Lessons Learned from the Large-Scale CO2 Stimulation of 11 Unconventional Wells in the Williston Basin: A Practical Review of Operations, Logistics, Production Uplift, and CO2 Storage

The paper introduces the results of the first CO2 fracturing campaign conducted in the Williston Basin. From 2015 to 2019, 11 horizontal multi-stage wells were safely stimulated using a CO2-hybrid design to improve production and store CO2 underground. The fracturing design consisted of the injection of a super-critical CO2 pre-pad (with a target injected volume of 5,000 tons per well) followed by a traditional slickwater or hybrid proppant slurry. The CO2 was captured from point-source plants that would have released the CO2 to the atmosphere otherwise. The performance of the CO2 fracturing design is compared to the performance of nearby hybrid and slickwater designs. The paper provides a range of potential production uplift for both 12-month production and EUR. The paper also provides the range of CO2 concentrations produced back to the surface and an estimate of CO2 storage potential based on extensive compositional monitoring. The paper shares practical guidelines and recommendations to facilitate the understanding and logistics of CO2 operations during injection and production. The field study highlights critical considerations related to fracturing design, logistics, operational handling of CO2, reservoir uplift, and permanent CO2 storage potential. The analysis provides new insight to the storage potential for CO2 fracturing, EOR, and/or carbon capture and storage (CCS) applications in the Williston Basin, and by extension to other ultra-tight formations.