Hydraulic fracturing to determine Hydraulic fracturing to determine S3

Hydraulic fracture initiation in vertical wellHydraulic fracture initiation in vertical well

= 3 − − 2 − ΔP − = −σminθθ

Shmin SHmax Pp σΔTT0

Leako� test (mini-frac, FIT, XLOT)Leako� test (mini-frac, FIT, XLOT)

© Cambridge University Press (Fig. 7.2, pp. 211)Zoback, Reservoir Geomechanics

from instantaneous shut-in pressure from instantaneous shut-in pressure

© Cambridge University Press (Fig. 7.3, pp. 213)

S3

Zoback, Reservoir Geomechanics

© Cambridge University Press (Fig. 7.3, pp. 213)Zoback, Reservoir Geomechanics

Step-rate testStep-rate test

© Cambridge University Press (Fig. 7.5, pp. 216)Zoback, Reservoir Geomechanics

Be careful!Be careful!

When When integrate density logs integrate density logs

© Cambridge University Press (Fig. 7.4, pp. 214)

∼S3 Sv

Zoback, Reservoir Geomechanics

What about What about ??

so

or

SHmax

ΔP = −Pb Pp

= 3 − − +SHmax Shmin Pb Pp T0

= 3 − (T = 0) −SHmax Shmin Pb Pp

Does it work?Does it work?Consider a system with compressibility βs

=βsΔVs

Vs

1

ΔP

ΔP = Δ1

βsVs

Vs

=ΔP

Δt

1

βsVs

ΔVs

Δt

Answer: Not very well.Answer: Not very well.