bluuebunny/crossref_metadata_2025_split huggingface dataset:
Static and Dynamic Compressibility of Deep Underground Caverns
Authors: Berest P. , Bergues J. , Brouard B. 
Published: December 2007

Abstract
Compressibility of deep fluids-filled cavern is discussed. Compressibility is measured both through statical and dynamical tests. Statical compressibility is influenced by cavern shape and cavern fluids nature. This parameter plays an important role for such applications as the determination of stored hydrocarbons volume, of volume lost during a blow-out, and of pressure build-up rate in a closed cavern. Dynamical compressibility is measured through the periods of waves triggered by pressure changes. Both tube waves and longer period waves associated to the existence of an interface between a liquid and a gas can be observed. They can provide additional information, for instance the existence of trapped gas in the well-head.
P. 105
A Comparison Of Leak-Off Test And Extended Leak-Off Test Data For Stress Estimation
Authors: Addis M.A. , Hanssen T.H. , Yassir N. , Willoughby D.R. , Enever J. 
Published: December 2007

Abstract
The principal function of leak-off tests is to assess casing integrity, but the test data are commonly used beyond this original purpose, for stress estimations in exploration and drilling. The value of leak-off test data for stress estimation is questionable and extended leak-off tests have been proposed as a more appropriate method for stress estimation. The paper for the first time compares leak-off test (LOT) and extended leak- off test (ELOT) data from two areas, the North West Self of Australia and the Norwegian North Sea. Standard LOTs have a characteristically large scatter associated with the leak-off pressures (Plo), minimum stress and fracture gradient estimates in both areas. However, the minimum stress determined from ELOTs are consistent and form a lower bound to the standard fl0 data in both areas. The ELOT takes about an hour to perform, but provides far superior data than that obtained from a LOT, and is recommended where stress data are required.
P. 131
Can Dipmeter logs be used to identify In-situ Stress Directions in the North Sea?
Authors: Fejerskov M. , Bratli R. 
Published: December 2007

Abstract
Analysing borehole breakouts is a well known method for obtaining horizontal stress directions. In this study dipmeter data from 46 wellbores in the Tampen area in the northern North Sea were analyzed for breakouts. The analysis identified a large problem of differentiating borehole breakouts from key- seats. Even at very low bole deviation elongations seemed to align with hole azimuth. This hampered breakout identification, and indicated that key seating possibly is a much larger problem than implied in earlier breakout work from the North Sea From our findings and also based on other stress data from the area it seems as though the wellbore very often deviates in the direction of the least horizontal stress, thereby masking breakouts as key seats. To examine this observation the effect of bedding and stress on the wellpath were examined, without yielding a solution to the problem. For future stress analyses in the northern North Sea enhanced use of imaging data will be important to avoid similar problems. Borehole breakouts identified by dipmeter analysis primarily seem to give an indication of the in-situ stress direction, as long as the number of observations are statistical significant. Traditional breakout analysis should not be trusted alone, but always be constrained by, for instance, image analysis.
P. 151
Constraining the State of Stress in Tectonically Active Settings
Authors: Plumb R. , Papanastasiou P. , Last N. 
Published: December 2007

Abstract
This paper describes the hierarchical approach used to characterize the regional state of stress in tectonically active settings. The example featured here is the Cusiana field where wellbore instability was a serious problem. The Cusiana field is located in the foothill of the Colombian Andes, South America. A key to solving the instability the was to identify what stress information was needed to improve drilling performance. Using drilling records, caliper logs, cavings samples, cores from the reservoir and a few meters of borehole image, an internally consistent working hypothesis of the state of stress was formulated, tested and refined. Simple calculations based on elastic-brittle model, confirmed also b, y drilling data, showed that the minimum principle stress is horizontal and the overburden was the intermediate stress. Elastoplastic modeling of borehole deformation in sands and shales based on core testing and finite element analysis placed tighter constraints on the relative principal stress magnitudes and the magnitude of the maximum horizontal stress.
P. 179
Flexurally-Induced Stresses in the Northern North Sea: Preliminary Comparison of Observation and Theory
Authors: Grollimund B. , Zoback M.D. , Arnesen L. 
Published: December 2007

Abstract
In this work we evaluate the role of lithospheric flexure resulting from post-glacial rebound as a possible source of regional stress variations in the northern North Sea. Compilations of leak-off and pore pressure data, estimates of the full stress tensor from observations of wellbore failure, and earthquake focal plane mechanisms indicate high horizontal compression (i.e., SHmax&gt;Sv and Shmin=Sv) on the west side of the Viking Graben and decreased horizontal stresses on the east side. In this study we extend the available knowledge about regional stress magnitudes by analysis of leak-off and pore pressure data. We use numerical modeling of lithospheric flexure due to post glacial rebound to show that this is a possible cause of the observed high horizontal compression in the Tampen Spur, regional stress variations and possibly the high pore pressures observed at depth west of the Viking Graben.
P. 189
The Shrinkage Rate of KCL-Exposed Smectitic North Sea Shale Simulated By a Diffusion Model
Authors: Bostrom B. , Svano G. , Horsrud P. , Askevold A. 
Published: December 2007

Abstract
Based on a containment transport model developed for hydrogeological purposes, a numerical method for the analysis of intrusion of potassium ions into a shale has been developed. The scheme has been applied in the back-analysis of KCl-brine exposed specimens of smectite-rich Tertiary Paleocene shale from the North Sea. The specimens, exposed under effective confining stresses in a triaxial cell at 80 C, shrank during the KCl-exposure. Two tests with different KCl concentrations (5wt% and 20wt%) have been back-analysed.
The ion transport is modelled by diffusion Using a finite difference scheme. In the back-analysis it was assumed that the observed shrinkage is due to the ion exchange when the bound Na+-ions are exchanged with K+-ions from the exposure fluid. The agreement between simulated and measured shrinkage rate was good, indicating that the assumed relation between ion transport, ion exchange and shale shrinkage is a valid mechanism.
The simulations showed tensile stresses near the specimen boundaries, where the shale first shrinks. A downhole situation was therefore analysed with a linear elastic model, and the development of tensile stresses with time was investigated. This linear elastic analysis showed that in the vicinity of the borehole wall, large tensile stresses develop as the front of the K+ ions progresses into the shale. Such tensile stresses may lead to the development of cracks and fissures, which in turn increases the surface area of the brine-exposed shale. An accelerating mechanism of cracking may thus develop, increasing the potential of destabilising the shale.
For each practical case there is thus an upper limit to the KCl-concentration which should be used in smectite-rich shale. Up to this limit, stability is improved due to a reduced stress concentration. Above this limit, stability problems will increase with increasing KCl-concentration.
P. 273
Laboratory Study of Permeability Evolution in a Tight' Sandstone under Non-Hydrostatic Stress Conditions
Authors: Keaney G.M.J. , Meredith P.G. , Murrell S.A.F. 
Published: December 2007

Abstract
Hydrostatic and triaxial compression experiments have been conducted to investigate the evolution of fluid permeability and fluid storage capacity in Tennessee sandstone, a low- porosity tight' reservoir sandstone. A newly developed single-ended transient pulse permeability measurement technique has been used for this study. Under hydrostatic stress, both permeability and specific storage are demonstrated to be dependent upon effective confining pressure. The evolution of axial permeability as a function of increasing compressive deviatoric axal sttess has been investigated in triaxial compression experiments. All samples were deformed within the brittle faulting regime. Both permeability and specfic storage decrease during compaction, and subsequently increase when axially-aligned dilatant microcracking becomes dominant. Brittle failure is sometimes accompanied by a transient increase in permeability by as much as 1.5 orders of magnitude. Following brittle failure the permeability is controlled by the properties of the fault rock. Permeability decreases as stable sliding occurs on the fault up to large axial strains, such that the fault may act as an impermeable seal to migrating fluids.
P. 329
Reservoir Compaction and Seafloor Subsidence at Valhall
Authors: Pattillo P.D. , Kristiansen T.G. , Sund G.V. , Kjelstadli R.M. 
Published: December 2007

Abstract
The combination of in situ effective stress and reservoir chalk mechanical weakness in the Valhall field has resulted in compaction and associated subsidence at the mudline. This paper summarizes recent finite element modeling of this phenomenon, emphasizing items of concern in a numerical simulation of this nature. The paper also presents new results from a simulation allowing inelastic overburden response.
P. 377
Integrated Borehole Stability Analysis - Against Tradition
Authors: Zheng Z. 
Published: December 2007

Abstract
Technological advances in drilling equipment, directional control and mud systems and a better understanding of reservoir properties have resulted in the drilling of an increasing number of highly deviated and horizontal wells. Along with these wells come the increasing borehole instability and sand production potentials under normal in-situ stress conditions (when the stresses are vertical and horizontal, with vertical greater than both horizontal stresses). Conventional guidelines for horizontal well design have been to drill in the direction parallel to the minimum principal stress, which reduces the difference between the principal stresses perpendicular to the borehole, and results in a minimum stress concentration around the borehole. Such guidelines are based on an effort to reduce the required borehole pressure to maintain zero breakout.
Research on borehole breakout and borehole stability in the past fifteen years has shown that a stable breakout is characterized by a stress distribution which transfers the high stress concentration from the opening to the zone near the tip of the breakout, and causes a quasi-hydrostatic stress state in that zone. Breakout geometry is therefore more stable than circular geometry. Recent experimental studies on utilizing breakout geometry to enhance tunnel stability have also shown that breakout geometry has a much greater "excavation strength" than circular geometry under the same stress configurations. Breakout geometry provides a "self-supportive" function that allows a smaller degree of failure potential around the borehole than other excavation geometries.
Fundamental stability mechanisms for stable breakout are revisited and the feasibility of drilling parallel to the intermediate principal stress direction under stable conditions investigated through numerical simulations. The results show that under most in-situ conditions, drilling in the intermediate principal stress direction and allowing some degree of breakout affords tmproved stability during drilling and subsequent production, provided that the breakout generated failure materials can be removed efficiently. The mud weight required to maintain stability is substantially less for this type of borehole configuration that leads to reduced formation damages, and allows for the generation of a single hydraulic fracture parallel to the borehole rather than multiple fractures perpendicular to the borehole (assuming it is drilled in the direction of the minimum principal stress). The cost savings and possible production enhancement derived from such drilling practices could result in a dramatic economic impact on the petroleum industry.
P. 395
Reservoir Compaction, Surface Subsidence, and Casing Damage: A Geomechanics Approach to Mitigation and Reservoir Management
Authors: Fredrick J.T. , Deitrick G.L. , Arguello J.G. , DeRouffignac E.P. 
Published: December 2007

Abstract
Geologic, and historical well failure, production, and injection data were analyzed to guide development of three-dimensional geomechanical models of the Belridge Diatomite Field, California. The central premise of the numerical simulations is that spatial gradients in pore pressure induced by production and injection in a low permeability reservoir may perturb the local stresses and cause subsurface deformation sufficient to result in well failure. Time-dependent reservoir pressure fields that were calculated from three-dimensional finite difference reservoir simulations were input into three-dimensional nonlinear finite element geomechanical simulations. The reservoir models included nearly 100,000 gridblocks (100-200 wells), and covered nearly 20 years of production and injection. The geomechanical models were meshed from structure maps and contained more than 300,000 nodal points. Shear strain localization along weak bedding planes that causes casing dog-legs in the field was accommodated in the model by contact surfaces located immediately above the reservoir and at two locations in the overburden. The geomechanical simulations are partially validated by comparison of the predicted surface subsidence with field measurements, and by comparison of predicted deformation with observed casing damage. Further, simulations performed for two independently developed areas at South Belridge, Sections 33 and 29, corroborate their different well failure histories. The simulations suggest the three types of casing damage observed, and show that although water injection has mitigated surface subsidence, it can, under some circumstances, increase the lateral gradients in effective stress, that in turn can accelerate subsurface horizontal motions. Geomechanical simulation is an important reservoir management tool that can be used to identify optimal operating policies to mitigate casing damage for existing field developments, and also applied to incorporate the effect of well failure potential in economic analyses of alternative infilling plans and operating strategies.
P. 403
Three History Cases of Rock Mechanics related Stuck Pipes while drilling Extended Reach wells in North Sea.
Authors: Charlez P.A. , Onaisi A. 
Published: December 2007

Abstract
Stuck pipes have three different origins : hole geometry (excessive dog legs in highly deviated wells), pack off (wellbore instability or bad hole cleaning leading to a plugging of the annulus) and differential sticking (drill string embedded into the mud cake due to an excessive difference between mud weight and reservoir pressure). This paper presents three different examples of stuck pipes directly related to rock mechanics problems.
The first one results from a typical pack off in a highly unstable under compacted shale formation drilled in under balanced conditions.
The second stuck pipe is quite untypical since it occurred while drilling a 9 5/8 cemented shoe track. Finally, the third one occurred while drilling the reservoir section of a highly deviated well (720 inclination) and during a directional survey. The analysis of the surface data clearly showed that differential sticking was the cause of the stuck pipe.
In the three cases, the well had to be side tracked where each time the cost was in the range of 1M.
P. 423
Seismic Wave Propagation in Fractured Rock
Authors: Myer L.R. , Pyrak-Nolte L.J. , Yi W. 
Published: December 2007

Abstract
Azimuthal variation in shear wave speed and existence of two shear wave arrivals are commonly assumed to be diagnostic of fractured rock. These properties derive from a representation of fractured rock as an effective anisotropic medium. Work on effects of single fractures suggests that energy can be partitioned in ways that are not captured by the effective medium representation. Single fractures cause frequency dependent reflections, refractions and group time delays in plane waves and can trap energy as interface waves. These effects can result in distinctive seismic signatures in multiply fractured rock.
P. 211
New Technology For Conversion Of Coal To Pipeline Gas
Authors: Detman Roger 
Published: December 2007

This paper was prepared for the Second Midwest Oil and Gas Industry Symposium of the Society of Petroleum Engineers of AIME, to be held in Indianapolis, Ind., March 28–29, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
The new technology for conversion of coal to pipeline gas being developed in the joint Government-Industry program is described. Status of the pilot plant operations is covered along with plans for evaluation and selection of a process for full scale demonstration. Concepts process for full scale demonstration. Concepts of commercial reactors are described along with the major problems in converting the new technology to industrial plants.
PRESENTATION PRESENTATION The nation has become acutely aware of the shortage of domestic sources of oil and natural gas. This has come about as a result of the sudden loss of crude oil from the middle East. However we do not import natural gas from the Middle East. The natural gas shortage was a growing problem for many years before the Middle East crisis. As a result of the oil embargo, the gas problem has become more acute and the urgency of developing new sources of gas has become a critical problem almost overnight. The impending problem of a gas shortage was recognized by some back in the 1950's and work was started at that time to develop processes to convert coal into pipeline gas. In 1960 the office of Coal Research was established in the Department of the Interior to direct the Government's efforts. Research to develop new processes was underway in the 60's in several processes was underway in the 60's in several organizations. These included the Bureau of Mines, Bituminous Coal Research, the Consolidation Coal Company, the Institute of Gas Technology, the Food Machinery Corporation, and others.
By 1970 several new processing concepts had been developed in the laboratories and two of these had reached the stage of pilot plant design. In 1970 a joint Government-Industry program was organized to accelerate the program was organized to accelerate the development of processes for converting coal to pipeline gas. The agreement between the pipeline gas. The agreement between the American Gas Association and the Government's office of Coal Research was for a four year program to develop promising new processes program to develop promising new processes through the pilot plant stage.
Possibilities of Energy Recovery from CO2 Reservoirs
Authors: Popp V.V. , Marinescu M. , Manoiu D. , Popp A. , Chitu P.M. 
Published: December 2007

Abstract
The paper presents the results of the investigations regarding thoe geothermal exploitation of CO2 reservoirs and the limited efficiency of the process.
For gas with a hydrocarbon content between 10% mol. and 55% mol., a process consisting of the catalytic burning of hydrocarbons energy recovery and CO2 injection into reservoirs is described..
P. 33
Scale Effects on Fracture Growth Resistance in Poroelastic Materials
Authors: Shlyapobersky Jacob , Issa Mohsen A. , Issa Mahmud A. , Islam MD.S. , Dudley John W. , Shulkin Yuiri , Chudnovsky Alexander 
Published: December 2007

Abstract
The size effect in brittle fracture of rock-type materials is studied by conducting a comprehensive experimental program with concrete specimens of different sizes from materials with different aggregates. Fracture behavior in single edge notched specimens subjected to forces, splitting and compressive along the plane, under displacement control conditions is observed. Based on experimental data and numerical analysis, the stress intensity factor and energy release rate, KIC and GIC, are obtained at the onset and in the course of crack growth. It is established that:the fracture toughness to crack initiation weakly increases with increase in specimen and aggregate sizes;the toughness significantly increases with fracture length.
These trends are attributed interaction of crack surfaces (aggregate interlock effect) due to the presence of compressive force along the crack plane. A model of the interlock effect is discussed.
P. 29
Artificial Lift Design for the Deepwater Gulf of Mexico
Authors: Stair Craig D. 
Published: December 2007

Abstract
Artificial lift could significantly increase ultimate recovery from deepwater Gulf of Mexico (GOM) reservoirs, but the extreme application will present unique challenges to conventional artificial lift designs. This paper presents an exploration of feasibility and operability issues for both gaslift and Electric Submersible Pump (ESP) usage in direct vertical access wells in the deepwater GOM.
System and equipment considerations for gaslift and ESP design specific to the typical deepwater GOM application are discussed. Either system will work in this application, but they will both push current technology to the limit. The incremental recovery associated with either system is shown to be largely a function of the producing gas-liquid ratio.
A description of the creation and interpretation of outflow curves for the two types of artificial lift is also included. Outflow curves are an important element in the simulation of well deliverability and reservoir performance over time. Proper use of these curves and an understanding of the curve limits are necessary to perform a valid simulation.
P. 43