Browsing by Subject "Oil"

Oil spills in marine environments often damage marine and coastal life if not remediated rapidly and efficiently. In spite of the strict enforcement of environmental legislations (i.e., Oil Pollution Act 1990) following the Exxon Valdez oil spill (June 1989; the second biggest oil spill in U.S. history), the Macondo well blowout disaster (April 2010) released 18 times more oil. Strikingly, the response methods used to contain and capture spilled oil after both accidents were nearly identical, note that more than two decades separate Exxon Valdez (1989) and Macondo well (2010) accidents.

The goal of this dissertation was to investigate new advanced materials (mechanically strong aerogel composite blankets-Cabot® Thermal Wrap™ (TW) and Aspen Aerogels® Spaceloft® (SL)), and their applications for oil capture and recovery to overcome the current material limitations in oil spill response methods. First, uptake of different solvents and oils were studied to answer the following question: do these blanket aerogel composites have competitive oil uptake compared to state-of-the-art oil sorbents (i.e., polyurethane foam-PUF)? In addition to their competitive mechanical strength (766, 380, 92 kPa for Spaceloft, Thermal Wrap, and PUF, respectively), our results showed that aerogel composites have three critical advantages over PUF: rapid (3-5 min.) and high (more than two times of PUF’s uptake) oil uptake, reusability (over 10 cycles), and oil recoverability (up to 60%) via mechanical extraction. Chemical-specific sorption experiments showed that the dominant uptake mechanism of aerogels is adsorption to the internal surface, with some contribution of absorption into the pore space.

Second, we investigated the potential environmental impacts (energy and chemical burdens) associated with manufacturing, use, and disposal of SL aerogel and PUF to remove the oil (i.e., 1 m3 oil) from a location (i.e., Macondo well). Different use (single and multiple use) and end of life (landfill, incinerator, and waste-to-energy) scenarios were assessed, and our results demonstrated that multiple use, and waste-to-energy choices minimize the energy and material use of SL aerogel. Nevertheless, using SL once and disposing via landfill still offers environmental and cost savings benefits relative to PUF, and so these benefits are preserved irrespective of the oil-spill-response operator choices.

To inform future aerogel manufacture, we investigated the different laboratory-scale aerogel fabrication technologies (rapid supercritical extraction (RSCE), CO2 supercritical extraction (CSCE), alcohol supercritical extraction (ASCE)). Our results from anticipatory LCA for laboratory-scaled aerogel fabrication demonstrated that RSCE method offers lower cumulative energy and ecotoxicity impacts compared to conventional aerogel fabrication methods (CSCE and ASCE).

The final objective of this study was to investigate different surface coating techniques to enhance oil recovery by modifying the existing aerogel surface chemistries to develop chemically responsive materials (switchable hydrophobicity in response to a CO2 stimulus). Our results showed that studied surface coating methods (drop casting, dip coating, and physical vapor deposition) were partially successful to modify surface with CO2 switchable chemical (tributylpentanamidine), likely because of the heterogeneous fiber structure of the aerogel blankets. A possible solution to these non-uniform coatings would be to include switchable chemical as a precursor during the gel preparation to chemically attach the switchable chemical to the pores of the aerogel.

Taken as a whole, the implications of this work are that mechanical deployment and recovery of aerogel composite blankets is a viable oil spill response strategy that can be deployed today. This will ultimately enable better oil uptake without the uptake of water, potential reuse of the collected oil, reduced material and energy burdens compared to competitive sorbents (e.g., PUF), and reduced occupational exposure to oiled sorbents. In addition, sorbent blankets and booms could be deployed in coastal and open-ocean settings, respectively, which was previously impossible.

This thesis examines how the recent discovery of massive oil reserves off the coast of Cuba has driven a resurgence of Cuban-Russian relations in the 21st century. The first chapter demonstrates how the Russian government came to conceptualize the export of hydrocarbons as integral to the nation's development. It also examines the internal situation in Cuba after the fall of the Soviet Union to explain what initiated shifts in domestic policy that allowed for greater external investment. The second chapter discusses the effect of the discovery of these oil reserves, and how the Russians and the Cubans have come together over this issue against the backdrop of larger anti-American tendencies in Latin America. The first chapter relies more on secondary analyses of trends in both nations to help familiarize the reader with key concepts, such as the idea of Russia's energy weapon and Cuba's impetus for change. The second chapter heavily uses newspaper articles and speeches to demonstrate the visible shift in Russian attitude towards Cuba.

This thesis shows that the oil reserves have stimulated both countries to work closely together, though each has their respective reasons.

The primary focus of this dissertation is on the assessment of fugitive methane emissions from near and far-field sources. Methane is the second most prevalent greenhouse gas (GHG) emitted in the United States from anthropogenic activities. Due to measurement and model limitations, there is not an accurate assessment of how much methane in the atmosphere is due to anthropogenic sources. This dissertation focuses on measuring the methane emissions from two of the three largest anthropogenic sources -- landfills and natural gas systems. All measurements are made with a single fixed or single mobile sensor. Methods are developed to assess the source strength for both near (i.e. natural gas) and far-field (i.e. landfill) sources using either the fixed or mobile sensor.

For far-field measurements, a standardized version of a mobile tracer correlation measurement method was developed and used for assessment of methane emissions from 15 landfills in 56 field deployments from 2009 to 2013. A total of 1876 mobile tracer correlation measurement transects were attempted over 131 field sampling days.

Transects were analyzed using signal to noise ratio, plume correlation, and emission rate difference method quality indicators. The application of the method quality indicators yield 456 transects (33\%) that pass data acceptance criteria.

For near-field sources, techniques are developed for 1) fixed sensors sampling through time downwind of a source and 2) mobile sensors passing across plumes downwind of a source. For the fixed sensor, the lateral plume geometry is reconstructed from the fluctuating wind direction using a derived relationship between the wind direction and crosswind plume position. The crosswind plume spread is estimated with two different methods (modeled and observed), and subsequently used a Gaussian plume inversion to estimate the source strengths. For the fixed sensor, the sensor takes measurements for about 20 minutes and we are able to reconstruct the ensemble average of the plume.

For the mobile sensor, the vehicle drives through the plume in the crosswind direction.

The measurements show the lateral plume geometry of an instantaneous plume. The instantaneous plume has a narrowed Gaussian structure.

Two techniques are tested using data from controlled methane release experiments; these two techniques are 1) linear-squares and 2) a probabilistic approach. For the probabilistic approach, Bayesian inference tools are applied and special attention is paid to the relevant likelihood functions for both short time averaged concentrations from a single fixed sensor and spatial transects of instantaneous concentration measurements from a mobile sensor. The two techniques are also tested on measurements downwind of multiple natural gas production facilities in Wyoming for the fixed sensor and in Colorado for the moving sensor. The results for both the fixed and mobile techniques show promise for use with gas sensors on industry work trucks, opportunistically providing surveillance over a region of well pads.

The water energy nexus represents the intersection of water use, energy production, electricity generation, and waste generation and disposal. The rapid rise of unconventional natural gas and oil production through the combined processes of horizontal drilling and hydraulic fracturing have shifted the energy dynamic in the United States. Concurrently, the rising utilization of unconventional gas and oil production has intensified the water use for hydraulic fracturing and generation of flowback and produced water associated with shale gas and tight oil production. Among the major environmental risks associated with the rise of unconventional oil and gas exploration water availability, water contamination from leaking or disposal of wastewater, and adequate disposal of the wastewater are the key issues associated with the water-energy nexus. This dissertation aims to quantify the water use for hydraulic fracturing across the U.S., evaluate the water use for electricity production from natural gas in comparison to coal combustion, estimate the flowback and produced water production, and assess possible recycling of oilfield water through irrigation in California.

This dissertation describes the water footprint of hydraulic fracturing by examining total water use, water use per well, water use per length of horizontal well, and the changes in water use through time. The data show that hydraulic fracturing water use per well has been increasing between early stages (2008-2012) to later stages (2012-2016) of operation. In addition to water use, this dissertation estimated waste water generated from unconventional oil and gas wells and find a concurrent increase in flowback and produced water (FP water) per well through time. Using salinity as a marker to distinguish FP water from water injected for hydraulic fracturing, this dissertation observes the sequestration of the injected freshwater, while the return flow composed primarily of more saline formation brines entrapped within the shale formations.

In addition, this this dissertation explored two downstream impacts of the increasing water use and FP water generation. First, as abundant natural gas resources from the expansion of hydraulic fracturing have shifted the electricity sector from primarily coal- to primarily natural gas-fired, this study examined the impact increasing water use associated with hydraulic fracturing has had on power plant lifecycle water consumption and withdrawal. The study found that despite increasing water use for hydraulic fracturing, natural gas-fired generation on average used less water for cooling relative to coal-fired generation. Finally, this this dissertation examined the risks from recycling of oilfield produced water (OPW) as an agricultural makeup water source. The data from field studies in California show that by using low salinity OPW, farmers are able to successfully recycle OPW without risking metals accumulation in soil and consequently in crop and human health.