Hydrogeology geochemical characteristics of continental formation water in Xinchang gas field,western Sichuan depression and gas migration and accumulation
Zhou Xiaoxin1, Lou Zhanghua2, Zhu Rong2, Zhu Hongquan3, Li Huaji3, Li Fei1
1. Institute of Hydrology and Water Resources, College of Civil Engineering, Zhejiang University, Hangzhou 310058;
2. Department of Ocean Sciences and Engineering, Zhejiang University, Hangzhou 310058;
3. SINOPEC Southwest Oilfield Company, Chengdu 610081
Xinchang gas field is the main gas production district of Chuanxi depression. The gas-bearing beds are deep Xujiahe Formation (Section 2 and 4) of the Upper Triassic and Middle-Upper Jurassic (Shangshaximiao Formation and Penglaizhen Formation), which all produce groundwater more or less. It indicates that there is complex relationship between gas and groundwater. Inherent connections of liquid exist between shallow-middle fluid and deep fluid. Low salinity, low coefficient of salinization and high HCO3- ionic concentration in the formation (depth between 500～2 200 m) may resulted from the frequency exchange of shallow-middle formation water in vertical. The formation water with the characteristics of high salinity and high coefficient of salinization in the depth of 3 000～5 500 m are mainly contributed by the formation water concentrated gradually with the depth increase. The formation water presented the characteristics of intermingling water in the depth of 2 200 m～3 000 m. The characteristics of formation water salinity on horizontal distribution in Jurassic formation are different from the characteristics in the Upper Triassic. The salinity of formation water in Shangshaximiao Formation is high in the fault district while it is relative low in Section 2 of the Upper Triassic at the corresponding district. The deep liquid connected with shallow-middle liquid by the fault. The shallow-middle formations are filled with high salinity formation water in the fracture district while the gas gathered in the favorable traps in a certain distance away from the faults in shallow-middle formation.
. Hydrogeology geochemical characteristics of continental formation water in Xinchang gas field,western Sichuan depression and gas migration and accumulation[J]. Chinese Journal of Geology, 2015, 50(1): 330-339.