bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Studies on the Dependency of Temperature and Fluid Pressure on Fault Zone Strength, Slip Displacement and Sealing Potential
Authors: Odedra Anita , Sammonds Peter , Ohnoka Mitiyasu 
Published: December 2007

Abstract
Temperature and pressure sensitive processes modify rock strength and fault properties with depth. A series of triaxial shear fracture experiments have been conducted on granite under fixed confining pressures (70 to 480MPa), pore fluid pressures (10 to 300MPa) and temperatures (room temperature to 4800C) to investigate relationships between ambient crustal conditions, rock strength and fault displacement. We report here the first investigations of rock fracture experiments under elevated temperatures in the presence of high pore pressures. Our results improve existing models of fault slip displacement and rock strength with depth, based on dry experiments, by incorporating a more realistic water saturated crust, and considering the sealing effect on faults caused by high temperature welding.
The effect of ambient conditions on rock shear fracture parameters may be summarised as follows: rock strength with depth of burial is relatively constant up to temperatures of 3000C, after which strength decreases rapidly. Increasing pore fluid pressure mechanically reduces the strength of rock at all temperatures, and also reduces the amount of fault displacement. Temperature dependent processes at depth may allow a fault to seal (due to welding and mixed deformation processes), but simultaneously leak' nearer the surface (due to brittle fracture induced porosity).
P. 323
A Soil Mechanics Approach To Predict Cement Sheath Behavior
Authors: Thiercelin M. , Baumgarte C. , Guillot D. 
Published: December 2007

Abstract
In this paper, we predict the bulk shrinkage of oil well cements using a soil mechanics model where compaction is a dominant mechanism. In our approach, the bulk shrinkage is the result of the decrease in pore pressure following cement hydration. We perform triaxial tests on set cements to calibrate the model. We perform laboratory experiments to demonstrate the applicability of this approach to shrinkage prediction. We simulate the downhole conditions to predict the consequences of shrinkage on zonal isolation.
P. 329
Analysis of Hydraulic Fracture Closure in Laboratory Experiments
Authors: van Dam D.B. , de Pater C.J. , Romijn R. 
Published: December 2007

Abstract
Conventional models of hydraulic fracture closure make assumptions about the fracture geometry and rock mechanical behaviour, In this paper we present the results of scaled laboratory experiments, We show that deviations from conventional assumptions influence leak-off volumes, mechanical behaviour, and pressure decline significantly. We discuss mechanisms that lead to deviations from assumptions during fracture closure.
P. 365
Influences of Heat Convection and Plastic Deformation on Hydraulic Fracture Initiation and Reservoir Compaction
Authors: Shao J.F. , Homand S. 
Published: December 2007

Abstract
In hydraulic fracturing technique, one of the questions is to determine fracture initiation pressure. The resolution of this problem should account for the coupling between material deformation, fluid flow and temperature variation. A finite element solution is proposed in this paper by taking into account non linear coupling due to heat convection and plastic deformation of rocks. A specific numerical algorithm is used to treat long time injection problem. A typical example of cold water injection through a vertical well is then considered. Comparative calculations made with and without heat convection have clearly shown the key role of heat convection in diffusion of stresses, pore pressure and temperature around the well. Two particular issues, reservoir deformation induced by injected cold water (cooling and pore increase) and influence of thermal stress diffusion by convection on hydraulic fracture initiation, are examined. The main finding is that the stress and temperature diffusion is quasi completely controlled by convection. The cold water injection induces relative reservoir compaction, which can become significant (reservoir subsidence) when the injection pressure is low. Concerning fracture initiation pressure, the tangential stress evolution is also strongly controlled by heat convection. The temperature decrease (cooling) induces a significant and time dependent tensile tangential stress zone where the breakdown pressure may be much smaller than that determined without considering heat convection. Moreover, heat convection accelerates the propagation of the tensile stress zone (consequently the fracture propagation) into reservoir. Finally, in the cases studied in this paper, rock plastic deformation plays a secondary role with respect to heat convection.
P. 401
Viscous Rheology and State of Stress in Unconsolidated Sands
Authors: Chang C.T. , Zoback M.D. 
Published: December 2007

Abstract
Observations of triaxial creep and stress relaxation of unconsolidated reservoir sands imply markedly different static and dynamic modulii and may explain observations of very low differential stresses found in the Wilmington Field, CA, the Gulf of Mexico, and elsewhere. Triaxial testing performed on 1 inch plugs of reservoir sands under both stress- and strain-controlled conditions show transient stresses and strains. All tests were performed under dry or drained conditions to eliminate poroelastic effects. We previously observed creep under hydrostatic stress conditions in these unconsolidated sands. The resulting strain vs. time curves could be fit with a standard linear solid viscoelastic model that had a relaxation time of about 10 hours. The data demonstrates the rock's ability to dissipate stress through relaxation and creep. The reservoir material shows viscoelastic rheological behavior in both creep and relaxation tests which appears to be related to the presence of intergranular clay. Measurements of the static Poisson's ratio under large strains yielded values .29 which suggests that the particles in the matrix efficiently coupled the principle strains.
P. 465
Management of Competence in HSE and Application in Training Redesign
Authors: van Kujk E. , van der Velden J. 
Published: December 2007

Abstract
This paper presents the findings and recommendations of a study on the management of competence in the areas of Health, Safety and Environment from an organisational perspective. A conceptual model is developed which describes the management of business processes and the aspect controls for the associated business risks. Within the study, HSE is considered as one of the business risk areas. Progress in competence management in each of the elements of the model was assessed through a survey. The results of this survey support the integrated approach, which is being developed. Skills portfolios have recently been formulated, covering the technical disciplines and business skills for individuals and teams. These skill requirements are supplemented with the required competencies to execute the tasks and maintain the barriers identified in the Hazard and Effect Management Process [1]. Results from a case-study confirm the value of the approach in the development of learning and training programmes as well as provide a tool to assess and demonstrate the extent to which the existing competence assurance programmes match the requirements identified in HSE cases.
Unique PDC Bit Technologies Combine to Consistently Reduce Drilling Time in Interbedded Formations
Authors: Taylor S. , Besson A. , Minto D. , Mampuk I. 
Published: December 2007

Abstract
Interbedded formations cause difficulty when selecting a drill bit for optimum section performance. Hard stringers require bit features that conflict with those required for softer homogeneous formations. Limited by conventional technology, this culminates in the selection of a bit too heavy set to maximise penetration rates through the soft formation or too light set to drill the hard stringers. This paper describes a unique combination of PDC bit technologies that provide a solution to consistently drill interbedded formations without compromising bit selection. The unconventional design consists of features to maintain high penetration rates in soft formations and the stability and life required to pierce through hard stringers.
The technologies are combined on a steel bit body. The nature of this material allows its fundamental engineering properties to be exploited to produce extreme features that cannot be achieved using matrix powder technology. This material is the cornerstone that expands the design and manufacture windows for conventional PDC bit technologies.
Soft formations imply high penetration rates: the technologies developed are a novel hydraulic arrangement, bit face design, cutter size and usable diamond volume. Hard stringers require high stability in order to maintain bit life by preventing premature component failure. Technologies developed are conventional anti-whirl theory, localised cutter placement to extend bit life and an innovative low friction gauge pad that spans two blades and encloses a junkslot.
The case history demonstrates the significant performance improvement that can be achieved through interbedded formations by combining innovative PDC bit technologies. The study examines the development of the 12 1/4, section in the Tunu Field, Indonesia.
The continual development of the project is discussed including a lighter set variant to complete the same application and the successful translation of the design philosophy into a slimhole program.
P. 75
Barite Sag: Measurement, Modelling and Management
Authors: Bern P. A. , van Oort E. , Neusstadt B. , Ebeltoft H. , Zurdo C. , Zamora M. , Slater K. 
Published: December 2007

Abstract
A joint industry project was established to study barite sag mechanisms and to develop field guidelines to manage the consequences. A simple empirical model was developed to compare sag potential for a wide range of fluid types. In the study, physical properties of the mud, wellbore conditions, and characteristics of the weighting material were shown to have a large influence on sag behaviour. The study also included direct measurements of the properties of settled weight-material beds. These results provide new insight into the mechanisms of barite sag and how best to manage problems in the field.
Data from the tests clearly demonstrate that the parameters affecting sag are interrelated and seldom act in isolation. For all muds tested, the highest sag occurred at low annular velocities over angles from 60–75°. Drill-pipe rotation was particularly beneficial in minimising barite settlement. Rotation also assisted in re-distributing barite deposits formed on the low side of the hole.
The improved understanding of the mechanisms of barite sag enabled development of practical field guidelines. Case history studies presented in the paper demonstrate how the results of the work together with better field monitoring have been successfully applied to manage the effects of barite sag in HP/HT and extended-reach drilling operations.
Fatigue Life Evaluation: A Key to Avoid Drillpipe Failure Due to Die-marks
Authors: Hossain M.M. , Rahman M.K. , Rahman S.S. , Akgun F. , Kinzel Holger 
Published: December 2007

Abstract
Slips and tongs produce permanent marks on pipe body and tool joints. Such marks develop high stress concentration that reduces strength of pipes. The remaining strength of pipes often falls below the pipe stresses which can lead to tubular failure. Slim pipes are most susceptables to failure due to die- marks. In many instances, slim pipes are handled using double elevator system to reduce pipe failure. In this paper, results of a recent study of various die-mark related failures of drill pipes under different loading conditions, with particular emphasis on fatigue damage are presented. Stress concentration due to die-marks is characterised by finite element analyses as a function of mark sizes to cover various gripping systems available in the market. Then a methodology is presented for the prediction of failure due to cumulative fatigue damage. Effect of stress concentration arising from die-marks is taken into account in the analysis. Results of this study suggest that the effect of stress concentration on the cumulative fatigue damage may be significant depending on particular gripping system in use. In most cases, the fatigue life evaluation based on conventional assumption of smooth pipe surface is found to be very unsafe. Thus, a new approach is proposed in this paper for prediction of true safe life of marked drillpipes against fatigue failure. Fatigue damage results are presented in graphical forms. Calculation of cumulative fatigue damage of drillpipes used in a number of drilling events is then presented systematically in tabular form to assist drilling engineers in the evaluation of actual remaining fatigue life of drillpipes for the target drilling event using a particular gripping system.
P. 125
Addressing the Problem of PDC Bit Performance in Deep Shales
Authors: Smith John Rogers 
Published: December 2007

Abstract
Oil and gas wells that are drilled into deep, overpressured sediments frequently encounter slow penetration rates that result in high drilling costs. A cooperative effort between industry and university researchers has begun to study this problem and seek potential solutions. The current work has identified characteristics of the problem, its economic significance, its possible causes, and the best historical field practices for addressing it.
P. 261
Solving Casing Subsidence Problems with Downhole Activated Casing Slip Joints
Authors: Eriksen Eric Peter V. , Schwall Gene , Mahmoud Salah 
Published: December 2007

Abstract
Subsidence in chalk fields loads casing and liners with axial compression loads and results in uneven radial loading of the pipe wall. Eventually the casing or liner will fail from plastic collapse under the stress generated by the uneven radial loading combined with axial compressive load.
Casing Slip Joints placed in the compacting zones can reduce the combined stress in the cross sections thus increasing the stress level from uneven loading that can be tolerated.
Current designs require an activation load of 150,000 lbf. to initiate closing. The effect of a slip joint will be greatly improved if the Slip Joint is able to close when subjected to a small compressive load instead of the 150,000 lbf. currently required.
A system has successfully been developed that allows the Slip Joint to be run-in and cemented in its open position and yet be able to stroke freely after a preset time.
The system uses metallic shear screws that transmit a force equal to their full cross sectional shear strength when running- in. After a pre-set time their strength will be reduced to nearly zero through controlled stress corrosion cracking.
A number of materials were evaluated and one material was tested. The internal tensile stress required for the Stress Corrosion Cracking (SCUC) process can be adjusted to achieve a predetermined and predictable time to failure.
P. 277
Applications of Acid Fracturing Technique to improve Gas Production in Naturally Fractured Carbonate Formations, Veracruz Field, Mexico
Authors: Perex Daniel , Huidobro Efrain , Avendano Jose 
Published: December 2007

Abstract
This paper presents the results of successful applications of Acid Fracturing to increase gas production in mature carbonate fields in Mexico. Production comparisons show a substantial improvement in well performance following acid fracturing treatments. Six case studies are provided where a systematic methodology was employed to correctly determine candidates, and treatments. The methodology discusses the use of a novel technique that consist in alternating stages of acid and a non reactive fluid.
The fracture acidizing treatment technique, is designed to stop wormhole growth once growth has begun. The technique consists of initiating a fracture with a nonreactive pad of gel led fluid followed by alternating stages of alcoholic acid and nonreactive pad.
This system has been chosen to overcome two main problems, those are fracture extension and well cleanup.
This technique improves live acid penetration in a naturally fractured reservoir, thus sustaining greater and longer production increases than prior stimulation treatments.
The benefit obtained from the used of alcoholic acid as a reactive fluid in gas wells is observed during the initial production stages, when the well cleanup is rapidly achieved and gas production established.
Results of the treatments performed are discussed in details, including acid and gel volume, designs and analysis of the pressures recorded during placement, also data on load recovery times following the job are shown as wells as Prior and post fracture well analysis interpretations showing effective skin reduction and fracture length. Finally gas and condense production are presented including stability with time.
P. 285
Area-Specific Analysis Reflects Impact of New Generation Fluid Systems on Deepwater Exploration
Authors: Friedheim James E. 
Published: December 2007

Abstract
The worldwide acceleration in deepwater exploration and the accompanying technical and environmental complications have been well documented in the literature. From a drilling fluids perspective, the demands intrinsic to deepwater drilling and completions are especially acute as operators must reconcile performance and economic objectives with unique technical and environmental obstacles. Beyond standard fluid criteria, mud systems designed for deepwater projects must also address such unique problems as shallow gas hazards/water flows; gas hydrate formations; loss circulation/lower fracture gradients and hole cleaning in the riser section.
This paper reviews the latest developments in synthetic and water-based mud systems geared specifically for deepwater drilling and completions. The inherent advantages and disadvantages of the various systems will be reviewed. Moreover, to illustrate the technical and economic impact of latest generation fluid systems in deepwater projects, the author will present case studies from deepwater theaters worldwide.
A New Approach to Designing High-performance Lightweight Cement Slurries for Improved Zonal Isolation in Challenging Situations
Authors: Revil Philippe , Jain Bipin 
Published: December 2007

Abstract
A new approach to cementing allows the design of high- performance slurries at low as well as high densities. The technology decouples slurry and set cement performance from the slurry density. Using this technique new lightweight cement slurries as low as 10 PPG can be designed with high compressive strength, low permeability, and low porosity for applications such as completion in reservoirs with low fracture gradients, matched density kickoff plugs, geothermal wells, single slurry for both lead and tail, grouting jobs and many more.
The technology is based on the correct selection of components for the dry blend with compounds of proper specific gravity and in an optimum ratio. The subsequent reduction in usage of liquid for slurry preparation leads to beneficial effects on set cement properties.
The advantageous properties provided by the proposed system are:
– Very high compressive strengths of 2000 psi at 10.0 PPG and 4000 psi at 12.0 PPG, at low densities – Very low permeability and porosity of set cement – Improved stability, fluid-loss control and in most cases no free water compared to conventional systems – Excellent perforability for the set cement – Improved robustness to possible density fluctuations
In this paper the technology is presented and illustrated through a comprehensive set of laboratory data. Also, results are presented from various field applications where the technology has been used. Significant savings have resulted for the operator, especially when replacing conventional multistage operations with single-stage ones.
P. 339
Determination of Casing and Tubing Burst and Collapse Design Factors to Achieve Target Levels of Risk, Including Influence of Mill Source
Authors: Burres C. V. , Tallin A. G. , Cernocky E. P. 
Published: December 2007

Abstract
This paper provides examples of the opportunity for significant change away from historical burst and collapse design factors through the use of risk-based design. The roles of D/T ratio, grade, and mill source are accounted for in the determination of the design factor to use for a chosen target level of risk. The paper provides examples of what the burst and collapse design factors should be set to, in order to meet corresponding target levels of risk. The paper shows that the influence of grade and mill source can sometimes have significant impact on the pressure capacity of the pipe for a fixed risk of failure. The figures summarize the role that pipe parameters and service pressures play in setting the risk of failure.
Will Risk Based Casing Design Mean Safer Wells?
Authors: Hinton Andy 
Published: December 2007

Abstract
Although Working Stress Design is well understood, and has been used successfully, it does have drawbacks for industry. QRA / Risk Based Design are valid methods of designing casing. Full understanding of a new system is required by users and there is some concern about the validity of load data compared to resistance. Risk Based Design alone will not mean safer wells and it must be justified by being part of a total system which includes improved Quality Control and more accurate failure equations.
Probabilistic Well Design in Oman High Pressure Exploration Wells
Authors: Dahlin A. , Snaas J. , Norton S. 
Published: December 2007

Abstract
Historically, deep HPHT exploration wells in South Oman have been designed in a deterministic manner. In the design phase certain assumptions are made somewhat risk-averse, resulting in well designs catering for "worst-case" conditions. With hindsight this method, although proven to be sound, has resulted in over-designed wells.
The cost conscious Well Engineer, by better accounting for uncertainty, needs to minimise the over-design without risking the loss of pressure control and its possible effects on Health, Safety and Environment. It is evident that a careful balance needs to be found between risk and the level of over-design.
A novel approach to reducing the over-design is through applying a "Probabilistic Well Design" method. This method differs from the conventional design methods by defining a model in which the geological variables are defined in a probabilistic rather than a deterministic manner.
Once the model is described outcomes are simulated with statistical "Monte Carlo" software to calculate the distribution in the range of maximum design loads. Based on this distribution curve the Well Engineer can define the maximum safe operating limits of the well. The method results in a "fit for purpose" well design, with the clear understanding that if the worst case conditions (which have a low probability of occurring) are approached, some of the well objectives may not be achieved. If this should turn out to be the case the downside is that a subsequent well that does cater for these conditions is then required.
The technique has been successfully applied to two deep onshore HPHT wells during 1997 and is planned for two further wells in 1998. In the first application the technique resulted in a well, that if designed in the deterministic manner would have been drilled as a 15000psi well. After applying the probabilistic analysis it was determined that there was a 93% chance that the objectives could be met without the maximum surface pressure exceeding 10,000 psi. The well was drilled and all the objectives were met within the 10,000 psi design rating.
The probabilistic design technique is now applied to all the HPHT exploration wells and it is anticipated that it will result in considerable reductions in drilling costs in the future.