Studies On Gel Systems With Variable Strength

In order to satisfy the demand for excellent temporary blocking performances of temporary blocking agent in the technologies of separated layer water injection and commingled water injection and the demand for excellent deep profile control agent in deep profile control technology which has been widely used in medium or high water-cut oilfield, gel systems with variable strength are proposed. This paper mainly researches gel typed temporary blocking agent and gel typed deep profile control agent with variable strength.This paper studies the components and formulations of gel typed temporary blocking agent. The formulations of gel typed temporary blocking agent are optimized by analyzing effect factors of its gelation time and gel breaking time, and then its application properties are studied. The results indicate that the temporary blocking agent has strong lithological adaptability, good injection performance, good shearing resistance and excellent blocking characteristics. In core blocking experiments, some 85% of initial permeability is restorable. The research of parallel sand-packed models indicates that the temporary blocking agent can reduce the degree of water shuoff agent entering low permeability formation, so it can remarkably reduce the damage of non-target formation. Therefore, the use of temporary blocking technology is very essential.In the research of gel typed deep profile control agent with variable strength, phenol-formaldehyde resin gel is selected as the basic formulations. The results of formulations research indicate that when the concentration of polymer or cross-linker increases, the gelation time of phenol-formaldehyde resin gel decreases and the gel strength increases. Thiourea as the oxygen scavenger cannot affect the gelation time, but it can significantly increase the gel strength. Under the temperature of 80℃, the half-life of hydrogen peroxide is too short, so it cannot adjust the gel strength for a long time. While the half-life of tert-butyl hydroperoxide is much longer, it can gradually decrease the gel strength of phenol-formaldehyde resin gel through its slow spontaneous decomposition. After three months, the gel strength declined to 55% of its crest value, so tert-butyl hydroperoxide can adjust the gel strength of gel typed deep profile control agent in the long term.