The Interaction of Hydraulic Fractures with Natural Fractures: An Experimental View
Jon E. Olson
Petroleum and Geosystems Engineering, University of Texas at Austin
ABSTRACT: The incredible increase in oil and gas production in the United States can be largely attributed to the application of horizontal wells and hydraulic fracturing to organic-rich shales. One aspect of the hydraulic fracturing in these formations that seems unique is the apparent complexity of the induced fracture propagation. Some of this complexity has been attributed to the intersection and diversion of the hydraulic fracture by pre-existing natural fractures and faults. We investigated the attributes that control failure for calcite cemented veins in subsurface core samples of Marcellus shale using the Semi-Circular Bend Test. Experimental results show that the approach angle of the propagating fracture relative to the vein has a strong influence on whether the fracture-fracture interaction results in crossing or diversion. The likelihood of diversion can be explained using the Energy Release Rate criterion. Other parameters that were investigated include the vein thickness, fracture toughness and Young’s modulus. Numerical modeling work is underway to probe a wider range of parameters than is possible with physical samples. This work is utilizing the Distinct Element Method code PFC3D.
