The Damage to Reservoir Caused by the Injection Water in K1S2 of Tuha Oilfield

Based on the problem happened during the water-flooding development of K1S2 reservoir in Tuha oilfield, the article has analysed the poroperm characteristics, petrologic feature, grain-size characteristics and clay composition. The article has also evaluated the velocity sensitivity to the reservoir on the basis of comparison between formation and injection water. The results show the reservoir is poor in shale and montmorillonite, but the injection of illite and kaolinite the pore throat is thin. Water differs from each other and the mineralization of the injection water is lower than the formation one. It will produce scale deposit after mixing them partly. The water-flooding development leads to serious particle migration and decreases the permeability seriously. The velocity sensitivity index is 36% existing medium velocity sensitivity. Under the displacement velocity of 0.2mL/min, the permeability of formation water is 24.41×10-3µm2,after injecting the water for 24h, the permeability is 18.91×10-3µm2,reduce the permeability by 22.5%,causing the light damage.