Impact of water saturation and cation concentrations on wettability alteration and oil recovery of carbonate rocks using low-salinity water

Abstract

In this study, the effect of initial water saturation on the oil recovery for carbonate rocks is investigated using spontaneous imbibition experiments. The experiments are performed using 20 times diluted sea water as imbibing fluid and the sea water as initial water. In addition, the impact of pH and Ca 2+ , Mg 2+ , Na +, and K + cations concentration change of imbibing fluid are investigated during tests. These results help to identify the active cations in the wettability alteration process of carbonate rocks during the low-salinity water injection. A mechanism is proposed to describe the effect of initial water saturation on the oil recovery by low-salinity water injection. The impact of initial water saturation on the wettability alteration might be positive or negative depending on its value and the rock permeability. The comparison of divalent cations concentrations shows that the minimum adsorption of Ca 2+ and maximum desorption of Mg 2+ lead to maximum oil recovery of spontaneous imbibition. The results confirm that three cations of Ca 2+ , Mg 2+ , and Na + are active for wettability alteration of carbonate rocks in the presence of sea water as initial water and diluted sea as imbibing fluid, whilst the amounts of potassium remain constant.

Mechanisms of smart waterflooding in carbonate oil reservoirs - A review

“…Contact angle measurements confirmed these observations: contact angle decreased with increased temperature, indicating a more water-wet surface (Karoussi and Hamouda, 2007). A positive effect of high temperature was also reported by Zaeri et al (2018aZaeri et al ( , 2018b.…”

“…It was concluded from the simulation that wettability alteration played an effective role only when IFT was high, which was more important at the early stages of the experiments. Zaeri et al (2018aZaeri et al ( , 2018b carried out Amott (imbibition) tests with the reservoir oils and the carbonate rock materials from Iranian petroleum reservoirs. It was showed that there is an optimum degree of dilution corresponding to a maximum recovery.…”

“…A double layer around a drop in the surrounding concentration gradient may be non-uniform, which creates a moving force. Zaeri et al ( 2018b) showed that recovery by imbibition of the low salinity water increases much if the rock contains initially a certain (but not-so-large) amount of the saline connate water. Increasing the initial water saturation to a certain value improves the oil recovery, but any further increase has a negative impact.…”

Smart water flooding performance in carbonate reservoirs: an experimental approach for tertiary oil recovery

“…Concentration of Mg 2+ , which can displace adsorbed carboxylic groups, is also found to be an important factor in wettability alteration (Karimi et al 2015). As a result, both positive and negative effect for the presence of divalent ions have been reported in the literature (Awolayo et al 2016;Fathi et al 2010Fathi et al , 2011Karimi et al 2015;Lashkarbolooki et al 2017;RezaeiDoust et al 2009;Zaeri et al 2018b). So, a more comprehensive study is needed to be performed to understand the impact of changing the relative amount of different divalent ions at reservoir condition.…”

Extraction, characterization and evaluation of saponin-based natural surfactant for enhanced oil recovery

“…The inorganic salt breaks the structure of the water, thereby increasing the solubility of the organic components of the oil in the aqueous phase (Ghorbanizadeh and Rostami 2017). Besides, the presence of the ions increases the adsorption of the surfactant at the oil-water interface (Zaeri et al 2019;Liu et al 2018;Strand et al 2006). Hence, the IFT of the oil-water interface reduces further.…”