Abstract
The Horgos area of the thrust belt on the southern margin of the Junggar Basin has a good prospect for oil and gas exploration. However, because of the complex surface conditions and the coverage of the gravel layer, the seismic data on the southern margin thrust belt have some poor imaging, which makes the three-row structural pattern unclear. It is urgent to use 3D magnetotelluric (MT) exploration to investigate the distribution of gravel layer for seismic processing to build shallow model. In this paper, a 3D geoelectric model is established using MT data and logging data collected in the study area. Through the forward modeling and inversion calculation, the feasibility of using 3D MT data to explore the high resistivity gravel layer of various thickness is verified. Phase tensor analyses indicate the shallow (> 0.1 Hz) electrical structure is mainly 1D or 2D, while the deep structure is affected by 3D structure. The 3D conjugate gradients inversion method is used to process the MT data of the study area, the forward responses of the inversion result fit the observed data well and the electrical layers of the 3D inversion is consistent with the electrical characteristic revealed by the electric logging data. All these indicate the reliability of the 3D inversion results. The 3D MT results are first used to interpret the distribution and thickness of two sets of gravel layers in the study area. It is mainly used to assist the seismic exploration to solve problems involving exploration of complex surface carbonate rocks, exploration of deep complex structures and identification of shallow lithology. It proves that 3D MT is an effective technique for the gravel and shallow lithology exploration in similar regions.
Published Version
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