Microfracture Test Research Articles

Fracture toughness of sintered SiC ceramics: a comparison between different methods

In the present study the fracture toughness K lc is evaluated by three- and four-point bending tests on straight-notched bending bars, by three-point bending tests using chevron-notched specimens, and by the indentation microfracture method. The influence of the crack growth rate on the fracture toughness at room temperature is examined experimentally. As a results, K lc tests on chevron-notched specimens are shown to yield a lower value of fracture toughness with a much better reproducibility than tests on straight-notched specimens. Fracture toughness evaluated in indentation microfracture tests is shown to depend on the method of measuring thhe crack lenght. Moreover, the load dependence of the apparent fracture toughness and the large nnumber of different formulae available were further difficulties in evaluating valid K c values from indentation tests. Three-point bending tests of chevron specimens showed a slight increase of K lc with higher crack growth rates at room temperature. The critical strain energy release rate G lc was evaluated from bending tests with chevron-notched specimens as an energetical fracture parameter. It was compared with the conventional fracture parameter K lc .

Microfrac tests optimize frac jobs : Kuhlman, R D Oil Gas JV88, N4, 22 Jan 1990, P45–49

This paper discusses how microfracture testing is providing operators with data for optimizing fracture treatments and determining the placement of wells. This type of testing has increased during the last 5 years because operators can obtain actual stress magnitudes in various zones and the fracture azimuth direction. Entire multiple-well programs have been planned around this testing.

Fracture Height Prediction

Developpement d'une methode en trois etapes pour estimer la hauteur de la fracture realisee en recuperation asisstee par fracturation hydraulique. Cette methode consiste a utiliser les vitesses des ondes de cisaillement et de compression pour calculer les proprietes elastiques de la roche, a calculer la contrainte horizontale minimale de la roche a partir des donnees d'elasticite, de pression des pores, des contraintes tectoniques etc…, et a utiliser un modele de mecanique de la rupture lineaire pour estimer la croissance en longueur de la fracture au cours du traitement de fracturation hydraulique

An experimental study of thermally induced microfracturing and its relation to volcanic seismicity

Thermoelastic seismic-energy release as source mechanism for volcanic earthquakes, describing thermal microfracture tests