Abstract

Carbon dioxide (CO2) and other greenhouse gas (GHG) emissions have become a major challenge globally, and particularly for the oil and gas industry. Carbon capture, utilization and storage (CCUS) is one of the options to reduce the amount of anthropogenic CO2 entering the atmosphere. This option creates economic benefit from the waste CO2, vs. pure disposal for sequestration. Organic rich shale reservoirs are an attractive target for carbon storage, due to their adsorptive abilities and multiple mechanisms for gas storage.

CO2 has been widely used in oilfield operations since the 1950's. The unique physical properties of CO2 allow for easy transport in pipelines as a gas, or by transport truck as a cold liquid. Oilfield uses include: a gaseous agent to assist in fluid recovery from the wellbore, a component in hydraulic fracture fluids, an enhanced oil recovery (EOR) agent, a fluid blockage removal agent, etc. CO2 is at least partially soluble in water and is a strong hydrocarbon solvent.

This study investigates the amount of CO2 sequestered when utilized as a component in the hydraulic fracture fluid system used in multi-stage fractured horizontal wells in several different western Canadian formations. By careful analysis and accounting for the volumes of CO2 injected and returned during flowback, it will be shown that significant volumes of CO2 remain sequestered in the formation; in some cases up to 75% of the injected volume. With more stringent carbon regulations coming into effect in Alberta in 2017 (and Canada in 2020), this opens up a potential new avenue for emitters to utilize and store some of the CO2 they emit - into formations they are actively developing, while at the same time potentially monetizing carbon credits.

This is believed to be the first definitive study proving that CO2 is sequestered during hydraulic fracturing operations in organic rich shales and tight sandstone reservoirs. The study will show that there is a net environmental benefit to hydraulic fracturing with anthropogenic CO2 from an overall perspective. It will be shown that this unique application of CCUS also has significant economic benefit to the producer.

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