Using Low Salinity Waterflooding to Improve Oil Recovery in Naturally Fractured Reservoirs

Abstract

Low salinity waterflooding is an effective technique to accelerate and boost oil recovery. The impact of this technique has been investigated widely in laboratories for various scales and rock typing, most of which have demonstrated a potential improvement in oil recovery. This improvement has been attributed to several chemical and physical interactions that led to a change in the wettability to become more water-wet, as well as a reduction in the residual oil saturation. Meanwhile, it is rare to find a discussion in the literature about the efficiency of low salinity flooding in naturally fractured reservoirs. Therefore, in this work, we investigate the potential advantages of this method in fractured reservoirs using numerical simulations. A new approach to estimate the weighting factor using a tracer model has been proposed to determine the brine salinity and, hence, its properties in the mixing region. We have also used the relative permeability curves as a proxy for any physical and chemical mechanisms which are not represented explicitly in the model. The simulation outcomes highlighted the advantage of low salinity waterflooding in fractured reservoirs. An increment in oil recovery by 10.7% to 13% of Stock Tank Oil Initially In Place (STOIIP) was obtained using the dual- and single-porosity model, respectively. Therefore, the low salinity waterflooding technique represents a promising low-cost, effective method in fractured reservoirs.

Modelling the transient effect in naturally fractured reservoirs

“…13) in the simulation model can enhance the matrix characterisation, and hence increase the simulation accuracy of low salinity waterflooding (e.g. (Aljuboori et al 2020a(Aljuboori et al , 2020b) est gratitude to Universiti Teknologi PETRONAS for providing the required software license and creating the necessary working environment. The registration fee of the conference was funded by Universiti Teknologi PETRONAS, YUTP Grant (015LC0-109).…”

“…The matrix heterogeneity in NFR's is related to the depositional environment and the subsequent diagenesis processes that alter the depositional properties of the rocks (e.g. (Aljuboori et al 2020a)). Meanwhile, the pervasive occurring of fractures in most of the carbonate rocks creates additional heterogeneity to the system due to their multiscale and their various flow capacities (Agada et al 2013;Nelson 2001).…”

Experimental Study on Alternating Injection of Silica and Zirconia Nanoparticles with Low Salinity Water and Surfactant into Fractured Carbonate Reservoirs for Enhanced Oil Recovery

“…Therefore, it has been shown that LSWF is effective in fractured carbonates as well. 9,26,27 Nonetheless, LSWF causes fines migration and thus leads to formation damage, which could potentially reduce oil production. 28 Accordingly, NPs are injected with LSW because they possess the tendency to reduce fines migration.…”

“…In addition to the difficulties encountered during the characterization of carbonate reservoirs, the presence of fracture networks renders waterflooding techniques ineffective in most cases, which has been ascribed to the storability and permeability contrasts existing between the matrix and the fracture networks, − leading to an early water breakthrough and poor sweep efficiency. Consequently, researchers have focused on the use of inexpensive and environmentally friendly EOR methods to increase oil recovery from carbonate reservoirs.…”

“…Recently, numerous studies have been investigating the use of low salinity water (LSW), nanoparticles (NPs), and surfactants (abbreviated together as LNS) for EOR purposes because of their effectiveness and the relatively low costs incurred in their application. , Low salinity waterflooding (LSWF) or smart waterflooding is reported to be a suitable EOR method because it yields an increase in oil recovery in carbonate reservoirs. − The mechanism identified by different studies to be responsible for the incremental oil recovery under LSWF is mainly wettability alteration, which is caused by multi-ion exchange (MIE), formation of micro-dispersions, and the presence of partitioned surface-active materials. − Zhang et al and Strand et al revealed that the MIE mechanism is crucial for FCRs since the removal of the carboxylic group in the oil from the carbonate surface by Mg 2+ , Ca 2+ , and SO 4 2+ ions increases the flow of water into the matrix pores. Therefore, it has been shown that LSWF is effective in fractured carbonates as well. ,, Nonetheless, LSWF causes fines migration and thus leads to formation damage, which could potentially reduce oil production . Accordingly, NPs are injected with LSW because they possess the tendency to reduce fines migration.…”