NUMERICAL SIMULATION FOR CO2 MIGRATION, DISTRIBUTION, AND GEYSERING PROCESSES AT LITTLE GRAND WASH AND SALT WASH FAULTS IN UTAH

Geologic CO₂ sequestration is considered as one of means to reduce CO₂ concentration. However, stored CO₂ can leak from the targeted formation if there exist any unwanted pathways. Leaked CO₂ can cause to secondary groundwater contamination and ultimately have potential to induce detrimental effects to the surrounding environment. In these reasons, many studies have been conducted to understand natural CO₂ leakage process. Green River area, in eastern Utah, USA, is a well-known CO₂ natural analogue site where CO₂and brine leaked periodically through the abandoned wellbore and diffusively through east-west cutting normal faults such as Little Grand Wash (LGW) and Salt Wash (SW) fault.

Two-dimensional simulation models delineating the region containing both LGW and SW faults and Crystal geyser were developed. In these fault systems, supercritical CO₂ and Paleozoic brine move via faults, and meteoric ground water which is recharged from San Rafael Swell flows with dissolved CO₂ through the Navajo Sandstone. Since LGW fault acts vertically as a conduit (k_v = 10^-16 m² ) and horizontally as a barrier (k_h = 10^-17 m²) (Jung at al., 2015) while confining formations and aquifers are interbedded each other, anticlinal CO₂ trapping were developed adjacent to faults. Overall regional formations dip (4 degrees) to north and the LGW faults dip (70 degrees) to south made CO₂ trapping zones develop not at the hanging wall but at footwall, and thus, at the hanging wall updip migration of CO₂ occurred. Consequently, CO₂ moved toward SW fault (the south). Due to this reason, CO₂ trapping zone was developed at footwall of the northern SW fault. In two of southern faults, in spite of CO₂ supply from northern fault, anticlinal CO₂ trapping was not formed. Rather, most of CO₂ directly diffused to the surface through faults. Additionally, eruption patterns for Crystal geyser simulated from this model were categorized to three processes including eruption, recharge and spring.