Abstract:

The carbonate reservoirs of the Middle and Lower Ordovician in southern Tahe oilfield are mainly of fractured-vuggy type featured in effective fractures and rugs formed by dissolution.The distribution of fractures in these reservoirs is controlled by faults,the oil layers are thin,and water bodies are active.The fracture-rug combinations are of different scales,irregular spatial distributions,and various filling properties.In view of the characteristics of the fractured-vuggy carbonate reservoirs in the study area,two techniques are presented,namely the pre-staek anisotropy analysis technology for detecting the intensity and azimuth of fractures and the pre-stack elastic parameter inversion method for predicting,in combination with log data,the growth of the fractured-vuggy zones and fluid-bearing indicators.The application of the techniques in southern Tahe oilfield reveals that the prediction results are basically consistent with data gathered from the known fractured-vuggy reservoirs and drilling data.The application of these two techniques has improved the prediction of spatial distribution of smallscale fractured-vuggy reservoirs and also shows that there are several favorable fraetured-vuggy zones distributed in the southern Tahe oilfield.

Key words: azimuthal anisotropy, pre-stack elastic parameter inversion, physical modeling, fractured-vuggy carbonate reservoir, reservoir prediction, Tahe oilfield