Multiscale Digital Core Technology for Analyzing the Genesis of Low‐Resistivity Oil Reservoirs in the Guantao Formation of Bohai Sea: Clay Mineral‐Induced Additional Conductivity Effect, Pore Structure Regulation Mechanism, and Quantitative Characterization

The genetic mechanism of low‐resistivity oil reservoirs in the Guantao Formation of the Bohai Sea is complex, and understanding the role of clay minerals and pore structures in forming low resistivity remains unclear. This study employed multiscale digital core technology to integrate multisource digital core data. Combined with flow characteristic‐based upscaling technology, microscale and nanoscale digital cores were reconstructed to calculate parameters such as porosity, permeability, and formation factor. At the same time, mercury intrusion and seepage experiments were simulated. The research reveals two key mechanisms underlying the influence of clay minerals and pore structures on low‐resistivity oil reservoirs: first, the additional conductive effect of clay. Among clay minerals, illite–smectite mixed‐layer minerals exhibit the strongest conductivity, which is the key factor contributing to reduced resistivity, followed by illite, kaolinite, and chlorite in decreasing order of additional conductive capacity. The second is the regulatory role of pore structures. Kaolinite fills intergranular pores to form a complex micropore system, resulting in high irreducible water saturation in the reservoir, which is the primary cause of low‐resistivity oil reservoirs. This study clarifies the influence mechanisms of clay minerals and pore structures on resistivity, provides key technical support for fine geological modeling and optimization of oil and gas reservoir development schemes, and holds significant practical value for reducing exploration risks and improving oil recovery efficiency.