ABSTRACT

Crack initiation and propagation is a three-dimensional process. Most of the analytical solutions (such as PKN and KGD models) and numerical models treat crack propagation as a two-dimensional (2D) process. Yet, there is no experimental study, which can provide a one to one comparison in 2D to validate these kinds of models. The 2D experimental set-up equipped with a high-speed camera provides continuous video record and measurement of fracture path. A Speckle Pattern is applied in order to accurately measure surface deformation with Digital Image Correlation (DIC). A transparent material is used in order to have a direct viewing of fracture growth. The results provide information about the breakdown pressure, fracture growth direction, width and fracture speed.

INTRODUCTION

Hydraulic fracturing has been used in different applications since 1950. There are still many open questions and uncertainties related to hydraulic fracturing. Observing the fracture geometry in field treatments is almost impossible, except in special tests with extensive seismic monitoring (Abe et al., 1983; Vinegar et al., 1992), even in those cases it is believed (de Pater et al., 1994) the data interpretation needs to be more developed. To better understand the behavior of rock during a hydraulic fracturing treatment, numerous studies have been undertaken and several physical models developed to investigate rock behavior during the injection. Laboratory tests should, therefore, serve as benchmarks for numerical simulations.

In this study, an innovative two-dimensional set-up is introduced for conducting hydraulic fracturing on low-strength rock-like materials.

1. BACKGROUND

There are three different approaches for simulating crack propagation.

  1. Analytical,

  2. Numerical and

  3. physical models are introduced and related literature are summarized.

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