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Jiang Y.,Key Laboratory of Natural Gas Geology | Jiang Y.,Southwest Petroleum University | Tao Y.,Key Laboratory of Natural Gas Geology | Tao Y.,Southwest Petroleum University | And 11 more authors.
Petroleum Exploration and Development | Year: 2016

The formation conditions, existence evidence, modification modes and timing of hydrothermal dolomitization in the Sinian Dengying Formation are studied based on the basic geological conditions, mineral assemblages in dolomites, and geochemical features of the Gaoshiti-Moxi area in the Sichuan Basin. The Gaoshiti-Moxi area is a significant exploration target of the Sinian Dengying Formation in the Sichuan Basin and has the basic conditions of regional geology for the occurrence of structurally controlled hydrothermal dolomitization: (1) activity of extensional basement-fault; (2) deep-burial hydrothermal reservoirs; (3) the overlying seal strata. Based on the petrographic analysis and geochemical tests (trace elements (Fe and Mn), stable isotopes (C, O, and Sr), homogenization temperature of fluid inclusions, etc.) of the core samples of the Dengying Formation in the study area, combing with the MVT mineral assemblages and geochemical characteristics, the study demonstrates that structurally controlled hydrothermal dolomitization exists in the Dengying Formation of the study area. This type of hydrothermal dolomitization refers to transformation of matrix dolomites by hydrothermal fluids and it consists of three modes: (1) dissolution and cementation; (2) recrystallization and neomorphism; (3) hydrofracturing. It is inferred that there exists multi period of hydrothermal dolomitization, namely, Late Sinian to Early Cambrian, Late Devonian and Late Permian. © 2016 Research Institute of Petroleum Exploration & Development, PetroChina.


Jin M.,Key Laboratory of Natural Gas Geology | Jin M.,Petrochina | Jin M.,Southwest Petroleum University | Zeng W.,Key Laboratory of Natural Gas Geology | And 13 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2014

Based on data from boreholes, cores and lab analysis, the characteristics, genesis and controlling factors of different types of reservoirs in Cambrian Longwangmiao Formation, Moxi-Gaoshiti area, Sichuan Basin, are examined, and the distribution of favorable reservoir zones is predicted. The reservoirs can be subdivided into four types according to the different types of reservoir space and their combination with the "piebald" karst system: pinhole, "piebald" pinhole, cave, and "piebald" cave. Among them, the "piebald" cave reservoir is the best in quality, followed by the cave and "piebald" pinhole reservoirs, and the pinhole reservoir is the worst in quality. The genesis and controlling factors of Longwangmiao Formation reservoir are that the regional shoal deposition gave rise to a large area of grain dolomite, the layers with intergranular pores and small amount of intragranular dissolution pores of shoal facies provide a material base for later karst reformation. During the Caledonian period, the karst water flowing and corroding along the porous bed formed previously played a key role in the formation of premium reservoirs. During the period of the Caledonian-Hercynian, the tectonic paleogeomorphology controlled the fluid potential of karst water, which in turn decided the development of reservoirs. Karst is most developed on the slope of the paleotopography (along the well line of Moxi 201-Moxi 9-Moxi 12), where "piebald" cave or cave reservoirs usually occur, which are the most favorable reservoir zones. ©, 2014, Science Press. All right reserved.


Jiang Y.,Key Laboratory of Natural Gas Geology | Jiang Y.,Southwest Petroleum University | Tao Y.,Key Laboratory of Natural Gas Geology | Tao Y.,Southwest Petroleum University | And 11 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2016

The formation conditions, existence evidence, modification modes and timing of hydrothermal dolomitization in the Sinian Dengying Formation are studied based on the basic geological conditions, mineral assemblages in dolomites, and geochemical features of the Gaoshiti-Moxi area in the Sichuan Basin. The Gaoshiti-Moxi area is a significant exploration target of the Sinian Dengying Formation in the Sichuan Basin and has the basic conditions of regional geology for the occurrence of structurally controlled hydrothermal dolomitization: (1) activity of extensional basement-fault; (2) deep-burial hydrothermal reservoirs; (3) the overlying seal strata. Based on the petrographic analysis and geochemical tests (trace elements (Fe and Mn), stable isotopes (C, O, and Sr), homogenization temperature of fluid inclusions, etc.) of the core samples of the Dengying Formation in the study area, combing with the MVT mineral assemblages and geochemical characteristics, the study demonstrates that structurally controlled hydrothermal dolomitization exists in the Dengying Formation of the study area. This type of hydrothermal dolomitization refers to transformation of matrix dolomites by hydrothermal fluids and it consists of three modes: (1) dissolution and cementation; (2) recrystallization and neomorphism; (3) hydrofracturing. It is inferred that there exists multi period of hydrothermal dolomitization, namely, Late Sinian to Early Cambrian, Late Devonian and Late Permian. © 2016, Science Press. All right reserved.

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