POTENTIAL STRUCTURAL TRAPS ASSOCIATED WITH LOWER CARBONIFEROUS SALT IN THE NORTHERN TARIM BASIN, NW CHINA
Jiangyu Zhou*#, Zhongmin Lin**, Chuangrong Luo and Xiepei Wang#
* Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, PO Box 1131, Wushan, Guangzhou 510640, P. R. China.
** Northwest Bureau of Petroleum Geology, CINOPEC, Urumqi 83001, P. R. China.
*** Research Institute of Petroleum Exploration, CINOPEC, Jingzhou, Hubei 434100. P. R. China.
# Present address: Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, P. R. China.
Author for correspondence, email: zjy522@cug.edu.cn
In the Aixieke-Santamu area of the northern Tarim Basin (NW China), 45 relatively low amplitude structures related to the plastic flow of Lower Carboniferous salt have been discovered in the Lower Carboniferous Kalashayi Formation and the Middle-Upper Triassic Akekule and Halahatan Formations. Three small hydrocarbon accumulations have so far been located at the margins of a Lower Carboniferous salt body (measuring about 55km × 75km and 115-225m thick, controlled by wells and 2D and 3D seismic sections). In this paper, we consider the development of this salt body and discuss possible reasons why vertical diapirs are absent from the study area. We attempt to develop a model of salt flow and we investigate the relationship between salt flow and the occurrence of oil and gas traps.
Using recently-acquired high-resolution 2D and 3D seismic profiles, we show that the Lower Carboniferous salt has undergone three separate phases of plastic flow. At the end of the Early Permian, the salt flowed southwards by 2.0-2.8 km; then, during the Late Triassic -- Early Jurassic, it flowed in the same direction by 1.0-1.8 km; and finally at the end of the Tertiary, it flowed northwards by 0.6-1.5 km. These movements resulted in the formation of various types of structural trap in the Kalashayi, Akekule and Halahatan Formations including salt ridge anticlines, domes and marginal troughs. Salt ridge and salt edge low-amplitude anticlines are probably the most important targets for future hydrocarbon exploration.