Resources and articles
In a 2015 Swedish article, the authors explain that, to achieve good drilling performance in crystalline rocks such as granite, it is essential to target an area with continuous fractures. Our methodology is designed precisely for that purpose: to identify cracks and fractures in the rock. Using this approach, we have successfully located several deep wells in granite formations around the world.
Here is the link to the full article:
"The Swedish bedrock generally offers good potential for groundwater extraction from rock-drilled wells, primarily for private water supply (SGU 2008). However, extraction capacity may be limited at the local level. According to Banks et al. (1996), the success of well drilling depends on finding an aquifer fracture that connects to a larger, continuous fracture network. To optimize the potential for good well yield, drilling should not be limited to vertical wells; rather, the well orientation (inclination and azimuth) must take into account local geological conditions—such as foliation orientation (plastic anisotropy), potential rock contacts, existing fracture zones, etc.—so as to access the maximum number of fractures. Furthermore, if data are available, the orientation of the predominant local stress field should be taken into account (Banks et al. 1994, 1996).
The yield of a newly drilled well in crystalline rock is typically 100 to 1,000 l/h. However, if a larger fracture zone is encountered, the water supply can be considerably higher. In Late Precambrian and Phanerozoic sedimentary rocks, yields exceeding 10,000 l/h are not uncommon, but 100 l/h is usually sufficient for a typical household (SGU 2008)."