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CHAPTER THIRTEEN
Air injection
Abstract
As air has its vast and free resources, it has its economic benefit. This chapter addresses
air injection in shale and tight reservoirs of light oils. In detail, this chapter addresses the
following special issues: (1) kinetic parameters; (2) oxidation reactions; (3) spontaneous
ignition; (4) thermal effect from low-temperature oxidation (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.
Keywords: Air injection; Air requirement; Combustion; Kinetic parameters; Low-
temperature oxidation (LTO); Minimum oil content; Oxidation reactions; Oxygen
consumption rate; Spontaneous ignition.
13.1 Introduction
As shale and tight formations have ultralow permeability, gas injection
has its advantage in terms of injectivity. Gas injection is a relatively effective
method to enhance shale and tight oil and condensate recovery. Natural gas
is short of supply as a clean energy in some countries like China. We may try
to avoid injecting natural gas to recover oil. CO 2 injection needs building of
long pipelines, and thus it is expensive. Air has its vast and free resources. It
has its economic benefit. There exists light oil in most of shale and tight oil
reservoirs. This chapter addresses air injection in shale and tight reservoirs of
light oils.
Initially high-pressure air injection (HPAI) is designed for light oil
reservoirs to make use of high-pressure air energy not heat, while in-situ
combustion (ISC) is designed for heavy oil. Later air injection in some light
oil reservoirs is found to have thermal benefit, for example, in the North and
South Dakota portions of the Williston basin. Kumar et al. (2007) stated that
more than half of the cumulative oil production was contributed by the
thermal effects for the HPAI project in the West Buffalo Red River Unit.
As a result, air injection in light oil reservoirs has gained attention.
Enhanced Oil Recovery in Shale and Tight Reservoirs © 2020 James Sheng.
ISBN: 978-0-12-815905-7 Published by Elsevier Inc.
https://doi.org/10.1016/B978-0-12-815905-7.00013-X All rights reserved. 401 j
