On sorption and swelling of CO2 in clays

Abstract

The geological storage of carbon dioxide (CO 2 ) is a well-studied technology, and a number of demonstration projects around the world have proven its feasibility and challenges. Storage conformance and seal integrity are among the most important aspects, as they determine risk of leakage as well as limits for storage capacity and injectivity. Furthermore, providing evidence for safe storage is critical for improving public acceptance. Most caprocks are composed of clays as dominant mineral type which can typically be illite, kaolinite, chlorite or smectite. A number of recent studies addressed the interaction between CO 2 and these different clays and it was shown that clay minerals adsorb considerable quantities of CO 2 . For smectite this uptake can lead to volumetric expansion followed by the generation of swelling pressures. On the one hand CO 2 adsorption traps CO 2 , on the other hand swelling pressures can potentially change local stress regimes and in unfavourable situations shear-type failure is assumed to occur. For storage in a reservoir having high clay contents the CO 2 uptake can add to storage capacity which is widely underestimated so far. Smectite-rich seals in direct contact with a dry CO 2 plume at the interface to the reservoir might dehydrate leading to dehydration cracks. Such dehydration cracks can provide pathways for CO 2 ingress and further accelerate dewatering and penetration of the seal by supercritical CO 2 . At the same time, swelling may also lead to the closure of fractures or the reduction of fracture apertures, thereby improving seal integrity. The goal of this communication is to theoretically evaluate and discuss these scenarios in greater detail in terms of phenomenological mechanisms, but also in terms of potential risks or benefits for carbon storage.

Influence of shale‐total organic content on CO2 geo‐storage potential

“…Shale matrix swelling by CO 2 injection is another limiting factor; however, sorption‐induced shale swelling is not confirmed and not well understood [ Busch et al ., ], compared to coal swelling which is well established [ Brochard et al ., ].…”

Characteristics of Clay-Abundant Shale Formations: Use of CO2 for Production Enhancement

“…The suitability of using CO 2 as a replacement for water-based fracking fluid in clay-abundant reservoirs has been extensively tested and the expansion behaviour of clay mineral in shale formations caused by CO 2 sorption is still a controversial topic [92]. Compared with water, CO 2 can induce much less swelling of clay minerals and the swelling effect is greatly dependent on the initial water content in clay minerals.…”

Impact of fracturing liquid absorption on the production and water-block unlocking for shale gas reservoir

“…The first one is the adsorption force by clay minerals (Busch et al, 2016;Cai et al, 2017b) which including osmotic hydrationand surface hydration. The double electrical layers theory is usually used to explain osmotic hydration.…”