A full 3D geomechanical model is developed to model 3D hydraulic fracturing in naturally fractured and layered anisotropic reservoirs. The modeling was achieved using a full 3D anisotropic damage mechanics (ADaM) model implemented in the material point method (MPM). Interface modeling that was demonstrated to control the fracture height in layered reservoir was modeled using multiple modeling tools including imperfect interface and Coulomb friction contact models.
The validation of this 3D anisotropic damage mechanics model is demonstrated on elementary tests and on an actual Eagle Ford well. First, laboratory experiments involving layered media and interfaces were modeled, and numerical results closely matched the experimental results. Then a sensitivity analysis on fracture propagation potentials was performed on two layered specimens by using three interface properties: perfect, weak and de-bonded interfaces. Numerical results showed that fracture propagation was highly affected by the presence and the nature of the interface. Weakly bonded and debonded interfaces played a barrier role, by arresting the fracture propagation. Offset of hydraulic fractures is also demonstrated in specimens with weak interfaces and the presence of a flaw crossing the interface when the flaw is near the injection point. The flaw influenced the propagation height in the layered medium, and an asymmetric half-height was observed with both near and far flaw positions, with a propagation promoted toward the side of the flaw. Finally, a new 3D geomechanical workflow that accounts for 3D fracture planes and interfaces was introduced and illustrated on an Eagle Ford well. The natural fractures are represented using explicit discontinuities estimated from seismic data. The workflow was used to reproduce field observations from an Eagle Ford case, where MPM results matched the microseismic events. The lessons learned were applied to a Wolfcamp B well to better understand its low performance.
The fully 3D geomechanical tool provides the ability to model the interaction of hydraulic fracture planes with the natural fracture network and the layered rock in a 3D volume. The new approach could be used to improve fracture height estimation and to reduce vertical well interferences.
