Patent ID: 8061421
Filing Date: 2011-11-22
Classification: E21B,G01V

Abstract:
1. Apparatus for superimposing a seismic wave onto a flow of liquid being injected into the ground around a borehole, characterised by the following combination of features: the apparatus includes a reservoir for storing, under pressure, the liquid to be injected into the ground; the apparatus includes a downhole-structure, which is suitable for lowering down into the borehole; the downhole-structure has an overall-circumference, being the circumference that circumscribes all portions of the down-hole structure, the overall-circumference measures OC cm in length, measured in a plane at right angles to the axis of the borehole; the downhole-structure includes a valve, comprising a valve-face on a valve-member, and a valve-seat which is movable relative to the valve-member; the valve is operable between a closed condition and a full-open condition; in the full-open condition, the valve-face lies separated from the valve-seat and lies spaced therefrom by a valve-gap; in the closed condition, the valve-face and the valve-seat make sealing contact over an annular contact-area; a valve-gap-seal-contact-line is defined as the locus of the mid-point of the said annular contact-area at each radius around the valve-gap-seal-contact-line; the valve-gap-seal-contact-line has a valve-gap-seal-circumference that measures VGSC cm; and VGSC is larger than seventy-five percent of OC.