Application of 3D-Seismic Data in Detecting Buried Karsts in Asmari Formation: An Example from Kupal Oil Field, Southwest Iran

Detecting karstification processes in hydrocarbon carbonate reservoirs is important because of their porosity, permeability and also the risk associated with their drilling. A very useful technique to locate buried karsts is 3D seismic. In this research, seismic frequency decomposition (spectral decomposition) and seismic inversion techniques used to identify these sub-surface diagenetic features that control quality of the Asmari reservoir of the Kupal oil field. The results point to numerous buried karstified features in the upper Asmari which can be regarded as the main targets for reservoir development. According to seismic inversion, the karstic interval (mainly channel) have lower seismic acoustic impedance, and at the same time higher effective porosity. Also, numerous geological evidence such as drilling fluid loss, tidal and supratidal facies, as well as the development of fenestrate porosity, vuggy and extended vuggy porosity in the upper Asmari, all point to the meteoric diagenesis and subaerial exposure. These confirm the likelihood for paleokarsts occurrence in this part of the Asmari Formation. Therefore, the results of this research can be very useful in designing new wells in order to increase the production rate, reduce the risk and cost, when drilling new wells in the Asmari reservoir of this oil field.