Patent ID: 8544552

Claim:
Tool having an operational capability to superimpose pulses onto a pressurized stream of fluid being injected into a ground formation, wherein: the tool includes a pulse-valve, having a pulse-valve-member that is movable between a valve-closed position and a valve-open position; the tool includes an accumulator, in which fluid is stored at accumulator-pressure; the tool includes a piston, which is connected to the pulse-valve-member; the tool includes an area-divider, relative to which the piston is movable between a contact-position and a clear-position; the piston has an accumulator-surface and an opposed formation-surface, and the tool is so structured that, the pulse-valve being open: (a) accumulator-pressure acting on the accumulator-surface urges the piston to its clear-position; and (b) formation-pressure acting on the formation-surface urges the piston to its contact-position; the tool includes structure that exerts a biassing-force on the piston in the direction to urge the piston towards the contact-position; the tool is so structured that, the piston being in the contact-position: (a) the accumulator-surface of the piston now makes sealing contact with the area-divider, thereby creating a divider-seal; (b) the divider-seal sealingly divides the area of the accumulator-surface of the piston into two sub-areas, being area-A and area-B; (c) the divider-seal, and the tool as a whole, are so structured as to enable the pressure to which area-A is exposed to be substantially different from the pressure to which area-B is exposed; (d) only area-A of the accumulator-surface , and not area-B, is exposed to accumulator-pressure; (e) when the pressure differential between accumulator-pressure and formation-pressure (PDAF) exceeds an upper trigger level, forces on the piston due to the PDAF acting over the area-A now exceed the biassing-force on the piston, whereby the piston now moves clear of the area-divider, towards the clear-position; the tool is so structured that, the piston being in the clear-position: (a) area-A and area-B are not now sealingly separated by the area-divider, but are now connected; (b) whereby the accumulator-pressure now suddenly acts over the sum of area-A and area-B together; (c) whereupon the piston now is subjected to a sudden force of sufficient magnitude to move the piston and to move the valve-member to the valve-open position.