Hydraulic Fracturing coupled with Reservoir Simulation


Water injection above fracture propagation pressure has been extensively used for secondary oil recovery in the Dan Field, generating fractures whose length in some cases exceeds 2000 ft. ReSolution has been used to model this type of massive hydraulic fracture treatments in conjunction with water-flooding. The main objective of this study was to determine the sensitivities to the parameters characterizing this type of treatment.
 
 

This sketch  shows the domain used to simulate the reservoir with some of the boundary conditions. The fracture is assumed to be symmetric with respect to a plane containing the well and orthogonal to the plane of minimum in-situ  stresses on which the fracture is growing.
 

Contained fracture

When the in-situ stress contrast is large enough the fracture remains contained.

Fracture fronts at different times and the grid used for flow simulation inside the fracture, note the in situ stress contrast on the right side of these plots. Computed fracture width.
Saturation isosurfaces and Pressure isosurfaces in the reservoir model.
 

Non contained fracture

Under non-favarable in-situ stress contrasts,  fractures can grow vertically.

Fracture fronts at different times and the grid used for flow simulation inside the fracture.
 

Conclusion

Numerical results indicate that stable fractures are possible under field conditions found during water-flood induced fractures in  Dan Field. This is a fundamental difference between conventional simulators based on Carter’s leak-off model and the current fracture-reservoir coupling approach. This is a clear indication of the importance of coupling reservoir simulation with hydraulic fracture simulation for very long fractures.

Among factor having a strong influence on the fracture growth are: the relative permeability curves of the rock, the effective permeability of the reservoir, the injection rate, the toughness of the rock, and the difference between the pressure inside the fracture and the reservoir pressure.

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