STUDY THE EFFECT OF INJECTION TEMPERATURE ON LIQUID C02 FLOODING

Injection of gas carbon dioxide is widely applied in enhance oil recovery method.
This injection will normally utilized characteristic of supercritical fluid of carbon
dioxide to achieve higher recovery of crude oil by displacing the crude oil to the
producing well. It also reduce the viscosity ofcrude oil whilst enable the crude oil to
flow easily to the producing well. However, the sweep efficiency of gas carbon
dioxide to displace the residual oil is low due viscous fingering. Carbon dioxide
flooding usually requires an operating condition of more Minimum Miscibility
Pressure (MMP) to achieve a good displacement of residual oil from injection well to
production well. Besides, most of the application of gas carbon dioxide injection is
combine with other fluids injection such as water alternating gas (WAG),
simultaneous water alternating gas (SWAG) and surfactant alternating gas (SAG).
This combination of fluids injection will increase the sweep of residual oil in the
reservoir and hence increase the tertiary recovery. Therefore, this study will focus on
the alternative way to increase the displacement onthe residual oil from the injection
well to the producing well. Hence, application of injection of liquid carbon dioxide
will be usedto recover the residual oil. Liquid carbon dioxide will sweep the residual
oil in the reservoir especially near the injection well before it vaporizes. The presence
of liquid carbon dioxide displacement will help to reduce the viscous fingering due to
the gas of carbon dioxide and increase the sweep efficiency. The characteristic of
liquid carbon dioxide that diffuse into crude oil will reduce the viscosity ofcrude oil.
Besides, it will reduce the interfacial tension between the carbon dioxide and the
crude oil. Hence, allow crude oil to flow easily to production well. The vaporisation
of liquid carbon dioxide also will help to displace the crude oil and help to carry the
light component of hydrocarbon during the mass exchange. All this had contributed
to the effectiveness of displacing crude oil with liquid carbon dioxide. Study on the
phase behaviour of carbon dioxide with the help of carbon dioxide phase diagram
need to be done to ensure the temperature of injection liquid carbon dioxide below the
bubble point ofcarbon dioxide at desire injection pressure. The effectiveness of liquid
carbon dioxide injection to increase the recovery has to be done through the
experiment. Therefore, liquid carbon dioxide flooding will be done using the relative
permeability system (RPS). Berea core and mineral oil has been used in this experiment. Liquid carbon dioxide injection temperature was at ambient temperature
25 °C at injection pressure of 950psi.
From the experiment, it's found that the percentage recovery of residual mineral oil
was at 20.8 % of OOIP of the berea core. This shows a significant increase in the
residual oil recovery compare to the literature review of four field implementation of
WAG in the reservoir can only yield the highest recovery of 17%of OOIP. On the
other hand, the temperature of injection of liquid carbon dioxide has been varied for
the same injection pressure. This will help us to observe the effect of injected
fluid(liquid carbon dioxide) temperature in the liquid carbon dioxide flooding. The
heat of vaporization of liquid carbon dioxide increases with the decreases in the
temperature. Therefore, this will lead to the increase oftime require for liquid carbon
dioxide to vaporized. Consequently, presence of liquid carbon dioxide to displace the
residual oil in the reservoir will increase before the carbon dioxide vaporizes.
Nevertheless, the validity of this principle need to be verify through the experiment.
Inthis experiment, the injection temperature of liquid carbon dioxide has been reduce
to 20 °C, 15 °C and 5 °C. It's found thatthe recovery of residual oil do increase from
20.8 % of OOIP at ambient temperature of liquid carbon dioxide injection to 26.1 %
of OOIP at injection temperature of 5 °C. This proved that reducing the injection
temperature of liquid carbon dioxide do help increase the displacement efficiency of
residual oil hence increase the recovery.
In conclusion, performance of liquid carbon dioxide injection in enhance oil recovery
is proven to be effective and tertiary recovery inversely proportional with the liquid
carbon dioxide injection temperature.