Capillary desaturation curve: does low salinity surfactant flooding significantly reduce the residual oil saturation?

Davood Zivar,Peyman Pourafshary,Nikoo Moradpour

doi:10.1007/s13202-020-01074-1

Davood Zivar, Peyman Pourafshary + Show 1 more

Open Access

https://doi.org/10.1007/s13202-020-01074-1

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Abstract

Different oil displacement experiments conducted on sandstone and carbonate samples show that low salinity water (LSW) injection can reduce the residual oil saturation (ROS). Recently, surfactant flooding (SF) in combination with low salinity water (known as low salinity surfactant (LSS) flooding) is proposed as a potentially promising hybrid enhanced oil recovery (EOR) process. A lower ROS is reported for a LSS process compared to that seen in SF or with LSW at the same capillary number. The capillary desaturation curve (CDC) is a well-known tool to study the effect of viscous and capillary forces on ROS for different EOR techniques. In this study, ROS data of various LSW, SF, and LSS flooding experiments at different capillary numbers are collected to develop a CDC to analyze the performance of the hybrid LSS method. This can help to analyze the effect of the hybrid method on an extra improvement in sweep efficiency and reduction in residual oil. A lower ROS is observed for LSS compared to LSW and SF in the same capillary number range. Our study shows different behaviors of the hybrid method at different ranges of capillary numbers. Three regions are identified based on the capillary number values. The difference in ROS is not significant in the first region (capillary number in the range of 10−7–10−5), which is not applicable in the presence of surfactant due to the low interfacial tension value. A significant reduction in ROS is observed in the second region (capillary number in the range of 10−5–10−2) for LSS compared to SF. This region is the most practical range for SF and LSS flooding. Hence, the application of LSS provides a noticeable benefit compared to normal EOR techniques. In the third region (capillary numbers greater than 10−2), where the surfactant flooding is a better performer, the difference in ROS is negligible.

Highlights

It is perceived that primary and secondary recovery mechanisms of oil recovery are incapable of fully draining the reservoir on account of domineering capillary forces or the deficient sweep efficiency of the injection fluid
The performance of the hybrid low salinity surfactant method is compared with low salinity water and surfactant flooding
A dataset consisting of residual oil saturation and capillary number values is established using data presented by scholars.The capillary desaturation curve was used to study the effective mechanisms on residual oil saturation at different capillary numbers for the mentioned enhanced oil recovery (EOR) techniques

Summary

Introduction

It is perceived that primary and secondary recovery mechanisms of oil recovery are incapable of fully draining the reservoir on account of domineering capillary forces or the deficient sweep efficiency of the injection fluid. A new line of research on active mechanisms during low salinity water (LSW) has flourished, considering fine migration (Fouladi et al 2019; Tang and Morrow 1999), pH variation (Austad et al 2010; McGuire et al 2005; Morrow and Buckley 2011), multicomponent ion exchange (AlAbri et al 2019; Lager et al 2008; Moradpour et al 2020; Shabani and Zivar 2020), double-layer expansion (Mahani et al 2015; Lee, et al 2011), and water micro-dispersion (Darvish Sarvestani et al 2019; Mahzari and Sohrabi 2015) as the most efficient mechanisms These studies have been extensively performed at various scales such as molecular scale (Khosravi et al 2020), pore level scale (Akai et al 2020; Mirchi 2018), laboratory (Lager et al 2008; Darvish Sarvestani et al 2019), and field (Vledder et al 2010) scales

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