METHOD OF BOREHOLE SEISMIC PROSPECTING Russian patent published in 1998 - IPC

FIELD: seismic prospecting. SUBSTANCE: elastic vibrations of drill pipe string are excited by action of drill tool on face of borehole in process of drilling. Three-component recording of vibrations is carried out at different distances of reception points from borehole head, mutual correlation functions are formed. Reception of elastic vibrations on day surface is conducted by radial profiles passing through borehole head by interference systems which parameters are chosen within range of working frequencies from 20 up to 100 Hz in agreement with formulae D = 2v_ap.ref/(f_res1+f_res3) (1), d = v_kmin/(f_res1+f_res3) (2), n = D/d+1(3), where D is length of base of group; d is distance between elements; n is number of elements in group; v_ap.ref is minimal apparent velocity of reflected wave; v_kmin is minimal apparent velocity of waves-interferences; f_res1,f_res3 are first and third resonance frequencies of recorded quasi-harmonic vibrations. Mutual correlation functions of recorded wave field are formed, spectral analysis is executed , quasi-harmonic components of most intensive resonance frequencies are isolated and monochromatic correlograms are formed per each of them. Then they are transformed into pulse form by which structure and physical properties of studied medium close to borehole are determined. EFFECT: improved authenticity of method. 3 dwg