초록 ▼

A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well f

A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

대표청구항 ▼

[ What is claimed is:] [1.] A well tool which is lowered into a well containing well fluid which is used for exploration of formations surrounding the well by use of elastic waves comprising at least one elastic wave emission or reception set, a self-contained gas generator provided with a pressure

[ What is claimed is:] [1.] A well tool which is lowered into a well containing well fluid which is used for exploration of formations surrounding the well by use of elastic waves comprising at least one elastic wave emission or reception set, a self-contained gas generator provided with a pressure control and which delivers to the well fluid, on demand, calibrated gas bubbles which attenuate tube waves propagating in the well, an expansion valve which delivers gas at a predetermined overpressure in relation to pressure prevailing in the well at a selected depth, and a porous filter which calibrates dimensions of the calibrated gas bubbles and wherein the gas generator comprises a combustion chamber in which a gas-generating pyrotechnical substance is combusted, and a tank for containing the gas generated by combustion of the pyrotechnical substance.