Abstract. Drilling fluid infiltration during well drilling may induce pore pressure and
strain perturbations in neighbored reservoir formations. In this study, we
report that such small strain changes (∼20 µε) have
been in situ monitored using fiber-optic distributed strain sensing (DSS) in
two observation wells with different distances (approximately 3 and
9 m) from the new drilled wellbore in a shallow water aquifer. The
results show the layered pattern of the drilling-induced hydromechanical
deformation. The pattern could be indicative of (1) fluid pressure
diffusion through each zone with distinct permeabilities or (2) the
heterogeneous formation damage caused by the mud filter cakes during the
drilling. A coupled hydromechanical model is used to interpret the two
possibilities. The DSS method could be deployed in similar applications such
as geophysical well testing with fluid injection (or extraction) and in
studying reservoir fluid flow behavior with hydromechanical responses. The
DSS method would be useful for understanding reservoir pressure communication,
determining the zones for fluid productions or injection (e.g., for
CO2 storage), and optimizing reservoir management and utilization.
In situ hydromechanical responses during well drilling recorded by fiber-optic distributed strain sensing
