Paper No. 53-13
Presentation Time: 4:45 PM
THE CAUSES OF HIGH-CONTENT NITROGEN IN SHALE GAS: A CASE STUDY OF THE LOWER CAMBRIAN OF THE XIUWU BASIN, CHINA
HUANG, Yizhou1, JIANG, Zhenxue2, SONG, Yan3, ZHANG, Kun4, JIANG, Shu5, JIA, Chengzao6, LIU, Weiwei7, WEN, Ming1, XIE, Xuelian8 and LIU, Tianlin9, (1)Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102249, China, (2)Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China, (3)Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China; Research Institute of Petroleum Exploration and Development, Beijing, 100083, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102249, China, (4)Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China; Energy & Geoscience Institute, University of Utah, Salt Lake City, UT 84108; Unconventional Petroleum Collaborative Innovation Center, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China; Research Institute of Petroleum Exploration and Development, No.20, Xueyuan Road, Haidian District, Beijing, 100083, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China, (5)Energy & Geoscience Institute, University of Utah, Salt Lake City, UT 84108, (6)Research Institute of Petroleum Exploration and Development, No.20, Xueyuan Road, Haidian District, Beijing, 100083, China, (7)Jiangxi Provincial Natural Gas Company, Ltd., Nanchang, 330000, China, (8)Guangzhou Marine Geological survey, Guangzhou, 510760, China, (9)State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102249, China; Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China
There are successes and failures in the exploration of marine shale gas in South China. In some shale gas blocks with good basis of hydrocarbon generating materials, the phenomena exists that the wells drilled are lack in gas but with high nitrogen content. As nitrogen is an indicator that directly reflects the preservation conditions of oil and gas, the study of nitrogen in shale will help to find out the regulations of the preservation and enrichment of hydrocarbon gases.
This study focuses on the Lower Cambrian shale in Xiuwu Basin, Yangzi area, with emphasis on the detailed study of the Jiangye-1 well, using gas component analyses, nitrogen isotope analyses, permeability tests in parallel and perpendicular direction and FIB-HIM experiments, also combining with seismic interpretation, core description, outcrops observation and other methods to study the generation of high nitrogen and low hydrocarbon in the Lower Cambrian shale, Xiuwu Basin.
The result shows that the nitrogen in the Lower Cambrian shale of the Xiuwu Basin is derived from the atmosphere and the deep crust-upper mantle. The shale stratification plane and the detachment layer in the bottom of the Lower Cambrian are the lateral passage for shale gas migrating to syncline limbs, and the widely developed deep faults are the vertical passage for shale gas diffusing into atmosphere. The nitrogen in the atmosphere also enters the shale reservoir in the same way along the stratification plane, the Lower Cambrian detachment layer and the deep faults. In the Jurassic, on the one hand, the volcanism on the basin margin increased the value of the paleo heat flow, promoted the graphitization of organic matter in shale and the collapse of organic pore, accelerating the loss of shale gas. On the other hand, it brought nitrogen from the deep crust and upper mantle of the crust. This study summarized diffusion pattern of shale gas, revealing the genesis of high nitrogen and low hydrocarbon in the plate-active region.
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