Synthetics

Question 1

Zero-incidence Reflection coefficients

Answer 1

R(0) = (rho2Vp2-rho1Vp1)/(rho2Vp2 +rho1Vp1)

Question 2

SEG POLARITY

Answer 2

reflectivity => positive => peak positif => number in data base negatif = > HARD KICK

Question 3

EUROPEENE POLARITY

Answer 3

reflectivity => positive => peak negatif => number in data base negatif = > HARD KICK

Question 4

Purposes synthetics

Answer 4

• Derivation of acoustic nature of geologically important markers/interfaces given the ambient wavelet
• Enable correlation well results with surface seismic
• Possibly derive transfer/seismic wavelet from well to seismic matching

Question 5

Calculation synthetic seismogram

Answer 5

• Multiply reliable sonic log
• With reliable density log and
• Differentiate to reflection coefficients, the unfiltered synthetic (primary reflectogram).
• Convert from depth to time
• Filter to seismic bandwidth or convolve with seismic wavelet

Question 6

Good practices - synthetics

Answer 6

• If density data are missing -> try to make synthetic from sonic alone
• If sonic data are missing -> do not waste time & efforts
• Never “calculate” missing log values over larger intervals –
it does not add information
• Filter the unfiltered synthetic with a passband that is slightly broader than that of the ambient seismic wavelet
• Use different passbands for objectives at –significantly - different depths
• Be critical in judging the matches