Abstract: Water injection is an effective measure to maintain the reservoir energy and to enhance the oil recovery. It is very important, to the expected development effectiveness of Water injection reservoirs, especially to those with medium-low permeability sandstone reservoirs to ensure water injection normally.
The study results show that the injected water quality regulation, operation and management are the main factors to affect the development effectiveness. Aimed at the development effectiveness and lowering water injection cost, a noval concept of water quality optimization is proposed in this paper, which takes comprehensive considerations of water quality compatibili-
ty, water treatment, water injectivity, stimulation, planned volume of injected water and integration cost of water injection.This technique has a wide guideable significance and its application will result in good economic benefit and perspective future.

Key words: water quality, optimization, stimulation Treatment, economic evaluation, water Injection