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

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.

Experimental Research on the Millimeter-Scale Distribution of Oil in Heterogeneous Reservoirs

“…The flow laws of the different fluids were analyzed. Parmigiani et al [25][26][27][28][29] investigated the relationship between relative permeability, capillary pressure, and oil saturation. Ma et al [30], and Wang et al [31] investigated the changes in oil saturation due to reservoir pore size and the hydrodynamic radius of the chemical constituents in the injected fluid using fluid flow simulation experiments.…”

Optimization of Low Salinity Water/Surfactant Flooding Design for Oil-Wet Carbonate Reservoirs by Introducing a Negative Salinity Gradient

“…The surfactant solution prepared in EW was then injected in continuous mode and it recovered 11.04% of OOIP. This additional oil was recovered due to the reduction of oil-water IFT by surfactant [37,71] and the microemulsion phase behavior generated under a constant optimum salinity profile was of the Type III-III. Such microemulsion profile is not the desired profile as it results in a lower reduction of S or .…”

“…Hybrid EOR methods are targeted to recover more residual oil in an economic, ecological, and technically feasible way by stimulation of multiple mechanisms simultaneously. LSWF promotes a suitable environment for effective surfactant flooding due to the detachment of oil molecules, wettability alteration, and reduction in IFT [36][37][38]. Moreover, the combination of LSWF with surfactant flooding leads to the minimization of surfactant consumption and improves its solubility and stability, which in turn reduces the project cost.…”

Experimental and Molecular Dynamics Simulation to Investigate Oil Adsorption and Detachment from Sandstone/Quartz Surface by Low-Salinity Surfactant Brines

“…This approach has become one of the most extensively studied areas, aiming to uncover the underlying mechanisms and determine the optimal brine composition. , The effectiveness of low-salinity water flooding is highly contingent on the characteristics of the crude oil–brine-rock (COBR) system. − Indeed, low-salinity water flooding stands out as an economical method for enhanced oil recovery (EOR), notable for its avoidance of toxic and costly materials. In recent times, there has been an increased emphasis on low-salinity water research and its synergy with other fluids such as surfactants, polymers, and so forth. − The primary goal is to minimize brine–oil interfacial tension, enhancing the efficacy of the recovery process. This approach has demonstrated superior outcomes when contrasted with high brine concentrations, supported by robust field data and academic research. ,− These studies have prominently focused on documenting wettability alteration in oil reservoirs, acknowledging its crucial role in attaining successful oil recovery.…”