skip to main content


Title: 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.

 
more » « less
NSF-PAR ID:
10305472
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Nature Publishing Group
Date Published:
Journal Name:
Scientific Reports
Volume:
10
Issue:
1
ISSN:
2045-2322
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Micro‐gel particle suspensions (MGPS) have been proposed for enhanced oil recovery (EOR) in reservoirs with harsh conditions in recent years, yet the mechanisms are still not clear because of the complex property of MGPS and the complex geometry of rocks. In this paper, the micro‐gel particle‐based flooding has been studied by our microfluidic experiments on both bi‐permeability micromodels and reservoir‐on‐a‐chip. A method for reservoir‐on‐a‐chip design has been proposed based on QSGS (quartet structure generation set) to ensure that the flow geometry on chip owns the most important statistical features of real rock microstructures. In the micromodel experiments with heterogeneous microstructures, even if the MGPS has the same macroscopic rheology as the hydrolyzed polyacrylamides (HPAM) solution for flooding, MGPS may lead to significant fluctuations of pressure field caused by the nonuniform concentration distribution of particles. In the reservoir‐on‐a‐chip experiments, clustered oil trapped in the swept pores can be recovered by MGPS because of pressure fluctuation, which hardly happens in the HPAM flooding. Compared with the water flooding, the HPAM solution flooding leads to approximately 17% incremental oil recovery, while the MGPS results in approximately 49.8% incremental oil recovery in the laboratory.

     
    more » « less
  2. null (Ed.)
    CO 2 -based enhanced oil recovery is widely practiced. The current understanding of its mechanisms largely focuses on bulk phenomena such as achieving miscibility or reducing oil density and viscosity. Using molecular dynamics simulations, we show that CO 2 adsorption on calcite surfaces impedes decane transport at moderate adsorption density but enhances decane transport when CO 2 adsorption approaches surface saturation. These effects change the decane permeability through 8 nm-wide pores by up to 30% and become negligible only in pores wider than several tens of nanometers. The strongly nonlinear, non-monotonic dependence of decane permeability on CO 2 adsorption is traced to CO 2 's modulation of interfacial structure of long-chain hydrocarbons, and thus the slippage between interfacial hydrocarbon layers and between interfacial CO 2 and hydrocarbon layers. These results highlight a new and critical role of CO 2 -induced interfacial effects in influencing oil recovery from unconventional reservoirs, whose porosity is dominated by nanopores. 
    more » « less
  3. Hydrate surface wettability is a fundamental aspect to better understand agglomeration present in oil bearing petroleum pipelines. Coupling these measurements with hydrate film growth gives further information on kinetic effects that may also be present from natural surfactants in different oils. In situ measurements of wettability (quantified by the contact angle) and film growth rates were performed on cyclopentane hydrate surfaces at atmospheric pressure and subcooling of 4 ◦C. Contact angle and film growth results were obtained for the baseline system (pure cyclopentane), one model oil, and seventeen natural oils (diluted to 0.02 vol% in cyclopentane). Results showed a wide variety of contact angles and film growth values where higher asphaltene contents in the oils corresponded to higher contact angles and lower film growth rates, thought to be from better alignment of natural surfactant molecules at the hydrate/hydrocarbon interface. It was also shown for select oils that increasing the oil concentration in the cyclopentane increases the contact angle and decreases the film growth rate compared to the baseline system. For select oils that had higher contact angles, increasing the water content of the system decreases their contact angle and film growth compared to the baseline system. Isolating different oil fractions for select oils also shows which fractions tend to play a larger role in wettability behavior. Typically, the fractions with more surface active components (asphaltene and resins) are shown to contribute to the higher contact angle and slower film growth rates for select oils. Evidence of the competition between film growth and capillary suction of water into the hydrate has been shown, and a mechanistic breakdown of three different transient scenarios has been proposed. Each of these observed interfacial behaviors gives information on what can be expected from larger scale phenomena, including hydrate agglomeration, with very small oil samples. 
    more » « less
  4. Marine oil contamination remediation remains a worldwide challenge. Siphon action provides a spontaneous, continuous, low-cost and green route for oil recovery. However, it is still limited by the low oil recovery rate due to insufficient internal pathways for oil transport. In this paper, a graphene petal foam (GPF)-based oil skimmer is designed and fabricated by plasma-enhanced chemical vapor deposition (PECVD) for ultrafast self-pumping oil recovery from oil/water mixtures. The hierarchical structure, containing micro- and nano-channels formed by interconnected graphene networks and vertically aligned graphene petals (GPs), respectively, and micro-pores inherited from the 3D interconnected structure of Ni foam, provides multiple fast passages for oil transport. An oil recovery rate of 135.2 L m −2 h −1 is achieved in dark conditions for such oil skimmers, while the value is increased to 318.8 L m −2 h −1 under solar irradiation of 1 kW m −2 because of the excellent solar-heating effect of GPs. Quantitative analyses suggest that 68.8% of such a high oil recovery rate is contributed by the nano-channels and micro-pores, while 31.2% arises from the micro-channels. Our demonstrated GPF oil skimmers exhibit great promise for fast spontaneous and continuous oil contamination cleanup. 
    more » « less
  5. Abstract

    The efficiency of gas recovery in tight gas reservoirs has been a challenge in the oil and gas industry for the past decade because conventional drainage or water‐controlled gas recovery technologies typically have poor performance in low‐permeability reservoirs. To solve this problem, self‐made nanofluid was introduced to enhance drainage gas recovery in a tight gas reservoir. In this paper, nanofluid was prepared by phase reversal technology for application in a tight gas reservoir. Its thermal, acidic, alkaline, and salty stabilities were systematically investigated by using light transmittance as a shortcut index. At the same time, its biodegradability and biotoxicity were evaluated based on the industry/national standard, and the effectiveness of its drainage gas recovery was studied by dynamic gas–water percolation. The results showed that the self‐made nanofluid can be effectively used for drainage gas recovery in tight gas reservoirs. The nanofluid has chemical stability and is environmentally friendly, which fully conforms to the contemporary development trend of the oil and gas industry. The nanofluid can shift the isotonic point of the gas–water relative permeability to the left (its minimum is 1.83% at 6.25 wt.% and maximum is 4.78% at 100 wt.%) and reduce the irreducible water saturation (its minimum is 8.84% at 6.25 wt.% and maximum is 4.28% at 100 wt.%), achieving the purpose of the enhancement of drainage gas recovery. The research results provide technical support for the application of nanofluid to improve the gas production in tight gas reservoirs.

     
    more » « less