Abstract
Low salinity water flooding (LSWF) is a promising technique for improving oil recovery in sandstone reservoirs. This paper is proposed to analyze the effects of water salinity and injection rate on the oil recovery of LSWF, and to measure the wettability alteration of sandstone surface. This study performed 9 groups of core flooding experiments by injecting different salinity water, and recorded the oil recovery for each group. Furthermore, the formation water (FW) and the preferred low salinity water (FW-100) were injected under 6 different injection rates ranging from 0.10 mL/min to 0.75 mL/min, results of which were compared to analyze the influence of injection rate. The oil recovery raised at first and then decreased due to the increase of water salinity and injection rate. The preferred water salinity was about 2384.6 mg/L for the sandstone core sample. On the other hand, when the water injection rate was less than 0.30 mL/min, the oil recovery of FW-100 flooding was greater than that of FW flooding. However, once the water injection rate was higher than 0.40 mL/min, an opposite experimental result was obtained. The contact angle between core slice and oil droplet increased 5.26° after aging 50 h by 50 times dilute formation water. The incremental oil recovery by LSWF in sandstone could be best explained as wettability alteration which is related to clay minerals, oil composition and divalent cations concentration. This paper innovatively analyzed the preferred water salinity and injection rate of LSWF in sandstone, which is helpful for further application in oilfield.KeywordsLow salinity water floodingImproved oil recoveryWater injection rate
Published Version
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