bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Numerical Analysis of Strain Localization In Two Rock Materials
Authors: Diouta N. G. , Haied A. , Kondo D. , Shao J. F. 
Published: December 2007

Abstract
The theoretical framework of strain localization is summarized. Two kinds of material are studied: an overconsolidated clay and a sandstone. In the case of the oveiconsolidated clay which is contractant, non-associativity of a plastic flow (Khan's model) is found to be sufficient for the detection of the localization in the hardening regime. But for a strong dilatant material such as Fontainebleau sandstone, the non-associativity is no longer sufficient. Non coaxial flow theory needs to be added to the constitutive law to have bifurcation consistent with data provided by careful experiments.
A solution to wave propagation in randomly heterogeneous media: The 3-D analogue of the 1-D reflectivity sequence
Authors: Leary P. C. 
Published: December 2007

Abstract
Measurement of seismic structure at scales below «20m (the resolution limit of surfacegenerated seismic waves) requires borehole seismic sources and receivers. For borehole seismic data analysis, typical seismic imaging using plane wave propagation in 1-D layering must be supplanted by spherical wave propagation in 3 dimensions. Images of production fronts and discrete rock units must be sought as coherent scattering in a background of incoherent scattering by random discontinuities. The spectrum of scattered waves measures the density and size of the velocity fluctuations; as velocity fluctuations are often due to changing porosity and fracture density, broadband borehole seismic scattering spectra can characterize these features of reservoir volumes in the sub-metre to multi-metre range.
Steady and Unsteady State Two-Phase Flow Through Vertical Flow Strings
Authors: Gould T.L. , Tek M.R. 
Published: December 2007

Abstract
A numerical simulation for vertical multiphase systems has been developed, based on the original concepts presented by J. Orkiszewski. The rather marked variability for different flow regimes in a given well and the simultaneous coexistence of these various regimes at different depths are properly accounted for in the interative calculation of the pressure distributions. The method features the most reliable and proven correlations available for each of the flow regimes encountered. A programmed data package in support of the above correlations is described.
The concept of "Lifting Potential" introduced in an earlier paper has been programmed, permitting applications in programmed, permitting applications in a variety of multiphase flow problems. These include both steady and unsteady state applications. In general, the applications involve the study of "heading," "loading," "unloading," and "dying" of gas wells subject to liquid production, as well as different well production, as well as different well engineering and design optimization problems encountered in gas-lift and problems encountered in gas-lift and condensate production.
Introduction
The occurrence of two-phase flow in vertical flow systems is common to many engineering applications. Problems ranging from oil field technology to boiler design, from nuclear reactors fluidized beds, from special heat exchangers to thermosiphon reboilers frequently encounter conditions of multiphase flow.
The main problem of engineering interest in vertical two-phase flow may be defined as follows: Knowing the physical properties of each phase, physical properties of each phase, geometry of the flow system and conditions prevailing at one terminus to predict the pressure distribution along predict the pressure distribution along the pipe.
The literature available on vertical two-phase flow includes a large variety of correlations, analytical and empirical methods developed for prediction of energy losses as well as the flow regimes. It is significant to note that the references quoted above belong to two notably different schools of thought. The first group of papers, references 1 through a correlate friction losses by a unique energy loss factor without any particular regard to "slippage." particular regard to "slippage."
Rock failure mechanisms identification: A key for wellbore stability and reservoir behaviour problem
Authors: Maury V. 
Published: December 2007

Abstract
Generally several deformation and rupture mechanisms are involved in the problems of wellbore stability and reservoir behaviour. Adequate prognosis of the main mechanism responsible for an unexpected behaviour is a fundamental step in proposing a remedy which sometimes may be unusual or not conform to common practice but which has proven to be successful in several applications. This paper reviews and recalls some basic mechanism of wellbore instability until present overlooked and their practical consequences on the remedy to the problem. Another illustration is given by the various mechanisms involved in the reservoir behaviour of highly compactable material and the necessary evaluation of mechanisms involved for the prediction of significant movements.
Finite element modelling of shear band localisation and application to rock cutting by a PDC tool
Authors: Pierry Joélle , Charlier Robert 
Published: December 2007

Abstract
Several simulations of rock cutting at great depth by a single PDC cutter were carried out using the finite element method. They proved of great help in understanding the failure mechanisms inside the rock that are determinant for cutting efficiency. Shear bands, i.e. weaker regions along which a chip will develop, are successfully detected and localised using two different criteria, including an original one based on the evolution of strains during the cutting process. As classical finite element meshes lock the actual progression of shear bands, remeshing techniques are developed and applied so as to model the effective formation of chips into the rock. Automation of the different steps will result in a very useful numerical tool for optimisation in well-boring.
Borehole stability in shales: A constitutive model for the mechanical and chemical effects of drilling fluid invasion
Authors: Wong S. W. , Heidug W. K. 
Published: December 2007

Abstract
The density of the drilling fluid and its chemical composition are the main operational parameters controlling the stability of wellbores drilled in shales. To quantify their impact on the stress evolution around wellbores in pervious shales, we have developed a model that accounts for the physico-chemical interaction between the invading drilling fluid and a shale formation. The model is based on the principles of non-equilibrium thermodynamics and provides generalisations of Biot's classical poro-elastic theory and Darcy's flow equation. We demonstrate that our model can reproduce the salient features of experimental work on the fluid/shale interaction and use a finite-element scheme to numerically calculate the stress and strain distribution around a wellbore when interactions occur. We show that these effects promote tensile failure of the wellbore wall.
Time Dependent Borehole Stability: Laboratory Studies and Numerical Simulation of Different Mechanisms in Shale
Authors: Horsrud Per , Holt Rune M. , Sonstebo Eyvind F. , Svano Geir , Bostrom Bard 
Published: December 2007

ABSTRACT
Experimental work and numerical modelling have been applied to study mechanisms related to time dependent borehole stability during drilling in shales. Fully coupled numerical modelling showed that consolidation effects may act on a time scale of days, due to the low permeabilities of shale. Creep testing of a North Sea Tertiary shale showed that above 80% of the failure stress, the observed strain rates indicated that delayed borehole failure could occur within a period of 15 days. When exposing outcrop shale with close to zero swelling clay content to non-native fluids, substantial changes in mechanical properties were observed. Elevated temperature (80°C) also seemed to cause a weakening both in static and dynamic properties.
Sand Production in Vertical and Horizontal Wells in a Friable Sandstone Formation, North Sea
Authors: Ramos G. G. , Katahara K. W. , Gray J. D. , Knox D. J. W. 
Published: December 2007

ABSTRACT
Sand production is detrimental in oil and gas production. Sand-control measures include gravel-packing, drawdown control, sand consolidation, slotted liners, pre-packed screens, and frac-and-pack. Vertical wells can use any of these methods. Extended-reach, highly inclined wells, and horizontal wells close to water tables have very few cost-effective choices like slotted liners and open-holes. To predict the potential for sand production, a perforated completion was analyzed as an elastic-plastic spherical cavity while an open-hole horizontal well was analyzed assuming cylindrical symmetry. This analytical procedure was applied to investigate the feasibility of sand-free oil production from a friable sandstone formation in the North Sea. The calculated sand-free drawdown pressure of the horizontal well is more than twice that of the vertical-perforated well, depending on the drainage radius. Subsequently, in the North Sea single-well production test, a horizontal well was drilled and supported with a slotted liner only. The field test produced oil at high rates with no measurable amounts of formation sand.
Observations of Sand Production and Perforation Cleanup in a Weak Sandstone
Authors: Tronvoll Johan , Halleck Phillip M. 
Published: December 2007

ABSTRACT
Model experiments of sand production in a perforated sample of a weak outcrop sandstone are compared to tests on drilled cavities in the same rock. The perforation tunnel was filled with rock debris and a damaged zone occurred around it. Limited sand production resulted due to erosion of the rock debris, while instability of the perforation wall by formation of breakouts occurred at stress levels comparable to the failure stress of a drilled cavity. The failed material remained stable throughout the test, and most of the sand produced originated in the debris in the center of the perforation tunnel.
Wellbore Stability of a Superdeep Borehole in Crystalline Rock The KTB-Hauptbohrung, Germany
Authors: Hoffers Bernhard , Engeser Bernhard , Rischmüller Heinrich 
Published: December 2007

ABSTRACT
The borehole stability of the KTB-Hauptbohrung in Windischeschenbach, Bavaria, Germany, with its target depth of 10 km is described down to the depth of 8,715 m. The well is drilled from surface in crystalline rock, mostly gneisses and amphibolites. The types of wellbore instabilities observed so far (breakouts, washout zones, undergauge sections) as well as their causes (lithology, tectonics, in situ-stresses, miid properties) are discussed. The operational impact of the instabilities (changes in mud system, increase in mud weight, vertical drilling strategy, sidetracks) and the countermeasures taken are elaborated.
Modeling of Gas-Driven Fracture Propagation for Oil and Gas Well Stimulation
Authors: Petitjean L. , Couët B. 
Published: December 2007

Abstract
We present a model that can describe the propagation of a fracture driven by either a liquid or a gas. This model can be applied to situations in which the wellbore pressure is significantly higher than the in-situ stress, resulting in high fracture propagation speed and turbulent fluid flow within the fracture. We present results of test problems, where analytical and/or numerical solutions are available. Finally, we have applied our model to simulate field operations where the formation is dynamically fractured, as in extreme overbalanced operations. We compare results of fractures that are gas-or liquid-driven.
Prediction of Fracture Density and Drainage Distance in Layered Rock Masses Using Borehole Data
Authors: Wu Haiqing , Willemse Emanuel J. M. , Pollard David D. 
Published: December 2007

Abstract
We present a simple method to estimate fracture density and drainage distance from borehole data. The method is suitable for boreholes parallel to bedding and is based on the knowledge of fracture spacing observed in both outcrops and experimentally modeled fracture patterns. The method is relevant to long term well behavior as it identifies intervals of high fracture density that also have a long fracture drainage distance. To evaluate the method, the two-dimensional (2D) characteristics of known fracture patterns were compared with the ID data obtained from simulated wells bored through these fracture patterns.
Subsidence Induced Casing Deformation Mechanisms in the Ekofisk Field
Authors: Schwall G. H. , Denney C. A. 
Published: December 2007

Abstract
Casing deformation as a consequence of reservoir compaction and surface subsidence has occurred in the Ekofisk Field. Casing deformation database results show that reservoir deformations occur throughout the field, while overburden deformations occur primarily on the field flanks. Deformation geometry shows compressive loading of casings in the reservoir resulting in axial buckling. In the overburden, deformation geometry suggests formation movement along near horizontal features. Identification of the deformation mechanisms will be used to refine mitigative techniques which minimize casing loading, thus enhancing well life.
Improved Subsidence Monitoring Methods
Authors: Fourmaintraux D. M. , Flouzat M. , Bouteca M. J. , Kasser M. 
Published: December 2007

Abstract
The Differential Global Positioning System (DGPS) has been adapted to the oil industry by the CEA with EAP. It allows a continuous, accurate (+ or – 3 mm) and quasi-automatic monitoring of the subsidence above hydrocarbones field. The method is detailled and a simple case study explains how accurate subsidence data are able to precise the drainage pattern and help the production managment. The Airbom Laser System to measure subsidence developed with IGN is now at experimental stage. Monitoring a great number of points, it will be suited to onshore fields and allow to map the subsidence and the drainage pattern changes.
Computerised Prediction of Subsidence Over Oil and Gas Fields
Authors: Reddish D. J. , Yao X. L. , Waller M. D. 
Published: December 2007

Abstract
This paper presents the development of the theory and of a computer program to predict subsidence and horizontal displacement due to oil and gas withdrawal. Geertsma's nucleus of strain model has been modified and combined with an influence function program, developed for the prediction of mining subsidence, to form a new technique for the prediction of ground movements over oil and gas fields. The modifications and the influence function theory are described in detail, with particular emphasis being placed on the applicability of the developed theory to computer prediction. The influence function method allows complex reservoir geometry to be taken into account and both subsidence and associated horizontal ground movements may be calculated.
The Potential for Monitoring the Progress of Production Fronts Across Hydrocarbon Reservoirs
Authors: Crampin Stuart , Taylor David B. 
Published: December 2007

Abstract
Recovering more oil from a reservoir depends on obtaining a better understanding of the fluid/fluid and fluid/rock interactions over u wide range of scale lengths. Recent advances in understanding and modelling the behaviour of cracked and porous rock and developments in seismic instrumentation open the possibility of monitoring the movement of production and IOR fronts and interpreting the behaviour in terms of crack physics. Prototype strings of three-component broadband receivers and sources are designed to pass down production tubing into the reservoir, where seismic resolution is at least an order of magnitude better than in conventional techniques.
Numerical Simulation of Ekofisk Reservoir Compaction and Subsidence: Treating the Mechanical Behavior of the Overburden and Reservoir
Authors: Chin L. Y. , Boade R. R. , Nagel N. B. , Landa G. H. 
Published: December 2007

Abstract
Three aspects of reservoir compaction/subsidence simulation for Ekofisk are addressed: (i) stress paths in the reservoir during depletion, (ii) impact of porosity heterogeneities in reservoir chalk on scaling laboratory compaction data to field behavior, and (iii) methods for treating the behavior of the overburden in a finite element simulator. Specially created finite element models were used for the first two issues. Results indicate that geometry has a major impact on stress path. Results of the scaling analysis indicate that porosity heterogeneities cause a block of chalk comprised of numerous cells with different porosities to appear strong when internal shear failure is not allowed, but to appear weak when it is allowed. The discussion of the overburden behavior concentrates on field observations, interpretations of these observations, and methods used to represent them in a simulator.
Mechanical Testing and Permeability Measurements of Reservoir Chalk Under True Triaxial Stress Conditions
Authors: Christensen Helle F. , Foged Niels 
Published: December 2007

Abstract
A newly developed specialized true triaxial cell for rock mechanical testing is described. The cell allows testing of 46 X 46 x 110 mm box shaped specimens under in-situ reservoir stress conditions. The operating effective stress is up to 100 MPa [14500 psi] in the vertical direction and 50 MPa (7250 psi) in the horizontal direction. The applied stresses may be varied independently in 3 orthogonal directions (true triaxial stress condition) and both the vertical and the 2 horizontal absolute permeabilities are measured. The application of the true triaxial cell is illustrated by 3 selected tests.
Open Hole Stress Tests in Shales
Authors: Thiercelin M. , Desroches J. , Kurkjian A. 
Published: December 2007

Abstract
This paper presents a series of stress tests which have been performed in shales using a wireline stress tool which includes a downhole pump. It is shown that the best technique to carry out stress tests in these weak rocks is to use a combination of sleeve fracturing and hydraulic fracturing. An inversion of the pressure response during propagation and closure of the fractures is presented leading to the estimation of the in-situ minimum stress and various rock properties.
Hydraulic Fracturing and Microseismicity: Background and Recent Developments
Authors: Deflandre J. -P. , Sarda J. -P. 
Published: December 2007

Abstract
Hydraulic fracturing generates acoustic emissions. Laboratory works, field experiments and theoretical analysis progressively improved the understanding of the source mechanisms. The direction of the source, its distance from the recording station and even its size can be derived from advanced analyses of the acoustic signals: polarization analysis and analysis of the signal spectrum. New types of sondes and softwares help improving such analyses and lead to envisage their use as reservoir monitoring tools.
Logistical and Drilling Considerations Associated with Sulphur Exploration in High Arctic
Authors: Marshall D.J.B. , Crain E.R. 
Published: December 2007

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
During 1969, a stratigraphic test hole program was conducted on Melville Island in program was conducted on Melville Island in the Canadian Arctic. The purpose of the program was to explore for sulphur bearing program was to explore for sulphur bearing limestone caprock associated with salt domes. Two track-mounted seismic style drilling rigs were used to drill thirty-six holes to a maximum depth of 1000 feet.
In such a remote location and difficult environment, many transportation and support services were necessary that would not normally be required. Hercules type freighter aircraft were found to be the most efficient means of transporting exploration equipment into the Islands. Conventional tracked vehicles were quite suitable for surface transportation of the drilling equipment. Both a helicopter and a mixed wing aircraft were needed for personnel movements on and between the Islands.
Drilling in a permafrost environment presented unique problems which have not been presented unique problems which have not been extensively covered in the literature. The selection of the proper drilling fluid appears to be the most important consideration in planning a drilling program in permafrost areas. planning a drilling program in permafrost areas. Contrary to many widely publicized opinions, it does not appear that human or industrial activity has a serious or lasting effect on the ecology of the area.

Introduction
In July of 1968, King Resources Company secured sulphur exploration permits covering approximately 880,000 acres in the Arctic Islands from the Canadian Federal Government. These permits were obtained after geological studies indicated an abundance of salt domes in the Sverdrup Basin which is centered in the Canadian Arctic. This basin bears a marked resemblance to the Gulf Coast Basin in that both contain large thicknesses of Mesozoic sediments and both have intrusive salt domes. The target in this venture was to find sulphur in limestone caprock associated with these domes. Preliminary economic studies were conducted which indicated that if sulphur reserves of the order of 20 million tons could be discovered at depths suitable for normal Frasch mining, the sulphur would be competitive on the world market.
Early in 1969, planning began for an exploration program.
A New Wellsite Information System To Aid the Drilling Process
Authors: Grenadier J. A. , McCann Dominic , Koch Steve 
Published: December 2007

Abstract
The IDEAL1 Wellsite Information System acquires data to monitor the drilling process. It interprets the realtime data flow from both surface and downhole and displays useful information on high resolution color screens to the key decision makers on and off the wellsite.
The IDEAL Wellsite Information System can support four classes of users simultaneously: The driller, the directional driller on the rig floor, logging specialists in the unit and the company representative in the customer's office. Color displays have been customized to the specialized needs of each class of user. In particular, the IDEAL Driller's Display is a pressurized unit located on the rig floor. The driller can select from a number of screens with a minimum number of keystrokes.
This information network improves drilling efficiency, geological evaluation and subsequent production through enhanced geological steering.
Data is continually stored in both the time and depth domains. These databases can be exported into a variety of formats. Data can also be transmitted in realtime to the customer's office offsite.
Backup system components allow for redundancy so that system downtime is virtually eliminated.
By having system developers concentrate on making the workstation easy to operate, the users can focus on the drilling process and not on the computer system. Custom graphic displays were designed by drillers for drillers. "Smart Alarms" have been designed to alert the user of potential problems such as kicks, sticking pipe and drillpipe washout.