Abstract: An assembly is provided that includes an oilwell rig; a sheave wheel adapter connected to the rig; a sheave wheel yoke connected to the adapter; and a sheave wheel connected to the yoke. In various embodiments of the invention, this assembly is configured to permit the wheel to rotate about three mutually perpendicular planes of motion.

Abstract: An apparatus for generating a seismic signal in a wellbore includes an elongated housing configured to be disposed in the wellbore; a piston slidably disposed in an internal bore in the elongated housing; a strike plate fixed on the elongated housing proximate one end of the internal bore; and an energizing mechanism configured to move the piston to hit the strike plate. A downhole system for seismic survey of a formation penetrated by a wellbore includes at least one seismic receiver; a seismic source; and at least one inflatable packer configured to separate the seismic source and the at least one seismic receiver in different compartments in the wellbore when inflated.