Clay pores are important storage spaces in shale oil reservoirs. Studying the adsorption behavior of shale oil in clay nanopores is of great significance for reserve assessment and exploitation. In this work, illite clay pore models and multi-component shale oil adsorption models considering light hydrocarbon correction are constructed for carrying out molecular dynamics simulation. We studied the adsorption behavior and characteristics of shale oil in illite pores, and analyzed the effects of reservoir environmental factors such as temperature, pressure and pore size on the adsorption behavior. The results show that in illite nanopores, shale oil can form multiple adsorption layers. The heavier the component, the stronger the interaction with the wall. The adsorption ratio of the component is closely related to the solid–liquid interaction and the molar fraction, which preliminarily reveals the reason why the heavy component content in the produced oil is considerable. The increase in temperature promotes the desorption of light and medium components, while the heavy components and dissolved gas are less affected; although the increase in pressure inhibits diffusion, the adsorption amount changes little, and only the light component increases slightly. This study deeply reveals the adsorption mechanism of shale oil in illite pores, providing a theoretical basis for the optimization and development of shale reservoirs.

Complete and thorough core cleaning is a critical prerequisite for the precise measurements of most rock's petrophysical parameters. In shale, the oil cleaning process, aimed to remove the volatile hydrocarbons, is often complicated by the requirement for intact solid organic. Evaluation of shale's cleaning methods needs to take structural integrity of organic matrix into account but neglected in the existing researches. Here, we develop a novel evaluation method using a modified ESH (extended slow heating) pyrolysis cycle, which starts at a lower initial temperature of 150°C for 10 minutes and then slowly increases to 650°C by 10°C/min. Hydrocarbons on the ESH pyrogram were divided into light free hydrocarbon (S_A), FHR (fluid‐like hydrocarbon, S_B), and solid organic matter (S_C). We propose a set of quantitative evaluation criterions comparing the results of pyrograms, for different types of the hydrocarbons, at different cleaning conditions. We showed that a modified pyrogram achieves complete cleaning with S_A and S_B removed while S_C remains almost intact. The modified pyrogram achieves complete removal of FHR in the second stage of pyrogram, while earlier researches often report residual FHR. The introduced method improves the accuracy in the identification of production potential in kerogen‐rich shale reservoirs up to about 3% of the total pore volume. Further, the new approach allows a quantitative assessment for the cleaning quality without altering the sample's organic matrix. Future studies on the petrophysical properties of the hydrocarbon‐bearing reservoir rocks may benefit from the thorough hydrocarbon removal achieved through the modified pyrogram methods proposed in this study.

Unconventional reservoirs typically exhibit strong heterogeneity leading to a significant scale effect in digital rock physics simulations. To ensure the reliability of the simulation results, improving computational efficiency and increasing sample sizes are crucial. In this study, we present a numerical finite element simulation method for the acoustic and electrical properties of digital rock cores based on tetrahedral unstructured meshes. We calculated the elastic moduli and electrical resistivity of the Fontainebleau sandstone digital rock samples. A comparison was made between the tetrahedral mesh and the traditional voxel-based hexahedral mesh in terms of the accuracy and efficiency of finite element numerical simulations. The results indicate that this numerical simulation method based on the tetrahedral mesh exhibits high accuracy comparable to experimental results, and its computational efficiency is significantly improved compared to the traditional hexahedral mesh method. These findings highlight the advantages of this finite element simulation method in improving the computational scale and efficiency of digital rock simulations. It effectively addresses common computational resource constraints in dealing with large-scale core systems and facilitates better integration with engineering construction, well-logging instrument simulations, and production applications.

Natural gas hydrates, solid crystalline structures formed by the combination of natural gas and water molecules under high-pressure and low-temperature conditions, are regarded as a promising clean energy source. Electrical resistivity serves as a fundamental petrophysical parameter for quantifying natural gas hydrate saturation in sand-dominated sediments, with its sensitivity to pore-filling hydrate morphology and distribution patterns. An integrated experimental system combining in-situ CT scanning and resistivity measurement was developed to investigate tetrahydrofuran (THF) hydrate formation dynamics in quartz sand sediments. We prepared four distinct THF solutions to represent different hydrate formation regimes, lowered the temperature within a reactor containing quartz grains, and continuously monitored the electrical resistivity of the sediments during the hydrate formation. Additionally, CT scanning was used to acquire three-dimensional grayscale images at varying hydrate saturation. The experimental resistivity data revealed pronounced deviations from classical Archie’s equation, demonstrating complex behavior between the resistivity index and water saturation. The CT scan images demonstrate a pronounced salting-out effect during the hydrate formation process. The precipitation of dissolved salts significantly increased the salinity of formation water, resulting in a corresponding decrease in resistivity due to enhanced ionic conductivity. The phenomenon significantly impedes hydrate formation kinetics, causing a substantial divergence between the measured hydrate saturation and the thermodynamic equilibrium prediction. When temperature effects and salt precipitation phenomena are properly accounted for, the resistivity index-water saturation relationship exhibits excellent agreement with Archie’s law, enabling reliable estimation of hydrate saturation in quartz-dominated sediments.