Page 233 - Geothermal Energy Systems Exploration, Development, and Utilization

4.9 Sustainability of Treatment 209

W
s eff
Proppant
crushing,
Formation
compaction
X f

Filtrate invasion,
filter cake
(fracture face damage)
Rock detritus
(mechanical
erosion and fines
migration during
fracture creation)
Proppant

Gel residues,
chemical precipitates s eff
Proppant
embedment zone

Figure 4.11 Conceptual model of fracture face damage and
fines production and pore blocking of a system fracture with
not well designed proppants (Legarth, Huenges, and Zim-
mermann, 2005).
4.9.1.2 Coated Proppants
Adding coated proppants (a kind of resin on the surface of the proppants) at the
end of the treatment (typically 20% of the total amount) leads to sustainable and
long-term conductivity of the fracture especially if a production well is concerned.
These proppants are interconnected due to the special coating and act as a barrier
in the near-wellbore region and avoid a flow-back of proppants into the well during
production.

4.9.2
Thermal Stimulation

Little is generally known, about the sustainability of thermal stimulation mea-
sures, and to the authors’ knowledge, no systematic investigations into this topic
are publicly available to this day. However, it has been recognized at thermal
stimulation measures on Icelandic wells that thermally induced fractures seem to
be self-propping, in that no additives have to be admixed during the stimulation
treatment.