论文部分内容阅读
Most of petroliferous sedimentary basins in China have experienced multiple phases of tectonic evolution and deposition, and are characterized by tectonic and depositional superimposition. The term “superimposed basin” is suggested to describe those basins which consist of two or more simple prototype basins superimposing vertically and/or coalescing later-ally. The characteristics of petroliferous superimposed basins are “multiple stages of basin forming and reworking, multiple layers of source rocks, multiple periods of hydrocarbon genera-tion and expulsion, multiple periods of petroleum migration-accumulation-escape”. Therefore, applying the wave process analysis method to studying the process of basin formation, hydro-carbon generation, and reservoir formation, and then establishing theory of “petroleum accumu-lation system” is helpful to enhancing petroleum exploration efficiency in superimposed basins. This paper will, based on case study in the Tarim basin, report the major developments in studying basin formation, hydrocarbon generation and petroleum accumulation. In study of basin formation, (1) geophysical comprehensive profiles reveal that the Tarim plate has been sub-ducted beneath the Tianshan orogenic belt with an interfinger structure and that the deep struc-ture in the eastern section of the Tianshan orogenic belt is different from that in the western sec-tion. (2) The vertical variation in debris and geochemical composition reveals the nature and Mesozoic-Cenozoic evolution history of the Kuqa Depression. (3) Field investigation and paleo-stress reconstruction show that the Kuqa Depression has undergone gravity-driven extension in sedimentary cover when the Tianshan uplifted vertically. In hydrocarbon generation study, new developments include (1) setting environmental index to judge high grade source rocks in marine carbonates, and (2) establishing the lower limit of the organic carbon content for effective car-bonate source rocks. In petroleum accumulation study, (1) methods of determining paleopres-sure and paleotemperature of forming fluid inclusions have been established. (2) The petroleum source analysis has indicated that the erude oil in the Lunnan and Tahe oilfields are derived from the source rocks of the Middle and Upper Ordovician. (3) Three generations of oil inclusions from the Lunnan oilfield have been recognized and dated.