Light hydrocarbon and noble gas migration as an analogue for potential CO₂ leakage: numerical simulations and field data from three hydrocarbon systems

Abstract

Sites where anthropogenic CO2 captured from industrial sources is stored in deep geological formations for climate change mitigation are required to show secure retention of the injected CO2. Monitoring, reporting, and verification (MRV) plans are needed to indicate that no CO2 release has occurred. We explored the degree to which direct comparison between a surface anomaly and reservoir geochemistry using various geochemical parameters can be used for attribution. We used data collected on light hydrocarbons and noble gases throughout the sedimentary column at three CO2 enhanced oil recovery (EOR) sites to understand the processes that may cause fluid evolution. Light hydrocarbon and noble gases were sampled from reservoirs, gas‐bearing intervals above reservoirs, and groundwater. Vertical profiles indicated that lighter components are relatively enriched during migration (i.e. chromatographic separation). Static and numerical models were designed to simulate episodic gas migration and geochemical alteration of these geochemical parameters from solubility and sorption. The effects of hydrocarbon solubility were minimal (Bernard ratio changes within 5.2%) although field data were within the range of expected alterations from sorption. Forward models of CO2 migration and noble gas interactions showed that CO2 stripping causes an enrichment of crustal noble gases. In areas where natural fluxes of CO2 from depth are non‐existent, the occurrence of crustal noble gas signature may distinguish fugitive CO2 from the reservoir from natural near‐surface sources, and could be considered to explain apparent fluid anomalies. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Acid-Extracted Hydrocarbon Anomalies and Significance in the Chaoshan Depression of the Northern South China Sea

“…By detecting such anomalies, potential reservoirs can be predicted. Based on the direct correlation between latent petroleum reservoirs and the hydrocarbon concentrations of the gas adsorbed in sea bed sediments, the hydrocarbons' internal composition can be used to reliably forecast the properties of the migrated hydrocarbons and forecast the development characteristics of the underlying petroleum reservoir and distinguish its overall properties [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Development of methods for assessing the safety of light hydrocarbon storage facilities in emergency situations

“…Light hydrocarbons of different fractional composition are stored in reservoirs both in "pure" form and in a mixture with other additives [4]. Substances such as methane and ethane are rarely stored, mostly transported to consumers immediately after extraction [5]. In connection with this fact and low values of the gas phase density, the storage facilities for methane and ethane were not considered in the paper [6].…”

Comparing Direct Numerical Modeling Predictions With Field Evidence for Methane Vertical Microseepage in Two Geological Settings

“…Different mechanisms, such as buoyancy of microbubbles, continuous gas-phase flow, diffusion, and transport water solution, have been proposed to explain microseepage in oil prospective regions (e.g., Clayton and Dando, 1996;Klusman and Saeed, 1996;Kroos and Leythaeuser, 1996;Brown, 2000;Etiope 2015;Anderson et al, 2019) and anthropogenic settings, such as landfills and underground gas storage complexes (e.g., El-Fadel et al, 1996a,b;Jones and Burtell, 1996;Chen et al, 2000;Nastev et al, 2001;Martín et al, 2001;Zeng, 2019). The theoretical treatment of this phenomenon can be challenging, depending on the numerous factors considered in the problem statement, such as dimensionality, hydrocarbons source model, multiphase hydrocarbons transport, and time-variation hydrocarbons composition.…”