Pore Structure Characteristics and Affecting Factors of Shale in the First Member of the Qingshankou Formation in the Gulong Sag, Songliao Basin

[Image: see text] A major historical breakthrough has been made in the exploration of the GK (the first member of the Qingshankou Formation (K2qn(1)), Gulong Sag) shale oil of the Songliao Basin. However, few reports have been reported on the pore structure characteristics of this large-scale lacustrine medium–high maturity shale. In addition, the difference between the pore structure characteristics of the GK shale and medium–low maturity marine/continental shale is unknown, and the affecting factors of pore development are still unclear. Therefore, in order to clarify the pore structure characteristics of the GK shale and its affecting factors, this study characterized them experimentally and revealed the law of pore evolution using the mineral composition and geochemical analysis, microscopic observations, and pore quantification techniques. Results indicate that (1) the pore system of GK shale reservoirs is divided into micropores (pore diameter < 10 nm), mesopores (10 nm < pore diameter < 50 nm), and macropores (pore diameter > 50 nm); (2) the pore structure of the GK shale is mainly affected by the clay content, siliceous mineral content, and thermal maturity; and (3) when the content of clay minerals and siliceous minerals in the GK shale reservoir is high, and ∼0.8% < R(o) < ∼1.4%, the storage capacity and oil content of the GK shale show high values, and it can be considered as a strong candidate for further exploration and development. This research can push the shale oil revolution to a new height and is significant to promote the development of the petroleum industry.