Origin of Upper Triassic formation water in middle Sichuan Basin and its natural gas significance

• Main Authors: Li Wei, Yang Jinli, Jiang Junwei, Liu Jimin, Liu Zongcheng
• Format: Article
• Language: English
• Published: KeAi Communications Co., Ltd. 2009-08-01
• Series: Petroleum Exploration and Development
• Online Access: http://www.sciencedirect.com/science/article/pii/S1876380409601385

The formation water of Upper Triassic Xujiahe Formation in the middle Sichuan Basin is of high salinity in most areas and of low to medium salinity locally. All the formation water lack sulphate ion implying good reducing and sealing conditions, but are rich in barium ion. The forming environment of the Xujiahe formation water is similar to that of the Jurassic formation water, but very different from that of the underlying marine formation water. The Xujiahe formation water has lower sodium (potassium) chloride coefficients and higher metamorphism coefficients. The water shows the characteristics of original continental sedimentary formation water reworked by later marine water of high salinity. In reworking the reservoirs, surface water of high sulphate ion content should be avoided, and also quick changes of formation temperature, pressure and chemical equilibrium should be avoided to prevent precipitates from blocking pores and throats. Key words: Sichuan Basin, Upper Triassic, formation water, origin, geological significance