Rock Physics Modeling for the Potential FORGE Site on the Eastern Snake River Plain, Idaho

Abstract

Rock physics models allow establishing a physical-mathematical relation between rock and fluid properties and geophysical attributes. In this study, we propose to apply rock physics model to a geophysical dataset measured at two well locations near the proposed Snake River Plain FORGE site in eastern Idaho. The potential target is a rhyolite layer, which occurs between 2,000 and 3,000 m. The available data include two sets of sonic and petrophysical well logs at two well locations, which are approximately 6 km apart. The goal of this study is to calibrate a physical model to link reservoir properties (porosity, lithology, saturation) and reservoir conditions (pressure and temperature) with geophysical attributes (velocities, density, and resistivity). This multi-physics model is calibrated at the well locations, but can be extended to the entire site if geophysical data are available. As a feasibility study to determine the value of information of 3D geophysical surveys we plan to build synthetic 2D sections through the two existing wells by interpolating well log data using geostatistical techniques such as kriging and sequential Gaussian simulations and compute the predicted seismic, electromagnetic and gravimetric responses of the model. By combining rock physics models with mathematical inverse theory, we plan to perform a sensitivity analysis on the resolution and noise level of the geophysical survey in order to determine the minimum requirements of the geophysical data acquisition to improve the reservoir description. We will also compare the new results with a previous study based on 2D refraction seismic, resistivity and gravity fields.