Characteristics of Pyrite in Shale and Its Application in Shale Gas Enrichment Evaluationa Case Study of Longmaxi Shales in the Xiang'exi Depression, China

作者：Huang, Yuqi^*; Zhang, Jinchuan; Zhang, Peng; Tang, Xuan; Liu, Chengwei

来源：Energy & Fuels, 2023, 37(16): 11942-11954.

DOI：10.1021/acs.energyfuels.3c01598

• FRAMBOIDAL PYRITE
• SULFUR ISOTOPE
• MORPHOLOGY
• PALEO
• GENERATION
• SEDIMENTS
• MEMBER
• BASIN

Exploration and development of shale gas in China havemade significantbreakthroughs in recent years. Longmaxi shales in the Xiang'exidepression are the key targets for shale gas exploration in the middleYangtze region. However, systematic studies on the authigenic mineralsand their application in shale gas enrichment evaluation are insufficient.Therefore, in this study, pyrite was selected to characterize itsmorphology, grain size, and distribution characteristics, with thehope to identify the favorable exploration target of Longmaxi shalesin the Xiang'exi depression. Herein, 44 unweathered core sampleswere collected from well LD-1 for experiments. The results show thatLongmaxi shales can be divided into four lithological segments fromthe bottom to the top. L4 high-carbon clayey shale facies andhigh-carbon siliceous shale facies, exhibits the characteristics ofan anoxic environment with a medium pyrite content, due to the insufficientsupply of ferric ions. L3 medium-carbon siliceous shale facies,shows the characteristics of a hypoxic environment, with enhancedterrestrial supply and increased pyrite content. L2 low-carbonsiliceous shale facies, has the characteristics of an aerobic environmentwith strong terrestrial supply, leading to a low content of pyrite.L1 medium-carbon clayey shale facies, shows the characteristicsof a hypoxic environment similar to L3 but with the highest pyritecontent among the four segments. Further research shows that the presenceof pyrite is conducive to the development and preservation of organicpores, and shale with a higher pyrite content shows larger gas contentand desorption gas/total gas content ratio, showing a greater explorationand development potential. Combined comprehensive analysis concludesthat in the Xiang'exi depression, L4 of the Longmaxi shaleis the optimal exploration target segment, followed by L1, then L3,while the L2 segment shows the lowest exploration potential.

• 单位
  中国地质大学（北京）; 六盘水师范学院