Volcanic Rocks Distribution and Exploration Potential in Ordos Basin, China

Jianrong, Gao; Wanglin, Xu; Yanru, Guo
Research Institute of Petroleum Exploration & Development Petrochina, Petrochina, Beijing, China.

The Ordos Basin is the most important base rich in energy and minerals in western China , by the end of 2011, 28 Mesozoic oil fields have been founded in the south of the basin and 9 Neopaleozoic gas fields have been founded in the north of the basin, However, with rising levels of exploration, there is an urgent need to find the new replacing-areas . With reference to the experience of the exploration of volcanic rocks from other basins, This study provides that deep-seated volcanic rocks in the Ordos Basin are also very developed, with basic condition for natural gas accumulation.Volcanic rocks in the Ordos Basin are of mainly two types: one in the basin and the other along the margin of the basin. Besides those along the margin, the marginal volcanic rocks also include the volcanic rocks in the Yinshanian orogenic belt north of the basin. Based on the latest collection of gravitational and aeromagnetic data, here we interpret basement faults in the Ordos Basin and its peripheral region, compare the faults derived from aeromagnetic data with those from seismic data, and identify the geological ages of the fault development. Two aeromagnetic anomaly zones exist in the NE-trending faults of the southern basin, and they are in the volcanic basement formed in pre-Paleozoic. These NE-trending faults are the channel of volcanic material upwelling in the early age (Archean-Neoproterozoic), where igneous rocks and sedimentary rocks stack successively on both sides of the continental nucleus. In the Cambrian, the basin interior is relatively stable, but in the Late Paleozoic and Mesozoic, the basin margin underwent a number of volcanic activities, accompanied by the formation of nearly north-south and east-west basement faults in the basin periphery and resulting in accumulation of great amount of volcanic materials. Volcanic tuff from the basin periphery is discovered in the central basin and volcanic materials are exposed in the margins of the basin. According to the source-reservoir-cap rock configuration, the basin peripheral igneous traps formed in the Indosinian-Early Yanshanian and Late Hercynian are favorable exploration objectives, and the volcanic rocks in the central basin are the future target of exploration.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012