| Popis: |
Since the gas generation of Lower Paleozoic marine shale, it has suffered from strong structural transformation, resulting in complex enrichment law of shale gas in Nanchuan area. In order to reveal the constraints of Mesozoic and Cenozoic tectonic deformation to shale gas enrichment, through fine structural analysis, and the analysis of evolution time series, and main controlling factors of shale gas enrichment, the structural model is constructed, the Mesozoic and Cenozoic tectonic evolution process is restored, the main controlling factors of shale gas enrichment are determined, and then the response relationship between structural style and shale gas enrichment model is analyzed. The study shows that the tectonic deformation strength gradually weakens from east to west in Nanchuan area, and there are two propagation structural modes: strong thrust fold-break-slip in the northern section and strong thrust fold-break slip in the south ones.In the middle Yanshan period, the main NE trending structures were developed, and Pingqiao and Dongsheng structures were formed in the time. At the end of the middle Yanshan period, due to Jinfoshan uplift and Nanchuan-Zunyi fault, the southern section underwent structural superposition and transformation. The early NE trending structure evolved into a north dipping monocline, and a nearly SN Yangchungou anticline was developed on the east side of Nanchuan-Zunyi fault. Due to differential structural deformation, anticlinal shale gas rich structural style is developed in the fault fold belt, and the shale gas rich structural style is monoclinic in the outer edge belt in the north section, while monoclinic and anticline ones are developed in the structural superposition belt in the southern section. The preservation conditions of shale gas are restricted by the structural deformation mode. The preservation conditions of shale gas gradually become better from east to west in the northern section, while the shale gas ones are more complex in the southern section. Among them, three structural styles such as low angle monocline, wide and gentle anticline and wide and gentle anticline are favorable shale gas enrichment structures in the northern section. |
