Grantee Research Project Results
Final Report: Locating Oil-Water Interfaces in Process Vessels
EPA Grant Number: R827015C015Subproject: this is subproject number 015 , established and managed by the Center Director under grant R827015
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (1989) - Western HSRC
Center Director: McCarty, Perry L.
Title: Locating Oil-Water Interfaces in Process Vessels
Investigators: LoPresti, Peter G. , Manning, Francis S.
Institution: University of Tulsa
EPA Project Officer: Aja, Hayley
Project Period: June 14, 2001 through November 30, 2001
RFA: Integrated Petroleum Environmental Consortium (IPEC) (1999) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research
Objective:
Crude oil always is produced with connate water, and the water-to-oil ratio often is greater than 10 to 1. In the field, the well stream is first separated into its three phases: natural gas, crude oil, and produced water. Unfortunately, crude oil and produced water often form stable emulsions that severely impede the oil-water separation. Development of a thick emulsion or rag layer between the oil and water phases is the precursor to an upset. Such upsets reduce production and increase the emissions to land, water, and air. The current method of using floats to sense the oil-water interface in separators, treaters, and desalters fails when the emulsion layer thickens.
The overall goal is to assess the capability of a new technique for locating the oil/water interface and measuring the thickness of any rag layer inside production vessels. The technique consists of locating any oil/water or oil/emulsion or emulsion/water interfaces using fiber-optic pressure sensors. The specific objective of the research project was to evaluate the maximum possible pressure resolution attainable using differential detection methods and a receiver utilizing spatial demultiplexing.
Summary/Accomplishments (Outputs/Outcomes):
A test procedure was outlined in the project proposal to determine the maximum resolution. In the previous report, difficulties in constructing the required experiments were reported. An optical spectrum analyzer (OSA) replaced the intended spatial demultiplexer in order to perform a preliminary evaluation of sensor resolution. Oil and water were successfully differentiated using a float sensor design. A diaphragm sensor design showed promise but required an instrument with more resolution than the OSA. The spatial demultiplexing receiver was implemented successfully and tested thoroughly. The receiver is capable of higher wavelength resolution (and therefore pressure resolution) than the OSA.
Receiver Optimization
The receiver configuration evaluated is depicted in Figure 1. We used a grating with less-than-optimal properties because of difficulties in securing an ideal grating from a manufacturer. An imaging lens has been added. The lens lightly focuses the incoming light onto the camera. The location of the focused light depends on the location of the incident light on the lens, which is in turn dependent on the wavelength. There exists a design trade-off between the size of the focal spot and the instrument resolution.
Our efforts focused on the proper placement of the lens with respect to the grating and the camera and the proper choice of the lens’ focal length. Three different lenses having focal lengths of 19 mm, 38 mm, and 50 mm were evaluated. Each lens was positioned at several distances d from the camera, starting with d equal to the focal length and increasing in 10 percent increments. The distance was further refined by identifying the two distances that provided the best resolution and positioning the lens at a point halfway between these distances. The lens position with respect to the grating was determined with multiple sensor signals, as the lens diameter limits the maximum spatial difference between any two wavelength to be detected.
The first experiments focused on selecting the proper focal length of the lens and positioning with respect to the camera. For the experiments, a single sensor signal was used, and the signal wavelength varied using a piezo-electric stretcher. Wavelength changes were calibrated using the OSA at selected values of the voltage applied to the stretcher. The lens position was adjusted so that the focused light formed a circular spot on a relatively noise-free part of the camera. A circular spot ensures that the incoming optical rays are parallel to the optical axis of the lens, and therefore changes in location and shape of the recorded light pattern only are because of wavelength changes. Camera data was converted to a bit-map file and then into spreadsheet format for performing data processing. The centroid algorithm was applied to the data using MS Excel. Before applying the algorithm, however, some preprocessing was required, as light levels often caused the digital output from the camera to “cycle” one or more times—that is to reach 255 and cycle back to 0 one or more times for high optical powers incident at the pixel location.
Typical results as a function of focal length are shown in Figure 2. The 50 mm focal length lens did not produce significant movement in the spot location on the camera for most distances and was quickly discounted. The 38 mm lens produced significant movement (Figure 3), with an optimal location at 1.36 times the focal length, as determined by measurements of displacement and standard deviation at each position. For a 100 V change on the piezo-electric controller, corresponding to a 0.26 nm change in wavelength, a 4.9 pixel change in location was achieved. Thus, the linear dispersion at the camera input was 0.053 nm/pixel. As before, the minimum resolution of the instrument was set by twice the standard deviation of the measurements. The minimum resolution afforded by the 38 mm lens was 0.0387 pixels, corresponding to 2.05 pm. The 19 mm lens produced an even higher resolution of 0.060 nm/pixel but at a distance of 1.2 times the focal length. Typical results from the 19 mm lens are shown in Figure 4.
A second sensor was added to the test configuration to determine whether the lens was capable of capturing both wavelengths simultaneously at the distance for optimal resolution. The wavelengths of the two sensors were separated by 46.085 pixels when both sensors were at rest. A 1 inch diameter lens was just able to collect both wavelengths without significant diffraction of light from the edges of the lens, which would increase system noise. No measurable increase in diffraction was recorded when 17.2 V was applied to the piezo-electric driver on either sensor. For the current experimental parameters, a maximum of four sensors per fiber string could be discriminated accurately. The primary limitation on system performance still is the grating we are using currently. An imaging (concave) grating or one with a greater linear dispersion would improve both the resolution and the range of wavelengths that could be collected.
In the two sensor configuration, an experiment was conducted to determine the improvement in resolution of the receiver using differential measurement. The experiment was performed using the 38 mm lens. Results of the experiment are shown in Table 1 and Figures 5 and 6. On average, the resolution was improved by a factor of 44.3 percent, from 0.0595 to 0.0362 pixels. Based on these results, we expect that water and oil can be differentiated with the appropriate sensor design.
We are scheduled to begin resolution tests within the oil-water column in the next several weeks. As noted above, the resolutions obtained with the 38 mm and 19 mm lenses indicate that we will be able to differentiate between oil and water for both sensor designs. A diaphragm-based design is more desirable at present, because we believe it can be implemented with a minimum of moving parts and without exposure of the fiber optic cable to the external (and often hostile) environment present in a production column. We are conferring with the project consultants on the sensor designs and practical concerns in implementing the receiver.
Figure 1. Extended Path Experimental Setup for Spatial De-Multiplexing Receiver
Figure 2. Displacement at Camera Plane as a Function of the Lens Focal Length. Displacement is measured with respect to the voltage change on the piezo-electric controller.
Figure 3. Shift in the Peak Location on the Camera as a Function of the Distance Between Lens and Camera for the 38mm Focal Length Lens
Figure 4. Peak Location in Pixels as a Function of the Voltage Setting of the Piezo-electric Controller
Figure 5. Typical Processed Output for Dual Sensor Measurement. The pixel value has been adjusted for noise and for rollover in the quantized digital output.
Figure 6. Results of Differential Measurement Experiment. Voltage and position difference are sensor 2 – sensor 1. Note that there are two sets of measurements at –8.6 V, one for 0 V–8.6 V, and one for 8.6 V–17.2 V.
Table 1. Summary of Resolution Data for Differential Measurement. Measurements are quoted in terms of standard deviation.
[V1, V2] | [0, 0] | [0, 8.6] | [17.2, 8.6] | [0, 17.2] | [8.6, 0] |
σ1 + σ2 | 0.0392157 | 0.0473458 | 0.0406284 | 0.0833363 | 0.0869257 |
σ(2-1) | 0.0233435 | 0.0177992 | 0.0130581 | 0.0658063 | 0.0607721 |
% change | -40.5 | -62 | -67.9 | -21 | -30 |
Supplemental Keywords:
Arkansas (AR), petroleum, phytoremediation, EPA Region 6, rhizosphere,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Sustainable Industry/Business, Sustainable Environment, Environmental Chemistry, Analytical Chemistry, Technology for Sustainable Environment, Economics and Business, Ecological Risk Assessment, Technical Assistance, Ecology and Ecosystems, pollution prevention, Environmental Engineering, chemical waste, clean technologies, cleaner production, hazardous emissions, petrochemicals, oil production, hazardous waste, pollution control, IPEC, fiber optic pressure sensor, innovative technology, oil water separation, technology transfer, bioremediationMain Center Abstract and Reports:
R827015 HSRC (1989) - Western HSRC Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R827015C001 Evaluation of Road Base Material Derived from Tank Bottom Sludges
R827015C002 Passive Sampling Devices (PSDs) for Bioavailability Screening of Soils Containing Petrochemicals
R827015C003 Demonstration of a Subsurface Drainage System for the Remediation of Brine-Impacted Soil
R827015C004 Anaerobic Intrinsic Bioremediation of Whole Gasoline
R827015C005 Microflora Involved in Phytoremediation of Polyaromatic Hydrocarbons
R827015C006 Microbial Treatment of Naturally Occurring Radioactive Material (NORM)
R827015C007 Using Plants to Remediate Petroleum-Contaminated Soil
R827015C008 The Use of Nitrate for the Control of Sulfide Formation in Oklahoma Oil Fields
R827015C009 Surfactant-Enhanced Treatment of Oil-Contaminated Soils and Oil-Based Drill Cuttings
R827015C010 Novel Materials for Facile Separation of Petroleum Products from Aqueous Mixtures Via Magnetic Filtration
R827015C011 Development of Relevant Ecological Screening Criteria (RESC) for Petroleum Hydrocarbon-Contaminated Exploration and Production Sites
R827015C012 Humate-Induced Remediation of Petroleum Contaminated Surface Soils
R827015C013 New Process for Plugging Abandoned Wells
R827015C014 Enhancement of Microbial Sulfate Reduction for the Remediation of Hydrocarbon Contaminated Aquifers - A Laboratory and Field Scale Demonstration
R827015C015 Locating Oil-Water Interfaces in Process Vessels
R827015C016 Remediation of Brine Spills with Hay
R827015C017 Continuation of an Investigation into the Anaerobic Intrinsic Bioremediation of Whole Gasoline
R827015C018 Using Plants to Remediate Petroleum-Contaminated Soil
R827015C019 Biodegradation of Petroleum Hydrocarbons in Salt-Impacted Soil by Native Halophiles or Halotolerants and Strategies for Enhanced Degradation
R827015C020 Anaerobic Intrinsic Bioremediation of MTBE
R827015C021 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
R827015C022 A Continuation: Humate-Induced Remediation of Petroleum Contaminated Surface Soils
R827015C023 Data for Design of Vapor Recovery Units for Crude Oil Stock Tank Emissions
R827015C024 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells
R827015C025 A Continuation of Remediation of Brine Spills with Hay
R827015C026 Identifying the Signature of the Natural Attenuation of MTBE in Goundwater Using Molecular Methods and "Bug Traps"
R827015C027 Identifying the Signature of Natural Attenuation in the Microbial
Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and
"Bug Traps"
R827015C028 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
R827015C030 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
R827015C031 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
R827015C032 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
R830633 Integrated Petroleum Environmental Consortium (IPEC)
R830633C001 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells (Phase II)
R830633C002 A Continuation of Remediation of Brine Spills with Hay
R830633C003 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
R830633C004 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
R830633C005 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
R830633C006 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
R830633C007 Identifying the Signature of the Natural Attenuation in the Microbial Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and “Bug Traps”
R830633C008 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
R830633C009 Use of Earthworms to Accelerate the Restoration of Oil and Brine Impacted Sites
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.