R e c all: S t at e o f s t r e s s s u r r o u n d in g a ...

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Recall: Recall: State of stress surrounding an State of stress surrounding an arbitrarily deviated well arbitrarily deviated well © Cambridge University Press (Fig. 8.1b, pp. 237) Zoback, Reservoir Geomechanics
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Transcript of R e c all: S t at e o f s t r e s s s u r r o u n d in g a ...

Recall: Recall: State of stress surrounding anState of stress surrounding an arbitrarily deviated wellarbitrarily deviated well
© Cambridge University Press (Fig. 8.1b, pp. 237)Zoback, Reservoir Geomechanics
=RB
T B
σzz
σθθ
τθz
σrr
= − 2ν( − ) cos 2θ − 4ν sin 2θσ33 σ11 σ22 σ12
= + − 2( − ) cos 2θ − 4 sin 2θ − ΔPσ11 σ22 σ11 σ22 σ12
= 2( cos θ − sin θ)σ23 σ13
= ΔP
Principal eective stresses around thePrincipal eective stresses around the wellborewellbore
σtmax
θz ‾ ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√
= ( + − ) 1
θz ‾ ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√
Example: Reverse faultingExample: Reverse faulting
Find the minimum and maximum tangential stress for an open hole well that is oriented from North and deviated from vertical at a depth of km. Assume a hydrostatic pore pressure gradient, a Poisson ration of , and a balanced drilling operation.
S =
© Cambridge University Press (Fig. 8.1a, pp. 237)Zoback, Reservoir Geomechanics
Normal Strike-slip Reverse
Normal Strike-slip Reverse