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Monitoring of subsidence and induced seismicity in the Lacq gas field (France): the consequences on gas production and field operation
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Groundwater problems 931507 Potentiometric and aquifer property changes above subsiding longwall mine panels, Illinois Basin coalfield Booth, C J; Spande, E D Ground Water V30, N3, May-June 1992, P362-368 Hydrological changes resulting from subsidence over a 220m deep active longwall panel are described. The overburden is mainly shale but includes a shallow sandstone aquifer overlain by a shale aquitard capped with drift. Pumping and packer tests indicate that the hydraulic conductivity of the sandstone aquifer increased by about I order of magnitude, that of some lower horizons by several orders of magnitude. The drift aquifer was unaffected by mining. Heads in the bedrock unit dropped sharply in response to mining. Head in the sandstone aquifer declined slowly ahead of mining, with rapid partial recovery afterwards. Potentially higher well yields are found. 931508 Description and status of the Yucca Mountain project repository sealing program Fernandez, J A; Hinkebein, T E Proe 1st Annual Topical Meeting on High Level Radioactive Waste Management, Las Vegas, 8-12 April 1990 V1, P658660. Publ La Grange Park: ANS/ASCE, 1990 Sealing design options and design requirements for the Yucca Mountain Project are examined. Different approaches are made to sealing of shafts and ramps, the underground facility, and exploratory boreholes. The philosophy may be to maximise impermeability or to route water away from undesirable areas. Materials selection is discussed. Natural earthen materials are thought less likely to deteriorate with time than concrete or grout materials. Controlled blasting is suggested to minimise fracturing at potential seal locations. 931509 Reducing groundwater flow model uncertainties at Yucca Mountain Albrecht, K A; Fenster, D F; Van Camp, S G Proe Conference on Calibration and Reliability in Groundwater Modelling, The Hague, 3-6 September 1990 P301-309. Publ Wallingford: IAHS Press, 1990 (IAHS Publication No. 195) Groundwater travel time (GWTT) regulations applicable to the Yucca Mountain site specify a minimum of 1000 years from repository to accessible environment along the most rapid path. Site geology is described and a conceptual flow model discussed. The low fluxes in the unsaturated zone containing the repository level and its great thickness contribute to the long travel times expected. Parameter values necessary to reduce uncertainty in these calculations must be obtained from large scale field tests in dry drilled holes at depths down to repository level.
contact roughness on strata movement evaluated for comparison with field data. Best fit is obtained when a relatively low stiffness value is maintained constant for all contacts. Increasing density of vertical joints or reducing contact roughness do not markedly improve fit. 931511 Monitoring of subsidence and induced seismicity in the Lacq Gas Field (France): the consequences on gas production and field operation Maury, V M R; Grasso, J R; Wittlinger, G Engng Geol V32, N3, May 1992, P123-135 Pressure depletions and subsidence resulting from exploitation of the Lacq field in the periods 1957-1967 and 1967-1989 are described. Induced seismicity recorded during the latter period is also discussed. The seismic data have been processed and the fractures responsible and kinematics of displacement evaluated. The regional mechanism appears to be lowering of a rigid block at the top of the structure by a succession of movements along pre-existing fractures and faults. Calculated amplitudes of fault slip are in the order of millimetres. The possibility of increasing knowledge of reservoir response on the basis of analysis of induced seismicity is considered. 931512 Subsidence and ground movements in chalk Bell, F G; Culshaw, M G; Moorlock, B S P; Cripps, J C lnt Assoc Engng Geol Bull N45, April 1992, P75-82 Subsidence in chalk terrain in the U K as a result of collapse of old mine workings is considered. Investigation techniques to detect these workings are described: remote sensing, aerial photography, geophysical methods, and direct examination. Subsidence hazard assessment methods are presented. Two case histories of subsidence associated with old workings are illustrated, one at Bury St Edmonds, Suffolk, the other at Grays, Essex. 931513 Combating the problem of rockbursts at KGF - contributions of National Institute of Rock Mechanics gaju, N M; Jha, P C; Shringarputale, S B; Srinivasan, C; Sivakumar, C J Min Metal Fuels V39, Nll/12, Nov-Dec 1991, P370-376 Rockbursts present a major problem in the Kolar Gold Fields. Statistical analysis of stope convergence data allows identification of action limits and warning limits on the basis of closure rate, but this provides some warning of rockburst only in the immediate vicinity of the stope. Seismic data have been analysed and zones of high and low stress within the rock mass delineated. Periodic review of these stress maps shows migratory trends of seismic fronts in the mining region, with possible projection of future location of danger areas. Analysis of the microseismic signature of rockbursts may permit their prediction on a relatively short time scale.
Surface subsidence, caving and rockbursts 931510 Hybrid discrete element code for simulation of mining-induced strata movements O'Connor, K M; Dowding, C H Engng Comput vg, N2, April 1992, P235-242 A hybrid rigid block model, combining a small displacement code and a large displacement code, is presented to simulate the kinematics of mining-induced subsidence in a blocky rock mass. Subsidence over a longwall panel is modelled, and influence of rigid block contact stiffness, vertical joint density, and
931514 Seismieity associated with deep-level mining at Western Deep Levels Limited Lenhardt, W A J S Aft, lnst Min MetaU V92, N5, May 1992, Pl13-120 Results of 5 years research into mining-induced seismicity are summarized. The various types of event and models of their mechanisms are presented: shear slip; fault slip; slip along dyke contacts; abutment failure; pillar foundation failure; and crush. Most seismicity results from mining geologically disturbed areas. Reduction of seismic potential is discussed.
© 1993 Pergamon Press Ltd. Reproduction not permitted
Groundwater problems 931507 Potentiometric and aquifer property changes above subsiding longwall mine panels, Illinois Basin coalfield Booth, C J; Spande, E D Ground Water V30, N3, May-June 1992, P362-368 Hydrological changes resulting from subsidence over a 220m deep active longwall panel are described. The overburden is mainly shale but includes a shallow sandstone aquifer overlain by a shale aquitard capped with drift. Pumping and packer tests indicate that the hydraulic conductivity of the sandstone aquifer increased by about I order of magnitude, that of some lower horizons by several orders of magnitude. The drift aquifer was unaffected by mining. Heads in the bedrock unit dropped sharply in response to mining. Head in the sandstone aquifer declined slowly ahead of mining, with rapid partial recovery afterwards. Potentially higher well yields are found. 931508 Description and status of the Yucca Mountain project repository sealing program Fernandez, J A; Hinkebein, T E Proe 1st Annual Topical Meeting on High Level Radioactive Waste Management, Las Vegas, 8-12 April 1990 V1, P658660. Publ La Grange Park: ANS/ASCE, 1990 Sealing design options and design requirements for the Yucca Mountain Project are examined. Different approaches are made to sealing of shafts and ramps, the underground facility, and exploratory boreholes. The philosophy may be to maximise impermeability or to route water away from undesirable areas. Materials selection is discussed. Natural earthen materials are thought less likely to deteriorate with time than concrete or grout materials. Controlled blasting is suggested to minimise fracturing at potential seal locations. 931509 Reducing groundwater flow model uncertainties at Yucca Mountain Albrecht, K A; Fenster, D F; Van Camp, S G Proe Conference on Calibration and Reliability in Groundwater Modelling, The Hague, 3-6 September 1990 P301-309. Publ Wallingford: IAHS Press, 1990 (IAHS Publication No. 195) Groundwater travel time (GWTT) regulations applicable to the Yucca Mountain site specify a minimum of 1000 years from repository to accessible environment along the most rapid path. Site geology is described and a conceptual flow model discussed. The low fluxes in the unsaturated zone containing the repository level and its great thickness contribute to the long travel times expected. Parameter values necessary to reduce uncertainty in these calculations must be obtained from large scale field tests in dry drilled holes at depths down to repository level.
contact roughness on strata movement evaluated for comparison with field data. Best fit is obtained when a relatively low stiffness value is maintained constant for all contacts. Increasing density of vertical joints or reducing contact roughness do not markedly improve fit. 931511 Monitoring of subsidence and induced seismicity in the Lacq Gas Field (France): the consequences on gas production and field operation Maury, V M R; Grasso, J R; Wittlinger, G Engng Geol V32, N3, May 1992, P123-135 Pressure depletions and subsidence resulting from exploitation of the Lacq field in the periods 1957-1967 and 1967-1989 are described. Induced seismicity recorded during the latter period is also discussed. The seismic data have been processed and the fractures responsible and kinematics of displacement evaluated. The regional mechanism appears to be lowering of a rigid block at the top of the structure by a succession of movements along pre-existing fractures and faults. Calculated amplitudes of fault slip are in the order of millimetres. The possibility of increasing knowledge of reservoir response on the basis of analysis of induced seismicity is considered. 931512 Subsidence and ground movements in chalk Bell, F G; Culshaw, M G; Moorlock, B S P; Cripps, J C lnt Assoc Engng Geol Bull N45, April 1992, P75-82 Subsidence in chalk terrain in the U K as a result of collapse of old mine workings is considered. Investigation techniques to detect these workings are described: remote sensing, aerial photography, geophysical methods, and direct examination. Subsidence hazard assessment methods are presented. Two case histories of subsidence associated with old workings are illustrated, one at Bury St Edmonds, Suffolk, the other at Grays, Essex. 931513 Combating the problem of rockbursts at KGF - contributions of National Institute of Rock Mechanics gaju, N M; Jha, P C; Shringarputale, S B; Srinivasan, C; Sivakumar, C J Min Metal Fuels V39, Nll/12, Nov-Dec 1991, P370-376 Rockbursts present a major problem in the Kolar Gold Fields. Statistical analysis of stope convergence data allows identification of action limits and warning limits on the basis of closure rate, but this provides some warning of rockburst only in the immediate vicinity of the stope. Seismic data have been analysed and zones of high and low stress within the rock mass delineated. Periodic review of these stress maps shows migratory trends of seismic fronts in the mining region, with possible projection of future location of danger areas. Analysis of the microseismic signature of rockbursts may permit their prediction on a relatively short time scale.
Surface subsidence, caving and rockbursts 931510 Hybrid discrete element code for simulation of mining-induced strata movements O'Connor, K M; Dowding, C H Engng Comput vg, N2, April 1992, P235-242 A hybrid rigid block model, combining a small displacement code and a large displacement code, is presented to simulate the kinematics of mining-induced subsidence in a blocky rock mass. Subsidence over a longwall panel is modelled, and influence of rigid block contact stiffness, vertical joint density, and
931514 Seismieity associated with deep-level mining at Western Deep Levels Limited Lenhardt, W A J S Aft, lnst Min MetaU V92, N5, May 1992, Pl13-120 Results of 5 years research into mining-induced seismicity are summarized. The various types of event and models of their mechanisms are presented: shear slip; fault slip; slip along dyke contacts; abutment failure; pillar foundation failure; and crush. Most seismicity results from mining geologically disturbed areas. Reduction of seismic potential is discussed.
© 1993 Pergamon Press Ltd. Reproduction not permitted