Impulsive suction pulse generator for borehole

Abstract

Suction pressure pulses are generated within a borehole by closing a valve that interrupts the flow of a drilling fluid (e.g., drilling mud) circulating through one or more high velocity flow courses within the borehole. In one embodiment in which the suction pressure pulses are applied to improve the efficiency of a drilling bit, the valve interrupts the flow of drilling mud directed through the bit and thus through high velocity flow course(s) disposed downstream of the bit. Arresting flow of the drilling mud through the high velocity flow course(s) generates suction pressure pulses of substantial magnitude over a face of the drill bit. The suction pressure pulses provide a sufficient differential pressure that weakens the rock through which the drill bit is advancing and also increase the force with which the drill bit is being advanced toward the rock at the bottom of the borehole. However, the flow of drilling mud into an inlet port of the valve is not interrupted, so that fluid motors can still be used to rotate the drill bit. When the valve is closed, the drilling mud continues to flow into the valve and subsequently flows back into the borehole. The suction pressure pulses can also be applied to a short section of the borehole wall to produce seismic pulses, or to provide remediation of formation damage (by drawing fines from the wall of a borehole to enhance oil and gas production rates), or can be employed for descaling tubes within a borehole.