ZHAO Xiutai;BAI Yingrui;WANG Zengbao;GAO Yuan;SHANG Xiaosen
The recovery efficiency of oil could be enhanced by using compound cross-linking polyacrylamide system of deep profile control and flooding. The formula contained main agents of a cross-linking polyacrylamide system which consisted of 0.30% HPAM, 0.08% organic chromium, and 0.10% hexamethylenetetramine is optimized by orthogonal test under the 70℃ condition. In order to prolong the gel time of system, the effects of delayed cross-linker SO on gel time and gel strength are researched. Gel time of system is 48h and gel strength is 0.057MPa when the concentration of SO is 0.04%. The performance of system could be affected by salinity, temperature, pH value, and other factors. When the concentration of Na+ is under 36,000 mg/L, the concentration of Ca2+ is below 1,000mg/L, the gel strength of system could be higher than 0.040MPa. When pH is between five and seven, the gel strength of system could be above 0.065MPa; however, the gel time is shorter. When temperature is between 60℃ and 90℃, the gel strength of system is about 0.056MPa and changes slightly, however when temperature is between 50℃ and 60℃, the gel strength of system changes greatly. The deep profile control and flooding performance of system is researched by using single tube core displacement experiment. The results show that the oil recovery could be enhanced about 20% after water flooding and the plugging rate is higher than 90% by using that system. Because the gel time of system is above 48h, therefore the performances of that cross-linking polyacrylamide system could satisfy the requirements for deep profile control and flooding in oil layers.
