Black Nanosheet-Enhanced Low-Salinity Water System for Improving Oil Recovery in a Low-Permeability Conglomerate Reservoir

Abstract

Black nanosheets (BNs) and low-salinity water (LSW) flooding are two effective methods for improving oil recovery in low-permeability or ultra-low-permeability petroleum reservoirs. The former focuses on emulsification and interfacial tension reduction, while the latter focuses on wettability alteration. Combining BN with LSW is expected to achieve dual effects in oil recovery. However, there has been no research on the combination effect of BN and LSW on conglomerate reservoirs. Therefore, this study aims to investigate the oil imbibition mechanism of the BN–LSW composite system in the tight reservoir of Mahu Oilfield. The interfacial properties of the BN–LSW composite system were evaluated in terms of the oil–water interfacial tension, crude oil emulsification capability, and three-phase contact angle between oil, water, and rock. Through the imbibition experiment of the natural cores in Mahu Oilfield, the imbibition differences between single systems and the BN–LSW composite system were compared. The results showed that the BN–LSW composite system had minimal impact on the interfacial tension between oil and water compared to formation brine, LSW, and BN solution. However, the composite system demonstrated a significant emulsification effect with Mahu crude oil and alterated the wettability of the core. Compared to the single systems, the imbibition rate of the BN–LSW composite system was higher, resulting in an improved imbibition effect. The NMR T 2 signal explained the synergistic core imbibition effect of the BN–LSW composite system at the microscopic scale. The research outcomes of this study can provide a new approach for developing low-permeability and ultra-low-permeability reservoirs, holding practical value and reference significance.

Dispersion Stability and Oil Displacement Effect of Modified Black Nanosheet

“…When the concentration of amphiphilic molybdenum disulfide (KH550-MoS 2 ) nanosheets was 0.005%, the interfacial tension with crude oil decreased to 2.6 mN/m, and the contact angle decreased from 131.2 to 51.7°. Zhu et al 24 proposed a composite oil displacement system of BN and low-mineralization water (LSW) based on BNs. BN-LSW can give full play to the synergistic effect of the two.…”

“…BN-LSW can give full play to the synergistic effect of the two. Zhu et al , also examined the oil recovery effects of the BN-LSW composite imbibition system through imbibition in both tight sandstone and conglomerate reservoir cores, respectively. The BN-LSW composite system demonstrated excellent performance in wettability reversal and reducing interfacial tension, which contributed to its superior imbibition effect compared with individual BN and LSW systems for oil displacement.…”

Development of Anionic-Modified Black Nanosheet and Its Oil Imbibition Performance in Ultralow-Permeability Reservoirs

“…When the concentration of octadecyl-modified black nanosheet reaches 100 mg/L, they reduce the oil–water interfacial tension from 18.47 to 0.27 mN/m by forming multilayer adsorption at the oil–water interface. Zhu et al , found that black nanosheets could also synergize with low-salinity water to reduce interfacial tension, alter core wettability, enhance emulsification properties, and improve imbibition oil recovery performance. Yao et al modified black nanosheet with different chain length modifiers to change their hydrophilic–lipophilic values, finding that the longer the carbon chain length of the modifier, the closer the nanosheets approached neutral wetness and the stronger the interfacial activity.…”