WO2013104954A1

WO2013104954A1 - Method and system for testing oil spill dispersant effectiveness

Info

Publication number: WO2013104954A1
Application number: PCT/IB2012/050100
Authority: WO
Inventors: Maurice Bourrel; Marianna RONDON-GONZALEZ; Didier Lauranson; Sandrine LESCOULIE; Nicolas Passade-Boupat
Original assignee: Total Sa
Priority date: 2012-01-09
Filing date: 2012-01-09
Publication date: 2013-07-18

Abstract

This invention relates to a system and a method for testing oil spill dispersant effectiveness, in particular in the context of oil spill dispersants, more particularly marine oil spill dispersants. In one aspect, the invention relates to a system for testing the oil spill dispersing effectiveness of a dispersant, the system comprising: a)a vessel for containing a liquid; b)at least one injector, said injector being configured to dispense an adjustable flow of an oil-based fluid at the bottom of the vessel; and c)at least one of.a liquid turbidity assessment system comprising a laser beam emitting device and a detector, and 2.a liquid sampling system. In another aspect, the invention relates to a method for testing the oil spill dispersing effectiveness of a dispersant, comprising: a)dispensing an oil and a dispersant at the bottom of a vessel containing water under stirring; and b)at least one of a. assessing the turbidity as a function of time, b. measuring the average oil droplet size, c. measuring the hydrocarbon concentration, and d. assessing the color, of a water sub-layer located between the top 10% water layer and the bottom of the vessel.

Description

METHOD AND SYSTEM FOR TESTING OIL SPILL DISPERSANT

EFFECTIVENESS

FIELD OF INVENTION

[0001] This invention relates to a system and a method for testing oil spill dispersant effectiveness, in particular in the context of marine oil spill dispersants for sub-sea applications.

BACKGROUND OF THE INVENTION

[0002] When oil is spilled at sea, a small proportion will be naturally dispersed by the mixing action caused by waves. This process can be slow and proceed to only a limited extent for most situations. Dispersants are used to accelerate the removal of oil from the surface of the sea by greatly enhancing the rate of natural dispersion of oil and thus prevent it from coming ashore. Dispersed oil will also be more rapidly biodegraded by naturally occurring microorganisms. The rationale for dispersant use is that dispersed oil is likely to have less overall environmental impact than oil that persists on the surface of the sea, drifts and eventually contaminates the shoreline, where it can damage coastal habitats and resident wildlife.

[0003] Thus, any discharge of a significant amount of oil into the marine environment will trigger a response effort to recover or dissipate the spilled oil. Although mechanical recovery of the oil is the primary means of removing large quantities of spilled oil, application of chemical dispersants is an important supplementary measure for spills that spread over a wide area or create a large slick.

[0004] The development of modern dispersants began after the Torrey Canyon oil spill in 1967. Many lessons have been learned since that spill, and as a result, dispersants and application techniques in use today have become an integral part of responding to an oil spill. With the advent of the Macondo accident in the Gulf of Mexico in 2010, limitations of modern oil spill response techniques have become apparent. For example, the need to devise an appropriate response to adequately treat oil spills from a sea-floor oil gushers has become painfully obvious. One of the response efforts that emerged as being an important one is that of dispersing the oil before it reaches the surface of the ocean. Indeed, once on the surface, the wave and swell of the sea favour the formation of an oil/seawater emulsion, which in turn is more difficult to disperse by exiting dispersants. Research efforts are currently under to way to develop dispersants that are effective for sub-sea treatment of an oil spill, and methods of applying those dispersants.

[0005] The effectiveness of a particular dispersant is difficult to assess, partly because it depends on a variety of factors. Clearly, the composition of the dispersant product and the application system are important factors in determining the effectiveness of the dispersant. Other important factors are the composition and state of the oil being dispersed, the ratio of dispersant to oil, and the amount of mixing energy in the system. Oil composition can vary considerably, from light crude oils which will evaporate to a significant degree, to medium crude oils with different amounts of aromatics, saturates, resins and asphaltenic and polar compounds, to heavy crude oils and fuel products with lower volatility and higher viscosity. In addition, the oil can become emulsified with water, causing a significant increase in volume and viscosity.

[0006] The problem is even more preponderant in the case of dispersants meant for sub-sea treatment of oil-spill, because there are currently no standard method for reliably testing dispersants in conditions that would model or simulate a sub- sea treatment of an oil spill.

[0007] Many methods are reported in the literature aimed at evaluating the effectiveness of additives for surface dispersion of oil spills. Many governmental and academic laboratories have worked on this subject during the 80's and 90's decades (See Figure 1 for a Table summarizing the main methods known to date). However, to our knowledge, no tests have been reported to date concerning the efficiency evaluation for sub-sea applications of dispersants.

[0008] Accordingly, there remains a need for developing systems and methods for testing the effectiveness of dispersants in sub-sea treatment of oil spills. SUMMARY OF INVENTION

[0009] The present invention addresses this need by providing, in one aspect, a system for testing the oil spill dispersing effectiveness of a dispersant, the system comprising:

a) a vessel for containing a liquid;

b) at least one injector, said injector being configured to dispense an adjustable flow of an oil-based fluid at the bottom of the vessel; and c) at least one of

i. a liquid turbidity assessment system comprising a laser beam emitting device and a detector,

ii. a liquid sampling system.

[0010] In certain embodiments, the oil-based fluid may be an oil or a mixture of oil and a dispersant.

[0011] In certain embodiments, the injector is configured to dispense a dispersant in the vicinity of the flow of oil-based fluid.

[0012] In certain embodiments, the injector is in fluid connection with a reservoir containing the oil-based fluid.

[0013] In certain embodiments, the injector comprises an open ended hollow tube shaped into a hook comprising a straight portion and a hook portion, the straight end of the tube being in fluid connection with a reservoir containing the oil-based fluid, and the hook end of the tube being oriented toward the bottom of the vessel, so as to allow dispensing an adjustable flow of oil-based fluid out of the tip of the hook end and away from the straight portion of the injector.

[0014] In certain embodiments, the reservoir containing the oil-based fluid is a syringe.

[0015] In certain embodiments, the vessel contains a liquid, and the laser beam emitting device and the detector are positioned such that the detector can detect laser light transmitted through the liquid by the laser beam emitting device. [0016] In certain embodiments, the laser beam emitting device and the detector are positioned at a level falling below the surface of the liquid, so as to measure light transmitted through the top third fraction of the liquid in the vessel.

[0017] In certain embodiments, the system further comprises a stirring device, which may be a mechanical or magnetic stirring device.

[0018] In certain embodiments, the system further comprises a camera. The camera may be for performing colorimetric analysis of liquid samples.

[0019] In certain embodiments, the system further comprises a first camera for monitoring the surface of the liquid contained in the vessel, and a second camera for monitoring the color changes, and/or assessing the color, of the liquid contained in the vessel.

[0020] In another aspect, there is provided a method for testing the oil spill dispersing effectiveness of a dispersant, comprising:

a) dispensing an oil and a dispersant at the bottom of a vessel containing water under stirring; and

b) at least one of

i. assessing the turbidity as a function of time,

ii. measuring the average oil droplet size,

iii. measuring the hydrocarbon concentration, and

iv. assessing the color,

of a water sub-layer located between the top 10% water layer and the bottom of the vessel.

[0021] In certain embodiments, the oil and the dispersant are dispensed separately or as a mixture.

[0022] In certain embodiments, the oil and the dispersant are dispensed separately, and the dispersant is dispensed in the vicinity of the oil dispensing site.

[0023] In certain embodiments, the water is maintained at a temperature ranging from 2 to 15°C, preferably from 2 to 10°C, most preferably from 2 to 4°C. [0024] In certain embodiments, assessing the turbidity of the water layer as a function of time comprises measuring the fraction of light transmitted through the water layer from a laser beam emitting device, with a detector in optical alignment with the laser beam emitting device.

[0025] In certain embodiments, measuring the average oil droplet size of the water layer is performed with a laser diffractometry technique.

[0026] In certain embodiments, measuring the hydrocarbon concentration of the water layer comprises:

i. mixing a sample of the water layer with a chemical compound to form an emulsion,

ii. dissolving the emulsion in a suitable solvent to form a solution, and iii. measuring the quantity of hydrocarbon in the solution.

[0027] In certain embodiments, measuring the hydrocarbon concentration of the water layer comprises a liquid-liquid extraction with an oil selective solvent.

[0028] In certain embodiments, the step of measuring the quantity of hydrocarbon in the solution is performed with a total organic carbon analyzer.

[0029] In certain embodiments, assessing the color of the water layer is performed visually or with a colorimetric analyzer.

[0030] In certain embodiments, the method further comprises robotic integration, automation, semi automation or combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows a table summarizing the main methods known to date for testing the effectiveness of oil spill dispersants, and their corresponding operating conditions.

[0032] FIG. 2 is a schematic view of a system for testing oil spill dispersant effectiveness, according to one embodiment of the invention.

[0033] FIG. 3 is a schematic view of a system for testing oil spill dispersant effectiveness, according to another embodiment of the invention. [0034] FIG. 4 is a schematic view of the base of the system depicted in Figure 3, showing an exemplary embodiment how valve (1 1 ) and injector (1 ') may be assembled.

a) (15): hole 0 2 mm + welded inox tube 2 x 3 (dispersant injection inlet)

b) (16): hole 0 6 mm + welded inox tube 6 x 8 (oil injection inlet) c) (17): hole 0 4 mm + welded inox tube 4 x 6 (air injection inlet) d) (18): welded tube 0 24 mm for connecting to dynamic mixer (10) e) (19): tapped hole 0 6mm

f) (20): O-ring 0 5 mm

g) (19): 1 " NPT tapped holes for ¼ " NP male coupling for tubes with external 0 6, 8 or 3 mm

[0035] FIG. 5 is a graph showing the test results of a dispersant (dispersant A) using the method and system according to one embodiment of the invention, using a mixture of dispersant A and crude oil extracted from a subsea oil field, the mixture being dispersed in sea water at a rate of 1 ml/min during 2 min and analyzed over a 24 hour period at rest.

[0036] FIG. 6 is a graph showing the test results of another dispersant (dispersant B) using the method and system according to one embodiment of the invention, using a mixture of dispersant B and crude oil extracted from a subsea oil field, the mixture being dispersed in sea water at a rate of 1 ml/min during 2 min and analyzed over a 24 hour period at rest.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[0037] As noted above, there has been an increasing need for developing systems and methods for testing the effectiveness of dispersants in sub-sea treatment of oil spills. In one aspect, there is provided a system for testing the oil spill dispersing effectiveness of a dispersant, the system comprising:

a) a vessel for containing a liquid; b) at least one injector, said injector being configured to dispense an adjustable flow of an oil-based fluid at the bottom of the vessel; and c) at least one of

i. a liquid turbidity assessment system comprising a laser beam emitting device and a detector, and

ii. a liquid sampling system.

[0038] The term "oil" as used herein takes the conventional meaning given to the term in the petroleum extraction industry. It generally refers herein to crude oil extracted from petroleum fields like sub-sea oil fields; it could also refer to pipeline or tanker oil leakage. In preferred embodiments, it refers to crude oil extracted from sub-sea oil fields.

[0039] The dispersant to be tested may be any dispersant designed to be used in an oil spill response, for example when oil is spilled at sea. For example, the dispersant may be a liquid blend of surfactants (surface active agents) and solvents, designed to hasten breakup of oil slicks into fine droplets that disperse naturally in the sea. Dispersants are generally of three types: water-soluble dispersants; hydrocarbon solvent-based dispersants (typically having between 10 and 30 percent surfactant in a hydrocarbon solvent such as kerosene); and concentrated dispersants (typically having between 30 and 80 percent surfactant in oxygenated solvents or hydrocarbon solvents). All three types of dispersants may be applied neat (that is, undiluted) and, in addition, water-based dispersants and concentrated dispersants may be diluted with fresh water or seawater prior to application.

[0040] Advantageously, the vessel may be transparent. For example, it may be made of glass or a plastic material such as PVC. The vessel may be graduated so as to allow the user to readily estimate the quantity of liquid that is being poured into it. In certain embodiments, the vessel may be not transparent and include transparent windows.

[0041] Advantageously, the vessel may be a thermostated vessel. In other words, the temperature of the liquid contained in the vessel may be regulated by a thermostat. This may be accomplished for example by plunging in the vessel a loop allowing a thermally controlled liquid to circulate, or by immersing the vessel in a thermally controlled bath. In certain embodiments, the vessel and its contents may be maintained at a temperature ranging from 2 to 15°C, preferably from 2 to 10°C, most preferably from 2 to 4°C.

[0042] In certain embodiments, the liquid is water-based. Preferably, the liquid used is one that mimics the conditions at sea. In certain embodiments, the liquid may be tap water, salt water or sea water. Fine granular sodium chloride or table salt, non-iodized, may be used for making the salt water. Preferably, sea water may be used.

[0043] In certain embodiments, the vessel contains tap water, salt water or sea water.

[0044] Since the system is designed for use in conditions similar to the marine environment or in salt water, all of the metallic components and fittings are preferably in non-corrosive materials such as aluminium, bronze, brass, copper or galvanized steel and are designed for marine use or for use in conditions similar to the marine environment or in salt water. Non-metallic components are chosen preferably for their compatibility with the marine environment and with the chemicals of the dispersants to be tested with the system of the invention.

[0045] In certain embodiments, the oil-based fluid may be oil or a mixture of oil and the dispersant to be tested dispersant. Preferably, the oil may be crude oil, whether it is used separately or in a pre-mix with the dispersant. The oil/dispersant pre-mix may be prepared by adding the oil and the dispersant, and by mixing well by manual shaking or stirring. The dispersant to oil ratio may range from 1 :10 to 1 :1000, preferably 1 :20 to 1 :500, preferably 1 :30 to 1 :200. Thus, in certain embodiments, the oil-based fluid may be an oil/dispersant pre-mix, and the injector may be configured to dispense a mixture oil/dispersant.

[0046] In certain other embodiments, the oil-based fluid is oil, preferably crude oil, which is dispensed at the bottom of the vessel separately but simultaneously with the dispersant to be tested. For example, the injector may have a separate dispersant injection means configured to dispense the dispersant in the vicinity of the flow of oil-based fluid, for example in the plume of the oil-based fluid that is being dispensed from the injector.

[0047] In certain embodiments, the injector may be set vertically substantially in the centre of the vessel. By "substantially in the center" of the vessel, it is meant that the injector is placed in the inner area of the vessel that is the farthest from the lateral walls of the vessel.

[0048] In certain other embodiments, the injector may be in fluid connection with a reservoir containing the oil-based fluid.

[0049] In certain other embodiments, the injector may comprise an open ended hollow tube shaped into a hook comprising a straight portion and a hook portion, the straight end of the tube being in fluid connection with a reservoir containing the oil-based fluid, and the hook end of the tube being oriented toward the bottom of the vessel, so as to allow dispensing an adjustable flow of oil-based fluid out of the tip of the hook end and away from the straight portion of the injector.

[0050] In certain other embodiments, the reservoir containing the oil-based fluid has a pump attached thereto for adjusting the flow of oil-based fluid dispensed from the injector into the vessel. This provides the user with the ability to select between flow rates, and enhances the flexibility of the system to test dispersants in a wide variety of flow conditions. The user may select a desired flow rate by adjusting the setting of the pump connected to the reservoir. Selection of flow rate may depend on the thickness and viscosity of the oil, the water temperature, the water turbulence (stirring speed), the type and concentration of the dispersant, and the desired oil flow to be dispensed at the bottom of the vessel. The pump may be a manually, mechanically or electronically operated pump.

[0051] Thus, in exemplary embodiments, the injector may be hydraulically connected through a monitor and optionally through tubes or tubing to a source of pressurized oil-based liquid, which may optionally comprise a pressure manifold. The system may be powered by a centrifugal pump hydraulically connected on its output side to the pressure manifold and optionally hydraulically connected on its input side to an inlet manifold. The pump receives and pressurizes the oil-based liquid by pumping it into the pressure manifold whence it is conveyed through the monitor and thence to the injector.

[0052] In certain other embodiments, the reservoir containing the oil-based fluid may be a syringe. Preferably, it may be a syringe equipped with a speed- controlled piston so that the flow rate of the oil-based fluid may be controlled and adjusted at will. [0053] Turbidity

[0054] In certain other embodiments, the system is equipped with a device allowing the assessment of the turbidity of an aqueous medium, for example water turbidity. This may be accomplished, for example, with a laser beam emitting device and a detector in optical alignment with the laser beam emitting device. The principle is that the detector detects the light transmitted by the laser beam emitting device through the liquid contained in the vessel (i.e., water, oil and dispersant). Particles that may be present in the liquid held in the vessel will scatter the incoming light. Such may be the case, for example, if the oil dispensed at the bottom of the vessel form droplets, for example by action of the dispersant.

[0055] As it will be readily understood, the larger the droplet number is, the more intensively the light is scattered. The light transmission efficiency can be monitored as a function of time:

wherein l_t represents the transmitted light intensity at time t and l₀ represents the transmitted intensity in the absence of dispersed oil.

[0056] The ratio l_t/lo can be correlated to the size and number of the oil particles/droplets in suspension in the sample. The closer to 0 the ratio l_t/lo is, the more dispersed are the oil particles/droplets in the sample, and therefore the more effective the dispersant is. For example, an effective dispersant will drop the transmitted light by a factor 2 within 5 seconds.

[0057] In certain other embodiments, the laser beam emitting device and the detector are positioned outside of the vessel, such that the detector can detect laser light transmitted through the vessel by the laser beam emitting device. For example, the laser beam emitting device and the detector are positioned on diametrically opposite sides of the vessel walls.

[0058] In exemplary embodiments, the vessel contains a liquid (a mixture of water, oil and the dispersant being tested), and the laser beam emitting device and the detector are positioned such that the detector can detect laser light transmitted through the liquid by the laser beam emitting device.

[0059] One important aspect of the present invention is that, contrary to testing methods currently available in the art, the inventive system allows to test the oil spill dispersing effectiveness of a dispersant within the under water layers of the liquid contained in the test vessel (i.e., not at the liquid surface). This is important because the system allows to evaluate the effectiveness of dispersants for sub- sea applications, when current test systems allow little visibility in that regard.

[0060] Thus, advantageously, the laser beam emitting device and the detector may be preferably positioned at a level falling below the surface of the liquid, so as to measure light transmitted through the liquid sub-layers contained in the vessel. In exemplary embodiments, the laser beam emitting device and the detector may be preferably positioned at a level falling below the surface of the liquid, so as to measure light transmitted through the top third fraction of the liquid in the vessel.

[0061] The system may be computarized. As such, in exemplary embodiments, the system may further comprise a computer or processor running software for processing and analyzing the transmitted light. In preferred exemplary embodiments, the computarized system may include a data processing algorithm that allows the user to access directly a measure of the turbidity of the liquid medium, and evaluate the dispersing effectiveness of the tested dispersant.

[0062] When light having an intensity l'₀ enters the liquid medium (scattering light medium), and transmits for a distance y so as to be attenuated into l_t through the scattering liquid medium, the scattering phenomenon may be represented by the following equation: l_t/l Ό = exp (-xy)

[0063] The values l'₀ and y are known and are determined by the system parameters: l'₀ is the incident light entering the liquid medium, and y is the path crossed by the laser light through the liquid medium. The value y depends on the positioning of the laser beam emitting device and the detector on either side of the vessel containing the scattering liquid medium (mixture of water, oil and dispersant). This positioning is set by the user. Therefore, the user knows and actually chooses the value y.

[0064] The parameter τ is referred to as the turbidity (or "scattering parameter"). It corresponds to a scattering coefficient of the liquid medium, and is function to the number of particles "N" present in the liquid medium (scattering elements), and to the size of the particles.

[0065] Thus, the computarized system may include a data processing algorithm allowing to calculate the turbidity τ of the liquid medium according to the above equation.

[0066] The laser beam emitting device and the detector may each be mounted on a wheel gear assembly system such that vertical positioning of the laser beam emitting device and the detector may be adjusted at the desired height.

[0067] Liquid sampler

[0068] In exemplary embodiments, the liquid sampling system comprises any means for taking samples of the liquid medium contained in the vessel for purposes of analysis. This may take the form of a sampler cell that can be lowered into the liquid medium contained in the vessel at the desired height, depending on the depth of water layer the user wishes to sample. The sampler cell may be lowered toward to the bottom of the vessel to sample liquid near the oil and dispersant injection site, or at any one of possible intermediate points between below the liquid sample and the bottom of the vessel. Advantageously, the sampler cell will be lowered into the liquid medium at a level falling within the top third fraction of the liquid in the vessel, while remaining below the liquid surface. Once positioned at the desired height within the liquid medium, the cell may be allowed to fill with liquid medium, and may then be removed from the vessel for subsequent analysis.

[0069] In other exemplary embodiments, the liquid sampling system comprises at least one valve fitted on a lateral wall of the vessel, allowing to take a sample of liquid contained in the vessel. In exemplary embodiments, the liquid sampling system may comprise a plurality of valves interspersed vertically along a lateral wall of the vessel, allowing to take a plurality of samples of liquid contained in the vessel at different heights within the volume of liquid contained in the vessel.

[0070] The samples may then be analyzed for example for hydrocarbon content and for average oil droplet size. Embodiments concerning this aspect of the invention will be discussed infra in relation to the method for testing the oil spill dispersing effectiveness of a dispersant also provided within the context of the present invention.

[0071] Stirring device

[0072] In other exemplary embodiments, the system according to the present invention may further comprise a stirring device for stirring the liquid contents of the vessel. Preferably, the stirring device may be adjusted by the user at a desired speed. The stirring allows to test and compare dispersants under controlled conditions , even if these conditions are far from realistic sub-sea conditions (flow rate, currents, flux, ground swell, etc .). The stirring device may be a mechanical or magnetic stirring device.

[0073] Camera

[0074] In exemplary embodiments, the system may further comprise a camera, for example a digital camera. The camera may be used to record changes in the liquid medium aspect contained in the vessel as the oil-based liquid is dispensed via the injector, changes that can give indications as to the quality of the oil dispersion, and therefore as to the dispersing effectiveness of the dispersant. For example, the camera may be fitted for performing colorimetric analysis of liquid samples. Color changes, for example as a result of direct and indirect chemical or physicochemical reactions, have been developed for many years to aid the analytical chemist to measure qualitatively and/or quantitatively constituents of interest. These colorimetric methods can be automated such that instead of using the human eye to observe and assess the colorimetric properties, one can use a spectrometric system that is sensitive to the colorimetric process of interest. For example, high resolution digital colorimetry at pixel level for quantitative analysis may be used.

[0075] The system may thus be coupled to an analytical imaging approach to the quantitation of dispersed oil in the vessel liquid medium. The approach may use digital images of a series of standard dispersions of the oil used in the test (for example crude oil) in the presence of known dispersants, the dispersing effectiveness of which is also known and recorded. The analytical imaging approach may additionally involve processing of the aforementioned digital images with appropriate software to assign a numeric value to each standard in terms of color intensity. Each standard numeric value may then be attributed to a quantitated oil dispersion state (emulsion, slightly dispersed, well dispersed, totally dispersed (i.e. solution)), and allows the construction of a calibration graph.

[0076] Thus, the results recorded by the camera element may be compared with those standard values used to construct the calibration curves, to quantify the dispersion state of the liquid medium contained in the vessel, and therefore to quantify the dispersing effectiveness of the tested dispersant. In exemplary embodiments, the chemical imaging technique may be implemented with a commercially available digital camera and the public domain software ImageJ, developed by the National Institutes of Health and freely available for download on the Internet.

[0077] In certain embodiment, an image recognition software may be used that allows to distinguish shapes and contours.

[0078] In accordance with an embodiment of the present invention, the system comprising a camera, preferably a digital camera, allows to perform colorimetric analysis of liquids with a greater precision than is typically accomplished by systems relying on visual inspection of color changes.

[0079] In exemplary embodiments of the present invention, the system may perform colorimetric analysis of liquids in an automated way, thereby permitting the system to be placed in a fixed location to automatically or periodically perform measurements. That is, the system of the invention may automatically read and report the measurement without user intervention.

[0080] In exemplary embodiments of the present invention, the present system may comprise devices and methods for performing colorimetric analysis of fluid samples. In an exemplary embodiment, the device comprises one or more colorimetric sensors in one or more locations on and/or in the vessel of the inventive system.

[0081] In exemplary embodiments, the spacing and placement of the sensors may correspond to the sub-layers of the liquid medium contained in the vessel for which the user wants to characterize and assess the dispersing effectiveness of the dispersant tested.

[0082] Readings from each of the colorimetric sensors may be transmitted to a computational device which interprets the measurements and reduces them to estimates or quantification of the dispersing effectiveness of the dispersant. Thus, in exemplary embodiments, the camera may be connected to a computer and an image processing software.

[0083] In other exemplary embodiments, the system according to the present invention may further comprise a first camera for monitoring the surface of the liquid contained in the vessel, and a second camera for monitoring the color changes, and/or assessing the color, of the liquid medium contained in the vessel as described above. The first camera is useful for detecting the formation for example of an emulsion or an oil film at the surface of the liquid medium, which would be indicative of a poor effectiveness of the dispersant.

[0084] With reference to Figure 2, the system according to the present invention may comprise a hook-shaped injector (1 ) which is positioned vertically substantially at the centre of a vessel (3) filled with salt water. The vessel is equipped with a magnetic stirring bar (4) and is placed on a magnetic stirring plate (5). The straight end of the injector (1 ) is in fluid connection with a flow-controlled syringe (2) containing a mixture of oil and the dispersant to be tested. The system further comprises a liquid sampler cell (8) immersed in the liquid within the top third fraction of the liquid in the vessel. The system also comprises a liquid turbidity assessment system comprising a laser beam emitting device (7) and a detector (9). The system also comprises a first camera (6) for monitoring the surface of the liquid contained in the vessel, and a second camera (6') for performing colorimetric analysis of liquid samples and monitoring the color changes, and/or assessing the color, of the liquid medium contained in the vessel.

[0085] With reference to Figure 3, the system according to the present invention may comprise an injector (1 ') which is positioned vertically at the bottom of a vessel (3') filled with salt water. In exemplary embodiments, the injector (1 ') protrudes from the bottom of the vessel (3'), so as to model an oil spill from a sea- floor oil gusher (cf. Macondo accident). The injector (1 ') may be fitted with a dynamic mixer (10) allowing the pre-mixing of the oil with the dispersant to be tested, prior to dispensing the oil-based liquid from the injector (1 '). The dynamic mixer (10) may be in fluid connection with an oil inlet and a dispersant inlet allowing the introduction of oil and dispersant within the mixer (10). The vessel (3') may be advantageously a column, preferably a transparent PVC column, more preferably a graduated transparent PVC column. The column may have a height ranging from 1.50 to 3.00 m, for example 2.00 m, and a diameter ranging from 0.30 to 0.80 m, for example 0.50 m. The vessel (3') may be fitted with a purge valve (1 1 ) at the bottom of the vessel (3'), allowing to empty the vessel (3') when needed/desired. The valve 1 1 can also be used to feed the vessel with concentrated brine, which is then diluted with fresh water, thanks to valve 13, to the desired salt concentration. The vessel (3') may be fitted with a mechanical stirring device to mix oil and water. Alternatively, this can be achieved by circulating a flux of water at the bottom of the vessel thanks to valves 14 and 14'. Alternatively or simultaneously, a gas can be injected to form bubbles contributing to the agitation, for example through inlet 17 (cf. Figure 4). The gas can be air, nitrogen, methane, carbon dioxide etc The system further comprises a plurality of sampling valves (12) along the vertical wall of the vessel (3'). The valves (12) may be interspersed at regular intervals, for example, they can be 25 cm apart as shown on Figure 3. The valves (12) may be PVC valves preferably fitted with a rubber septum.

[0086] The system may also comprise (i) at least one set of liquid turbidity assessment system each set comprising a laser beam emitting device (7) and a detector respectively (9); and (ii) a camera (6') for performing colorimetric analysis of liquid samples and monitoring the color changes, and/or assessing the color, of the liquid medium contained in the vessel. In certain exemplary embodiments, the laser beam emitting device(s) (7), detector(s) (9), and/or camera (6') may be mounted on a wheel gear assembly system such that vertical positioning of the laser beam emitting device(s) (7), detector(s) (9), and/or camera (6') may be adjusted at the desired height. In certain exemplary embodiments, the system may comprise one set of liquid turbidity assessment system comprising one laser beam emitting device (7) and one detector respectively (9). In other exemplary embodiments, the system may comprise two sets of liquid turbidity assessment systems each comprising a laser beam emitting device (7) a detector (9).

[0087] The system may also comprise a purge valve (1 1 ) enabling the user to empty and clean the vessel after usage. [0088] In another aspect of the invention, there is provided a method for testing the oil spill dispersing effectiveness of a dispersant, comprising:

b) at least one of

i. assessing the turbidity as a function of time,

ii. measuring the average oil droplet size,

iii. measuring the hydrocarbon concentration, and

iv. assessing the color,

[0089] In exemplary embodiments, the oil and the dispersant are dispensed separately or as a mixture.

[0090] In exemplary embodiments, the oil and the dispersant are dispensed separately, and the dispersant is dispensed in the vicinity of the oil dispensing site.

[0091] In exemplary embodiments, the water is stirred with a mechanical or a magnetic stirrer.

[0092] In exemplary embodiments, the water is thermostated. For example, the water may be maintained at a temperature ranging from 2 to 15°C, preferably from 2 to 10°C, preferably from 2 to 4°C, the latter temperature range being the temperature range typically existing in deep ocean waters.

[0093] In exemplary embodiments, assessing the turbidity of the water layer as a function of time comprises measuring the fraction of light transmitted through the water layer from a laser beam emitting device, with a detector in optical alignment with the laser beam emitting device. In that regard, the reader will refer to any of the embodiments already discussed above for the system according to the present invention, which are explicitly applicable to the present method.

[0094] The step of measuring the average oil droplet size may first comprise a step of collecting a sample of the liquid (i.e., water containing oil and dispersant dispensed by the injector) contained in the vessel. This may be accomplished by a liquid sampler system as described above for the system according to the invention. A sample may be taken from any location in the volume of liquid contained in the vessel where the user chooses to assess the oil spill dispersing effectiveness. For example, a sample may be taken from the vicinity of the tip of the injector from which the oil-based liquid is being dispensed. In another example, a sample may be taken from the top third fraction of the volume of liquid contained in the vessel. Samples may be taken at different time intervals to monitor dispersing effectiveness over time. A plurality of samples may be taken from different locations in the volume of liquid contained in the vessel. For example, a plurality of samples may be taken at different space intervals along a vertical axis in the volume of liquid, to monitor how the dispersing effectiveness of the dispersant being tested may vary within the liquid volume from the site of injection to the surface of the liquid.

[0095] The step of measuring the average oil droplet size may be carried out by any means known in the art for measuring particle size. Many different techniques have been devised for determining particle size, but for a wide range of industries laser diffraction has become the preferred choice. Laser diffraction, alternatively referred to as Low Angle Laser Light Scattering (LALLS), can be used for the non- destructive analysis of wet or dry samples, with particles in the size range 0.02 to 2000 micron and has inherent advantages which make it preferable to other options for many different materials. In exemplary embodiments, measuring the average oil droplet size of the water layer is performed with a laser diffractometry technique. For example a Malvern Instrument™ laser diffractometry may be used.

[0096] In exemplary embodiments, a measured average droplet size smaller than or equal to 2 to 3 micrometers may be indicative of good dispersing effectiveness of the oil spill dispersant that is being tested by the method according to the invention.

[0097] In exemplary embodiments, measuring the average oil droplet size may be carried out.

[0098] In exemplary embodiments, measuring the hydrocarbon concentration of the water layer comprises: a. mixing a sample of the water layer with a chemical compound to form an emulsion,

a. dissolving the emulsion in a suitable solvent to form a solution, and b. measuring the quantity of hydrocarbon in the solution.

[0099] For example, the method may use the process described in PCT Application N° PCT/EP2012/050039 filed on January the 3rd 2012 by TOTAL S.A. which is incorporated herein by reference in its entirety.

[00100] In a first step, a chemical compound may be added to a water layer sample in order to form an emulsion of water and hydrocarbons. The chemical compound may be a solution comprising one or more surfactant compounds. In a particularly simple embodiment, the chemical compound may also be an alkaline solution, such as a sodium hydroxide solution. Indeed, a base (such as soda) may react with the naphthenic acids present in the hydrocarbons and form surfactant compounds in situ. Sodium hydroxide may be replaced with another base such as potash, ammonia or sodium carbonate etc.

[00101] On the other hand, if instead (or additionally), a surfactant compound is used, in particular for weakly acidic oils, the surfactant compound(s) may be advantageously selected so as not to perturb the final step of measuring the amount of hydrocarbons. For example, when the step of measuring the quantity of hydrocarbons is carried out by UV absorbance, the surfactant compounds are preferably essentially non-absorbent in the UV spectrum.

[00102] The chemical compound may be advantageously mixed with the water layer sample until the emulsion is obtained, either manually or preferably by using mechanical mixing means (e.g., stirrer with paddles, magnetic stirrer, vortex stirrer, or others).

[00103] The nature and the amount of the chemical compound may be adapted according to the nature of the water layer sample so as to allow formation of a homogeneous emulsion. The concentration of the chemical compound may vary between 0.05% and 3% by weight. The emulsion that is formed is typically of the oil in-water type, and therefore should have good fluidity. By observing it visually under stirring, it is then possible to appreciate its homogeneity.

[00104] In a second step, a sample of the emulsion may be taken out (the emulsion sample being representative of the global emulsion), and may then be dissolved in a solvent common to both water and hydrocarbons to form a solution. By sampling the emulsion, it is possible to limit the amount of solvent used while obtaining a sufficiently diluted hydrocarbon solution so as to be able to carry out a measurement of the hydrocarbon concentration while avoiding saturation of the measurement apparatus. Depending on the solvent, the rate of dilution by the solvent may vary from 1 to 10.

[00105] It is considered that a product is a solvent for water and for hydrocarbons (i.e., a solvent common to both water and hydrocarbons) when, at room temperature, and at ambient pressure, the solubility of water in this product is greater than or equal to 30% by volume and the solubility of the hydrocarbons in this product is greater than or equal to 30% by volume.

[00106] If the water contains salts, at a concentration greater than typically 20 g/L, solubilization of the water in the solvent may become insufficient and separation of the phases may occur. The method may comprise an additional step in order to adapt to this situation. This additional step comprises diluting the sample with distilled water so as to reduce the salinity to a value of less than 20 g/L. The term "salt" refers to any salt contained in the aqueous phase of the sample (for example, but not limited to, NaCI, CaCI₂, MgCI₂, ...).

[00107] The method of the invention may further include a step of determining the amount of salt in the aqueous phase of the sample, prior to the step of dilution with distilled water.

[00108] A highly efficient solvent common to both water and hydrocarbons is tetrahydrofurane. However it is possible to use other solvents such as dimethylsulfoxide, dimethylformamide, dimethylacetamide etc., this list not being limiting,

[00109] If mineral solid particles are still present in the solution, they generally decant easily because of the disappearance of the aqueous phase in which these particles are generally suspended and are therefore no longer a nuisance for the measurement. Alternatively, provision may be made for filtration, if required. The gas that may be present is generally also discharged during this step.

[00110] In a third step, a direct measurement of the amount of hydrocarbons in the solution is carried out. A particularly simple method comprises carrying out an absorbance measurement of the solution in the UV range, by using a spectrometer. This typically involves preliminarily calibration of the spectrometer with samples of hydrocarbons in the solvent at various concentrations. By completely analyzing the UV spectrum of the hydrocarbon, it is possible to select wavelengths producing different absorbances. Depending on whether the samples are strongly concentrated or strongly diluted, wavelengths may be selected, which produce low or strong absorbances, respectively, allowing enhanced accuracy.

[00111] In exemplary embodiments, the step of measuring the quantity of hydrocarbon in the solution is performed with a total organic carbon analyzer. Total organic carbon (TOC) refers to the amount of carbon bound in an organic compound and is often used as a non-specific indicator of water quality or cleanliness. The analysis may be performed according to well known methods in the art. For example, the total organic carbon analysis may be carried out with an analyzer functioning on the basis of an oxidizing combustion and an infra-red analysis. Typically, modern TOC analyzers perform this oxidation by several processes, including high temperature combustion, high temperature catalytic oxidation (HTCO), photo-oxidation alone, thermo-chemical oxidation, photochemical oxidation or electrolytic oxidation. Preferably, high temperature combustion is used. Typically, the samples are combusted at 1 ,350 °C in an oxygen-rich atmosphere. All carbon present converts to carbon dioxide, flows through scrubber tubes to remove interferences such as chlorine gas, and water vapor, and the carbon dioxide is measured either by absorption into a strong base then weighed, or using an Infrared Detector. Most modern analyzers use non- dispersive infrared (NDIR) for detection of the carbon dioxide.

[00112] In exemplary embodiments, assessing the color of the water layer is performed visually or with a colorimetric analyzer. Visual inspection of the color of the liquid in the vessel can give indications to the trained professional as to the quality of the oil dispersion, and thus the effectiveness of the dispersant being tested. For example, these colors can vary from light brown to dark brown, and from light grey to black. The darker the color is, the better the dispersion is. In the case of a bad dispersion, oil arrives at the surface in big drops and the solution stays clear. In the case of an average dispersion, the drops are littler and they disperse. The solution is more or less dark depending on the number of drops so depending on the fineness of the drops. In the case of a good dispersion, all the oil is dispersed. The solution is very dark, it is almost homogeneous.

[00113] In exemplary embodiments, the method further comprises robotic integration, automation, semi automation or combinations thereof.

[00114] In certain preferred embodiments, the system and method of the present invention may be used in a standardized test for evaluating the effectiveness of an oil spill dispersant, particularly in sub-sea setting. A standard test would be useful to establish a baseline performance parameter so that dispersants can be compared, a given dispersant can be compared for effectiveness on different oils, and at different oil weathering stages, and batches of dispersant or oils can be checked for effectiveness changes with time or other factors.

[00115] As the reader will appreciate, dispersant effectiveness varies with oil type, sea energy, oil conditions, salinity, and many other factors. Accordingly, test results from a standard test based on the system and method described in the present application would form a baseline, but would not to be taken as the absolute measure of performance at sea. Actual field effectiveness could be more or less than this value. Nevertheless, a standard test based on the system and method according to the present invention is expected to have superior predictive value in assessing the effectiveness of dispersants in responding to a sub-sea oil spill, over existing standard tests. The decision to use or not use a dispersant on an oil spill would not be based solely on this or any other laboratory test method, but the results from a standard test based on the system and method according to the present invention would have a lot more weight than any other existing laboratory standard test for making that decision.

[00116] [00117] Example 1

[00118] The method of the invention was carried out to test the oil dispersing effectiveness of two dispersants: dispersant A (Figure 5) and dispersant B (Figure 6).

[00119] Each experiment (dispersant A and B, respectively) was carried out using a system according to that depicted in Figure 3. Sea water was used as the liquid in the vessel, and a mixture of dispersant and crude oil was dispersed at the bottom of the vessel at a rate of 1 ml/min during 2 min and analyzed over 24 hours at rest. Sea water have a salinity between 25g/l to 50g/l, typically 32g/l.

[00120] As shown in Figure 5, that the incident light is completely transmitted to t=t0 and then falls very rapidly to almost zero: the oil immediately blocks the transmission of light. Over a long period of time, the transmitted light increases slightly. This is due to oil rising to the surface.

[00121] For concentration measurements, the water/oil mixture is sampled out of a tap/valve located in the middle of the beaker. The valve is located at the height of 8.5 cm +/- 0.5 cm, the total height of the breaker is 17 cm. The 40 ml samples are typically extracted from the vessel for particle size and concentration measurement. The efficiency of dispersion is calculated as the ratio between the amount of oil found in the samples (by UV method) over the mount of oil injected.

[00122] The reader will refer to all the embodiments described above and herein for the system of the invention, for practicing the method according to the present invention. The embodiments related to the system according to the invention are applicable mutadis mutandis to the method according to the invention. Likewise, the embodiments related to the method according to the invention are applicable mutadis mutandis to the system according to the invention.

[00123] It should be noted that different embodiments of the invention may incorporate different combinations of the foregoing, and that the invention should not be construed as limited to embodiments that include all of the different elements. Various other objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.

[00124] While the foregoing has described and illustrated aspects of various embodiments of the present invention, those skilled in the art will recognize that alternative components and techniques, and/or combinations and permutations of the described components and techniques, can be substituted for, or added to, the embodiments described herein. It is intended, therefore, that the present invention not be defined by the specific embodiments described herein, but rather by the appended claims, which are intended to be construed in accordance with the well- settled principles of claim construction, including that: each claim should be given its broadest reasonable interpretation consistent with the specification; limitations should not be read from the specification or drawings into the claims; words in a claim should be given their plain, ordinary, and generic meaning, unless it is readily apparent from the specification that an unusual meaning was intended; an absence of the specific words "means for" connotes applicants' intent not to invoke 35 U.S.C. §1 12 (6) in construing the limitation; where the phrase "means for" precedes a step or manipulation "function," it is intended that the resulting means- plus-function element be construed to cover any, and all, implementation(s) of the recited "function"; a claim that contains more than one means-plus-function element should not be construed to require that each means-plus-function element must be a structurally distinct entity.

Claims

CLAIMS We claim:

1 . A system for testing the oil spill dispersing effectiveness of a dispersant, the system comprising:

a. a vessel for containing a liquid;

b. at least one injector, said injector being configured to dispense an adjustable flow of an oil-based fluid at the bottom of the vessel; and

c. at least one of

ii. a liquid sampling system.

2. The system of claim 1 , wherein the vessel is transparent.

3. The system of claim 1 or 2, wherein the vessel contains tap water, salt water or sea water.

4. The system of any one of claims 1 to 3, wherein the oil-based fluid is oil or a mixture of oil and a dispersant.

5. The system of any one of claims 1 to 3, wherein the injector is configured to dispense a dispersant in the vicinity of the flow of oil-based fluid.

6. The system of any one of claims 1 to 5, wherein the injector is set vertically substantially in the centre of the vessel.

7. The system of any one of claims 1 to 6, wherein the injector is in fluid connection with a reservoir containing the oil-based fluid.

8. The system of any one of claims 1 to 6, wherein the injector comprises an open ended hollow tube shaped into a hook comprising a straight portion and a hook portion, the straight end of the tube being in fluid connection with a reservoir containing the oil-based fluid, and the hook end of the tube being oriented toward the bottom of the vessel, so as to allow dispensing an adjustable flow of oil-based fluid out of the tip of the hook end and away from the straight portion of the injector.

9. The system of claim 5 or 6, wherein the reservoir containing the oil-based fluid has a pump attached thereto for adjusting the flow of oil-based fluid dispensed from the injector into the vessel.

10. The system of claim 9, wherein the pump is a manually, mechanically or electronically operated pump.

1 1 . The system of any one of claims 5 to 8, wherein the reservoir containing the oil-based fluid is a syringe.

12. The system of claim 1 , wherein the laser beam emitting device and the detector are positioned outside of the vessel, such that the detector can detect laser light transmitted through the vessel by the laser beam emitting device.

13. The system of claim 12, wherein the laser beam emitting device and the detector are positioned on diametrically opposite sides of the vessel walls.

14. The system of claim 12 or 13, wherein the vessel contains a liquid, and the laser beam emitting device and the detector are positioned such that the detector can detect laser light transmitted through the liquid by the laser beam emitting device.

15. The system of claim 14, wherein the laser beam emitting device and the detector are positioned at a level falling below the surface of the liquid, so as to measure light transmitted through the top third fraction of the liquid in the vessel.

16. The system of any one of claims 12 to 15, further comprising a computer or processor running software for processing and analyzing the transmitted light.

17. The system of claim 1 , wherein the liquid sampling system is at least one valve fitted on the lateral wall of the vessel, allowing to take a sample of liquid contained in the vessel.

18. The system of claim 1 , wherein the liquid sampling system comprises a plurality of valves interspersed vertically along the lateral wall of the vessel, allowing to take a plurality of samples of liquid contained in the vessel at different heights within the volume of liquid contained in the vessel.

19. The system of any one of claims 1 to 18, further comprising a stirring device.

20. The system of claim 19, wherein the stirring device is a mechanical or magnetic stirring device.

21 . The system of any one of claims 1 to 20, further comprising a camera.

22. The system of claim 21 , wherein the camera is for performing colorimetric analysis of liquid samples.

23. The system of claim 21 or 22, wherein the camera is connected to a computer and an image processing software.

24. The system of any one of claims 1 to 23, further comprising a first camera for monitoring the surface of the liquid contained in the vessel, and a second camera for monitoring the color changes, and/or assessing the color, of the liquid contained in the vessel.

25. A method for testing the oil spill dispersing effectiveness of a dispersant, comprising:

a. dispensing an oil and a dispersant at the bottom of a vessel containing water under stirring; and

b. at least one of

i. assessing the turbidity as a function of time, ii. measuring the average oil droplet size, iii. measuring the hydrocarbon concentration, and iv. assessing the color,

of a water layer located between the top 10% water volume and the bottom of the vessel.

26. The method of claim 25, wherein the oil and the dispersant are dispensed separately or as a mixture.

27. The method of claim 25, wherein the oil and the dispersant are dispensed separately, and the dispersant is dispensed in the vicinity of the oil dispensing site.

28. The method of claim 25, wherein the water is stirred with a mechanical or a magnetic stirrer.

29. The method of claim 25, wherein the water is maintained at a temperature ranging from 2 to 4°C.

30. The method of claim 25, wherein assessing the turbidity of the water layer as a function of time comprises measuring the fraction of light transmitted through the water layer from a laser beam emitting device, with a detector in optical alignment with the laser beam emitting device.

31 . The method of claim 25, wherein measuring the average oil droplet size of the water layer is performed with a laser diffractometry technique.

32. The method of claim 25, wherein measuring the hydrocarbon concentration of the water layer comprises:

a. mixing a sample of the water layer with a chemical compound to form an emulsion,

b. dissolving the emulsion in a suitable solvent to form a solution, and

c. measuring the quantity of hydrocarbon in the solution.

33. The method of claim 32, wherein the step of measuring the quantity of hydrocarbon in the solution is performed with a total organic carbon analyzer.

34. The method of claim 25, wherein assessing the color of the water layer is performed visually or with a colorimetric analyzer.

35. The method of any one claims 25 to 34, wherein the method further comprises robotic integration, automation, semi automation or combinations thereof.