Does shale oil develop in small continental sags?

Dec. 29,2021
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The great success of exploration and development of marine shale oil in North America has triggered the shale oil revolution. In recent years, breakthroughs have been made in shale oil exploration in China’s Bohai Bay and Songliao basins, revealing that continental shale oil has good development prospects. Shale oil is found in source rocks, which are widespread in petroleum-bearing basins. However, shale oil accumulation requires multi-factor coupling such as source, storage, and preservation. The Subei Basin is a typical continental faulted lake basin with relatively low abundance of oil and gas resources. What kind of lithological combination does it develop? How rich is the organic matter? Where is the main storage space? Does it have the favorable conditions for the formation of shale oil? Where are the favorable exploration zones?

ZAN Lin, LUO Weifeng, YIN Yanling, JING Xiaoming (Wuxi Research Institute of Petroleum Geology, PEPRIS, SINOPEC) published a paper named “Formation conditions of shale oil and favorable targets in the second member of Funing Formation in Qintong Sag, Subei Basin” in “Petroleum Geology & Experiment”. The favorable targets of shale oil exploration were optimized based on the analyses of hydrocarbon generation, reservoir conditions and oil enrichment of the shale sections in the second member of Funing Formation in the Qintong Sag, Subei Basin. Some favorable zones were predicted according to the properties of lithology, pressure and fractures. The research has certain theoretical and practical significance for deepening the understanding of shale oil exploration potential in moderate thermal evolution basins.

The organic-rich mud shale in the second member of the Funing Formation of the Qintong Sag is thick and widely distributed. It is moderately thermally evolved, and has good organic matter types, providing a material basis for the formation of shale oil. The lithology of the second member of Funing Formation is mainly lime-bearing mudstone and lime mudstone. The shale has developed various pores such as dissolved pores and intercrystalline pores among clay minerals and carbonate minerals. Laminae and micro-fractures control the permeability of the reservoir. From the third to the fifth section of the second member of Funing Formation, the content of brittle minerals is high, mainly composed with quartz, calcite and dolomite. The free hydrocarbon content (S1) is high, referring the most favorable layers for shale oil exploration of the sections mentioned above. The Shiyan and Chujialou depression zones in the Qintong Sag are the most favorable areas for shale oil accumulation.

The results of the study were published in “Petroleum Geology & Experiment”, Volume 43, Issue 2, 2021.

Corresponding Author: ZAN Lin
CNKI Press Officer: LI Jingjing YANG Na

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