Structural control over well productivity in the Jundiaí River Catchment, Southeastern Brazil.

The well productivity in crystalline terrains is extremely changeable and depends on external factors, in addition to the intrinsic properties of rocks. In the Jundiaí River Catchment, Southeastern Brazil, the main factor that influences well productivity is the existence of open discontinuities permeability in geologic environments that favor groundwater recharge. In that area, Pre-Cambrian shear and fault zones were reactivated throughout geologic time, controlling the morphostructural compartments and the Cenozoic sedimentary deposition. Superposition of productivity data and structural maps showed that more productive wells are concentrated mainly along the regional geologic structures. The structural control over well productivity is also noticeable in detailed scale. Using fine scale maps we show that the most productive wells are located in areas where brittle structures with NW-SE and E-W directions denote the action of neotectonic transtensional stress. The comprehension of evolutionary geologic history allied to fracturing analysis proved to be an efficient and a low cost technique, which is adequate for selecting areas for further developments using more expensive methods.