Experimental investigation of miscibility conditions of dead and live asphaltenic crude oil–CO2 systems
J Petrol Explor Prod Technol
Experimental investigation of miscibility conditions of dead and live asphaltenic crude oil-CO2 systems
Abdolah Golkari 0 1 2
Masoud Riazi 0 1 2
0 Abbreaviations API Oil API gravity (American Petroleum Institute) ADSA Axisymmetric drop shape analysis FCMP First-contact miscibility pressure (MPa) GOR Gas-oil ratio (scf/bbl) IFT Interfacial tension (mN/m) MMP Minimum miscibility pressure (MPa) P Pressure (MPa) T Temperature (K) VIT Vanishing interfacial tension
1 Enhanced Oil Recovery (EOR) Research Centre, School of Chemical and Petroleum Engineering, Shiraz University , Shiraz , Iran
2 & Masoud Riazi
Carbon dioxide (CO2) injection is a well-established enhanced oil recovery method. The optimization process of CO2 injection is usually performed through estimation of two physical properties, i.e., minimum miscibility and first-contact miscibility pressures (MMP and FCMP) for the crude oil-CO2 system. In this experimental study, the equilibrium IFT of the crude oil-CO2 system is measured at (313.15 and 323.15 K) for two oil types (i.e., live and dead crude oil) using the axisymmetric pendant drop shape analysis method. Vanishing interfacial tension technique is also applied to estimate the MMP and FCMP. The experimental results demonstrate that IFT decreases with different trends as the equilibrium pressure increases for the systems of live oil/CO2 and dead oil/CO2 systems. The IFT test results demonstrate that the estimated MMP and FCMP values of crude oil-CO2 system increase with temperature. It was also observed that the presence of methane gas in the oil phase increases the MMP value, whereas it decreases the FCMP.
Carbon dioxide-(CO2) enhanced oil recovery; (EOR) process; Minimum miscibility pressure (MMP); First-contact miscibility pressure (FCMP); Vanishing interfacial tension (VIT) method; Live asphaltenic oil
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Department of Chemical Engineering, School of Chemical
and Petroleum Engineering, Shiraz University, Shiraz, Iran
Introduction
Enhanced oil recovery (EOR) methods become important
and get attentions in petroleum industry. For this purpose,
gas injection as an efficient enhanced oil recovery
technique has been utilized to recover the remaining oil in
place by reduction of the interfacial tension and viscosity
and maintaining the reservoir pressure
(Jha 1985; Rojas
and Ali 1988)
. Among of the existed gases, use of the
carbon dioxide (CO2) is one of the proposed methods
with relatively low cost and high efficiency to improve oil
recovery
(Ali and Thomas 1996; Alvarado and Manrique
2010; Moritis 2004)
. CO2 injection method has been
suggested for processes of enhanced oil recovery and CO2
sequestration
(Aycaguer et al. 2001; Kokal et al. 1992;
Mathiassen 2003; Sarma 2003)
. In addition, CO2 injection
process is more attracted due to the reduction of
greenhouses gas emissions
(Aycaguer et al. 2001; Gui et al.
2010; Rao and Rubin 2002)
. The CO2 flooding process,
depending on the highest possible operating pressure and
minimum miscible conditions, can be performed at both
miscibility and immiscibility conditions (Wang and Gu
2011). The oil recovery mechanisms that occur in CO2
injection include the oil viscosity reduction,
light-component extraction, IFT reduction, immiscible and miscible
displacements and improving the oil swelling
(Cao 2012;
Holm and Josendal 1974; Mungan 1981; Simon and
Graue 1965)
. These mechanisms could play key roles,
depending on whether the CO2 displacement is miscible
or immiscible. For instance, in immiscible CO2 injection
process the oil viscosity and IFT reduce, these two
mechanisms are among the important oil recovery
mechanisms, whereas the oil-swelling, and
light-components extraction take place in miscible CO2 flooding
process (Martin and Taber 1992).
If the pressure of the injecting fluid increases, the IFT
between flooded fluid (i.e., gas) and oil in reservoir
approaches to zero and consequently capillary force
decreases to a minimum value
(Danesh 1998; Lake 1989)
.
Under this condition, the injecting gas will be able to
mobilize a great amount of trapped oil at pore scale
(Green and Willhite 1998; Stalkup Jr 1983)
. Miscibility
conditions mainly depends on pressure, temperature and
the fluids compositions. It is a condition at which two
fluids can be mixed together so that no separation can be
identified
(Green and Willhite 1998; Orr and Jessen
2007)
. In general, the mechanisms of oil recovery under
miscible conditions are mainly reduction of both capillary
pressure and reservoir fluid viscosity
(Leach and Yellig
1981; Wylie and Mohanty 1999; Zanganeh et al. 2012)
.
From operational point of view, the minimum miscibility
pressure (MMP) is the minimum operating pressure at
which oil recovery is high and displacing gas with
reservoir oil can reach miscibility at reservoir conditions
(Cao and Gu 2013b; Dong et al. 2001; Stalkup 1987)
.
MMP is a key factor on enhanced oil recovery (EOR)
method including CO2 o (...truncated)