Hydrate Swapping for CO 2 storage & CH 4 Production: Challenges & Innovations

• Main Author: Pandey, Jyoti Shanker
• Format: Book
• Language: English
• Published: Technical University of Denmark 2021
• Subjects: permafrost
• Online Access: https://orbit.dtu.dk/en/publications/9a5e6f9d-07df-497a-86c2-9beff112bb1b; https://backend.orbit.dtu.dk/ws/files/263411780/Jyoti_Shanker_Thesis_Reduced_size.pdf

Sedimentary gas hydrate deposits occurring in geological settings in cold regions such as permafrost and deep oceans are considered a clean gas source to meet future energy needs. A large amount of CH 4 -rich gas stored in these reservoirs could also leak into the atmosphere due to melting caused by global warming. Therefore, there is an urgent need to extract CH4 gas from these reservoirs on a commercial scale and stabilize the hydrate reservoirs. CO 2 injection into CH 4 hydrates addresses both of the above concerns with the added benefit of CO 2 storage in the hydrate reservoir. This technique is referred to as “hydrate swapping”. CO 2 gas also tends to form hydrates, similar to CH 4 hydrates. Thermodynamically, CO 2 hydrates are more stable than CH4 hydrates. Therefore, CO 2 injection into CH 4 hydrate would cause spontaneous conversion of CH 4 -rich hydrate system to CO 2 -rich hydrate system. This is expected to release CH 4 gas for production, store CO 2 in the hydrate, and improve the thermodynamic stability of hydrate-bearing sediments. Although hydrate swapping is an environmentally friendly, carbon-neutral technique and poses less risk to geomechanical stability, the technique has not yet been applied commercially due to the low CH 4 production volume. This technique suffers from low CO 2 injectivity and low CO 2 sweep range caused by the mass transfer barrier at the gas-liquid interface. The mass transfer barrier reduces the volume of CO 2 that can be injected into the CH 4 hydrate, reduces the gas mobility in the pore space, and may even trap the produced CH 4 gas. Therefore, in this study, we attempted to improve CH 4 recovery and store additional CO 2 . In our first approach, we sought to understand the effect of the mass transfer barrier on CH 4- CO 2 hydrate exchange. To do this, we altered the pore water chemistry by adding chemicals (inhibitors and promoters) to the water in small doses. Paper 1 and Paper 2 focused on the effects of the additives at the core scale to investigate their effect ...