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The paleovegetation and paleoclimate characteristics are studied in the Palaeogene strata of Hetao Basin, Subei Basin and Qaidam Basin in China, and the Cretaceous Guyang Formation (K1g) in the Hetao Basin. These three basins receive high attention, different distribution areas, representative. Pollen evidence shows that: (1) The sporopollen assemblage of Palaeogene Linhe Formation (E3l) in Hetao Basin is characterised by Pinaceae-Ephedripites-Ulmipollenites-Chenopodipollis. It reflects that the ancient vegetation types were mainly coniferous and evergreen woody plants, and the climate was cold temperature. The sporopollen assemblage characteristics of the upper member of the Palaeogene Xiaganchaigou Formation (E32) in the Qaidam Basin are similar to it. (2) The sporopollen characteristics of the K1g in the Hetao Basin reflect that its ancient vegetation was dominated by evergreen woody plants and belongs to a warm and humid subtropical climate. (3) The assemblage of Palaeocene Funing Formation (E1f) in Subei Basin was Pterisisporites undulatus-Ulmipollenites minor-Taxodiaceaepollenites hiatus. The climate type was humid north temperate climate, vegetation was mainly deciduous trees and evergreen woody plants. (4) Leiosphaeridia/Granodiscus, Pediastrum and Botryococcus were also detected in the E1f of Subei Basin. The appearance of these algae indicates the special saline water environment and good hydrocarbon potential. [ABSTRACT FROM AUTHOR]

Total organic carbon (TOC) content of source rocks is usually determined by geochemical analysis of samples, but this process takes a long time and costs a lot. Using high-resolution and continuous logging information to evaluate the TOC content can solve the above problems. Previous studies have shown that there are certain differences in the response of logging curves such as spontaneous potential (SP), acoustic interval transit time (AC), natural gamma ray (GR), resistivity (Rt) and density (DEN) to TOC. Based on the response characteristics, this article uses the logging data of nine wells in Wenchang A and Wenchang B depressions to predict TOC by multiple regression method, and proves its accuracy by comparing with the density logging method and ΔlogR method. In addition, the influencing factors of logging evaluation are discussed: ① Type difference of parent rock affects the structural evolution and reservoir conditions of upper strata; ② Different clay mineral compositions lead to the difference in the distribution of argillaceous types and content, thus affecting the logging data. Therefore, clarifying the factors affecting logging evaluation and establishing effective prediction models in different blocks have important guiding significance for oil and gas exploration and development in the Zhu III sub-basin. [ABSTRACT FROM AUTHOR]

The alkaline lacustrine source rock developed in Fengcheng Formation is the main source of Mesozoic oil and gas in the Mahu Sag of the Junggar Basin. The study is related to the Total organic carbon (TOC) evaluation of the Fengcheng source rock. Utilizing the improved ΔlogR method and multiple regression of logging data on the SPSS software, the TOC logging calculation model of the Fengcheng source rock has been obtained. Results show that the Fengcheng source rock in the western slope of the Mahu Sag is concentrated in the longitudinal direction. The TOC values are more than 0.6%, and the highest value is greater than 2.0%. TOC gradually decrease from west to east on the plane. [ABSTRACT FROM AUTHOR]