Hydraulic anisotropy characterization of pneumatic-fractured sediments using azimuthal self potential gradient

2009 ◽  
Vol 103 (3-4) ◽  
pp. 134-144 ◽  
Author(s):  
DeBonne N. Wishart ◽  
Lee D. Slater ◽  
Deborah L. Schnell ◽  
Gregory C. Herman
Keyword(s):  
Potential Gradient ◽  
Hydraulic Anisotropy ◽  
Self Potential

Marine self-potential gradient exploration of the continental margin

Geophysics ◽  
2005 ◽  
Vol 70 (5) ◽  
pp. G109-G118 ◽  
Author(s):  
Graham Heinson ◽  
Antony White ◽  
David Robinson ◽  
Nader Fathianpour
Keyword(s):  
Mineral Exploration ◽  
South Australia ◽  
Potential Gradient ◽  
Ocean Waves ◽  
Horizontal Gradient ◽  
Reconstruction Method ◽  
Source Regions ◽  
Image Reconstruction Method ◽  
Numerical Finite Element ◽  
Self Potential

The self-potential (SP) method for mineral exploration is seldom used on land, primarily because of electrode noise problems and nonunique interpretations. Marine measurements of the horizontal gradient of the SP field, on the other hand, are relatively simple to make with an array of electrodes towed behind a ship. With low ship speeds of 5 to 10 km/hour, dense spatial sampling (∼1 m) can be obtained with resolution of better than 1 μV/m. In this paper we report on gradient SP data recorded on the continental shelf of South Australia by a horizontal array of towed electrodes approximately 20 m above the seafloor. Ocean waves and swells with periods of 5 to 15 s yielded large amplitude signals ±20 μV/m, but subseafloor mineralization produced SP gradient anomalies of ±50 μV/m and widths of 2 km or more in a number of parallel traverses. Integrating the observed SP gradients along each line delineated SP anomalies of amplitude up to −100 mV. Self-potential and magnetic anomaly data show limited spatial correlation and have different wavelengths, suggesting that SP sources are probably nonferrous minerals, such as graphite, and are deeper than the magnetic sources. The source of the SP signal is probably reduction-oxidation (redox) potential ([Formula: see text]) variations across a conducting body below the seafloor. We approximate the source as being two dimensional and find the most probable locations of line sources by an image reconstruction method. Numerical finite-element modeling of more realistic source regions suggests shallow, easterly dipping (∼15°) conductors of 1 Ω.m in the uppermost 2 km.

scholarly journals Fusion of Remote Sensing and Applied Geophysics for Sinkholes Identification in Tabular Middle Atlas of Morocco (the Causse of El Hajeb): Impact on the Protection of Water Resource

Resources ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 51
Author(s):  
Anselme Muzirafuti ◽  
Mustapha Boualoul ◽  
Giovanni Barreca ◽  
Abdelhamid Allaoui ◽  
Hmad Bouikbane ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Geophysical Methods ◽  
Remote Sensing Data ◽  
Resistivity Tomography ◽  
Geophysical Surveys ◽  
Middle Atlas ◽  
Karst Landforms ◽  
Water Springs ◽  
Self Potential

The Causse of El Hajeb belongs to the Tabular Middle Atlas (TMA), in which thousands of karst landforms have been identified. Among them, collapse dolines and dissolution sinkholes have been highlighted as a source of environmental risks and geo-hazards. In particular, such sinkholes have been linked to the degradation of water quality in water springs located in the junction of the TMA and Saïss basin. Furthermore, the developments of collapse dolines in agricultural and inhabited areas enhance the risk of life loss, injury, and property damage. Here, the lack of research on newly formed cavities has exacerbated the situation. The limited studies using remote sensing or geophysical methods to determine the degree of karstification and vulnerability of this environment fail to provide the spatial extent and depth location of individual karst cavities. In order to contribute to the effort of sinkhole risk reduction in TMA, we employed remote sensing and geophysical surveys to integrate electrical resistivity tomography (ERT) and self-potential (SP) for subsurface characterization of four sinkholes identified in the Causse of El Hajeb. The results revealed the existence of sinkholes, both visible and non-accessible at the surface, in carbonate rocks. The sinkholes exhibited distinct morphologies, with depths reaching 35 m. Topography, geographic coordinates and land cover information extracted on remote sensing data demonstrated that these cavities were developed in depressions in which agricultural activities are regularly performed. The fusion of these methods benefits from remote sensing in geophysical surveys, particularly in acquisition, georeferencing, processing and interpretation of geophysical data. Furthermore, our proposed method allows identification of the protection perimeter required to minimize the risks posed by sinkholes.

Comparison between permeability anisotropy and elasticity anisotropy of reservoir rocks

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 230-240 ◽  
Author(s):  
Patrick N. J. Rasolofosaon ◽  
Bernard E. Zinszner
Keyword(s):  
Elastic Anisotropy ◽  
Rock Permeability ◽  
X Ray ◽  
Reservoir Rocks ◽  
Invasion Fronts ◽  
Hydraulic Anisotropy ◽  
Elasticity Tensors ◽  
Complete Set ◽  
Seismic Measurements

We developed new experimental and theoretical tools for the measurement and the characterization of arbitrary elasticity tensors and permeability tensors in rocks. They include an experimental technique for the 3‐D visualization of hydraulic invasion fronts in rock samples by monitoring the injection of salt solutions by X‐ray tomography, and a technique for inverting the complete set of the six coefficients of the permeability tensor from invasion front images. In addition, a technique for measuring the complete set of the 21 elastic coefficients, a technique allowing the identification and the orientation in the 3‐D space of the symmetry elements (planes, axes), and a technique for approximating the considered elastic tensor by a tensor of simpler symmetry with the quantification of the error induced by such an approximation have been developed. We apply these tools to various types of reservoir rocks and observed quite contrasted behaviors. In some rocks, the elastic anisotropy and the hydraulic anisotropy are closely correlated, for instance in terms of the symmetry directions. This is the case when elastic anisotropy and hydraulic anisotropy share the same cause (e.g., layering, fractures). In contrast, in some other rocks, hydraulic properties and elastic properties are clearly uncorrelated. These results highlight the challenge we have to face in order to estimate the rock permeability and to monitor the fluid flow from seismic measurements in the field.

Self-potential method applied to the characterization of a clogged porous medium

2014 ◽  
pp. 1467-1472
Author(s):  
S Taoudiat ◽  
N-D Ahfir ◽  
H-Q Wang ◽  
A Jardani ◽  
J-P Dupont
Keyword(s):  
Porous Medium ◽  
Potential Method ◽  
Self Potential

scholarly journals Improved Characterization of DNAPL Source Zones via Sequential Hydrogeophysical Inversion of Hydraulic‐Head, Self‐Potential and Partitioning Tracer Data

2020 ◽  
Vol 56 (8) ◽  
Author(s):  
Xueyuan Kang ◽  
Amalia Kokkinaki ◽  
Peter K. Kitanidis ◽  
Xiaoqing Shi ◽  
André Revil ◽  
...  
Keyword(s):  
Hydraulic Head ◽  
Source Zones ◽  
Partitioning Tracer ◽  
Self Potential

scholarly journals Characteristics of a fracture network surrounding a hydrothermally altered shear zone from geophysical borehole logs

Solid Earth ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 829-854
Author(s):  
Eva Caspari ◽  
Andrew Greenwood ◽  
Ludovic Baron ◽  
Daniel Egli ◽  
Enea Toschini ◽  
...  
Keyword(s):  
Shear Zone ◽  
Damage Zone ◽  
Fracture Network ◽  
Core Material ◽  
Petrophysical Properties ◽  
Brittle Deformation ◽  
Borehole Radar ◽  
Borehole Logs ◽  
Self Potential

Abstract. Hydrothermally active and altered fault/shear zones in crystalline rocks are of practical importance because of their potential similarities with petrothermal reservoirs and exploitable natural hydrothermal systems. The petrophysical and hydraulic characterization of such structures is therefore of significant interest. Here, we report the results of corresponding investigations on a prominent shear zone of this type located in the crystalline Aar massif of the central Swiss Alps. A shallow borehole was drilled, which acutely intersects the core of the shear zone and is entirely situated in its surrounding damage zone. The focus of this study is a detailed characterization of this damage zone based on geophysical borehole measurements. For this purpose, a comprehensive suite of borehole logs, comprising passive and active nuclear, full-waveform sonic, resistivity, self-potential, optical televiewer, and borehole radar data, was collected. The migrated images of the borehole radar reflection data together with the optical televiewer data reveal a complicated network of intersecting fractures in the damage zone. Consequently, the associated petrophysical properties, notably the sonic velocities and porosities, are distinctly different from intact granitic formations. Cluster analyses of the borehole logs in combination with the structural interpretations of the optical televiewer data illustrate that the variations in the petrophysical properties are predominantly governed by the intense brittle deformation. The imaged fracture network and the high-porosity zones associated with brittle deformation represent the main flow pathways. This interpretation is consistent with the available geophysical measurements as well as the analyses of the retrieved core material. Furthermore, the interpretation of the self-potential and fluid resistivity log data suggests a compartmentalized hydraulic behavior, as evidenced by inflows of water into the borehole from different sources, which is likely to be governed by the steeply dipping structures.

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