bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drawdown in embankments
Authors: Stephenson D 
Published: October 2009

The recession of the phreatic line in an embankment following sudden drawdown of a reservoir is studied. The non-equilibrium equation for flow in porous media is simplified and solved to produce general charts indicating the variation of the water surface with time. Charts for the cases of a battered cut and a triangular embankment are presented. The point of emergence of the phreatic line is considered and the relationship between the storage coefficient and coefficient of consolidation is explained. On étudie l'abaissement de la nappe phréatique dans un remblai à la suite d'un affaissement brutal d'un réservoir. L'équation de non-équilibre pour l'écoulement dans un milieu poreux est simplifiée et résolue pour produire des graphiques généraux indiquant la variation de la surface de l'eau avec le temps. Des graphiques pour les cas d'une coupe inclinée et d'un remblai triangulaire sont présentés. Le point d'emergence de la nappe phréatique est considéré et la relation entre le coefficient d'accumulation et le coefficient de consolidation est expliquée.
The stability of shallow tunnels and underground openings in cohesive material
Authors: Davis E. H. , Gunn M. J. , Mair R. J. , Seneviratine H. N. 
Published: October 2009

A basic engineering decision to be made in designing a tunnel in soft clay is whether or not the tunnel can be excavated without internal support. The safety of constructing a shallow heading in soft clay can be assessed in terms of the fluid support pressure which may be required to maintain stability. This can be estimated by means of the lower and upper bound theorems of plasticity. The Paper considers three different shapes of shallow underground opening relevant to tunnelling and upper and lower bound stability solutions are derived for collapse under undrained conditions. Solutions are also derived for assessment of the risk of blow-out failure caused by excessively high fluid pressures. Conditions are considered under which local collapse can occur, independent of the cover above the tunnel. Une décision fondamentale doit être prise lorsque l'on veut réaliser un tunnel dans de l'argile molle; il s'agit, en effet, de décider si un support interne sera ou non nécessaire pour l'excavation du tunnel. La sécurité de la construction d'une galerie peu profonde dans de l'argile molle peut être évaluée en fonction de la pression du fluide support qui pourrait être nécessaire au maintien de la stabilité. Cette estimation peut se faire à l'aide des théorèmes à limites inférieure et supérieure. L'article envisage trois formes différentes d'ouverture souterraine peu profonde intéressant le creusement de tunnels, et des solutions de stabilité à limites inférieure et supérieure sont trouvées pour l'affaissement dans des conditions non drainées. Des solutions sont également trouvées en ce qui concerne l'évaluation du risque de rupture par éruption due aux pressions excessives du fluide. Les conditions dans lesquelles un affaissement local peut se produire sont envisagées, indépendamment de la couverture située audessus du tunnel.
Behaviour of a propped embedded retaining wall in stiff clay at Bell Common Tunnel
Authors: Tedd P. , Chard B. M. , Charles J. A. , Symons I. F. 
Published: October 2009

Extensive instrumentation has been installed at Bell Common Tunnel to monitor the performance of a propped embedded retaining wall and the behaviour of the stiff clay in which it has been constructed. Earth and porewater pressures, ground and wall movements, and roof loading have been monitored during the construction period. The deformations and stresses measured at each stage of construction are presented and the performance of the wall is discussed. Un système important d'instrumentations a été installé au tunnel de Bell Common pour contrôler le comportement d'un mur de soutènement encastré et celui de l'argile raide dans laquelle il a été construit. Pendant la période de construction on a contrôlé les pressions du sol et de l'eau interstitielle, les mouvements du sol et du mur et le chargement du mur. L'article presente les déformations et les contraintes mesurées à chaque étape de la construction et analyse le comportement du mur.
An experimental and theoretical comparison between static and dynamic torsional soil tests
Authors: Bolton M. D. , Wilson J. M. R. 
Published: October 2009

The dynamic properties of dry Leighton Buzzard sand have been investigated using a resonant column test apparatus. These data are compared with very low frequency cyclic tests on identical specimens of sand. The comparison indicates that the properties of dry sand are independent of frequency. A simple one-dimensional model of kinematic hardening plasticity is used to predict the dynamic behaviour of the sand. The input parameters for this model are based on the results of static tests. These may be conducted on standard laboratory equipment with only minor modifications. The predictions are in good agreement with the measured data. In particular, the frequency response close to resonance was correctly shown to be asymmetric and the reduction in the resonant frequency with increasing strain amplitude was also correctly represented. The practical consequences of these findings are assessed with regard to soil testing procedures and dynamic analyses of foundations. Particular emphasis is placed on the dynamic analyses of the foundations for vibrating machinery and offshore gravity structures. Lea propriétés du sable set de Leighton Buzzard ont été étudiées a l'aide d'un appareil de laboratoire employant une colonne de résonance. Ces données sont comparées avec des essais cycliques de fréquence trés basse effectués sur des échantillons identiques du sable. La comparaison indique que les propriétés dn sable set ne dépendent pas de la fréquence. Un modéle trés simple unidimensionnel de la plasticité de durcissement cinématique a été employé pour prédire le comportement dynamique du sable, les parametres d'entrée pour ce modèle étant basés sur les réultats d'essais statiques, qui peuvent s'effectuer sur des appareils normaux de laboratoire avec des modifications de faible importance. Les prédictions s'accordent s bien aux donées mesurées. En particulier la réponse de fréquence asymétrique prés de la résonance et la réduction de la fréquence de résonance avec des amplitudes croissantes de déformation ont été rep résentées de façon exacte. Les conséquences pratiques de cette étude sont examinées en fonction des procedures pour tester le sol aussi hien que des analyses dynamiques des fondations. On examine plus particuliérement les fondations pour les machines oscillantes et pour les structures gravitationelles au large.
Design aspects and permeability testing of natural clay and sand-ben tonite liners
Authors: Van ree C.C.D.F. , Weststrate F.A. , Meskers C.G. , Bremmer C.N. 
Published: October 2009

A methodology has been developed to evaluate the permeability performance of natural clay and sand-bentonite liners using undisturbed field samples of the actual liner. The tools necessary to apply it to the design and inspection of new liners are described. Test results are presented and the influence of the testing procedures is described. The overall performance of liner systems are only partially characterized by their permeability. Other factors, including physico-chemical processes, are equally or even more important, and have to be considered in the design phase. To demonstrate this simulation results on contaminant transport taking geochemical reactions into account as well as some results of leachate compatibility testing of a sandbentonite liner are presented. Une méthodologie a été développée pour évaluer les performances en perméabilité des revêtements d'argile naturelle et de sable/bentonite en utilisant des échantillons de chantier du revêtement même. L'article décrit les instruments nécessaires pour son application à la construction et au contrôle des nouveaux revêtements. Des résultats expérimentaux sont présentés et l'influence exercée par les essais est précisée. Les performances générales des systèmes de revêtement ne sont caractérisées qu'en partie par leur perméabilité. D'autres facteurs, compris des phénomènes physico-chimiques, ont une importance égale ou même supérieure et doivent être pris en considération dans l'établissement des projets. Pour illustrer cette simulation l'article présente des résultats concernant la migration des polluants tenant compte des réactions géochimiques et aussi des résultats obtenus au cours d'essais effectués pour étudier la compatibilité des lessivages dans le cas d'un revêtement de sable-bentonite.
Interaction behaviour of steel grid reinforcements in a clayey sand
Authors: Bergado D. T. , Shivashankar R. , Alfaro M. C. , Chai Jin-Chun , Balasubramaniam A. S. 
Published: October 2009

The interaction behaviour between steel grid reinforcements and a clayey sand has been studied in laboratory and field pullout tests. The clayey sand is potentially useful as cheap, low quality, locally available and cohesive-frictional backfill in the construction of mechanically stabilized earth walls and embankments, especially in coastal areas. The laboratory tests were conducted under undrained conditions at three compaction moisture conditions. The field tests were conducted on dummy reinforcements embedded at different elevations in a full-scale test embankment resting on soft clay foundation. The laboratory tests revealed that the moisture content of the compacted soil, compaction stress, applied normal stress level, diameter and spacing to diameter ratios of the transverse members of the steel grid, all affect the soil-reinforcement interaction, and thereby, also the magnitudes of the pullout resistances. Interferences between the bearing transverse members of the grid were found to be less significant for spacing to diameter ratios above 75. The laboratory tests, in general, gave conservative values of the pullout resistances as compared with the field tests. The proposed prediction equations agreed well with the experimental data. L'interaction entre les renforcements par treillis métalliques et les sables argileux a été étudiée à l'aide d'essais de traction en laboratoire et sur chantier. Le sable argileux est utilisé pour construire des murs en terre mécaniquement stabilisés et des remblais, dans les zones littorales notamment. Ce type de matériau est en effet un matériau de remplissage cohérent-frottant bon marché, de qualité médiocre et disponible localement. Les essais de laboratoire ont été menés, dans des conditions non-drainées, avec trois teneursen eau de compactage. Les essais de chantier ont été réalisés sur des renforcements ancrés à différentes profondeurs dans un remblai grandeur nature reposant sur des argiles molles. Les essais de laboratoire ont montré que la teneur en eau du sol compacté, la contrainte de compaction, le niveau de contrainte normale, le diamètre et les rapports espacement-diamètre des composants transversaux du treillis métallique jouent sur les interactions renforcement-sol, et par conséquent, sur la grandeur de la résistance à la traction. Les interférences entre les éléments porteurs transversaux du treillis semblent moins importantes pour des rapports espacement-diamètre supérieurs à 75. Les essais de laboratoire donnent, en général, des valeurs de résistance en traction plus reproductibles que celles obtenues dans les essais de chantier. Les équations proposées pour la prédiction du comportement sont en bon accord avec les données expérimentales.
Basic creep of unsealed hardened cement paste at temperatures between 20°C and 725°C
Authors: Dias W. P. S. , Khoury G. A. , Sullivan P. J. E. 
Published: October 2009

Synopsis A definition for basic creep at elevated temperatures is arrived at, based on the time at which load is applied. Experimental results are presented for the basic creep of hardened cement paste and comparisons are made with the behaviour of various concretes. The time function of basic creep is shown to follow a power law relationship, whereas the temperature function indicates that a rheological property, seated in the cement paste itself, would limit the structural usefulness of Portland cement-based concretes to below 600°C. Preheating to temperatures higher than the creep test temperature reduces the creep potential in general.
Carbonation of concrete containing pfa
Authors: Hobbs D. W. 
Published: October 2009

Synopsis A limited investigation of the influence of 35% replacement of one OPC by two pfa's upon rate and depth of carbonation, strength development and water retention of concrete cubes is described. It is shown that both water retention and strength development of OPC/pfa concretes may be more adversely affected by short-term curing than those of OPC concretes and that the depth of carbonation in concretes of a similar water/binder ratio or similar binder content can be substantially higher in OPC/pfa concretes than in OPC concretes. The depth of carbonation of the OPC/pfa concretes tested after 3 years is similar or slightly higher than in the OPC concretes of similar 28 day compressive strength.
Predicting Sorption-Induced Strain and Permeability Increase With Depletion for Coalbed-Methane Reservoirs
Authors: Clarkson C.R.. R. , Pan Z.. , Palmer I.. , Harpalani S.. 
Published: October 2009

Summary
It is well known that absolute permeability changes occur in coalbed methane (CBM) reservoirs during primary depletion or enhanced recovery/CO2 sequestration operations. Sorption-induced strain in CBM reservoirs, also known as matrix shrinkage or swelling, may dominate permeability changes at low pressures, as is the case for CBM wells undergoing primary depletion in the Fruitland coal fairway of the San Juan basin.
Several analytical models have been developed to predict changes in coal permeability as a function of stress and sorption. Most models, however, utilize an empirical method for estimating sorption-induced strain. Recently, a theoretical model for sorption-induced strain was developed and applied to single-component adsorption/strain experimental data. The new model was developed from basic thermodynamic principles and is more predictive than the empirically based approaches. In this paper, the theoretical model is expanded to incorporate multicomponent adsorption models that are more rigorous, and sometimes more accurate, than the commonly applied extended Langmuir (EL) equation. This improves predictions of multicomponent gas sorption-induced strain, as demonstrated by comparison to experimental data. The new sorption-induced strain model is then used to calculate the sorptionstrain component of the popular Palmer and Mansoori (P&M) equation, which, in turn, can be used to model permeability changes during both primary (single- or multicomponent gas) and enhanced recovery operations. Finally, the coupled sorption-strain/permeability model, incorporated into an analytical simulator, is used to predict and match permeability growth in a producing CBM well in the Fruitland coal fairway, which has a binary (CH4 + CO2) sorbed/produced gas composition.
Matches to field-derived permeability growth using the new model are accurate but nonunique because of the lack of available data, particularly rock mechanical properties. Given the availability of rock mechanics and adsorption isotherm data, the rigorous thermodynamic basis of the new model should allow for more accurate predictions of coalbed permeability changes, but further testing is required.
Specially Formulated Drilling Fluid Prevents Differential Sticking, Mud Losses, and Wellbore Instability in Oil and Gas Wells in Saudi Arabia
Authors: Al-Ansari Adel A. , Al-Mutair Faisal M. , Al-Kilani M. H. , Al-Haidary Saleh A. , Al-Baloosh Mishal S. , Al-Nimer A. A. , Al-Zahrani Walid G. , Veloo Vickneswaran , Villalobos Mario 
Published: October 2009

Abstract
Differential sticking can be a significant cause of lost time and non-productive cost where formations with varying permeability are drilled. In some instances, operators have limited choice and drilling overbalanced through lower pressured formations is necessary to meet well design targets. Higher permeability sections result in high rates of fluid loss into the formation, thick filter cakes and a significant risk of the drillstring becoming differentially stuck.
A novel approach to preventing such incidents was introduced in Saudi Arabia in 2006. The treatment/system relies on a combination of two new products added to the mud system; a synthetic graphite and an organic polymer which, in combination, provide an effective seal against high permeability formations and substantially reduce occurrences of differential sticking.
The synthetic graphite and the polymer, (added in the form of an aqueous emulsion) sizes are important factors in the success of this approach. Strategies to maintain the correct level of products in the mud system during drilling are discussed in conjunction with examples of successful field applications.
Laboratory work, designed to improve on previously existing guidelines for product application in different formation types and a proposed method of determining the graphite concentration in the mud by analytical analysis are also presented. Data from all field applications to date are summarized, showing that the system described is highly effective at eliminating differential sticking, mud losses and wellbore stability issues.
Costly Shoe-Track Drilling Practices Using Conventional and Rotary-Steerable Systems Evaluated: A Summary of Lessons Learned, Proposed Best Practices, and Software-Driven Recommendations
Authors: Rogers Hank , Webb Earl , Tilley Jim , Fears Brett 
Published: October 2009

Abstract
Drilling operations performed through the shoe-track are generally considered duplicated effort by many operators. Nonetheless, shoe-track drillout is an operation that must be performed on all surface or intermediate casing strings or liners. Slow penetration rates are often experienced, even when drilling through so-called drillable casing equipment. Today's costly drilling operations force operators to attempt to reduce nonproductive operations whenever possible. Therefore, improved shoe-track drillout performance can improve operators' overall drilling cost and schedule. Thus, a better understanding of downhole dynamics is necessary to develop improved drilling procedures.
A review of jobs from the North Sea database of cement jobs and shoe-track drillouts revealed that, of the more than 1,200 data points available to the authors, 83% of the drillout times were less than three hours; 70% of the drillout times were less than two hours; and 50% of the drillout times were less than one and one-half hours, with the overall average being 93 minutes. When a single type of cementing casing equipment was drilled in some wells in 30 minutes and other wells in three hours, questions were raised as to what major contributing factors determine actual drillout time.
Two case histories are presented with close attention paid to drilling parameters that adversely affect actual weight applied by the bit to the target being drilled. A better understanding of weight on bit (WOB) and weight on target (WOT) is needed to best determine drilling procedures to be used for any given drillout.
This paper documents lessons learned from successful drillouts performed with conventional and rotary-steerable drilling assemblies. Software-driven recommendations are provided for improved interpretation of downhole forces applied to the target being drilled.
Preventing Shallow Water Flow in North Sea Exploration Wells Possibly Exposed to Shallow Gas
Authors: Opseth T. Landbø , Ribesen B. T. , Tran T. N. , Hinton A. , Laget M. , Lende G. , Saasen A. 
Published: October 2009

Abstract
Originally, shallow water flow was severely hindering further drilling in a North Sea exploration well. The water depth was 111.5m. The 20" casing was set at 590m; above a shallow gas zone. After mounting the Blow Out Preventer (BOP), drilling the 17 ½" section started and continued for a few 100 meters. The wellhead was routinely inspected using an ROV (Remotely Operated Vessel). After some time, a tiny flow was observed around the wellhead. The flow increased in strength and later a large wash out area was observed, and further drilling had to be terminated. Most likely, the water flow originated from a zone at a depth of 172m MSL.
To cure the shallow water flow it was decided to grout cement on the outside of the casings. Regular well cements was not desirable to use since these cements are somewhat retarded in itself by mineralogical composition. It was decided to use standard construction industry cement with a very short curing time. Before the grouting could start the BOP had to be removed. Because of the shallow gas zone underneath the 20" casing, two barriers had to be included in the well for well control. Two packers were used, one drillable and one retrievable. The BOP was removed and the grouting operation was performed successfully. No water flow or gas flow were observed while the cement was setting. After the flow was cured drilling resumed, first by drilling and retrieving the packers, then continuing to drill the 12 ¼" section.
The lessons learned from this particular well are to focus on using rapid hardening industry cement when cementing the conductor and a foamed cement system around the surface casing. Furthermore, a riserless mud return system has been used on later wells to be able to drill with weighted drilling fluid prior to setting the riser. These solutions to prevent shallow water flow are further discussed and experiences from later wells are presented in the following paper.
Dealing with the Challenges of UBD Implementation in Southern Iranian Oilfields
Authors: Shadravan Arash , Nabaei Mohammad , Amani Mahmood 
Published: October 2009

Abstract
Approximately 90% of the discovered fields in Iran are in carbonate reservoirs making this country as one of the largest carbonate producers in the world. Iranian depleted zones are increasing, as most of the fields become mature. High pressure drop in most of these fields such as Parsi, Karanj, Aghajari, Gachsaran, Bibi Hakimeh, Lab Sefid, Dehloran, Danan and Mal Kouh caused several drilling and production problems. The current condition for new operation challenges in Iranian oilfields emphasizes the significance of utilizing new tools and methods.
Implementing underbalanced drilling (UBD) technology in Parsi oilfield, located in south western part of Iran, may offer a solution to the challenges of operations of the field. Parsi has undergone substantial pressure loss over its history of nearly 50 years, and it is characterized by the highly fractured, vuggy Asmari formation. That combination of a challenging reservoir and low pressure has led to increasing problems for traditional overbalanced approaches. Many papers have been published discussing potential UBD advantages for southern Iranian oilfields; however, few papers are available about the challenges of this technology. Despite the increasing experience in this field, the value of UBD has not been fully acknowledged. This paper investigates the main UBD challenges in Parsi oilfield and summarizes the solutions to deal with them.