Page 167 - Enhanced Oil Recovery in Shale and Tight Reservoirs

CHAPTER SEVEN

Water injection

Abstract
In this chapter, research results on experimental and simulation studies are presented
to evaluate the EOR potential of water injection. Water can be injected in a huff-n-puff
mode or a flooding mode. Their performance is compared. Water injection is also
compared with gas injection. At the end, field performance of water injection is
summarized. Other modes of water injection are also briefly mentioned.

Keywords: Field performance; Huff-n-puff; Waterflooding; Water injection; Water
injection modes.

7.1 Introduction
Waterflooding is the most practiced method to produce oil in
conventional reservoirs. One main concern for waterflooding in shale and
tight reservoirs is injectivity. Therefore, there are not many water injection
projects in the United States, but quite a few in Chinese tight formations. In
this chapter, we present research results on experimental and simulation
studies to evaluate the EOR potential of water injection. Water can be
injected as a huff-n-puff mode or a flooding mode. Their performance is
compared. At the end, field performance of water injection is summarized.
Other modes of water injection are also briefly mentioned.

7.2 Waterflooding
Although there is a concern of water injectivity, field projects per-
formed in US so far did not show the problem as serious as expected in shale
reservoirs (Hoffman and Evans, 2016). Many tight reservoirs in China did
not show injectivity problem either.
Song and Yang (2013) used Bakken cores to conduct a waterflooding

experiment. The oil viscosity was 2.17 cP at 20 C and at an atmospheric
pressure. The core permeability was 0.27 mD and the porosity was 0.23.
The initial oil saturation was 0.55. The oil recovery factor at the break-
through was 0.48 at 0.36 pore volumes of injection. The total oil

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/B978-0-12-815905-7.00007-4 All rights reserved. 151 j