Page 74 - Enhanced Oil Recovery in Shale and Tight Reservoirs

CHAPTER THREE

Asphaltene precipitation and
deposition in a huff-n-puff

process

Abstract

Asphaltene precipitation and deposition may cause formation damage in conventional
reservoirs. In shale and tight reservoirs, pore and throat sizes are smaller than those in
conventional reservoirs. This problem could be more serious in shale and tight reser-
voirs. This chapter is dedicated to the asphaltene precipitation and deposition in a
huff-n-puff process. Experimental results and numerical analysis are presented. The
mechanisms of asphaltene deposition are discussed. Effect of asphaltene deposition
on huff-n-puff optimization is also discussed.

Keywords: Asphaltene precipitation; asphaltene deposition; formation damage; pore
throat.

3.1 Introduction

It has been reported that asphaltene precipitation and deposition may
cause formation damage in conventional reservoirs. In shale and tight reser-
voirs, pore and throat sizes are smaller than those in conventional reservoirs.
This problem could be more serious in shale and tight reservoirs. From
another angle, huff-n-puff has been found to an effective EOR method.
This chapter is dedicated to the asphaltene precipitation and deposition in
a huff-n-puff process. Experimental results and numerical analysis are
presented.

3.2 Experiments of asphaltene precipitation and
permeability reduction

Maroudas (1996) found that particles with a size greater than 1/3 of
the size of a pore or a throat would block the pore or the throat. It was found
that if the 1/7 rule was used, oil recovery was improved. Ershaghi et al.
(1986) suggested to use the more stringent 1/7 rule. The known 1/3-1/7

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/B978-0-12-815905-7.00003-7 All rights reserved. 61 j