Laterally constrained inversion for CSAMT data interpretation

Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun

doi:10.1016/j.jappgeo.2015.07.009

Cited by 19 publications

(6 citation statements)

References 32 publications

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“…CSAMT is a hybrid method progressively being used in geotechnical engineering 17 , 31 , 63 – 66 . It measures subsurface resistivity distribution of the earth’s electric and magnetic fields, mainly due to the time-dependent variations and the high-frequency electromagnetic waves artificially transmitted by non-polarization.…”

Section: Methodsmentioning

confidence: 99%

“…However, ERT can only assess the subsurface at shallow depths 32,62 . CSAMT, on the other hand, is becoming the most suitable and economical geophysical method to obtain detailed information of the subsurface at large depths 17,31,[63][64][65][66] . Resistivity is a function of rock porosity and, consequently, the degree of fracturing in the rock mass; it is also strongly controlled by other factors including rock type, mineral and water contents, joint fissures development, temperature, pressure and pore-water electrical conductivity (EC).…”

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confidence: 99%

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Evaluation of rock mass units using a non-invasive geophysical approach

Hasan,

Shang,

Meng

2023

Sci Rep

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Thorough and accurate assessment of rock mass units is important for development of engineering infrastructures and groundwater resources assessments. Rock mass units are widely evaluated by reliable geomechanical parameters namely rock quality designation (RQD) and rock core index (RCI). Conventionally, these parameters are acquired via an extensive number of geotechnical tests. Such tests, however, suffer efficiency for data coverage, cost, equipment and topographic constrictions, and hence cause ambiguity in geological models for a detailed evaluation of rock mass integrity. Conversely, geophysical surveys offer fast, more user-friendly, less invasive, more cost-effective and less time-consuming approach for geological investigations. The past research confirms a useful link between geophysical and geotechnical parameters. But, none of the past studies provides a suitable and generalized relation between these parameters which can reduce geotechnical model uncertainty mostly caused by inadequate data and subsurface heterogeneity. This paper proposes a meaningful and feasible method to obtain geomechanical parameters using a certain number of drillings and geophysical data of four different sites. Based on electrical resistivity obtained from electrical resistivity tomography (ERT) and controlled-source audio-frequency magneto telluric (CSAMT), this research provides the general and adaptable formulas for geotechnical parameter estimation and reduces geological model uncertainty for more detailed 2D/3D imaging of RQD and RCI covering the whole sites where even no drilling data exists. Thus, the investigated sites are assessed laterally and vertically along each geophysical profile via distinct value ranges of geological parameters for a thorough and reliable evaluation of rock mass units in highly heterogeneous setting. Our research reduces the ambiguity caused by structural heterogeneities and scarce data, fills the gap between inadequate well tests and the true geological models, and gives new insights into the rock mass units for proper engineering design and groundwater exploitation.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Evaluation of rock mass units using a non-invasive geophysical approach

Hasan,

Shang,

Meng

2023

Sci Rep

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“…The data processing was also similar to that in CSAMT [ 42 ]. The apparent resistivities were used to perform a laterally constrained inversion [ 43 , 44 ].…”

Section: Case Studiesmentioning

confidence: 99%

Insight into skywave theory and breakthrough applications in resource exploration

Xue

et al. 2021

National Science Review

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Skywave refers to the electromagnetic wave reflected or refracted from the ionosphere and propagate in the form of a guided wave between the ionosphere and the Earth's surface. Since the skywave can propagate over large distances, it has been widely used in long-distance communication. This paper explores and demonstrates the feasibility of skywave for deep resource and energy exploration at depths up to 10 km. Theoretical and technical advancements were accomplished in furthering the skywave applications. A new solution method based on Green's function has been developed to study skywave propagation in a fully coupled lithosphere-air-ionosphere full space model. The model allows one, for the first time, to study skywave distribution characteristics in the lithosphere containing inhomogeneity such as ore deposits or oil and gas reservoirs. This model also lays a foundation for skywave data processing and interpretation. On a parallel line, we have developed a multi-channel, broadband, low-noise, portable data acquisition system suitable for receiving skywave signals. Using the skywave field excited by a high-power fixed source located in the central China, actual field surveys have been carried out in some areas in China including the Biyang depression of Henan Province. The initial results appear encouraging – The interpreted resistivity models prove to be consistent with those of seismic exploration and known geological information, and the exploration cost is only about 1/4 to 1/10 of seismic surveys. These initial successful applications of the skywave theory lay a solid foundation for further verification of the new method.

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“…The two-and three-dimensional CSAMT inversions are presumed to reflect the real underground resistivity model, and the layer demarcation is still based on the speculation of the values of the model-calculated resistivity (CRM) (Xiong et al, 2019;Zonge & Hughes, 1991). Although the CSAMT interpretations are based on lateral and vertical resistivity distributions, the conceptual model still has difficulty accurately describing stratigraphic logs composed of underground layers (Esnault et al, 2014;McNeill, 1990McNeill, , 1991Ruo et al, 2015;Xepapadeas & Koundouri, 2004). Moreover, during the drilling operations, it is a challenging task to define layer contacts and thicknesses, especially in a complex geological area with numerous tectonic structures (faults, fractures, dikes etc.)…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, during the drilling operations, it is a challenging task to define layer contacts and thicknesses, especially in a complex geological area with numerous tectonic structures (faults, fractures, dikes etc.) (An & Di, 2010;He, 2018;Ruo et al, 2015). To solve this problem, most geophysicists have used additional methods to confirm the existence of an interesting underground structure, such as fracture zones and a water reservoir rock (WRR) (e.g.…”

Section: Introductionmentioning

confidence: 99%

A novel approach for water reservoir mapping using controlled source audio‐frequency magnetotelluric in Xingning area, Hunan Province, China

Kouadio

Liu

Malory

et al. 2023

Geophysical Prospecting

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Controlled source audio‐frequency magnetotelluric is frequently used in association with other geophysical methods, especially in complex geological areas to highlight geological structures such as water reservoir rock. Although it gives satisfactory results, combining several methods requires time and expense. In addition, despite this combination, several drilling locations proposed after geophysical investigations were inaccurate, resulting in many unsuccessful drillings. The latter occurs due to the difficulty to emphasize the fracture zones properly. To work around this problem, we proposed a novel approach called pseudostratigraphic to reduce the repercussion of unsuccessful drilled boreholes and to demarcate the water reservoir rock. The technique consists to discretize the resistivity of the inverted OCCAM2D model based on the true layer resistivities collected from the borehole log data (observed layers). The discrete resistivity model is known as the new resistivity model. It is used to generate the pseudostratigraphic log at each station by pseudo‐demarcating the thicknesses of the observed layers with a low margin of error. Moreover, the combination of multiple new resistivity models from different survey lines creates a three‐dimensional pseudostratigraphic map useful to emphasize the water reservoir rock. The pseudostratigraphic implementation is carried out in the Xingning area as a real‐world case study. The results show that the intersection of the main fault (F1) and the conductive zones (≤100 Ω m) indicates the potential water reservoir rock. Its thickness is estimated around 150–600 with an error equal to ± 7°m. Based on the three‐dimensional pseudostratigraphic map, the water found in the fracture zone located under the reservoir rock is considered much hotter due to the intense geothermal activity along F1, thereby making it a better place for hot water exploitation. Finally, the pseudostratigraphic technique could be an innovative and cheap strategy to find groundwater reservoirs in complex geological areas.

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Laterally constrained inversion for CSAMT data interpretation

Cited by 19 publications

References 32 publications

Evaluation of rock mass units using a non-invasive geophysical approach

Evaluation of rock mass units using a non-invasive geophysical approach

Insight into skywave theory and breakthrough applications in resource exploration

A novel approach for water reservoir mapping using controlled source audio‐frequency magnetotelluric in Xingning area, Hunan Province, China

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