Mark Naylor

CO2 leakage from geological storage facilities: environmental, societal and economic impacts, monitoring and research strategies

Carbon capture and storage (CCS) has the potential to significantly limit CO 2 emissions to the atmosphere; however a leakage of CO 2 from transport or storage could have environmental and safety implications. Monitoring of CCS storage is a further challenge, both to assure the public and, should leakage occur, to enable mitigation and verification. This chapter reviews the current state of knowledge regarding environmental sensitivities and monitoring and outlines the challenges for research over the next few years. The current hypothesis is that significantly large leaks would be required to cause noticeable damage in the ecosystem.

Volcanic eruption forecasts from accelerating rates of drumbeat long-period earthquakes

Accelerating rates of quasiperiodic “drumbeat” long-period earthquakes (LPs) are commonly reported before eruptions at andesite and dacite volcanoes, and promise insights into the nature of fundamental preeruptive processes and improved eruption forecasts. Here we apply a new Bayesian Markov chain Monte Carlo gamma point process methodology to investigate an exceptionally well-developed sequence of drumbeat LPs preceding a recent large vulcanian explosion at Tungurahua volcano, Ecuador. For more than 24 hr, LP rates increased according to the inverse power law trend predicted by material failure theory, and with a retrospectively forecast failure time that agrees with the eruption onset within error. LPs resulted from repeated activation of a single characteristic source driven by accelerating loading, rather than a distributed failure process, showing that similar precursory trends can emerge from quite different underlying physics. Nevertheless, such sequences have clear potential for improving forecasts of eruptions at Tungurahua and analogous volcanoes.

Natural CO2 sites in Italy show importance of overburden geopressure, fractures and faults for CO2 storage performance and risk management

Abstract The study of natural analogues can inform the long-term performance security of engineered CO2 storage. There are natural CO2 reservoirs and CO2 seeps in Italy. Here, we study nine reservoirs and establish which are sealed or are leaking CO2 to surface. Their characteristics are compared to elucidate which conditions control CO2 leakage. All of the case studies would fail current CO2 storage site selection criteria, although only two leak CO2 to surface. The factors found to systematically affect seal performance are overburden geopressure and proximity to modern extensional faults. Amongst our case studies, the sealing reservoirs show elevated overburden geopressure whereas the leaking reservoirs do not. Since the leaking reservoirs are located within <10 km of modern extensional faults, pressure equilibration within the overburden may be facilitated by enhanced crustal permeability related to faulting. Modelling of the properties that could enable the observed CO2 leakage rates finds that high-permeability pathways (such as transmissive faults or fractures) become increasingly necessary to sustain leak rates as CO2 density decreases during ascent to surface, regardless of the leakage mechanism into the overburden. This work illustrates the value of characterizing the overburden geology during CO2 storage site selection to inform screening criterion, risk assessment and monitoring strategy.