PREPARATION OF HEAT RESISTANT AND SALTS TOLERANT HYDROPHOBICALLY ASSOCIATING POLYMER WEAK GEL AS PERMEABILITY PROFILE MODIFICATOR/OIL DISPLACING AGENT


The applicability of weak gels of two different polymers and crosslinkers is studied as permeability profile modifying/flooding agents at standard reservoir conditions of Shengli (temperature 70°C and TSD of formation water 7277 mg/L). It is shown that HPAM (hydrolyzed polyacrylamide)/AI citrate/artificial formation water (AFW) systems (M = 1.7 × 107 for HPAM) gelate very quickly and the gel viscosity is not stable and maintains for < 48 hr; hydrophobically associating polymer NAPs/Al citrate/AFW systems form gels with improved stability at rather high polymer concentration (> 1200 mg/L); NAPs/Cr3+ (from an organic acid salt)/AFW systems containing 600-800 mg/L of polymer form gels of viscosity 300-500 mPa/sec in 1-3 days which keeps stable in > 45 days (the experimental time duration limit); by introducing 50-250 mg/L of a selected organic acid as gelation retarder into system of 700 mg/L of NAPs + 500 mg/L of Cr3+ crosslinker + AFW, the gelation time of the system is delayed from 1-3 to 5-15 days and more. This delayed gelling NAPs/Cr3+ fluid can meet the requirements to permeability profile modifying/flooding fluid in field used where the amount of the fluid to be injected is large.