Pore-scale experimental investigation of oil recovery enhancement in oil-wet carbonates using carbonaceous nanofluids

Abstract

This study investigates the pore-scale displacement mechanisms of crude oil in aged carbonate rocks using novel engineered carbon nanosheets (E-CNS) derived from sub-bituminous coal. The nanosheets, synthesized by a simple top-down technique, were stable in brine without any additional chemicals. Owing to their amphiphilic nature and nano-size, they exhibited dual properties of surfactants and nanoparticles and reduced the oil/brine interfacial tension (IFT) from 14.6 to 5.5 mN/m. X-ray micro-computed tomography coupled with miniature core-flooding was used to evaluate their ability to enhance oil recovery. Pore-scale displacement mechanisms were investigated using in-situ contact angle measurements, oil ganglia distribution analysis, and three-dimensional visualization of fluid occupancy maps in pores of different sizes. Analysis of these maps at the end of various flooding stages revealed that the nanofluid invaded into medium and small pores that were inaccessible to base brine. IFT reduction was identified as the main displacement mechanism responsible for oil recovery during 1 to 8 pore volumes (PVs) of nanofluid injection. Subsequently, wettability alteration was the dominant mechanism during the injection of 8 and 32 PVs, decreasing the average contact angle from 134° (oil wet) to 85° (neutral wet). In-situ saturation data reveals that flooding with only 0.1 wt% of E-CNS in brine resulted in incremental oil production of 20%, highlighting the significant potential of this nanofluid as a recovery agent.

Effect of In-situ Dual Surfactant Formulation on Spontaneous Oil Deformation: A Comprehensive Study from Mechanism Discovery to Oil Recovery Application

“…In addition, we believe that the macroscale displacements could provide some important implications for the tertiary mode. Throughout the literature, the oil clusters are well-connected after waterflooding when the rock sample is strongly oil-wet, , which presents a similar connected structure to that in our secondary mode. In this situation, the stable displacement should occur if the STAC flooding is used as the tertiary mode.…”

New Amphiphilic Tricationic Imidazolium and Pyridinium Ionic Liquids for Demulsification of Arabic Heavy Crude Oil Brine Emulsions

“…One of the most important characteristics for application of amphiphiles as oilfield chemicals is based on their great ability to reduce the IFT at the crude oil/brine water interface . The amphiphiles reduced the IFT of the crude oil/brine water interface below 0.1 mN/m and were used as emulsifiers for enhanced petroleum crude oil recovery . In this respect, the Arabic heavy crude oil sea water IFT measurements were determined in the absence and presence different injection doses part per million (ppm; mg/L) or mM of either IPy-IL or AIPy-IL and are listed in Table .…”

Spontaneous Deformation of Oil Clusters Induced by Dual Surfactants for Oil Recovery: Dynamic Study from Hele-Shaw Cell to Wettability-Altered Micromodel

“…However, the size was reduced by only 1 order of magnitude after chemical flooding for the oil-wet porous media. This difference proves that wettability significantly influences the residual oil size and connectivity . The reason can be explained by the Young–Laplace equation, which is usually used to estimate the capillary pressure (eq ).…”

“…This difference proves that wettability significantly influences the residual oil size and connectivity. 41 The reason can be explained by the Young−Laplace equation, which is usually used to estimate the capillary pressure (eq 8). 42 Specifically, the capillary pressure was negative in the oil-wet porous media, whereas it was positive in the water-wet porous media.…”