| Author's Name: ZHU Chao, LIU Zhanguo, WANG Bo, GONG Qingshun, WANG Yanqing,
TANG Pengcheng, WEI Xuebin, WU Kunyu, TANG Li, ZHANG Na |
| Based on outcrop, drilling, seismic and a large number of experimental analysis data, from the aspects of
current stratigraphic structure, subsidence rate, deposition rate, paleosalinity, rock assemblage and sedimentary facies
distribution, organic matter types of source rocks, it is demonstrated that a large underwater paleouplift (central
paleouplift) is developed between Chaixi Depression and Yiliping Depression in Qaidam Basin. The tectonic evolution of
the central paleouplift is analyzed through structural analysis and paleogeomorphic restoration. Finally, the significance of
hydrocarbon accumulation in the paleouplift for the next oil and gas exploration is expounded. The results show that: (1)
In the early Paleocene, influenced by the early Himalayan compression orogeny, the prototype of paleouplift was formed,
which is distributed in a NW-SE direction on the plane, separating the Chaixi Depression on the west side and the
Yiliping Depression on the east side. The paleouplift has good inheritance from Eocene to Oligocene, and the maximum
area of the uplift area in Lower Ganchaigou period is about 3 500 km2. In the late Miocene, the paleouplift evolved into a
wide and gentle slope due to the eastward migration of Chaixi sedimentary center and the north-south provenance supply.
(2) The central paleouplift controls the formation of oil and gas reservoirs, hydrocarbons and reservoirs. Large-scale delta
sand bodies are developed in the near provenance areas at the north and south ends of the central paleouplift, while the
central main area far away from the provenance is in an undercompensated salinized water environment, and large-scale
lacustrine carbonate reservoirs are developed there. Influenced by the separation of paleouplift, it has been confirmed that
high-quality salinized lacustrine source rocks are developed in Chaixi Depression in the west during Lower Ganchaigou
to Upper Ganchaigou period, and effective source rocks may be developed in Yiliping Depression in the east. As a
directional area for oil and gas migration, the paleouplift is conducive to hydrocarbon accumulation and can serve as the
next favorable exploration zone. |
