Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (5): 1337-1354.doi: 10.11743/ogg20240510

• Petroleum Geology • Previous Articles     Next Articles

Characteristics and main controlling factors of reservoirs in the Middle Permian Maokou Formation, Longnvsi area, central Sichuan Basin

Jun PENG1,2(), Fanglan LIU1,2(), Lianjin ZHANG3, Binsong ZHENG1,2, Song TANG3, Shun LI3, Xinyu LIANG3   

  1. 1.School of Geoscience and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    2.Natural Gas Geology Key Laboratory of Sichuan Province,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    3.Chuanzhong Oil & Gas Mine,Southwest Oil & Gas Field Company,PetroChina,Suining,Sichuan 629000,China
  • Received:2024-06-03 Revised:2024-07-06 Online:2024-10-30 Published:2024-11-06
  • Contact: Fanglan LIU E-mail:pengjun@swpu.edu.cn;liufl101260@163.com

Abstract:

In recent years, high-yield industrial gas flow has been obtained from the Maokou Formation in multiple wells such as JT1 and MX145 in the central Sichuan Basin, indicating great potential for hydrocarbon exploration and exploitation of this formation. However, the characteristics of and main factors controlling the reservoirs therein remain unclear, severely restricting in-depth hydrocarbon exploration. Aiming to investigate reservoirs of the Maokou Formation in Longnvsi area, central Sichuan Basin, the study delves into the geological characteristics such as lithology, physical properties, and pore-throat structure, along with the local geochemical characteristics via rock and ore tests under the guidance of reservoir geology. Accordingly, the major factors governing the development of high-quality reservoirs within the formation are proposed. The results indicate that dolomite and limestone reservoirs occur in the Maokou Formation, with primary reservoir rocks of crystal dolomites, brecciated dolomites, and granular limestones. The dolomite reservoir rocks can be categorized into three types and six subtypes, while the limestone reservoir rocks can be divided into four types and five subtypes. Storage spaces in the reservoirs consist primarily of intercrystalline pores, nonselective dissolution pores, and karst caves. The structural-dissolution fractured-vuggy system formed by the matching of vugs and fractures, exhibits a large storage space, extensive distribution, and high connectivity, which establish this system as a favorable reservoir. Regarding the formation and evolutionary pattern of the reservoirs, the reservoir framework is caused by sedimentation and dolomitization, and reservoir modification can be attributed to superimposed karstification and tectonism. In all, the primary factors governing the development of high-quality reservoirs include sedimentation, diagenesis, and tectonism, and brecciated dolomites are identified as high-quality reservoir rocks.

Key words: main controlling factor, evolutionary pattern, reservoir characteristics, Maokou Formation, Middle Permian, Longnvsi area, central Sichuan Basin

CLC Number: