In the decade following the Deepwater Horizon catastrophe, considerable research and development has been accomplished to address known research gaps to respond to offshore oil spills; however, opportunities to enhance spill response capabilities remain. The Bureau of Safety and Environmental Enforcement (BSEE) is the lead agency in the U.S. regulating energy production on the U.S. Outer Continental Shelf. BSEE's Oil Spill Response Research (OSRR) program is the principal federal source of oil spill response research to improve the detection, containment, treatment/cleanup of oil spills and strives to provide the best available information, science, research, and technology development to key decision makers, industry, and the oil spill response community. The paper will highlight several key collaborative projects with federal and industry stakeholders including System and Algorithm Development to Estimate Oil Thickness and Emulsification through an UAS Platform and Methods to Enhance Mechanical Recovery in Arctic Environments. Additionally, the paper will provide an update on the Development of a Low-emission Spray Combustion Burner to Cleanly Burn Emulsions where we partnered the Naval Research Laboratory and met with industry representatives to incorporate their needs in the final phases of the development effort.
The Bureau of Safety and Environmental Enforcement's Oil Spill Response Research Program The Bureau of Safety and Environmental Enforcement's (BSEE) mission is to promote safety, protect the environment, and conserve resources offshore through vigorous regulatory oversight and enforcement. Title VII of The Oil Pollution Act of 1990 sets forth oil spill response research and development requirements, and the establishment of Ohmsett for oil pollution research (OPA90, Public Law 101-380, as amended through PL 115–382, Enacted December 4, 2018). BSEE's Oil Spill Response Research (OSRR) program works to protect people and the environment by optimizing spill responses through its applied research program, integrated with government and industry partners to develop the best and safest available technology. OSRR research engineers work closely with other Federal agencies including the U.S. Coast Guard, the National Oceanic and Atmospheric Administration (NOAA), and the Environmental Protection Agency (EPA) to continually enhance response technologies and capabilities. Ohmsett – The National Oil Spill Response Research and Renewable Energy Test Facility, located in Leonardo, New Jersey is managed under the OSRR program.
As with historic major oil spills, there was heightened public awareness of the need for research and development into viable oil spill response measures after the 2010 Deepwater Horizon oil spill. The oil industry also stood up several research initiatives including the American Petroleum Industry's (API) Joint Industry Task Forces (JITF). Funds from BP and Transocean settlements established the Gulf of Mexico Research Initiative (GOMRI) and the National Academy of Science's (NAS) Gulf Research Program that focuses on health and safety issues. The International Oil and Gas Producers (IOGP) established the Arctic Oil Spill Response Technology Joint Industry Programme (JIP) to increase greater understanding of spill response in the Arctic. GOMRI's efforts primarily focus on environmental issues and basic research. BSEE's OSRR program spans the areas of chemical treating agents (dispersants, surface collecting agents or herders), in situ burning and combustion of crude oil, the behavior of oil in the marine environment, mechanical containment and recovery, remote sensing, and decision-making support tools. These research initiatives have focused on understanding the implications associated with the Deepwater Horizon oil spill response, advancing the state of the art in response technologies, and preparing for a potential oil spill under arctic conditions. In regard to Ohmsett, the nation's premiere oil spill research and training venue, the projects have focused on enhancing data collection tools, scientific protocols, and enhanced capabilities to meet the ever-changing oil spill response venue needs.
BSEE continues to advance the science and technology available to respond to an offshore oil spill. Major changes have occurred over time with respect to offshore spill response capabilities including subsea dispersant injection, aerial dispersant application, and improvements in remote sensing from aerial platforms. However, there remains a need to advance technology to address larger spills in challenging offshore response environments. As oil exploration and production activities move into deeper waters, new response technologies should be explored that have been developed in related fields that may support better outcomes in offshore oil spill response efforts.
BSEE is working to institutionalize the use of newly-defined Technology Readiness Levels (TRL) and their application to the technology development process. This effort will result in a measured, progressive technology development program, as well as provide a metric to gauge success. BSEE's OSRR staff conducts literature syntheses and gap analyses to avoid conducting duplicative research, identify relevant research needs, and effectively leverage past research and development activities. Finally, BSEE is preparing emerging technology for real-world use. Using newly defined technology readiness levels (TRL) as shown in Table 1 and other tools at our disposal, we are expanding efforts into ensuring that response options have undergone appropriate testing and are validated products ready for use in responding to an oil spill in the marine environment.
This paper will highlight several key BSEE oil spill research initiatives where we are collaborating with federal and industry stakeholders to advance technology to respond and mitigate oil spills on water including: System and Algorithm Development to Estimate Oil Thickness and Emulsification through an UAS Platform and Methods to Enhance Mechanical Recovery in Arctic Environments. Additionally, the paper will provide an update on the “Development of a Low-emission Spray Combustion Burner to Cleanly Burn Emulsions” where we partnered the Naval Research Laboratory and met with industry representatives to incorporate their needs in the final phases of the development effort.
SYSTEM AND ALGORITHM DEVELOPMENT TO ESTIMATE OIL THICKNESS AND EMULSIFICATION
The project's focus was on the implementation of an array of sensors called a multispectral imager that would collect data from floating layers of oil and emulsions which would be used to derive thickness information from the floating oil. The objective was to build a suite of sensors and configure them to create a real and near-real time system that could be used for oil spill response and assessment operations.
This project started with the selection of commercial imagers (multispectral cameras) that fit our needs in terms of wavelengths, resolution, costs, and configurations. Then the project included two phases: Phase 1: Lab Testing, consisted on the elaboration of layers of oil in a controlled setting where we could validate the multispectral imager response to identify different levels of thicknesses, and Phase 2: Field testing, which consisted on the testing on a real life spill scenario where we could demonstrate the potential of the multispectral sensor package.
This system was successfully developed, calibrated, and tested in different sets of conditions by mounting it on an Unmanned Aerial System (UAS). This algorithm/sensor system demonstrated its capacity of identifying areas and locations of actionable oils to response units. (Figure 1). The information generated from the system allowed improved oil mitigation and control actions by responder vessels and for the assessment of the impact and magnitude of the oil spill.
Our vision is to facilitate this development of an oil spill response system in which remotely sensed images by a UAS are interpreted with validated algorithms providing intelligent classifications of oil thicknesses. This now operational system will help to direct fleet vessels to locations where responders will have the highest remediation value. Additionally, this system will help to evaluate the magnitude of an oil spill by using oil thickness classification on the quantification of the oil volume discharged.
METHODS TO ENHANCE MECHANICAL RECOVERY IN ARCTIC ENVIRONMENTS
Consultation with industry experts and oil spill responders identified several areas where research and development could improve oil spill response operations specific to cold weather. This collaborative project with the Army Corps of Engineer's Cold Regions Research and Engineering Laboratory (CRREL) and the oil spill removal organization Alaska Clean Seas (ACS) leveraged the experience of ACS to identify major limitations to current cold weather oil recovery operations. Two of these limitations include: (1) recovering oil trapped under a solid ice sheet is time consuming, and current methods are not extremely effective, and (2) the use of a standard rope mop skimmer can be limited by cold temperatures due to ice buildup on the system that renders it inoperable.
Techniques to Enhance Oil Recovery Under Solid Ice
Oil spilled under ice can collect in sub-surface depressions generated during ice growth, and over time can become encapsulated within the ice. ACS identified a desire to enhance its current approach to oil-under-ice recovery which includes identifying the location(s) of the trapped oil, cutting recovery holes through the solid ice at identified locations to release the oil, and recovering the oil using skimmer equipment placed in the hole or burning the oil. This approach is time consuming and labor intensive and becomes unfeasible as the number of locations of oil and size of spill increases. ACS was interested in exploring the use of a remotely operated vehicle (ROV) equipped with an air application system to inject air into the oil pockets to displace the oil and “herd” it under the ice to a central recovery hole for removal (Figure 2). If successful, this approach would reduce the number of recovery holes and ultimately the amount of time and effort required to remediate a spill under ice.
CRREL conducted initial experiments at their facility by simulating an ice sheet with a sub-surface depression using an acrylic sheet equipped with a center dome. This sheet was placed on the surface of a 3 × 3 × 1 m deep water filled basin (Figure 3). Oil was injected into the center dome and various air application systems were assessed to determine their ability to dislodge and move the oil to a desired location.
The most effective air application system was then installed on an underwater ROV (Figure 4) and tested CRREL's outdoor Geophysical Research Facility (GRF) under an 18.3 × 6.7 × 0.3 m thick salt water ice sheet containing sub-surface depressions. Alaska North Slope (ANS) oil was injected under the ice sheet into each depression. Two holes were cut through the ice; one hole was used for ROV deployment/recovery and the second for the planned recovery of the oil herded by the ROV. The ROV equipped with the air application system and underwater camera was deployed through the ice and maneuvered by CRREL personnel to the oil filled depressions. The applicator system was activated to deliver air to dislodge and herd the oil to the designated recovery hole. Figure 5 shows an underwater view of the ROV releasing air to displace the oil.
The ROV equipped with the air application system was successful at introducing air into the oil filled depression and moving the oil to one side of the pocket. Once enough air was added to the pocket, it found the lowest edge to escape, and carried the oil with it. This made controlling the direction in which the oil moved very difficult and initially unpredictable. The bottom of the ice sheet was not flat and was bowed up at the sheet's edges. Once the oil was released from the depression it travelled naturally to the edge of the ice sheet rather than to the designated recovery hole. It was necessary to cut an additional trench to facilitate oil recovery.
The ROV air application system was successful at dislodging oil from a pocket under the ice sheet. However, additional research is required to improve the ability to guide the oil to a desired location. BSEE is currently conducting research to equip an ROV with the ability to vacuum under-ice pockets containing oil, scrape newly formed ice crystals, and pump recovered product to the surface for temporary storage.
Methods to Reduce Icing of the Vertical Rope Mop Skimmer
Alaska Clean Seas uses vertical rope mop oil skimmers during their oil recovery operations. Vertical rope mop oil skimmers are considered very reliable and can be effectively used to recover oil in broken ice conditions. These skimmers employ long, continuous loops of oleophilic fibers (mops) that rotate down onto the oil/water surface to collect oil and then rotate to the top of the skimmer where they pass through a roller/wringer mechanism which releases the oil into a collection sump (Figure 6a). In low temperature conditions, the mops can become laden with ice which reduces their available oil collection surface area. In addition, the ice can clog the roller/wringer mechanism or the sump inlet, making the skimmer inoperable.
This study was conducted in two phases. In Phase I, two heat application methods were tested to assess their ability to prevent or reduce ice accumulation on the mop. Figure 6b shows the steam application collar developed by CRREL and Figure 6c shows the skimmer insulated in a casing heated with electric heating pads. Testing was conducted in CRREL's temperature-controlled Material Evaluation Facility (MEF) facility. A 3 × 3 × 1 m basin was filled with saline water. The skimmer was operated in the water at a set air temperature of −10oC, −20o C or −28o C, and ice accumulation was measured for one hour. Figure 7 shows pounds of ice accumulated on the skimmer with the different heating methods at an air temperature of −28 oC. The insulated casing reduced ice accumulation by 66%, and the steam application collar prevented any ice accumulation on the skimmer.
In Phase II the skimmer's oil recovery performance was measured with and without the steam application collar using ANS crude oil. The skimmer was operated for one hour in water at −10o C or −20o C to allow ice accumulation to occur. ANS was then added to the basin to create a slick thickness of 2.5 cm. This thickness was maintained throughout testing by adding ANS as necessary. The skimmer recovered for 60 minutes, and recovered fluid was collected in 10-minute increments for later fluid recovery rate and oil recovery efficiency calculations. For the tests using the steam application collar, the steam was applied after 25 minutes of operation. After each test, the oil-water mixture was decanted to measure the changes in fluid recovery rate and recovery efficiency over time.
Figure 8 shows test results of fluid recovery rate and oil recovery efficiency at −10o C. For the baseline test without steam, a continuous decrease in fluid recovery rate occurred throughout the test period. With the use of the steam application collar the fluid recovery rate starts to increase as the steam melts the accumulated ice and increases the available oil collection surface area. Initially the steam did not enhance oil recovery efficiency. However, as the test progressed the oil recovery efficiency increased and stabilized at approximately 45%.
This study demonstrated that use of a steam collar can reduce or eliminate ice accumulation and thus potentially extend operating time of a rope mop skimmer in arctic conditions. ACS has subsequently developed their own steam collar which they are currently testing (Figure 9).
LOW-EMISSION SPRAY COMBUSTOR FOR EMULSIFIED CRUDE OIL “BSEE BURNER”
A sub-scale and engineering-scale burner were designed, built, and tested in an effort to develop a single nozzle burner capable of efficiently atomizing and burning unweathered, emulsified, and weathered crude oil for spill response and remediation. The sub-scale and engineering-scale burners were capable of burning 22.9 bbl/day and 91.5 bbl/day, respectively. It was discovered that the flow-blurring atomizers used in these burners were able to effectively atomize the highly viscous emulsified crude oil, even with nozzle diameters of 12.7 mm and 25.7 mm. The increasing size of both the atomizer and burner geometry has been shown to increase burn temperature without negatively impacting burner performance. A parallel laboratory study used a flat-flame stabilized spray burner to examine fundamental spray combustion behavior. It was shown that flame radiation has a significant impact on the droplet ignition and spray flame propagation.
This project involves the development of a low-emission spray combustor for emulsified crude oil. To date, testing and examination of fundamental spray combustion behavior of crude oils in a sub-scale (25%) and an engineering-scale (50%) burner have been completed. Test efforts included laboratory-scaled spray measurements, flame characterization, and analytical measurements of the oils, their emulsion and weathered mixtures, and the combustion products. A recent concept demonstration study by the Naval Research Laboratory (NRL) showed the feasibility of using a flow-blurring atomizer (FBA) to (Tuttle, 2014) atomize and burn unweathered and emulsified crude oil with nozzle pressure drops less than 20 psig This is a crucial step in developing an alternative in situ burn technology for oil spill remediation. Offshore crude oil spill remediation is generally performed by gathering the surface oil into large pools where the oil is either pumped into floating storage bladders for shipping to oil processing facilities (Smith, 1978) or the pools are ignited to form large fires (Buist, 1999). ISB produces large plumes of soot and other potentially harmful pollutants (Schaum et al, Kearney et al, Markatos, et al, and Argyropoulos et al) and leaves a slick of residual hydrocarbons remaining on the ocean surface (Scholz, 2005). The seawater provides a nearly infinite heat sink that prevents a layer 1 - 3 mm-thick of crude oil from evaporating and burning. Additionally, ISB cannot reliably burn emulsified crude oil formed by surface or benthic mixing (Buist, 1999). In contrast, oil flares, formed by spraying and igniting crude oil, produce much less soot than in situ burning and have been reported to be capable of burning emulsified oil with seawater volume fractions up to 80% (Buist, 1999 and Tebeau, 1998). In the past, these flares have used atomizers that were either mechanically complex or required high air and oil pressures that small sea vessels cannot supply. For example, the Super Green burner manufactured by Expro operates at ~1400 psig.
The principle benefit of incorporating the FBA into a combustor system is the low atomization pressure. For large, sea-based vessels and oil exploration platforms, which have onboard power generation systems capable of supplying more than a megawatt of power, supplying power to high-pressure pumps and compressors is trivial. For a small vessel, such a power requirement is not practical. Another benefit of the FBA atomizer is the simple design. It contains no moving internal parts and it only requires liquid and air supply pressures up to 30 psig. Additionally, the liquid orifice size is quite large (~2–50 mm), allowing particulate debris to pass through the atomizer without clogging it.
A notional layout of the oil capture, process, and storage system is shown in Figure 10. There are three power generation or transmission systems required. The first is electrical power generation to operate the ignition system. The same generator could also provide electrical power to the second and third systems: the hydraulic and pneumatic systems. The hydraulic system provides the power to operate the skimmer and the associated pumps. The pneumatic system provides air for the atomizer and could also be integrated into the pneumatic system used for the spill booms.
The test conditions for Figure 11a and b are 2.0×10−2 kg/s of air with oil flows of 1.0 and 2.01 L/min (air-liquid ratio of 1.3 and 0.65), respectively. In both cases, there were no residual droplets that escaped the burn plume. In this case, there were visible soot emissions, without residual crude oil droplets. This indicates that the unit was effectively atomizing the crude oil and that there was sufficient heat produced by the spray flames and reflected back to the plume by the combustor shroud to evaporate all and burn most of the crude oil mixture.
Scientists from the Environmental Protection Agency's Office of Research and Development, Center for Environmental Measurement and Modeling sampled the plume emissions. (Note: the burner is highly efficient and there were insufficient volumes of unburned residue available for sampling.) Of particular interest were Particulate matter (PM2.5) CO, CO2, particulate carbon (TC) and black carbon. The TC to the total carbon sampled (TC + carbon from CO2 and CO) ranged from 0.02–0.15% which can be compared to 6.3% in the plumes from the gulf oil spill in situ oil burns. Lower PM2.5 emission factors were found from Hoops and Middle Weight-High Flow than Hoops Emulsified and Middle Weight-Low Flow. The emission factor ranged from 2.5 to 41 g/kg oil, which can be compared to in situ oil burns with emission factors ranging from 110–160 g/kg oil. Black carbon was continuously measured in the plume. The Middle Weight oil type attributed to higher black carbon emission factors than Hoops (Figure 12). An increase emission factor (EF) with burn number was found for Hoops Emulsified and Middle Weight high flow (HF) (Figure 13). This may be attributed by changes in the configuration or just by coincident. The values here (<1 g/kg oil) compare with values for open air pan burns of 53 g/kg oil (Gullett et al., 2017).
An increase in size from 12.7 mm to 25.7 mm diameter atomizer did not inhibit the atomizer performance in any way. This is especially important as the final burner concept will have a 50 mm diameter for the intended capacity of 366 bbl/day to meet the skimming rates of the Vessel of Opportunity Skimming System (VOSS). NRL researchers found during development and testing of the larger engineering-scale burner that practical crude oil spray combustion improves with increasing size. The larger plume produced a much greater radiant heat transfer than the smaller plume, as measured by the thermocouples in the flow and the higher temperatures of the components. The radiant heat transfer to the surrounding combustor shroud increases, which transfers more heat to the entrained air that passes through the shroud dilution holes, and the resulting combustion more stable. Higher temperature ensures that the oil spray will evaporate and burn rapidly.
Currently during the final phase of research, work continues to resolve some of the engineering issues of the burner system. First, the ignition source has been refined using glow plugs to produce a steady, high temperature ignition source is available to ignite, and anchor emulsified and weathered mixtures. Researchers continue work with emulsified and weathered mixtures, ensuring their stability and defining their chemical properties to assist in ignition studies. The thermal strain on the structure of the burner is being addressed by refining the burner design to build a structure that can be assembled, repeatedly thermally cycled, disassembled, stored, and shipped. The final report detailing the 50% engineering scale burner can be found on the BSEE web page at https://www.bsee.gov/research-record/osrr-1061-development-low-emission-spray-combustor-emulsified-crude-oil (Tuttle, 2017).