| 摘要 |
<p>For injecting e.g water into ground formation around a borehole, and for superimposing pulses onto the outflow of the injected water, it is important that the puses have a rapid rise-time. A piston is connected to a pulse-valve of the tool. A bias spring urges the piston towards its closed position. The piston is urged towards the open position by a differential PDAF between the supplied accumulator-pressure and the in-ground formation-pressure. When the pulse-valve is open, the PDAF is falling, until the force of the spring closes the pulse-valve. Then the PDAF rises, but now the PDAF acts over only a small area of the piston. When the PDAF is high enough to ease the pulse-valve open, suddenly the whole area of the piston is exposed to the PDAF, whereby the pulse-valve opens violently.</p> |
