Prediction of 3-D fluid permeability and mudstone distributions from ground-penetrating radar (GPR) attributes: Example from the Cretaceous Ferron Sandstone Member, east-central Utah

A 3-D fluid permeability distribution is estimated inside a channel sandstone reservoir analog in the Cretaceous Ferron Sandstone fluvio-deltaic complex in east-central Utah from ground-penetrating radar (GPR) attributes. Fluid permeability measurements at 5 cm spacing along four boreholes and one pseudohole section at the adjacent cliff face are used together with instantaneous amplitude and frequency attributes of GPR data to predict fluid permeabilities away from the measured vertical transects and to delineate the distribution and geometry of mudstone layers inside the reservoir analog. Statistically significant relationships are determined between the well data (fluid permeability and mudstone content) and the GPR attributes. These calibrations are applied to the entire GPR volume to estimate the 3-D fluid permeability variation and the lateral development of mudstone units. Measured and predicted fluid permeabilities range from 0.1 to 290 md. One of the five units considered contained no mudstone layers; cores from the other four units contained 18-42% mudstone and mudstone intraclast conglomerate. The mudstone content is estimated to be 8% by volume in these four units. Variograms show that the mudstone bodies fall into two main categories; most are 2.3-3.5 m in extent in the maximum correlation direction, with anisotropies of 0.4 to 0.7. A few ribbon-like mudstone bodies are also present, with 20- to 30-m extents in the maximum correlation direction and with anisotropies of similar to0.1.