Seimic resolution and time-to-depth conversion by the common-reflection-surface (CRS) method / Resolução sismica e conversão tempo-profundidade, atraves do metodo de superficie comum de reflexão (CRS)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The demand for large multiplicities in seismic processing has always been a tough target for the professionals involved in this area. Until recently, the major effort to meet this demand has been done during seismic acquisition, which, due to high cost, is not usually implemented. Recently, the Common Reflection Surface (CRS) technique filled this gap providing greater multiplicity on the expense of more intensive computation, when compared with conventional procedures. Besides a greater multiplicity, the CRS technique enables the improvement of the vertical resolution through the CRS stack. This improvement is achieved by means of increasing a specific frequency which we call "critical frequency". At the critical frequency, the signal-to-noise rate is equal to one (s=n = 1). Once the critical frequency is increased, the frequency spectrum can be flattened by usual techniques. In this thesis, we quantify the improvement of the critical frequency as a function of increasing multiplicity and show why only techniques that allow for high multiplicities can achieve this improvement. We will also show that the gain obtained through this procedure is worth the effort. As it is well known in the geophysical literature, the use of the CRS method provides some parameters (usually called CRS parameters) that provide useful information on the seismic propagation involved. Here we show how this information can be optimally used for imaging purposes through the concept of "geometric maps". We show how to generate these maps, as well as, a few "products" derived from them, such as time migrated velocity field, pre-stack time migration using a short operator, real diffraction apex mapping, a true amplitude zero offset section and the conversion of that section to depth using the normal ray. Next, we show that, even in the presence of discontinuity, we can collapse the real diffractions that are present in the data and, furthermore, to construct true-amplitudes panels in depth. Finally, we use the geometric maps to study the effect of the CRS stack on the seismic lateral resolution, especially on the vicinity of discontinuities

ASSUNTO(S)

geofisica geophysics

ACESSO AO ARTIGO

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