Preface: New advances in unconventional petroleum sedimentology in China

Significant progress has been gradually made on the exploration and development of unconventional petroleum on land in China over the past 20 years. In 2019， unconventional petroleum production in China accounted for about 23% of the total oil and gas production that year and reached 70 million tons of oil equivalent in 2020, indicating China’s petroleum industry has entered a new stage of unconventional petroleum development. Unconventional petroleum sedimentology as an important part of unconventional petroleum geology， and the theoretical system has been gained more and more attention over recent years， leading to important studies， such as “Depositional model of gravity flows， sandy debris in a deep lacustrine basin”， “Depositional model of marine and/or lacustrine organic-rich shale”， “Abundant micro- and nano- pore throat systems developed in fine-grained sedimentary rocks”， and “Sweet-spot areas （intervals） of unconventional petroleum resulted from coupling the sedimentology of several geological events”. This special issue systematically assembles new advances made in the unconventional petroleum sedimentology of China by Chinese unconventional petroleum sedimentologists in recent years. These studies refer to about 30 sets of unconventional petroleum strata （intervals） from the Proterozoic to Cenozoic in more than 50 basins， providing an important theoretical basis and technical support for unconventional petroleum exploration and development. Unconventional petroleum sedimentology would focus on deposition and formation of“sweet⁃spot box” and “sweet⁃spot group ”developed in unconventional petroleum industry in future, and further enhance efficiency of unconventional petroleum exploration and development.