Relating 4D seismics to reservoir geomechanical changes using a discrete element approach     

Haitham Alassi  Rune Holt  Martin Landrø 《Geophysical Prospecting》2010,58(4):657-668

A modified discrete element method is briefly introduced and used for modelling reservoir geomechanical response during fluid injection and depletion. The modified approach works as a continuum method until some local failure is initiated, after which it behaves like a discrete element method on a polygonal lattice. The method is advantageous for modelling fracture developments in rocks. It is applied here to synthetic models of two reservoirs taken from the North Sea (Gullfaks and Elgin‐Franklin). For Gullfaks, two cases of water injection were modelled, one with low horizontal effective stress and the other with low vertical effective stress. Vertical fractures are developed in the first case, whereas horizontal fractures are developed in the second case. This would not have been seen using traditional methods. Based on 4D seismics data for the Gullfaks field, one may envision that horizontal fractures could have been formed. The Elgin‐Franklin synthetic model is used to study various scenarios of changing stress field around the depleting reservoir. Based on 4D seismics data from this field, one may see changes that could be interpreted in terms of possible fault reactivation.  相似文献   

Influence of subsurface injection on time‐lapse seismic: laboratory studies at seismic and ultrasonic frequencies          下载免费PDF全文

Dawid Szewczyk  Rune M. Holt  Andreas Bauer 《Geophysical Prospecting》2018,66(Z1):99-115

Seismic monitoring of reservoir and overburden performance during subsurface CO₂ storage plays a key role in ensuring efficiency and safety. Proper interpretation of monitoring data requires knowledge about the rock physical phenomena occurring in the subsurface formations. This work focuses on rock stiffness and elastic velocity changes of a shale overburden formation caused by both reservoir inflation induced stress changes and leakage of CO₂ into the overburden. In laboratory experiments, Pierre shale I core plugs were loaded along the stress path representative for the in situ stress changes experienced by caprock during reservoir inflation. Tests were carried out in a triaxial compaction cell combining three measurement techniques and permitting for determination of (i) ultrasonic velocities, (ii) quasistatic rock deformations, and (iii) dynamic elastic stiffness at seismic frequencies within a single test, which allowed to quantify effects of seismic dispersion. In addition, fluid substitution effects connected with possible CO₂ leakage into the caprock formation were modelled by the modified anisotropic Gassmann model. Results of this work indicate that (i) stress sensitivity of Pierre shale I is frequency dependent; (ii) reservoir inflation leads to the increase of the overburden Young's modulus and Poisson's ratio; (iii) in situ stress changes mostly affect the P‐wave velocities; (iv) small leakage of the CO₂ into the overburden may lead to the velocity changes, which are comparable with one associated with geomechanical influence; (v) non‐elastic effects increase stress sensitivity of an acoustic waves; (iv) and both geomechanical and fluid substitution effects would create significant time shifts, which should be detectable by time‐lapse seismic.  相似文献   

Late-glacial cirque glaciation in parts of western Norway     

Eiliv Larsen  John W. Attig  Asbjrn Rune Aa  Eivind Snstegaard 《第四纪科学杂志》1998,13(1):17-27

Younger Dryas cirque glaciers are known to have existed beyond the Scandinavian Ice Sheet in parts of western Norway. At Kråkenes, on the outermost coast, a cirque glacier formed and subsequently wasted away during the Younger Dryas. No glacier existed there during the Allerød. Large cirque moraines, some with marine deltas and associated fans, extend into the western part of Sykkylvsfjorden. Comparison with existing late-glacial sea-level curves shows that the uppermost marine sediment in these features was deposited well above Younger Dryas sea-level, demonstrating that the cirques were occupied by glaciers before the Younger Dryas. During the Younger Dryas the cirque glaciers expanded, and some advanced across the deltas, depositing till and supplying the sediment to form lower-level fans and deltas controlled by Younger Dryas sea level. The extent of the Younger Dryas advance of some of the glaciers was, at least in part, controlled by grounding on material deposited before the Younger Dryas. The depositional history of the glacial–marine deposits in the Sykkylven area indicates that cirque glaciers existed throughout Late-glacial time and only expanded during the Younger Dryas. The sediment sequence in glacial lakes beyond cirque moraines and reconstructions of glacier equilibrium lines indicate that this was true for most cirques in western Norway. Only on the outermost coast were new glaciers formed in response to Younger Dryas climate cooling. © 1998 John Wiley & Sons Ltd.  相似文献   

Green restructuring,innovation, and transitions in Norwegian industry: The role of economic geography     

Markus Steen  Rune Njøs 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(1):1-3

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Innovation networks and green restructuring: Which path development can EU Framework Programmes stimulate in Norway?     

Giuseppe Calignano  Rune Dahl Fitjar  Nina Hjertvikrem 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(1):65-78

ABSTRACT

With combined insights from evolutionary economic geography and transition studies, the article examines the engagement of different regions in Norway in the innovation networks created within the European Union’s environmental programmes. The aim is to explore the programmes’ potential for supporting green economy and economic restructuring through branching and new path creation. The authors assess which regions participate in the programmes, which international networks they build, and which organisations participate in different regions. They compare three regions with different restructuring needs and research capacity – the counties of Rogaland, Hordaland, and Sør-Trøndelag (now part of the county of Trøndelag). They find that overall, Norwegian organisations participate relatively frequently in the programmes, but private firms play a marginal role. Their partners are mainly in core EU regions. Regional participation in the programmes is a function of research capacity as well as oil dependence. The authors conclude that in research-oriented regions, research establishments tend to dominate participation, creating potential for restructuring mainly through path creation. In oil-dependent regions, private firms account for a higher share of participants, enhancing the potential for branching. As the former regions participate more, the programme can mainly stimulate path creation.  相似文献   

Polar amplification in a coupled climate model with locked albedo   总被引：1，自引：0，他引：1  

Rune Grand Graversen  Minghuai Wang 《Climate Dynamics》2009,33(5):629-643

In recent years, a substantial reduction of the sea ice in the Arctic has been observed. At the same time, the near-surface air in this region is warming at a rate almost twice as large as the global average—this phenomenon is known as the Arctic amplification. The role of the ice-albedo feedback for the Arctic amplification is still a matter of debate. Here the effect of the surface-albedo feedback (SAF) was studied using a coupled climate model CCSM3 from the National Center for Atmospheric Research. Experiments, where the SAF was suppressed by locking the surface albedo in the entire coupled model system, were conducted. The results reveal polar temperature amplification when this model, with suppressed albedo, is forced by a doubling of the atmospheric CO₂ content. Comparisons with variable albedo experiments show that SAF amplifies the surface-temperature response in the Arctic area by about 33%, whereas the corresponding value for the global-mean surface temperature is about 15%. Even though SAF is an important process underlying excessive warming at high latitudes, the Arctic amplification is only 15% larger in the variable than in the locked-albedo experiments. It is found that an increase of water vapour and total cloud cover lead to a greenhouse effect, which is larger in the Arctic than at lower latitudes. This is expected to explain a part of the Arctic surface–air-temperature amplification.  相似文献   

Control-Volume Discretization Method for Quadrilateral Grids with Faults and Local Refinements     

Ivar Aavatsmark  Edel Reiso  Rune Teigland 《Computational Geosciences》2001,5(1):1-23

This paper extends the multipoint flux-approximation (MPFA) control-volume method to quadrilateral grids for which the adjacent cells do not necessarily share corners. Examples are grids with faults and locally refined grids. This paper gives a derivation of the method for such grids. The difference between two-point flux-approximation (TPFA) results and MPFA results for faults and local grid refinements is demonstrated for synthetic problems. Further, the results are compared with results from uniform fine-grid simulations. The effect of repeated fault patterns as well as anisotropy is investigated. Large errors may be found for the TPFA method for flow through a series of faults in an anisotropic medium. Finally, a comparison is done for a reservoir field application.  相似文献   

Trace element composition and cathodoluminescence of kyanite and its petrogenetic implications     

Axel Müller  Alfons M. van den Kerkhof  Rune S. Selbekk  Maarten A. T. M. Broekmans 《Contributions to Mineralogy and Petrology》2016,171(8-9):70

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High-velocity migration of large earthquakes along the Azores-Iran plate boundary segment     

Klaus Meyer  Rune Olsson  Ota Kulhánek 《Pure and Applied Geophysics》1984,122(6):831-847

Between 1 January 1980 and 28 July 1981, a series of large earthquakes with body-wave magnitudes around 7, took place along the western segment of the Alpide belt. The sequence started in the Azores and migrated eastward along the belt at a rate of about 4400 km/yr with consecutive large events in northern Algeria, southern Italy, southern Greece and Iran. Two different methods are employed to identify similar series and corresponding migration velocities during earlier time periods of this century. The data set used contains all earthquakes with body-wave magnitudes larger than 6.3 and covers the time interval 1901–81. The concept of linear migration is tested for eastward and/or westward propagation, considering high migration velocities from 1600 to 11 000 km/yr. Results obtained are not homogeneous with respect to the two opposite migration directions, west-east and east-west, and we interpret this as a net drift of earthquake activity from the west to the east. Our efforts here are concentrated on analysis of observational data and on estabilishing the uniqueness of migration patterns. Because of the complexity of the tectonic system in question, we did not attempt to establish a mechanism explaining the migration of the observed earthquake sequences.  相似文献   

Analogies between electricity and mechanics with geophysical applications     

Rune Olsson 《Journal of Geodynamics》1986,5(3-4)

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