Page 434 - Enhanced Oil Recovery in Shale and Tight Reservoirs

402 Enhanced Oil Recovery in Shale and Tight Reservoirs

This chapter addresses several special issues related to air injection in shale
and tight reservoirs:
(1) Kinetic parameters
(2) Oxidation reactions
(3) Spontaneous ignition
(4) Thermal effect from low-temperature oxidation (LTO)
(5) Oxygen consumption rate in low-temperature oxidation
(6) Minimum oil content for combustion
(7) Air requirement for combustion
(8) EOR mechanisms and EOR potential in shale and tight reservoirs
Before addressing these issues, fundamental laboratory measurements
about air injection are introduced.

13.2 Laboratory experimental facilities

To facilitate understanding of air injection, equipment and instruments
to study air injection are briefly introduced. They are thermogravimetry (TG)
and differential scanning calorimetry (DSC), and small batch reactor (SBR),
ramped temperature oxidation, combustion tube, and accelerating rate
calorimetry (ARC). Turta and Singhal (2001) listed laboratory tests needed
for air injection projects.

13.2.1 Thermogravimetry
In a thermogravimetric apparatus, a sample (oil) is put in a crucible which is
placed in a sample holder, as shown in Fig.13.1. The holder is heated by a
controllable heating program with a continuous gas flow. The gas could
be air, pure oxygen, or nitrogen. The gas called purging gas will contact
and displace the vapor phase of the sample and the remaining weight
of the sample is recorded at different temperatures. The experiment is
performed at atmospheric pressure. The experimental data are analyzed in
the method described in Section 13.3.1.

13.2.2 Differential scanning calorimetry

In a DSC apparatus, a sample (oil) is put in a container. An example
apparatus is shown in Fig.13.2. The sample is heated by a controllable
heating program (1e10 C/min) with a continuous gas flow. The gas could

be air, pure oxygen, or nitrogen. During the experiment, the heat flow
(watt per second) is recorded at different temperatures. The data on positive
deviation in heat flow from the crude-oil sample compared with a reference