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- Title
川中磨溪—龙女寺构造中二叠统茅口组白云岩 成因分析.
- Authors
徐 婷; 袁海锋; 陈 聪; 张玺华; 山述娇; 匡明志; 谌 辰; 叶子旭; 李天军; 阳 聪
- Abstract
Early oil and gas exploration in the Permian Maokou Formation in the Sichuan Basin mainly focused on karst fracture-cavity reservoirs in the Shunan region. In recent years, a number of drilled dolomite reservoirs in the Maokou Formation in the central Sichuan Basin have obtained high-yield industrial gas flow, demonstrat⁃ ing the great exploration potential. In this paper, we take the Moxi-Longnvsi area in central Sichuan Basin as the research object. Through the analysis of drilling and logging data, the genesis of dolomite reservoirs were discussed by means of core observation, thin section identification, cathodoluminescence, in-situ micro-elemental and chronology analysis and carbon and oxygen isotopes and other methods. Two main types of dolomite are present in the P2m² section: the first type is matrix dolomite, mainly composed of gray fine-medium crystal dolomite and fine-medium crystal dolomite, with dark red light under the cathode ray, low Fe content, and similar rare-earth partitioning model to micrite. δ13C,δ18O isotopic values and 87Sr/86Sr values are within the Permian seawater range values, and the U-Pb age of the matrix dolomite is 263±15 Ma, indicating that the dolomitization time is symbiotic- perisogamy-early shallow burial period, and the dolomitization fluid is mainly the same period seawater in a more restricted environment during the P2m² sedimentary period, which laid the foundation of the reservoir development in the P2m² section. The second type is filled dolomite, mainly composed of medium crystal dolomite and saddle dolomite, with red light under the cathode ray, lower content than matrix dolomite, higher Mn content, lower Sr element content, high 87Sr/86Sr value and rare-positive Eu anomaly feature in earth partitioning model, indicating that the dolomitization fluid is mainly hydrothermal fluid in this period and the dolomitization time is buried period. The study concluded that the development of dolomite is mainly controlled by the P2m² sedimentary facies zone, the dolomitization time is early, and the development of scale porosity is earlier than the oil and gas filling, and the achieved results can be used for reference to search for scale quality reservoirs and exploration deployment in the Maokou Formation.
- Subjects
DOLOMITE
- Publication
Natural Gas Geoscience, 2024, Vol 35, Issue 1, p13
- ISSN
1672-1926
- Publication type
Article
- DOI
10.11764/j.issn.1672-1926.2023.08.014