Physical modeling of seismic responses in thin interbedded reservoirs with horizontal fractures

Oil and gas reservoirs usually contain horizontal fractures that develop along bedding and have a non-negligible effect on reservoir characteristics. When the horizontal fracture is parallel to the bedding, the seismic response of the fracture overlaps with that of the bedding, making it difficult to identify the horizontal crack. In this paper, the physical modelling technology is used to simulate the seismic response of thin interbedded reservoirs with horizontal fractures, thus providing a basis for the seismic identification of such cracks. First, a physical model is constructed by embedding fractured media into uniform strata. The horizontal fractured media are composed of epoxy-bonded fibre sheets and constructed in advance before the construction of the whole physical model. Then the model is put into a water tank, and four 2D seismic data for P-waves are acquired in the water tank. Subsequently, these data are processed and analyzed. Results that horizontal fractures in thin interbedded layers can cause obvious anomalies in the time-frequency spectrum, which are constrained by the tuning effect caused by thin interlayers and fractures. Therefore, both thin layer interpretation and fracture prediction consider such dual effects. For frequency-dependent AVO (Amplitude Variation with Offset), although the frequency-dependence produced by thin interbedded layers play a dominant role, the development of cracks and the variation of crack parameters can cause significant changes in frequency-dependent AVO, which indicates that the frequency-dependent AVO can be used to identify horizontal fractures in thin interbedded reservoirs.