Fluid Flow and Growth of Active Salt Structures at Decadal Timescales: Paradox Basin, Utah

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

This project is aimed at quantifying how fluid flow in evaporite (salt) deposits controls 3D brittle strain in the upper crust, in addition to solute transfer and it's connections between Earth's surface and subsurface. The research will help understand how transient fluid flux drives short-term brittle strain at timescales of days to decades and distances of tens of meters to kilometers. The research team will characterize active surface deformation with 1:5,000 scale field mapping and construction of cross sections, analysis of InSAR scenes, and installation of a three-component extensometer (creep meter) across a rapidly slipping boundary fault. In addition researchers will assess patterns and rates of surface and groundwater flowing through or directly into buried salt and its effect on rock strength as governs by hydraulic weakening and dissolution. Three-dimensional mechanical modeling will be undertaken to test models constrained by observed strain at the surface, fluid flux, groundwater modeling, structural geology and topography. The goal is to fully characterize how fresh water moves through the salt system, how that modulates plastic strain by dissolution and changes on the strength of halite and the role topography plays in coupled surface and subsurface processes. The work?s broader significance includes understanding how fluid flow and strain in salt systems evolves at scales not available by other means. The researchers are particularly interested in determining how transient surges in plastic salt flow might respond to input of the seasonal influx of surface runoff and groundwater recharge. The field work is located in the Paradox evaporite basin in eastern Utah, a region noted for its extraordinarily well-exposed rocks and wealth of available surface and subsurface data. This work will build on the recent discovery of transient surges in unconfined salt bodies in western Iran and the Dead Sea in Israel. These structures, which consist of emergent domes and flows of pure rock salt are modern examples of geologic structures analogous to glaciers and are similar to features in areas such as the Gulf of Mexico that contain great petroleum reserves. The research will define the conditions that control deformation and growth of salt structures and relate this to conditions such as the inflow of fresh water and outflow of saline brines within them. These studies will utilize a wide array of techniques and data previously unavailable in past studies. The ultimate goal is thus to define the physical conditions that control and guide their development in order that this may be applied in general to other salt structures around the world. On a global scale, this work is of interest to responsible resource exploration in salt basins for hydrocarbons. For instance the Deepwater Horizon well that created the oil spill in the Gulf of Mexico in 2010 was being drilled into a salt structure, and the cause of the blowout was an unforeseen increase in fluid pressure. In addition, this work holds the promise to quantify the saline brine influx into the Colorado River and shallow groundwater and its effect on the degradation of water quality in the largest source of fresh water in the southwestern United States.