| 摘要 |
A downhole seismic signal source (vibrational or impulsive) capable of producing a signal of sufficiently high energy to permit the tool to be used in a deep wellbore (exceeding 4000 feet). A piston rod having two pistons reciprocates in an elongated cylindrical housing. An electrohydraulic valve controls the flow of hydraulic fluid to opposite sides of a first piston to control the piston rod's vertical movement. The second piston is positioned between a fluidic spring which balances the pressure of the wellbore fluid and a reservoir of hydraulic fluid which inflates a flexible bladder to produce the seismic signal in the wellbore fluid.
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