Development and evaluation of organic/inorganic combined gel for conformance control in high temperature and high salinity reservoirs

Polymer gels have been successfully applied to control undesired water production for many years, however, due to poor long-term thermal stability and salt tolerance, conventional polymer gels present some limitations for application in high temperature and high salinity reservoirs. In this paper, an organic/inorganic combined gel composed of polymer with low degree of hydrolysis, phenol formaldehyde resin and inorganic silicate was proposed and developed. The effects of concentration, temperature on gelation time were studied. Long-term thermal stability, salt tolerance and permeability reduction ability were investigated. Results showed that based on proper gelation time and economical cost, the formulation of the organic/inorganic combined gel was optimized. The gelation time decreased from 54.0 to 15.5 h with increasing temperature from 100 to 130 degrees C. After aging for 60 days in simulated formation brine with high total dissolved solids (TDS: 20 % NaCl + 2.5 % CaCl2) at 130 degrees C, compared with polymer gel, the organic/inorganic combined gel had better long-term thermal stability and salt tolerance. Sandpack flow experimental results showed that for the organic/inorganic combined gel composed of 0.3 wt% polymer, 4.0 wt% resin and 3.0 wt% inorganic silicate, after aging for 60 days at 130 degrees C, the combined gel showed approximately 85 % permeability reduction. Therefore, these results indicate that the combined gel studied here can be a good candidate for controlling water production in high temperature and high salinity reservoirs.