Low salinity effects on oil recovery performance: underlying physical mechanisms and practical assessment

Abstract

This paper is a tentative synthesis of the main knowledge and experience gained from recent studies and application of Low Salinity Water Injection (LSWI) in carbonate and clayey silico-clastic rocks. A physical model based on ionic force is presented to explain the so-called Dual Layer Expansion (DLE) mechanism often invoked to account for the Low Salinity Effects (LSE) on rock wettability and oil recovery. The role played by the Multi Ion Exchange (MIE) mechanism is clarified, at least for clayey rocks. Eventually, the proposed physical analysis shows the complementary roles that injected brine concentration and composition can play on waterflood recovery efficiency depending on the Crude Oil Brine Rock (COBR) system under consideration. To account for the diversity of COBR systems, a straightforward modelling methodology is then proposed to simulate laboratory LSWI tests on a case-by-case basis and infer the actual evolution of residual oil saturation with brine concentration and/or composition. The simulation involves a wettability driver that may be either the global salinity or the square root of ionic force. The analysis of published results actually shows that the latter predicts low salinity effects on residual oil saturation better than the former. Hopefully, this paper contributes to the understanding of the DLE and MIE mechanisms induced by a smart water injection and provides a simple and robust methodology to simulate the reference coreflood experiments that remain necessary to assess and optimize LSWI.

Low Salinity Water–Polymer Flooding in Carbonate Oil Reservoirs: A Critical Review

“…Mineral dissolution can connect macro‐ and micropores, allowing access to regions that would otherwise not be reached and increasing oil recovery. [ 29 ]…”

“…[28] Mineral dissolution can connect macro-and micropores, allowing access to regions that would otherwise not be reached and increasing oil recovery. [29] Mineral dissolution is not considered the main mechanism that alone results in increased oil recovery through LSW injection. [ 21,28,30] Disagreements are mentioned regarding this mechanism, mainly because recovery improvements were not observed in tests with the injection of brines that could promote mineral dissolution.…”

Enhancing surfactant desorption through low salinity water post-flush during Enhanced Oil Recovery

“…Na ion tends to adsorb to the pore surface as a substitute to the SDBS monomer. As addressed by literature [34,35] where Na of LSW induces multi-component ion exchange. The exchange follows a bi-procedure illustrated in Figure 5.…”

Optimization of ionic concentrations in engineered water injection in carbonate reservoir through ANN and FGA

“…This test obtained quite significant results in this coupling to the flow simulator. Another aspect of the existing models for LSW/EWI simulation is a simplistic assumption whose change in wettability implies only in the modification of two-phase flow parameters (Bourbiaux, 2020).…”