161 8. Hydro-stratigraphic study of the Hydrogeological Experimental Site of Poitiers, France Occurrence ok karst Fracture inventory Audouin et al. (2008) identified a set of potentially productive fractures through the integration of heat-pulse flowmeter measurements and OPTV borehole imaging. While some of these features reveal the morphology of inclined fractures—as observed in borehole M07—most are interpreted as the result of collapse within karstified horizons and are more accurately described as sedimentary joints. Based on their analysis, the authors concluded that fewer than 3% of the identified fractures appear to be hydraulically conductive. To verify and expand upon these conclusions, a comprehensive review of all OPTV logs of this study was conducted, focusing specifically on the identification of inclined and vertical fractures. These were systematically mapped across the boreholes to assess their spatial distribution and relationship to karstic voids. The results are compiled in Table 2, which lists the depths and apparent apertures of each feature. Only non-horizontal fractures (i.e., vertical and inclined) are included in this dataset; horizontal features, interpreted as bedding planes or sedimentary joints, were excluded from this classification. Table 2 Depth of fractures reported on OPTV logs. Boreholes Fracture typology Open Filled by clay Recrystallised M01 0 1 38.67-39.80 0 M09 6 (36.71-37.70; 60.00-60.84; 66.53-70.13; 71.31-72.25; 72.52-73.73; 84.58-85.49) M10 0 0 0 M14 1 73.25-73.60; 0 1 85.49-85.75 M15(b) 1 47.8-48.8 1 61.4-63.0 0 M17 0 0 1 (43.02-44.19) The total length of all boreholes equals 593 m. Within these 593 meters, only 12 fractures are well identified, which gives a density of 0,02 fractures per meter. This ratio is largely due to M09, with 6 fractures identified. In general, reported fractures are located above the Oolite Formation of the Laeviuscula Biozone and are not present in Aalenian limestones. Only two of them are open and could provide water flow.
RkJQdWJsaXNoZXIy NjA3NzQ=