Evaluation And Scheme Optimization Of Water Quality Of Oilfield Injection

Although many new technologies, processes, materials, methods are used in oilfield development in recent years, water injection is still an important way in secondary oil recovery to maintain formation pressure and enhance oil recovery. Water quality is the key to ensure the quantity and quality of injection water. Thus the study of injection water quality is imperative. Higher water quality requirements mean additional water treatment costs but lower stimulation costs. Lower water quality requirements mean lower water treatment costs but higher stimulation costs. Therefore, the optimization of injection water’s quality specification schemes is undoubtedly of considerable realistic significance.Injecting water leads to reservoir damage inevitably. Factors and mechanism for injectivity decline are complex. Therefore, it’s a complicated synthesize research of water quality evaluation and optimization. A series of water quality evaluation experiments have been made for GX oilfield, the indexes were optimized and then two compatible water quality specification schemes were recommended for Dongying Formation and Shahejie Formation. On the basis of foreign research of injectivity, combining the reservoir characteristics and historical injection datas, parameter regression of impedance model have been completed together with a series of relations between filtration coefficient, formation damage coefficient, cake permeability and Jamin coefficient. The inpedance model for Dongying Formation and Shahejie Formation of GX oilfield have been established and it proved to be reliable. Comparing nine sets of options for water quality predicted by the impedance model, the varying pattern of injectivity was obtained and the corresponding stimulating period of injection well was treated. In current paper, on the basis of Present Value Cost, an economic evaluation model of water injection optimization was established, and nine sets of options total present value of the cost for water purification and injection increase were treated. The best option for economic benefit of water quality was recommended.