In the oil production process, due to the formation of heterogeneity, often produce flooding problems, the need for water shutoff, and its essence is to change the water flow in the formation of the state in order to reduce oil field produced water, keeping the formation energy, enhanced oil ultimate recovery purposes. Polyacrylamide flocculant chemistry class selective blocking agent of the oil and water infiltration capacity, reduced permeability to oil up more than 10%, while reducing water permeability can be over 90%. Selective water shutoff feature that is not available to other blocking agent, usually by selecting the appropriate type of formation relative molecular weight polyacrylamide. Good homogeneity, high average permeability of the reservoir, the choice of the relative molecular mass (. (500 ~ .700) × 10) polyacrylamide flocculant; bedrock fractured low permeability reservoir permeability changes or large the reservoir, the choice of high molecular weight (1000 × 10. above) polyacrylamide. When using polyacrylamide crosslinking may use, but can generate aluminum, chromium salt, zirconium salt and the like crosslinked gels, certain resins may be added to form a compatibilizer polymer network, so that it has a higher temperature resistance. This method has been applied shutoff water reservoir high water cut oilfield in the country at the end of carbonate, achieved remarkable results. Polyacrylamide can be adjusted within the formation water injection profile and large pore blocking, the practice has achieved good results.
   Our oil fields using polyacrylamide flocculant have done a lot of test areas. Oilfield with an average relative molecular mass (300 ~ 350) × 10 ', the degree of hydrolysis of 10% to 15% polyacrylamide, get good results in the oil shutoff. Hydrolysis degree of 30%, relative molecular mass of 400 × 10. Polyacrylamide flocculant in the geological drilling, played the hole wall to maintain stability and to prevent leakage of the drilling action. Hydrolysis degree of 30% polyacrylamide flocculant as drilling fluid, reduce the rate of penetration of the drilling fluid, the drilling larvae L improve speed, shorten the stirring time drilling fluid, thus reducing the number of units and the drilling fluid was stirred, to improve clay mud rate of 30% to 50%,. Sometimes, required for use in water shutoff partially crosslinked polyacrylamide. In order to improve the selectivity of water shut out of the oil, the degree of crosslinking to try to lower. Molecular weight polyacrylamide flocculant usually (300-500) × 10. And the relative molecular mass of choice to the permeability pore structure as the basis. 1D permeability greater than blocking layer, the polymer molecular mass to 300 × 10. Or so. At higher permeability, bite by (500 ~ 800) × 10. Polyacrylamide. The degree of hydrolysis and also about the nature of the blocking layer of rock, limestone adsorption ability, the degree of hydrolysis should be higher, about 20% to 30% lower sandstone adsorption capacity, degree of hydrolysis of 5% to 20%.