Page 84 - A Practical Companion to Reservoir Stimulation

PRACTICAL COMPANION TO RESERVOIR STIMULATION

EXAMPLE E-13
Closure Stress and Proppant Selection Stress (psi) Proppant Optimum 1-Yr NPV
Fracture ($000)
Half-Length, ft
With the data in Table E-6 (use k = 1 md), show the impact of
the closure stress on proppant selection and the resulting 1-yr 4457 Sand 2000 1500
N PV. ISP 1600 2575
Bauxite 700 985
Solution (Ref. Sections 8-3 and 8-4)
Three proppants have been selected: 20140 sand, 20/40 ISP 5571 Sand 1900 1210
and 20/40 bauxite. Furthermore, three closure stresses were ISP 1400 2250
used: 4457 psi, 557 I psi and 6685 psi. In all three cases, after Bauxite 1300 2005
stress effects were accounted for, the polymer-induced dam- 6685 Sand 1100 600
age was taken as 70% (i.e., 30% retained permeability). ISP 1300 1900
Table E-7 contains the results of these simulaions. While Bauxite 1300 1960
the cost of the proppants is disproportionate ($0.09/lb for
sand, $0.67/lb for ISP and $0.75/lb for bauxite), it can be seen Table E-7--Stress, proppant type and NPV.
clearly that proppants that sustain their permeability at higher
stresses result in higher NPVs. For this example, ISP is better
for the two lower stress values, but bauxite overtakes ISP at
the higher stress. If an even lower stress reservoir were to be
fractured, then sand may appear more attractive. The NPV is
affected both by the cost of the proppant and, more impor-
tantly, by the resulting fracture permeability and thus fracture
conductivity.

E-24