In order to solve the problems in Wellblock-SN-1 in Junggar Basin such as high water cut in oil wells

poor water injection effect in some wells

and decline in permeability of oil and water wells after water injection with wastewater and other issues

the influencing factors of water flooding recovery of reservoir have been studied. By the water injection optimization numerical simulations and experiments such as damage by the injection water to core

core flooding and injection water quality indicator analysis

the formation damage by injection water have been studied from microscopic scale

core scale and macroscopic scale respectively

and the damage mechanism leading to the decrease of permeability in production and injection wells has been revealed. It is recognized that the formation damage caused by solid blockage in injection water is the main controlling factor leading to low oil recovery. It is found that the solid blockage not only affects the microscopic flooding effect

but also increases the mobility ratio and reduces the sweep efficiency. Therefore

the water quality of the re-injection of the reservoir in Wellblock-SN-1 is the main factor for the poor water injection efficiency. The suspended solid mass concentration should be treated as the primary water quality control index. The proposed multi-scale evaluation method improves the reliability of the results

and is helpful for improving the exploitation effect of oilfield water flooding. It can provide technical reserves for stable oilfield exploitation.