Page 159 - A Practical Companion to Reservoir Stimulation

PRACTICAL CONSIDERATIONS FOR FRACTURE TREATMENT DESIGN

the loading force over a larger area. There are several varie- higher permeabilities maximizes potential production, a fact
ties of resin-coated sand. The resin can be precured or hard- substantiated by the proppant permeability values now re-
ened during the manufacturing process or cured in the forma- ported throughout the industry. Originally, proppant perme-
tion. Curable resins are often used strictly for controlling ability charts were derived by performing short-term labora-
proppant flowback after treatments. In recent years, dual- tory tests on proppants at varying closure pressures. Recent
coated resins have become increasingly popular. These developments have shown that this type of test procedure
proppants have the increased strength of a hardened inside greatly overpredicts the ultimate permeability of a given
coating and reduced point loading from a curable outside proppant. Leaving the proppant exposed to a high closure
coating. pressure over a longer period of time substantially reduces its
Fractures exposed to even higher stresses need specialized effective permeability. Recent work shows that proppants
man-made proppants. These proppants include intermediate should. be exposed to closure pressures for several days
strength ceramics, zirconia and bauxite. Bauxite is an alumi- before permeability measurements are made.
num oxide material and is perhaps the best proppant available In the past, the standard proppant permeability and con-
today for resisting crushing. Zirconia proppant is made from ductivity tests were performed in a test cell where the proppant
zirconium oxide, and the ISP proppants are blends of alumi- was contained between two parallel steel plates. Pressure
num oxide and silicone oxide. could be applied directly, and downhole temperatures could
be readily simulated by heating the cell. The permeability
P-2.2: Stress and Time Effects was measured by flowing 2% KCl water through the pack
In general, as many attempts for design optimization demon- and then applying Darcy’s law. Thus, the permeability of a
strate, treatments must incorporate more proppant at higher proppant pack (related to the propped width as shown earlier
slurry concentrations. Furthermore, using proppants with by the proppant concentration) can be measured at various

Propped Number of Propped Number of
Mesh Size Width Particle Width Particle
Diameters (2 Ib/ft2) Diameters
Northern White Sand 12/20 0.1 2 2.4 0.24 4.8
16/30 0.1 2 3.4 0.24 6.8
20140 0.1 2 4.8 0.24 9.6

Texas Brown Sand 12/20 0.12 2.4 0.24 4.8
16/30 0.12 3.4 0.24 6.8
20140 0.13 5.2 0.26 10.4
Curable Resin-Coated Sand 12/20 0.13 2.6 0.26 5.2
16/30 0.13 3.7 0.26 7.4
20140 0.12 4.8 0.24 9.6

Precured Resin-Coated Sand 12/20 0.12 2.4 0.24 4.8
16/30 0.1 1 3.1 0.22 6.2
20140 0.1 1 4.4 0.22 8.8
ISP 12/20 0.10 2.0 0.20 4.0
20140 0.10 4.0 0.20 8.0
ISP-Lightweight 20140 0.12 4.8 0.24 9.6
Sintered Bauxite 16/20 0.09 2.3 0.18 4.6
20140 9.09 3.6 0.18 7.2
40170 0.09 7.3 0.18 14.6
I I I I I
Zirconium Oxide 20140 0.10 4.0 0.20 8.0
Table P-2-Propped fracture width for various proppants and proppant concentrations. (Proppant concentration here refers to
the total mass of proppant injected divided by the generated fracture area.)

P- 3