2017


Jun
20 - 22

EUROCK 2017

Ostrava, Czech Republic

9:00 AM - 5:00 PM

Human activity in Rock Masses

Join Golder at the 2017 ISRM European Rock Mechanics Symposium (EUROCK 2017) in Ostrava, Czech Republic, on June 19-22, 2017

This Symposium is organized by the Institute of Geonics of the Czech Academy of Sciences and the Czech National Group of the ISRM. Listen to keynote lectures by some of the world’s leading experts on rock mechanics. Three short workshops will also take place and visits to different attractive mine and civil engineering works.

Golder's Marton Farkas, Geophysicist from our Hungarian office in Budapest will attend and have a stage presentation on "Interpreting multistage minifrac tests using discrete element modeling of foliated rock with various drilling mud properties".

A short summary of the presentation  

Multistage mini hydraulic fracturing tests were performed in a borehole located in central Hungary in order to determine in-situ stress. At depth of about 500 to 560 meters, observed pressure versus time curve in metamorphic rock (mica schist) show a typical results. After each pressurization cycle, the fracture breakdown pressure in the first fracturing cycle is lower than the reopening pressures in the subsequent reopening and step-rate phases. It is assumed that the composition of the drilling mud and observed foliation of the mica schist have a significant influence on the pressure values.

In order to investigate this problem, numerical modeling was performed using the discrete element code (ITASCA Particle Flow Code, PFC), which has been proven as an effective tool to investigate rock engineering problems associated with hydraulic fracturing. The code presented in this study enables simulating hydro-mechanically coupled fluid flow in crystalline rock with low porosity and pre-existing fractures (represented by the smooth joint contact model in PFC) in two dimensions. In this study, the sensitivity of the effect of foliation angle and fluid viscosity on the peak pressure is tested.

The anomalous characteristics of the pressure behavior are interpreted in that way that the drilling mud penetrates the sub-horizontal foliation plane, it clogs the plane of weakness and makes the opened fracture tight. Eventually, the process prevents leak-off from the opened fracture that might explain the increased fracture reopening pressure in subsequent cycles.

Golder contact:
Fredrik Hellner, Marketing Coordinator (Stockholm office)
+46 8 506 306 93
fredrik_hellner@golder.com

Find out more on EUROCK 2017 website

EUROCK2017