Simulating Non-Stationary Seismic Facies Distribution in a Prograding Shelf Environment

A dense array of high-resolution seismic profiles of the underwater Rhone River deltain the Mediterranean Sea is used as the only input for developing a stochastic model of an analogue of anoil reservoir in a prograding shelf environment. The topographic elevations of the unit boundaries arefirst estimated from the seismic profile sections. The geometry of the envelopes of the seven identifiedstratigraphic units is then estimated by non-stationary geostatistics, after the inference of theirgeneralized covariance by the method of increments. A complete “3D architectural model” is thenproduced by filling the envelopes of the previously estimated sedimentary units with internal faciesdistributions. These facies are first defined by their seismic signature, based on their reflectionconfiguration, continuity and amplitude. The HERESIM geostatistical software is used in a nonstationarymode to analyse and simulate the vertical and the horizontal facies variability. The verticalvariability is quantified for each unit by a vertical proportion curve. The horizontal variability isanalysed by the horizontal facies variograms which measure the autocorrelation of a given facies as afunction of the distance. The remaining model parameters are adjusted to give an optimum match of themodel to the observed seismic data. The model results are used to interpret the deposition, erosion andtectonic mechanisms that have shaped this shelf environment.