We have conducted laboratory tests to investigate the containment of hydraulic fractures in unconsolidated, layered formations. We varied both permeability and strength of the layers in the samples. The fracture evolution was observed with X-Ray CT scanning and by excavating the sample after the test.

We found that permeability is the dominant factor in containment, if the stress contrast is small. With a factor of three to four between the permeability of the two layers there is a strong tendency for the fracture to propagate in the low permeability layer. Difference in strength is much less important for containment.

A numerical fracture propagation model described the sand as an elasto-plastic material with parameters obtained from triaxial tests and used a simplified leak-off description of the cross-linked gel. The results agree qualitatively with the tests.

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