Conductivity Laws of High-Clay Shale Oil Using Artificial Cores and Digital Cores

Understanding the conductivity of shale oil reservoirs is crucial for accurate fluid saturation assessment, yet it remains challenging due to complex mineralogy and pore structures. To address this issue, this study integrates experimental measurements on artificial cores, digital core simulations, and well-log data to unravel the conductive mechanisms of high-clay shale. Conductive adhesive was used to fabricate two suites of artificial cores with controlled Illite and pyrite contents. Comprehensive petrophysical measurements and resistivity experiments under varying water saturations were conducted. Concurrently, digital cores were constructed to simulate four distinct pore fluid types classified by occurrence state (inorganic pore water, organic pore adsorbed oil, inorganic pore free oil, and inorganic pore bound oil), and their influence on rock conductivity was analyzed via finite-element numerical simulation. Building on the effective medium theory (EMT), component-specific resistivity models were developed for clay, pyrite, and pore fluids. The critical percolation rate and percolation exponent for these components were rigorously optimized against the resistivity data obtained from the artificial core experiments and digital core simulations. These optimized parameters were subsequently integrated into a unified seven-component EMT model. This model was applied to log data from the Qingshankou Formation in the Songliao Basin, where component volumes were derived from elemental and 2D NMR logging. Forward-calculated resistivity showed excellent agreement with field measurements, achieving an average relative error of 9.8% and 5.2% for two wells. This work provides a robust theoretical framework and a practical model for understanding shale conductivity and improving saturation interpretation in complex mineral compositions and clay-rich shale oil reservoirs.