bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlating Water Hammer Signatures with Production Log and Microseismic Data in Fractured Horizontal Wells
Authors: Carey Michael A. , Mondal Somnath , Sharma Mukul M. , Hebert Darrell B. 
Published: January 2016

Abstract
A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown or valve closure at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. The result is a pressure profile that consists of a series of oscillations that attenuate over time due to friction. Hydraulic fracture treatments have been shown to alter the period, amplitude, and duration of the water hammer signal. The goal of this study was to history match water hammer data from several multi-stage fractured wells with simulations derived from a water hammer model and compare the results to gathered production log and microseismic derived stimulated reservoir volume (SRV) data.
Water hammer pressure signals were simulated in this study with a numerical model that combined the continuity and momentum equations of the wellbore with a created hydraulic fracture represented by a circuit with a resistance, capacitance, and inertance (R, C, and I) connected in series. Treatment pressure data from three horizontal fractured wells were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained. All three horizontal wells had both production log and microseismic data for each stage, and the R, C, and I values obtained from history matching were compared to production log (gas) and microseismic SRV for any correlations.
It is shown that the water hammer derived capacitance was directly correlated with the stimulated reservoir volume (SRV) derived from micro-seismic measurements, however, it showed no correlation with gas production obtained from the production log. Inertance also showed a positive correlation with SRV but had no correlation with production log data. Finally, the water hammer derived resistance exhibited no correlation with SRV data, but showed a positive correlation with gas production.
The results from this work support the fact that the water hammer signal at the conclusion of a hydraulic fracturing treatment stage, contains diagnostic information about the created fracture network. Since this data can be recorded at very little incremental cost, it may prove to be a very useful and cost effective fracture diagnostic tool.
Well Integrity for Fracturing and Re-Fracturing: What Is Needed and Why?
Authors: King George E. , Valencia Randy L. 
Published: January 2016

Abstract
Fracturing, multiple fracturing and refracturing often create peak loads for well design. The scope of this work is to identify areas of potential damage in older wells being considered for refracturing so that those wells can be flagged for further investigation and repair. Removing damaged well stock from consideration before a well integrity failure can occur protects the environment and also allows time for repairs that protect the future value of the well stock.
New and older well conditions and stimulation methods are discussed with a view towards identifying peak-load factors. Laboratory work and literature study results are also cited to document the connection to previous work and relate literature findings to current stress load causes and isolation damage prevention. Well integrity investigation methods include pressure testing, cement evaluation tools (CET), cement and stimulation pump charts, downhole imaging devices (cameras, calipers, electrical logging tools), and other approaches.
New well fracturing, and particularly multi-fracturing completions can produce stresses on the cement-to-pipe and cement-to-formation seals, although the damage, depending on specific conditions can be minor to moderate and changes to construction techniques can eliminate or minimize most problems. Re-fracturing of wells opens several new areas of concern including corrosion, erosion, and production related issues such as subsidence that may result in a higher risk to barrier elements.
The results of the work illustrate construction methods that can produce wellbores capable of handling significant multi-fracturing stimulation. In addition, risks of re-fracturing damage on damage to older wells are rated with monitoring and remedial operations as part of the discussions. Finally, frac hits (a fracture from one well intersecting and damaging an adjacent well) will be discussed with examples of several factors that are common in frac hits.
Perforation Cluster Efficiency of Cemented Plug and Perf Limited Entry Completions; Insights from Fiber Optics Diagnostics
Authors: Ugueto C. Gustavo A. , Huckabee Paul T. , Molenaar Mathieu M. , Wyker Brendan , Somanchi Kiran 
Published: January 2016

Abstract
It is now well established that the production from horizontal wells completed via hydraulic fracture stimulations (fracs) is highly variable along the length of the wellbore. In addition to subsurface conditions, elements of the completion design, such as fluid volume, proppant tonnage, rate, stage length, the number of perforation clusters and their spacing, influence the performance of individual stimulated intervals and wells. Information about completion efficiency can be obtained using Fiber Optic (FO) diagnostics. Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS) provide great insights into the factors controlling frac construction and performance of each perforation cluster. The integrated analysis of DAS and DTS in horizontal wells completed with multiple perforation clusters per stage indicate that, although most perforation clusters receive fluids during the stimulation, there are significant changes in efficiency during the frac stimulation process that can impact frac connectivity, conductivity and ultimately, their production. This presentation illustrates recent observations about Perforation Cluster Efficiency (PCE) using FO diagnostics and summarizes the results for many wells with Cemented Plug and Perforated completions Limited Entry design (CPnP LE).
Hydraulic Fracture Height Predictions in Laminated Shale Formations Using Finite Element Discrete Element Method
Authors: Li Han , Zou Yushi , Valko Peter P. , Ehlig-Economides Christine 
Published: January 2016

Abstract
Laminated structures in shale formations typically result in anisotropic elastic properties, including Young's modulus and the Poisson ratio, which highly influence hydraulic fracturing treatment execution. The lamina can confine the hydraulic fracture height growth and they sometimes act as weak interfaces for potential fracture propagation path. Hydraulic fracture geometries are highly affected by these properties. In order to make more accurate prediction of hydraulic fracture pattern, especially fracture height, these factors cannot be ignored.
We utilized a recently developed Finite Element-Discrete Element Method (FEDEM) code to simulate the complex fracture propagation in shale formations. This coupled fluid flow and geomechanics simulation can also models multi-fracture, multi well fracture propagation scenarios. For simulating fracture height growth, the bedding planes module (with corresponding mechanical anisotropy properties generation) are incorporated. Both 2D and 3D hydraulic fracture propagation studies can be performed.
Our simulation results show that without considering the mechanical anisotropy effect, the treatment design will be corrupted by the inaccurate prediction of fracture height. To be more specific, in typical mechanical anisotropic formation, fracture height is always smaller than the fracture height in mechanical isotropic formation, and the fracture tends to propagate (at least temporarily) along the bedding plane interfaces. Different bedding plane properties, including bedding plane dipping angle, permeability etc., also have strong influence on the predicted fracture height. We also consider fracture height growth in multi fracture schemes. The stress shadowing effects give rise to non-planar vertical growth and possible fracture branching. The simulations show that hydraulic fracture height growth is substantially restricted in laminated formations.
This paper provides a framework for more realistic prediction of fracture height and fracture pattern evolution in laminated shale formations exhibiting mechanical anisotropy.
Computational Fluid Dynamics Applied to Investigate Development and Optimization of Highly Conductive Channels within the Fracture Geometry
Authors: Gomaa Ahmed M. , Hudson Harold , Nelson Scott , Brannon Harold 
Published: January 2016

Abstract
A conventional proppant pack may lose up to 99% of its conductivity due to gel damage, fines migration, multiphase flow, and non-Darcy flow. Therefore, pillar fracturing was developed to generate highly conductive paths for hydrocarbon to flow. This paper describes experimental results and numerical models of a new method of generating stable proppant pillars The proposed treatment method depends on fingering phenomena observed when a less viscous fluid, that does not carry proppant, is injected to displace a more viscous one that carries proppant. The low-viscosity fluid will channel through the high-viscosity fluid and create isolated proppant pillars. This method promises to reduce proppant costs, pumping horsepower, and gel damage compared to conventional treatments.
Large-scale experiments (Slot tests: 2-ft height and 16-ft length) were performed to evaluate the development and stability of the created channels. In additional, a computational fluid dynamics (CFD) model was constructed using commercial CFD software, to simulate the experiment and to scale it up into full fracture dimensions. The study focused on effects of surface injection rate (1 to 120 bpm) and viscosity ratio (from 2 to 200) between the two injected fluids.
Experimental results and numerical modeling confirmed that viscous fingering phenomena can be used to create a pillar fracture with conductive and stable channels. The numerical CFD model was able to accurately predict the experimental results. Increasing the injection rate reduces the main channel width while increasing the channel branching. Full piston displacement behavior was achieved after 60% of the fracture height, when a high-viscosity fluid displaced a low-viscosity fluid and their viscosity ratio was greater than 5. By reducing the viscosity ratio between the two fluids, the created channel shape converts from cylindrical (where the beginning and end of the channel have the same width) into conical behavior (where the beginning of the channel is wider than the end). This explains why the length of the channel decreases with the viscosity ratio between the two fluids. The distance between proppant pillars tends to be reduced with increasing distance from the wellbore, or with reduced pulse stage volume, time, or rate. A full description of the created channel (distance between proppant pillars) characteristics (size, width and length) will be presented in this paper.
Dry Polyacrylamide Friction Reducer: Not Just for Slick Water
Authors: Sanders Michael , Felling Kyle , Thomson Steve , Wright Steve , Thorpe Russell 
Published: January 2016

Abstract
Objective/Scope: The initial goal of the project was to investigate the use of dry polyacrylamide (PAM) friction reducers as a replacement for more typical Liquid emulsion Friction Reducers (LFR) to save cost and simplify operations. In addition to using dry PAM as a slick water friction-reducing agent, the project team expanded the scope to include the idea of using it as a proppant carrier and viscosifier, a function generally done with a gel-based system. From an operating perspective, eliminating the need to switch between a slick water system and a gel-based system is attractive.
Methods, Procedures, Process: Examination of rheological properties at various temperature and salt concentrations provided background data for field trials. Friction flow loop testing provided indications of performance and compatibility. Comparative field trials of liquid vs. pre-hydrated dry friction reducers determined the benefits and best operating conditions for use of Dry Friction Reducer (DFR). Finally, a case study comparison of liquid vs. dry friction reducer is presented.
Results, Observations, Conclusions: The pre-hydrated dry friction reducers reduced fracturing pressures by more than 1,000 psi at equivalent polymer loadings, substantially lowering costs. Dry PAM friction reducers were able to convey sand concentrations of over 5 ppt (pounds per thousand gallons) and could likely conduct higher concentrations.
Novel/Additive information: The simplicity of utilizing a single polymer system to conduct slick water operations as well as increased rheology applications provides ease, convenience, increased versatility, and savings to the Exploration and Production (E&P) operator.
High Concentration Polyacrylamide-Based Friction Reducer Used as a Direct Substitute for Guar-Based Borate Crosslinked Fluid in Fracturing Operations
Authors: Motiee Monet , Johnson Maxwell , Ward Brian , Gradl Christian , McKimmy Michael , Meeheib Jeremy 
Published: January 2016

Abstract
Traditionally, friction reducer systems have been used to promote laminar flow in pipe to reduce friction pressure in pumping of low viscosity, slickwater-type fracture treatments. In these types of treatments, velocity is the key factor in proppant transport into the reservoir. Typical testing of these conventional friction reducer fluid systems focuses primarily on the chemical's ability to reduce treatment pressures and permit higher fluid velocities.
In an effort to reduce completions costs and improve operational efficiency while maintaining baseline well productivity, our Completions Team applied these conventional friction reducers in an unconventional way. The project used high concentrations of friction reducer (HCFR) as a direct replacement for a guar-based borate crosslinked system without modification to the standard treatment and proppant schedule. The team took steps to qualify the fluid for field implementation, including low shear rate viscosity testing, proppant settling testing, and regained conductivity testing.
Following qualification and operational planning, the team performed field trials. The data showed a reduction in footprint and overall horsepower requirements. The reduced volume and number of chemicals on location led to decreased exposure to hazardous chemicals and also simplified logistics, resulting in fewer truck movements on location. The reduction in chemicals impacted the economics of the well completion positively. The stimulation costs of the wells treated with HCFR when compared to the wells treated with the baseline fluid design showed a chemical cost reduction of approximately 22% per well.
In addition to the cost and operational efficiency benefits observed in the project, initial production data indicates that the wells are meeting or exceeding baseline productivity curves.
Improved Frac Design and Reservoir Simulation Using Strain Derived from Geomechanical Modeling - Application to the Fayetteville Shale
Authors: McKetta Steven , Vargas-Silva Sandra , Ouenes Ahmed 
Published: January 2016

Abstract
A workflow that uses the strain derived from geomechanical modeling of hydraulic fractures interacting with natural fractures is applied to a Fayetteville shale well. The derived strain map is used to estimate the asymmetric half lengths that are input in a frac design software able to incorporate this information. The usual symmetric bi-wing design is replaced by realistic asymmetric half lengths observed in microseismic data by adjusting the leakoff coefficient, injection rate and the proppant concentration in such a way that the asymmetric half lengths of the frac design do not exceed the lengths of those provided by the strain map. Once the half lengths and orientation from the frac design match those provided by geomechanical simulation, the propped length and other key results provided by the frac design software are used in reservoir simulation. The derived strain is correlated to stimulated permeability through two calibration constants estimated during history matching. After history matching, the resulting pressure distribution facilitates more informed selection of refrac or new well candidates, optimization of well spacing, and estimation of an accurate EUR.
Optimal Perforation Location and Limited Entry Design for Promoting Simultaneous Growth of Multiple Hydraulic Fractures
Authors: Cheng Cheng , Bunger Andrew P. , Peirce Anthony P. 
Published: January 2016

Abstract
The objective of achieving uniform stimulation of a reservoir through hydraulic fracturing from a horizontal well typically depends upon the ability to generate a uniform array of hydraulic fractures from multiple entry points. However getting all the hydraulic fractures in an array to grow simultaneously is a challenge. The challenge apparently arises not only due to reservoir variability, but also in a substantial part due to the stress interaction among growing hydraulic fractures. This phenomenon, referred to as a stress shadowing, inhibits the growth of inner fractures and favors the growth of outer fractures in the array. Recently, we created a new hydraulic fracture simulator which simulates the growth of an array of hydraulic fractures in 10−6–10−5 of the computation time required for fully coupled 3D simulations of multiple parallel planar hydraulic fracture growth. Using a novel energetic approach to account for the coupling among the hydraulic fractures and through judicious use of asymptotic approximate solutions, the simulation enables designs reducing the negative effects of stress shadow by balancing the interaction stresses through non-uniform perforation cluster spacings. Furthermore, so-called limited entry approaches are thought to be capable of promoting greater uniformity among simultaneously growing hydraulic fractures as long as the number and diameters of the perforations in each cluster are appropriately designed. In order to enable such optimizations and designs, we add perforation loss into to the approximate, energy-based simulator. Our results show the potential of choosing the proper perforation diameter and number to double the fracture surface area generated by a given injected fluid volume though minimizing the negative effect of interaction. The usefulness of the new simulator is demonstrated by development of example limited entry designs and optimal spacings for different numbers of entry points.
Les lacunes de la correspondance entre Saint Augustin et Paulin de Nole
Authors: Courcelle Pierre 
Published: January 2016

L'édition Goldbacher du Corpus de Vienne fournit quatre lettres conservées de Paulin à Augustin et huit lettres conservées d'Augustin à Paulin. Lietzmann a déjà noté que ces lettres portent trace de neuf lettres perdues. Une étude plus attentive permet d'ajouter à ce compte une lettre conservée d'Augustin (le De cura pro mortuis gerenda.) et seize lettres perdues (dix de Paulin, six d'Augustin), auxquelles font allusion soit les lettres conservées, soit les autres œuvres d'Augustin.
Grâce à ces trente-huit lettres échelonnées sur vingt-six ans (de 395 à 421), nous apercevons le mode de conservation de cette correspondance aux archives d'Hippone et l'évolution de l'amitié entre Augustin et Paulin. Cette amitié eut à surmonter deux moments de crise, l'un après le sacre d'Augustin, l'autre lors de l'affaire pélagienne ; l'influence de Paulin sur la spiritualité d'Augustin, celle d'Augustin sur la réflexion théologique de Paulin se précisent. Cette correspondance contient aussi des allusions de haut intérêt à l'histoire littéraire (la genèse des Confessions) et à l'invasion wisigothique (projet de repli de la communauté de Nole en Afrique, sac de Nole, rapatriement des réfugiés italiens) .
Esquisse d'une histoire de la sculpture régionale de Gaule romaine, principalement dans le nord-est de la Gaule
Authors: Hatt Jean-Jacques 
Published: January 2016

L'auteur distingue dans cette esquisse d'une histoire de la sculpture gallo-romaine les périodes suivantes :
1° L'archaïsme, sous Tibère, jusque vers 40 ap. J.-C. L'art est alors fidèle aux traditions techniques indigènes, mais sous la dépendance de certaines influences venues de Cisalpine.
2° Le premier classicisme claudien et néronien. L'influence romaine domine alors et quelques éléments d'hellénisme font leur apparition ; le style est baroque et provincial. Cependant, à la même époque, deux autres tendances divergentes se manifestent : le réalisme indigène, qui annonce le développement de la sculpture régionale du IIe siècle, l'hiératisme et la stylisation, qui prolongent les tendances indigènes.
3° Au cours de l'époque flavienne, le baroque régional est à son apogée ; des influences venues de Rome par Narbonne se font sentir dans la Gaule du Nord-Est.
4° La première moitié du IIe siècle est l'époque de l'hellénisme triomphant. Des artistes hellénistiques se fixent en Gaule, y travaillent et font école.
5° La seconde moitié du IIe siècle est marquée par l'apparition en Gaule d'éléments orientaux. L'imagerie des Mystères, et particulièrement celle du culte de Mithra, répand la vogue d'un style mystique, romantique et tourmenté.
6° La renaissance politique et militaire du temps des Sévères est accompagnée d'un néo-classicisme, qui exerce une forte influence sur les arts populaires régionaux. À partir de 240, la décadence de l'influence romaine amène une véritable résurrection de l'art gaulois.
7° La renaissance constantinienne, qui a produit dans le rayon d'influence des empereurs de Trêves quelques œuvres remarquables, a exercé une certaine action dans le Nord-Est de la Gaule. Mais le style et la technique sont en nette dégénérescence, et ce dernier sursaut de l'académisme gréco-romain est sans vigueur.
Les deux premiers traités entre Rome et Carthage
Authors: Aymard André 
Published: January 2016

La clause du deuxième traité relative au Latium (Pol., III, 24, 5) ne peut pas se comprendre seule : elle postule le maintien de tout ce qu'elle ne modifie pas dans les clauses du premier traité relatives aux cités latines (III, 22, 11-13). De même, aucune clause du premier traité n'est reprise telle quelle dans le deuxième : il n'est pas une phrase de celui-ci qui n'apporte une modification au libellé du premier. Dès lors, le deuxième traité n'a pas été rédigé pour annuler le premier, mais uniquement pour l'amender, en laissant en vigueur toutes les clauses qui ne se trouvaient pas modifiées : le deuxième est déjà au premier ce que, d'après Polybe (III, 25, 1), le troisième est au deuxième.
Il s'ensuit que le premier traité ne peut pas se dater de 509, alors que le deuxième se placerait seulement en 348 : l'écart chronologique serait trop grand. Tous deux doivent dater du IVe siècle.
La causalité historique chez Tacite
Authors: Michel Alain 
Published: January 2016

La terminologie et les idées de Tacite, d'après certains commentateurs, hésitent entre stoïcisme et scepticisme. Mais il est possible d'atténuer ces contradictions apparentes si l'on étudie la rhétorique de l'historien et la philosophie qui s'en dégage. Peut- être rejoindra-t-on ainsi par une autre voie les conclusions de W. Theiler et P. Grenade sur le stoïcisme de Tacite, à propos des Annales (VI, 22).
Le destin est l'enchaînement éternel des causes. Or, les rhéteurs ont médité sur la causalité et souligné qu'elle met en jeu, d'une part, la raison (causes objectives), d'autre part, les passions (mobiles subjectifs), qui ne sont, d'après les philosophes, que de fausses opinions.
Certaines des contradictions de Tacite tiennent à la différence de ces deux aspects. Tantôt l'historien parle de causes réelles — elles dépendent alors du destin — tantôt, très souvent, de mobiles passionnels ou imaginaires — et alors il nie que le destin soit en cause.