Effects of high pressure and temperature conditions on the chemical fate of flowback water related chemicals

Environmental risk assessment is generally based on atmospheric conditions for the modelling of chemical fate after entering the environment. However, during hydraulic fracturing, chemicals may be released deep underground. This study therefore focuses on the effects of high pressure and high temperature conditions on chemicals in flowback water to determine whether current environmental fate models need to be adapted in the context of downhole activities. Crushed shale and flowback water were mixed and exposed to different temperature (25-100 °C) and pressure (1-450 bar) conditions to investigate the effects they have on chemical fate. Samples were analysed using LC-HRMS based non-target screening. The results show that both high temperature and pressure conditions can impact the chemical fate of hydraulic fracturing related chemicals by increasing or decreasing concentrations via processes of transformation, sorption, degradation and/or dissolution. Furthermore, the degree and direction of change is chemical specific. The change is lower or equal to a factor of five, but for a few individual compounds the degree of change can exceed this factor of five. This suggests that environmental fate models based on surface conditions may be used for an approximation of chemical fate under downhole conditions by applying an additional factor of five to account for these uncertainties. More accurate insight into chemical fate under downhole conditions may be gained by studying a fluid of known chemical composition and an increased variability in temperature and pressure conditions including concentration, salinity and pH as variables

Effects of pore fluid chemistry on compaction of sand and sandstone reservoirs : From experiments to potential applications and associated risks

To limit climate change and its impact on society and environment, anthropogenic emissions of greenhouse gases, such as CO2 and methane, must be reduced to zero or even to negative values by a portfolio of actions. These include both decarbonisation of the energy system, by switching to carbon-neutral energy sources such as wind, solar, geothermal and biomass, and elimination of emissions from fossil fuel use via carbon capture and storage (or utilisation). During the transition to a more sustainable energy system, natural gas, being a relatively low-carbon fossil fuel, is widely assumed to play an important interim-role. However, prolonged gas production is leading to surface subsidence and induced seismicity in an increasing number of gas fields around the world, due to depletion-driven compaction of the reservoir rock. The hesis addresses the geological and environmental risks related to subsurface fluid injection into depleted hydrocarbon reservoirs. It explores the effect of injected pore fluid chemistry on the mechanical behaviour of sands and sandstones, in the context of the potential for mitigating reservoir compaction caused by gas production, geothermal energy production and geological storage application

Effects of pore fluid chemistry on compaction of sand and sandstone reservoirs : From experiments to potential applications and associated risks

To limit climate change and its impact on society and environment, anthropogenic emissions of greenhouse gases, such as CO2 and methane, must be reduced to zero or even to negative values by a portfolio of actions. These include both decarbonisation of the energy system, by switching to carbon-neutral energy sources such as wind, solar, geothermal and biomass, and elimination of emissions from fossil fuel use via carbon capture and storage (or utilisation). During the transition to a more sustainable energy system, natural gas, being a relatively low-carbon fossil fuel, is widely assumed to play an important interim-role. However, prolonged gas production is leading to surface subsidence and induced seismicity in an increasing number of gas fields around the world, due to depletion-driven compaction of the reservoir rock. The hesis addresses the geological and environmental risks related to subsurface fluid injection into depleted hydrocarbon reservoirs. It explores the effect of injected pore fluid chemistry on the mechanical behaviour of sands and sandstones, in the context of the potential for mitigating reservoir compaction caused by gas production, geothermal energy production and geological storage application

Facilitating sustainable geo-resources exploitation: A review of environmental and geological risks of fluid injection into hydrocarbon reservoirs

Natural gas is an important low-carbon geo-resource for sustaining future energy demand. However, production is currently impeded by the negative effects of reservoir compaction, i.e. induced seismicity and surface subsidence. Fluid injection into producing or depleted hydrocarbon reservoirs is one of the strategies to mitigate compaction, though it may introduce other negative consequences. This study aims to identify lessons and potential knowledge gaps on the causes and mechanisms of consequences of such injection operations. An overview of the environmental and geological hazards and risks is developed by examining literature on four commonly injected fluids, i.e. CO2, methane, nitrogen and wastewater. The well-recognised hazards are leakage, reservoir deformation and induced seismicity, which have consequences for several environmental receptors, e.g. the atmosphere, surface sediments and water, subsurface resources and groundwater. Generally, in defining the risk, there is a consensus on the probability of hazards occurrence, while a lack of knowledge on the hazard impacts exists. The assessment approaches analysis also indicates that consequence magnitude evaluations and comparisons to thresholds are often missing from the risk assessments. For all examined injection fluids, knowledge on hazard occurrence, hazard exposure and receptor affectability is insufficient. Furthermore, in complex subsurface systems with high uncertainty, more insight in the probability of multiple hazards occurrence and the corresponding cumulative risks is needed

Facilitating sustainable geo-resources exploitation: A review of environmental and geological risks of fluid injection into hydrocarbon reservoirs

Natural gas is an important low-carbon geo-resource for sustaining future energy demand. However, production is currently impeded by the negative effects of reservoir compaction, i.e. induced seismicity and surface subsidence. Fluid injection into producing or depleted hydrocarbon reservoirs is one of the strategies to mitigate compaction, though it may introduce other negative consequences. This study aims to identify lessons and potential knowledge gaps on the causes and mechanisms of consequences of such injection operations. An overview of the environmental and geological hazards and risks is developed by examining literature on four commonly injected fluids, i.e. CO2, methane, nitrogen and wastewater. The well-recognised hazards are leakage, reservoir deformation and induced seismicity, which have consequences for several environmental receptors, e.g. the atmosphere, surface sediments and water, subsurface resources and groundwater. Generally, in defining the risk, there is a consensus on the probability of hazards occurrence, while a lack of knowledge on the hazard impacts exists. The assessment approaches analysis also indicates that consequence magnitude evaluations and comparisons to thresholds are often missing from the risk assessments. For all examined injection fluids, knowledge on hazard occurrence, hazard exposure and receptor affectability is insufficient. Furthermore, in complex subsurface systems with high uncertainty, more insight in the probability of multiple hazards occurrence and the corresponding cumulative risks is needed

Stress-cycling data uniaxial compaction of quartz sand in various chemical environments

Decarbonisation of the energy system requires new uses of porous subsurface reservoirs, where hot porous reservoirs can be utilised as sustainable sources of heat and electricity, while depleted ones can be employed to temporary store energy or permanently store waste. However, fluid injection induces a poro-elastic response of the reservoir rock, as well as a chemical response that is not well understood. We conducted uniaxial stress-cycling experiments on quartz sand aggregates to investigate the effect of pore fluid chemistry on short-term compaction. Two of the tested environments, low-vacuum (dry) and n-decane, were devoid of water, and the other environments included distilled water and five aqueous solutions with dissolved HCl and NaOH in various concentrations, covering pH values in the range 1 to 14. In addition, we collected acoustic emission data and performed microstructural analyses to gain insight into the deformation mechanisms. The data is provided in one folder for 26 experiments/samples. Detailed information about the files in these subfolders as well as information on how the data is processed is given in the explanatory file Schimmel-et-al_2020_data-description.docx. Contact person is Mariska Schimmel - PhD - [email protected] / [email protected]

TB-HIV co-infection in the Netherlands: estimating prevalence and under-reporting in national registration databases using a capture-recapture analysis

Background Knowledge of the HIV status in patients with tuberculosis (TB) and vice versa is crucial for proper individual patient management, while knowledge of the prevalence of co-infection guides preventive and therapeutic strategies. The aim of the study was to assess if national disease databases on TB and HIV are adequate sources to provide this information. Methods A two way capture-recapture analysis to assess the completeness of the registers, and to obtain the prevalence of TB-HIV co-infection in the Netherlands in the years 2002-2012. Results HIV testing was performed in less than 50% of the patients with TB. Of the 932 TB-HIV infected patients, just 293 (31.4%) were registered in both registers. Under-reporting of TB-HIV co-infection ranged from 50% to 70% in the national TB register, and from 31% to 37% in the HIV database. Prevalence of TB-HIV co-infection in the Netherlands in 2012 was 7.1% (95% CI 6.0% to 8.3%), which was more than double of the prevalence estimated from the national TB database. Conclusions TB-HIV co-infection is markedly under-reported in national disease databases. There is an urgent need for improved registration and preferably a routine data exchange between the two surveillance systems