CO2 Storage Resource Potential of the Cambro-ordovician Saline System in the we Stern Interior of North America

Abstract

A 3-year binational effort between the United States and Canada was initiated to characterize the lowermost saline system in the northern Great Plains–Prairie region of North America and determine its CO2 storage capacity. This saline system covers an area of 1.34 million km2 from northern South Dakota in the United States to central Alberta and Saskatchewan in Canada. This basal system, overlain mostly by shales and comprising Middle Cambrian to Ordovician sandstones and carbonates that overlie the crystalline Precambrian basement, crops out in recharge areas in South Dakota and Montana and in discharge areas in Manitoba. Pressures in the system follow a gradient of 10.8 kPa/m. Temperatures vary from greater than 150°C in the deepest part of the system to less than 10°C in outcrop areas. Water salinity ranges from greater than 300,000 mg/L in central Alberta and in North Dakota to less than 10,000 mg/L in recharge and discharge areas. Porosity varies from less than 1% in very deep regions to more than 25% in shallower regions. The area of the basal saline system suitable for CO2 storage was determined using the following criteria: a) CO2 should be stored at a distance greater than 20 km from the 10,000 mg/L water salinity isoline, to protect groundwater resources; b) porosity should be greater than 4%, to ensure storage capacity and injectivity; and c) CO2 should be always in dense phase. The storage capacity in the area of the saline system thus determined as suitable for CO2 storage was estimated using thickness, porosity, and CO2 density calculated at in situ conditions, and a storage efficiency coefficient of 2.4%, resulting in a storage capacity of 113 Gt CO2 with P50 confidence.