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S. Harrison J. Molson H. Abercrombie J. Barker D. Rudolph R. Aravena 《Hydrogeology Journal》2000,8(6):608-622
Discovery of high contents of methane gas in coals of the Mist Mountain Formation in the Elk River valley, southeastern British
Columbia, Canada, has led to increased exploration activity for coal-seam gas (CSG). CSG production requires groundwater abstraction
to depressurize the coal beds and to facilitate methane flow to the production wells. Groundwater abstraction will have hydrodynamic
effects on the flow system, and an understanding of the groundwater flow system is needed to evaluate these effects. The purpose
of this paper is to describe the groundwater flow system in the area by means of a groundwater flow model and interpretation
of hydrochemical and isotopic analyses of groundwater and surface water.
Groundwater flow for the Weary Creek exploration area is modeled in two vertical sections. The model domains, based on classic
upland–lowland conceptual flow models, are approximately 10,000 m long and 4,000 m deep. Each consists of a fixed water-table
boundary and no-flow boundaries along the traces of major faults. Steady-state groundwater flow is calibrated to hydraulic-head,
streamflow, and groundwater-recharge data. Simulated steady-state velocity fields define regional and local flow components
consistent with the conceptual model.
The results are consistent with regional trends in δ2H, δ18O, tritium, and TDS, which define two distinct groundwater groups (A and B) and a third of intermediate composition. An active,
shallow, local flow component (group A) is recharged in beds cropping out along subdued ridges; this component discharges
as seeps along lower and mid-slope positions in the southern part of the study area. The waters are tritiated, relatively
enriched in δ2H and δ18O, and have low TDS. A deeper regional flow component (group B), which originates at a higher altitude and which discharges
to the Elk River valley bottom, is characterized by non-tritiated groundwater with relatively depleted δ2H and δ18O, and higher TDS.
Groundwater contributes less than 10% of the total direct flow to the Elk River, as indicated by flow measurements and by
the absence of group A and group B characteristics in the river water. Thus it is hypothesized that groundwater extraction
during CSG production will have little impact on the river. The groundwater flow model developed in this work is used in a
companion paper to further test this hypothesis.
Electronic Publication 相似文献
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Aarthy Sabesan Kathleen Abercrombie Auroop R. Ganguly Budhendra Bhaduri Eddie A. Bright Phillip R. Coleman 《GeoJournal》2007,69(1-2):81-91
Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas, including,
but not limited to, the mitigation of natural and man-made disasters. Three sets of metrics, adopted or customized from geo-statistics,
applied meteorology and signal processing, are tested in terms of their ability to evaluate geospatial datasets, specifically
two population databases commonly used for disaster preparedness and consequence management. The two high-resolution, grid-based
population datasets are the following: The LandScan dataset available from the Geographic Information Science and Technology
(GIST) group at the Oak Ridge National Laboratory (ORNL), and the Gridded Population of the World (GPW) dataset available
from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Case studies evaluate
population data across the globe, specifically, the metropolitan areas of Washington DC, USA, Los-Angeles, USA, and Houston,
USA, and London, UK, as well as the country of Iran. The geospatial metrics confirm that the two population datasets have
significant differences, especially in the context of their utility for disaster readiness and mitigation. While this paper
primarily focuses on grid based population datasets and disaster management applications, the sets of metrics developed here
can be generalized to other geospatial datasets and applications. Future research needs to develop metrics for geospatial
and temporal risks and associated uncertainties in the context of disaster management.
The U. S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged. 相似文献
4.
Can observations of earthquake scaling constrain slip weakening? 总被引：4，自引：0，他引：4
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美国地球物理联合会(American Geo-physical Union)最近在美国缅因州波特兰举行了AGU Chapman会议。在接近Two Lights断层区域和Fort Foster脆性区域,现场考察了大西洋沿岸岩石暗礁。现场考察的负责人Dr.Mark Swanson和他的学生在过去20年来详细地研究了该区域,与会人员考察了3 相似文献
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A three-dimensional, finite-element flow model was used to assess the hydrogeological effects of depressurizing coalbeds
lying in the Weary Creek exploration block, Elk River valley, southeastern British Columbia, Canada. The simulation results
permit, at an early stage, assessment of the environmental and economic implications of how the flow system may respond to
depressurization.
Estimated reservoir conditions for the coal-seam gas targets lying within the Upper Jurassic–Lower Cretaceous Mist Mountain
Formation indicate that the coalbeds must be depressurized by up to 350 m to attain the critical gas desorption pressure.
The simulations suggest that depressurizing has little effect on groundwater flux to the Elk River. Simulated water production
for three depressurizing wells operating under steady-state, single-phase flow for initial reservoir conditions of 13 and
16.5 cm3/g is 645 m3/d (4,057 barrels/d) and 355 m3/d (2,233 barrels/d), respectively.
Groundwaters collected from monitoring wells have relatively low salinity, ranging from about 250–1,300 mg/L. The groundwater
is supersaturated with respect to Ca–Mg–Fe carbonates (calcite, dolomite, and siderite) and Al-bearing silicates, including
kaolinite and illite. Dissolved trace-metal concentrations are low; only Fe, Cd, Cr, and Zn exceed Canadian water-quality
guidelines for aquatic life. Groundwaters were devoid of the more soluble monocyclic aromatic organic compounds, including
benzene, toluene, ethylbenzene, and polycyclic aromatic compounds, including naphthalene.
Electronic Publication 相似文献
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H. J. Abercrombie G. B. Skippen D. D. Marshall 《Contributions to Mineralogy and Petrology》1987,97(3):305-312
The distribution of F between tremolite and talc has been determined in metamorphosed siliceous carbonates from the Grenville Province, Ontario. Wavelength dispersive electron microprobe analyses of contiguous, texturally compatible tremolite-talc pairs indicate that the substitution of F for OH is the most significant deviation from end-member stoichiometry in the samples studied. Mixing of F and OH components has been represented by an ideal solution model for F in tremolite and an asymmetric model for F in talc. Both linear and nonlinear regression techniques have been used to derive activity coefficients for the exchange of one equivalent of OH and F components in talc. The following expressions are the result of nonlinear regression of 32 analyses from coexisting mineral pairs: $$\begin{gathered} \ln \gamma _{TC(OH)} = X_{TC(F)}^2 [2.447 - 2.845X_{TC(OH)} ] \hfill \\ \ln \gamma _{TC(F)} = X_{TC(OH)}^2 [1.024 + 2.845X_{TC(F} ] \hfill \\ \end{gathered} $$ Isobaric \(T - X_{CO_2 } \) sections constructed using these equations show an enhanced stability for the assemblages talc+calcite and phlogopite+quartz+calcite with F substituting for OH. Projection of isothermal invariant points into P-T space predicts a shift in the stability of the assemblage talc-calcite from lower grade into the sillimanite field with increasing substitution of F for OH in talc. 相似文献
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R. E. Abercrombie 《Pure and Applied Geophysics》1998,153(2-4):475-487
—Earthquake seismograms recorded by instruments in deep boreholes have low levels of background noise and wide signal bandwidth. They have been used to extend our knowledge of crustal attenuation both in the near-surface and at seismogenic depths. Site effects are of major importance to seismic hazard estimation, and the comparison of surface, shallow and deep recordings allows direct determination of the attenuation in the near-surface. All studies to date have found that Q is very low in the near-surface (～ 10 in the upper 100 m), and increases rapidly with depth. Unlike site amplification, attenuation at shallow depths exhibits little dependence on rock-type. These observations are consistent with the opening of fractures under decreasing lithostatic pressure being the principal cause of the severe near-surface attenuation. Seismograms recorded in deep boreholes are relatively unaffected by near-surface effects, and thus can be used to measure crustal attenuation to higher frequencies (≥ 100 Hz) than surface recordings. Studies using both direct and coda waves recorded at over 2 km depth find Q to be high (～ 1000) at seismogenic depths in California, increasing only weakly with frequency between 10 and 100 Hz. Intrinsic attenuation appears to be the dominant mechanism. These observations contrast with those of the rapidly increasing Q with frequency determined from surface studies in the frequency range 1 to 10 Hz. Further work is necessary to constrain the factors responsible for this apparent change in the frequency dependence of Q, but it is clearly unwise to extrapolate Q estimates made below about 10 Hz to higher frequencies. 相似文献
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Yun Liu Stuart Crampin Rachael E. Abercrombie 《Geophysical Journal International》1997,129(2):439-449
53 local earthquakes recorded at 2.5 km depth in the Cajon Pass scientific borehole are analysed for shear-wave splitting. The time delays between the split shear waves can be positively identified for 32 of the events. Modelling these observations of polarizations and time delays using genetic algorithms suggests that the anisotropic structure near Cajon Pass has orthorhombic symmetry. The polarization of the shear waves and the inferred strike of the stress-aligned fluid-filled intergranular microcracks and pores suggests that the maximum horizontal compressional stress direction is approximately N13°W. This is consistent with previous results from earthquake source mechanisms and the right-lateral strike-slip motion on the nearby San Andreas Fault, but not with stresses measured within the uppermost 3 km of the borehole. This study suggests that the San Andreas Fault is driven by deeper tectonic stresses and the present understanding of a weak and frictionless San Andreas Fault may need to be modified. The active secondary faulting and folding close to the fault are probably driven by the relatively shallow stress as measured in the 3.5 km deep borehole. 相似文献
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