bluuebunny/crossref_metadata_2025 huggingface dataset:
A GEOLOGIA ENTRE MACAÚBAS E CANATIBA (BAHIA) E A EVOLUÇÃO DO SUPERGRUPO ESPINHAÇO NO BRASIL ORIENTAL
Authors: Caxito Fabrício de Andrade , Dos Santos Yan Lucas de O. Pereira , Uhlein Alexandre , Pedreira Augusto José , Faulstich Fabiano Richard L.
Published: January 2016

The Espinhaço Supergroup cropping out between the cities of Macaúbas and Canatiba, in the northernEspinhaço range, Bahia, is composed by the Pajeú Group (metarhythmites and intermediate to acidmetavolcanics), the Bom Retiro Formation (mature quartzites with metric to decametric cross-bedding), theSão Marcos Group (quartzites with wavy stratification and wave-related cross-bedding, intercalated with micaschists)and the Sítio Novo Group (cross-bedded, conglomeratic and massive quartzites, metarhythmites andmetapelites). The bedrock (gneisses and schists) is tectonically emplaced over the Espinhaço Supergroup inthe eastern portion of the area, and the Espinhaço Supergroup is unconformably covered by the Santo OnofreGroup (graphite-phyllites and metarhythmites) in the western portion of the area. This whole stratigraphicpackage is inverted, allowing, together with relations between bedding and schistosity, to define a largeinverted limb of an assymmetric fold with axis NNW-SSE.In the Veredas Formation, intermediate portion of the Sítio Novo Group, occurs a bed of approximately10 m of deep blue dumortierite-quartzites, used as ornamental rocks. Samples of these rocks have beenanalysed using optic, cathodoluminescence and electronic microscopic techniques, revealing its mineralogicand micromorphologic features.Comparing the stratigraphic and sedimentologic features of the studied area with other outcropping areas ofthe Espinhaço Supergroup, it can be concluded that it has evolved through three sedimentary megacycles,represented on each of the portions of the Espinhaço Range and Diamantina Plateau in the eastern regionof Brazil. The first megacycle involves syn-rift sedimentation, starting at about 1,75 Ga (Statherian Period).The second megacycle involves fundamentally eolian sedimentation. The third megacycle involves mainlyshallow marine to transitional sedimentation, with important tectonic reativation in the northern sector ofthe basin. All megacycles evolded in intracratonic environment..
A TECTÔNICA EXTENSIONAL PALEOPROTEROZÓICA NA BORDA SUDESTE DO CRATON SÃO FRANCISCO (SE, BRASIL): GEOQUÍMICA E PETROLOGIA DAS METAÍGNEAS.
Authors: Dussin Tania Mara
Published: January 2016

This work presents an assembly of geological, geochemical and petrological data concerning differentepisodes of magmatism related to Espinhaço Basin evolution in the central part of Minas Gerais State, witha goal to understand aspects of paleoproterozoic crust and tensional tectonic. Metamagmatic rocks arerepresented by alkaline flows, tholeitic gabbros and basalts and subalkaline granites and rhyolites. Geologicaland geochemical data indicate magma genesis in an anorogenic context at about 1.7 Ga. Taken together, allthese magmatic episodes reflect great rigidity of the Paleoproterozoic continental crust and indicate thatmagma genesis process occurred whenever there was a resurgence of crustal extension, fracturing andrifting, deep melting and the provision of conduits for the mantle heat and mantle magmas to rise into andmelt the crust.
Colaboradores deste número
Authors: Editor O
Published: January 2016

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A correspondência Jakobson-Mattoso Câmara (1945−1968)
Authors: Altman Cristina
Published: January 2016

RESUMO:

No texto estão editadas 23 das cartas que compõem a correspondência, até então inédita, entre dois grandes autores da Linguística do século XX, Joaquim Mattoso Câmara (1904−1970) e Roman Jakobson (1896−1982), depositadas no acervo de Mattoso Câmara, na Biblioteca da Universidade Católica de Petrópolis, Rio de Janeiro, e no acervo de Roman Jakobson, confiado ao MIT Libraries-Archives and Special Collections, em Cambridge, Massachussetts.

PALAVRAS-CHAVE: Mattoso Câmara, Jakobson, estruturalismo, fonêmica
O tratamento dos pronomes pessoais átonos na gramaticografia do português (séculos XVI-XVII)
Authors: Ponce de León Romeo Rogelio
Published: January 2016

RESUMO:

No artigo é analisada, nas obras metagramaticais do português dos séculos XVI e XVII, a descrição dos pronomes pessoais átonos. Partindo de trabalhos que, entre outros aspetos, abordam com algum pormenor o pronome na tradição gramatical do português, é estudado o grau de gramatização das formas em estudo, bem como, no caso de elas aparecerem registadas, o discurso gramatical acerca delas, tanto no que se refere à descrição como à prescrição, e os paradigmas em que se integram.

PALAVRAS-CHAVE:

Pronomes pessoais átonos – Gramaticografia do português – Séculos XVI e XVII
Probiotic preparation reduces faecal water genotoxicity and cytotoxicity in chickens fed ochratoxin A contaminated feed (in vivo study).
Authors: Śliżewska Katarzyna , Nowak Adriana , Smulikowska Stefania
Published: January 2016

The aim of the present study was to assess the genotoxicity and cytotoxicity of the faecal water of chickens fed ochratoxin A (OTA) contaminated feed with and without probiotic preparation. The study was performed on 20 healthy female Ross broiler chickens divided into 4 groups: control chickens - fed with non-supplemented feed; PP chickens - fed feed supplemented with the probiotic preparation; OTA chickens - fed feed contaminated with 1 mg per kg of OTA; OTA + PP chickens - fed feed contaminated with 1 mg per kg of OTA and supplemented with the probiotic preparation. Faecal water samples were collected on the 35(th) day of life of chickens from each group. Genotoxicity was measured using the comet assay, and cytotoxicity by means of MTT tests. Mean DNA damage, measured as the percentage of DNA in the tails of the comets, was 8.50 ± 1.10 for chickens fed OTA at 1 mg/kg and 6.41 ± 0.67 in the controls. The supplementation of feed with the probiotic preparation decreased the extent of DNA damage to 4.74 ± 0.78. In the control group of chickens the average cytotoxicity was 38.5 ± 0.5 (in MTT), while in the probiotic preparation group (PP group) it was 31.8 ± 0.7 (in MTT). After supplementation of the feed with the probiotic preparation, the genotoxicity and cytotoxicity were decreased in a statistically significant manner.
KEPERCAYAAN MASYARAKAT BANJAR TERHADAP BULAN SAFAR: Sebuah Tinjauan Psikologis
Authors: Mubarak Siti Faridah Dan
Published: January 2016

Bulan Safar adalah salah satu bulan dalam Kalender Hijriyah, Bulan Safar sebenarnya bulan biasa. Tidak terdapat keistemewaan atau kesialan di bulan itu. Kepercayaan akan adanya kesialan di bulan Safar sudah ada pada bangsa Arab sejak zaman Jahiliyah. Faktor yang mendasari sebagian masyarakat Banjar mempercayai dan melaksanakan amaliah tertentu di bulan Safar berdasarkan keterangan dari kitab-kitab ulama terdahulu yang disampaikan oleh para tokoh agama sehingga terjadi proses sugesti dan peniruan perilaku (modelling). Tradisi tersebut diwariskan turun temurun hingga sekarang. Motivasi dan tujuannya adalah untuk memperoleh keselamatan dan menhindari kesialan.
RELASI DAYAK-BANJAR DALAM TUTUR MASYARAKAT DAYAK MERATUS
Authors: Rafiq Ahmad
Published: January 2016

Etnis Dayak dan Banjar pada awalnya berasal dari rumpun etnik yang sama. Namun kemudian diidentifikasi secara berbeda tidak hanya melalui etnisitas, tetapi juga agama mereka. Dayak identik dengan Kaharingan sebagai agama asli mereka, sementara Banjar identik dengan Islam sebagai agama yang baru mulai dianut sejak didirikannya Kesultanan Islam Banjar oleh Pangeran Samudera. Semenjak itu, perbedaan identitas ini direspon oleh orang Dayak melalui mitos atau folklore. Mitos-mitos ini, berdasarkan riset lapangan yang telah dilakukan oleh penulis artikel ini, dipahami sebagai seperangkat simbol yang mengungkapkan tipologi relasi orang Dayak dengan Banjar. Paling tidak, ada empat tipologi relasi yang terungkap di sini, yakni: relasi geneologis, analogis, kooperatif, dan historis. Berbagai tipologi relasi inilah juga yang akhirnya menjadi dasar munculnya bentuk-bentuk sinkritisisme budaya di antara keduanya, Dayak-Banjar.
UNDANG-UNDANG SULTAN ADAM 1835 DALAM PERSPEKTIF SEJARAH HUKUM
Authors: Abdurrahman Abdurrahman
Published: January 2016

Undang-undang Sultan Adam sebagai perangkat hukum peninggalan masa lalu kurang mendapatkan perhatian baik dari kalangan para ahli hukum maupun dari sejarawan, bahkan sampai sekarang ini teks peraturan itu belum pernah ditulis dalam bahasa Indonesia karena sampai saat ini dokumen itu masih tertulis dalam bahasa Melayu/Banjar disertai terjemahannya dalam bahasa Belanda. Karena itu wajar apabila dokumen hukum itu tidak tersebar secara meluas dikalangan para ilmuan. Di sampimg itu dokumen hukum itu juga penting sebagai informasi bagi generasi mendatang tentang keberhasilan yang pernah dicapai oleh nenek moyang mereka dimasa lampau dalam menetapkan hukum di dalam masyarakatnya.
PETA GERAKAN SYI�AH DI KALIMANTAN SELATAN
Authors: . Humaidy
Published: January 2016

This article traces back the entry of the Shia in South Kalimantan through the inclusion of Islamic Wujudiyah (panentheism) Sufism which was first spread in the kingdom of Banjar. This is due to the similarity between Wujudiyah Sufism with the concept of Irfan in Shi'a. However, the influence of Shia in South Kalimantan suffered a setback at the era of Syekh Muhammad al-Banjari Arsyad (1710-1812 AD). According to Habib Ali, Shia began to revive in South Kalimantan after the Iranian revolution in 1979. Jafari school of thought (madhabs) is the growing Shiah in South Kalimantan. The Development of Shia in South kalimantan faces many challenges since Muslims in South Kalimantan have a strong belief in Sunni.
Assessing productivity to address safety concerns for information technology and promoting global standardization within aviation practices
Authors: Brown Willie Lee , Gilchrist Willie J.
Published: January 2016

Comparing these concepts with the usage of productivity assessment current design standards in implementing technological systems create concerns in safety performances [5]. The technology developmental risk was a concern in the Wright Brother era and the approach in implementing best solution practices based on simulating and testing standards to meet the goals in today’s operation is still an issue [4]. Effective modeling in promoting environmental changes for operational practices can present a risk concern in the developmental approach if productivity is not assessed [1]. Steps are needed to be taken to improve the environmental factors in the business efforts of promoting alternative energy; nonetheless, the long-term effects of not prioritizing the development standards on the global level may cause risk concerns in assessing aviation practice [1]. Realizing the sensitivity of the system development and the tradeoffs in implementing effective practices can also create awareness in the long-term efforts of environmental factors and its impact on operational cost improvements [10]. The ethical standards for human factors to improve the quality of people lives in addressing the challenges faced may be a concern going into the 21st century [7]. The tradeoffs of prioritizing can present both pros and cons; however, developmental practices are risky without modeling long-term impact and exploring different applications in adopting business practices [6]. Flexibility is an importance aspect in evaluating the productivity of long-term practices while using modern technology [6]. The productivity assessment impact in future implications and it influences to integrate traditional technology within the modern environment. 

 

Keywords: IT, aviation practices, promoting
Message from editor
Authors: Karahoca Adem
Published: January 2016

Message from editor
Advantages of using webquests in Efl Classes in A Technical University
Authors: Kuimova Marina Valeryevna , Golousenko Maksim Anatolyevich , Nikiforov Denis Sergeevich , Shcherbakov Vladislav Vladimirovich
Published: January 2016

The main purpose of foreign language teaching is to learn to communicate and overcome the language barrier. The article studies the theoretical background of WebQuest as a valuable tool and proves that it helps learners to acquire linguistic and extra-linguistic knowledge. WebQuests ensure a context-based learning environment, help to broaden learners’ perspectives by widening ideas and concepts on different topics and acquiring creative, critical and problem-solving skills. The authors demonstrate positive outcomes of the work with WebQuest in foreign language classes at the Institute of Non-Destructive Testing, National Research Tomsk Polytechnic University. Keywords: creative skills, foreign language teaching, Internet resources, Internet technology, WebQuest
Examining the instructors computer self-efficacy perceptions
Authors: Semerci Ali , Keser Hafize
Published: January 2016

In this study, instructors’ computer self-efficacy perceptions are examined in terms of variables such as age, gender, academic status, teaching experience, computer literacy and computer skills. The study is a descriptive one in which relational scanning method has been utilized. The study has been carried out within the framework of the data obtained from 172 police instructors who work in 28 Police Vocational Schools of Higher Education across the country. The data were collected by using a survey and “The Computer Self-efficacy Perception Scale”. A significant difference has been found between the self-efficacy perceptions of the instructors and their computer skills and computer training that they received. In addition to this, it has been seen that there was not any significant difference between self-efficacy perceptions of instructors and age, gender, position status, teaching experience and computer literacy. This is the first study carried out for determining the self-efficacy perceptions of police instructors. The results should be considered during the police trainer development trainings.  Keywords: self-efficacy, self-efficacy perceptions, training, education, police education.
Antioxidant and antimitotic activities of sulfated polysaccharide from marine brown algae Padina tetrastromatica
Authors: Jose Geena Mariya , Radhakrishnan Anitha , Muraleedhara Kurup G
Published: January 2016

Antioxidants play a central role in the prevention of carcinogenesis. The most natural compounds exhibit their protective effects by eliciting antioxidant potential. Sulfated polysaccharide was isolated from the brown algae Padina tetrastromatica, then purified and evaluated for its composition and in vitro antioxidant and antimitotic activities. Both ethanolic sulfated polysaccharide (ESPS) and ethanolic sulfated polysaccharide-column purified (ESPS-CP) exhibited considerable amount of carbohydrates (11.2% and 17.6%), sulfate (11.4% and 7.4%), fucose (5.5% and 15.7%), uronic acid (4.7% and 11.8%), xylose (0.5% and 0.03%) and sulfated polysaccharide (2.4% and 12.7%) content. The FTIR analysis and phytochemical screening also confirmed the presence of sulfated polysaccharides. In the in vitro antioxidant activity determination using DPPH (1-1-diphenyl 2-picryl hydrazyl) radical scavenging activity, hydroxyl radical scavenging activity, superoxide anion scavenging activity, hydrogen peroxide scavenging activity, total antioxidant activity and reducing power, ESPS showed more activity than ESPS-CP. In the case of nitric oxide radical scavenging, ESPS-CP was found to be more effective. At a concentration of 2mg/ml, both samples were potent antioxidants with significant IC50 values. The antimitotic studies such as mitotic index in onion root tips and sprouting assay in green gram seeds also proved that both the extracts are able to prevent mitosis. The extrapolation of these results can find opportunities in therapeutic regiments of cancer.
Modeling Study of Acid Fracture Fluid System Performance
Authors: Aljawad M. S. , Zhu D. , Hill A. D.
Published: January 2016

Acid fracturing stimulation can be an effective means to improve well performance in carbonate formations. In general, a treatment consists of multiple stage injections alternating between acid and non-reacting fluid to better place acid, and therefore, to create sustainable conductivity for enhanced well productivity. Selecting appropriate fluid systems is critical in success of acid fracturing. To optimize acid fracturing design, an integrated approach is needed to model the fluid behavior inside of the fracture, the conductivity after fracturing, and the productivity of fractured wells.

The integrated approach includes an acid transport model and a fracture propagation model. Theoretical models were developed to obtain the conductivity distribution and acid penetration distance inside fractures. Continuity and momentum balance equations are solved in three-dimensional space for pressure and velocity profiles. Once the velocity profile is generated, the acid balance equation can be solved for the acid concentration profile. Obtaining a concentration profile helps in calculating the amount of rock etched through diffusion and convection. Conductivity distribution is calculated using a correlation where statistical parameters are used to account for fracture heterogeneity. Finally, a reservoir simulator is used to predict the production performance from acid fractured wells.

Straight, emulsified, and gelled acid systems are examined using the integrated approach to capture the effect of each on fracture conductivity and acid penetration distance. Optimizing these two parameters will improve the production performance significantly. Straight acid reacts aggressively with carbonate formations and leaks off significantly more near the entrance of the fracture when compared with the other two acid systems. The apparent viscosities of gelled or emulsified acids are substantially higher than that of straight acid, and the diffusion coefficients of these viscous fluids are substantially lower than that of straight acid. These properties result in deeper penetration down the fracture with gelled or emulsified acids, but also less fracture etching by acid near the well. The tradeoff between deeper penetration with viscosified acid systems versus more near well etching with less viscous systems means that the acid formulation can be optimized depending primarily on the formation permeability.

Production analysis of these three acid systems suggests that emulsified acid is better used in tight formations. Gelled acid, on the other hand, results in the highest production rate when used in relatively high to medium permeability formations. Straight acid is the preferred system only when short, highly conductive fractures are desired.
Impact of Ash Beds on Production in Eagle Ford Shale
Authors: Xu Jian , Fisher Kevin , Qiu Fangda , Malpani Raj , Ejofodomi Efe , Viswanathan Anup
Published: January 2016

The Eagle Ford shale contains both kaolinite- and smectite-rich altered ash beds that present challenges for completion and production. Considering the five Eagle Ford units (A–E), the ash beds occur in the B unit. The B unit is divided into five subunits; B1 and B2 are characterized by the highest total organic carbon (TOC) whereas B3–B5 have a higher frequency of ash beds. The impact of these ash beds is not yet fully understood, but acquired horizontal production log measurements indicate that the production performance of stages landed in the B3–B5 units, with high ash bed frequencies, are poor compared to other stages landed in a different unit. Some operators are vertically staggering laterals to effectively drain the reservoirs, partially due to the lack of vertical connection in the production phase. Thus, to increase the effectiveness of the completion strategy and ultimately the well performance, methods must be developed to quantify the impact of ash beds on production and to mitigate the negative impact. An integrated hydraulic fracture-reservoir modeling workflow was applied on an Eagle Ford shale lateral with part of the lateral crossing an ash bed in B3–B5 units. The subject well was completed with 15 stages. The simulation results demonstrate that the ash beds in B3–B5 units restrict part of the created hydraulic fracture height and create conductivity pinch points, thus reducing the effective fracture height connected to the wellbore. This, in turn, affects the potential well productivity. Based on the simulated results, the optimum lateral landing location is within the B1–B2 interval. The analysis also showed that targeting the hydrocarbons in these units requires a different completion strategy. Use of a crosslinked fluid carrying higher proppant concentrations will facilitate the creation of larger fracture widths to withstand the negative impact of the ash beds isolating a certain portion of the created fracture height.
Understanding the Applicability and Economic Viability of Refracturing Horizontal Wells in Unconventional Plays
Authors: Lindsay G. J. , White D. J. , Miller G. A. , Baihly J. D. , Sinosic B.
Published: January 2016

Oil prices have fallen to lows not seen in years. These low oil prices and sustained low gas prices have drastically reduced the number of new wells being drilled in US unconventional plays as oversupply from these plays has reached an all-time high in US storage levels. One alternative to drilling new wells is to hydraulically refracture older wells to enhance production and gain additional economic returns. With each successful refracturing operation, service companies are improving on methods to divert refracturing fluid and proppant without the use of mechanical diversion techniques. To ensure success and meet economic hurdles, refracturing requires thorough preparation, proper candidate selection, and effective diversion techniques.

The authors of this paper studied the economic potential and applicability of refracturing in six different unconventional plays across the US, including the Haynesville, Fayetteville, Barnett, Woodford, Eagle Ford, and Bakken plays. The expected rates of return for refracturing were compared to the economics of new wells to determine which alternative is a better use of capital spending and how the economics vary by play. Major challenges with refracturing horizontal laterals are highlighted, along with criteria for picking the best refracturing candidates to reduce risk and help meet economic hurdles.

We carefully searched through over 20,000 laterals completed since the second half of 2013 in the US and found more than 100 horizontal wells refractured by chemical diversion means based on public records. The production results of these wells were evaluated to identify the best basins for economic success. The Haynesville and Eagle Ford show the best rates of return, whereas other basins will require higher market prices, changes to current refracturing techniques, and/or identification of the best refracturing candidates to minimize the associated risks. The number of economic horizontal refracture candidates across the various basins will vary with fluctuations in oil and gas prices.
Strategies for Effective Stimulation of Multiple Perforation Clusters in Horizontal Wells
Authors: Manchanda Ripudaman , Bryant Eric C. , Bhardwaj Prateek , Sharma Mukul M.
Published: January 2016

Increasing the efficiency of completions in horizontal wells is an important concern in the oil and gas industry. To decrease the number of fracturing stages per well it is common practice to use multiple clusters per stage. This is done with the hope that most of the clusters in the stage will be effectively stimulated. Diagnostic evidence, however, suggests that in many cases only 1 or 2 clusters out of 4 or 5 clusters in a stage are effectively stimulated.

In this paper strategies to maximize the number of effectively stimulated perforation clusters are discussed. A fully 3-D poroelastic model that simulates the propagation of non-planar fractures in heterogeneous media is developed and used to model the propagation of multiple competing, fractures. A parametric study is first conducted to show how important fracture design variables such as limited entry perforations and cluster spacing; and formation parameters such as permeability, lateral and verical heterogeneity affect the growth of competing fractures. The effect of stress shadowing due to both mechanical and poroelastic effects is accounted for.

3-D numerical simulations have been performed to show the impact of some operational and reservoir parameters on simultaneous competitive fracture propagation. It was found that an increase in stage spacing decreases the stress interference between propagating fractures and increases the number of propagating fractures in a stage. It was also found that an increase in reservoir permeability can decrease the stress interference between propagating fractures because of poro-elastic stress changes. A modest (about 25%) variability in reservoir mechanical properties along the wellbore is shown to be enough to alter the number of fractures created in a hydraulic fracturing stage and mask the effects of stress shadowing. Inter-stage fracture simulations show post-shutin fracture extension induced by stress interference from adjacent propagating fractures. The impact of poro-elasticity is highlighted for infill well fracture design and preferential fracture propagation towards depleted regions is clearly observed in multi-well pad fracture simulations.

The results in this paper attempt to provide practitioners with a better understanding of multi-cluster fracturing dynamics. Based on these findings recommendations are made on how best to design fracture treatments that will not only lead to the successful placement of fluid and proppant in a single fracture, but in a set of fractures that are competing with each other for growth. The ability to successfully stimulate all perforation clusters is shown to be a function of key fracture design parameters.
First Application for a Sequenced Fracturing Technique to Divert Fractures in a Vertical Open Hole Completion: Case Study from Saudi Arabia
Authors: Bartko Kirk , Tineo Roberto , Aidagulov Gallyam , Al-Jalal Ziad , Boucher Andrew
Published: January 2016

A unique sequenced fracturing technique using formation notching and degradable diversion pills was applied for the first time in a vertical open hole completion to stimulate multiple pay intervals in a well in the "Q" sandstone formation of Saudi Arabia.

The challenge to divert fractures in a vertical open hole is made more difficult by the large fracture surface area in contact with the wellbore. A robust, efficient and repeatable two-step technique was implemented to provide the diversion and controlled breakdown of higher-stressed sections of the interval. The first step used a specialized jetting nozzle to create circular notches and weaken the formation at target depths. The second step involved the pumping of a small volume of a composite fluid of degradable non-damaging fiber and particles that bridge at the fracture face, to divert the remainder of the treatment to under-stimulated sections of the interval.

The target for this well was a shallower formation due to completion pressure limitations while fracturing. This left six pay intervals spread across the tight, heterogeneous sandstone layers of the Q formation, which was completed as a single 552-ft. vertical open hole section. Previous experience showed large stress variations in the layers with contained fractures, and fracturing all pay intervals required separate treatments for each interval. After notching the pay intervals to reduce breakdown pressures, the interval was fractured with three proppant ramps separated by two diversion pills in the span of 8 hours, improving efficiency by more than three times. Diversion was confirmed by: (1) pressure increases of 380 psi and 500 psi, respectively, when the pills landed on formation; (2) increasing trend of the instantaneous shut-in pressures (ISIP's) throughout the treatment, resulting in 1,270 psi of net pressure gain; and (3) comparison of post-diagnostic injection test temperature log data with post-fracturing neutron log data, showing where nonradioactive traceable proppant was placed, including into at least three pay intervals not broken down during the injection test. Post-treatment production expectations were met and confirmed with a well test.

This paper will present the design, execution, and evaluation methodology and challenges overcome to divert hydraulic fractures in long vertical open hole intervals using this two-step diversion process for sequenced fracturing. The ability to do this consistently and predictably can provide a practical, efficient, and cost-effective preferred solution that does not exist today for completing and fracturing similar zones that are traditionally bypassed, resulting in increased production and reserves.
Improving North Sea Fracturing and Stimulation Economics Through Increasing Innovation and Efficiency in Operations and Applications: Lessons Learned
Authors: Ishteiwy O. , Doghmi A. , Rylance M.
Published: January 2016

Completion and intervention costs across the North Sea are at an all-time high and continue to challenge development economics; this has been exacerbated recently by a deteriorating oil price making cost-effective completion and intervention operations even more challenging. Typically at times such as these, the industry turns to the fracturing and stimulation process to maximise the return from existing assets and new wellbores. While this method continues to be feasible, increasingly this can only be achieved through challenging existing conventions and applying increasingly innovative approaches to the principal aspects and assumptions applied to the operations themselves; namely the deployment and the effectiveness of such operations in the field.

As the cost of a fracturing and stimulation execution mounts, due to numerous factors, including the efficiency of the service itself, available/economic well intervention capability, provision of sufficient accommodation (somewhat surprisingly/unhelpfully) and an ability to flow-back and clean-up in an efficient and effective manner. This paper will provide examples and case histories, across a number of our North Sea operations, which challenge and optimise each of these areas and demonstrate a number of mechanisms and approaches that have successfully been applied in order to reduce overall costs.

Some of the examples include a case history of the use of a boat (stimulation vessel) to boat (intervention vessel) stimulation approach, in order to eliminate secondary rig costs and thereby maximise the economics. Consideration of the use of a rig-based stimulation capability vs. extensive boat operations, efficient and cost effective well recompletion approaches and a suite of incremental improvements born out of continued North American solution development and deployment, such as the use of expandable packers and ball-drop matrix stimulations. Increasing the effectiveness of fracturing and stimulation (and maximising the productivity of each and every individual wellbore) is an obvious approach to improving economics and can be achieved in any number of ways. Again this paper will present a suite of examples and case histories of where this has already been achieved, across a number of our North Sea operations.

The current ‘perfect storm’, of a low oil-price environment combined with high industry contractual costs, is forcing all operators to become increasingly innovative in their pursuit of economic resource development across the North Sea. This paper presents a number of examples of innovation and cost-saving approaches that have been employed in order to achieve such economic intervention and provide further insight into the additional development potential and opportunity that may exist across this varied asset base.
Hydraulic Fracture Height Estimation in an Unconventional Vertical Well in the Vaca Muerta Formation, Neuquen Basin, Argentina
Authors: Ortiz Alberto César , Hryb Damián Emmanuel , Martínez Joaquín Ramirez , Varela Raúl Alejandro
Published: January 2016

One of the major uncertainties in the analysis of unconventional well productivity is the estimation of the hydraulic fracture height generated during stimulation operations. This study was carried out in a well located in the Neuquen Basin, Argentina with main focus on the development of unconventional shale oil.

The strategy consisted in the application of two combined techniques based on different and independent physical principles for the estimation of the hydraulic fracture height. The initial technique consisted in the pumping of proppant which contains elements with great neutron absorption. Thereby, the presence of traced proppant is identified through the differences in the neutron absorption capacity before and after the stimulation at approximately 6 inches from the wellbore.

The second technique is based on the characterization of the anisotropy on the shear wave obtained by the dipolar sonic curve in two perpendicular directions. This acquisition should be carried out before and after the stimulation and it is sensitive in the area close to the wellbore. (Between 5 and 40 in)

Results from both techniques showed a reasonable good consistency in the results, thus allowing the validation of both methodologies.

The results also allowed defining intervals that act as barriers of the hydraulic fracture vertical growth. This permit us the optimization of the fracture design in other wells, thus minimizing the vertical overlapping of the fractures and maximizing the connectivity of the stimulated interval in the well. In addition, traced proppant was confirmed close to the wellbore in several intervals that together represent approximately 60% of the pay which represents a 170 m. To improve completion efficiency, this information can be used to place hydraulic fracture stages and define clusters geometry.

Finally, it could be determined that a set of factors allowed the control of the vertical growth of the hydraulic fracture with proppant in the proximity of the wellbore. The main control on hydraulic fracture height was the magnitude of the minimum horizontal stress. The presence of discontinuities in the rocks such as calcite veins volcanoclastic intervals and limestone beds may also play a role.

These new data provide confidence on the current geomechanical model helping to optimize the upcoming stimulation operations in the area.
Lessons Learned: Refracs from 1980 to Present
Authors: Grieser Bill , Calvin James , Dulin James
Published: January 2016

Refracturing in the US midcontinent is not a new method. In 1980, a refracturing program was begun in the shallow, low-pressure Brown Dolomite gas pay in the Texas panhandle. The results were mixed, but the overall outcome was economically beneficial. Currently, operators are refracturing horizontal shale wells, especially those completed from 2003 to 2010. However, results continue to be mixed and unpredictable. This paper presents lessons learned during refracturing treatments performed between 1980 and the present that led to the creation of a new approach to refracturing treatments.

This paper discusses the factors to consider when planning a refracturing program. Refracturing failures are also discussed as a means to understand the controllable and uncontrollable variables that lead to these failures. Failures are categorized and specific failure types and modes are identified. Examples of successful refracturing treatments are also included.

The resulting newly developed refracturing approach includes a four-step process:

Candidate identification Refracture diversion design Execution and diagnostics Production analysis and diagnostics

Examples of using the four-step process are provided to show the incremental improvements that resulted from identifying potential candidates and designing, executing, and analyzing the project. Production results and incremental estimated ultimate recovery (EUR) values are discussed to illustrate the economic viability of refracturing, and the economic benefit of this incremental production increase is compared with the cost of the refracturing treatment. While incremental production from refracturing in the midcontinent has more than doubled, pre- and post-fracture diagnostics should improve the success rate by defining lateral coverage. Real-time diagnostic techniques are discussed as potential tools for pre- and post-refracturing analysis.

Despite the history of mixed results, refracturing efforts are improving through the implementation of this new four-step approach. Repressurization of the original fracture system is common to successful refracturing throughout time. New diversion materials and placement processes help achieve repressurization and refracturing placement success. Also, additional insight from new diagnostic tools and techniques can help improve the overall refracturing project success.
Eight-Plus Years of Hydraulic Fracturing in the Williston Basin: What Have We Learned?
Authors: Srinivasan Karthik , Krishnamurthy Jayanth , Williams Ryan , Dharwadkar Pavan , Izykowski Tyler , Moore William Ray
Published: January 2016

Since the inception of the oil boom in North Dakota, the Williston basin has witnessed a tremendous growth in horizontal drilling and completion activity primarily targeting the Bakken and Three Forks formations. Although the activity in the basin is maturing in terms of our understanding rock quality and completion quality, there is a wide variation of these indices within the basin from one field to another. Some of these variations are clearly noticeable in parameters such as thicknesses of the shale barriers, pore pressure gradients, reservoir permeabilities, porosities and stress gradients. The combined impact of these parameters has a huge impact on key decisions including, but not limited to, completion methodologies, types of proppants and fluids used for completion, number of fracturing stages in the lateral, number of perforation clusters per stage, and well spacing.

This paper discusses the evolution of stimulation strategies and completion practices in the Williston basin since 2009. Operators have experimented with cemented and uncemented laterals; sliding sleeves and plug-and-perf completions; lateral lengths ranging from 5,000 to 10,000 ft; perforation clusters ranging from one to six per stage; crosslinked, hybrid, and slickwater fluid systems; proppants ranging from sand to ceramic, etc. The consequent impacts of these variations on well completion pressure responses and long-term production have been mixed. As part of the work covered in this paper, the differences between various completion methodologies and their impact on the stimulation strategies have been discussed in a chronological order.

Although there is no single optimized design for the entire basin, experimentation of multiple methods and technical interpretation of various fracture and production models have provided us with a strong foundation to narrow down our practices to the most successful and repeatable ones across all the fields in the Bakken and Three Forks formations. The paper also covers how real-field measurements such as diagnostic fracture injection tests (DFITs), microseismic data, radioactive or chemical tracers, bottomhole pressure gauges, and interference experiments combined with log measurements such as magnetic resonance, acoustic logs, and elemental spectroscopy can provide us with a strong base for building and calibrating reservoir models that are reliable and reasonable.

The paper covers technical differences between sliding sleeves and plug-and-perf completions; differences between crosslinked, slickwater, and hybrid designs and their impact on fracture geometries; effect of using different proppant types; and ways to optimize the number of fracturing stages and proppant and fluid volumes. As part of the study, the importance of geomechanics in understanding planar versus complex fracture geometries is discussed to close the loop with reservoir simulation models.
Production Benefits from Complexity – Effects of Rock Fabric, Managed Drawdown, and Propped Fracture Conductivity
Authors: Britt Larry K. , Smith Michael B. , Klein Henry H. , Deng J. Y.
Published: January 2016

Many shale plays are being successfully developed throughout North America. Numerous studies have attempted to focus on the possible success mechanisms for these unconventional formations. The focus of these studies tends to fall into two distinct camps, (1) complexity and (2) the rock. It is the intent of this paper to show, however, that these two mechanisms are not distinct and independent and that they are in fact very interrelated.

This paper looks at two main issues: laboratory investigation of the stress sensitivity of un-propped fractures for several active unconventional formations, and Discrete Natural Fracture (DFN) simulation of the effect of this on post-frac production.
Effect of Horizontal Stress Models and Biot Poro-Elasticity on Predicted Fracture Geometry
Authors: Narasimhan Santhosh , Shaikh Hamza , Gray James K. , Cherian Bilu V. , Olaoye Olubiyi , Rifai Rafif , Kublik Kristina , McCleary Matt , Fluckiger Samuel D. , Sharf-Aldin Munir
Published: January 2016

This paper covers the methodology to derive all geomechanical properties (Young's modulus, Poisson's ratio and vertical/horizontal variable Biot constants as a function of rock type) for 13 different stress models. Minimum horizontal stress (Sh) is a key parameter controlling fracture height growth during hydraulic fracturing simulation. Assuming a homogeneous formation (rock property Horizontal:Vertical = 1.0) or poorly derived inputs for the anisotropy model can lead to incorrect fracture geometry. A major assumption made using the various stress models is the Biot poro-elastic constant. Many default models assume a Biot poro-elastic constant of one, which is valid for coarse grained conventional reservoirs where porosity is greater than 20%. Most of the reservoirs stimulated with hydraulic fracturing today do not fall in that porosity range, therefore an alternative derivation for the Biot poro-elasticity and its variability requires additional discussion.

Models derived and compared with their associated uncertainties in this paper include: Ben Eaton – isotropic, anisotropic, dynamic and modified with correction factor; default from auto log calibration; Vernik, Jaeger & Cook; Hubbert & Willis; Thiercelin – MC envelope and stiffness tensors (Cij); Segall & Penebaker. The geomechanical properties from the different stress models noted above were inserted into a gridded fracturing simulator. The outputs were compared to actual job and calibration data for; minimum horizontal stress, end of job net pressure and fracture geometry for each of the models.

When comparing fracture geometries from each stress model against calibration data it is apparent that the chosen stress model will have a substantial influence on the result. This illustrates the importance of choosing the correct stress model for fracture simulations.
Integration of Dynamic Microseismic Data with a True 3D Modeling of Hydraulic Fracture Propagation in Vaca Muerta Shale
Authors: Haddad Mahdi , Du Jing , Vidal-Gilbert Sandrine
Published: January 2016

Microseismic mapping during hydraulic fracturing processes in Vaca Muerta (VM) Shale in Argentina shows a group of microseismic events happening at shallower depth and at later injection time, and they clearly deviate from the growing planar hydraulic fracture. This spatial and temporal behavior of these shallow microseismic events incurs some questions regarding the nature of these events and their connectivity to the hydraulic fracture. To answer these questions, in this paper, we investigate these phenomena using a true 3D fracture propagation modeling tool along with statistical analysis on the properties of microseismic events.

First, we propose a novel technique in Abaqus incorporating fracture intersections in true 3D hydraulic fracture propagation simulations based on pore-pressure Cohesive Zone Model (CZM). The simulations fully couple slit flow in fracture with poro-elasticity in matrix and continuum-based leak-off on the fracture walls, and honor the fracture tip effects in quasi-brittle shale. Using this model, we quantify vertical natural fracture activation depending on reservoir depth, fracturing fluid viscosity, mechanical properties of the natural fracture cohesive layer, natural fracture conductivity, and horizontal stress contrast. The modeling results demonstrate this natural fracture activation in coincidence with the hydraulic fracture growth complexities at the intersection such as height throttling, sharp aperture reduction after the intersection, and multi-branching at various heights and directions.

Finally, we investigate the hydraulic fracture intersection with a natural fracture in the multi-layer VM Shale. We infer the natural fracture location and orientation from the microseismic events map and Formation MicroImager log in a nearby vertical well, respectively. We integrate the other field information such as mechanical, geological, and operational data to provide a realistic hydraulic fracturing simulation in the presence of a natural fracture. Our 3D fracturing simulations equipped by the new fracture intersection model rigorously simulate the growth of a realistic hydraulic connection path toward the natural fracture at shallower depths, which was in agreement with our microseismic observations.
Case Histories in Cost-Efficient Re-Fracturing of Horizontal Wells
Authors: Matt J. D.
Published: January 2016

Objectives/Scope: To identify cost-efficient re-fracturing methods in horizontal wells. We provide a case history of cost-efficient methods in the Eagle Ford, Permian, and Bakken by analyzing over 1000 re-fractured wells.

Methods, Procedures, Process: We have collected data on over 1000 re-fractured wells in our analysis. We incorporate the frac chemistry (slickwater vs gelled frac etc.) for each of the fracture treatments in this analysis. We have also analyzed the production improvements gained from the re-frac. We analyze the individual wells production prior to re-frac and the improved production after the re-frac.

Results, Observations, Conclusions: After standardizing as many variables as possible we have found that slickwater re-fracs with large amount of proppant have provided the highest production increase in terms of absolute production. Initial analysis shows slight differences between the three regions involved in this case study.

Novel/Additive Information: We are not aware of any other large scale public study done on this same topic. We hope that our case study based approach will provide a launching point for future work done on re-fracturing.