Environmental risk assessment of enhanced oil recovery solutions

PhD thesis in Risk management and societal safetyThe overall objective of the research presented in this thesis is to contribute new knowledge about the environmental risk related to shortlisted products and processes developed at the National Improved Oil Recovery (IOR) Centre of Norway and about how to assess such risk. According to the World Energy Outlook report presented by the International Energy Agency in 2021, oil and natural gas will continue to be important contributors to the energy mix over the next 20 years. Implementing enhanced oil recovery (EOR) solutions is important to maintain oil production from existing fields, as it is becoming increasingly difficult to discover new oil and gas reserves. An EOR screening study conducted across 53 reservoirs in 27 of the largest fields on the Norwegian Continental Shelf (NCS) found significant potential for additional oil recovery through EOR solutions. The (IOR) Centre of Norway has been developing new products and processes as part of EOR solutions to improve oil recovery on the NCS. Using these products and processes offshore poses an environmental risk to the marine environment and atmosphere, which needs to be assessed and managed. This thesis explores existing environmental risk assessment (ERA) approaches for offshore oil production and identifies knowledge gaps related to assessing the environmental risk of EOR solutions. The knowledge gaps are filled by using laboratory studies to generate new data, using this data in models to generate key insights, and by developing new methods for ERA of EOR solutions and proposing improvements to existing methods. The research conducted in this thesis has resulted in five scientific papers that are summarized below. Paper I presents a literature review on ERA guidelines relevant to offshore oil production. A review of the primary sources of environmental impacts and key environmental stressors resulting from offshore oil and gas production is also conducted. The main sources of environmental impacts from offshore oil production include operational discharges of produced water (PW), drilling waste to the marine environment, and air emissions from energy production using fossil fuels. The literature review indicates that current ERA practices may form a basis for ERA of EOR solutions; however, there are also knowledge gaps related to the ERA of new products and processes planned to be used as a part of EOR solutions. Based on the review, a generalized ERA framework for PW and drilling waste into the sea and for air emissions is proposed in Paper I. Several products and processes are developed at the IOR Centre to quantify and increase oil recovery as a part of EOR solutions. Using these new products and processes results in their back-production with PW, which is typically discharged into the marine environment. As a result, the main focus of this thesis is on the ERA of PW discharges caused by the implementation of EOR solutions. Quantifying residual oil saturation is important for the successful implementation of EOR solutions. The IOR Centre has proposed a group of seven chemicals (tracers) for potential use in quantifying residual oil saturation in oil reservoirs. Using these tracers in offshore oil fields results in their operational discharges (e.g., with PW) into the marine environment. Once released into the sea, marine organisms may become exposed to the tracers, thereby posing an environmental risk to the ecosystem. Paper II first reports on laboratory experiments conducted to measure the biodegradability and toxicity of seven tracer compounds. A hypothetical case of using tracer compounds on the NCS is then assumed. Discharge of PW containing tracers, along with other production chemicals from the Brage field (used as a proxy case), is simulated using the dynamic risk and effects assessment model (DREAM), which estimates the contribution to the environmental impact factor (EIF) values from each tracer. In addition, the seven tracer compounds are ranked from low to high in terms of their environmental impact. This ranking of the tracers can be used to shortlist the tracer(s) with minimum environmental impact for offshore applications. Polymer flooding is a process in which high molecular weight synthetic polymers are injected into an oil reservoir to increase oil recovery. Injected polymers are usually back-produced with the PW, which is typically discharged into the sea. These synthetic polymers have slow microbial degradation rates under aerobic conditions, unless the molecular weight is reduced to less than 3 kilodaltons. Photocatalytic depolymerization rates for several different synthetic EOR polymers have been measured as a part of another project at the IOR Centre. In Paper III, a novel method is proposed to estimate the residual lifetime of synthetic polymers in the marine environment. Residual lifetime is the amount of time the discharged synthetic polymer takes to reach a molecular weight, below which it becomes biodegradable in the sea. The proposed method uses the DREAM model to estimate the concentration distribution of polymers in the sea. Subsequently, the concentration distribution is linked with the depolymerization rate equations to estimate the residual lifetime of synthetic polymers in the sea. The applicability of this developed procedure is demonstrated by estimating the residual lifetime of synthetic polymers discharged from single and multiple oil fields on the NCS. Paper IV assesses the exposure and effects of discharging synthetic EOR polymers into the sea. Two main approaches are used: The first is based on estimating the EIF values of discharging PW-containing polymers using near-field simulations (where the discharge point is placed within a 50*50-kilometer grid). The estimated contribution to EIF values from synthetic polymers suggests negligible environmental impact when no assessment factor (AF) is used and low/moderate impact when an AF of 50 is used. The AF is a simple way to account for uncertainty in the assessment. The second approach, based on far-field simulations (where the discharge point is placed within a 1200*1800-kilometer grid), is primarily studied to assess polymer build-up in the sea, as synthetic EOR polymers show resistance to microbial degradability. In one of the farfield simulations, polymers are repeatedly released annually over a 10-year period from seven arbitrarily chosen oil fields on the NCS. The highest concentration values (based on the 75 percentiles) during the first and tenth years of discharge are used in a regression analysis against the amount of polymer discharged each year. The regression analysis indicates that polymers will not build up within the simulation area at the expected amounts of polymers discharged each year. Moreover, there is a considerable margin of safety between the highest concentration values calculated by the model and the concentration at which harmful effects in aquatic species are predicted. Paper V focuses on the use of species sensitivity distributions (SSDs) in ERA. An SSD is used to determine the threshold effect levels of stressors, below which unacceptable effects on a group of species are not expected. A literature review is performed to understand how risk is currently defined and how uncertainties are addressed when using SSDs in ERA. It is found that current ways of handling uncertainties while using SSDs are not based on unified guidance provided by the field of risk science. In Paper V, a risk-oriented framework is proposed that addresses uncertainties in a systematic manner while using SSDs. The proposed framework addresses uncertainties due to both lack of knowledge and variability. Furthermore, a scheme for assessing bias in theoretical and practical assumptions underlying SSDs is included in the framework. Lastly, a qualitative method is proposed to characterize the strength of knowledge underlying the SSDs

An environmental risk assessment framework for enhanced oil recovery solutions from offshore oil and gas industry

Environmental risk assessments are necessary to understand the risk associated with enhanced oil recovery (EOR) solutions and to provide decision support for choosing the best technology and implementing risk-reducing measures. This study presents a review of potentially relevant environmental/ecological risk assessment (ERA) guidelines and, based on this review, proposes an initial suggestion of an ERA framework for understanding the environmental impacts from EOR solutions. We first shortlist the important elements necessary for conducting an ERA of EOR solutions from the selected guidelines. These elements are then used to build the suggested ERA framework for produced water discharges, drilling discharges and emissions to air from EOR solutions, which is the primary objective of the present study. Furthermore, the emphasis is placed on identifying the knowledge gaps that exist for conducting ERA of EOR processes. In order to link the framework with the current best environmental practices, a review of environmental policies applicable to the marine environment around the European Union (EU) was conducted. Finally, some major challenges in the application of ERA methods for novel EOR technologies, i.e. uncertainties in the ERA due to lack of data and aggregation of risk from different environmental impacts, are discussed in detail. The frameworks suggested in this study should be possible to use by relevant stakeholders to assess environmental risk from enhanced oil recovery solutions.publishedVersio

Environmental risk assessment of inter-well partitioning tracer compounds shortlisted for the offshore oil and gas industry

Quantifying residual oil saturation (SOR) in the inter-well region of oil and gas reservoirs is key for successfully implementing EOR solutions. Partitioning inter-well tracer tests (PITTs) has become a common method for quantifying SOR. A new group of seven chemicals – pyridine, 2,3-dimethyl pyrazine, 2,6-dimethyl pyrazine, 4-methoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol, 4-chlorobenzyl alcohol, and 2,6-dichlorobenzyl alcohol – have been proposed as potential partitioning tracers for quantifying SOR. Using these tracers can lead to their environmental release in the marine environment through produced water discharges, with currently limited knowledge on impacts in the marine ecosystem. The primary objective of the present study is to assess the environmental risk of discharging the tracer compounds in the marine environment. We investigated the fate and effect of these tracers in the marine environment. Biodegradability in seawater was measured to understand the fate of tracers in the marine environment. The acute toxicity of tracers was measured in terms of the percent cell viability of a rainbow trout gill cell line (RTgill-W1) and growth inhibition of the algae Skeletonema costatum. The ecotoxicological information obtained from these experiments was used in the dynamic risk and effects assessment model (DREAM) to calculate the tracers’ contribution to the environmental impact factor (EIF). The results from the DREAM simulations suggest no contribution towards EIF values from any of the tracers at the expected back-produced concentrations. Results from simulations at higher concentrations suggest that both pyrazines have the lowest environmental risk, followed by 3,4-dimethoxybenzyl alcohol, 4-methoxybenzyl alcohol, and pyridine; while both chlorobenzyl alcohols show the highest environmental risk.publishedVersio

Continued glacial retreat linked to changing macronutrient supply along the West Antarctic Peninsula

At the West Antarctic Peninsula (WAP), continued atmospheric and oceanic warming is causing significant physical and biogeochemical changes to glaciers and the marine environment. We compare sediment sources and drivers of macronutrient distributions at two bays along the WAP during austral summer 2020, using radioactive radium and stable oxygen isotopes to trace sedimentary influences and quantify different freshwater inputs. In the Ryder Bay, where the Sheldon Glacier is marine-terminating, radium activities at the sediment-water interface indicate considerable benthic mixing. Using radium isotope activity gradients to resolve radium and macronutrient fluxes, we find buoyant meltwater proximal to the glacier drives vigorous mixing of sediment and entrainment of macronutrient deep waters, on the order of 2.0 × 105 mol d−1 for nitrate. Conversely, in the Marian Cove, where the Fourcade Glacier terminates on land, low salinities and oxygen isotopes indicate a meltwater-rich surface layer <1 m thick and rich in sediment, and strong vertical mixing to the seafloor. A continued shift to land-terminating glaciers along the WAP may have a significant impact upon nutrient and sediment supply to the euphotic zone, with impacts upon primary productivity and carbon uptake efficiency. The future of primary production, carbon uptake, and food web dynamics is therefore linked to glacier retreat dynamics in the many fjords along the WAP

Sequence Relationships among C. elegans, D. melanogaster and Human microRNAs Highlight the Extensive Conservation of microRNAs in Biology

microRNAs act in a prevalent and conserved post-transcriptional gene regulatory mechanism that impacts development, homeostasis and disease, yet biological functions for the vast majority of miRNAs remain unknown. Given the power of invertebrate genetics to promote rapid evaluation of miRNA function, recently expanded miRNA identifications (miRBase 10.1), and the importance of assessing potential functional redundancies within and between species, we evaluated miRNA sequence relationships by 5′ end match and overall homology criteria to compile a snapshot overview of miRNA families within the C. elegans and D. melanogaster genomes that includes their identified human counterparts. This compilation expands literature documentation of both the number of families and the number of family members, within and between nematode and fly models, and highlights sequences conserved between species pairs or among nematodes, flies and humans. Themes that emerge include the substantial potential for functional redundancy of miRNA sequences within species (84/139 C. elegans miRNAs and 70/152 D. melanogaster miRNAs share significant homology with other miRNAs encoded by their respective genomes), and the striking extent to which miRNAs are conserved across species—over half (73/139) C. elegans miRNAs share sequence homology with miRNAs encoded also in both fly and human genomes. This summary analysis of mature miRNA sequence relationships provides a quickly accessible resource that should facilitate functional and evolutionary analyses of miRNAs and miRNA families

Study of Environmental Regulations for Emissions to Air in the EU and the US, and to understand guidelines of regulations in the EU by considering a case of aluminum industry

Master's thesis in Environmental technologyClimate change and high level of atmospheric pollution is a global problem that has taken on particular significance in recent years and will continue to grow in the near future. To deal with this problem, it is very important to adopt sustainable development practices in organizations day to day activities. The goal of sustainable development is to meet the needs of present generations without compromising the ability of future generations to meet their own needs. There are three main pillars of achieving sustainable development: environment, economic and social, in this study the focus is on the environmental pillar. To achieve environmental sustainability, there is a large number of voluntary and mandatory environmental standards. These standards provide guidelines for making the environmental pillar strong. In this study, mandatory environmental standards affecting heavy industries in the US and the EU were studied and compared. Additionally, linkage of these standards with global and continental environmental treaties were studied. The study suggests that, the EU is somewhat ahead of the US when it comes to climate change regulations. For regulations concerning air pollution, the US is still the environmental leader and the policies in the EU are not always leading to the best outcomes when it comes to industrial environmental performance due to weak enforcement system in the EU. To understand the application of environmental regulations, the aluminum industry was selected in the EU. Main regulations studied were EU-ETS for reducing GHG emissions (climate change) and IED for reducing harmful pollutants entering the atmosphere (air pollution). For EU-ETS, methods for quantification of GHG emissions were studied. For IED, monitoring methodology and emission limit values of different pollutants based on the use of best available technology was studied. The study suggests that there exists a good framework within these regulations for reducing GHG emissions and other harmful pollutants from entering into the atmosphere in the EU from aluminum industry. Finally, it has been demonstrated that reporting of organizations performance on environmental sustainability is important for both internal and external stakeholders. Therefore, effort is made to understand internal reporting mechanisms and processes in the organizations. Also, a detailed analysis was done for the monitoring and reporting process under the IED. The result from this analysis can be used to constitute a system design for implementing monitoring and reporting process of IED on software systems

Performance evaluation of adaptive suppression schemes for asynchronous CDMA systems in frequency-selective multipath fading

Includes bibliographical references (pages [104]-106)The thesis objective is to examine various adaptive schemes for asynchronous Code Division Multiple Access (CDMA) in frequency-selective multipath fading environments. Three schemes are considered here in detail; (i) N-tap adaptive detector, (ii) D-tap cyclically shifted filter bank (CSFB) scheme and (iii) Blind equalization scheme. The normalized Least Mean Square (NLMS) algorithm is used for tap adaptation in the first two methods. The gradient descent algorithm is used for the blind equalization scheme. The system considered has 10 users of which 8 are synchronous (v^ =0) with a relative power level of 5dB. It has one asynchronous user (vj =40Tc) with a relative power level of lOdB with respect to the desired user. The chip length was considered to be of length 63 and an input AWGN of variance 0.01. The users are provided with a pseudo-random sequence generated by the Gold code generator, which is preferred over regular shift register code generators due to its relatively better code properties. The results show that all three schemes perform well even in the presence of a multipath fading channel. The N-tap MMSE detector exhibits better initial convergence, while the CSFB scheme performs better after the initial convergence is achieved. Blind equalization gives improved results as compared to the matched filter receiver, although the earlier two schemes perform better than blind equalization.M.S. (Master of Science

Thermo-mechanical characterization of polyimide thin film using bulge test

Bulge test has been used to test elastic properties of metal and ceramic films, but has proved inadequate to the task of testing viscoelastic properties for materials like polymers. A novel bulge test setup has been designed to overcome this drawback. The capability of the new setup to test at elevated temperatures and in controlled environments increases the scope of bulge test to a wide range of tests and materials. PMDA-ODA polyimide is used as the material to be characterized using the new bulge test setup designed as part of the dissertation. The material is also tested with alternative testing methods (TGA, TMA, wafer curvature and microtensile). The results from the alternate methods are used in conjunction to confirm the findings of bulge test as well as to prove its validity as a viscoelastic characterization tool. The polyimide material is characterized for it Tg, degradation temperature, coefficient of thermal expansion, residual stress, modulus and creep behavior.Master of Engineering (MAE

MicroRNA modulation of caenorhadbitis elegans dietary restriction and longevity

Aging is a universal biological phenomenon involving a complex decline in the ability of the organism to respond adequately to intrinsic and extrinsic stresses, leading to age-related diseases and pathologies. All organisms age, but the larger questions of how and why aging occurs are still being deciphered despite decades of research and experimentation . We present evidence identifying microRNAs, small non-coding RNAs that regulate gene expression by repressing target mRNAs through partially complementary binding, significantly impact Caenorhabditis elegans longevity. We have identified several mir mutants that impact not only lifespan but also specific aspects of aging like metabolic aging vs muscle aging. Excitingly we have also identified that the mir-80 mutant animal is under chronic dietary restriction – a conserved pathway that extends life- and healthspan in many diverse organisms. The mir-80(Δ) mutant exhibits multiple parameters of healthy aging, reduced fecundity and expression of molecular reporters associated with dietary restriction. Using a targeted RNAi approach we have identified several stress response transcription factors (daf-16, hsf-1 and skn-1), the metabolic energy sensor (AMPK) and the transcriptional co-factor cbp-1 as important requirements for mir-80(Δ) longevity and the DR-state. Finally we show that mir-80 longevity is also partially regulated by the conserved insulin/IGF-1 signaling pathway. In summary, we identify the first metazoan microRNA that regulates longevity through conserved dietary restriction and suggest a model whereby mir-80 may regulate a network of stress response and metabolic genes to impact C. elegans longevity. In conclusion, we identify novel miRNAs that modulate C. elegans longevity and the first microRNA that modulates longevity through dietary restriction.Ph. D.Includes bibliographical referencesby Mehul M Vor

Prediction of reverse osmosis performance using artificial neural network

108-115Reverse osmosis (RO) has found extensive usage in the fields of desalination and pollution control. In the present work, an attempt is made to model the separation of sodium chloride-water system by reverse osmosis using neural nets. Experimental data are used to train the network developed for the said system. The training data included the feed concentration range from 1000 to 30000 ppm, pressure range from 20 to 100 atm, and feed rates from 300 to 1500 mL/min. The network thus developed has been found to predict the system variables within the error range of ±1%, except for sudden deviations in process parameters, and initial and final value of flow rates at low pressures. Nearly the same trend, that is, maximum errors at lower pressures and higher flow rates, were observed in the prediction of RO performance with membrane transport models, reported earlier. The reasons for this may be the unsteady state behaviour of the system, or system instability or error in experimentation. Such deviations are not of much importance, because the predicted and experimental values are within the satisfactory range