A hydrophobically
associating hydroxyethyl cellulose (HAHEC) used
for enhanced oil recovery (EOR) was studied in the present study.
The effects of HAHEC concentration, temperature, and shear rate on
apparent viscosity of HAHEC solution were explored. Results show that,
because of the hydrophobic association of HAHEC molecules and the
formation of supramolecular aggregates, the viscosifying performance
of HAHEC is obviously better than that of HEC. But the apparent viscosity
of HAHEC solution is sensitive to the temperature and it declines
significantly especially when the temperature is less than 50 °C.
HAHEC solution also has satisfactory shear resistance performance,
and its apparent viscosity can basically return to the initial value
after withdrawing severe shear action. Moreover, HAHEC shows favorable
surface and interfacial activities because of the adsorption and arrangement
of HAHEC molecules onto a water/air surface and water/oil interface.
Sand pack core experiments were conducted to investigate the EOR ability
of the HAHEC flooding system; results display that both the resistance
factor and the residual resistance factor of HAHEC solution in cores
are higher than those of HEC solution. Favorable EOR performance of
the HAHEC flooding is proved, and high incremental oil recovery can
be achieved with the application of optimized injection concentration,
injection rate, and injection slug size after initial water flooding.
In addition, the emulsification phenomenon is obvious during the HAHEC
flooding because of the favorable surface and interfacial activities
of HAHEC.
Monoisopropanolamine
(MIA) and monoethanolamine (MEA), which are
two kinds of organic alkalis, present favorable potential for enhanced
oil recovery. When MIA and MEA are respectively applied, the minimum
oil/water interfacial tension (IFT) can be reduced to about 1 mN/m,
the crude oil can be emulsified, and the originally oil–wet
sand surface can be altered to weak water-wet status. To display the
synergistic effect of surfactant and organic alkalis, a surfactant/compound
organic alkalis (MIE/MEA) flooding system (SMM), which consists of
0.10 wt % SDBS, 0.15 wt % MIA, and 0.10 wt % MEA, is screened. This
system can reduce the minimum oil/water IFT to an ultralow value which
contributes to the emulsion stability. Results of sandpack flooding
tests indicate that although the incremental oil recovery can be continuously
enhanced with the increase of the SMM slug size, there is an optimal
injection size (0.8 PV in this study) when the expense is taken into
consideration. As for the effect of the injection type, the highest
incremental oil recovery (21.86% OOIP) is achieved when organic alkalis
(MIA/MEA) are simultaneously injected with the SDBS. During the SMM
flooding, emulsification is a crucial flooding mechanism, and most
of the incremental oil is extracted in the form of emulsified oil
droplets. Moreover, the injection rate is optimized (0.5 mL/min) for
the SMM flooding system to achieve a satisfactory incremental oil
recovery.
In
this study, a modified nanolaponite was applied with foaming
agent XR-1 to form a foam flooding system for enhanced oil recovery.
The system formula was screened as 0.40 wt % XR-1 + 0.25 wt % nanolaponite,
and both the foaming volume and the drainage half-time reach satisfactory
values using the formula, proving the synergistic effect of the nanolaponite
and XR-1 for the contribution to nitrogen foam properties. Micromodel
displacement experiments were performed to investigate the microstatic
stability and displacement behavior of this system. Results show high
microstatic stability of nitrogen foam within the test time when XR-1
and nanolaponite are applied together. According to the matching rule
between the foam bubble and pore throat, the nanolaponite stabilized
nitrogen foam belongs to the ideal bubble’s throat blocking
model, which can significantly improve the conformance efficiency.
Moreover, the obvious oil dispersion and emulsification phenomena
also contribute to the sweep efficiency. Single and double sand pack
core displacement experiments were conducted to study the enhanced
oil recovery (EOR) ability of this system in homogeneous and heterogeneous
reservoirs, respectively. Results display that the nanolaponite stabilized
nitrogen foam has favorable EOR ability, and the incremental oil recovery
is considerable in both single and double core displacement experiments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.