Pore-Scale Investigation and Performance Evaluation of SMART LowSal Flooding for Enhanced Oil Recovery from Matured Reservoirs Using a Lab-on-a-Chip

Abstract

Oil recovery from a matured oilfield is challenging due to the low recovery factor. These challenges became opportunities for existing low-salinity water (LSW)-based enhanced oil recovery (EOR) methods. The performance of the LSW in recovering the residual oil from a matured oilfield is improved with the help of additives, viz., surfactant, water-soluble polymer, and silica nanoparticles (NPs). In the present study, series of experiments have been carried out to understand the pore-scale oil displacement phenomena of the novel nanofluids (SMART LowSal) using a microfluidic chip (lab-on-a-chip) integrated with an inverted microscope. The microfluidic chip is saturated with oil and is flooded with different nanofluids (NFs) to recover oil. The efficacy of oil displacement is evaluated using two unique methods (series and parallel). The oil displacement efficacy from the chip matrix, the interaction between rock−oil−nanofluid, and wettability alteration of the rock representative surface have been visually investigated. The oil displacement results are compared with the oil recovery results from the sand-pack reactor and Amott cell. Oil displacement was found to increase with increasing concentration of nanoparticles in NFs and slightly decreases beyond 1000 ppm of NPs. Visual observation clarified the complex interaction of rock− oil−nanofluid systems. A significant reduction in the interfacial tension of the fluid−fluid phase in the presence of surfactant leads to elongation of the oil globules and higher oil recovery. A thin layer of a film of water is noticed between the grain and the fluid phase, which could be the reason for the wettability alteration and improved oil recovery. The lab-on-a-chip method adopted for evaluating the efficacy of oil recovery due to the various nanofluids could help better understand the displacement phenomena and screening of additives for the best formulation of injection fluid for EOR application.

Microfluidic Investigation of Surfactant-Assisted Functional Silica Nanofluids in Low-Salinity Seawater for Enhanced Oil Recovery Using Reservoir-on-a-Chip

“…As mentioned above, the flow conditions employed in our study lie within the transition zone between viscosity and capillary force dominated region according to the log ( M ) – log (Ca) plot. Similar flow conditions were used by other researchers. , In typical reservoir conditions, the capillary number (Ca) varied from 10 –8 to 10 –2 . Therefore, the given experimental conditions give a realistic capillary number and hence flow rate for an EOR operation.…”

“…The total, or cumulative, oil displacement achieved after NF0 flooding was 81.78% (see Table ). The addition of NF0 nanofluid (without nanoparticles) leads to a significant decrease in the interfacial tension between crude oil–water phases (thinning of the interfacial film), resulting in the elongation of oil globules and an improvement in oil recovery …”

“…Therefore, the given experimental conditions give a realistic capillary number and hence flow rate for an EOR operation. The flow rate (0.026 mL/min) was selected by observing the displacement capabilities of the injected fluid at lower flow rates, and similar flow rates have been reported in the literature. , Additionally, the Peclet number is another important parameter, representing the ratio of the advective transport rate to the diffusive transport rate. However, since there is no diffusion transport in the present study, the Peclet number cannot be analyzed.…”

“…The addition of NF0 nanofluid (without nanoparticles) leads to a significant decrease in the interfacial tension between crude oil−water phases (thinning of the interfacial film), resulting in the elongation of oil globules and an improvement in oil recovery. 47 Figure 9a−d shows microscopic pictures of the crude oil displacement from the oil-saturated microfluidic chip (location 18) due to flooding of SW, LSW, and NF4 injection fluids. Figure 9b shows the flooding of SW during secondary oil recovery in the oil-saturated microfluid chip.…”

“…Similar flow conditions were used by other researchers. 47,52 In typical reservoir conditions, the capillary number (Ca) varied from 10 −8 to 10 −2 . 53 Therefore, the given experimental conditions give a realistic capillary number and hence flow rate for an EOR operation.…”