**6. LSW/hot water hybrid EOR technique**

Heavy oil is conventionally recovered by thermal-based approaches. Thermal energy in combination with LSW water flooding, in the form of hot LSW water flooding, can be applied to simultaneously decrease the viscosity of the heavy oil and alter the wettability of the porous media to attain higher oil recovery. Alotaibi et al. and Tang et al. reported lower contact angle and higher oil recovery, respectively, after increasing the displacement temperature in LSW injection [62, 63]. Contrary to this observation, Soraya et al. [64] found lower oil recovery at higher temperatures by tertiary LSW. However, another study [65] demonstrated that the injection of hot LSW yielded significant incremental oil recovery. In this work, hot LSW at a concentration of 200 ppm salinity was injected after hot HSW at a concentration of 15,000 ppm salinity, which yielded about 25% OOIP incremental oil recovery, as shown in **Figure 21**. In addition, in this study the injection of steam is proposed after hot LSW flooding to further enhance the oil recovery.

A similar trend was reported by Ding et al. by injecting nanoparticle-assisted low-salinity hot water (LSHW) into silica sand packs to recover heavy oil. Temperatures of 17, 45, and 70°C were applied under different scenarios of high- and low-salinity brines and nanofluids. LSW was found to provide better

**Figure 21.** *Oil recovery by hot HSW and hot LSW [65].*

*Hybrid EOR Methods Utilizing Low-Salinity Water DOI: http://dx.doi.org/10.5772/intechopen.88056*

performance than the HSW under ambient temperature. Moreover, in all cases in the presence or absence of nanoparticles, increasing the displacement temperature yielded higher ultimate oil recoveries up to 23%. Increased temperature also restrains the growth rate of water cut [65].

The results to date in terms of enhanced oil recovery for all hybrid LSW-based EOR methods are promising. So far, experiments at laboratory scale have been carried out, while modeling studies and pilot field applications are scarce. Numerical simulation studies are necessary to provide more practical insights on the effectiveness of hybrid methods especially important for field implementations.
