Self-organizing maps with cokriging porosity applied to sand-shale reservoirs using seismic

Abstract

We selected seismograms from a 3D seismic survey acquired at the Waggoner Ranch, Texas to characterize the distribution of porosities in each lithofacie. Porosity images were obtained using cokriging and the facies using the Self-Organizing Map (SOM) technique. The reservoir geology is a sand and shale sequence with small amounts of limestone as markers. The SOM uses reflection attributes that are able to capture the three geological units. The seismic lines are first converted to impedance and then with the help of the porosity and impedance logs are transformed to porosity images using geostatistics. We compute vertical and horizontal variograms as well as cross variograms of the soft (impedance) and hard data (porosity logs). The SOM image correlates with the lithological units and the seismic reflection lines as well. The SOM image identifies the sedimentary structure of the shale and sands, and the porosity image provides the distribution of porosity in the specific sand and shale units of the reservoir.