Nadeem, Muhammad
(2007)
A Study on Enhanced Oil Recovery by Surfactants for a Malaysian Sandstone Reservoir.
PhD thesis, University of Agriculture,.
Abstract
A laboratory scale investigation into the utilization of conventional and nonconventional
surfactants for Enhanced Oil Recovery (EOR) was conducted using an inhouse
imbibition cell flooded with formation water in the presence of polymers and
alkaline mixtures. The success of chemical enhanced recovery treatment hinges on many
factors; firstly there is a need for the selected chemical mixture to be sufficiently benign
towards the aggressive components of the formation water. Secondly there is a need for the
components of the chemical flooding mixture to possess certain desirable properties
namely, stability, viscosity, extend of IFT reduction, partition coefficient, adsorption and
wettability alteration. Formation water from Angsi field was analyzed for mineral
contents using volumetric analyses and Atomic Absorption Spectroscopy (AAS).
Surfactants and polymers have been examined for temperature stability using Thermo
Gravimetric Analyses (TGA). The viscosities of the polymers have been determined using
a rotary viscometer. The presence of alkali, surfactants and a raise in temperature led to a
decrease in the viscosity of the polymers. Reduction in IFT at the oil/water interface has
been recorded using an interfacial tensiometer. Partition coefficients of the surfactants in
oil and water phases have been calculated. Emulsification and wettability alterations have
been evaluated by an Atomic Force Microscopy (AFM) and contact angle measurements
respectively. BET surface and micropore areas of the cores have been measured.
Sandstone cores possessing suitable porosity and permeability have been characterized and
used for the imbibition studies. The internal structure and mineral profiles of the
sandstones have been illustrated and analyzed using a Scanning Electron Microscopy
(SEM) and an Energy Dispersive X-ray (EDX) respectively. Molecular interactions
between the various components have been elaborated by Fourier-Transform-Infra red
(FTIR) spectroscopy. It was concluded that oil recovery can be significantly enhanced,
when an appropriate mixture of non-conventional anionic surfactants (Aerosol OT & TR)
has been utilized along with alkali and polymer. The preliminary screening results
obtained by an in-house imbibition cell have also been adequately verified by industry
accepted coreflooding experiments. Adsorption mechanism of the surfactants on sandstone
cores is well elaborated by the Langmuir isotherm instead of the Freundlich isotherm.
Adsorption kinetics obeys the Pseudo-second-order kinetics. It can be concluded that the
polymer is responsible to increase the macroscopic displacement efficiency, whereas the
synergistic effect of the surfactants and alkali are responsible to produce an ultra-low IFT
(10" dyne/cm) resulting in a pronounced microscopic displacement efficiency. Nonconventional
surfactants can produce an ultra-low IFT even in minuscule amounts of alkali
and polymer. It was concluded that Low-Alkaline-Surfactant-Polymer (LASP) is not only
an economical technology but it can also enhance oil productiondrastically.
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