2-D and 3-D resistivity image reconstruction using crosshole data

Geophysics ◽  
1992 ◽  
Vol 57 (10) ◽  
pp. 1270-1281 ◽  
Author(s):  
Hiromasa Shima
Keyword(s):  
Field Test ◽  
Numerical Models ◽  
Electrical Potential ◽  
Nonlinear Least Squares ◽  
Three Dimensions ◽  
Inversion Method ◽  
Good Resolution ◽  
Inversion Algorithm ◽  
Linear Inversion ◽  
Resistivity Model

Theoretical changes in the distribution of electrical potential near subsurface resistivity anomalies have been studied using two resistivity models. The results suggest that the greatest response from such anomalies can be observed with buried electrodes, and that the resistivity model of a volume between boreholes can be accurately reconstructed by using crosshole data. The distributive properties of crosshole electrical potential data obtained by the pole‐pole array method have also been examined using the calculated partial derivative of the observed apparent resistivity with respect to a small cell within a given volume. The results show that for optimum two‐dimensional (2-D) and three‐dimensional (3-D) target imaging, in‐line data and crossline data should be combined, and an area outside the zone of exploration should be included in the analysis. In this paper, the 2-D and 3-D resistivity images presented are reconstructed from crosshole data by the combination of two inversion algorithms. The first algorithm uses the alpha center method for forward modeling and reconstructs a resistivity model by a nonlinear least‐squares inversion. Alpha centers express a continuously varying resistivity model, and the distribution of the electrical potential from the model can be calculated quickly. An initial general model is determined by the resistivity backprojection technique (RBPT) prior to the first inversion step. The second process uses finite elements and a linear inversion algorithm to improve the resolution of the resistivity model created by the first step. Simple 2-D and 3-D numerical models are discussed to illustrate the inversion method used in processing. Data from several field studies are also presented to demonstrate the capabilities of using crosshole resistivity exploration techniques. The numerical experiments show that by using the combined reconstruction algorithm, thin conductive layers can be imaged with good resolution for 2-D and 3-D cases. The integration of finite‐element computations is shown to improve the image obtained by the alpha center inversion process for 3-D applications. The first field test uses horizontal galleries to evaluate complex 2-D features of a zinc mine. The second field test illustrates the use of three boreholes at a dam site to investigate base rock features and define the distribution of an altered zone in three dimensions.

Inversion of reflection times in three dimensions

Geophysics ◽  
1981 ◽  
Vol 46 (7) ◽  
pp. 972-983 ◽  
Author(s):  
Håvar Gjøystdal ◽  
Bjørn Ursin
Keyword(s):  
Real Data ◽  
Normal Incidence ◽  
Thin Layers ◽  
Three Dimensions ◽  
Good Resolution ◽  
Inversion Algorithm ◽  
Linear Inversion ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Interval Velocities

When reflection data are available from a grid of crossing seismic lines, it is possible to construct normal incidence time maps from interpreted stacked sections and then apply three‐dimensional (3-D) ray‐tracing techniques following the normal‐incidence raypaths down to the various reflectors. The main disadvantage of this well‐known “time map migration” procedure is that interval velocities must be known a priori, and they must be estimated in advance by some approximate method. A technique is presented here which combines the above procedure with an inversion algorithm, providing direct calculations of interval velocities from the additional use of nonzero offset traveltime observations. A generalized linear inversion scheme is used, making possible a complete calculation of interval velocities and reflection interfaces, the latter represented by bicubic spline functions. To test the method in practice, we have applied it to (1) synthetic data generated from a constructed model, and (2) real data obtained from marine seismic sections. In the latter case, velocities and reflector depths obtained were compared to those obtained directly from a well log in the area. These results show a reasonably good resolution for layers that are not too deep relative to the shot/receiver offsets used. For deep and/or thin layers, the results are not satisfactory. This indicates the general limitation of seismic reflection data to resolve interval velocity, even in the presence of horizontally layered structure.

Traveltime inversion for the geometry of aquifer lithologies

Geophysics ◽  
1996 ◽  
Vol 61 (6) ◽  
pp. 1728-1737 ◽  
Author(s):  
David W. Hyndman ◽  
Jerry M. Harris
Keyword(s):  
Central Valley ◽  
Hydraulic Testing ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Inversion Method ◽  
Limited Information ◽  
Inversion Algorithm ◽  
Traveltime Tomography ◽  
Tomographic Inversions ◽  
Better Than

Crosswell traveltime tomography can provide detailed descriptions of the geometry and seismic slowness of lithologic zones in aquifers and reservoirs. Traditional tomographic inversions that estimate a smooth slowness field to match traveltime data, provide limited information about the dominant scale of subsurface heterogeneity. We demonstrate an alternative method, called the multiple population inversion (MPI), that co‐inverts traveltimes between multiple well pairs to identify the spatial distribution of a small number of slowness populations. We also compare the MPI with the split inversion method (SIM) that was recently introduced to address the same problem. The lithologies and hydraulic parameters for these populations can then be determined from core data and hydraulic testing. The MPI iteratively assigns pixels to a small number of slowness populations based on the histogram of slowness residuals. By constraining the number of slowness values, this method is less susceptible to inversion artifacts, such as those related to slight variations in ray coverage, and can resolve finer scale sedimentary structures better than methods that smooth the slowness field. We demonstrate the MPI in two dimensions with a synthetic aquifer and in three dimensions with the Kesterson aquifer in the central valley of California. In both cases, the constrained inversion algorithm converges to an equal or smaller average traveltime residual than obtained with unconstrained‐value tomography. The MPI accurately images the dominant lithologies of the synthetic aquifer and provides a geologically reasonable image of the Kesterson aquifer.

Refinements to the linear velocity inversion theory

Geophysics ◽  
1984 ◽  
Vol 49 (2) ◽  
pp. 112-118 ◽  
Author(s):  
Frank G. Hagin ◽  
Jack K. Cohen
Keyword(s):  
Synthetic Data ◽  
Scattered Wave ◽  
Scattering Data ◽  
Inversion Method ◽  
Impedance Change ◽  
Inversion Algorithm ◽  
Linear Inversion ◽  
Velocity Inversion ◽  
Linear Algorithm ◽  
Inversion Theory

The linear inversion method presented by Cohen and Bleistein in 1979 gives seriously degraded results when large reflectors are encountered. Obviously there is an irrecoverable loss of information when such a linear algorithm is applied to a nonlinear world. However, in many cases, excellent results can be achieved by suitable postprocessing of the output of the basic linear inversion algorithm. Although a certain degree of helpful postprocessing can be and has been performed by straightforward consideration of the linearization process, we present here a substantially improved postprocessing algorithm. The basis for these improvements is a more accurate scattering model due to Lahlou et al where, among other things, a WKB analysis of the wave equation led to a much more accurate accounting of the geometric spreading of the scattered wave. These notions plus an effective use of traveltime are used in the new algorithm to improve both the estimate of the reflector locations and the estimate of amplitude (velocity or acoustic impedance) change across the reflectors. The basic idea is to insert this idealized scattering data into the original linear algorithm, and then use the result of this computation as a guide in the interpretation of the numerical output of the algorithm. We demonstrate the result of computer implementation of this algorithm on synthetic data, with and without noise, and verify that the postprocessing algorithm produces dramatically improved reflector locations and speed estimates. Moreover, the new algorithm adds only very modest cost to the basic processing, which is, in turn, very competitive in cost to other multidimensional algorithms.

Source signature determination from ministreamer data

Geophysics ◽  
1994 ◽  
Vol 59 (8) ◽  
pp. 1261-1269 ◽  
Author(s):  
Martin Landrø ◽  
Jan Langhammer ◽  
Roger Sollie ◽  
Losse Amundsen ◽  
Eivind Berg
Keyword(s):  
Point Sources ◽  
Inversion Method ◽  
Far Field ◽  
Nonlinear Inversion ◽  
Inversion Algorithm ◽  
Linear Inversion ◽  
Air Bubble ◽  
Air Gun ◽  
Error Energy ◽  
Effective Source

Two methods for estimating the pressure wavefield generated by a marine airp‐gun array are tested. Data have been acquired at a ministreamer located below the source array. Effective source signatures for each air gun are estimated. In the first method a nonlinear inversion algorithm is used, where the forward modeling scheme is based upon a physical modeling of the air bubble generated by each air gun. In the second method a linear inversion method is used, with the assumption that the physics in the problem can be described by the acoustic wave equation with explosive point sources as the driving term. From the estimated effective source signatures, far‐field signatures have been calculated for both methods and compared with measured far‐field signatures. The error energy between the measured and estimated far‐field signatures was approximately 8 percent for both methods.

scholarly journals Andesite prospect at West Sungkai of North Lampung: Its distribution based on electrical resistivity tomography

2021 ◽  
Vol 882 (1) ◽  
pp. 012086
Author(s):  
R. M. Antosia ◽  
Mustika ◽  
I. A. Putri ◽  
S. Rasimeng ◽  
O. Dinata
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Research Area ◽  
Inversion Method ◽  
Reserve Estimation ◽  
Linear Inversion ◽  
Resistivity Tomography ◽  
Resistivity Model ◽  
Subsurface Resistivity ◽  
2D And 3D

Abstract Infrastructure construction made andesite’s demand has increased, particularly in Lampung Province. In this research, its distribution in West Sungkai of North Lampung is mapped based on Electrical Resistivity Tomography (ERT) data from 6 lines, each of them was 186 m in length. Due to its excellent vertical resolution, Wenner configuration is performed. The research area is part of Quarter Holocene Volcanic (Qhv) formation. Lajur Barisan members consist of volcanic breccia, lava, and andesite-basalt tuff; thus, resistivity modeling is built within this aisle. Subsurface resistivity model has been created using the non-linear inversion method with promising low error at the third to fifth iterations, which marks an acceptable value. Using 2D and 3D ERT modeling, it is estimated that there are three mains of rocks based on their resistivity value: sandy tuff with 65 – 212 Ω m; tuff with 212 – 655 Ω m; and andesite with resistivity more than 655 Ω m. Andesite within this area is likely lava andesite which spread from the middle to the West and north. It is located at 5 – 35 m in depths with the reserve estimation of andesite is about 1.65 million tons.

scholarly journals The strain-generated electrical potential in cartilaginous tissues: a role for piezoelectricity

2021 ◽  
Vol 13 (1) ◽  
pp. 91-100
Author(s):  
Philip Poillot ◽  
Christine L. Le Maitre ◽  
Jacques M. Huyghe
Keyword(s):  
Physiological Response ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Electrical Potential ◽  
Evidence Base ◽  
Piezoelectric Response ◽  
Mechanical Forces ◽  
Streaming Potentials ◽  
Cartilaginous Tissues ◽  
Electrical Potentials

AbstractThe strain-generated potential (SGP) is a well-established mechanism in cartilaginous tissues whereby mechanical forces generate electrical potentials. In articular cartilage (AC) and the intervertebral disc (IVD), studies on the SGP have focused on fluid- and ionic-driven effects, namely Donnan, diffusion and streaming potentials. However, recent evidence has indicated a direct coupling between strain and electrical potential. Piezoelectricity is one such mechanism whereby deformation of most biological structures, like collagen, can directly generate an electrical potential. In this review, the SGP in AC and the IVD will be revisited in light of piezoelectricity and mechanotransduction. While the evidence base for physiologically significant piezoelectric responses in tissue is lacking, difficulties in quantifying the physiological response and imperfect measurement techniques may have underestimated the property. Hindering our understanding of the SGP further, numerical models to-date have negated ferroelectric effects in the SGP and have utilised classic Donnan theory that, as evidence argues, may be oversimplified. Moreover, changes in the SGP with degeneration due to an altered extracellular matrix (ECM) indicate that the significance of ionic-driven mechanisms may diminish relative to the piezoelectric response. The SGP, and these mechanisms behind it, are finally discussed in relation to the cell response.

scholarly journals Fengyun Meteorological Satellite Products for Earth System Science Applications

2021 ◽  
Author(s):  
Di Xian ◽  
Peng Zhang ◽  
Ling Gao ◽  
Ruijing Sun ◽  
Haizhen Zhang ◽  
...  
Keyword(s):  
Data Sharing ◽  
Satellite Data ◽  
Prediction Models ◽  
Weather Forecasting ◽  
Numerical Models ◽  
Weather Prediction ◽  
Vegetation Indices ◽  
Open Data ◽  
Earth System ◽  
Inversion Algorithm

AbstractFollowing the progress of satellite data assimilation in the 1990s, the combination of meteorological satellites and numerical models has changed the way scientists understand the earth. With the evolution of numerical weather prediction models and earth system models, meteorological satellites will play a more important role in earth sciences in the future. As part of the space-based infrastructure, the Fengyun (FY) meteorological satellites have contributed to earth science sustainability studies through an open data policy and stable data quality since the first launch of the FY-1A satellite in 1988. The capability of earth system monitoring was greatly enhanced after the second-generation polar orbiting FY-3 satellites and geostationary orbiting FY-4 satellites were developed. Meanwhile, the quality of the products generated from the FY-3 and FY-4 satellites is comparable to the well-known MODIS products. FY satellite data has been utilized broadly in weather forecasting, climate and climate change investigations, environmental disaster monitoring, etc. This article reviews the instruments mounted on the FY satellites. Sensor-dependent level 1 products (radiance data) and inversion algorithm-dependent level 2 products (geophysical parameters) are introduced. As an example, some typical geophysical parameters, such as wildfires, lightning, vegetation indices, aerosol products, soil moisture, and precipitation estimation have been demonstrated and validated by in-situ observations and other well-known satellite products. To help users access the FY products, a set of data sharing systems has been developed and operated. The newly developed data sharing system based on cloud technology has been illustrated to improve the efficiency of data delivery.

scholarly journals Application of an Improved Ultrasound Full-Waveform Inversion in Bone Quantitative Measurement

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 260
Author(s):  
Meng Suo ◽  
Dong Zhang ◽  
Yan Yang
Keyword(s):  
Nonlinear Equations ◽  
Waveform Inversion ◽  
Optimal Solution ◽  
Inversion Method ◽  
Full Waveform Inversion ◽  
Inversion Algorithm ◽  
Elastic Wave Equation ◽  
Full Waveform ◽  
Ultrasonic Propagation ◽  
Joint Velocity

Inspired by the large number of applications for symmetric nonlinear equations, an improved full waveform inversion algorithm is proposed in this paper in order to quantitatively measure the bone density and realize the early diagnosis of osteoporosis. The isotropic elastic wave equation is used to simulate ultrasonic propagation between bone and soft tissue, and the Gauss–Newton algorithm based on symmetric nonlinear equations is applied to solve the optimal solution in the inversion. In addition, the authors use several strategies including the frequency-grid multiscale method, the envelope inversion and the new joint velocity–density inversion to improve the result of conventional full-waveform inversion method. The effects of various inversion settings are also tested to find a balanced way of keeping good accuracy and high computational efficiency. Numerical inversion experiments showed that the improved full waveform inversion (FWI) method proposed in this paper shows superior inversion results as it can detect small velocity–density changes in bones, and the relative error of the numerical model is within 10%. This method can also avoid interference from small amounts of noise and satisfy the high precision requirements for quantitative ultrasound measurements of bone.

scholarly journals Deep electrical resistivity tomography for the prospection of low- to medium-enthalpy geothermal resources

2019 ◽  
Vol 219 (3) ◽  
pp. 2056-2072
Author(s):  
A Carrier ◽  
F Fischanger ◽  
J Gance ◽  
G Cocchiararo ◽  
G Morelli ◽  
...  
Keyword(s):  
Electrical Potential ◽  
Bouguer Anomaly ◽  
Industrial Area ◽  
Gravity Models ◽  
Efficient Technology ◽  
Geothermal Resources ◽  
Reflection Seismic ◽  
Resistivity Model ◽  
Noise Data ◽  
Geoelectrical Methods

SUMMARY The growth of the geothermal industry sector requires innovative methods to reduce exploration costs whilst minimizing uncertainty during subsurface exploration. Until now geoelectrical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow-reaching prospecting methods commonly used in hydro-geophysical studies. We present a recent technology for geoelectrical prospection, and show how geoelectrical methods may allow the investigation of medium-enthalpy geothermal resources until about 1 km depth. The use of the new acquisition system, which is made of a distributed set of independent electrical potential recorders, enabled us to tackle logistics and noise data issues typical of urbanized areas. We acquired a 4.5-km-long 2-D geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a ∼700 m geothermal exploration well (Geo-01, Satigny) in the Greater Geneva Basin, Western Switzerland. To show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs. The processed resistivity model is consistent with the interpretation of the active-seismic data and density variations computed from the inversion of the residual Bouguer anomaly. The combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing Mesozoic geological units up to Palaeogene–Neogene units that can be used for medium-enthalpy geothermal exploitation. Our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth. This new cost-efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources.

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