Application of ion-engineered Persian Gulf seawater in EOR: effects of different ions on interfacial tension, contact angle, zeta potential, and oil recovery

Amir Hossein Saeedi Dehaghani,Seyed Masoud Ghalamizade Elyaderani

doi:10.1007/s12182-020-00541-y

Amir Hossein Saeedi Dehaghani, Seyed Masoud Ghalamizade Elyaderani

Open Access

https://doi.org/10.1007/s12182-020-00541-y

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Journal: Petroleum Science	Publication Date: Jan 17, 2021
Citations: 9	License type: open-access

Affiliation: Tarbiat Modares University

Abstract

In this study, we initially performed interfacial tension (IFT) tests to investigate the potential of using the Persian Gulf seawater (PGSW) as smart water with different concentrations of NaCl, KCl, MgCl2, CaCl2, and Na2SO4. Next, for each salt, at the concentration where IFT was minimum, we conducted contact angle, zeta potential, and micromodel flooding tests. The results showed that IFT is minimized if NaCl or KCl is removed from PGSW; thus, for solutions lacking NaCl and KCl, the IFT values were obtained at 26.29 and 26.56 mN/m, respectively. Conversely, in the case of divalent ions, minimum IFT occurred when the concentration of MgCl2, CaCl2, and Na2SO4 in PGSW increased. Specifically, a threefold rise in the concentration of Na2SO4 further reduced IFT as compared to optimal concentrations of MgCl2 or CaCl2. It should be mentioned that eliminating NaCl from PGSW resulted in the lowest IFT value compared to adding or removing other ions. Whereas the removal of NaCl caused the contact angle to decrease from 91.0° to 67.8° relative to PGSW and changed surface wettability to weakly water-wet, eliminating KCl did not considerably change the contact angle, such that it only led to a nine-degree reduction in this angle relative to PGSW and left wettability in the same neutral-wet condition. At optimal concentrations of MgCl2, CaCl2, and Na2SO4, only an increase in Na2SO4 concentration in PGSW could change wettability from neutral-wet to weakly water-wet. For solutions with optimal concentrations, the removal of NaCl or KCl caused the rock surface to have slightly higher negative charges, and increasing the concentration of divalent ions led to a small reduction in the negative charge of the surface. The results of micromodel flooding indicated that NaCl-free PGSW could raise oil recovery by 10.12% relative to PGSW. Furthermore, when the Na2SO4 concentration in PGSW was tripled, the oil recovery increased by 7.34% compared to PGSW. Accordingly, depending on the conditions, it is possible to use PGSW so as to enhance the efficiency of oil recovery by removing NaCl or by increasing the concentration of Na2SO4 three times.

Highlights

Evidence has demonstrated that about 65%–70% of the oil in reservoirs is trapped when conventional oil recovery methods are used
Smart water can change the wettability of the rock surface from hydrophobic to hydrophilic and reduce interfacial tension (IFT), allowing trapped oil to move (Al-sofi and Yousef 2013; Awolayo et al 2016; Honarvar et al 2020a; Manshad et al 2017; Mohanty and Chandrasekhar 2013; Nowrouzi et al 2019; Saeedi Dehaghani and Badizad 2019; Saeedi Dehaghani et al 2020)
The results revealed that MgSO4, compared to MgCl2, increased IFT values and altered wettability from strongly water-wet to weakly water-wet, oil recovery was improved by the occurrence of the snap-off phenomenon

Summary

Introduction

Evidence has demonstrated that about 65%–70% of the oil in reservoirs is trapped when conventional oil recovery methods are used. In other words, these methods cannot overcome the capillary force in the porous medium and bring about significant oil production, especially in carbonate reservoirs. Smart water flooding can be defined as a novel EOR technique in which the ionic composition of brine is changed by adding or removing ions to yield higher oil recovery. Smart water is obtained by adjusting and optimizing the concentration of ions in the base fluid or by adding a salt containing the ions that can change the balance of the oil/brine/rock system and improve oil recovery Smart water can change the wettability of the rock surface from hydrophobic to hydrophilic and reduce interfacial tension (IFT), allowing trapped oil to move (Al-sofi and Yousef 2013; Awolayo et al 2016; Honarvar et al 2020a; Manshad et al 2017; Mohanty and Chandrasekhar 2013; Nowrouzi et al 2019; Saeedi Dehaghani and Badizad 2019; Saeedi Dehaghani et al 2020)

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