Evaluation of reservoir damage of Well Yingnan-2 and its protection measures

The output of Yingnan-2 well declines obviously after drilling,as well as the reservoir is seriously damaged.Therefore,it is necessary to evaluate reservoir damage and conduct research on protection measures.The analysis results of lithology,physical properties,pore feature,and clay components of reservoirs show that pores and throats are tiny and there is plenty of andreattite,which easily lead to serious sensitivity damage.Based on latent damage factors,the author runs water lock and different sensitive experiments.Results show that water lock,water sensitivity,pressure sensitivity are the main damage factors.A potassium base sulphonated polymer drilling fluid formulation is designed for preventing the water sensitivity damage.The static performance of the cores damaged shows that the permeability restoration of the cores is high.CO2 fracturing technique is suggested to be used,and formation pressure should be controlled appropriately.