文档介绍：Lesson 4 C
Fracture Gradient Determination
Harold Vance Department of Petroleum Engineering
Fracture Gradient Determination
Hubbert and Willis
Matthews and Kelly
Ben Eaton
Christman
Prentice
Leak-Off Test (experimental)
Harold Vance Department of Petroleum Engineering
Fracture Gradient Determination
Read AWC Chapter 4 all
Harold Vance Department of Petroleum Engineering
Well Planning
Safe drilling practices require that the following be considered when planning a well:
Pore pressure determination
Fracture gradient determination
Casing setting depth
Casing design
H2S considerations
Contingency planning
Harold Vance Department of Petroleum Engineering
Harold Vance Department of Petroleum Engineering
The Hubbert & Willis Equation
Provides the basis of fracture theory and prediction used today.
Assumed elastic behavior.
Assumed effective stress exceeds the minimum by a factor of 3.
Harold Vance Department of Petroleum Engineering
Harold Vance Department of Petroleum Engineering
The Hubbert & Willis Equation
If the overburden is maximum, the assumed horizontal stress is:
sH = 1/3(sob - pp) + pp
Equating fracture propagation pressure to minimum stress gives
pfp = 1/3(sob - pp) + pp
Harold Vance Department of Petroleum Engineering
The Hubbert & Willis Equation
pfp = 1/3(sob - 2pp) (minimum)
pfp = 1/2(sob - pp) (maximum)
Harold Vance Department of Petroleum Engineering