Physical Basis for the Use of Reflected Wave forms for Studying Groups of Thin Beds
At present, considerable thought is being given to the study of reflections caused by groups of thin beds. Electric and acoustic well logs described earlier in this collection have shown that the occurrence of thin-bedded sequences is common. The bed thickness may be comparable to the lengths of the waves travelling through them in some cases, or considerably longer or shorter in other cases. In view of this, there is both scientific and practical interest in the study of wave propagation in groups of layers with varying thickness. The study of groups of layers with varying thickness is of particular practical importance in the exploration for and development of oil and gas reserves, which occur preferentially in the permeable beds. The greater part of oil and gas reserves is associated with sequences of detrital rocks, occurring at various depths below the surface (for example, the fields on the Russian platform, in the Krasnodar Belt, and others). The detrital rocks in which oil and gas occur are alternating beds of sandy and shaly facies (siltstones and shales). From the seismologists’ point of view, such rocks may be represented as sequences of periodically alternating beds with nearly the same velocity profile in them. In the present paper, we will examine a seismic representation which approximates a real sequence of detrital rocks and study the dynamic wave properties (the wave form) for waves reflected from such sequences which vary in thickness. This is done using data from theoretical studies.
KeywordsWave Speed Wave Form Periodic Sequence Synthetic Seismogram Moderate Thickness
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