Discussion on Enrichment Law of Organic Matter in Continental Shale with Clue of Primary Productivity and Carbon Storage Law
It is generally believed that it is easy to enrich oil and gas in deep-water environments such as deep lacustrine to semi-deep lacustrine in continental basins,but a large number of shale gas exploration has proved that shale gas reservoirs are generally located closer to the edge of lacustrine basins,so it is necessary to further study the law of organic matter enrichment in continental lacustrine basins.In this paper,the metallogenic conditions of shale oil,gas and coal are compared by analogy method.Combined with the primary productivity of the lake,the rate of carbon sequestration and fossil development,the paleo-geomognomy and burial history recovery means are used to put forward six evidence that shale developed in shallow water restricted environment.It is found that shale oil,gas and coal have similar metallogenic patterns,and have a symbiotic relationship with coal and evaporative salt in shallow water environment.The carbon sequestration rate in shallow water environment is much higher than that in deep water environment.The conclusion is that shale oil and gas are enriched in closed to semi-closed environment such as shallow lake bay and interbay.The condensed section of the maximum flood period should be the organic-poor section.Finally,the results are verified in Songnan area,indicating that this conclusion is universal and can guide shale oil and gas exploration better.
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