Containment of massive hydraulic fractures
Based on two-dimensional analyses of three cases involving the relationship of linear fracture mechanics to the containment of massive hydraulic fractures (MHF), Terra Tek Inc. concluded that the mechanical properties of the pay zone and the barrier formation, as well as the minimum horizontal in situ stresses for these layers, play important roles in the prediction of hydraulic-fracture containment. The analyses revealed three fundamental results that are useful in general MHF design: (1) hydraulic fractures in a pay zone located between two adjacent barrier layers tend to be contained, provided the stiffness of the pay zone is less than the stiffness of the barrier layers. If the opposite condition exists, barrier penetration is likely; (2) migration of a hydraulic fracture, either upward or downward in an isotropic, homogeneous medium, may be controlled by the density of hydraulic fracturing fluid. If the fluid density gradient is greater (less) than the minimum horizontal in situ stress gradient, then downward (upward) migration is probable; (3) if in situ stress differs between the bounding layers and the pay zone, with greater in situ stress in the bounding layers, then those layers serve as a barrier to vertical extension of the fracture. Fracture propagation into the barrier formation may be detectable by an increase in pumping pressure, occurring as the fracture crosses the interface and extends into the barrier layer. The pressure increase for a given extension into the barrier is a function of the difference in in situ stress between the barrier and the pay zone layers and the height of the pay zone.
- OSTI ID:
- 5769471
- Journal Information:
- Soc. Pet. Eng. J.; (United States), Journal Name: Soc. Pet. Eng. J.; (United States) Vol. 18; ISSN SPTJA
- Country of Publication:
- United States
- Language:
- English
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