Two-dimensional Modeling of Magnetotelluric Data for Detection of Hydrocarbon Sources by Lanczos Bidiagonalization Method (Case Study: Kashan Region)

Document Type : Research Paper

Authors

1 Department of Earth Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Faculty of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran

3 Department of Physics, Faculty of Science, Arak University, Arak, Iran

Abstract

The magnetotelluric method uses natural and time-varying electric and magnetic fields on the earth’s surface to detect the earth’s electrical structures, such as hydrocarbons exploration. In the inversion process, the matrix inverse calculation method has a considerable effect on the inversion speed as well as the quality of obtained models. Lanczos Bidiagonalization (LB) method has been reported to be a fast and efficient approach for solving the inversion problems. In LB algorithm, the full set of equations is replaced by a dimensionally reduced system of equations. In addition, we employed Active Constraint Balancing (ACB) approach for determining the optimum regularization parameter. The results of the synthetic data inversion show that both methods require equal computer memory, but LB method is faster and more reliable than Conjugate Gradient (CG) method. The proposed approach was also applied to inverse real MT data collected from the Kashan area, which is the most interesting area for oil and gas exploration in the Central Iran Basin. The obtained model shows the Qom Formation, which is the most important reservoir rock and hydrocarbon source rock in central Iran, and other geological structures of the region, such as the Navab anticline and faults.

Keywords

References

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Journal of Petroleum Research
Volume 31, 1400-3 - Serial Number 118
September and October 2021
Pages 121-133

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