Article

Hydrogeophysical Methods for Analyzing Aquifer Storage and Recovery Systems

U.S. Geological Survey, Denver Federal Center, MS964, Denver, CO 80225, USA.
Ground Water (Impact Factor: 1.95). 02/2010; 49(2):250-69. DOI: 10.1111/j.1745-6584.2010.00676.x
Source: PubMed

ABSTRACT Hydrogeophysical methods are presented that support the siting and monitoring of aquifer storage and recovery (ASR) systems. These methods are presented as numerical simulations in the context of a proposed ASR experiment in Kuwait, although the techniques are applicable to numerous ASR projects. Bulk geophysical properties are calculated directly from ASR flow and solute transport simulations using standard petrophysical relationships and are used to simulate the dynamic geophysical response to ASR. This strategy provides a quantitative framework for determining site-specific geophysical methods and data acquisition geometries that can provide the most useful information about the ASR implementation. An axisymmetric, coupled fluid flow and solute transport model simulates injection, storage, and withdrawal of fresh water (salinity ∼500 ppm) into the Dammam aquifer, a tertiary carbonate formation with native salinity approximately 6000 ppm. Sensitivity of the flow simulations to the correlation length of aquifer heterogeneity, aquifer dispersivity, and hydraulic permeability of the confining layer are investigated. The geophysical response using electrical resistivity, time-domain electromagnetic (TEM), and seismic methods is computed at regular intervals during the ASR simulation to investigate the sensitivity of these different techniques to changes in subsurface properties. For the electrical and electromagnetic methods, fluid electric conductivity is derived from the modeled salinity and is combined with an assumed porosity model to compute a bulk electrical resistivity structure. The seismic response is computed from the porosity model and changes in effective stress due to fluid pressure variations during injection/recovery, while changes in fluid properties are introduced through Gassmann fluid substitution.

Full-text

Available from: Jonathan Ajo-Franklin, May 06, 2015
2 Followers
 · 
137 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Aquifer storage and recovery (ASR) methods are increasingly used to overcome the temporal imbalance between water demand and availability. Common ASR recharge methods utilize large-diameter injection wells or surface infiltration basins and trenches, and can be costly to implement. A new low-cost ASR recharge method is currently being developed. This approach is based on recharge via gravity in small-diameter wells installed with direct-push (DP) technology. Numerical modeling is used here to assess the potential of this new approach under conditions commonly faced in field settings. The primary objective is to investigate if a battery of small-diameter DP wells can serve as a viable alternative to a surface basin under typical field conditions, while the secondary objective is to assess which subsurface parameters have the greatest control on DP well performance. Simulation results indicate that gravity recharge via small-diameter wells appears to have a distinct advantage over recharge via surface infiltration basins. For example, two 0.05-m shallow vadose-zone wells with 9-m screens can recharge water at a greater rate than a 60 m2 basin. Also, results reveal that, contrary to an infiltration basin, the recharge rate in a DP well has a much stronger dependence on the horizontal component of hydraulic conductivity than on the vertical component. Moreover, near-surface layers of low hydraulic conductivity, which can significantly reduce the recharge capacity of a surface basin, have a relatively small impact on the recharge capacity of a well as long as a significant portion of the well screen is installed below those layers. Given that installation and operation costs can be low in comparison to common ASR recharge methods, this new approach appears to have great potential for recharging good quality water in shallow unconsolidated aquifers. A field investigation has recently been initiated to follow up the findings of this simulation assessment.
    Journal of Hydrology 09/2014; 517:54–63. DOI:10.1016/j.jhydrol.2014.05.003 · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Information generated from geophysical, geochemical and hydrogeological data has been used in assessing the groundwater resource potential, quality and usability and in mapping flow directions within the shallow subsurface of the Mamfe Embayment, Cross River State, Nigeria. The electrical resistivity technique in which the Schlumberger’s vertical electrical sounding field procedure has been adopted was the geophysical method employed; lithology logs from drilling records, discharge rates, static water level information were the hydrogeological information utilized, while the geochemical techniques involve analyses of water samples. Apparent resistances were measured using different resistivity meters including OYO McOhm (model 2115), ABEM terrameter (SAS300B and SAS1000 models) and IGIS (SSP-ATS-MRP model) with maximum current electrode separation reaching 1 km in some communities. Geological information was used as control in the modelling and interpretation of all geophysical data. The physico-chemical parameters of the water samples from the different water sources in the area were determined using different analytical techniques and in some cases, by in situ direct measurement of some parameters. Measured values of electrical conductivity, static water level, available aquifer discharge information and calculated SAR and %Na were integrated into the geophysical and hydrogeological results. The shallow subsurface of the area is segmented into four hydrogeological provinces [crystalline basement province (CBP), Cross River Plain Province (CRPP), Nkporo-Afikpo Shales Province (NASP) and alluvial/buried river province (ABRP) with localized groundwater flow patterns]. Results indicated that the alluvial (discharge rate of 3.83 L/s), fractured sandstone (discharge rate of 2.43 L/s) and basement (discharge rate of 1.80 L/s) aquifers are more yielding than the aquifers in areas covered with deformed shales (discharge rate of 0.62 L/s) and siltstone aquifers (discharge rate of 0.97 L/s). The aquifer horizons are inhomogeneous and anisotropic with topography and lithology exerting significant influence on groundwater flow direction. However, there appears to be some high yielding aquifers at depths greater than 100 m in the CRPP areas although researches on their distribution are still ongoing. Precipitation is the major source of recharge and the water is enriched with Na+, K+, Ca2+, Mg2+, ${\text{HCO}}_{ 3}^{ - }$ , Cl−, ${\text{SO}}_{ 4}^{2 - }$ and ${\text{NO}}_{ 3}^{ - }$ throughout the year. Graphical analyses of hydrochemical data using Piper and Stiff diagrams show that Ca–(Mg)–CO3–HCO3 is the dominant water facies. Results from EC, SAR and %Na show that the water is fresh and belongs to the good-to-excellent class and is, therefore, suitable for domestic, agricultural and industrial use.
    Environmental earth sciences 10/2013; DOI:10.1007/s12665-013-2232-3 · 1.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Geoelectrical techniques are widely used to monitor groundwater processes, while surprisingly few studies have considered audio (AMT) and radio (RMT) magnetotellurics for such purposes. In this numerical investigation, we analyze to what extent inversion results based on AMT and RMT monitoring data can be improved by (1) time-lapse difference inversion; (2) incorporation of statistical information about the expected model update (i.e., the model regularization is based on a geostatistical model); (3) using alternative model norms to quantify temporal changes (i.e., approximations of l1 and Cauchy norms using iteratively reweighted least-squares), (4) constraining model updates to predefined ranges (i.e., using Lagrange Multipliers to only allow either increases or decreases of electrical resistivity with respect to background conditions). To do so, we consider a simple illustrative model and a more realistic test case related to seawater intrusion. The results are encouraging and show significant improvements when using time-lapse difference inversion with non l2 model norms. Artifacts that may arise when imposing compactness of regions with temporal changes can be suppressed through inequality constraints to yield models without oscillations outside the true region of temporal changes. Based on these results, we recommend approximate l1-norm solutions as they can resolve both sharp and smooth interfaces within the same model.
    Journal of Applied Geophysics 09/2012; 84:29–38. DOI:10.1016/j.jappgeo.2012.05.012 · 1.30 Impact Factor