Page 88 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

70 Thomas Russell et al.

3.7.2 Splitting method for integration of two-phase systems 160
3.7.3 Exact solution for the auxiliary system 162
3.7.4 Lifting equation 163
3.7.5 Inverse mapping 163
3.7.6 Implementation of fines migration using reservoir simulators 165
3.8 Conclusions 167
Nomenclature 168
Greek symbols 169
Super/Subscripts 170
References 170

3.1 INTRODUCTION

Migration of natural reservoir fines is one of the main formation
damage mechanisms during waterflooding and enhanced oil recovery
(EOR) operations (Civan, 2014). Formation damage is induced by mobi-
lization, migration, and straining of particles which are initially attached
to the rock surface. Fig. 3.1 shows fine particles attached to grains,
detached particles, and those strained in thin pores.
The most common fines in subterranean reservoirs are clays (e.g.,
kaolinite, illite, chlorite). Initially, fine particles coat the rock surface, so
their detachment causes a small increase of permeability. However,
straining of particles in thin pores reduces the number of available flow
paths in the porous media, causing significant permeability decline.
Fig. 3.2 shows a Scanning Electron Microscope (SEM) image of kaolin-
ite leaflets on a grain surface. The platelet shape of the kaolinite particles
means that although detachment of kaolinite will have a small effect
on the porosity, detached particles can strain in even large pore throats
(Al-Yaseri et al., 2017; 2016). Sarkar and Sharma 1990 report typical
permeability decrease for fines migration during single-phase flow of
100 1000 times, although the presence of residual oil decreases this
number by 10 100.
Fig. 3.3 shows the primary forces acting on an attached particle. The
drag and lifting force will act to detach the particle, while the electrostatic
and gravitational force will act against particle mobilisation. It is com-
monly assumed that at the moment of detachment, the particle rotates
around a neighboring particle or an asperity on the grain surface, so the