The low salinity effect at high temperatures

• Published in: Fuel (Guildford) Vol. 200; no. C; pp. 419 - 426
• Main Authors: Xie, Quan, Brady, Patrick V., Pooryousefy, Ehsan, Zhou, Daiyu, Liu, Yongbing, Saeedi, Ali
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.07.2017; Elsevier BV; Elsevier
• Subjects: 02 PETROLEUM; Complexation; Contact angle; Contact pressure; Dilution; Disjoining pressure; Enhanced Oil Recovery; Flood predictions; Flooding; High pressure; High temperature; Interfaces; Kaolinite; Low salinity water; Mathematical models; Oil; Pressure; Pressure effects; Reservoirs; Saline water; Salinity; Salinity effects; Sandstone; Surface complexation model; Temperature effects; Water chemistry; Water flooding; Water temperature; Wettability; Zeta potential; Surface complexation model; Enhanced Oil Recovery; High temperature; Low salinity water; Disjoining pressure
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2017.03.088

The mechanism(s) of low salinity water flooding (LSWF) must be better understood at high temperatures and pressures if the method is to be applied in high T/P kaolinite-bearing sandstone reservoirs. We measured contact angles between a sandstone and an oil (acid number, AN=3.98mgKOH/g, base number, BN=1.3mgKOH/g) from a reservoir in the Tarim Field in western China in the presence of various water chemistries. We examined the effect of aqueous ionic solutions (formation brine, 100X diluted formation brine, and softened water), temperature (60, 100 and 140°C) and pressure (20, 30, 40, and 50MPa) on the contact angle. We also measured the zeta potential of the oil/water and water/rock interfaces to calculate oil/brine/rock disjoining pressures. A surface complexation model was developed to interpret contact angle measurements and compared with DLVO theory predictions. Contact angles were greatest in formation water, followed by the softened water, and low salinity water at the same pressure and temperature. Contact angles increased slightly with temperature, whereas pressure had little effect. DLVO and surface complexation modelling predicted similar wettability trends and allow reasonably accurate interpretation of core-flood results. Water chemistry has a much larger impact on LSWF than reservoir temperature and pressure. Low salinity water flooding should work in high temperature and high pressure kaolinite-bearing sandstone reservoirs.