Seismic expression of carbonate build-up karstification: karst modelling strategies and insights from synthetic seismic

Abstract

Abstract Many ancient carbonate build-ups are impacted by meteoric diagenetic processes, including karstification. However, very little is known about the acoustic properties and seismic expression of karstified reservoirs. This paper investigates potential seismic expressions of karstified build-ups by means of synthetic seismic modelling. The overall stratigraphic architecture and physical properties of rock are derived from published examples of SE Asian carbonate build-ups. Various karst systems, corresponding to distinct stages of karstification of varying intensity, have been superimposed to the background facies-related acoustic model. Three-dimensional synthetic seismic cubes have been computed from the karst-bearing acoustic model and by testing various wavelet frequencies. The proposed approach allowed several types of palaeokarst to be reproduced, from dendritic karst and flank-margin caves to cave networks, in amplitude sections. However, geometrical seismic attributes, like coherency, cannot be accurately reproduced with modelling based on the available literature. In addition, the exploration of this synthetic seismic data shows that non-stratiform diagenetic bodies (i.e. leached carbonate wedges in a mixing zone) appear as stratiform even in very-high-resolution seismic. Thus, their detection and characterization require advanced techniques or prior knowledge, such as borehole data.