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Europe
AE Monitoring And X-Ray Ct Observation For Failure Of Berea Sandstone With Pore Pressure Increase
Niwa, T. (Kyoto University) | Ishida, T. (Kyoto University) | Fukahori, D. (Kyoto University) | Ishida, M. (Kyoto University) | Sato, R. (Kyoto University) | Murata, S. (Kyoto University) | Onozuka, S. (Japan Oil, Gas and Metals National Corporation) | Oseto, K. (Japan Oil, Gas and Metals National Corporation) | Yamamoto, K. (Japan Oil, Gas and Metals National Corporation)
We monitored AE events accompanied with a failure of Berea sandstone specimen induced by pore pressure increase in a tri-axial test. After the test, several located AE events were compared with X-ray CT images obtained on the fractured specimen. The comparison elucidated that most of the sources are closed to or exactly on the locations of macroscopic fracture planes. From the stress and strain data, we also found that the failure can be explained and predicted by Mohr-Coulomb's criterion and the effective stress theory. 1. INTRODUCTION AE (Acoustic Emission) monitoring has been recently often applied to detect behavior of petroleum reservoirs. For example, at oil fields in Ekofisk and Valhall in North Sea and in Clinton County, Kentucky in U.S., AE events have been monitored with operation of EOR (enhanced oil recovery) [1]. EOR is the technology to recover oil and gas from depleted reservoirs by injecting fluid such as water, natural gas, and carbon dioxide. Since AE events are most likely caused with increase of pore pressure by the injected fluid, the AE monitoring helps to understand how the injected fluid penetrates and permeates. In this research, we monitored AE events accompanied with a failure of Berea sandstone specimen induced by pore pressure increase in a tri-axial experiment. Moreover, we compared location of AE sources to fracture planes on X-ray CT (computed tomography) images obtained after the experiment. 2. EXPERIMENTAL METHOD In this experiment, we used a cylindrical specimen of Berea sandstone, measuring 38mm in diameter and 76mm in height, as shown in Figure 1. P-wave velocities of the specimen measured along X-, Y-, and Z-directions were 2.46, 2.48, 2.46 km/s, respectively. This indicates that the specimen is almost isotropic. Since a permeability test conducted on the specimen indicated a large permeability, 92.1md, the specimen was expected to be completely saturated in a few seconds after applying pore pressure in the tri-axial test. To monitor AE events, twelve cylindrical piezoelectric elements, 5 mm in diameter and 6.7 mm long, having resonance frequency of 300 kHz, were placed on the surface of the specimen. After above preparations, the specimen covered by silicon rubber with pedestals was set in a pressure cell, and tri-axial test was conducted. After the tri-axial test, X-ray CT images were obtained on the fractured specimen with a medical CT scanner (TOSHIBA Aquilion16). Through using the CT scanner, we can observe cracks inside of the specimen with leaving silicon rubber covering the specimen, only with removing piezoelectric elements and strain gauges that interrupt X-ray due to their high density. 3. RESULTS Fig.2 shows change of axial pressure (σ1), confining pressure (σ3), pore pressure (P), and strains (ε1, ε3 and εvol) along the elapsed time in this experiment. The procedure of this experiment is shown as follows. 3.1. Procedure of Loading At the first step from the beginning to the point (1) in Fig.2, the specimen was set in a pressure cell, and then the axial pressure was applied slightly.
- North America > United States > West Virginia (1.00)
- North America > United States > Pennsylvania (1.00)
- North America > United States > Ohio (1.00)
- North America > United States > Kentucky > Clinton County (0.24)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/4 > Greater Ekofisk Field > Ekofisk Field > Tor Formation (0.97)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/4 > Greater Ekofisk Field > Ekofisk Field > Ekofisk Formation (0.97)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Tor Formation (0.97)
- (3 more...)
Evaluation Of Underground Research Laboratories For Formulation Of Interdisciplinary Global Networks
Wang, Joseph S.Y. (Lawrence Berkeley National Laboratory) | Smeallie, Peter H. (American Rock Mechanics Association) | Feng, Xia-Ting (Institute of Rock and Soil Mechanics, The Chinese Academy of Sciences) | Hudson, John A. (International Society of Rock Mechanics and Imperial College)
SYNOPSIS: Developed in the 1970s in Sweden for thermal and hydrological responses in hard rock to emplacements of spent nuclear materials, underground research laboratories (Ur's) have since been and are continuously being established worldwide in different formations for studying coupled thermal-hydrological-mechanical-chemical biological processes, as well as for CO2 sequestration testing. Deep underground laboratories have been concurrently developed for physics research from the middle of the 20th century to the present. The knowledge and experience from Ur's at different sites locally, nationally, and regionally can certainly be networked globally. In this article, we evaluate the status of Ur's in preparation for a URL network workshop associated with the 2011 ISM Beijing Congress. The relatively quiet conditions underground and the optimum signal-to-noise ratios are among factors favoring linkages among Ur's for interdisciplinary studies and for developing global networks. International and interdisciplinary collaborations enhance interest in formulating URL networks and in demonstrating underground locations as potential settings for technological innovations. 1. WORKSHOP ON UNDERGROUND RESEARCH LABORATORY NETWORKS FOR INTERNATIONAL, INTERDISCIPLINARY INNOVATION An Underground Research Laboratory (URL) workshop is proposed for October 17, 2011, one day before the technical program of the International Society for Rock Mechanics (ISM) 2011 Beijing Congress. The URL workshop concept and logistics were discussed with ISM directors and colleagues, and the URL Workshop scheme was recently presented to the American Rock Mechanics Association (ARMS). We plan to schedule the one-day workshop with overview lectures, covering different topics given by experts. In the following sections, case histories from underground investigations in past decades are first summarized, to form the basis for addressing key questions and mechanisms in the formation of URL global networks. Thus, the URL workshop plans to cover primarily:Ur's for nuclear waste research, with over six sites existing in Europe, three in North America, four in Japan, one in Korea, and one planned in China; deep underground laboratories (Du's) dedicated primarily to basic physics research, with ~10 sites operated or planned worldwide; and mines and underground facilities for energy and environmental research, such as CO2 capture and storage study networks in Europe and North America, and the biology-seismic study site in South Africa. Topics 2–6 are on broad issues, 7–11 on detailed findings, leading to network discussions in 12. 2. FROM SWEDEN'S HARD ROCK LABORATORY TO CHINA'S COMPETENT, SPARSELY FRACTURED SITE FOR NUCLEAR WASTE STUDY AND THE DEEPEST TUNNEL LABORATORY FOR PHYSICS RESEARCH The Strips Sweden iron mine was converted in 1977 to a hard rock URL—the first hard rock URL dedicated to thermal mechanical testing and hydrological flow/transport characterization [2–4]. The thermal-mechanical studies there used heaters emplace below drift floors to simulate full-scale and scaled-down spent-nuclear-fuel canisters. Fracture deformations in the granitic rock (and crystalline rocks in general) were likely the main reason for the lower induced stress and the lesser deformations measured in the field than predicted by elastic models, which used intact rock properties that were derived from laboratory tests.
- Europe (1.00)
- North America > United States > California (0.46)
- Asia > China > Beijing > Beijing (0.44)
- (2 more...)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Rock Type (1.00)
- Geology > Mineral (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Gravity Surveying > Gravity Acquisition (0.68)
- Geophysics > Seismic Surveying > Passive Seismic Surveying (0.46)
- Water & Waste Management > Solid Waste Management (1.00)
- Materials > Metals & Mining (1.00)
- Energy > Power Industry > Utilities > Nuclear (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (23 more...)
- Reservoir Description and Dynamics > Storage Reservoir Engineering > CO2 capture and sequestration (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- (5 more...)
ABSTRACT: The Longitudinal Deformation Profile (DP) is an important component of the Convergence- Confinement method. The present study concerns numerical simulation, by means of the finite difference code FLAX 3D, to calculate the DP curve for an unlined tunnel driven in a Burger viscoelastic rock mass model in various stress fields. Model constants of the Burger rock mass are selected according to a detailed literature review and parameterized in order to simulate different time-dependent situations of rock mass. The results are plotted, analyzed, discussed and compared against known empirical solutions and found in good agreement. 1. BACKGROUND 1.1. Time-dependent response Observed displacement of a specific point in an underground excavation can be expressed as the sum of displacements caused by two effects, the face advance and the time dependent reaction of the ground. In order to describe the time-dependent deformation due to creep in tunnels, various approaches have been established based on analytical, empirical and numerical methods. To briefly report an indicative selection of researches that include time in stability analysis of tunnels, one would start with the basic research that was presented by Salem et al [12]. In their suggested analytical method an explicit solution was proposed for the determination of the radial displacements and the ground pressure acting on tunnel support. It was based on a Kelvin-Voigt theological model. A closed-form solution for the calculation of the pressure acting on tunnel support structures was given by Samurai [10]. He introduced an "equivalent initial stress" in order to solve three-dimensional effects of the tunnel face progression with a two-dimensional plane strain model of tunnel- support structures for elastic and viscoelastic media. Also, by means of a three component viscoelastic model, relations are given for the calculation of tunnel wall displacement and pressure on lining. In another research by Ghaboussi and Gilda [4], the short-term effects that develop when a tunnel is driven in a ground showing viscous behaviour associated with the devi atomic deformations is studied. Also, radial deformation of a lined tunnel when there is an unsupported zone between the face of the excavation and the liner, the effects of a temporary interruption of the excavation process and of various rates of tunnel excavation. More recently, Salami [11] performed viscoelastic analysis with the Abacus code to model ground squeezing through the heavily sheared and fault zones of the Red Pine shale of still-water tunnel (Utah, USA) under an overburden of 700 m. He concluded that the effect of tunnel face advance on the crown displacement extends to a distance of about 2 tunnel diameters behind the tunnel face and 1.5 tunnel diameters ahead of the face. This zone of influence is slightly wider than the zone that has been predicted from elastic analysis. Yiouta-Mitra et al [15] performed viscoelastic analysis of materials with swelling and creep potential to investigate the effects on the tunnel final lining loads. Sophistic numerical code and the viscoelastic Persona model were used on the basis of the convergence-confinement method.
- Asia (1.00)
- Europe (0.93)
- North America > United States > Utah (0.24)
SYNOPSIS: The present paper deals with climate change impact on stability of underground cavities due to its indirect effect on ground water levels. In France, several back-analyses have confirmed that variations of underground water tables play a key role in the genesis of surface disorders above shallow mine workings. The paper presents the forecast impacts of climate change on the behaviour of underground water tables as well as the consequences of those variations on the stability of disused underground cavities. A particular collapse that affected the Paris Basin during a major flood of the Seine River, one century ago (January 1910), with dramatic consequences, illustrates the importance of water variation impacts on the rock mass behaviour. The high sensitivity of the extracted material (very pure chalk) to water as well as the dynamics of the mine flooding process are described. The most realistic mechanisms and scenario enabling to explain massive failure of the underground workings are then discussed. 1. INTRODUCTION The existence of a global warming process of the global climate is now well admitted by the scientific community. The rise of the average temperatures of air and oceans, as well as the observation of the de-icing of ice caps and the rise of mean sea level constitute some clear indicators. The various studied prospective scenarios, depending on the efficiency of prevention policies engaged by governments show that, up to 2100, the average rise in temperature on the surface of the Earth could vary between 1,5 and 6 °C [1]. Such a temperature increase would be likely to generate serious disturbances on climatic parameters (e.g. modification of rainfalls, disturbances of water tables). Numerous international studies are being performed in order to make progress in the understanding and prediction of the consequences of the presumed climate change. Among these studies, very few relate to the matter of underground cavities. The paper deals with the impact of climate change on stability of underground cavities. This topic may become a serious problem in France due to the existence of very numerous (hundred of thousands) shallow underground cavities, natural or manmade, well known or totally unlocated, undermining French territory. Several recent examples have confirmed that, among those, the level and variations of underground water tables have a key role in the genesis of surface disturbances. Major trends concerning the forecast impacts of climate change on underground water tables as well as the consequences of those variations on the mechanical behaviour of shallow underground workings (impacts on strata and discontinuities) are thus briefly presented. Among others, the specific case of a ground collapse (with dramatic human consequences: 7 deaths and 7 severe injured persons) that affected the Paris Basin during a major flood of the Seine River, one century ago is then described, as a perfect illustration of the importance of water variation impacts on rock mass behaviour. The chalk mine of Lorroy (city of Chateau-Landon), collapsed in January 1910, in direct connection with the flood of the Seine River.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Geological Subdiscipline > Environmental Geology > Hydrogeology (1.00)
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (0.93)