Aquifer Characterization in the Blue Ridge Physiographic Province Using Resistivity Profiling and Borehole Geophysics: Geologic Analysis

Seaton, William; Burbey, Thomas J.

doi:10.4133/jeeg5.3.45

Cited by 37 publications

(27 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The λ value (Equation ) relates the matrix to fracture hydraulic conductivity. The calibrated values of 0.0026–0.0032 (Table ) indicate that the fracture hydraulic conductivity is nearly 3 orders of magnitude greater than the matrix, which confirms what has been previously published regarding hydraulic testing at the site (Seaton and Burbey, , ). Finally, regarding the fracture skin (Equation ), the test results were not very sensitive to this particular parameter value and this confirms the fact that the short pumping period (early time drawdown) probably precludes us from calculating a reasonable fracture skin.…”

Section: Discussion Of Resultssupporting

confidence: 86%

“…This fault is one in a series of en echelon style faults, which trend southwest to northeast across the region and are associated with regional stress associated with the Blue Ridge Fault, which separates the Precambrian metamorphic rocks of the Blue Ridge from the underlying Paleozoic sedimentary formations (Seaton and Burbey, ). A complete geologic and hydrogeologic description of the site can be found in Seaton and Burbey (, ) and Burbey and Seaton ().…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of a hydraulically induced crystalline‐rock fracture

Burbey

Brandon

2016

Hydrological Processes

Self Cite

View full text Add to dashboard Cite

Hydraulic fracturing has become an important technique for enhancing the permeability of hydrocarbon source rocks and increasing aquifer transmissivity in many hard rock environments where natural fractures are limited, yet little is known about the nature or behaviour of these hydraulically induced fractures as conduits to flow and transport. We propose that these fractures tend to be smooth based on observed hydraulic and transport behaviour. In this investigation a multi‐faceted approach was used to quantify the properties and characteristics of an isolated hydraulically induced fracture in crystalline rocks. Packers were used to isolate the fracture that is penetrated by two separate observation wells located approximately 33 m apart. A series of aquifer tests and an induced gradient tracer test were performed to better understand the nature of this fracture. Aquifer test results indicate that full recovery is slow because of the overall low permeability of the crystalline rocks. Drawdown tests indicate that the fracture has a transmissivity of 1–2 m2/day and a specific storage on the order of 2–9 × 10−7/m. Analysis of a potassium–bromide tracer test break through curve shows classic Fickian behaviour with minimal tailing analogous to parallel plate flow. Virtually all of the tracer was recovered, and the breakthrough curve dilution indicates that the swept area is only about 11% of a radial flow field and the estimated aperture is ≤0.5 mm, which implies a narrow linear flow region. These outcomes suggest that transport within these hydraulically induced ‘smooth’ fractures in crystalline rocks is rapid with minimal mixing, small local velocity fluctuations and no apparent diffusion into the host rock or secondary fractures. Copyright © 2016 John Wiley & Sons, Ltd.

show abstract

Section: Discussion Of Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Characterization of a hydraulically induced crystalline‐rock fracture

Burbey

Brandon

2016

Hydrological Processes

Self Cite

View full text Add to dashboard Cite

show abstract

“…Electrical imaging (or tomography) surveys are now widely used in diverse engineering and environmental problems, hydrological, agricultural, mineral and even hydrocarbon exploration (Dahlin, 1996;Seaton and Burbey, 2000;Bauman, 2005). Most surveys have been carried out using the traditional arrays such as the Wenner, Schlumberger, pole-pole, dipole-dipole and pole-dipole arrays.…”

Section: Introductionmentioning

confidence: 99%

Fast computation of optimized electrode arrays for 2D resistivity surveys

Loke¹,

Wilkinson

Chambers

2010

Computers & Geosciences

View full text Add to dashboard Cite

Four different methods to automatically select an optimal set of array configurations that gives the maximum resolution of the subsurface with a limited number of measurements for 2D electrical imaging surveys were tested. The first method (CR method) directly calculates the change in the model resolution for each new array added to the base data set, and uses this to select array configurations that gave the maximum model resolution. However this method is the slowest. The computer code for calculating the rank one updates used by the CR method was optimized to reduce the computer time by about eighty times. The sequence of calculations needed was modified to reduce the traffic between the computer main memory and the CPU registers. Further code optimizations were made to take advantage of the parallel processing capabilities of modern CPUs. The second (ETH) and third (BGS) methods use approximations based on the sensitivity values to estimate the change in the model resolution matrix.The ETH and BGS methods respectively use the first and second power of the sensitivity values to calculate an approximation of the model resolution. Both methods are about an order of magnitude faster than the CR method. The results obtained by the BGS method are significantly better than the ETH method, and it approaches that of the CR method. The fourth method (BGS-CR) uses a combination of the BGS and CR methods. It produces results that are almost identical to the CR method but it is several times faster. The different methods were tested using data from synthetic models and field surveys. The 2 models obtained from the inversion of the data sets generated by the four different methods confirm that the models generated by the CR method have the best resolution, followed by the BGS-CR, BGS and ETH methods.

show abstract

“…ERI/ERT surveys are now widely used in diverse fields of hydrogeology, engineering, environment, archaeology, agroforestry, geotechnique and mineral exploration (e.g. DAHLIN, 1996;SEATON and BURBEY, 2000;BAUMAN, 2005). Obviously, the target resolution of surface and borehole surveys depends on: (1) the number and spacing of applied electrodes, (2) aspect ratio (borehole offset divided by length of electrode array), (3) electrode configurations and (4) the unknown subsurface resistivity structure (e.g.…”

Section: Introductionmentioning

confidence: 99%

2D Optimized Electrode Arrays for Borehole Resistivity Tomography and CO2 Sequestration Modelling

Hagrey

2011

Pure Appl. Geophys.

View full text Add to dashboard Cite

Modern optimization approaches for electrode configurations can significantly improve the resolution of 2.5D resistivity imaging surveys. This study presents a brief review of the 2.5D optimization approach, particularly for borehole-borehole surveys with applications for mapping virtual CO 2 plumes sequestrated in deep saline reservoir formations. The applied algorithm searches for arrays that maximize the spatial resolution of the survey among the comprehensive dataset of best possible spatial resolution (i.e. least temporal resolution). A main goal of this study is to increase the temporal resolution of ERT boreholeborehole surveys by selecting optimized electrode configurations in order to minimise the required data acquisition time while sustaining a high spatial resolution. The optimized dataset starts with a base set and is iteratively increased based on the model resolution matrix (R) until the required number of data points is achieved. Among four different optimization methods, the compare R (CR) method of the best resolution is applied to directly calculate R for each new array added to the optimized dataset. Small optimized datasets generated by this technique are only \5% of their comprehensive sets but of an average resolution ratio (R r ) of[0.95 (i.e. almost the same resolution). With increasing the size of the optimized dataset (during its generation), the algorithm progressively enhances R r values in the central interwell region (of low sensitivities and low resolution) far higher than in the near borehole region (of high sensitivities). Also the inverted tomogram reliability increases by increasing the optimized data size. Briefly, the optimized arrays improve the resolution in the interwell region which is commonly low in borehole-borehole ERT studies. The inverted output model is evaluated quantitatively using the model difference relative to the input model. The results reflect the common smearing effects and artefacts of varying degrees that overpredict volumes, underpredict magnitudes and blur boundaries of the target anomalies. This input model is a synthetic resistivity model that was used to generate synthetic (forward solution) data used during the inversion. Applications on synthetic CO 2 models show that the mapping resolution for optimized datasets is better than that for other highly resolving arrays of the same number of data points. Problems of smeared boundaries and thin layers are less visible in the optimized array than in the other highly resolving arrays.

show abstract

Aquifer Characterization in the Blue Ridge Physiographic Province Using Resistivity Profiling and Borehole Geophysics: Geologic Analysis

Cited by 37 publications

References 20 publications

Characterization of a hydraulically induced crystalline‐rock fracture

Characterization of a hydraulically induced crystalline‐rock fracture

Fast computation of optimized electrode arrays for 2D resistivity surveys

2D Optimized Electrode Arrays for Borehole Resistivity Tomography and CO2 Sequestration Modelling

Contact Info

Product

Resources

About