Page 171 - Reservoir Formation Damage

Paniculate Processes in Porous Media 153

Civan's equation using
A=4.60, 6=0.153, C=1.52

Gruesbeck and Collins data

0 10 20 30 40
c p, Particle Concentration, Ib/gal
(Reynolds number could not be used
due to insufficient data)
Figure 8-6. Chart for determination of the particle bridging conditions using
the aspect ratio and particle Reynolds number (modified after Civan, 1994;
reprinted by permission of the U.S. Department of Energy).

The above formulation is a simplistic approach. In reality, the pore and
pore throat sizes are distribution functions, which vary by damage or
stimulation, as shown in Figure 8-7. This can be considered by the
methods developed by Ohen and Civan (1993) and Chang and Civan
(1997), as described in Chapter 5.

Dislodgment and Redeposition of Particles at Pore Throats

Gruesbeck and Collins (1982) observed that the effluent particle con-
centration tended to fluctuate during constant flow rate experiments. Such
phenomena did not occur during constant pressure difference experiments,
which are more representative of the producing well conditions.
They explain this behavior by consecutive dislodgment and formation
of plugs at the pore throats. They postulate that, in heterogeneous systems,
when a suspension of particles of various sizes flow through a porous
media made of a wide range of grain sizes, narrow pathways are likely
to be plugged first, diverting the flow to wider pathways, which transfer