The Taiyuan Formation, located on the northern margin of the Ordos Basin, has an important role in reconstructing tectonic paleogeography and evolutionary process due to its preservation of information about the tectonic evolution of the basin throughout the Late Paleozoic. The provenance, paleogeography, and tectonic activity traits of the Taiyuan Formation were examined using the sedimentary petrology and zircon chronology methods. The Alxa block is consistent with the dating results of the Taiyuan Formation in Shabatai, and the Daqing Shan is consistent with the results of the Taiyuan Formation in Xiachengwan and Adaohai. It is inferred that the provenance of the Taiyuan Formation in the western part of the northern margin of the basin is from the Alxa block, and the provenance in the eastern part is from the Daqing Shan when combined with the study of sandstone detrital components, and paleocurrent. In the late Paleozoic, the Siberian plate collided with the North China Craton, and the Taiyuan Formation was deposited in the northern margin of the Ordos Basin. However, on account of the different ages and types of basement rocks and the central paleo-uplift which has not completely disappeared, the Taiyuan Formation has obvious east-west zonation.

Kerogen micropores in shale are crucial for gas sorption; nevertheless, their formation and evolution have been insufficiently studied. To qualitatively and quantitatively analyze changes in the molecular structure and associated micropores of kerogen throughout natural maturation, a series of experiments were performed on collected kerogen samples with varying maturity levels. The results demonstrated that the evolution of the chemical structure and associated micropores of kerogen can be divided into three stages during thermal evolution. When Ro < 1.43%, micropores are primarily controlled by the aliphatic composition of kerogen, resulting in a reduction in the micropore volume with decreasing numbers of aliphatic functional groups. When 1.43% < Ro < 1.93%, the micropore structure is primarily governed by the aromatic composition of kerogen and the micropore volume exhibits a gradual increment with increasing aromatic ring size. When Ro > 1.93%, the micropore volume rapidly increases with increasing aromatic composition of kerogen, and the aromatic rings become more orderly. Moreover, molecular simulations also show that the adsorption curves of CO₂ and CH₄ are type I isotherms, and that the adsorption capacity of CO₂ is greater than that of CH₄ under the same conditions, which indicates that the microscopic adsorption mechanism of CH₄ and CO₂ is gas competitive adsorption. This research offers new perspectives on the formation and evolution of kerogen micropores, and the carbon sequestration process.

Accurately determining the pore structure and heterogeneity characteristics of marine-continental transitional shale in the Taiyuan Formation is crucial for evaluating the shale gas resources in the northern Ordos Basin. However, the studies on pore characteristics and heterogeneity of marine-continental transitional shales and isolated kerogen are limited. This study collected Taiyuan Formation shale in the northern Ordos Basin, and corresponding kerogen isolated from shale and used N₂ and CO₂ adsorption experiment and Frenkel–Halsey–Hill and Volume-Specific Surface Area model to investigate the pore structure and heterogeneity of both. The results show that the isolated kerogen is dominated by micropores, and the micropore’s specific surface area and volume are 4.7 and 3.5 times the corresponding shale, respectively. In addition, the microporous heterogeneity of the isolated kerogen is stronger than that of shale, while the mesoporous heterogeneity is exactly the opposite. Meanwhile, the micropores fractal dimension D_m is positively correlated with organic matter (OM) content, while mesopores fractal dimension D₁ and D₂ are negatively linearly correlated with TOC content and have no significant relationship with clay mineral and quartz content (but show a significant positive correlation with illite and illite/smectite mixed layer). Isolated kerogen plays an important role in the pore (especially micropores) heterogeneity of shale, while other minerals (such as clay minerals) have a controlling effect on the mesopores heterogeneity of shale. Compared with marine shale, the marine-continental transitional shale of the Taiyuan Formation has a lower fractal dimension and better connectivity, which is conducive to shale gas seepage and migration. The final result can provide a significant basis for the reserve evaluation and the optimization of desert areas in the marine-continental transitional shale gas in the northern Ordos Basin.