Abstract: A system and method for performing seismic prospecting and monitoring during drilling of a well are disclosed. The system generates energy, such as acoustic vibrations and electromagnetic energy, at a downhole location and imparts the same into the surrounding earth. The energy may be imparted by the drilling operation itself, or may be generated by a downhole apparatus. Downhole sensors are provided which sense the energy after it has passed through the earth surrounding the wellbore. The sensed energy is either communicated to the surface, or is communicated to a downhole computer for analysis, with the results of the analysis communicated to the surface. Due to the use of both downhole generation and sensing of the energy, high frequency energy may be used. As a result, the resolution of the resulting survey is improved over techniques which utilize surface detectors for energy traveling through the earth.

Abstract: An expandable ignition chamber within an upstanding cylinder is formed between its base and a massive free piston. Initial detonation of a combustible gas mixture within the chamber drives the piston upwardly to expose in sequence a series of vertically spaced gas inlets in the cylinder wall, through which the supply of gas is replenished to support a corresponding sequence of additional rapidly timed detonations. Repetitive seismic pulses are thereby supplied by the downward thrust of the base which is itself slidable with respect to the cylinder walls.