Effects of Drilling-Induced Disturbance to estimate Reservoir Compaction through Radioactive Marker Technique

In-situ measurements of reservoir compaction through Radioactive Marker Techniques are here discussed. This study evaluates the effect of well casing on the deformation measured in the vicinity of the borehole, with respect to the actual reservoir deformation to which the formation is subjected at larger radial distance, where the formation is likely to be undisturbed. It is here proved that the presence of a fully cased hole generates perturbations of the deformations in a large area surrounding the borehole, even accepting an elastic behavior of the rocks. Additionally, elasto-plasticity has been taken into account to further highlight the phenomenon. In particular, the deformation around a cased hole has been found to be much lesser than the one of the undisturbed formation. These effects are evident in the close vicinity of the borehole (where the radioactive markers are implanted), and are amplified in the case of loose or unconsolidated formations characterized by a rigidity much lesser than the one of the cased hole. The numerical investigations have been obtained through a fully coupled numerical code, here adopted for performing analyses of reservoir deformations and drilling-induced formation disturbance.