ESTIMATION OF SEISMIC ATTENUATION IN THE KANGAN FORMATION FROM WALKAWAY VSP DATA

摘要

In this paper we use the geometry of walkaway vertical seismic profiling (WVSP) in order to define seismic wave attenuation trends in the Kangan reservoir sequences of the South Pars oil field. The mean relative-amplitude attenuation values are analyzed as a function of geophone-source offsets. Our purpose is determining locations in which attenuation shows excessive amounts, that would indicate the possibility if there was any location where there was excessive energy attenuation, that would indicate the possibility of an overpressure zone that would be a drilling hazard. The amplitudes in one walkaway VSP survey line were evaluated to observe any main variation of amplitude in different offsets and to estimate the attenuation of seismic waves energy. Downgoing first arrivals were separated by applying a time window after flattening along a targeted horizon and then performing Fast Fourier Transform (FFT) on first arrivals.In WVSP data acquisition, seismic waves propagate through the geological layers via different source-receiver offsets to reach a constant-geophone depth in subsurface. By processing the amplitudes of these waves, The amounts of attenuation is measured and the lost energy is estimated.