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The Use of Ground Penetrating Radar Data in the Development of Facies-Based Hydrogeologic Models Rosemary Knight, Elliot Grunewald, Richelle Allen-King, Stephen Moysey, David Gaylord
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Groundwater flow & transport models: –Evaluate/manage drinking water supply –Evaluate groundwater susceptibility to contamination –Estimate societal/ecological impacts of contamination –Assign risk to prioritize remediation needs
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Groundwater flow & transport models: –Evaluate/manage drinking water supply –Evaluate groundwater susceptibility to contamination –Estimate societal/ecological impacts of contamination –Assign risk to prioritize remediation needs Incorporating heterogeneous distributions of subsurface properties authentically will reduce uncertainty for all of these!
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Groundwater flow & transport models: –Evaluate/manage drinking water supply –Evaluate groundwater susceptibility to contamination –Estimate societal/ecological impacts of contamination –Assign risk to prioritize remediation needs but we should do so in a way that allows us to quantify uncertainty
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10’s of cm’s to 100’s of meters ?
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? ? ? ?
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?
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12 m 52 m 10 m Knoll et al. (1988)
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geophysical properties
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hydrogeologic information transform
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Develop a model of large-scale architecture.
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depth 20 meters TxRx change in dielectric properties 11 22
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Sandy Point spit, Alberta (Smith and Jol, 1992)
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Develop a large-scale model using radar facies.
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Radar facies are defined by patterns shapes, bounding surfaces internal “texture” Smith and Jol (1992) Develop a large-scale model using radar facies.
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Sandy Point spit, Alberta (Smith and Jol, 1992) radar facies 1 radar facies 2 radar facies 3
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Sandy Point spit, Alberta (Smith and Jol, 1992) radar facies 1 radar facies 2 radar facies 3 Radar facies = lithofacies/hydrofacies?
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Radar facies are defined by: patterns Use neural networks for pattern recognition.
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Radar facies are defined by: patterns Use neural networks for pattern recognition. More efficient Allows us to generate stochastic models & quantify uncertainty. Moysey, Knight, Caers, Allen-King, 2002 Moysey, Knight, Jol, 2005
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Step #1- training (i.e. calibration) with a known data set: Neural Networks: Lithofacies Recognition wells, cores
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Step #1- training (i.e. calibration) with a known data set: radar attributes (e.g., reflection dip, continuity) facies probabilities P(F=f 1 ) = 0 P(F=f 2 ) = 1 P(F=f 3 ) = 0 Neural Networks: Lithofacies Recognition InputsWeights and combinations wells, cores
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Neural Networks: Lithofacies Estimation Neural network used to assign facies probabilities at each location based on local patterns. radar attributes (e.g., reflection dip, continuity) facies probabilities P(F=f 1 )=.7 P(F=f 2 )=.2 P(F=f 3 )=.1
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Lithofacies Probabilities 01 Facies 1 Facies 4Facies 3 Facies 2 Probabilities allow us to include uncertainty in modeling
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Use neural net to interpret facies assuming that training remains valid for all other data sets
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Use neural net to interpret facies assuming that training remains valid for all other data sets Can we develop training (classification schemes) that are transferable?
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Use neural net to interpret facies assuming that training remains valid for all other data sets Can we develop training (classification schemes) that are transferable? Is there a characteristic radar signature associated with specific depositional environments?
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Conditional Facies Realizations Radar Data Facies (NN) Facies 1 Facies 2 Direct Facies Observations (e.g., well data) 0 1 GEOSTATISTICS Use direct observations + radar data to develop models of large-scale architecture.
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Application - Borden Groundwater Research Site
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? ? ? ?
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? 050100150200250m Can we use radar data to fill in between and beyond core samples?
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450 MHz radar data: 17 NS lines, 17 EW lines; depth ~3m 12 core samples in top 1.5 m
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Lithofacies: Soil, Fine-Grained Planar Cross-Stratified (FPXS), Distinct Plane Laminated (DPL), Massive Coarse-Grained (MCG), Massive Fine-Grained (MFG), Faint Plane Laminated (FPL), Low-Angle Planar Cross-Stratified (LPXS), High-Angle Planar Cross-Stratified (HPXS), Deformed Sand (DS), Cross-Stratified Sand (XSS), Complexly Cross-Stratified Sand (CPXS), Laminated Silt (ZM).
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Lithofacies: Soil, Fine-Grained Planar Cross-Stratified (FPXS), Distinct Plane Laminated (DPL), Massive Coarse-Grained (MCG), Massive Fine-Grained (MFG), Faint Plane Laminated (FPL), Low-Angle Planar Cross-Stratified (LPXS), High-Angle Planar Cross-Stratified (HPXS), Deformed Sand (DS), Cross-Stratified Sand (XSS), Complexly Cross-Stratified Sand (CPXS), Laminated Silt (ZM).
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Lithofacies: Soil, Fine-Grained Planar Cross-Stratified (FPXS), Distinct Plane Laminated (DPL), Massive Coarse-Grained (MCG), Massive Fine-Grained (MFG), Faint Plane Laminated (FPL), Low-Angle Planar Cross-Stratified (LPXS), High-Angle Planar Cross-Stratified (HPXS), Deformed Sand (DS), Cross-Stratified Sand (XSS), Complexly Cross-Stratified Sand (CPXS), Laminated Silt (ZM).
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Lithofacies: Soil, Fine-Grained Planar Cross-Stratified (FPXS), Distinct Plane Laminated (DPL), Massive Coarse-Grained (MCG), Massive Fine-Grained (MFG), Faint Plane Laminated (FPL), Low-Angle Planar Cross-Stratified (LPXS), High-Angle Planar Cross-Stratified (HPXS), Deformed Sand (DS), Cross-Stratified Sand (XSS), Complexly Cross-Stratified Sand (CPXS), Laminated Silt (ZM).
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Lithofacies: Soil, Fine-Grained Planar Cross-Stratified (FPXS), Distinct Plane Laminated (DPL), Massive Coarse-Grained (MCG), Massive Fine-Grained (MFG), Faint Plane Laminated (FPL), Low-Angle Planar Cross-Stratified (LPXS), High-Angle Planar Cross-Stratified (HPXS), Deformed Sand (DS), Cross-Stratified Sand (XSS), Complexly Cross-Stratified Sand (CPXS), Laminated Silt (ZM).
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Radar Data and Cores Visualized with Geoprobe® To explore the 3D continuity of core lithologies and radar horizons To correlate lithological data with radar reflections
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Core depth converted to time using velocity of 0.69 m/ns N Time (ns) Distance (m) Core Data Only
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17 north-south GPR lines imported as data cube Frequency: 450 MHz Length: 20 m Spacing: 1/8 m Radar Data with Cores
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Moving through the 3D Volume
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“Seed point” specified on potential horizon (max or min) EzTracker tool explores away from seed for similar waveform Identifying and Tracking Horizons
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Horizon 1 interpreted as base of soil layer Horizon 2 interpreted as base of X-bedded sand Horizon 3 interpreted as base of massive/laminated zone Three Main Horizons Identified 1 2 3
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Training the Neural Network Chose four descriptive facies based on core data and horizons Trained neural net using facies map for a single profile After training neural net used to classify entire set of radar data
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Neural Network Classification Results maximum likelihood Substantial agreement of classifications with cores and horizons Soil layer and Cross-stratified units particularly well-identified Less continuous classifications of the deep half of the image may reflect lateral variation observed in cores at depth Geoprobe Horizons
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Neural Network Classification Results maximum likelihood Substantial agreement of classifications with cores and horizons Soil layer and Cross-stratified units particularly well-identified Less continuous classifications of the deep half of the image may reflect lateral variation observed in cores at depth Geoprobe Horizons
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12 m 52 m 10 m Knoll et al. (1988)
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