Seismic image-guided 3D inversion of marine controlled-source electromagnetic and magnetotelluric data

2020 ◽  
Vol 8 (4) ◽  
pp. SS1-SS13 ◽  
Author(s):  
Randall L. Mackie ◽  
Max A. Meju ◽  
Federico Miorelli ◽  
Roger V. Miller ◽  
Carsten Scholl ◽  
...  
Keyword(s):  
Structural Complexity ◽  
Structural Similarity ◽  
Hydrocarbon Exploration ◽  
Magnetotelluric Data ◽  
Controlled Source ◽  
Seismic Image ◽  
New Frontier ◽  
Gradient Fields ◽  
Resistivity Model ◽  
Geologic Interpretation

Geologic interpretation of resistivity models from marine controlled-source electromagnetic (CSEM) and magnetotelluric (MT) data for hydrocarbon exploration and reservoir monitoring can be problematic due to structural complexity and low-resistivity contrasts in sedimentary units typically found in new frontier areas. It is desirable to reconstruct 3D resistivity structures that are consistent with seismic images and geologic expectations of the subsurface to reduce uncertainty in the evaluation of petroleum ventures. Structural similarity is achieved by promoting a cross-gradient constraint between external seismically derived gradient fields and the inversion resistivity model. The gradient fields come from coherency weighted structure tensors computed directly from the seismic volume. Consequently, structural similarity is obtained without the requirement for any horizon interpretation or picking, thus significantly reducing the complexity and effort. We have determined the effectiveness of this approach using CSEM, MT, and seismic data from a structurally complex fold-thrust belt in offshore northwest Borneo.

Resistivity imaging of controlled‐source audiofrequency magnetotelluric data

Geophysics ◽  
1992 ◽  
Vol 57 (7) ◽  
pp. 952-955 ◽  
Author(s):  
Yutaka Sasaki ◽  
Yoshihiro Yoneda ◽  
Koichi Matsuo
Keyword(s):  
Current Loop ◽  
Magnetotelluric Data ◽  
Model Inversion ◽  
Controlled Source ◽  
Smooth Model ◽  
Resistivity Model ◽  
Em Method ◽  
Survey Results ◽  
Plane Wave Approximation ◽  
A Current

The controlled‐source audiofrequency magnetotelluric (CSAMT) method is an electromagnetic (EM) method where a transmitter (a grounded electric bipole or a current loop) is placed far away from the receiver sites. If the transmitter is located at distances greater than 3–5 skin depths, the plane-wave approximation is valid and the techniques used for (natural source) MT interpretation can be applied (Goldstein and Strangway, 1975; Sandberg and Hohmann, 1982). The CSAMT method can be employed in a detailed survey by closely spacing a number of receiver sites along a traverse. The borehole CSAMT technique is proposed in West and Ward (1988) to enhance the ability of the surface CSAMT method to detect subsurface inhomogeneities. In these cases, two‐dimensional (2-D) smooth‐model inversion (Rodi et al., 1984; Sasaki, 1989; deGroot‐Hedlin and Constable, 1990) would be particularly useful for deriving a resistivity model from the far‐field data and for presenting the survey results in the form of an image.

Workflow for improvement of 3D anisotropic CSEM resistivity inversion and integration with seismic using cross-gradient constraint to reduce exploration risk in a complex fold-thrust belt in offshore northwest Borneo

2018 ◽  
Vol 6 (3) ◽  
pp. SG49-SG57 ◽  
Author(s):  
Max A. Meju ◽  
Ahmad Shahir Saleh ◽  
Randall L. Mackie ◽  
Federico Miorelli ◽  
Roger V. Miller ◽  
...  
Keyword(s):  
Reservoir Characterization ◽  
Three Dimensional ◽  
Structural Complexity ◽  
Hydrocarbon Exploration ◽  
Parameter Estimates ◽  
Thrust Belt ◽  
Exploration Risk ◽  
Resistivity Logs ◽  
Geologic Interpretation ◽  
Reservoir Parameter

The focus of hydrocarbon exploration has now moved into frontier regions where structural complexity, heterogeneous overburden, and hydrocarbon system fundamentals are significant challenges requiring an integrated exploration approach. Three-dimensional controlled-source electromagnetic (CSEM) anisotropic resistivity imaging is emerging as a technique to combine with seismic imaging in such regions. However, the typically reconstructed horizontal resistivity [Formula: see text] and vertical resistivity [Formula: see text] models often have conflicting depth structures that are difficult to explain in terms of subsurface geology. It is highly desirable to reduce ambiguity or subjectivity in depth interpretation of [Formula: see text] and [Formula: see text] models and also achieve comparability with other coincidentally located subsurface models. We have developed a workflow for integrating information from seismic well-based inversion, interpreted seismic horizons, and resistivity well logs in a cross-gradient-guided simultaneous 3D CSEM inversion for geologically realistic [Formula: see text] and [Formula: see text] models whose parameter estimates for a selected reservoir interval can then be better optimized to aid reservoir characterization. We developed our workflow using exploration data from a complex fold-thrust belt. We found that the integrated cross-gradient approach led to [Formula: see text] and [Formula: see text] models that have a common depth structure, are consistent with seismic and resistivity logs, and are hence less ambiguous for geologic interpretation and reservoir parameter estimation.

Field test of sub-basalt hydrocarbon exploration with marine controlled source electromagnetic and magnetotelluric data

2015 ◽  
Vol 63 (5) ◽  
pp. 1284-1310 ◽  
Author(s):  
G. Michael Hoversten ◽  
David Myer ◽  
Kerry Key ◽  
David Alumbaugh ◽  
Oliver Hermann ◽  
...  
Keyword(s):  
Field Test ◽  
Hydrocarbon Exploration ◽  
Magnetotelluric Data ◽  
Controlled Source

Three-dimensional inversion of controlled-source audio-frequency magnetotelluric data based on unstructured finite-element method

2020 ◽  
Vol 17 (3) ◽  
pp. 349-360
Author(s):  
Xiang-Zhong Chen ◽  
Yun-He Liu ◽  
Chang-Chun Yin ◽  
Chang-Kai Qiu ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
Audio Frequency ◽  
Magnetotelluric Data ◽  
Controlled Source ◽  
Element Method

Mineral exploration with 3-D controlled-source electromagnetic method: a synthetic study of Sukhoi Log gold deposit

2019 ◽  
Vol 219 (3) ◽  
pp. 1698-1716 ◽  
Author(s):  
M Malovichko ◽  
A V Tarasov ◽  
N Yavich ◽  
M S Zhdanov
Keyword(s):  
Finite Difference ◽  
Gold Deposit ◽  
Large Scale ◽  
Mineral Exploration ◽  
Mineral Deposit ◽  
Hydrocarbon Exploration ◽  
Contraction Operator ◽  
Inversion Algorithm ◽  
Controlled Source ◽  
Regularized Inversion

SUMMARY This paper presents a feasibility study of using the controlled-source frequency-domain electromagnetic (CSEM) method in mineral exploration. The method has been widely applied for offshore hydrocarbon exploration; however, nowadays this method is rarely used on land. In order to conduct this study, we have developed a fully parallelized forward modelling finite-difference (FD) code based on the iterative solver with contraction-operator preconditioner. The regularized inversion algorithm uses the Gauss–Newton method to minimize the Tikhonov parametric functional with the Laplacian-type stabilizer. A 3-D parallel inversion code, based on the iterative finite-difference solver with the contraction-operator preconditioner, has been evaluated for the solution of the large-scale inverse problems. Using the computer simulation for a synthetic model of Sukhoi Log gold deposit, we have compared the CSEM method with the conventional direct current sounding and the CSEM survey with a single remote transmitter. Our results suggest that, a properly designed electromagnetic survey together with modern 3-D inversion could provide detailed information about the geoelectrical structure of the mineral deposit.

Three‐dimensional inversion of magnetotelluric data for a resistivity model with arbitrary anisotropy

2021 ◽  
Author(s):  
Wenxin Kong ◽  
Handong Tan ◽  
Changhong Lin ◽  
Martyn Unsworth ◽  
Benjamin Lee ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Magnetotelluric Data ◽  
Resistivity Model ◽  
Arbitrary Anisotropy

Deep electrical structure of northern Alberta (Canada): implications for diamond exploration

2009 ◽  
Vol 46 (2) ◽  
pp. 139-154 ◽  
Author(s):  
Erşan Türkoğlu ◽  
Martyn Unsworth ◽  
Dinu Pana
Keyword(s):  
Subduction Zone ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Three Dimensional ◽  
Diamond Formation ◽  
Magnetotelluric Data ◽  
Diamond Exploration ◽  
Upper Mantle Structure ◽  
Resistivity Model ◽  
Northern Alberta

Geophysical studies of upper mantle structure can provide constraints on diamond formation. Teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere–asthenosphere boundary. Studies in the central Slave Craton and at Fort-à-la-Corne have detected conductors in the lithospheric mantle close to, or beneath, diamondiferous kimberlites. Graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth. Petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite. Other diamond-bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal. The Buffalo Head Hills in Alberta host diamondiferous kimberlites in a Proterozoic terrane and may have formed in a subduction zone setting. Long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region. Magnetotelluric (MT) data were recorded at 23 locations on a north–south profile extending from Fort Vermilion to Utikuma Lake and an east–west profile at 57.2°N. The data were combined with Lithoprobe MT data and inverted to produce a three-dimensional (3-D) resistivity model with the asthenosphere at 180–220 km depth. This model did not contain an upper mantle conductor beneath the Buffalo Head Hills kimberlites. The 3-D inversion exhibited an eastward dipping conductor in the crust beneath the Kiskatinaw terrane that could represent the fossil subduction zone that supplied the carbon for diamond formation. The low resistivity at crustal depths in this structure is likely due to graphite derived from subducted organic material.

Detecting Skrugard by CSEM — Prewell prediction and postwell evaluation

2014 ◽  
Vol 2 (3) ◽  
pp. SH67-SH77 ◽  
Author(s):  
Lars Ole Løseth ◽  
Torgeir Wiik ◽  
Per Atle Olsen ◽  
Jan Ove Hansen
Keyword(s):  
Data Acquisition ◽  
Barents Sea ◽  
Hydrocarbon Exploration ◽  
Seismic Structure ◽  
Well Location ◽  
Resistivity Logs ◽  
Resistivity Model ◽  
Joint Interpretation ◽  
Hydrocarbon Saturation ◽  
Scenario Testing

The discovery of Skrugard in 2011 was a significant milestone for hydrocarbon exploration in the Barents Sea. The result was a positive confirmation of the play model, prospect evaluation, and the seismic hydrocarbon indicators in the area. In addition, the well result was encouraging for the CSEM interpretation and analysis that had been performed. Prior to drilling the 7220/8-1 well, EM resistivity images of the subsurface across the prospect had been obtained along with estimates of hydrocarbon saturation at the well position. The resistivity distribution was derived from extensive analysis of the multiclient CSEM data from 2008. The analysis was based on joint interpretation of seismic structures and optimal resistivity models from the CSEM data. The seismic structure was furthermore used to constrain the resistivity anomaly to the Skrugard reservoir. Scenario testing was then done to assess potential alternative models that could explain the CSEM data in addition to extract the most likely reservoir resistivity. Estimates of hydrocarbon saturation followed from using petrophysical parameters from nearby wells and knowledge of the area, combined with the most likely resistivity model from CSEM. Our results from the prewell study were compared to the postwell resistivity logs, for horizontal and vertical resistivity. We found a very good match between the estimated CSEM resistivities at the well location and the corresponding well resistivities. Thus, our results confirmed the ability of CSEM to predict hydrocarbon saturation. In addition, the work demonstrated limitations in the CSEM data analysis tools as well as sensitivity to acquisition parameters and measurement accuracy. The work has led to more CSEM data acquisition in the area and continued effort in development of our tools for data acquisition and analysis.

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