Studies On The Gelation Reaction Mechanism Of Phenolics With Polyacrylamide And Its Used As Water Shutoff Agent In High Temperature & High Salinity Reservoir

Chemical water plugging is well recommended in this paper; polyacryla- mide used as water shutoff agent is discussed in detail. The nature of CPAM, the mechanism of the cross linking reaction of cationic polyacrylamide with phenolics and water shutoff agent used cationic polyacrylamide in high temperature and high salinity reservoirs are researched particularly. The results show that: CPAM has good temperature tolerance. It is the dissolution oxygen that was the main factor of polyacrylamide does not steady in high temperature. The hydrolysis reaction of amide group aggravates the instability of polyacrylamide in high temperature and high salinity environment, but the cationic group in polyacrylamide can strengthen its stability. Cationic polyacrylamide is steady in acidic environment, but it generates flocculent deposition when pH is more than ten. It is good for gelation in neutral and alkalescent environment. The mechanism of the cross linking reaction of phenolics with cationic polyacrylamide was investigated with infrared spectrometer and viscosimetry contrast experiment. The results show the essence of the gelation reaction of phenolics with cationic polyacrylamide is that the hydroxymethyl (—CH2OH) and amide group (—CONH2) form a—CH2—NH—CO—group and generate a water (H2O). The combination bond is covalence bond, which is different with co-ordination bond when anionic polyacrylamide crosslink with metallic ion. It is more strength and stability. Carboxyl group do not react with phenolics.The experience talks that: High salinity leads to short gelling time and high strength gel. Compound cross linking agent can improve gel's salt tolerance in high temperature. At 85℃, the preferable concentration of the gel system is that: 0.5% HJ-2 + 0.3%phenolics + 0.07%LN-135. The optimum pH for cross linking reaction is 7 to 10. The gel is stable in high salinity with the content of NaCl: 2.5×105mg/L and CaCl2: 10000mg/L. At 135℃, the preferable concentration of the gel system is that: 0.5%HJ-2 + 0.15%Compound cross linking agent + 0.15%LN-135 + 0.5%inhibitor + 0.05%oxygen scavenger. The optimum pH for cross linking reaction is 6.5 to 9. The gel is stable in high salinity with the content of NaCl: 2.2×105mg/L and CaCl2: 1000mg/L. At 110℃, with the pressure of 70MPa, 60 minutes for temperature rising time, the gel system's crosslinking time is more than 8 hours in cement thicken instrument.