Abstract

Kela 2 Gas Field is a large blocked structural reservoir with bottom water in Kuqa Depression, Tarim Basin. Reservoir is mainly deposited as delta front underwater distributary channel in Bashijiqiuke Formation during Early Cretaceous. Reservoir thickness is over 460 m and average net-to-gross ratio is 78%. There developed faults in the reservoir which has strong anisotropy, porosity of the reservoir is 10 to 18% while permeability is 1-100×10-3 μm2, and fractures developed also in some areas. During 17 years of reservoir production, some wells started to produce water. Data monitor indicates that the level difference of water invasion is about 200 m between wells, and anisotropic water invasion constrains sustainable development of the gas field. This paper used core analysis, logging interpretation and seismic data to analyze faults, fractures, relationship between relatively high permeability zones and barrier beds, and it is the main control for the strong anisotropic water invasion which bottom water ascends along faults vertically. Combined with production performance data, water invasion of gas reservoir is divided into 3 patterns: bottom water ascends along faults vertically and then invades horizontally, edge water invades horizontally, and nearly homogeneous bottom water invades from deeper layers. It is predicted and warned for the water produced from gas wells, as well as it provides the basis for preventing and governing the water invasion in Kela 2 Gas Field.

Key words: Tarim Basin, Kela 2 Gas Field, water invasion influencing factors, water invasion patterns, gas field development.