bluuebunny/crossref_metadata_2025 huggingface dataset:
Bioinspired Temperature Responsive Multilayer Films and Their Performance under Thermal Fatigue
Authors: Athanasopoulos Nikolaos , Siakavellas Nicolaos J.
Published: June 2018

In Nature, it is common for living plants and non-living plant tissues to consist of materials with anisotropic multilayer and non-homogenous structure. The structure of tissues determines their self-shaping and self-folding capabilities in response to a stimulus in order to activate different functionalities. Predetermined movements are realized according to changes in environmental conditions, which trigger the fibrous anisotropic structure of the plants’ material. In this study, we present the fabrication process of low-cost anisotropic multilayer materials that are capable of realizing complex movements caused by small temperature changes (<40 oC). The mismatch in the thermo-mechanical properties between three or more anisotropic thin layers creates responsive materials that alter their shape owing to the developed internal stresses. Isotropic layers can perform only bending movements, whereas anisotropic multilayer materials can perform bending, twisting or complex combined modes. The movements of the material can be controlled by forming anisotropic homogenous metallic strips over an anisotropic polymer. As a result, inexpensive responsive materials can be developed to passively react to a very broad range of thermal requirements. We studied the major parameters that affect the sensitivity of the developed materials, as well as their failure modes and crack formation under thermal fatigue conditions.
A 35 MHz/105 MHz Dual-Element Focused Transducer for Intravascular Ultrasound Tissue Imaging Using the Third Harmonic
Authors: Lee Junsu , Moon Ju-Young , Chang Jin Ho
Published: June 2018

The superharmonic imaging of tissue has the potential for high spatial and contrast resolutions, compared to the fundamental and second harmonic imaging. For this technique, the spectral bandwidth of an ultrasound transducer is divided for transmission of ultrasound and reception of its superharmonics (i.e., higher than the second harmonic). Due to the spectral division for the transmission and reception, transmitted ultrasound energy is not sufficient to induce superharmonics in media without using contrast agents, and it is difficult that a transducer has a -6-dB fractional bandwidth of higher than 100%. For the superharmonic imaging of tissue, thus, multi-frequency array transducers are the best choice if available; transmit and receive elements are separate and have different center frequencies. However, the construction of a multi-frequency transducer for intravascular ultrasound (IVUS) imaging is particularly demanding because of its small size of less than 1 mm. Here, we report a recently developed dual-element focused IVUS transducer for the third harmonic imaging of tissue, which consists of a 35-MHz element for ultrasound transmission and a 105-MHz element for third harmonic reception. For high quality third harmonic imaging, both elements were fabricated to have the same focus at 2.5 mm. The results of tissue mimicking phantom tests demonstrated that the third harmonic images produced by the developed transducer had higher spatial resolution and deeper imaging depth than the fundamental images.
Botulinum Neurotoxin F Subtypes Cleaving the VAMP-2 Q58-K59 Peptide Bond Exhibit Unique Catalytic Properties and Substrate Specificities
Authors: Sikorra Stefan , Skiba Martin , Dorner Martin B. , Weisemann Jasmin , Weil Mirjam , Valdezate Sylvia , Davletov Bazbek , Rummel Andreas , Dorner Brigitte G. , Binz Thomas
Published: June 2018

In the recent past about 40 botulinum neurotoxin (BoNT) subtypes belonging to serotypes A, B, E, and F pathogenic to humans were identified among hundreds of independent isolates. BoNTs are the etiological factors of botulism and represent potential bioweapons, but are also recognized pharmaceuticals for efficient counteraction of hyperactive nerve terminals in a variety of human diseases. The detailed biochemical characterization of subtypes as the basis for development of suitable countermeasures and possible novel therapeutic applications is lagging behind the increase in new subtypes. Here we report the primary structure of a ninth subtype of BoNT/F. Its amino acid sequence diverges by at least 8.4% at the holotoxin and 13.4% on the enzymatic domain level from all other known BoNT/F subtypes. We found that BoNT/F9 shares the scissile Q58/K59 bond in its substrate vesicle associated membrane protein 2 with the prototype BoNT/F1. Comparative biochemical analyses of four BoNT/F enzymatic domains showed that the catalytic efficiencies decrease in the order F1 > F7 > F9 > F6 and vary by up to factor eight. KM values increase in the order F1 > F9 > F6 ≈ F7, whereas kcat decreases in the order F7 > F1 > F9 > F6. Comparative substrate scanning mutagenesis studies revealed a unique pattern of crucial substrate residues for each subtype. Based upon structural coordinates of F1 bound to an inhibitor polypeptide the mutational analyses suggest different substrate interactions in the substrate binding channel of each subtype.
Ahmed Glaucoma Valve Implantation: Graft-Free Short Tunnel Small Flap versus Scleral Patch Graft After 1 Year Follow-Up: A Randomised Clinical Trial
Authors: Pakravan Mohammad , Hatami Mohammadmehdi , Esfandiari Hamed , Yazdani Shahin , Doozandeh Azadeh , Kheiri Bahareh , Conner Ian
Published: June 2018

Purpose: To compare the efficacy and safety of graft-free short tunnel small flap (STSF) technique with that of scleral patch graft (SPG) in Ahmed glaucoma valve (AGV) implantation.  Design: Randomized clinical trial.  Participants: Eighty-eyes of eighty patients with medically uncontrolled glaucoma including 41 in STSF and 39 eyes in SPG. Methods: Patients were enrolled and assigned randomly to STSF or SPG.  Main Outcome Measures: tube exposure, Intraocular pressure (IOP), number of glaucoma medications, best corrected visual acuity (BCVA), surgical complications, and success rate ( defined as intraocular pressure (IOP) >5 mmHg, ≤21 mmHg, and IOP reduction ≥20% from baseline at two consecutive visits after three months, no reoperation for glaucoma).  Results: only one case in SPG developed tube exposure at 1-year follow-up. The cumulative probability of success during the first year of follow-up was 70% in the STSF and 65% in SPG (P = 0.36). IOP decreased significantly from 29.6 ± 8.6 mmHg at baseline to 16.4 ± 3.6 mmHg at the final follow-up in STSF (p = 0.001). The corresponding numbers for SPG were 30.9 ± 11.2 and 15.8 ± 4.7, respectively (p = 0.001). The final IOP was comparable between both groups (p = 0.65). Mean ± standard deviation of the number of glaucoma medications was 1.8 ± 0.9 in STSF and 1.6 ± 0.9 in SPG at final follow-up (P = 0.32). Postoperative complications developed in 8 patients (19%) in STSF and 9 patients (23%) in SPG (P = 0.81).  Conclusions: STSF and SPG techniques had comparable complication rate at one-year follow-up. Both techniques were comparable in terms of success rate, postoperative IOP, and glaucoma medications.
Medical Geology and Health: An Approach to Address Diseases Related to Natural Environment-Reviewing the Ghanaian Situation
Authors: ARHIN Emmanuel , Kazapoe Raymond , Mahamuda Abu
Published: June 2018

Inadequate data linking geology and health in Developing Countries contributes immensely to the challenges to identify sources and causes of many of the emerging diseases. Deficiencies and toxicities of trace elements generally impact human and animal health. The review of the geology of Ghana suggests the presence of oxides and sulphide minerals that are released into the natural environment during the geological process of weathering which introduce both essential and, potentially harmful elements. Of great concern is the fact that majority of the Ghanaian population eat locally cultivated food and expect to be nourished from the diet. Furthermore, archived reports on Ghana rural drinking water indicates most of the aquifers are enriched in As and F while deficient in Mg. Medical geology, the emerging discipline that attempts to address the environmental health issues emanating from geological processes is known in developed nations but not much of its activities are recognized in Ghana. This review has identified the concentrations of a number of elements in different geological settings and have linked these concentrations with health issues. There is therefore a need for medical geologists to work together with other disciplines to devise preventive as well as mitigative techniques in addressing many geology related health issues in Ghana.
Online Demand Side Management with PEVs Using Stochastic Optimization
Authors: Acquah Moses , Yu Byeonggu , Han Sekyung
Published: June 2018

This study purposes the use of plug-in electric vehicles for demand side management (DSM) considering uncertainties in demand as well as uncertainties due to mobility of PEV to mitigate peak demand. The solution also seeks to reduce electric cost in addition to reducing the effects of greenhouse gases. In recent years DSM using distributed storage system such as battery energy management system (BESS) and plugged-in electric vehicles (PEV) have become very prevalent with most implementations resorting to deterministic load forecast. These methods do not consider the potential growth in demand making their solutions less robust. In this study we propose a real-time density demand forecast and stochastic optimization for robust operation of PEV for a building. This method accounts for demand uncertainties in addition to uncertainties in mobile energy storage as found in PEV, making the resulting solution robust as compared to the deterministic case. A case study on a real site in South Korea is used for verification and testing. The proposed study is verified and tested against existing algorithms. The result verifies the effectiveness of the proposed approach
An Improved Method for Impervious Surface Mapping Incorporating Lidar Data and High-Resolution Imagery at Different Acquisition Times
Authors: Luo Hui , Wang Le , Wu Chen , Zhang Lei
Published: June 2018

Impervious surface mapping with high-resolution remote sensing imagery has attracted increasing interest as it can provide detailed information for urban structure and distribution. Previous studies have suggested that the combination of LiDAR data and high-resolution imagery for impervious surface mapping performs better than using only high-resolution imagery. However, due to the high cost of the acquisition of LiDAR data, it is difficult to obtain the multi-sensor remote sensing data acquired at the same acquisition time for impervious surface mapping. Consequently, real landscape changes between multi-sensor remote sensing data at different acquisition times would lead to the error of misclassification in impervious surface mapping. This issue has mostly been neglected in previous works. Furthermore, the observation differences generated from multi-sensor data, including the problems of misregistration, missing data in LiDAR data, and shadow in high-resolution images would also challenge the final mapping result in the fusion of LiDAR data and high-resolution images. In order to conquer these problems, we propose an improved impervious surface mapping method incorporating both LiDAR data and high-resolution imagery at different acquisition times in consideration of real landscape changes and observation differences. In the proposed method, a multi-sensor change detection by supervised multivariate alteration detection is employed to obtain changed areas and misregistration areas. The no-data areas in the LiDAR data and the shadow areas in the high-resolution imagery are extracted by independent classification yielded by its corresponding single sensor data. Finally, an object-based post-classification fusion is proposed to take advantage of independent classification results with single-sensor data and the joint classification result with stacked multi-sensor data. Experiments covering the study site in Buffalo, NY, USA demonstrate that our method can accurately detect landscape changes and obviously improve the performance of impervious surface mapping.
Multiple Rotors Hovering Near an Upper or a Side Wall
Authors: Tanabe Yasutada , Sugiura Masahiko , Aoyama Takashi , Sugawara Hideaki , Sunada Shigeru , Yonezawa Koichi , Tokutake Hiroshi ,   Japan Aerospace Exploration Agency (JAXA) 6-13-1 Osawa, Mitaka, Tokyo 181-0015, Japan,   Ryoyu Systems, Co., Ltd. Ryoko South Bldg., 6-19 Oe-cho, Minato-ku, Nagoya-shi, Aichi 455-0024, Japan,   Nagoya University Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan,   Central Research Institute of Electric Power Industry (CRIEPI) 1646 Abiko, Abiko-shi, Chiba 270-1194, Japan,   Kanazawa University Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan
Published: June 2018

The influence of walls on the performance of multiple rotor type drones is numerically simulated. With the current wide-spread applications of autonomously flyable UAVs, there are potential needs to use the drones for inspections and observation near various structures, such as buildings and bridges. The flow fields around multiple rotors are influenced significantly by the existence of an upper or a side wall, so that the thrust, required torque, and other forces and moments are changed. It is found that when a rotor approaches an upper wall, as the distance between the rotor and the upper wall is less than a diameter of the rotor, the thrust suddenly increases, which causes the rotors to collide with the upper wall. When an isolated rotor is operated near a side wall, the thrust decreases and a rolling moment appears to tilt the rotor toward the wall as the distance becomes shorter. For a multiple rotor drone near a side wall, the rotors have different distances from the wall, which causes the whole aircraft tilts toward the wall. From the perspective of safety operations, the multi-rotor drone should be kept away from both the upper wall and the side wall at a distance of at least 1.5 times of the rotor diameter to prevent unexpected motions of the aircraft caused by the wall during hovering flight.
Treatment of Adhesive Capsulitis of the Shoulder
Authors: Yip Michael , Francis Anna-Marie , Roberts Timothy , Rokito Andrew , Zuckerman Joseph D. , Virk Mandeep S.
Published: June 2018

* Idiopathic adhesive capsulitis of the shoulder is a self-limiting condition with gradual improvement in symptoms over a variable period of time (1 to 3 years), although a small subset of patients can have permanent residual symptoms.

* Nonoperative and operative treatments do not alter the long-term natural history of adhesive capsulitis, but they do provide short-term symptomatic relief of pain and improvement in shoulder range of motion.

* There has been no consensus in scientific literature on a single treatment type, nonoperative, operative, or combined, which is more effective in the treatment of adhesive capsulitis.

* There has been a general consensus that nonoperative management is the initial treatment of choice for adhesive capsulitis. Nonoperative treatments such as physical therapy, oral anti-inflammatory medications, corticosteroid injections, and hydrodilatation allow accelerated pain relief and/or improvement in range of motion compared with untreated controls, but these differences are short-term and there is no difference in final outcomes.

* There has been insufficient evidence to support early operative treatment for adhesive capsulitis. However, there has been a general consensus that operative treatment (arthroscopic capsular release and/or manipulation under anesthesia) is an option if nonoperative treatment fails after a period of 6 months.

* Arthroscopic capsular release with or without manipulation results in early relief of pain and improvement in motion compared with nonoperative treatment, but there is no difference in the final outcomes.

* There has been insufficient evidence to make recommendations with regard to the indication for and timing of operative treatment or to the ideal surgical technique for arthroscopic capsular release.
Application of Sand-Ramp Fracturing Pumping Mode in Unconventional Shales Stimulation
Authors: Yang Guangzhi , Zhang Shicheng , Liu Ming
Published: June 2018

Sand-slug fracturing has been the main fracturing pumping mode due to the tightness of shale. This mode makes it easier to inject proppants. However, it may cause poor connectivity in the middle brittle formation due to the discontinuous propping. This paper describes an attempt to fracture the unconventional shales with conventional sand-ramp fracturing pumping mode. The results show that good effect is achieved compared with the sand-slug fracturing mode used in the adjacent wells.

Shale reservoir reconstruction has large construction displacement and high pressure, and it adopts fracturing technology of slickwater and linear glue1. In other blocks, Sand-slug mode causes large amounts of slickwater injecting into the formation. The role of water, in addition to carrying sand and making seams, will also cause "water lock" in the micro-fissure, reducing the gas permeability. Therefore, the large amount of liquid is not good to the reservoir.

The Sand-ramp modes using less fluid and higher sand content2-3, resulting in a greater height and length of the fractures. By using a small amount of proppant, Sand-ramp mode can also achieve high conductivity4, communicating the natural cracks5-7 at the same time. Two wells were designed for Sand-ramp mode in the test area.

Based on the understandings on geological characteristics and formation property, the sand-ramp fracturing pumping mode was designed. Two of six wells in the pad were selected to apply this mode. To maximize the stimulated reservoir volume, slickwater accounted for 40% to 60% of the total injected fluids. 100-mesh quartz sands were pumped in priority to improve the complexity of fracture. Then, the 40-70 mesh ceramsites was pumped with crosslinked gel to support the primary, secondary and natural fractures. The pumping rate is 12-13 cubic meters per minute and no acid is used throughout the whole pumping process.

The maximum proppant concentration of sand-ramp reached to 480 kilogram per cubic meters, which was much higher than that of sand-slugs. As a result, good propped fractures were obtained. Since no fluid sweep was used after the sand-slug, the average fluid injection per stage is declined by 27%, but the average sand injection volume was increased by 17%, which significantly reduced the cost and the possible influence to environment. With the sand-ramp mode, the highest test production of the block was up to 278500 cubic meters per day. This well produced 35 million cubic meters of shale gas in 270 days.

The practicability of the sand-ramp pumping mode used in unconventional shales is proven to be positive, especially in the formation with high horizontal stress difference. However, the development result needs to be continuously studied.
Acidizing Highly Permeable Sandstone Stringers: Drill-in Fluid Damage and Compatibility with Rock Minerals
Authors: Al Moajil Abdullah , Al-Khaldi Mohammed , Hazzazi Hassan , Caliskan Sinan
Published: June 2018

Drilling horizontal and highly permeable sandstone acid-sensitive reservoirs with oil based drilling fluids are normally followed by filter cake and associated organic sludge removal treatments. The acid or cleaning recipes should be compatible with the formation minerals, especially when losses are encountered. The objectives of this paper were to conduct a comprehensive evaluation of HCl/formic acid recipe to dissolve oil-based filter cake, characterize and dissolve associated organic sludges, and assess compatibility with highly permeable acid-sensitive sandstone core plugs.

Filter press experiments were conducted to optimize the fluid recipe. Core flood testing was conducted on sandstone core plugs at 160°F. Compatibility with reservoir fluids were assessed using aging cells. TGA was used to identify organic/inorganic composition of sludge samples XRD and ESEM were used to characterize core plugs and sludge samples. ICP analysis was conducted to analyses effluent from coreflood experiments. GC and GC-MS analysis was conducted to identify and characterize sludge samples. Micro CT scan was used to assess the dissolution of rock minerals.

The removal efficiencies of the oil-based filter cake were between 85-100% by weight using HCl/Formic acid recipe. The characterization of the sludge samples revealed the presence of mainly diesel. The inorganic compounds (50% by weight) were mainly quartz with small amounts of calcite, dolomite, kaolinite, microcline, and pyrite. Maximum solubility of nearly 60 wt% was achieved. Core flooding tests of the acid recipe indicated reduction in permeability of core plug. The coreflood effluent analysis indicated dissolution of mainly Ca, Fe, and Mg with small amounts of Al, Si, and Sr with indication of Si-based precipitation. No major indication of precipitation occured. ESEM and EDS spot analysis of the core plug particles showed the sample was comprised Si, O, Fe, S as the main constituents with small amounts of Al. XRD analysis of the core plug after coreflood testing showed the presence of mainly Quartz and small amounts of Microcline, Pyrite, and Palygorskite. The CT scan of core plug before/after coreflooding indicated the acid dissolved rock minerals. There was no clear indication of core damage or solids plugging.
An Evaluation of Enhanced Oil Recovery Strategies for Extra Heavy Oil Reservoir after Cold Production without Sand in Orinoco, Venezuela
Authors: Bao Yu , He Liangchen , Lv Xue , Shen Yang , Li Xingmin , Liu Zhangcong , Yang Zhaopeng
Published: June 2018

The Orinoco heavy oil belt in Venezuela is one of the largest extra-heavy oil resources in the world. It has become a major goal for the unconventional oil exploitation in these years. Now, the most common production method is to use the horizontal well cold production without sand. It is an economic and commercial process, and with the reservoir of this area have high initial gas to oil ratio (GOR), porosity and permeability with unconsolidated sand. However, after several years' production, the oil rate draws down quickly caused by the reservoir pressure drops; the key challenge of cold production is that the recovery factor (RF) tends to be only between 8% and 12%, implying that the majority of the oil remains in the oil formation. It is necessary to develop viable recovery processes as a follow-up process for cold production. Generally, steam based recovery method was widely used as a follow-up process for cold production. In this paper, steam fracturing (dilation) Cyclic Steam Stimulation (CSS) operation and Non steam fracturing (No dilation) CSS operation by using reservoir simulator is examined for a post cold production in extra heavy oil reservoir, in order to analyze the performance of the oil rate, cumulative steam-to-oil ratio (cSOR), steam depletion zone, greenhouse gas emission and some necessary parameters.

The key component of the steam fracturing (dilation) is the ability to inject high temperature and pressure steam into the formation to fracture the reservoir rock which in turn raises the rock permeability and mobilized the oil by lowering the visocisity. To compare the results of the dilation and no dilation CSS operation, this study reveal that due to the steam is injected into the reservoir by using the same cumulative cold water equivalent (CWE), the steam condensate; pressurized by steam vapour, fracture the formation. Dilation operation achieves higher oil rate, lower cSOR. The result also show that fraturing (dilation) of the reservoir during steam injection relieves the pressure which in turn lowers the steam injection pressure below the case where No dilation operation ouccurs.
Increasing Production Flow Rate and Overall Recovery from Gas Hydrate Reservoirs Using a Combined Steam Flooding-Thermodynamic Inhibitor Technique
Authors: Fakher Sherif , Abdelaal Hesham , Elgahawy Youssef , El Tonbary Ahmed , Imqam Abdulmohsin
Published: June 2018

When producing from gas hydrate reservoirs using steam flooding, since hydrate dissociation is an endothermic reaction, the heat is used up. This results in a decrease in reservoir temperature which causes the hydrate equilibrium conditions to be established again, thus causing hydrate reformation. This research studies the effect of injecting thermodynamic inhibitors during steam injection on overcoming the problem of hydrate reformation which in turn will increase hydrocarbon recovery significantly from hydrate reservoirs. The reservoir model was built based on data collected from previous models found in the literature. After specifying all parameters for the reservoir, and the hydrate layer, a systematic study was performed in order to assess the use of inhibitors with steam flooding. The production methods studied include depressurization, steam flooding, inhibitor injection including both brine and glycol, and finally the combined steam flooding inhibitor injection method. The conditions for the steam flooding were kept the same during all runs in order to be able to compare them. Results indicated that the use of the thermal stimulation alone without inhibitor managed to increase recovery, however, the problem of hydrate reformation occurred which caused a cessation of production. Using inhibitors alone managed to increase recovery as well, however the recovery increase was much less compared to thermal stimulation. The type of inhibitor also played a role in recovery with the glycol producing the most, followed by the brine. By combining both steam flooding and inhibitor injection, the recovery increased significantly more than what was observed when using each of the methods on its own. To the authors' knowledge, no extensive study has been performed by combining both steam flooding and inhibitor to increase hydrocarbon recovery from hydrate reservoirs. This research can help in improving real field gas hydrate projects by making the overall project much more economic by increasing hydrocarbon recovery.
A Newly Developed Mathematical Model to Predict Hydrolyzed Polyacrylamide Crosslinked Polymer Gel Plugging Efficiency in Fractures and High Permeability Features
Authors: Fakher Sherif , Bai Baojun
Published: June 2018

Reservoir heterogeneity is one of the most challenging problems facing the hydrocarbon industry nowadays. It results in excess water production and a substantial reduction in oil recovery from water flooding applications. Gel treatment is one of the most successful applications to overcome reservoir heterogeneity problems by plugging high permeability features in a reservoir. One of the most widely used gels is the Hydrolyzed Polyacrylamide-Chromium Acetate Gel (HPAM/CrAc). This research uses data from 70 sources, including more than 1050 experiments, to perform a thorough data analysis to understand the conditions under which this gel is mainly applied. Histograms, and boxplots were generated revealing the ranges under which this gel can be applied, and the frequency of each range. The histograms and boxplots are each divided into the gel properties, and the core and sand pack properties, thus revealing both the chemical and rock properties' ranges. Three dendrograms were also developed based on their equivalent cluster plots generated. The dendrograms can show the different ranges at which the data was distributed and also tell the extent to which each range is related to the other. A mathematical model was also generated and validated in this study. This model gives a relation between the polymer concentration and the oil residual resistance factor (Frro). This model is extremely important since it can predict the effect of polymer concentration on the reduction of the oil permeability, which can help avoid the excessive reduction in oil permeability. The gel was found to have very good disproportionate permeability reduction (DPR), which indicates that it can reduce the permeability of water much more that the permeability of oil. This research can help in revealing the conditions under which the HPAM/CrAc gel can be applied, which in turn can significantly improve the design of field projects.
Advanced HSP Ceramic Proppants— An Evaluation and Effect of Fines on Proppant Pack Conductivity
Authors: Al Moajil Abdullah , Alghizzi Ahmed , Alsalem Ali , AlDarweesh Sajjad
Published: June 2018

Fracturing fluids are normally injected at high rates and pressures to break the reservoir rock, where proppants ideally are suspended during fluid injection. High strength ceramic proppants are used to overcome hash environments (i.e., high closure stress and temperatures). Advancements in proppant manufacturing further added several characteristics to the proppants, such as self-suspending, multi-phase flow enhancer, and multifactional proppants. The objectives of this study were to compare the performance of HSP and ULW ceramic proppants though proppant characterization, wettability measurements, settling behavior, acid solubility, proppant pack conductivity, and proppant crush resistance.

Fracture cell was used to measure the proppant pack conductivity. Proppant crush resistance was conducted using hydraulic uni-axial loading frame. XRD and XRF were used to characterize proppant samples. Solubility in HCl solutions was examined. Elemental analysis was conducted using ICP. Light transmission and backscattering technique was used to compare the settling behavior of proppant samples. Drop Shape Analyzer was used to measure the contact angle on the surface of proppant samples.

The highest performance proppant among the five-examined proppants was proppant P-1. This was based on the conductivity values obtained, the correlation between conductivity and fines generated, settling behavior, and solubility in HCl acids. Proppant P-5 exhibited non-wetted properties for both water and condensate fluids. ULW proppants (i.e., P-7 and P-8) showed significantly improved suspension properties over the examined HSP proppants. The solubility of the HSP proppants in HCl acid depended on the acid concentration, soaking time, surface area. The solubilities obtained was up to 10 wt% in concentrated HCl acids. High concentrations of Fe were observed in concentrated acid solution (i.e. ~1800 mg/l). Proppant pack conductivity values for examined proppants were relatively similar except for proppants P-3 and P-5.A linear correlation was found between wt% of fines generated and proppant pack conductivity.
Comparison of Various Rate-Decline Analysis Models for Horizontal Wells with Multiple Fractures in Shale gas Reservoirs
Authors: Miao Yanan , Li Xiangfang , Lee John , Zhao Chaojie , Zhou Yunjian , Li Han , Chang Yucui , Lin Wenji , Xiao Zhihua , Wu Nan
Published: June 2018

In recent years, improving the accuracy of production forecast in unconventional reservoirs has been of growing interest to oil and gas industries. Decline curve analysis (DCA) models have been recognized as the most efficient and easiest approaches to estimate gas rate. However, fluid flow regime and well rate decline curves are highly affected by the geological properties of formations. Therefore, the selection of DCA models based on completion designs and geological properties of formations is important for production rate prediction.

Traditional DCA methods, particularly Arps' decline model, was originally developed for predicting boundary dominated hydrocarbon well rate decline, which differs from the dominant long-duration transient flow regime in shale reservoirs. The Stretched Exponential model, the Duong model, the Arps model with a minimum terminal decline rate and the scaling method by Patzek were developed to match and forecast wells with transient flow followed by boundary dominated flow (BDF). In this paper, firstly we developed a new model to estimate production in shale gas reserviors by considering both Knudsen diffusion of bulk gas and surface diffusion of adsorbed gas based on the traditional equation of rate versus square-root-of-time. This proposed model can provide better fits to data in transient linear flow regimes. In addition, a systematic analysis of numerical simulation cases in CMG were performed to compare with the traditional model.

The results demonstrated that, in most cases, our model which is demonstrated in this paper, provide more accurate estimation of reserves for numerically simulated cases compared with the traditional decline methods. Therefore, the work offers critical insights into evaluating production in shale gas reserviors in a more efficient way.
Model of Human Resource Needs for the Upstream Petroleum Sector
Authors: Alleyne Neal A. , Alexander David
Published: June 2018

The petroleum industry needs persons with a wide variety of skills for its efficient operation. A catalogue of these skills is therefore very useful to any entity, be it country or company, entering the petroleum industry. This paper describes the human resource needs of the industry on the basis of the value chain of the industry.

The petroleum value chain starts with activities aimed at searching for and finding petroleum and ends with production and sales of crude oil and natural gas to refineries and end users. The technical needs for each section of the value chain are depicted by a model that describes the skills required from the technician to the professional level in addition to the specialist skills. These specialist skills are not always at the professional level. For each section of the value chain the technical skills are built around a particular discipline such as geoscience or petroleum engineering.

The final result is a three dimensional model with ‘technical complexity’ represented in one dimension, ‘value chain variation’ represented in the second dimension and the different entities in the industry represented by the third or ‘entity’ dimension. Along the ‘entity’ slice of the model e.g. for the regulator, the base skills of the disciplines for each section of the value chain are modified or tuned to the needs of a regulatory body such as the ministry of energy for all sections of the value chain. By way of example, under the prospect generation section of the value chain, the regulator requires geoscientist skills aimed at awarding acreage for exploration, the operating companies require geoscience skills for planning and executing exploration programmes and the service companies focus on the skills for providing exploration services.

The model develops a complete catalogue of skills required to meet the needs of all entities involved in the petroleum industry. This catalogue provides universities and training providers with skills which need to be developed in students in preparation for jobs in the industry.
A Comparative Study of Mathematical Models for Fractured Reservoirs: Anomalous Diffusion and Continuum Approach.
Authors: Karim Md Mostafijul , Hossain M. Enamul , Hashan Mahamudul , Imtiaz Syed
Published: June 2018

This study aims to determine an appropriate representative flow-model of a fractured reservoir after comparing two existing approaches: the anomalous diffusion and the continuum approach. A fractured reservoir is assumed in this paper that drains the fluid in transient condition, to a hydraulically fractured horizontal well. To investigate the comparison, dimensional consistency is maintained for both the anomalous diffusion and the continuum approach. Chen and Raghavan's (2015) model is considered as the anomalous diffusion model with modified boundary conditions. Continuum approach model considers the linear flow in a triple continuum structure that consists of matrix slab, micro-fracture, and hydraulic fracture. An analysis of the pressure response curves and the field data evaluates the proper approach for the analysis of the flow behavior. The solution of the wellbore pressure is derived in Laplace domain and is inverted by the Stehfest algorithm. Slope of the pressure response curve depends on the order of differentiation at the anomalous diffusion model. Conversely, the permeability of the hydraulic fracture controls the transient behavior at the continuum approach. The first set of analyses states that the continuum-based model considers the physical structure of the reservoir and increases the accuracy in the prediction of the reservoir behavior; however, more reservoir parameters are required for new continuum those are difficult to be determined. Alternatively, anomalous diffusion approach requires less parameter compare to the continuum approaches, but a high uncertainty exists in the precise determination of the order of the differentiation or the fractal exponent. The anomalous diffusion shows a good agreement with the synthesized field data at the early time whereas the continuum approach matches better at late time response.
Polymer Flooding Application in Trinidad Heavy Oil Reservoirs
Authors: Dukeran Rajiv , Soroush Mohammad , Alexander David , Shahkarami Alireza , Boodlal Donnie
Published: June 2018

The objective of this paper is to assess the application of polymer flooding in Trinidad heavy oil reservoirs. Uncertainty analyses on several synthetic models have been performed to evaluate how variations in reservoir properties affect the oil recovery factor (RF) and Net Present Value (NPV).

Three (3) phases were conducted for the polymer flooding assessment. Phase 1 included a core flooding simulation to assess the oil viscosity sensitivity region and the ranges of polymer concentration for optimization. Phase 2 carried out uncertainty analysis using synthetic models to optimize polymer flooding with respect to NPV. Phase 3 discussed more detail analysis of parameters effects and confirmed the observations in previous cases using analytical approach.

Three types of polymer were used in the models, Flopaam 3130S, 3430S and 3630S. In core flooding simulation, optimal range of polymer concentration was estimated between 500ppm to 5000ppm. On recovery-viscosity plot, a high viscosity oil requires a higher polymer concentration to have higher recovery. Our results showed that this trend was not always true mainly due to the low reservoir fracture pressure, since a higher concentration and/or a higher molecular weight polymer require higher injection pressure. Uncertainty analysis in Phased 2 to 3 indicated that °API /viscosity, depth, permeability and polymer concentration had the highest effect on RF and NPV.

This paper also presents optimal polymer concentration versus oil viscosity for Trinidad oil reservoirs. Moreover, this work determines the reservoirs where the polymer flooding is applicable and recommend proxy models to estimate RF and NPV versus reservoir parameters.
A Novel Dual Isolation System for Deep Water Injector Standalone Screen Completions
Authors: Roane Tom , Bourgneuf Patrick , Johnson Kenneth , Williams Mark , Chaloupka Vladimir
Published: June 2018

A major operator manages multiple, multiwell deep water projects in West Africa. For two such projects in Congo and Nigeria, it was determined that sand control was necessary and a stand-alone screen (SAS) completion was an efficient and cost-effective means for providing sand control for the majority of wells in both projects. This paper describes a new and unique feature of the SAS completion, called the Dual-Isolation Assembly (DIA), which addresses many challenges, and its application in Nigeria on the Egina Project.

Standard SAS completions incorporate a circulation path down the workstring, through the float shoe, and back to surface through the workstring by casing annulus for circulation, pressure maintenance, and removal of the filter cake at the operation's conclusion. The capability to wash down through the toe of the system while running in the well requires washpipe seals inside the float shoe, which incorporates spring-loaded valves that open during pumping, but close when pumping stops. In addition to the wash-down capability, the washpipe incorporates a shifter for closing an uphole isolation valve with the ability to reopen the valve, if necessary.

For an injector well, the flow path into the formation is through the sand-control screens and float shoe from the inside. The path is the opposite for a producer well, which flows from the formation to inside the screen while the float shoe is closed. Because of the different natures of the flow paths, the float shoe is continuously exercised in an injector well as a result of injection fluid starts and stops. During injection, if the opening pressure of the float shoe spring is exceeded, it could stay open over time, causing loss of integrity of the float shoe. When pumping stops, the flow path into the screen through the float shoe could heave formation particles back into the wellbore, as a result of the reservoir being energized upon injection shutdown. The DIA provides secondary and permanent isolation of the float shoe, as requested by the operator, and is capable of shifting a barrier isolation valve installed in the lower completion to comply with the operator's barrier policy for deepwater wells. The DIA and lower completion design allows the operator to safely place a filter-cake breaker treatment in the open hole after setting a lower completion packer.

In addition to fulfilling the requirements of these SAS completions, the DIA design addresses other potential challenges, such as hydraulic locks and any potential swabbing while manipulating the service tools. This paper describes the evolution of the DIA design and full QA/QC and operational procedures, which led to the successful deployment and excellent functionality of the DIA in 12 completions run to date in Nigeria.
Application of Memory Formalism and Fractional Derivative in Reservoir Simulation
Authors: Hashan Mahamudul , Zaman Tareq Uz , Jahan Labiba Nusrat , Elhaj Murtada , Imtiaz Syed , Hossain M. Enamul
Published: June 2018

Reservoir properties (e.g., porosity, permeability, surface tension, viscosity, fluid saturation, wettability, reservoir thickness, pressure, and temperature) are the function of time. Time variation of rock-fluid properties in a reservoir can be defined as memory concept in the field of petroleum engineering. Introducing memory formalism in reservoir simulation allows to account the time-varying nature of rock-fluid properties and enables reservoir simulator to provide more accurate reservoir flow forecast. The key purpose of this paper is to summarize the details for developing a memory formalism-based reservoir simulator. Within the context of the study, the key concept of memory formalism and fractional calculus are precisely explained. A complete roadmap in preparing a memory formalism-based reservoir simulator is shown with example and application.
A Comparative Analysis of Two Methods of Wax Treatment for a Waxy Oil Well in Southwest Trinidad
Authors: Persad Niran , Hosein Raffie , Jupiter Andrew
Published: June 2018

During oil production, when crude oil flows into a wellbore, pressure and temperature are reduced. The micelle structure of the crude oil is destabilized, allowing paraffin (wax) and/or asphaltene molecules to precipitate into the oil, increasing oil viscosity and allowing deposition in the well tubulars. This causes plugging of production and flow lines which decreases oil production. Wax deposition can be mitigated by the application of passive energy waves or a chemical solvent. Passive energy waves are generated by a tool containing a vibrating quartz and semi-precious metal core. This passive vibrational energy stabilizes the original micelle structure in oil and prevents wax deposition and viscosity changes. A chemical solvent is injected to dissolve and remove wax deposits.

In this study, both methods of wax treatment were applied on a waxy oil well in Trinidad, to determine which was more effective and economical. An average oil production rate of 14.4 barrels of oil per day (bopd) was attained from chemical solvent injection and an average oil production rate of 13.4 bopd from passive energy wave application, resulting in cumulative oil volumes of 374 barrels and 349 barrels respectively. Oil inflow into the wellbore, or Productivity Index, increased significantly from pre-treatment conditions by factors of 10.4 with chemical solvent injection and 8.8 with passive energy wave application. From an analysis using profit per barrel of oil (Netback) economics, the total workover cost for passive energy application, including tool rental and installation costs, paid out in 58 days at an average production rate of 13.4 bopd. The total workover cost for chemical solvent injection, including chemical and injection equipment costs, paid out in 12 days at an average production rate of 14.4 bopd.

Decline curve analysis showed that the historical production from the well followed an exponential decline model. This model was applied to production outputs resulting from both treatments and the analysis showed that the producing life of the well was altered by 19% with passive energy wave application and by 20% with chemical solvent injection. From oil sample testing, passive energy wave application caused an increase in oil API gravity from 22.5 to 28.8 °API and a decrease in oil viscosity from 439.1 to 23.7 centiPoise (cP). Production outputs and economics showed that chemical solvent injection was the more feasible wax treatment option for the waxy well studied. However, passive energy wave application was able to positively alter crude oil properties and showed notable success in preventing wax formation in this well.