Shale Gas Exploration Potential Analysis and Accumulation Conditions of the Lower Cambrian in the Southern Margin of the Ordos Basin, China

Abstract

The Lower Cambrian shale is a relatively high-quality source rock in the southern margin of the North China Craton. According to data of geochemistry，X-ray diffraction, electron microscope scanning, energy spectrum, etc., the accumulation conditions of the Lower Cambrian shale gas in the southern margin of the Ordos Basin were systematicly investigated. Compared with major gas producing shales in the U.S., the lower Cambrian shale was characterized by abundance of organic carbon, high maturity, high brittle minerals and developed organic matter pores, which has good accumulation conditions for shale gas and better exploration potential. 1) a set of high quality source rocks developed in the southern margin of Ordos basin with a thickness up to 60m.The Lower Cambrian shale has a high organic matter abundance with the mean up to 3.14% and the highest of 11.18%, and the types of the organic matter (mainly type II, partly type I) are favorable. The shales are in the high- and over-mature phase at present. 2) The content of brittle minerals such as quartz, feldspar and dolomite is high, and it is easy to form natural cracks and improve reservoir seepage capacity, which is conducive to the development of shale gas reservoirs. 3) The rich organic matter pores, especially quartz, feldspar and pyrite, found a large number of micro-nano pores, provided a high-quality place for the enrichment of shale gas. 4) Compared with the shale gas content of the Qiongzhusi Formation in the Sichuan basin, the Lower Cambrian shale in the Ordos basin has a high gas content and has a good prospect for exploration. The breakthrough of Lower Cambrian shale gas exploration in Sichuan basin provides a new perspective for the shale gas exploration throughout the Ordos basin. The Lower Cambrian high-quality shale is a favorable exploration layer in the southern margin of the Ordos basin and has great exploration potential.

AAPG Datapages/Search and Discovery Article #90333©2018 AAPG Middle East Region, Shale Gas Evolution Symposium, Manama, Bahrain, December 11-13, 2018