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Learning of an energy absorption of seismic transients

            As it is known, propagation of pressure waves to real environments is tracked by reduction of amplitude and energy of the surge, linked generally with two factors: with a discrepancy of energy of a surge on front and with a surge energy absorption in bulk of environment. Occluding is understood as the power loss of a surge linked to transferring in thermal energy. In real (granulated and laminated) environments, besides 'pure' occluding, essential influencing on energy of a seismic impulse such factors as render reflexes and interceptions on boundary surfaces of beds, dissipation on small discontinuities. Thus, at the analysis of reduction of amplitudes (after the account of a geometrical discrepancy of a surge) we learn total affecting of the pointed factors, separation among which one 'pure' occluding is a challenge [3].
Quantitative measure of functional connection of reduction of amplitudes of a pressure wave with spacing interval (at VSP with depth) is the effective attenuation coefficient (occludes)[2, 4]:

CSP-logging

 

 

 

 

 

 

 

 

 

 

 

 

 

P/S profiles

 

 

 

 

 

 

 

 

 

 

 

 

                   ln (А0/Аx)
αeff. = ________________  ,[2,4]
                          x

Where А0 – amplitude oscillations in some (basic) point,
      Аx – amplitude oscillations apart x from this point.
           
            On fig. 4.15 diagrammes of the given amplitudes and effective decay factors of a direct longitudinal wave of R.Ispolzovanie of this wave for calculation αeff are shown. Is preferable as it is registered on an interval representing practical interest vertical a lateral view on absolutely quiet background.
            On a drawing of amplitudes of Аp=f(H) it is possible to see the smooth decrease of amplitudes of this wave with the depth which background is complicated by inappreciable variations of values of Ar in those and other legs from middle lines. Adequate, but with a return sign, the behaviour of signal attenuation of Ar with depth is observed and on a drawing of effective decay factors (fig. 4.15). At the analysis of diagrammes it is possible to pay attention only to two intervals which are somehow correlated with features of a geological slit. The first interval between depths 1380-1480m which is scored decreased by Ar and magnifications αp, well is compared with clay a slit in bottoms pokuskaya assise (in particular with development clay Koshay assise), on what in the blanket are specified by curve PS. The second interval between depth a 2500m-face of the chink including adjournment of bottoms of the Tyumen assise and fractured of breed surface of a part of the base is mapped on diagrammes by the raised frequency of variations of Ar and αp. I.e. Some communication with features of a geological slit is here too scored.
            With a lithology composition of a slit we do not find in other intervals of a slit of any communication of analyzed dynamic parametres.

On fig. 4.15 diagrammes of App =f(H) and αpp, calculated on reflected mode are given. On these diagrammes, as appears from drawing viewing, some blanket tendency of their opposite behaviour in relation to incident wave diagrammes is scored. Unlike the last on them the considerable variations of values of Arr and αpp are observed that we relate to burdening by their serious errors caused by incomplete inhibition of noises imposed on reflected modes. For interpretation they are not suitable. A priori it is possible to assert that any additional, at least, they do not bear essentially important information..

Geoacoustic model of dynamic parametres (Factors of attenuation and amplitudes) The falling and reflected longitudinal waves

 

 

 

 

 

 

 

 

 

 

 

 

 

Estimate of accuracy of definition of averages and layer velocities

At an estimate of accuracy of evaluation of averages and layer velocities the error of measuring of time as small on quantity casual errors in depth do not play an essential role is usually taken into consideration only. If mt – an error of individual measuring of time the error in mean velocity definition is counted under the formula:                      
mv = ±  V2  *mt
                     H
At satisfactory quality of acoustics logging the maximum inaccuracy in time measuring, calculated on audit observations, compounds 0.002 with.
At rather slow ascending of velocity with depth and under condition of an invariable error mt inaccuracy in velocity mv is diminished in process of depth magnification. In tab. 4.1, 4.3 values of inaccuracies in mean velocity definition (for longitudinal and cross surges) on various depth intervals are resulted.
The mean-square error in definition of values of layer velocities paid off under the formula:   
mvla. = ± Vla2 * m/ΔН