bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation of Fracture Growth in Laminated Sandstone and Carbonate Rock Samples under Brazilian Testing Conditions Using Digital Image Correlation Technique
Authors: Nath Fatick , Salvati Peter E , Mokhtari Mehdi , Seibi Abdennour , Hayatdavoudi Asadollah 
Published: September 2017

Abstract
Strain is a critical parameter in the calculation of elastic rock properties, yet its conventional methods for strain measurement has several deficinies. In this paper, we analyze the application of optical methods with Digital Image Correlation (DIC) technique to provide detailed information regarding fracture patterns and strain development with time under Brazilian testing condition. The effect of porosity, rock types, lamination, and saturation on tensile strength will be also discussed.
To examine the effect of rock type, 60 samples of sandstone (Parker, Nugget and Berea) and carbonate formations (Winterset limestone, Silurian dolomite, Edward Brown and Austin Chalk) were testedunder dry and saturated conditions and with regard to lamination angle in laminated samples. A Vic-snap photogrammetry system was employed to monitor the samples in non-contact manner while conducting indirect tensile experiment. DIC is based on the photogrammetry system, which helps to visualize and examine rock fracture pattern from the recorded images of the rock before and after deformation by assessing the strain development in samples.
The experimental results show that - (1) average tensile strength declines while increasing porosity for homogeneous, laminated, and heterogeneous rock specimens. (2) lower tensile strengths are observed in carbonate rock samples compared to the sandstones except Silurian dolomite; (3) saturation reduces the rock strengths, for isotropic samples, highest 28% decline in strength (Berea sandstone) observed; whereas, a larger decrease (65%) was observed in fully heterogeneous Edwards Brown carbonate samples; (4) increase of lamination angle (from 0° to 90°) impacts the tensile strength, average tensile strength was observed for Parker and Nugget sandstone greater in perpendicular to the lamination (9 = 90°) direction compare to that of parallel (9 = 0°); (5) fracture patterns examined for homogeneous rocks are almost centrally propagated and relatively linear; whereas, three different fracture patterns (central fracture, layer activation and non-central or mixed mode) investigated for laminated and heterogeneous samples; (6) Finally, DIC results illustrated the fracture initiation and propagation with consistent strain mapping. The homogeneous samples produced a uniform fracture strain until the diametrical split where for the laminated samples were influenced by planes of weakness, and fully heterogeneous anisotropic rocks produced winding and erratic fractures.
Marcellus Shale Toe-up Laterals: Hydraulics and Well Control Implications
Authors: Elshehabi Tawfik , Bilgesu Ilkin 
Published: September 2017

Abstract
Unconventional shale resources are drilled horizontally following the geologic bed dip upward or downward and completed with multi-stage fracturing to maximize reservoir contact. A recent study in Oklahoma claimed that toe-up (inclined upward) laterals yield the highest production rate and estimated ultimate recovery. The objective of this study is to investigate drilling fluid hydraulics and well control operations in toe-up laterals and compare the results to toe-down laterals.
This study uses a multiphase steady-state hydraulics and a dynamic well control simulator. A hydraulics model was developed and verified with a data from a recently drilled Marcellus shale lateral in Monongalia County, WV in 2015. Static and dynamic pressure profiles were examined at drilling flow rate and at slow pump rate. Further, this research studies gas kick behavior and well control practices for kicks experienced at shallow, middle, and deep zones in the lateral section. Additionally, it considers the impact of operational parameters and influx characteristics on wellbore integrity.
The results of this study showed that the developed hydraulics model successfully predicted the pump pressure with an accuracy of 0.97. Larger kick sizes result in higher pit gain, gas flow rate, choke, and casing shoe pressures in toe-down laterals. In contrast, in toe-up laterals, the higher the kick size, the longer the circulation times with an insignificant impact on the choke and shoe pressures. In toe-up laterals, gas bubbles migrated towards the toe and accumulated in high side pockets. Likewise, choke experienced less pressure, volume, and gas discharge rate for extended periods of time in toe-up laterals. Therefore, higher circulation rates and longer circulation times were essential to flush out the dispersed and trapped gas bubbles. The closer the kick location to the vertical section of the well, the shorter the circulation time needed. However, kicks experienced at the heel resulted in higher pit gain, gas discharge rate, choke pressure, and consequently high casing shoe pressure.
Identifying the consequences of drilling toe-up laterals on hydraulics and well control is crucial for drilling operations. This improves rig and personnel safety and reduces the blowout associated risks. Accordingly, it is critical to verify the well integrity by monitoring surface choke, casing shoe, and constant bottomhole pressures throughout the entire well control operations.
Analysis of Compositions of Flowback Water from Marcellus Shale Wells by Utilizing Data Mining Techniques
Authors: Pan Yuewei , Yilin Wang John 
Published: September 2017

Abstract
Volume and salt concentrations in Marcellus flowback water depend on geology, drilling and completions, stimulation and flowback operations. Recent studies include evaluations of geochemical origins based on the compostition concentrations, flowback sampling analysis and numerical studies. However, an in-depth understanding of chemical compositions as well as the changes of compositions is still needed.
In this paper, we will first review the literature related to flowback water in Marcellus shale gas wells to fully understand the chemistry, geochemistry, and physics governing a fracture treatment, shut-in, and flowback. We will then gather all public and in-house flowback data, named as 3-week or 3-month flowback in this work, to build a data set of flowback water compositions. After data screening, we will then analyze this composition database using four different methods: geographical, changes over time, linear regression, clustering and multi-variable analysis. New understandings such as the magnitude and prevailing trends of concentrations for target constituents as well as the correlations among flowback compositions, the differentiation between early and late time flowback water were obtained and explained on the basis of geochemistry and physics. Guidelines for a comprehensive sampling protocol will be provided based on our analysis.
A Quantitative and Visual Experimental Study: Effect of Fracture Roughness on Proppant Transport in a Vertical Fracture
Authors: Huang Hai , Babadagli Tayfun , Li Huazhou Andy 
Published: September 2017

Abstract
The roughness of fractures may play an important role in affecting the migration and placement of proppants during hydraulic fracturing operations. Previous studies focused on investigating the proppant transport in smooth vertical fractures, which did not consider the effect of the fracture-surface roughness. We examine the migration of proppants in rough and vertical fractures and then quantitatively reveal the effect of roughness on the instantaneous proppant transport and final proppant placement. Two types of rock samples (marble and granite) are fractured with the Brazilian test and molded to manufacture 20 × 20 × 5 cm transparent replicas. The surface roughness of these rock samples was first characterized by fractal dimensions. Then, the dyed fracturing fluid with a given proppant loading was injected into the rough vertical fracture. In each test, the inlet pressures were continuously monitored in order to obtain the differential pressure across the fracture model while the proppants were being transported in the fracture. The process was videotaped to real-time track the proppant distribution in the rough fracture.
The proppant-transport behavior in the rough and vertical fracture was observed to be totally different from that in the smooth fracture. The major experimental findings include the following: 1) The proppant in a rough vertical fracture does not progress as a regular sand bank that commonly occurs in the smooth fracture, but rather an irregular-shape sand clusters with fractal characteristics; 2) In the rough and vertical fracture, the phenomenon of proppant bridging is visually observed, and such phenomenon is more likely to occur in the location with a larger roughness height. This implies rough fracture could promote a wider spreading of the proppant in the fracture compared to smooth fractures, and; 3) The existence of roughness enhances the vertical displacement of fluid containing proppants. These effects are also favorable for obtaining a better filling of the proppants in the fracture. Our experimental study reveals the mechanisms of proppant transport and distribution in real vertical fractures under the influence of roughness effect.
US Class II Underground Injection Wells: Injection and Seismicity Operational Risk Factors
Authors: Capper L. H. , Lee M. C. 
Published: September 2017

Abstract
Management of produced water from conventional plays and shale and tight oil and gas plays is driving subtle yet potentially consequential changes in certain regions and Underground Injection Control (UIC) formations.
UIC operation topics of interest include induced seismicity (from UIC injection, extraction, or unknown/anomolous activity), formation pressurization from years of UIC injection, and reallocation of produced water from originating "tight" producing formations to more receptive conventional, depleted, or waterflooded formations, resulting in formation pressure changes. Early signs of diminished formation health or threats to operations continuity can include: Barely felt (low magnitude) induced and anomolous earthsquakes - which nonetheless are a cause of significant concern to the public – and by extension, landowners, stakeholders, and regulators.Reduced formation injectivity – suggesting that injection rates should be "dialed back", or that injection pump pressures be increased, or that water be transported further to more receptive injection formations.
If encountered, stresses can contribute to cost overruns, impairment to operations schedules, additional oversite to assure regulatory compliance, reduced public goodwill, and potentially, impairment of industry’s social license to operate.
Through analysis of publicly available UIC operations data and well completion data, we evaluate methods which might help to qualitatively assess UIC issues with macro, regional, local and subsurface formation perspectives. The methods discussed may provide operators with a consistent simple methodology to qualitatively identify those assets and UIC formations with higher potential relative risk which may warrant more detailed exploration and possible risk mitigation.
Analysis and Design Method for Particulate Diversion in Carbonate Acidizing
Authors: Safari Reza , Shahri Mojtaba P. , Smith Clayton , Fragachan Francisco 
Published: September 2017

Abstract
In this paper, an integrated analysis and design method is presented to understand and quantify the effect of particle jamming near the entrance of perforation/wormhole tunnel. An advanced wellbore-scale three dimensional numerical studies with a coupled computational fluid dynamics (CFD) and discrete element model (DEM) were performed to simulate different mechanisms involved in particulate diversion. The results of wellbore-scale simulation were translated into an engineering particulate diversion model, based on the proven diversion mechanisms from laboratory and simulation. The model is incorporated into an integrated carbonate acidizing simulator.
Generally particulate diversion is not used in carbonate acidizing because of the formation of the wormholes and potential difficulty in removing particles from the induced wormholes or perforation tunnel. The new degradable particulate system addresses the issue and presents an efficient approach to divert acid in carbonate stimulation. Detailed physics based simulation demonstrate that the induced wormholes or perforation would plug thru two distinct mechanisms: (1) temporarily seal the entrance of small scale wormholes or perforation with a combination of small and large particles, and/or (2) large particles bridge along tapered path of wormhole/perforation and forms a temporary filter cake on the mouth of opening. Either of these diversion mechanisms will decrease the injectivity locally and promote fluid diversion from inside of well into other normally under-stimulated locations.
The integrated simulator is used to optimize acid stimulation of a vertical wellbore and explain the impact of operational parameters and subsurface conditions on the stimulation efficiency. The model results showed that most optimized bullheaded treatment can be significantly improved by utilizing the particulate diversion system. It is shown that that the developed skin from jammed particulate provided considerable diversion. The results also demonstrated the relation between treatment pressure, the quality of diversion, and subsurface conditions (e.g. permeability, porosity, reservoir pressure and temperature).
Characterizing Foam-Based Frac Fluid Using Carreau Rheological Model to Investigate the Fracture Propagation and Proppant Transport in Eagle Ford Shale Formation
Authors: Nath Fatick , Xiao Chongwei 
Published: September 2017

Abstract
In-situ stresses and heterogeneity of the formation rock are the dominant factors that influence hydraulic fracturing process. The rheology of frac fluid also significantly affects hydraulic fracturing treatment regarding fracture propagation, proppant transport, formation property alteration, and flow back process. Non-Newtonian CO2 foams stabilized by nanoparticles has been recently studied as a promising frac fluid, which is advanced in less water contents, proppant placement, fast clean, and maintaining conductive channels. For the application of the new frac fluid for unconventional reservoir development, it is critical to investigate fracture propagation and proppant transport using CO2 foams.
This study simulated hydraulic fracturing and proppant transport by viscous gas foams in a horizontal well perforated in Eagle Ford Shale formation of Zavala County, TX. A 3D numerical model was setup with heterogeneous reservoir properties using a commercial fracturing simulator - GOHFER. To represent formation heterogeneity, the rock mechanical properties were derived from well logs including Gamma Ray, Resistivity, Neutron Porosity, and Density Porosity logs, characterized by Young's modulus (3 × 106 ~ 6 × 106 psi), Biot constant (0.6 ~ 0.8), and Poisson's ratio (0.2 ~ 0.4). The flow behavior of CO2 foams stabilized by nanoparticles was characterized by Carreau rhelogy model based on the experimental data. During the pumping schedule for multistage fracturing process, the effects of variable injection rate (20 ~ 40 BPM), CO2 foams quality (50 ~ 80 %), incremental proppant distribution (0 ~ 5 PPA), and fluid leakoff were investigated.
The results showed that a laterally un-even shape of fracture propagation profile was developed during multi-stage CO2 fracturing, which represents the reservoir heterogeneity with varying in-situ stress and poroelastic properties. The results also indicated that the rheology of frac fluid significantly influences the fractures propagation. As the viscosity of CO2 foams increases with variation of foam quality from 50% - 80%, fracture width increases but fracture length decreases. The fluid loss during fracturing was quantified by pressure dependent leakoff approach. For different CO2 foams quality (50% - 80%), fluid leakoff rate decreases with increasing the CO2 foam quality.
This study provides a pioneering insight and improved fracture treatments design by non-Newtonian frac fluid - CO2 foams application with increased fracture conductivity and efficiency, which is vital for hydrocarbon exploitation from unconventional reservoirs.
Effect of Dilute Acid on Hydraulic Fracturing of Carbonate Rich Shales – Modeling Study
Authors: Teklu T. , Amini K. , Park D. , Jung H. , Abass H. H. 
Published: September 2017

Abstract
In Teklu et al. (2017a, and 2017b) matrix and fracture permeability of carbonate rich and clay rich shale cores were measured before and after exposing the core samples to spontaneous dilute acid imbibition. In this study, effect of brine and dilute acid imbibition on long term production of shale gas reservoir is investigated using numerical modeling approach.
Experimental observations show that: (1) matrix permeability of clay rich shale samples are usually impaired / damaged by dilute HCl imbibition. This impairment is due to both the clay swelling and related issue of brine (within the dilute HCl solution) and rock-acid reaction. (2) Matrix permeability of calcite rich shales improved with dilute acid imbibition. (3) Effective fracture permeability of un-propped (natural fracture) calcite rich and clay rich shales are reduced by dilute acid imbibition, this is because of "rock softening" and "etching/smoothing" of fracture roughness on the "fracture faces". (4) Propped permeability of clay and carbonate rich shales decrease with brine imbibition, and permeability further decreased after dilute acid imbibition. The further decrease in permeability and porosity after acid imbibition is caused by three phenomena: (a) rock weakening by rock-acid reaction, (b) further proppant embedment during repeated testes vs. stress, and (c) scale precipitation. These observations are similar to results reported in Teklu et al. (2017a and 2017b).
Modeling results show that: (1) For carbonate rich shale reservoirs, despite dilute acid injection/imbibition/fracturing can cause considerable damage to propped fractures and natural fractures (mainly due to rock softening/weakening, fracture roughness damage, and proppant embedment), it can still lead to considerable production improvement This is mainly caused by the matrix permeability improvement which leads to improvement in stimulated reservoir volume. (2) For clay rich shale reservoirs, both brine (slickwater) and dilute acid imbibition/injection/fracturing reduces hydrocarbon production, due to damages caused in to propped fractures, natural fractures, and matrix. Therefore, dilute acid injection or imbibition is recommended pre, post, or during hydraulic fracturing of carbonate rich shale reservoirs (but not for clay rich shale reservoirs) Moreover, slickwater fracturing in clay rich shale reservoirs can create considerable formation damage and decrease in hydrocarbon production, hence, dry gas (such as N2, CO2, LNG, etc.) might be an alternative solution hydraulic fracturing of in clay rich shale reservoirs.
Probabilistic linkage of national immunisation and state-based health records for a cohort of 1.9 million births to evaluate Australia’s childhood immunisation program
Authors: Gidding Heather F , McCallum Lisa , Fathima Parveen , Snelling Thomas , Liu Bette , De Klerk Nicholas , Blyth Christopher C , Sheppeard Vicky , Andrews Ross M , Jorm Louisa , McIntyre Peter B , Moore Hannah C 
Published: September 2017

IntroductionSeveral countries have developed national immunisation registers, but only the Nordic countrieshave linked their registers to other health data in order to comprehensively evaluate the ‘real world’effectiveness of vaccines. Nordic countries can link datasets deterministically using the nationalperson identifier, but most countries, including Australia, don’t have such an identifier to enablethis type of linkage.
ObjectivesTo describe the process for assembling a linked study cohort that will enable the conduct ofpopulation-based studies related to immunisation and immunisation policy.
MethodsNational death and immunisation databases along with state health data (notifications of vaccinepreventable diseases, perinatal data, hospital admissions and emergency department presentations)up until December 2013 were probabilistically linked (using demographic details) for children bornbetween 1996 and 2012 in two states: Western Australia and New South Wales (42% of Australia’spopulation, combined).
ResultsAfter exclusions there were 1.95 million children in the study cohort (live born children withboth a birth and perinatal record which represents 97.5% of all live births in the state perinataldata collections - our source population) and 18.0 million person years of follow up (mean: 9.2years per child). The characteristics of children in the cohort were generally similar to those onlyincluded in state perinatal databases and outcome measures were in keeping with expected figuresfrom unlinked data sources. However, the lack of a dynamic national population register meantimmigrants could not be included.
ConclusionsWe have been able to develop a similarly comprehensive system to the Nordic countries based onprobabilistic linkage methods. Our experience should provide encouragement to other countrieswith national immunisation registers looking to establish similar systems.
Nghiên cứu ảnh hưởng của các nồng độ dung dịch dinh dưỡng NQ2 đến sinh trưởng và năng suất xà lách xoăn trồng phương pháp thủy canh bấc đèn tại Thừa Thiên Huế
Authors: Khánh Lê Thị , Quy Nguyễn Văn 
Published: September 2017

Thí nghiệm thực hiện vụ Xuân 2012 Tại Thừa Thiện Huế, nhằm chọn được một nồng độ dung dịch dinh dưỡng NQ2 thích hợp nhất với xà lách xoăn, cây sinh trưởng tốt, thu năng suất cao và hiệu quả kinh tế lớn nhất. Thí nghiệm gồm 6 công thức, cồng thức I -IV ứng với các nồng độ từ 400-1200 ppm và VI (đối chứng): trồng ngoài đất, nhắc lại 3 lần, mỗi công thức TN trồng 30 hôp xốp, mỗi hộp xốp có kích thước dài x rộng x cao = (50 x 40 x 20 )cm, trồng 12 cây với mật độ 60 cây/m2. Áp dụng kỹ thuật hệ thống thủy canh bấc đèn. Kết quả cho thấy: Tất cả các nồng độ dung dịch dinh dưỡng NQ2 đều có ảnh hưởng tốt đến sinh trưởng, năng suất và hiệu quả kinh tế của xà lách xoăn vụ Xuân, trong đó Công thức V có nồng độ dung dịch dinh dưỡng 1000 ppm là tốt nhất
NGHIÊN CỨU SỰ TÍCH LŨY NITƠ VÀ PHỐT PHO TRONG AO NUÔI TÔM THẺ CHÂN TRẮNG Litopenaeus vannamei (Boone, 1931) TẠI TỈNH THỪA THIÊN HUẾ
Authors: Trâm Nguyễn Duy Quỳnh , Dũng Ngô Tiến , An Lê Thị Thu , Ngọc Trần Nguyên , Minh Nguyễn Tử , Sơn Nguyễn Khoa Huy 
Published: September 2017

Nghiên cứu này nhằm đánh giá sự tích lũy nitơ và phốt pho trong ao nuôi tôm thẻ chân trắng tại Tỉnh Thừa Thiên Huế. Nghiên cứu đã triển khai trên 6 ao lót bạt, nuôi tôm thẻ chân trắng với mật độ 150 con m-2. Kết quả nghiên cứu cho thấy rằng một lượng lớn nitơ và phốt pho được cung cấp vào ao nuôi chủ yếu là từ thức ăn lần lượt chiếm đến 92 % và 94,5 %, còn lại từ con giống và nước cấp chỉ chiếm tỷ lệ thấp, đối với nitơ là 8%, trong đó 7,998 % từ nguồn nước cấp và con giống là 0,002 %, đối với phốt pho là 5,5 %, trong đó từ con giống là 0,001%, từ nước cấp là 5,499 %. Khả năng chuyển đổi và tích lũy nitơ và phốt pho của tôm nuôi trong mô hình này lần lượt là 30 % và 9 %. Lượng lớn nitơ tôm không hấp thụ được thải ra ngoài môi trường chiếm 70 %, trong đó nước thải chiếm 54 % và trong bùn chiếm 11 %, nitơ thất thoát là 5 %. Phốt pho thải ra ngoài môi trường nước và bùn đáy lần lượt là 20 % và 40 %, lượng phốt pho thất thoát không xác định được chiếm tỷ lệ 31 % của tổng Phốt pho đầu vào. Trung bình để sản xuất ra 1 tấn tôm thương phẩm sẽ thải ra môi trường là 88 kg nitơ và 19 kg phốt pho. Từ khóa: nitơ, phốtpho, tích lũy, tôm thẻ chân trắng.