Page 62 - Primer on Enhanced Oil Recovery

Oil recovery stages and methods
7

Abstract

The recovery of hydrocarbons historically was done through only two main stages: pri-
mary and secondary recovery. Primary extraction is carried out at the expense of the natu-
ral energy of the reservoir, while secondary extraction of hydrocarbons is carried out at
the expense of the energy introduced into the reservoir from the outside, by injecting gas
and/or fluids, to maintain or increase the initial energy in the reservoir.
Enhanced Oil Recovery comes after the above and aims to increase oil retrieval from the
oil reservoir.

chapter outline

7.1 Primary recovery 53
7.2 Secondary recovery 54
7.2.1 Waterflooding 54
7.2.2 Gas injection 56
7.3 Why enhanced oil recovery (EOR) methods 58
7.4 Sweep efficiency 61
Further reading 63

The recovery of hydrocarbons develops through two main stages: primary and sec-
ondary recovery. Primary extraction is carried out at the expense of the natural
energy of the reservoir, while secondary extraction of hydrocarbons is carried out at
the expense of the energy introduced into the reservoir from the outside, by inject-
ing gas and/or fluids, to maintain or increase the initial energy in the reservoir.

7.1 Primary recovery

During primary extraction, the energy to move oil through reservoir into the pro-
duction well is obtained by: gravity forces, expanding rock and liquid, releasing
and expanding gas dissolved in oil while reducing reservoir pressure (depletion
drive), expanding the gas cap or active aquifer, or a combination of these factors
(Fig. 7.1).

Primer on Enhanced Oil Recovery. DOI: https://doi.org/10.1016/B978-0-12-817632-0.00007-4
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