Electromagnetic and Seismic Joint Structural Modeling Technology and Its Application in Chaiwopu Area of Junggar Basin

[objective] The Chaiwoubu area of the Qaidam Basin is situated in a complex piedmont structural belt affected by multistage tectonic activities. Extensively developed fault systems and highly fragmented subsurface structures, coupled with low-quality seismic data, have long restricted hydrocarbon exploration breakthroughs in this region.[methods]To tackle these problems, this study proposes an electrical-seismic joint inversion method incorporating prior information and dual structural constraints. First, taking full advantage of seismic profiles with high lateral resolution and clear mid-shallow stratigraphic architectures, structural prior information is extracted to build an initial resistivity model, which effectively reduces the multiplicity of inversion solutions. Second, a Gram matrix-based regularization function is adopted to establish structural constraint terms. The gradient field characteristics derived from the velocity model are mapped to the resistivity inversion objective function, ensuring structural consistency between resistivity and velocity models.[results]Theoretical model tests demonstrate that the proposed method effectively strengthens structural coupling and constrained correlations among different geophysical parameters and improves the spatial resolution of inversion results. [conclusion]In applications to field electromagnetic data from the Chaiwoubu area, the inverted resistivity profiles exhibit good agreement with available drilling and seismic interpretations. Two dominant thrust structural units are identified: the northern unit comprises a basin-directed overthrust nappe with upward thrusting motion, whereas the central unit develops a large-scale basement-cutting reverse fault with a vertical throw exceeding 1 km. These two structural systems dip oppositely and squeeze each other, forming a typical contractional structural assemblage that controls the development of secondary fault blocks and local folds in the study area.The proposed electrical-seismic joint inversion technique provides a feasible technical scheme for fine structural analysis and favorable hydrocarbon zone optimization in complex basin-slope transition zones. The results are of great practical significance for delineating favorable hydrocarbon accumulation belts and guiding future exploration deployment in the Chaiwoubu area.