltene sludge while acidizing carbonate cores with 15 wt.% HCl and a chelating agent. A Kuwaiti crude oil was used in this study has an API of 38° and 2% asphaltene content. The crude oil was characterized by a variety of analytical techniques including total acid and base numbers (TAN, TBN), saturates, aromatics, resins and asphaltene analysis (SARA), density, viscosity and elemental analysis. Indiana limestone cores were used with average porosity of 16% and permeability ranges (9-13) md. X-ray diffraction (XRD) was used to analyze the mineral and clay content in the cores. Sludge tests were used to examine the acid and oil compatibility using anaging cell under 500 psi and 160°F with oil to an acid ratio of 1:1. Coreflooding experiments under reservoir condition were done with the selected two acid systems, 15 wt. % HCl and achelating agent. Indiana limestone cores with a permeability of 7-12 md were initially saturated with the crude oil then acid was injected until breakthrough. The injected acid volume was recorded and CT-scan imaging of the cores after the acid treatment was used to evaluate the structure and the propagation of the wormhole. The effluent fluids were analyzed by inductively coupled plasma (ICP) and pH measurements.

The results for a Kuwaiti crude oil showed the formation of 13 wt% sludge with 15 wt% HCl and it increased to 19 and 30 wt% with increasing acid concentrations to 20 and 28 wt%, respectively. The presence of iron(III) in the system increased the sludge precipitation to 17.8 wt% at 15 wt% HCl and 3,000 ppm iron concentration. The sludging decreased to 7.5 wt% by adding 300 ppm coconut oil to the system. The formation of asphaltene sludge in the carbonate acidizing retards the wormhole propagation. Hence, the injected acid volume to the breakthrough decreased from 1 to 0.4 by adding 300 ppm coconut oil to the acid system. A conical wormhole was formed with the injection of 15 wt% HCl, comparing to a uniform wormhole in the presence of coconut on the acid system. In the case of stimulating the cores with achelating agent (20 wt% GLDA), the coconut oil exceeds the expectations with the minimum pore volume needed to breakthrough compared to the GLDA alone or with the chemical dispersant B.

This study concluded that the use of dispersant can help reduce the asphaltene sludge and create better acid propagation through the core. The results can be employed to design the optimum acid formulation and create the desired wormhole in carbonate formations.
Re-Evaluating Contributions from Thin Bedded Reservoirs: Integrated Reservoir Modelling of the Greater Dolphin Area
Authors: Ryan Damien , Crooks-Smith Nwenna , Nurafza Peyman , Ogiste Candice , Calvert Stefan
Published: June 2018

The Dolphin Field has been producing gas since 1996, however predicting in place volumes, reserves and forecasting production has been a challenge since field inception. The fact that in place estimates have increased significantly since development sanction highlights that a range of geophysical, geological and petrophysical uncertainties are associated with the field. Historically, static volumes have been smaller than dynamic volumes estimated from material balance. The explanation of this difference traditionally related to uncertainty in contact depth (given the minimal data on contacts), that adversely caused poor predictions of water production in the historical models.

Many of the reservoir units within the Greater Dolphin Area (GDA) are characterised by a heterolithic deltaic succession of centimeter scale very-fine sandstone, siltstone and mudstone. Given the thin-bedded nature of the reservoir, conventional wireline-logging tools lack the resolution to accurately resolve many of the static parameters including water saturation. However, based on the available PLT data, it is believed that these thin-bedded intervals generally contribute to the production from the wells and hence to the fluid flow in the reservoir.

A new static and dynamic reservoir model of the GDA has been built that integrates and incorporates new seismic interpretation, petrophysical recharacterization, revised geological and reservoir engineering concepts, and eventually history matching to production data. A key component of this new model build has been integrated modelling iterations amongst different disciplines from new petrophysical interpretations through to dynamic simulation. Initial iterations used a conventional formation evaluation method and resulted in simulations that showed accelerated pressure drops (compared to production data) as a result of failure to capture flow from thin-beded intervals. An alternative petrophysical methodology that aims to better estimate water saturation within thin bedded intervals has been incorporated into a new workflow to account for the thin bed volumes. The new thin bed simulation model results in greater gas contributions from the thin-bedded intervals and helps overcome the historical shortage of static volumes required to achieve a pressure match.
The Upper Cretaceous of Trinidad, is there an Unconventional Source Rock Play?
Authors: Archie Curtis
Published: June 2018

To date Trinidad has produced close to three billion barrels of oil from onshore and offshore fields. Formations penetrated range in age from the Lower Cretaceous to the Pleistocene.

Ninety three wells have been drilled to the Cretaceous with varying degrees of success, these wells have identified whether source rock facies are present or absent across the island. Based on well and outcrop data, the Upper Cretaceous interval is shale dominated with occasional turbidite sandstone reservoirs and a siliceous mudstone locally known as "Argilline".

Geochemical research by Kuarsingh (1986), Rodrigues (1987, 1988, 1993), Talukdar et al (1990), Requejo (1991), Persad et al (1993), Requejo et al (1994), Baseline/DGSI (2004) indicated that most of the hydrocarbons in Trinidad have been sourced from Type II kerogens contained in Cenomanian-Santonian and Aptian aged marine shales of the Naparima Hill and Gautier Formations respectively, Maastrichtian and Tertiary sediments are dominated by mainly woody and coaly kerogens. Total Organic Contents range from 0.1 to +\- 9%.

Rodrigues (1989) mapped the distribution of geothermal gradients identifying hot and cold areas, this data has implications for petroleum systems modeling, especially for the timing and top of the oil generating window.

Royalty Lease Evaluation (RLE) analysis of oils produced from Upper Cretaceous sandstone and naturally fractured intervals (Specific gravity / API, viscosity, % Sulphur, % of products by distillation) give clues to the origin and history of these oils.

Integration of these results and data can result in identification of areas with potentials unconventional source rock plays.
Application of Rotating Magnet Ranging System and An Innovative Concept of Heat Recycling in SAGD Operation
Authors: Jin Fu , Shunyuan Zhang , Bingshan Liu , Bo Li , Lisheng Chen
Published: June 2018

As a kind of methodology to develop coalbed methane in China, RMRS (Rotating Magnet Ranging System) has been popular in SAGD operation in recent years. In Liaohe Oilfield SAGD (Steam Assisted Gravity Drainage) is becoming a more and more mature methodology. In a pair of parallel wells high pressure steam is injected into a horizontal well to drain heavy oil into the lower production well. However, not all thermal resources have not been exploited, such as heat of the hot production fluid, flue gas and hot brine separated by the steam-water separator in the boiler.

Trials and researches were finalized on many dual-horizontal wells in Liaohe Oilfield to learn about the present situation and technical capabilities, while thermodynamic models of various types were established and experimental means were applied to analyze thermal distribution and each of the thermal sources previously mentioned. Effects of various media, flow rates and temperatures on thermal utilization and heat deficit rates were studied on the assumption that one ton crude oil was produced per hour.

Waste heat of flue gas may be utilized to help combust air and the thermo-coil may be used as the air preheater, which improves boiler’s heat efficiency. The high temperature production fluid may be used to heat water in the boiler first and then used as the heat source of the absorption heat pump, so that heat is transferred from the low temperature heat source to the high temperature heat source and the low grade heat energy is recycled. As a high grade waste heat, the HPHT brine that is separated from moist steam in the boiler takes up twenty percent of the total water and shall not be only used to heat injected water. Instead, it may be used to achieve flash evaporation. Thus, waste water is heated and distilled water is recycled.

The waste heat recyling model applies thermo-coil air preheaters to recycle flue gas and flash evaporated hot brine to evaporate waste water. Beside, hot production fluid is recycled to heat boiler water. On a basis of the same fuel consumption volume, the recovery rate and marketability of crude oil are both improved.