Key controls on the hydraulic properties of fault rocks in carbonates

Abstract

A significant knowledge gap exists when analysing and predicting the hydraulic behaviour of faults within carbonate reservoirs. To improve this, a large database of carbonate fault rock properties has been collected from 42 exposed faults, from 7 countries. Faults analysed cut a range of lithofacies, tectonic histories, burial depths and displacements. Porosity and permeability measurements from c.400 samples have been made, with the goal of identifying key controls on the flow properties of fault rocks in carbonates. Intrinsic and extrinsic factors have been examined, such as host lithofacies, juxtaposition, host porosity and permeability, tectonic regime, displacement, maximum burial depth as well as the depth at the time of faulting. The results indicate which factors may have the most significant influence on fault rock permeability, improving our ability to predict the sealing or baffle behaviour of faults in carbonate reservoirs. Intrinsic factors, such as host porosity, permeability and texture, appear to play the most important role in fault rock development. Extrinsic factors, such as displacement and kinematics, have shown lesser or, in some instances, a negligible control on fault rock development. This conclusion is, however, subject to two research limitations: lack of sufficient data from similar lithofacies at different displacements, and a low number of samples from thrust regimes.Thematic collection: This article is part of the Fault and top seals collection available at: https://www.lyellcollection.org/cc/fault-and-top-seals-2019

The Importance of Physiochemical Processes in Decarbonisation Technology Applications Utilizing the Subsurface: A Review

“…(1) Knowledge transfer from fossil fuel industry and sharing of data publicly (e.g., Erdlac, 2006;Bu et al, 2012;Groff et al, 2016): This should include the re-skilling and repurposing/ deployment of highly skilled and experienced oil and gas professionals, especially engineers and geologists; (2) Knowledge transfer from active decarbonisation plants around the world to allow optimization and sustainable implementation of technologies in other countries: Examples include storing CO 2 in basalt in the CarbFix Pilot Project in Iceland (Matter et al, 2009), geothermal energy plants such as Reykjanes, Krafla (Friðleifsson et al, 2015;Friðleifsson et al, 2019) or Larderello, Italy (Batini et al, 2003), and ATES at Eindhoven University of Technology in Netherlands (Kallesøe and Vangkilde-Pedersen, 2019); (3) Short and long term laboratory experiments: For instance, scaling experiments (e.g., Stáhl et al, 2000), porositypermeability measurements on fault rocks (e.g., Michie et al, 2020a;Michie et al, 2020b) coupled with in-depth microstructural studies (e.g., Kaminskaite et al, 2019;Kaminskaite et al, 2020); (4) Experiments at test sites, such as the UKGEOS coal mine geothermal test site in Glasgow, nuclear waste disposal sites in Olkiluoto, Finland (Siren, 2015), SKB in Sweden (Rosborg and Werme, 2008), Mont-Terri in Switzerland (Tsang et al, 2012), Mol-Dessel in Belgium (Desbois et al, 2010), and Bure and Tournemire in France (Armand et al, 2007;Matray et al, 2007). ( 5) Study of natural geological systems for long term behaviour and comparisons of predictions based on laboratory experiments coupled with numerical simulations: For instance, outcrops and/or core plugs taken out from natural geothermal systems where hydrothermal fluids have been flowing over long timescales (>10 2 -10 4 yrs) or fossil geothermal systems provide us with the examples of how hydrothermal fluids have affected the rocks on a large scale and how long the system has sustained the flow for (e.g., Major et al, 2018); (6) Numerical modelling using sophisticated and continuously improving codes, e.g.,: Microstructural modelling using hybrid approaches e.g., ELLE (Vass et al, 2014;Piazolo et al, 2019;Koehn et al, 2020) or codes f...…”