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.

The lithology and rock-physical properties of tight sandstone reservoirs become increasingly complex, resulting in a more challenging reservoir evaluation process. Conventional rock-physics experiments are too restrictive to adequately investigate formation properties. Recently, the emerging digital rock-physics (DRP) technology effectively overcomes these constraints. Nevertheless, the current DRP technology faces two major challenges: the integration of multiple-resolution images and the upscaling of rock-physics properties (electricity). We develop an innovative method for assigning electrical characteristics to voxel units, enabling the integration of multiresolution images, as well as a novel approach for establishing a new saturation model to achieve electrical property upscaling. Initially, core samples are selected and drilled based on logging data and lithology analysis, followed by multiresolution scanning experiments, such as X-ray computed tomography, quantitative evaluation of materials by scanning electron microscopy, and modular automated processing system (MAPS). After that, mineral components are segmented, and multicomponent digital rocks are constructed. Considering mineral voxel as the analytical units, pore characteristics within each mineral, which are extracted from MAPS, are used to generate 3D pores by the quartet structure generation set method. These generated 3D pores are then merged with their respective mineral voxels. Subsequently, the electrical properties of the merged models are simulated and assigned to multicomponent digital rock. This process enables the integration of multiresolution images, leading to the construction of high-precision digital rocks. In addition, high-precision digital rock-based electrical modeling is conducted, and a new saturation model is then established by combining DRP, experiment rock physics, and theoretical rock physics. Finally, the new saturation model is applied to calculate saturation, accomplishing electrical property upscaling. Application results show the new saturation model improves the accuracy of saturation evaluation, demonstrating the feasibility of the upscaling method for electrical properties.

The rotary valve speed control, seriously affected by the nonlinear characteristic of rotary valve load torque, affects the generation of drilling fluid pressure phase shift keying (PSK) signal and its quality. The calculation model feedforward of the load torque acts on the speed control system and enables the motor voltage to change according to the law of calculation model, and the linearization correction of the speed system is performed. Additionally, the flow measurement is introduced into the calculation model of the load torque to track the load torque change with the flow, suppressing the influence of large changes in flow rate on open-loop control of rotary valve speed. The closed-loop proportional-integral-derivative (PID) control is formed by negative feedback of speed, and the PID parameter value rule is established based on the rapid decay control of transient component in the rotary valve speed step response, which speeds up the tracking of the rotary valve speed following the control voltage pulse and reduces the distortion of the drilling fluid pressure PSK signal, increasing the frequency of the drilling fluid pressure carrier and improving the transmission rate of downhole information. Simulink simulation indicates that the closed-loop PID control of rotary valve speed can track the change of control voltage pulse quickly and strongly suppress the interference influences from flow measurement error and load torque calculation model deviation.