Abstract: For seismic monitoring of a petroleum deposit at least one signal receiving unit is fixed to an outside of a casing pipe before the casing plate is cemented in a borehole passing through the monitored zone.At least one housing, defined by projecting elements, (longitudinal members, stops), is provided along an outer surface of the casing pipe, with the where the reception unit being embedded and fixed therein so as to protect the reception unit from shocks or compressive forces which may occur during lowering of the pipe into the well. Each reception unit comprises a support assembly with cavities for sensors, electronic cards for amplifying the signals delivered by the sensors and a sealed external case which is easy to position and which is held firmly in position by embedment in the housing. A multiconductor cable is used, for example, for connecting the reception unit to the surface.

Abstract: A soft retaining gripper for gripping a surface while stresses are exerted in a longitudinal direction parallel to the surface between the gripper and the surface, comprises a jaw and an inflatable flexible bladder carried by the jaw, the bladder being in use inflated to grip the surface. To prevent creep of the gripper in use, a wall is associated with the bladder and extends between the bladder and the surface, the wall being made of a composite anisotropic material comprising elongate elements which are oriented to extend in the longitudinal direction and are practically inextensible and a flexible synthetic resin in which the elongate elements are embedded, the elongate elements being anchored to the jaw at at least that end in the direction of which creep might otherwise occur.