Research And Application Of Water Quality Optimization Technology For Sandstone Reservoir

Water injection is an important treatment which can make oil well reach high and stabled production in a long period. It is also a secondary recovery method to enhance oil recovery. However, problem do exists in water injection. In high water cut stage, because of the constant increasing injection rate, the proportion of water disposal charge in the whole operating cost is increasing. The contradiction of cost price and benefit is apparent. Especially in some low permeability oilfields, even if much finance had been invested, many of them still cannot reach the departmental standard. Those oilfields had to pull down the injection water quality to reduce the cost.The aim of injected water quality optimization is to control the injection cost and make the economic benefit maximize. In order to achieve this target, we first researched the relationship between the injected water quality criteria and the regularity of injectivity changed. Then make use of the economic evaluation method to compare the injection cost under different water quality criteria. Finally we can get the most profitable injected water disposal program.In this paper, the damage mechanism of reservoir during water injection and component of injected water quality criteria was summarized based on a comprehensive study of literature home and abroad. Then according the quantification of water quality criteria we proposed a method of classifying the water quality criteria. Several common used injectivity prediction modles were introduced, and then we derived the impedance prediction modle and acquired the resolution of it. With this modle we predicted the injection pressue of Sha nian oilfield, and the result showed a preferable match of the real condition. This modle is proved to be dependable. We conducted water quality compatibility laboratory experiment and got the high limit of water quality criteria of Sha nian oilfield. Based on the pore throat structure and the capacity of water disposal apparatus of Sha nian oilfield and the high limit of water quality criteria, using the water quality criteria classification method we designed six water disposal programs. According to the survey of water disposal technological process, capital cost, installation cost and simulation cost etc. of Sha nian oilfield, with the use of economic evaluation the injection cost was compared under different water disposal program and the most profitable injected water disposal program was proposed.