Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (2): 390-406.doi: 10.11743/ogg20220212

• Petroleum Geology • Previous Articles     Next Articles

Influence of the Cretaceous fine-grained volcanic materials on shale oil/gas, Luanping Basin

Xiaoning Liu(), Zaixing Jiang, Xiaodong Yuan, Chen Chen, Cheng Wang   

  1. [School of Energy Resources,China University of Geosciences (Beijing),Beijing 100083,China]
  • Received:2021-07-02 Revised:2022-01-18 Online:2022-04-01 Published:2022-03-11

Abstract:

Industrial shale oil/gas flow was successfully tested in Well Luanye 1 after fracturing, and the Cretaceous Xiguayuan Formation in the Luanping Basin has currently been a key zone of hydrocarbon exploration and research in this area. Recent petrological studies on Well Luanye 1 show that fine-grained volcanic materials have been discovered in the source rocks and are closely related to the generation and accumulation of shale oil/gas. It has become a new proposition to explore the relationship between fine-grained volcanic materials and shale oil/gas. The lower member of Xiguayuan Formation in the Luanping Basin is the target of the study with a combination of analyses and laboratory data such as cores, microscopic thin sections observation, logging, X-ray diffraction and geochemical test. The sedimentary characteristics and organic matter development of the fine-grained tuffaceous sedimentary rocks are discussed to provide theoretical support for further exploration and development of shale oil/gas in the area. On the other hand, the development of lower member of Xiguayuan Formation is controlled by volcano-lacustrine interaction, with lacustrine shale, fine-grained tuffaceous sedimentary rocks under the effect of volcanic activities, as well as andesite and pyroclastic rocks of volcanic facies well developed within. The results show that in the shale, the average TOC content is 0.64 %, and the average S1+S2 content is 0.41 mg/g; in the fine-grained tuffaceous sedimentary rocks, the average TOC content is 1.92 %, and the average S1+S2 content is 2.64 mg/g, indicating that the abundance of organic matters is markedly greater in the fine-grained tuffaceous sedimentary rocks. Pyrite framboids are widely developed in the intervals where fine-grained volcanic materials are enriched; meanwhile, Pr/Ph is smaller and V/(V+Ni) is larger, also indicating a strong reduction of water environment after volcanic eruption. The rapid deposition and burial of fine-grained volcanic materials is conducive to the preservation of organic matters. Lacustrine carbonate rocks are well developed and interbedded with laminated organic-rich mudstone and tuff. The interlayer fractures are conducive to hydrocarbon migration, while the tuff and dolomite laminae provide reservoir spaces. The fine-grained volcanic materials play a positive role in the complete process from the enrichment and hydrocarbon generation of organic matters to the storage and preservation of oil/gas.

Key words: fine-grained volcanic material, rock type, shale oil/gas, Xiguayuan Formation, Cretaceous, Luanping Basin

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