An investigation into the roles of chlorides and sulphate salts on the performance of low-salinity injection in sandstone reservoirs: experimental approach

Abstract

Numerous studies have been carried out to ascertain the mechanisms of low-salinity and smart water flooding technique for improved oil recovery. Focus was often on brine composition and, specifically, the cationic content in sandstone reservoirs. Given the importance of the salt composition and concentration, tweaking the active ions which are responsible for the fluids-rock equilibrium will bring into effect numerous mechanisms of displacement which have been extensively debated. This experimental study, however, was carried out to evaluate the extent of the roles of chloride-and sulphate-based brines in improved oil recovery. To carry this out, 70,000 ppm sulphates-and chloride-based brines were prepared to simulate formation water and 5000 ppm brines of the same species as low-salinity displacement fluids. Core flooding process was used to simulate the displacement of oil by using four (4) native sandstones core samples, obtained from Burgan oil field in Kuwait, at operating conditions of 1500 psig and 50 °C. The core samples were injected with 70,000 ppm chloride and sulphates and subsequently flooded with the 5000 ppm counterparts in a forced imbibition process. Separate evaluations of chloride-and sulphate-based brines were carried out to investigate the displacement efficiencies of each brine species. The results showed that in both high-and low-salinity displacement tests, the SO 4 brine presented better recovery of up to 89% of the initial oil saturation (Soi). Several mechanisms of displacement were observed to be responsible for improved recovery during SO 4 brine displacement. IFT measurement experiments also confirmed that there was reduction in IFT at test conditions between SO 4 brine and oil and visual inspection of the effluent showed a degree emulsification of oil and brines. Changes in pH were observed in the low-salinity flooding, and negligible changes were noticed in the high-salinity floods. These results provide an insight into the roles of chloride and sulphate ions in the design of smart "designer" water and low-salinity injection scenarios.

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

“…Calcium ions (Ca 2+ ) have a higher affinity for the quartz surface compared to sodium ions (Na + ), which results in a stronger electrostatic attraction. This attraction between the calcium ions and the quartz surface enhances the detachment of oil molecules from the surface, leading to oil displacement. − Additionally, the presence of calcium ions can modify the interfacial tension between the oil and brine, facilitating the movement of oil through the system. When the SDS surfactant is introduced into the calcium chloride system (CaCl 2 –SDS), the surfactant molecules interact with both the oil and brine phases, further influencing oil displacement.…”

Mechanistic analysis of matrix-acid treatment of carbonate formations: An experimental core flooding study

“…After preparing the core samples in terms of specific length and diameter, they are washed with organic solvents in order to remove organic and/or inorganic substances from their porous spaces to calculate the actual volume of the core samples [ 39 ]. The core samples are soaked in hot petroleum solvent (toluene) to wash the core samples and expel the hydrocarbons and possible water or drilling fluid from the inside of them [ 58 , 59 ]. After the hydrocarbon and water are dissolved in the solvent, the core samples are washed by the Soxhlet Extractor assembly.…”

Data-Driven Connectionist Models for Performance Prediction of Low Salinity Waterflooding in Sandstone Reservoirs

“…Thus, producing part of the oil left in the reservoirs is of paramount importance. Several EOR strategies from sandstone reservoirs have been proposed and implemented in both experimental and field trials. − Among these approaches, waterflooding and subsequently low salinity waterflooding (LSWF) remain an attractive option. , This method first gained recognition in the 1990s by research works conducted by Morrow and co-workers. ,− Several researchers have attempted to delineate mechanisms behind the low salinity effect (LSE) by exploring the impact of each parameter on the results. − The mechanisms of the LSE, which are categorized as brine/rock, oil/brine, and oil/brine/rock groups, can be listed as follows: wettability alteration, multicomponent ion exchange, fines migration, local pH increase, double layer expansions (DLE), , osmotic effect, microdispersion formation, and viscoelastic effect . By reviewing the literature, one can conclude that each of these mechanisms is directly or indirectly dictated by several effective parameters relevant to the oil, brine, and rock composition .…”