Prediction of Natural CO2Migration and Distribution in Little Grand Wash and Salt Wash Faults System

The Little Grand Wash (LGW) and Salt Wash (SW) faults located in the eastern Utah are sites of the well-known CO₂ natural analogue. In these sites, both CO₂ and brine have leaked periodically through abandoned wellbores (e.g. Crystal and Tenmile geyser) and diffusively around fault traces. The objective of this study is to predict leakage process of natural CO₂ in LGW and SW faults system.

Two-dimensional simulation models were developed (LGW and SW fault models) in order to mimic migration and distribution of CO₂ in complex fault systems. LGW and SW faults were assumed to act vertically as a conduit and horizontally as a barrier while regional multiple aquifers and aquitards were interbedded each other. As a consequence, buoyant CO₂ were accumulated within trapping structure formed by formations and faults. In addition, CO₂ in traps were supplied through multiple CO₂ pathways; (1) direct migration of CO₂ via fault, (2) CO₂-dissolved brine migration from the San Rafael Swell, and (3) dispersive CO₂migration through regional caprock (i.e. Kayenta formation).

Subsequently, several sensitivity studies were conducted to reduce uncertainty of hydrogeological properties of LGW fault and Kayenta formation, and location of CO₂ source. By using previously investigated field data such as CO₂ flux anomalies, and distribution of travertine and CO₂ geyser, result of simulation at reference range of permeability of LGW fault. Moreover, relatively permeable caprock, such as fractured or corroded formation, could contribute to develop CO₂ traps in both LGW and SW fault model. Based on the location of cold water geysers (e.g. Tumble Weed and Chaffin Ranch geyser), the SW fault must contain its own CO₂ sources from deep formations. Finally, through comparison of between largely developed CO₂ trap in northern footwall and distribution of travertine and CO₂ geyser, SW fault structural complexity could be roughly explained.