Marine magnetotellurics for petroleum exploration, Part II: Numerical analysis of subsalt resolution

Hoversten, G. Michael; Morrison, H. F.; Constable, Steven

doi:10.1190/1.1444394

Cited by 97 publications

(33 citation statements)

References 20 publications

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“…There were several publications presenting the results of marine magnetotelluric (MT) surveys Hoversten et al, 1998Hoversten et al, , 2000Ellingsrud et al, 2002;Key, 2003;Key et al, 2006). In all these publications, however, the interpretation of the sea-bottom MT data was based, as a rule, on 1D or 2D modeling, which limited the practical effectiveness of the MT method.…”

Section: Introductionmentioning

confidence: 99%

Rigorous 3D inversion of marine magnetotelluric data in the area with complex bathymetry

Zhdanov

Wan

Gribenko

et al. 2009

SEG Technical Program Expanded Abstracts 2009

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SummaryThree-dimensional (3D) magnetotelluric (MT) inversion is an emerging technique for offshore hydrocarbon (HC) exploration. In this paper we introduce a new approach to 3D inversion of MT data for offshore HC exploration based on the integral equation method. The method is implemented in a fully parallel computer code. We have applied the developed method and software for the inversion of marine MT data collected by the Scripps Institution of Oceanography (SIO) in the Gemini Prospect, Gulf of Mexico. The inversion domain was discretized into 1.7 M cells. It took 9 hours to complete 51 iterations on the 832 processor cluster with a final misfit between the observed and predicted data of 6.2%. The inversion results reveal a resistive salt structure which is confirmed by a comparison with the seismic data. These inversion results demonstrate that we can map resistive geoelectrical structures like salt domes or HC reservoirs with reasonable accuracy using 3D inversion of marine MT data.

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Section: Introductionmentioning

confidence: 99%

Rigorous 3D inversion of marine magnetotelluric data in the area with complex bathymetry

Zhdanov

Wan

Gribenko

et al. 2009

SEG Technical Program Expanded Abstracts 2009

View full text Add to dashboard Cite

show abstract

“…These techniques encounter different challenges such as limited resolution, not being applicable in certain environments (e.g., close to buildings) (Yukon Corporation Seismic Imaging Report 2006), and facing processing challenges, such as imaging beneath salt layers (Hoversten et al 1998;Leveille et al 2011). To obtain a better understanding of subsurface reservoirs and to overcome some of the surface seismic challenges, crosswell seismic-imaging techniques attracted considerable attention recently (Schlumberger Imaging Services Report 2009Daley et al 2010;Marion et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Synergizing Crosswell Seismic and Electromagnetic Techniques for Enhancing Reservoir Characterization

2016

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SummaryIncreasing complexity of hydrocarbon projects and the request for higher recovery rates have driven the oil-and-gas industry to look for a more-detailed understanding of the subsurface formation to optimize recovery of oil and profitability. Despite the significant successes of geophysical techniques in determining changes within the reservoir, the benefits from individually mapping the information are limited. Although seismic techniques have been the main approach for imaging the subsurface, the weak density contrast between water and oil has made electromagnetic (EM) technology an attractive complement to improve fluid distinction, especially for high-saline water. This crosswell technology assumes greater importance for obtaining higher-resolution images of the interwell regions to more accurately characterize the reservoir and track fluid-front developments. In this study, an ensemble-Kalman-based history-matching framework is proposed for directly incorporating crosswell time-lapse seismic and EM data into the history-matching process. The direct incorporation of the time-lapse seismic and EM data into the history-matching process exploits the complementarity of these data to enhance subsurface characterization, to incorporate interwell information, and to avoid biases that may be incurred from separate inversions of the geophysical data for attributes. An extensive analysis with 2D and realistic 3D reservoirs illustrates the robustness and enhanced forecastability of critical reservoir variables. The 2D reservoir provides a better understanding of the connection between fluid discrimination and enhanced history matches, and the 3D reservoir demonstrates its applicability to a realistic reservoir. Historymatching enhancements (in terms of reduction in the historymatching error) when incorporating both seismic and EM data averaged approximately 50% for the 2D case, and approximately 30% for the 3D case, and permeability estimates were approximately 25% better compared with a standard history matching with only production data.

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“…A number of recent studies have investigated some aspects of imaging salt structures with MT (Constable et al, 1998;Hoversten et al, 1998Hoversten et al, , 2000Zhdanov et al, 2009, among others). Most of these use 1D or 2D MT modeling or inversion for imaging salt structures.…”

Section: Introductionmentioning

confidence: 99%

Detecting a salt dome overhang with magnetotellurics: 3D inversion methodology and synthetic model studies

2012

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Detecting a salt dome overhang is known to be problematic by seismic methods alone. We used magnetotellurics (MT) as a complementary method to seismics to investigate the detectability of a salt dome overhang. A comparison of MT responses for 3D synthetic salt models with and without overhang shows that MT is very sensitive to shallow salt structures and suggests that it should be possible to detect an overhang. To further investigate the resolution capability of MT for a salt dome overhang, we performed a 3D MT inversion study and investigated the impact of model parametrization and regularization. We showed that using the logarithms of the conductivities as model parameters is crucial for inverting data from resistive salt structures because, in this case, commonly used Tikhonov-type stabilizers work more equally for smoothing the resistive and conductive structures. The use of a logarithmic parametrization also accelerated the convergence and produced better inversion results. When the Laplace operator was used as a regularization functional, we still observed that the inversion algorithm allows spatial resistivity gradients. These spatial gradients are reduced if a regularization based on first derivatives in contrast to the Laplace operator is introduced. To demonstrate the favorable performance when logarithmic parametrization and gradient-based regularization are employed, we first inverted a data set simulated for a simple model of two adjacent blocks. Subsequently, we applied the code to a more realistic salt dome overhang detectability study. The results from the detectability study are encouraging and suggest that 3D MT inversion can be applied to decide whether the overhang is present in the shallow salt structure even in the case when only profile data are available. However, to resolve the overhang, a dense MT site coverage above the flanks of the salt dome is required.

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Marine magnetotellurics for petroleum exploration, Part II: Numerical analysis of subsalt resolution

Cited by 97 publications

References 20 publications

Rigorous 3D inversion of marine magnetotelluric data in the area with complex bathymetry

Rigorous 3D inversion of marine magnetotelluric data in the area with complex bathymetry

Synergizing Crosswell Seismic and Electromagnetic Techniques for Enhancing Reservoir Characterization

Detecting a salt dome overhang with magnetotellurics: 3D inversion methodology and synthetic model studies

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