Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (4): 898-908.doi: 10.11743/ogg20210411

• Petroleum Geology • Previous Articles     Next Articles

Characteristics and favorable plays for high-quality reservoirs in the Middle Triassic Lei 4 Member, Yuanba area, northeastern Sichuan Basin

Jinbao Duan(), Mindong Jin, Zhiwei Fan, Xiang Zhu, Yanting Liu   

  1. Exploration Company, SINOPEC, Chengdu, Sichuan 610041, China
  • Received:2020-10-12 Online:2021-08-28 Published:2021-08-27

Abstract:

For the purpose of further enhancing the success rate of exploratory wells emplaced in the superposed shallow-karst reservoirs in the 4th member of Leikoupo Formation (hereinafter referred to as Lei 4 Member) to achieve efficient exploration and development in northeastern Sichuan, we comprehensively analyze the reservoir characteristics and major control factors based on rich data from borehole observation, coring and lab analysis.The results show that (1) the Lei 4 Member in the study area is of intraclastic grainstone shoal facies with reservoirs mainly developed in the doloarenite and karst breccia; and the dominant reservoir space is karst caverns and fractures, featuring relatively strong heterogeneity.(2) The analysis of the reservoir genetic mechanism shows that the original pore system of the shoals of tidal flat facies serves as the material basis for high-quality reservoir development.A mass of reservoir space formed by the transformation of karstification is a factor critical for the reservoir development.Thermal dissolution in the burial stage could further improve the reservoir quality.(3) The karstification shows identification markers special to mechanical filling and chemical reaction, and the property of karst fluid and its activity routines in the different karst geomorphic units serve to determine the reservoir quality.The karst mound-platform, which is near source rock laterally and/or has well-developed fracture system, is a desirable zone for future exploration in the northeastern Sichuan Basin.

Key words: karstification, thermal dissolution, shallow, reservoir characteristics, Triassic, Yuanba area, Sichuan Basin

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