Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
ABSTRACT: A number of underground gas storage caverns are being developed in water-saturated rock masses, relying on water pressures to provide containment. However, the gas-water contact in fractured rock is quantitatively different from conventional continuum assumptions. This paper describes the development of an approach for analyses of gas storage effectiveness based on discrete fracture network modeling. Discrete fracture geometries are modeled directly, and all flow occurs within the planar fracture features, although there can be interaction between fractures and the intact rock surrounding them. RÉSUMÉ: Uncertain nombre de reservoirs souterrians d' entreposage de gaz sont creuses à même las masses de roc sature en se basant sur la pression hydraulique comme mode de confinement. Cependant, Ie contact entre I' eau et Ie gaz dans Ie roc fracture est quantitativement different des hypothèses conventionnelles s'appliquant aux milieux continus. Cet article decrit Ie developpement d'une approche pour l'analyse de I'efficacite d'entreposage de gaz sur la base de la modelisation du reseau de fractures discretes. Les geometries de fractures discrètes sont modelisees directement et la totalite de I' ecoulement se produit au sein des elements de fractures planaires, bien qu'il puisse exister une interaction entre les fractures et le roc intact avoisiant. ZUSAMMENFASSUNG: Zur Zeit werden eine Anzahl von Untertage gas speicherkavernen gebaut, die sich in wassergesattigten Felsmassen befinden. Da der Wasserdrueck dem Gasdrueck entgegenwirkt, ergibt sich eiue gasdichte Kaverne. Jedoch verhalt sich der Gas-wasserkontakt im gekluefteten Fels quantitativ verschieden im Vergleich zum allgemein angenommenen Kontinuum. Diese Arbeit befaβt sich mit der Entwicklung eines Verfarens Zur Analyse der Gasspeicherueng, die auf der diskreten Kluftnetz modellieung aufgebaut ist. Diskrete Kluffgeometrien werden dabei direkt modelliert und die gesarnute Strömung verlauft zwischen ebenen kluftflachen. Eine Zusaumenwirkung der Kluefte mit dem Festgestein kam ebenfalls im Rechenmodell beruecksichtigt werden. 1. OVERVIEW Underground gas storage in unlined caverns depends on overpressures in surrounding rocks to maintain gas containment (Gustafson et al, 1989). In a conventional porous medium, the water pressures in the rock can be defined by a continuous field, and the gas-water contact is smooth and continuous, as illustrated in Figure 1. However, in a fractured rock, the water overpressure in fractures may vary from fracture to fracture. In addition, the aperture distribution by fracture varies. This can cause a variation in the gas penetration among adjacent fractures. The extent of gas penetration can be evaluated using a discrete Fracture model such as FracMan (Dershowitz et al, 1994). 2. MATHEMATICAL DEVELOPMENT Goodall et al (1988) established the criterion for gas containment in unlined rock caverns that gas cannot leak from unlined caverns in which water pressures increase in some portion of every path away from the cavern. 3. FRACTURE NETWORK SIMULATION The calculation of the probability of occurrence of a critical fracture Network, Nc, can be carried out using the well established procedures of discrete fracture simulation and pathways analysis (see, for example, Dershowitz and Roberds, 1990).The key stages of this analysis are: definition of geometries for source (cavern) and sinks (low pressure borehole, cavern, aquifer, etc.) derivation of geometric and hydrologic parameters for fracture network populations from fracture data. These parameters include orientation, size, shape, transmissivity, and location distributions. These parameters can be derived from field data using procedures described in. for example, Dershowitz (1992). Monte Carlo simulation of fracture geometries consistent with the statistics derived from fracture data. conditioning of Monte Carlo simulations to observed intersections with boreholes and caverns (Uchida et al, 1994).
- Europe (0.70)
- North America > United States (0.47)
ABSTRACT: This paper is mainly concerned with the influence of stress redistribution induced by excavation on the permeability change and groundwater flow around underground oil storage cavern. The exponential functions which describe the relationships of volumetric and lateral strains with permeability in elastic and plastic regions were derived and proposed. The deformational behavior of rock mass around cavern was analyzed using the finite element method, and the permeability change was evaluated by the relationships obtained from experimental results. The influence of permeability change on groundwater flow was also analyzed, and oil and gas leakage problems were investigated. RESUME: Cet article presente principalement I'influence de la redistribution des contraintes provoquees par I'exploitation sur Ie changement de permeabilite et ecoulement d'eau souterraine autour de la caverne pour stockage des petroles bruts. Les fonctions exponentielles que representent la relation de la deformation volumique et laterale avec la permeabilite dans les domaines elastiques et plastiques ont ete obtenues et proposees. Le comportement en deformation a ete etudie par la methode des elements finis, ainsi que Ie changement de permeabilite des massifs rocheux autour de la caverne a ete evalue par les relations obtenues des resultats experimentes. L'influence du changement de permeabilite sur l'ecoulement d'eau souterraine a ete analyse et les fuites de gaz et petroles sont egalement examinees. ZUSAMMENFASSUNG: Diese Untersuchung haldelt es sich urn den Einfluβ von der durch Abbruch hervorgerufenen Spannungsumlagerung auf Wasserdurchl assigkeits anderung und Grundwasserfluβ um einer untert agigen olspeicherkaverne. Die exponenten Funktionen sind abgeleitet und dargestellt, welche die Beziehungen von volumetrischer und lateraler Verformungen und Wasserdurchl assigkeit im elastischen und plastischen Bereich beschreiben. Das Verformungsverhalten der Felsmasse um Kaverne ist mit Finite-Elemente-Methode analysiert und die Permeabilit ats anderung ist mit der Versuchsergebnissen gewonnenen Beziehungen ausgewertet. Der Einfluβ der Permeabilittats anderung auf grundwasserfluβ ist analysiert und Sickerverlustprobleme von o1 und Gas sind untersucht, 1. INTRODUCTION Underground storage of crude oil and LPG has advantages of safety, environmental and economical aspects over above-ground storage systems and are very attractive commercially providing that geological conditions are favorable[l). The principles of oil and gas leakage control in underground oil storage cavern can be divided into permeability control and groundwater control. It, therefore, is very important to analyze the change of permeability of rock mass and groundwater level in designing grouting and water curtain system. This paper is mainly concerned with the influence of stress redistribution induced by excavation on permeability change and groundwater flow around underground oil storage cavern. The permeability around cavern is influenced by both blasting and stress relief[2](3). The influence of blasting on permeability change is confined to adjacent zone around cavern[3]. Therefore permeability change induced by stress redistribution was only considered. In this study, the relationship between strain and permeability was proposed based on a laboratory experiment using the transient pulse method[4]. The deformation behavior of rock mass around cavern was analyzed by the elasto-plastic finite element method and the changes of permeability was calculated using the relationship between strain and permeability. And an analysis of groundwater flow was carried out using the finite element method. The influence of permeability change on groundwater flow was analyzed and the oil and gas leakage was evaluated by considering the internal pressure of cavern. 2. SITE INVESTIGATION The underground oil storage facility is located at an island in southern Korea. It consists of six storage caverns, construction tunnels, connection tunnels and water curtain tunnels shown in Fig.1. The storage caverns are located at 30 ~ 60 m below a sea level and have a horse-shoe shaped cross section with a width of 18 m and a height of 30 m.
ABSTRACT: Water curtains comprise an interesting method to enhance the storage capacity of compressed, unlined gas storage and have been used for more than 20 years for this purpose. At the Röda Sten Rock Laboratory (RSRL), operated by Chalmers University of Technology, tests were performed in a pilot-scale rock cavern, explicitly constructed for gas storage experiments. The tests showed that no gas leakage occurred, provided the water curtain pressure, at all points, was higher than the gas pressure. At gas pressures above 1.0 MPa, complete gas containment was not achieved due to hydromechanical breakdown of the rock mass caused by the water curtain pressure. RÉSUMÉ: Les rideaux d'eau representent une methode interessante pour augmenter la capacite d'emmagasinage des depots sans doublure de gaz sous pression. Au laboratoire des roches de Röda Sten, en activite à I'Ecole Polytechnique de Chalmers, des essais dans une caverne pilote à l'echelle, exclusivement construite pour I'emmagasinage des gaz, ont ete effectues. Ces essais montrent qu'aucu ne fuite de gaz n'a eut lieu aussi longtemps que la pression du rideau d'eau etait en tous point s superieure à celle du gaz. Pour des press ions de gaz superieures à 1.0 MPa, une retenu e complete du gaz ne fut pas realisable à cause de Ie rupture hydromecanique de la masse rocheuse, causee par le pression du rideau d'eau. ZUSAMMENFASSUNG: Wasservorhange umfassen eine interessante Methode zur Erhöhung der Lagerungskapazitat beim Lagern von Gas unter Druck, in Raumen ohne Verkleidung. Sie haben seit ueber 20 Jahren fuer diesen Zweck Verwendung gefunden. Im Felslabor Röda Sten Rock Laboratory (RSRL), betrieben durch die Techni sche Universitat Chalmers, wurde eine Modellversuchsanlage einer Felskaverne geprueft, die ausdruecklich fuer Versuche mit Lagern von Gas konstruiert worden war. Die Pruefungen zeig ten keine Gaslecks an, unter Voraussetzung daβ der Druck des Wasservorhangs, an allen Punkten, höher war als der des Gases. Bei Gasdruecken ueber 1,0 MPa wurde kein vollstandiger Gaseinschluβ erreicht wegen hydromechanischer Zerteilung der Felsmasse verursacht durch den Druck des Wasservorhangs. 1. INTRODUCTION Storage of gas underground dates back to the beginning of the century when depleted gas and oil fields in the USA were used for this purpose. Even today, aquifer storage is widely used where an appropriate geology can be found. Another method where the geological conditions are used as a natural seal to prevent the gas from escaping is storage in leached salt formations. However, nature has only formed such geological settings in certain areas. Storage in hard rock geologies must be based on man-made caverns to create the necessary volume. Storage of pressurized gas in such caverns can be divided in two categories; lined and unlined caverns, where the former has a gas-tight membrane of steel or plastic attached to the cavern walls. For any unlined storage, gas containment depends on the presence and pressure of water in the rock mass around the storage. The water pressure situation, and thus the gas containment capacity is combined effect of the natural ground water pressure and the influence from the storage. Control of the water pressure in the rock mass prevents leakage and increases the gas containment capacity; such control is possible by the use of a water curtain. The following paper summarizes the most important results of a series of tests performed in a pilot- scale cavern at the Röda Sten Rock Laboratory (RSRL), operated by Chalmers University of Technology, Sweden. The material was presented as a doctoral thesis by the senior author (Söder. 1994).
- Europe > Sweden (0.68)
- North America > United States (0.48)
- Research Report > New Finding (0.50)
- Research Report > Experimental Study (0.40)
- Europe > Russia > Northwestern Federal District > Komi Republic > Timan-Pechora Basin > Pechora-Kolva Basin > Usa Field (0.97)
- North America > United States > California > Union Oil Field (0.89)
- Europe > United Kingdom (0.89)