Analysis of Structural Formation Evolution and Reservoir Control Effect of No. 8 Coal Seam in X Area, Eastern Ordos Basin

Xiao-jiao GUO , Zhi-di LIU , Gui-zhen LIU , Jian-bo HU , Cheng-wang WANG , Xin JIN

Science Technology and Engineering ›› 2024, Vol. 24 ›› Issue (29) : 12431 -12441.

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Science Technology and Engineering ›› 2024, Vol. 24 ›› Issue (29) : 12431-12441 DOI: 10.12404/j.issn.1671-1815.2309424
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Analysis of Structural Formation Evolution and Reservoir Control Effect of No. 8 Coal Seam in X Area, Eastern Ordos Basin
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Abstract

The regional enrichment of coalbed methane in the Benxi Formation of the X region in the eastern Ordos Basin is evident from production data, and it is believed to be correlated with tectonic structures. However, a clear comprehension of the enrichment patterns and geological theories remains unclear. To address this, an analysis of the tectonic evolution of the coal seams in the X region was conducted. This analysis compared the thermal evolution history and hydrocarbon generation history obtained from wells, aiming to clarify the controlling role of tectonic evolution on the enrichment of deep coalbed methane. The results indicates that the hydrocarbon generation in the coal seams of the Benxi Formation primarily occurred during two periods: the late Permian-early Triassic and the late Jurassic-early Cretaceous, with significant generation during the latter. During these periods, the ancient structures overlying the coal seams exerted a controlling influence on the enrichment and high production of coalbed methane, with a more pronounced effect observed during the second period. In particular, methane accumulated primarily in the low-lying areas of these structures. The study area is affected by multiple tectonic movements, leading to a No. 8 preferential concentration of coalbed methane in the gently sloping sections of the current structures overlying the coal seams. Conversely, steep slope sections exhibit minimal or no enrichment. Furthermore, a decrease in the structural height overlying the coal seams is associated with an increasing trend in gas production. A comprehensive analysis of the tectonic evolution history suggests that the enrichment and high production of deep coalbed methane are primarily controlled by ancient structural depressions formed during the second hydrocarbon generation period and subsequent uplift processes. These findings provide a solid geological theoretical basis for understanding the internal control mechanisms of ancient structures on reservoirs and the genesis of deep coalbed methane enrichment and high production.

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Ordos Basin / deep coalbed methane / tectonic evolution / paleotectonics / possession analysis

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Xiao-jiao GUO, Zhi-di LIU, Gui-zhen LIU, Jian-bo HU, Cheng-wang WANG, Xin JIN. Analysis of Structural Formation Evolution and Reservoir Control Effect of No. 8 Coal Seam in X Area, Eastern Ordos Basin. Science Technology and Engineering, 2024, 24(29): 12431-12441 DOI:10.12404/j.issn.1671-1815.2309424

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