Carbon capture and storage (CCS) aims to reduce atmospheric CO2 by capturing emitted gas for storage in subsurface locations. Microorganisms such as methanogens and acetogens, can utilize H2 and CO2 as a carbon and energy source in the subsurface. In enrichments with produced water (PW) from a potential CCS site, high concentrations of acetic acid were observed followed by methane production. Microbial community compositions of enrichments showed the percentage of methanogens increased as enrichment period progressed while the percentage of acetogens decreased. Methanogens of the order Methanomicrobiales were mostly present when enrichment pH was acidic or neutral. Mixing PW with source water (SW) at the site also affected the types of microbes present in PW samples. Mixing PW with SW resulted in an increase of CFU/mL indicating some additional growth. Microbial community composition analysis indicates that oil field microorganisms may have originated from SW.