ABSTRACT: Hydrocarbon recovery is potentially maximized with an open, complex fracture network of large surface area to volume ratio that penetrates the reservoir. We study the hydraulic rupture of a solid, homogenous cube of Polymethyl methacrylate (PMMA) containing model boreholes as an analog to hydraulic fracturing with various fracture-driving fluids. The transparency of PMMA allows for the visualization of fracture propagation using high-speed video. The cubes are constrained by prescribed triaxial far-field stresses with the borehole-parallel stress set to zero. The cube is ruptured by overpressuring the borehole at controlled rates with fluids present as both liquids and gases pre- and syn- failure. We measure the fracture breakdown pressure, rates of fracture propagation and the physical characteristics of the resulting fractures and how they vary between fluid types. Further research extends these experimental methods to bluestone and granite, with additional tests that determine the permeability of these materials and its effect on creating a complex fracture network.
1. INTRODUCTION To increase hydrocarbon recovery in the subsurface, it is desirable to produce fractures with high surface area to release the maximal amount of naturally stored oil and gas. The larger the surface area created by fractures in a finite space, the higher the potential of the system to recover hydrocarbons, because more flow channels are produced. Such a system is called an open, complex hydraulic fracture network. We investigate the creation of an open complex fracture network via laboratory experiments using a range of fracturing fluids and stress conditions. In this paper, we focus on fracture within homogenous samples, to better understand how complex networks initially develop. Once a baseline of data of fracture pressure per fluid has been made, the initial conditions can be manipulated for future experiments to create fractures of increased surface area.