Miscibility condition is an essential parameter for EOR
(Enhanced Oil Recovery) process. In order to optimize the process of
CO2 injection, estimating miscibility pressure (MMP and FCMP) should
be performed. Slim tube method has been widely used by in...
Miscibility condition is an essential parameter for EOR
(Enhanced Oil Recovery) process. In order to optimize the process of
CO2 injection, estimating miscibility pressure (MMP and FCMP) should
be performed. Slim tube method has been widely used by industry for measuring miscibility condition. But, it consumes more time, sample,
and no standard specification and procedure.(Johns et al., 2000; Johns
and Orr, 1996; Luo and Chen, 2001) On the other hand, VIT (Vanishing
Interfacial tension) method is cost effective, quick (1-2 days) and
accurate for determining of MMP using less crude oil sample. (Sequeira,
2008) And, previous many experiments for investigating miscibility
condition have been implemented using dead oil. That is why main
objectives of this study is to determine CO2-Synthetic oil’s miscibility
condition using VIT (Vanishing Interfacial Tension) and visual
observation method at reservoir condition. Dead oil was mixed with
methane gas to manufacture synthetic oil and simulate real reservoir
condition. Constant Composition Expansion Test was also conducted to
measure Pb (bubble point pressure). It is compared to the pre-tested
data from authorized organization (LEMIGAS) and validate reliability of
synthetic oil. Measured Pb is 1075 psi at 68.8 °C. This result is
similar to LEMIGAS's pvt data (1,116 psi). It presents that the
methane gas was totally soluble inside M-37 dead oil and the
experimental method was reliable. Also, Pb was measured as a function
of GOR (200, 270 SCF/STB) and temperature (40, 60, 68 °C) to find
correlation between them. After that, miscibility condition which is
- III
MMP (Minimum Miscibility Pressure) and FCMP (First Contact
Miscibility Pressure) are obtained through VIT method by extrapolating
two linear slope line (first, second slope) to determine miscibility
pressure (MMP, FCMP) respectively. VIT method was also conducted
to show the effect of solution gas, temperature and oil composition on
miscibility condition. The effect on FCMP of solution gas is minor. On
the other hand, estimated FCMP is increased much more than
determined MMP for both dead oil and synthetic oil due to temperature
effect. As a result, temperature effect compared with solution gas
effect is more pronounced parameter. When comparing heavier oil
(25.2°) with light oil (41.38°), heavier oil has three distinct pressure
intervals. It shows the presence of heavier oil components at the
interface with CO2 and it affects to the appearance of second, third
intervals and slope reduction. Also, by observing the oil drop color and
shape, miscibility condition can be determined. Determining MMP and
FCMP by Visual IFT observation has high reliability with low error
(%) compared to VIT (Graphical extrapolation) method. Based on
accurate evaluation of the miscibility condition, this study can contribute
to the design and performance of a CO2 injection EOR project in a field
application by ensuring a miscible CO2 flooding process with high oil
recovery.
Keyword: Synthetic oil-CO2 miscible condition (MMP, FCMP),
VIT (Vanishing Interfacial Tension) method, CCE test,
Visual observatio