In YanlO reservoir of North-Ⅲ block

Maling oilfield

the clay minerals are dominated by illite

mixed illite/smectite

kaolinite and chlorite. The potential damages to the reservoir are water and velocity sensitivities caused by illite

mixed illite/smectite and kaolinite. Based on reservoir damage study by using real sandstone model in the study area

the following understandings are achieved. (1) The velocity sensitivity of reservoir is weak in the study area

and the critical velocity is in positive correlation to permeability. The reservoir damage caused by velocity sensitivity is actually stronger than the experimental results

as the salinity of injection water is lower than that of the formation water used in the experiment. (2) The reservoir in the study area is characterized by weak-to-moderate water sensitivity

and the existence of K

+

and the increase of injection water salinity may alleviate reservoir damage from water sensitivity. The injection water salinity would be appropriate in the range from 5 to 10 g/L. (3) The oil displacement efficiency with water sensitivity damage is 11.35% lower than that without water sensitivity damage

and the overall displacement efficiency also remarkably lowers

resulting in a lower recovery ratio.