Abstract: Sebei No.1 gas field is now the largest unconsolidated sandstone gas field in China, with alternative gas and water layers, multi-thin layers and edge water. In the gas field development, the gas wells often produce water, so the control of water production is the one of the technical problems. This paper, on the basis of fine description of gas reservoirs, studies the characteristics of water production and gas production curves, water gas ratio value and its increased law to all wells in one layer of the gas reservoirs, analyzes the main water sources and the cause of water production. The water production in these wells is classified into four types, namely, the low water yielding and stable type, the low water yielding and slow growth type, the moderate water yielding and fast growth type and high water yielding and sharp growth one. According to the water production situations in different types of wells, the effective measures for water control are proposed by the classification. Field application of the measures showed good results.

Key words: Qaidam basin, Sebei No.1 gas field, unconsolidated sandstone, water gas ratio, performance analysis