InterPore2023

Novel laboratory apparatus for understanding microbiology in hydrogen storage in porous media

23 May 2023, 10:30

1h 30m

Poster Presentation (MS05) Biochemical processes and biofilms in porous media Poster

Speaker

Dr Simon Gregory (British Geological Survey)

Description

Controllable but realistic representation of subsurface gas storage scenarios are needed to assess the impacts that microbial processes could have on behaviour of stored gas in hydrogen storage. Current experimental approaches may misrepresent the type and magnitude of microbial activity as they do not consider the limited residual water available as habitats for microorganisms. Understanding microbial processes is necessary as microorganisms could consume and produce gases (including converting hydrogen to corrosive hydrogen sulphide or to methane) or block flow pathways with biomass or precipitates. These processes can only be properly assessed if the gas filled, residual water state can be recreated in the laboratory.
We have developed an experimental set-up that allows us to study microbial processes in both saturated and unsaturated conditions and change between them to represent fluid movement occurring at the fringes of stored gas during storage cycles. The fringes of stored gas have been identified as a potential hotspot for microbial processes.
The apparatus comprises two 1000 ml syringe pumps attached to a core sample held in a pressurised vessel. The system can be operated at pressures of up to 130 -500 Bar (depending on configuration) which is representative of pressures expected during hydrogen storage cycles. The sample can be heated up to at least 90 °C to cover the expected activity range of subsurface microorganisms. The system allows the core to be saturated from the base of the sample by flowing a suitable groundwater mimicking the environment in a saline aquifer prior to gas storage. Using the second pump, groundwater can be displaced from pore spaces by injecting hydrogen into the top of the core sample, leaving a residual volume of water more closely replicating the conditions that would occur in a storage reservoir. Continuous logging of flow, pressure and volumes allow the degree of saturation and flow properties to be calculated. Sampling ports allow collection of both gas and water samples, allowing microbial gas consumption and conversion and impact on water chemistry to be monitored.
The apparatus is currently undergoing proof-of-concept testing in which stimulation of methanogens within sandstone cores is being investigated. Although the system most closely resembles hydrogen storage in saline aquifers, it is also relevant to storage in depleted hydrocarbon fields and storage of carbon dioxide.