A New Model for Fracture Gradient


Voy E. Althaus, Exxon Company

5th Formation Evaluation
Symposium of the Canadian Well Logging Society in Calgary, May 5 – 7,



For the past eighteen years fracture gradient has been thought to be some func- tion of overburden stress, horizontal stress and internal fluid pressure. Each author that has published in the intervening years has refined this idea. This paper derives such a model but then uses the same data to turn the entire relationship around to derive and support a new model with the following attributes: 1. Fracture gradient is equal to the least stress field in the earth.