Modeling the overpressure of organic shales caused by thermal maturation and its elastic responses is crucial for geophysical characterization of source rocks and unconventional shale reservoirs. Thermal maturation involves the generation of excess fluid contents (oil and gas) and can cause the overpressure if an organic shale preserves the produced fluids partly or wholly. The solid organic matter (e.g., kerogen or solid bitumen) with the potential of generating hydrocarbon presents two types of morphology in organic shales: scattered patches as pore-fillings and continuous network as load-bearings. According to the kerogen morphology, two bulk volume models are devised to simulate the elasticity of organic shales using respective rock-physics modeling schemes. The rock physics modeling combined with the density and compressibility of pore-fillings are demonstrated to effectively capture the excess pore pressure characteristics due to thermal maturation in organic shales. The basic principle of solving the overpressure is that the pore space volume equals the total volume of all components within the pores before and after the maturation. According to the modeling results, the elastic characteristics of overpressure due to thermal maturation reveal a decrease in velocity and a slight decrease in density. Besides, for an organic shale with a relatively rigid framework, it tends to yield higher overpressure than a shale with a relatively compliant framework. With proper calibration, the modeling strategy shows its potential in quantitatively interpreting the well-log data of organic shale formation within the thermal maturation window.

The multiscale rock physics of unconventional reservoirs have drawn increasing attention in recent years, which involves several essential issues, including measuring method, transport property, physics model, characteristic scale, and their application. These issues vastly affect science and engineering regarding the exploration and development of unconventional reservoirs. To encourage communication on the advances of research on the rock physics of unconventional reservoirs, a conference on Multiscale Rock Physics for Unconventional Reservoirs was jointly organized by the journals Energies and Advances in Geo-Energy Research. Due to the limitations of movement caused by COVID-19, 21 experts introduced their work online, and the conference featured the latest multiscale theories, experimental methods and numerical simulations on unconventional reservoirs.