In-situ stress measurements by hydraulic fracturing method at Gotvand Dam site, Iran

A set of hydraulic fracturing tests were conducted for determining in situ stresses in 10 inclined and vertical boreholes ranging in depth from 30 to 100 m at locations of hydropower plant tunnels of the Gotvand Dam site in the southwest of Iran. The rock in the studied area is formed by the sequence of sandstone, clay stone, and mudstone layers of the Aghajari (AJ) formation, and by thick conglomerate layers of the Bakhtiari (BK) formation. Note that the AJ formation is located underneath the BK formation. The in situ tests were carried out by using conventional systems with special high pressure rods and straddle packer tools. The tests were conducted both in fractured and intact rocks. The measurements yielded an orientation of the maximum horizontal stress of N 30° ± 5° (NE-SW), which is generally the same as directions indicated by focal mechanisms solutions from earthquakes and fault conditions in the location of the area studied. © TÜBITAK.