Development of a geophysical methodology from boreholes for the study of radioactive waste repositories in granit formations

Within the frame of a 2-year contract with the C.E.C., dealing with storage and disposal of radioactive wastes in geological formations the B.R.G.M. has been involved in a research on the detection of fracturation from boreholes by geophysical methods. Various geometrical arrays (mono-hole, cross-hole, hole-to-surface) concerning mainly electrical methods, have been used in the field on granitic rocks, and interpreted according to three dimensional earth-models. Conductive or resistivite parallelepipedic inhomogeneities embedded in stratified or homogeneous half-spaces, have been taken into account in this three dimensional modelling. The influence of the various geometrical and electrical parameters of the inhomogeneities for different electrical arrays has been studied. Advantages and drawbacks of these arrays for the detection of the fracturation from boreholes, can be thus derived. An analysis of the calculation and drawing routines gives way to possible future improvements especially for modelling