Improvement in MRS parameter estimation by joint and laterally constrained inversion of MRS and TEM data

Geophysics ◽  
2012 ◽  
Vol 77 (4) ◽  
pp. WB191-WB200 ◽  
Author(s):  
Ahmad A. Behroozmand ◽  
Esben Auken ◽  
Gianluca Fiandaca ◽  
Anders Vest Christiansen
Keyword(s):  
Water Content ◽  
Joint Inversion ◽  
Synthetic Data ◽  
Clear Correlation ◽  
Model Parameters ◽  
Dc Resistivity ◽  
Borehole Data ◽  
Simultaneous Inversion ◽  
Transient Electromagnetic ◽  
Magnetic Resonance Sounding

We developed a new scheme for joint and laterally constrained inversion (LCI) of magnetic resonance sounding (MRS) data and transient electromagnetic (TEM) data, which greatly improves the estimation of the MRS model parameters. During the last few decades, electrical and electromagnetic methods have been widely used for groundwater investigation, but they suffer from some inherent limitations; for example, equivalent layer sequences. Furthermore, the water content information is only empirically correlated to resistivity of the formation. MRS is a noninvasive geophysical technique that directly quantifies the water content distribution from surface measurements. The resistivity information of the subsurface is obtained from a complementary geophysical method such as TEM or DC resistivity methods. The conventional inversion of MRS data assumes the resulting resistivity structure to be correct and considers a constant MRS kernel through the inversion. We found that this assumption may introduce an error to the forward modeling and consequently could result in erroneous parameter estimations in the inversion process. We investigated the advantage of TEM for the joint inversion compared to DC resistivity. A fast and numerically efficient MRS forward routine made it possible to invert the MRS and TEM data sets simultaneously along profiles. Furthermore, by application of lateral constraints on the model parameters, lateral smooth 2D model sections could be be obtained. The simultaneous inversion for resistivity and MRS parameters led to a more reliable and robust estimation of all parameters, and the MRS data diminished the range of equivalent resistivity models. We examined the approach through synthetic data and a field example in Denmark where good agreement with borehole data was demonstrated with clear correlation between the relaxation time [Formula: see text] and the grain size distribution of a sandy aquifer.

Combined Monitoring Methods for Potential Landslides Using MRS and TEM

2019 ◽  
Vol 24 (2) ◽  
pp. 225-236
Author(s):  
Tingting Lin ◽  
Xiaoxue Lin ◽  
Ling Wan ◽  
Shanshan Guan ◽  
Fei Teng
Keyword(s):  
Water Content ◽  
Pore Water Pressure ◽  
Joint Inversion ◽  
Water Pressure ◽  
Free Water ◽  
Depth Range ◽  
Monitoring Methods ◽  
Wet Season ◽  
Transient Electromagnetic ◽  
Magnetic Resonance Sounding

In this research study, the landslide events of Huangshan City in China's Anhui Province were monitored through the integration of two geophysical techniques: the magnetic resonance sounding (MRS) and transient electromagnetic (TEM) methods. The JLMRS-III system was used to determine the distributions of the free water in the strata and the MiniTEM system was utilized to image the subsurface electrical resistivity structures. Data acquisition was carried out on two planned survey lines during a wet season. A set of 15 measurements were completed using MRS array detection; a set of 44 measurements were completed using TEM method. The monitoring activities were repeatedly implemented before and after rainfall occurred. The results of water content information, relaxation time, and resistivity distributions were determined through joint inversion. Plots of the results clearly show the aquifer and resistivity structure of the study area. The monitoring data of displacement, pore-water pressure, and rainfall was collected to help differentiate the slip blocks, slip beds, and slip belts in the accumulation bodies of the landslides. We have delineated the potential landslide area, and determined the sliding depth range at 4 to 8 m. We analyzed the stability of the landslide based on the comparison of water content distribution and the relevant geological information in the sliding body to reveal the possibility of future destruction. The results of this study demonstrated that the combined techniques of MRS and TEM have the capability to effectively monitor potential landslides for key parameters needed for risk assessment.

2.5‐D inversion of frequency‐domain electromagnetic data generated by a grounded‐wire source

Geophysics ◽  
2002 ◽  
Vol 67 (6) ◽  
pp. 1753-1768 ◽  
Author(s):  
Yuji Mitsuhata ◽  
Toshihiro Uchida ◽  
Hiroshi Amano
Keyword(s):  
Frequency Domain ◽  
Regularization Parameter ◽  
Synthetic Data ◽  
Magnetic Data ◽  
Statistical Criterion ◽  
Model Parameters ◽  
Inversion Algorithm ◽  
Gas Field ◽  
Data Set ◽  
Transient Electromagnetic

Interpretation of controlled‐source electromagnetic (CSEM) data is usually based on 1‐D inversions, whereas data of direct current (dc) resistivity and magnetotelluric (MT) measurements are commonly interpreted by 2‐D inversions. We have developed an algorithm to invert frequency‐Domain vertical magnetic data generated by a grounded‐wire source for a 2‐D model of the earth—a so‐called 2.5‐D inversion. To stabilize the inversion, we adopt a smoothness constraint for the model parameters and adjust the regularization parameter objectively using a statistical criterion. A test using synthetic data from a realistic model reveals the insufficiency of only one source to recover an acceptable result. In contrast, the joint use of data generated by a left‐side source and a right‐side source dramatically improves the inversion result. We applied our inversion algorithm to a field data set, which was transformed from long‐offset transient electromagnetic (LOTEM) data acquired in a Japanese oil and gas field. As demonstrated by the synthetic data set, the inversion of the joint data set automatically converged and provided a better resultant model than that of the data generated by each source. In addition, our 2.5‐D inversion accounted for the reversals in the LOTEM measurements, which is impossible using 1‐D inversions. The shallow parts (above about 1 km depth) of the final model obtained by our 2.5‐D inversion agree well with those of a 2‐D inversion of MT data.

Global nonlinear inversion of transient EM data from conducting surroundings using a free‐space plate model

Geophysics ◽  
2000 ◽  
Vol 65 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Shashi P. Sharma ◽  
Pertti Kaikkonen
Keyword(s):  
Free Space ◽  
Synthetic Data ◽  
Electromagnetic Response ◽  
Model Parameters ◽  
Nonlinear Inversion ◽  
Conductive Plate ◽  
Transient Electromagnetic ◽  
Conducting Body ◽  
Geological Conditions ◽  
Very Fast Simulated Annealing

A platelike conducting body in free space is used as a model to invert transient electromagnetic data using the very fast simulated annealing procedure as a global optimization tool. When the host rock conductivity is non‐zero, acceptable fits between the observed and computed responses are difficult to obtain. In general, the conducting body is assigned a lower conductance, larger dimensions (strike length and depth extent) and a smaller depth than the true values. We approximate the response of a conducting host to yield reliable estimates of model parameters as well as a good fit between the observed and computed responses. Our procedure is based on the assumption that the observed electromagnetic response is the sum of the response due to the conductive target and the response due to conducting surroundings (host and overburden). It is also assumed that the host response is laterally invariant, implying a layered earth and fixed source‐receiver geometry. The validity of the superposition assumption is tested against the full solution for a conductive plate in a finite conducting host. The efficacy of our approach is demonstrated using noise‐free and noisy synthetic data and two field examples measured in different geological conditions.

scholarly journals Three-Dimensional Induced Polarization Parallel Inversion Using Nonlinear Conjugate Gradients Method

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Huan Ma ◽  
Handong Tan ◽  
Yue Guo
Keyword(s):  
Message Passing ◽  
Message Passing Interface ◽  
Joint Inversion ◽  
Synthetic Data ◽  
Induced Polarization ◽  
Conjugate Gradients ◽  
Processing Unit ◽  
Inversion Algorithm ◽  
Borehole Data ◽  
Surface Borehole

Four kinds of array of induced polarization (IP) methods (surface, borehole-surface, surface-borehole, and borehole-borehole) are widely used in resource exploration. However, due to the presence of large amounts of the sources, it will take much time to complete the inversion. In the paper, a new parallel algorithm is described which uses message passing interface (MPI) and graphics processing unit (GPU) to accelerate 3D inversion of these four methods. The forward finite differential equation is solved by ILU0 preconditioner and the conjugate gradient (CG) solver. The inverse problem is solved by nonlinear conjugate gradients (NLCG) iteration which is used to calculate one forward and two “pseudo-forward” modelings and update the direction, space, and model in turn. Because each source is independent in forward and “pseudo-forward” modelings, multiprocess modes are opened by calling MPI library. The iterative matrix solver within CULA is called in each process. Some tables and synthetic data examples illustrate that this parallel inversion algorithm is effective. Furthermore, we demonstrate that the joint inversion of surface and borehole data produces resistivity and chargeability results are superior to those obtained from inversions of individual surface data.

scholarly journals 3-D inversion of induced polarization data

Geophysics ◽  
2000 ◽  
Vol 65 (6) ◽  
pp. 1931-1945 ◽  
Author(s):  
Yaoguo Li ◽  
Douglas W. Oldenburg
Keyword(s):  
Wavelet Transforms ◽  
Joint Inversion ◽  
Linear Equations ◽  
Induced Polarization ◽  
Dc Resistivity ◽  
Data Sets ◽  
Bound Constraints ◽  
Borehole Data ◽  
Resistivity Data ◽  
Logarithmic Barrier

We present an algorithm for inverting induced polarization (IP) data acquired in a 3-D environment. The algorithm is based upon the linearized equation for the IP response, and the inverse problem is solved by minimizing an objective function of the chargeability model subject to data and bound constraints. The minimization is carried out using an interior‐point method in which the bounds are incorporated by using a logarithmic barrier and the solution of the linear equations is accelerated using wavelet transforms. Inversion of IP data requires knowledge of the background conductivity. We study the effect of different approximations to the background conductivity by comparing IP inversions performed using different conductivity models, including a uniform half‐space and conductivities recovered from one‐pass 3-D inversions, composite 2-D inversions, limited AIM updates, and full 3-D nonlinear inversions of the dc resistivity data. We demonstrate that, when the background conductivity is simple, reasonable IP results are obtainable without using the best conductivity estimate derived from full 3-D inversion of the dc resistivity data. As a final area of investigation, we study the joint use of surface and borehole data to improve the resolution of the recovered chargeability models. We demonstrate that the joint inversion of surface and crosshole data produces chargeability models superior to those obtained from inversions of individual data sets.

scholarly journals Joint inversion of crosshole radar and seismic traveltimes acquired at the South Oyster Bacterial Transport Site

Geophysics ◽  
2008 ◽  
Vol 73 (4) ◽  
pp. G29-G37 ◽  
Author(s):  
Niklas Linde ◽  
Ari Tryggvason ◽  
John E. Peterson ◽  
Susan S. Hubbard
Keyword(s):  
Joint Inversion ◽  
Synthetic Data ◽  
Physical Property ◽  
Shallow Aquifer ◽  
Model Parameters ◽  
Structural Constraints ◽  
Integral Scale ◽  
Point Spread Functions ◽  
Traveltime Tomography ◽  
The Individual

The structural approach to joint inversion, entailing common boundaries or gradients, offers a flexible and effective way to invert diverse types of surface-based and/or crosshole geophysical data. The cross-gradients function has been introduced as a means to construct models in which spatial changes in two distinct physical-property models are parallel or antiparallel. Inversion methods that use such structural constraints also provide estimates of nonlinear and nonunique field-scale relationships between model parameters. Here, we jointly invert crosshole radar and seismic traveltimes for structurally similar models using an iterative nonlinear traveltime tomography algorithm. Application of the inversion scheme to synthetic data demonstrates that it better resolves lithologic boundaries than the individual inversions alone. Tests of the scheme on GPR and seismic data acquired within a shallow aquifer illustrate that the resultant models have improved correlations with flowmeter data in comparison with models based on individual inversions. The highest correlation with the flowmeter data is obtained when the joint inversion is combined with a stochastic regularization operator and the vertical integral scale is estimated from the flowmeter data. Point-spread functions show that the most significant resolution improvements offered by the joint inversion are in the horizontal direction.

Transdimensional Markov Chain Monte Carlo joint inversion of direct current resistivity and transient electromagnetic data

2020 ◽  
Vol 224 (2) ◽  
pp. 1429-1442
Author(s):  
Ronghua Peng ◽  
Pritam Yogeshwar ◽  
Yajun Liu ◽  
Xiangyun Hu
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Parameter Uncertainty ◽  
Joint Inversion ◽  
Model Parameters ◽  
Mcmc Method ◽  
Complementary Information ◽  
Data Set ◽  
Electromagnetic Data ◽  
Transient Electromagnetic

SUMMARY Joint inversion of multiple geophysical data sets with complementary information content can significantly reduce the non-uniqueness inherent to each individual data set and, therefore, can improve subsurface characterization. Gradient-based joint inversion methods depend on the choice of model regularization and usually produce one single optimal model, and rely on linearization to estimate model parameter uncertainty. However, a quantitative evaluation of the parameter uncertainty of the derived model parameters is crucial for reliable data interpretation. In this study, we present a transdimensional Markov Chain Monte Carlo (MCMC) method for the joint inversion of direct current resistivity and transient electromagnetic data, which provides a rigorous assessment of the uncertainty associated with the derived model. The transdimensional property of the algorithm allows the number of unknown model parameters to be determined adaptively by the data. This usually favours models with fewer parameters through the parsimony criterion of the Bayesian method by choosing suitable prior distributions. In this paper, we demonstrate that the transdimensional MCMC method combines complementary information contained in each data set and reduces the overall uncertainty using synthetic examples. Furthermore, we successfully applied the new joint inversion scheme to field data from Azraq, Jordan. The transdimensional MCMC inversion results are in good agreement with the results obtained by deterministic inversion techniques. From the MCMC inversion results we identified the thickness of a basalt formation and a conductive zone, which were uncertain and not interpreted in prior studies, adding to the geological interpretation.

Combined application of dc and TEM to sea‐water intrusion mapping

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 417-425 ◽  
Author(s):  
Chieh-Hou Yang ◽  
Lun-Tao Tong ◽  
Ching-Feng Huang
Keyword(s):  
Pore Water ◽  
Sea Water ◽  
Salt Water ◽  
Joint Inversion ◽  
Empirical Relation ◽  
Dc Resistivity ◽  
Water Conductivity ◽  
Archie’S Law ◽  
Resistivity Method ◽  
Transient Electromagnetic

A geoelectric survey using a dc resistivity method and a transient electromagnetic induction (TEM) method was carried out from 1986 to 1988. It was used to help map the lateral and vertical distributions of the freshwater/salt‐water interface in the Pei‐kang area on the west coast of Taiwan. The dc and TEM soundings were performed at 79 localities over an area of 240 km2 of Quaternary alluvium. Significant changes in pore‐water conductivity at some places were detected by these two methods. A low resistivity value (<1.5 ohm-m) implies salt‐water contamination of groundwater. The results of spatial distribution of apparent resistivity indicate the salt‐water‐affected aquifers are confined to the southwest part of the study area, and the affected aquifers are confined to the top of two aquifers. A geoelectric model with three to four layers is inferred from the joint inversion of dc and TEM data. Based on a modified Archie’s law suggested by the authors, an empirical relation between pore‐water resistivity of the stratum and formation resistivity can be obtained. It can be used to convert the computed resistivity of each geoelectric layer (aquifer) to the resistivity of the water contained in these layer, thus leading to the assessment of groundwater contamination. Repeated dc resistivity measurements have been carried out at selected locations once every year from 1986 to 1988. These data were used to monitor the temporal variation and a possible spreading of the salt‐water invasion. During 1995, a dc survey was conducted in the same area to compare with the dc sounding results obtained in 1988. The final results provide an evaluation of the efficiency of groundwater management in the study area.

Determination of thermal properties and formation temperature from borehole thermal recovery data

Geophysics ◽  
2003 ◽  
Vol 68 (6) ◽  
pp. 1835-1846 ◽  
Author(s):  
Tien‐Chang Lee ◽  
A. D. Duchkov ◽  
S. G. Morozov
Keyword(s):  
Synthetic Data ◽  
Thermal Recovery ◽  
Model Parameters ◽  
Formation Temperature ◽  
Drilling Mud ◽  
Borehole Data ◽  
Linear Inversion ◽  
Element Simulation ◽  
Model Formation ◽  
Parameter Values

Thermal recovery in boreholes cooled by circulation of drilling mud has been modeled for estimating formation temperature and thermal conductivity. Coupled with a finite‐element simulation of heat conduction, inverse modeling for the desired parameters starts with a genetic algorithm that feeds initial estimates of model parameters to an iterative quasi‐linear inversion scheme. In addition to using the rms misfit between the computed and observed borehole temperatures, the results are assessed by comparing or constraining the model formation temperature with a value obtained conventionally from an asymptotic temperature–time relation for a steady line source. The model conductivity is further evaluated for equality with a conductivity value, which is estimated through simulation of heat exchange between the formation and circulating mud. Test results on synthetic data and two sets of highly noisy borehole data from Lake Baikal in Russia indicate that the two equality criteria in temperature and conductivity are achievable. Multiple runs of GA‐IM are used to find mean parameter values and their uncertainties. The resultant model conductivity values are consistent with those measured in cores with a needle‐probe method.

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