Title of Thesis
To Investigate The Use Of Air Injection To Improve Oil Recovery
From Light Oil Reservoirs
Mehran University Of Engineering & Technology,
|Number of Pages|
|Keywords (Extracted from title, table of contents and
abstract of thesis)|
Reservoirs, Injection, Recovery,
Combustion, Investigate, Pressure, Oil, Utilization, Model,
Oxidation, Generation, Air, Light, Improve, Effect
Air injection into
light oil reservoirs is now a proven field technique, because of the
unlimited availability and low access cost of the injectant. One of
the key of a successful air injection project is the evaluation of
the process by carrying out representative laboratory studies. In
this research, experimental set up has been developed to understand
air injection process for improving oil recovery for depleted light
oil reservoirs and the parameters on the basis of different
petrophysics and fluid sample properties.
In order to provide reliable experimental data, pressure and
temperature experiments (upto 11032 KPa and 600 °C), at
non-Isothermal conditions ramp of 5 oC/ min., were performed with
unconsolidated cores (sand pack) and reservoir oils, at
conditions of the air injection process into light oil reservoirs.
The effects of porous media type, gas flux, heat input, water
saturation and total pressure on the rates of the insitu oxidation
reaction were measured. When air is injected, the oxygen contained
in the air (mainly of 79 % N2 and 21% O2) reacts with the
hydrocarbons in place, by oxidation reaction. The produced
combustion gases consisting of CO2, CO, O2 and N2 depend on the
temperature conditions and the nature of the crude oil. The
generation of a high temperature oxidation zone is preferable for
its higher oxygen uptake potential, it’s more efficient carbon
oxides generation and the creation of an oil bank downstream of the
thermal front, both of the latter factors contribute to the
improvement of the recovery. In both cases, the important point to
assess is the oxygen consumption to prevent oxygen arrival at the
producers and to sustain the combustion front. This is one of the
main objectives of the air injection experiments.
By continuous analysis of the produced gases from the reactor, at
linearly increased temperature rate, it was found that combustion of
crude oil in porous media follows a complex series of reactions.
These reactions can be divided into three sequences :( 1) low
temperature oxidation, (2) fuel deposition, and (3) fuel combustion.
A model is proposed to analyze and differentiate among these
reactions. The method developed is reasonably fast and can be used
to measure the oxidation and deposition of fuel for a given crude
oil and porous medium.
The major conclusions are:
1. 100 percent utilization of oxygen was observed.
2. Significant oil recovery was achieved about 85 percent of
original oil in place(OOIP).
3. The generation of flue gases by oxidation process was very
efficient in terms of carbon oxides with an average percentage of
gas composition of 10 % CO2 and
4 % of CO and balance unreacted oxygen.
4. The H/C ratio for the deposited fuel decreases when temperature
5. Increasing the injection pressure of system decreases the m-ratio
Expressions were obtained for low temperature oxidation rate of oil,
the fuel deposition rate and the burning rate of fuel as a function
of fuel concentration
The relative reaction rate of carbon oxidation was used. The
activation energy of each reaction was different for most of the
runs. A significant effect of the heat input on activation energy
was observed, a lower heat input producing larger activation energy.
The effect of total pressure up to 11032 KPa indicated kinetic
control with 21 % Oxygen partial pressure.
This research will contribute to the overall understanding of air
injection process and enable to be made of the most appropriate
technique for a given reservoir. Use of less expensive method in
tertiary phase will encourage the producers for additional recovery
in this area.