Abstract: A new plug agent which is made mainly from humic acid,formaldehyde,strength agent and 0.02% HPAM solution is studied.The influences of concentration of humic acid,cross linking agent,temperature,pH value and salinity on the property of the agent are studied,too.Orthogonal test is conducted to optimize the formulation and evaluation.The result indicates that its initial velocity is 10mPa·s,which can easily reach deep formation.The gelation time is 18h and gelation strength 0.087MPa.The excellent application range of pH value is 7~9.The properties include temperatureresistance and antisalt,long term stability,good plugging ability and low cost,it is very suitable for high temperature and low permeable reservoirs.

Key words: humic acid, plug agent, low permeable reservoir, hightemperature, optimal formulation