Page 96 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

78 Thomas Russell et al.

release. The main result is that the laboratory data can be matched with
equal precision by the slow-particle model and by the delay-fines-release
model. The obtained parameters are also used for field-scale prediction of
injectivity decline during low-salinity water injection. Exact solutions for
1D low-salinity waterflooding with a delay in fines release and fines
straining are derived using the splitting mapping, separating two-phase
flow equations from the system of equations expressing fines release,
migration, and straining.
The structure of the text is as follows. Section 3.2 presents governing
equations for single-phase colloidal flow in porous media with particle
detachment modeled by the maximum retention function. Section 3.3
derives an exact x,t-solution for fines migration under high injection rates
and matches the laboratory coreflood data. Section 3.4 derives an exact r,t-
solution for well inflow performance with fines migration; well behavior is
predicted using the model coefficients obtained by the tuning of the labora-
tory coreflood data. Section 3.5 derives an exact x,t-and r,t-solutions for
fines migration, mobilized by low-salinity water; x,t-solution matches the
laboratory coreflood data and tunes the model coefficients, which is used by
well behavior prediction. Section 3.6 derives an exact x,t and semianalytical
r,t-solutions for single-phase fines migration accounting for the delay in fines
release by low-salinity water. Section 3.7 derives an exact r,t-solution for
two-phase fines migration during low-salinity water injection into oilfield;
the section discusses how the solution can be applied for well injectivity in
3D reservoir simulation.

3.2 GOVERNING EQUATIONS FOR FLOW WITH
FINES MIGRATION

In this section, we present the torque balance condition for
mechanical equilibrium of fine particles attached to the rock surface
(Section 3.2.1) and use it further to derive the maximum retention con-
centration as a function of flow velocity and salinity (Section 3.2.2). The
mass balance equation for suspended, attached and strained particles, rate
expressions for straining and attachment, and the maximum retention
function form a closed system of equations describing suspension/colloidal
flow in porous media with particle detachment (Section 3.2.3).