Isotope molecular species markers for fluid resources or pollutants

Abstract

Systems and methods are provided for chemically tagging dry natural gas and other fluids. In one example, at least 1 ppbv of a first isotopic species of a first hydrocarbon is added to the dry natural gas as a chemical marker. The first isotopic species has at least three deuterium atoms. Some embodiments described herein provide for the addition of one or more chemical markers to a fluid and subsequent identification of the one or more chemical markers in the fluid. The method can be used to associate information associated with the one or more chemical markers to the fluid.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 362,867, titled "ISOTOPOLOGUE MARKER FOR FLUID", which is incorporated herein by reference.

Background Art

[0002] Background Many different operators process fluids such as natural gas, crude oil, water, and carbon dioxide. Often, as a result of shipping or storing these fluids, a mixture of fluids from various operators may be obtained. Once fluids are mixed, it can be difficult or impossible to determine which operator supplied the fluid and in what quantity. For example, natural gas is often transported from producers to consumers via a network of pipelines. Many different operators can supply natural gas to the same pipeline network and storage facilities. It is difficult to determine which operator's gas is present in a given pipeline or storage facility.

[0003] Manufacturers and processors of natural resources are also required to adopt environmentally considerate technologies and devices in order to minimize the impact of their operations on the environment. For example, natural gas producers need to minimize the environmental emissions of fossil fuels during the extraction / production, processing, and / or transmission of natural gas. However, it is difficult to distinguish between environmentally considerate participants who adopt appropriate resources and management and those who neglect to do so, especially when most of such resources are indiscriminately mixed at some point during transportation to vendors and users in the natural resources space.

Summary of the Invention

Means for Solving the Problems

[0004] Brief Description Some embodiments described herein provide the addition of one or more chemical markers to a fluid and the subsequent identification of one or more chemical markers in the fluid. This method can be used to associate information associated with one or more chemical markers with a fluid. Any desired information can be associated with a marker, and by extension, the fluid in which the marker is contained, such as the fluid supplier, whether the fluid meets certain standards (e.g., some standards made to ensure environmentally sustainable operations), whether the fluid meets the specifications for pipeline contents, or whether the fluid originates from a particular oil / gas field or geographical area.

[0005] A chemical marker may be a unique molecule or a combination of two or more molecules in a unique ratio. For example, a chemical marker may be one or more isotopic molecular species of a component of the main fluid in question or of a chemically similar compound. For example, a chemical marker for methane (CH4) or dry natural gas may be one or more isotopic molecular species of methane, e.g., CDH2, CD2H, CD3H, and / or CD4, and / or one or more isotopic molecular species of related compounds, e.g., isotopic molecular species of ethane (e.g., C2DH5, C2D2H4, C2D3H3, C2D4H2, C2D5H, and / or C2D6), and / or isotopic molecular species of propane (e.g., C3DH7, C3D2H6, C3D3H5, C3D4H4, C3D5H3, C3D6H2, C3D7H, and / or C3D8). The chemical marker may be one of those molecules, or a combination of such molecules in a specific ratio.

[0006] One object of the present invention is to identify fluids that may be mixed with other fluids of the same general properties. For example, dry natural gas (or some other fluid) supplied by a first manufacturer may be mixed with dry natural gas (or other fluid) supplied by a second manufacturer. The fluid in question may be any other natural resource (e.g., crude oil, propane, etc.) or pollutant (e.g., carbon dioxide, carbon monoxide, sulfuric acid, etc.).

[0007] Another object of the present invention is to provide an apparatus and method for generating chemical markers.

[0008] Another object of the present invention is to provide an apparatus and method for detecting the presence and amount of chemical markers in a fluid.

[0009] The drawings only illustrate exemplary embodiments and should not be considered limiting in scope. The exemplary embodiments will be described in more specific and detail using the attached drawings. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram of an example system for transporting fluids.

[0011] [Figure 2] Figure 2 shows a chromatograph of an example of a chemically pure (CP) grade methane sample, demonstrating that trace amounts of ethane can be separated using CP technology.

[0012] [Figure 3] Figure 3 is a chromatograph of another example of the sample shown in Figure 3, obtained by SIM selection of per-deuterated ethane.

[0013] [Figure 4] Figure 4 shows the calibration curve for perdeuterated ethane in methane.

[0014] [Figure 5] Figure 5 is a block diagram of an example system for synthesizing fluid markers. [Modes for carrying out the invention]

[0015] Detailed explanation Figure 1 is a block diagram of a system 100 for transporting fluids. The system 100 may include a number of suppliers 102 that supply fluids to a network of pipes 104. The network 104 delivers the fluids to one or more destinations 106. The fluids may be any fluids that are desirable to transport in gaseous or liquid form, such as dry natural gas, wet natural gas, crude oil, water, carbon dioxide, ethane, or propane. Each supplier 102 may be any suitable operator involved in supplying or transporting fluids to or within the network 104, such as a manufacturer, processor, refiner, or wholesaler. One or more destinations may be any suitable operator receiving the fluids, such as a power plant, industrial plant, local government, processing facility, refiner, transport swap point, or fluid storage facility. The network of pipes 104 may include one or more pipes of any suitable size or design for transporting fluids, including regional and interstate pipelines.

[0016] Each supply line 108 transports fluid from each supplier 102 to the network of pipes 104. In one example, only fluid from a single supplier 102 is included in each supply line 108. The fluid from each supplier 102 in each supply line 108 may be mixed with fluid from other suppliers 102 in the network of pipes 104. That is, the network of pipes 104 may contain a mixture of fluids originating from multiple suppliers 102 (for example, a mixture of dry natural gas).

[0017] In one example, each supplier 102 may process the fluid before supplying it to the network 104 (for example, before supplying the fluid to a regional or interstate pipeline). This processing can be done to separate the components of the fluid and / or to modify the fluid to a quality suitable for introduction into the network 104 (for example, a regional or interstate pipeline). In an example where the fluid is dry natural gas, supplier 102 may receive wet natural gas from, for example, one or more oil fields, storage facilities, and / or transport vehicles, and process the wet natural gas to separate heavy hydrocarbons (e.g., ethane, propane, etc.) from methane, as well as remove non-hydrocarbon gases as needed. The product of the processing is a gas that is primarily methane and is known as dry natural gas (also called pipeline-quality natural gas). The dry natural gas is then supplied to the network 104 for consumption by one or more destinations. Regional and interstate pipeline managers often provide specifications for the dry natural gas transported within those pipelines, and suppliers 102 ensure that, through their own processing, they produce dry natural gas that meets the specifications of the pipelines through which the gas is transported.

[0018] Before the fluid from supplier 102 is introduced into network 104 (i.e., before the fluid is mixed with fluids supplied by other suppliers 102), one or more chemical markers may be added to the fluid. Chemical markers can be used as indicators, which are detected in the fluid and can be used to indicate something about the fluid. Markers can indicate something of interest, and a list identifying each marker, along with the marker and associated information, can be kept in any suitable form (e.g., in a written or electronic table) for marker detection, as discussed below. Examples of information that a marker may indicate include, but are not limited to, the fluid supplier 102, the standards the fluid meets (e.g., pipeline standards, or standards related to environmentally sustainable manufacturing methods), or the quality of the fluid, whether the fluid meets the pipeline contents specifications, or whether the fluid originates from a particular oil / gas field or geographical area. As described above, markers can indicate that the fluid possesses certain properties or meets certain standards. For example, if the fluid meets a first industry standard, such as the standards for responsible production and processing of natural gas, the marker may be added to any fluid regardless of its source. Such markers can then be detected in the fluid to determine whether the fluid (and, if necessary, what percentage of the fluid) meets the relevant standards. Other information can also be associated with the marker.

[0019] As discussed below, each marker may be unique among the markers added to network 104 so that each marker can be detected independently in the fluid. As an example of a unique marker that identifies a unique supplier 102, a first unique marker can be added to the fluid in the first supply line 108 from the first supplier 102, and a second unique marker can be added to the fluid in the second supply line 108 from the second supplier 102. The first unique marker can be associated with the first supplier 102 and the second unique marker can be associated with the second supplier 102 so that the fluid in network 104 can be analyzed to detect whether the first and / or second markers are present, and thus to determine whether gas from the first and / or second suppliers 102 is present. The first and second unique markers may be composed of different molecules, or different sets of molecules, or a set of the same molecules in different ratios. If markers from different suppliers are made using different ratios of the same set of molecules, detection will involve an evaluation of the amount of each of the different molecules, along with deconvolution calculations to separate the amounts contributed by each molecule present. Thus, the markers present can be identified by determining what ratios and amounts of the markers, when mixed, will result in the amount of each molecule present.

[0020] Chemical markers may be added to the fluid so that the markers become and remain part of the fluid for later detection within the fluid. The chemical composition of the marker can be selected such that the marker stays with the fluid while the fluid is stationary (e.g., during storage) and moves with the fluid while the fluid is flowing (e.g., during transport via a pipeline).

[0021] Each marker injection station 110 can be placed in each supply line 108 to add one or more markers to the fluid. The marker injection station 110 may have any suitable configuration, such as being part of an exhaust station.

[0022] A centralized database or operator can be established for the purpose of establishing markers and assigning (associating) markers to specific operators 102 (such as specific suppliers), fluids meeting certain specifications (e.g., some specifications created to ensure environmentally sustainable operations), fluids derived from specific oil fields / gas fields or geographical regions, etc. The centralized operator may also be a supplier of certified marker input stations 110 for use by operator 102 to add its own markers to its fluids. The centralized operator can restrict the assignment of markers to operator 102 based on predefined criteria such as verification of compliance with certain environmentally conscious specifications defined by the centralized operator.

[0023] One or more marker detectors 112 can be placed at one or more locations within system 100 to detect markers in the fluid. For example, one or more marker detectors 112 can be provided in a gas storage facility supplied by network 104, or in multiple supply lines 108, to determine the presence and / or amount of an accepted fluid associated with a particular marker. As another example, marker detectors 112 can be provided at a compression station, at a consumer's location, or at a city gate. As another example, power generation station 106 may have a marker detector 112 for detecting markers in the received fluid.

[0024] Detector 112 can use any suitable method for detecting markers in the fluid. In one example, detector 112 uses suitable analytical techniques such as a combination of gas chromatography and mass spectrometry (GC-MS) for detecting and optionally quantifying markers in the fluid. Mass spectrometry can be used to quantify low concentrations of markers. Gas chromatography can be used to separate the marker from other components as much as possible to improve the sensitivity of the MS detector to the marker. Any suitable device can be used, and specific examples are shown below.

[0025] As already mentioned, chemical markers can be associated with information, and the identification of chemical markers in a fluid can be used to link that information to the fluid. Once one or more markers are identified in the fluid, the information associated with those markers can be linked to the fluid to identify, for example, which business operator 102 is supplying the fluid and / or what standards (e.g., specifications) the fluid meets. In one example, the detector 112 can analyze the fluid occasionally (e.g., regularly) or frequently to provide data about the fluid's contents. In another example, the detector 112 can analyze the fluid frequently to provide continuous data about the fluid's contents.

[0026] The system 100 shown in Figure 1 is an example of a system for labeling fluids such as natural gas that are mixed with other fluids in a storage facility such as a network of pipes 104. In other examples, the fluids may be supplied or mixed in storage (e.g., in artificial or natural structure containers) or in transport (e.g., in containers that can be installed in trucks, trains, ships, etc.). In such other systems, markers may be added to the fluid before it is mixed with other fluids. In some examples, markers may be added to a fluid that is already a mixture from multiple suppliers, including before that mixture is further mixed with other fluids. Such markers may be added to identify regional mixtures of fluids and can be used in addition to markers that identify individual suppliers 102. Markers may be added to a fluid for any desired reason at any point during the life of the fluid, as long as each marker is uniquely detectable.

[0027] The chemical composition of a marker and the specific amount of the marker added to the fluid can be selected so that the marker is detectable as an artificially occurring amount of a particular chemical composition. That is, for a marker to be definitively identifiable, its chemical composition must be present in the fluid in amounts exceeding the normal (e.g., naturally occurring) amounts of the chemical substance. The specific amount of the marker required to exceed the normal amounts of the chemical substance is determined by the chemical composition of the marker and the possible / predicted chemical composition in the fluid. In some examples, isotopic molecular species are naturally occurring in small amounts in most fluids, so isotopic molecular species of a molecule are used as molecules for markers. Because they are present in small amounts, small amounts of the molecule are required to exceed the normal (e.g., naturally occurring) amounts. In certain examples, the isotopic molecular species is a deuterated form of the molecule, where a deuterium atom replaces a hydrogen atom in the molecule.

[0028] In some examples, the chemical composition of each marker can be selected so that it can be detected by the detector 112 and specifically distinguished from other chemical markers. For example, if the detector uses chromatography to identify some or all of the markers, the chemical composition of each marker can be selected so that each marker yields a specific chromatographic signal. In some examples, a specific chromatographic signal can be achieved by selecting molecules with different retention times, for example, retention times separated by at least 10 seconds. In some examples, multiple different techniques can be used to detect the marker molecules, so a given marker does not need to be specifically identifiable by a single technique, as long as the combination of techniques used makes the marker specifically identifiable.

[0029] In some examples, the chemical composition of the marker can be selected, and the marker may be added using a method that allows for the determination of the amount and / or percentage of fluid corresponding to the marker after the fluid has been mixed with other fluids that do not have the same marker. For example, it may be desirable to know not only whether a particular fluid of business operator 102 is present in the composition, but also how much of that fluid of business operator 102 is present in the composition. To achieve this, a chemical marker can be selected that is specifically identifiable by detector 112 and that detector 112 can also measure the amount of the marker present. The amount may be absolute or relative so that the amount of the marker relative to other markers is determined. In such examples, the step of adding the marker to the corresponding fluid (e.g., to the fluid of the first business operator 102 before mixing) may be measured so that the amount of marker added corresponds to the amount of the corresponding fluid present. The amount of marker added may be maintained at a constant ratio to the amount of fluid present. For example, a first marker corresponding to the first business operator 102 can be added so that the first marker 102 is present in the fluid of the first business operator at an amount of 1 volume ppm (ppmv). The detector 112 can then determine the amount of fluid from the first operator 102 in the composition based on the amount of the first marker detected. That is, if the first marker is detected at an amount of 1 ppmv, 100% of the composition is the fluid from the first operator. If the first marker is detected at an amount of 0.5 ppmv, 50% of the composition is the fluid from the first operator. While this example uses a concentration of 1 ppmv, any appropriate amount can be used. To enable the amount of the marker to correspond to the amount of its corresponding fluid, the chemical composition of the marker can be selected so that it is deterministically diluted in the composition (e.g., in the same proportion or ratio as its corresponding fluid). For example, if 50% of the composition consists of fluid derived from the first operator 102 having the first marker, the first marker is selected so that it is present in the composition at an amount that is 50% of the level to which it is added. Other methods of addition and detection can also be used.

[0030] As discussed above, chemical markers may contain combinations of two or more molecules (e.g., isotopic molecular species) in a predetermined ratio. For example, a 1:1 molar (or volume) mixture of C2D6 and C2H3D3 can be added to dry natural gas at a concentration of 1000 ppbv (500 ppbv each). Other ratios of C2D6 and C2H3D3, such as 1:5, 1:3, 1:2, 2:3, 3:2, 3:1, or 5:1, can also be used. By using chemical markers that are multiple isotopic molecular species in predetermined ratios, a specific fingerprint can be formed. In some examples, a mixture of multiple such predetermined ratios of two or more isotopic molecular species can be used as a marker, and the mixture of these ratios is selected so that even if multiple such markers are present in a single fluid, their mixtures can subsequently deconvolve. Furthermore, by using multiple isotopic molecular species in predetermined ratios, a ratiometric method can be provided for detecting the amount of the marker and its corresponding fluid present.

[0031] To determine which markers are present in the fluid and, if necessary, the amount of markers present, the detector 112 can perform mass spectrometry on the fluid to determine which molecules used as markers are present in the fluid. It can provide a set of information corresponding to the molecular weight of each molecule used as a marker. For example, if the molecules used as markers consist of C2D6 and C2D4H2, the set of information would include approximately 36 for C2D6 and approximately 34 for C2D4H2. The detector 112 analyzes the output of the mass spectrometry to determine whether molecules with molecular weights of approximately 36 and approximately 34 have been detected. In one example, molecules with molecular weights within the set are detected if the area under the curve can be reliably integrated for the molecular weights within the set. The detector 112 can then determine which markers are present based on which molecules have been detected. For example, if each marker is a single molecule, the detection of molecules with molecular weights corresponding to the set of marker molecules is the detection of the markers. In another example, if each marker is a predetermined ratio of multiple molecules, the detector 112 can deconvolve the results to determine which markers are present. Such deconvolution can be performed using a linear programming algorithm that takes as input data the amount of each relevant molecule detected in the fluid using mass spectrometry, along with information about each marker, the molecules constituting the marker, and the ratios of those molecules. The linear programming algorithm then calculates and outputs a set of one or more markers (e.g., a set of one or more ratios of the molecules corresponding to each marker) that constitutes the amount of detected molecules, and optionally the amount. This output identifies the markers present in the fluid. A calibration curve may be provided for each molecule used as a marker, which shows the correlation between the area under the detection curve from mass spectrometry for a particular molecular weight (obtained by integration) and the amount of the molecule present. The detector 112 can determine the amount of the molecule present by comparing the area obtained for a certain molecular weight with the calibration curve for that molecular weight.

[0032] Figure 2 shows an example of chromatography of a sample containing ethane (C2H6) and perdeuterated ethane (C2D6) in methane, using a PLOT column and a 300 μL injection volume apparatus. As shown, the CH4 peak elutes in approximately 3.4 minutes, while the C2H6 peak has a retention time of approximately 4.6 minutes. The concentration of ethane in the sample was 10.3 ppmv in chemically pure methane, which, once compared to the calibration curve, is SIM m / z 30(C2H6 + This can be determined from the area of ​​the peak (A30=141280). C2D6 at 573 ppbv with a retention time of 4.6 minutes is also present in this sample. Figure 3 shows the detected SIM at m / z=36(C2D6). + This is a chromatograph showing the profile from the sample when set to ). As shown, a much smaller C2D6 peak is observed despite co-elution with a much larger ethane peak, and its area can be quantified. The C2D6 concentration is consistent with the value obtained when the area of ​​the A36 peak is compared to the calibration curve. Due to variability in instrument performance, each instrument is individually calibrated, and a unique calibration curve is created for each analyte.

[0033] Figure 4 shows examples of calibration curves for various concentrations of C2D6 in chemically pure methane in the range of 50–1000 ppbv. White circles and error bars indicate the mean and standard deviation of three measurements at each concentration. Linear fitting to the data with a correlation coefficient of 0.9997 is also shown. MSD was used in SIM mode with m / z=36. The table below shows the measured values ​​included in the calibration curve. [Table 1] This calibration curve demonstrated excellent linear fitting to the data, good reproducibility in any given measurement, and quantitative detection (LOQ) down to 50 ppbv. The curve has a slope of 14.6 ± 0.13 and a y-intercept of -37.2 ± 61.2. The quantitative expression of this fitting is A36 / 14.6 = [C2D6](ppbv). The detection limit is approximately half of this value, approximately 25 ppbv. While the use of larger injection volumes (>300 μL) and splitless injection may be considered, the most stable performance was observed with a 0.5:1 split. Splitting occurs when the analyte gas is mixed with the carrier gas in the mixing chamber before introduction into the column. Splitless means that such pre-mixing does not occur. Without splitting, local pressure cannot function, resulting in insufficient separation. In this example, 150 μL of helium was mixed with 300 μL of sample in a 0.5:1 split.

[0034] In some cases, the chemical composition of a marker can be selected so that the marker does not significantly alter the chemical properties of the fluid. This can be achieved by selecting a marker with chemical properties similar to those of molecules already present in the fluid. In this way, a marker can be added without significantly affecting the properties of the fluid, for example, without affecting the fluid's energy efficiency. In one example, the marker molecule is an isotopic molecular species of a molecule or type of molecule that is typically present in the fluid. The molecule (e.g., ethane) or type of molecule (e.g., hydrocarbon) in which the marker is an isotopic molecular species is ideally present at relatively low concentrations or not present at all in fluids where molecules have not been intentionally introduced. For example, it is preferable that the molecules constituting the marker are naturally present in the fluid at concentrations of less than about 1000 ppmv, more preferably less than about 100 ppmv, and most preferably less than about 10 ppmv, or 1 ppmv. In cases where the fluid is a gas, the concentration is measured as a volume percentage of the fluid (e.g., 10 ppmv). In cases where the fluid is a liquid, the concentration can be measured as a mass percentage of the fluid. For example, each marker molecule is added at a concentration greater than approximately 0.1 ppbv, for example, between 0.1 ppbv and 1000 ppmv. For example, molecules may be added at concentrations greater than approximately 0.1 ppbv, such as 0.25 ppbv, 0.5 ppbv, 1 ppbv, 2.5 ppbv, 5 ppbv, 10 ppbv, 25 ppbv, 50 ppbv, 100 ppbv, 250 ppbv, 500 ppbv, 1 ppmv, 2.5 ppmv, 5 ppmv, 10 ppmv, 25 ppmv, 50 ppmv, 100 ppmv, 250 ppmv, 500 ppmv, or 1000 ppmv. For the liquid being labeled, the units used herein (including the concentrations above) are expressed in mass fraction parts per unit (e.g., ppb, ppm) instead of volume parts per unit (e.g., ppbv, ppmv). This means, for example, that the above concentration for a liquid exceeds approximately 0.1 ppb, for example, between 0.1 ppb and 1000 ppm.

[0035] In some cases, the chemical composition of a marker can be selected so as not to violate the requirements of the fluid. For example, there may be industry standards for the composition of dry natural gas, in which case the marker would be selected to be an acceptable additive.

[0036] In one example, the fluid is natural gas, and the marker molecule is an isotopic molecular species of hydrocarbons, such as an alkane or alkene. Some exemplary alkanes and alkenes have 1 to 3 carbon atoms (e.g., per deuterated ethane, per deuterated ethylene, per deuterated propane, per deuterated propene). Examples of molecules that can form isotopic molecular species include methane, ethane, propane, butane, ethylene, propylene, or butene. Since natural gas is mainly composed of hydrocarbons, using a hydrocarbon isotopic molecular species as the marker means that the marker does not significantly alter the chemical properties of the gas. Alternatively, the marker may be various molecules naturally occurring in natural gas, such as carbon dioxide, nitrogen, hydrogen sulfide, or helium. Natural gas may contain low concentrations of alkane isotopic molecular species. In such cases, the amount of the particular isotopic molecular species used is selected to be higher than the natural abundance of the isotopic molecular species discussed below.

[0037] In some examples, the marker molecule is a deuterium-based isotope molecular species of hydrocarbon. This could be, for example, a deuterium-based isotope molecular species of methane containing one or more of CD4, CD3H, CD2H2, CDH3, and / or a deuterium-based isotope molecular species of ethane, such as C2D6, C2H2D4, C2H3D3, etc. Such isotope molecular species contain deuterium ( 2 One or more hydrogen atoms substituted with H or D 1 It has H, protium, or simply H. In other examples, the isotopic molecular species may be carbon-based isotopes (for example, 13-carbon isotopes). Such carbon-based isotopic molecular species may or may not contain deuterium isotopes. A preferred chemical marker for use with methane is C2H6. A preferred chemical marker for carbon dioxide is CD4.

[0038] The selected molecules to be used as isotopic molecular species markers, either alone or in combination with other molecules, may naturally exist in small amounts in the fluid. In this environment, isotopic molecular species can be used at concentrations well above their naturally occurring levels so that high levels of isotopic molecular species can be artificially identified as markers (or components of a marker if multiple molecules are used as a single marker). It may be advantageous to use an isotopic molecular species with more isotopes (e.g., more deuterium atoms) as the molecule in the marker, because the more isotopes there are in an isotopic molecular species, the lower the natural abundance of that isotopic molecular species. Hydrocarbon isotopic molecular species with a small number of deuterium atoms (e.g., one deuterium atom) may naturally exist in small amounts in the fluid. However, the more deuterium atoms there are in an isotopic molecular species, the less naturally that isotopic molecular species exists in the fluid. For example, C2D2H4 is naturally present in natural gas at a rate of approximately 24 ppbv or less, and C2D3H3 is approximately 3.17 e -12 They exist naturally in natural gas in the following proportions. In one example, the molecule in the marker has at least three deuterium atoms to ensure that the molecule exists naturally in the fluid in sufficiently low amounts. In another example, the molecule in the marker has at least four deuterium atoms to further ensure that the molecule exists naturally in the fluid in sufficiently low amounts. In hydrocarbons with more than three carbon atoms (e.g., butane), at least six deuterium atoms may be present in the molecule of the isotopic molecular species used as a marker. In another example, at least half of the hydrogen atoms in the marker molecule are replaced by deuterium atoms. That is, the molecule in the marker has at least N / 2 deuterium atoms, where N is the number of hydrogen atoms in the corresponding molecule. For ethane, since ethane has six hydrogen atoms, this means that the marker molecule will have at least three deuterium atoms (i.e., including C2D3H3, C2D4H2, C2D5H, and C2H6). The table below lists the natural abundances of deuterium-based isotopic molecular species of methane in natural gas. [Table 2]

[0039] The combination of gas chromatograph and mass spectrometer may be optimized for the separation of methane and ethane, for example, by using a Shimadzu TQ8030 to detect ethane isotopic molecular species. Mass spectrometry detection of trace amounts of isotopic molecular species in natural gas is highly sensitive and therefore can lead to clear identification and quantification of isotopic molecular species. For example, the separation of trace amounts of ethane, propane, and butane (including their isotopic molecular species) from methane can be achieved using a 50-meter Al2O3 / KCl porous layer hollow tube (PLOT) column, and selective ion mode (SIM) can be used. Oven temperatures between 100°C and 0°C can be used, and improved separation can be obtained at lower temperatures (e.g., 10-50°C, preferably 20-40°C, more preferably 25-35°C, most preferably 30°C). Different detection parameters and instruments may be used for different fluids or marker molecules.

[0040] Any other combination of ethane isotopic molecular species may also be used in specific ratios. Furthermore, one hydrocarbon isotopic molecular species may be used with another hydrocarbon isotopic molecular species in specific ratios; for example, ethane isotopic molecular species may be used with C3D9. The table below shows other exemplary markers along with their relevant physical data. [Table 3]

[0041] Figure 5 is a block diagram of Method 500, which is an example of a method for producing isotopic molecular species of an alkane (e.g., C2D6) that can be used as a natural gas marker. Method 500 in Figure 5 can economically produce isotopic molecular species of an alkane using a two-step reaction based on ordinary water (H2O), heavy water (D2O), and carbon monoxide (CO). The two steps 502 and 504 of this method operate in succession, with the product from the first step 502 being sent to the second step 504. The first step 502 of this method 500 includes a step of electrolysis with respect to the heavy water and, optionally, to ordinary water, by applying power to split deuterium and hydrogen, if present, from oxygen. Ordinary water and heavy water may be pumped from storage tanks and continuously added.

[0042] The oxygen product from this first stage 502 may be discharged into the atmosphere or contained for some other use. The deuterium and, optionally, dihydrogen from the first stage 202 are sent to the second stage 204 of process 200. Carbon monoxide is the input to the second stage 204, which uses a catalyst such as platinum and a heater to reduce the alkane isotopic molecular species with CO and the deuterium / hydrogen input. The second stage of the reaction produces a mixture of the alkane isotopic molecular species, heavy water, and, optionally, ordinary water.

[0043] A series of condensers operating at extremely low temperatures can be used to separate a mixture of isotopic molecular species, heavy water, and ordinary water (506). The heavy water and ordinary water can be collected and recycled back into the inputs of the first stage 202. The isotopic molecular species contained in the products of the second stage 504 can be controlled by adjusting the ratio of heavy water to ordinary water input into the first stage 502, along with the temperature and pressure used in the second stage 504. For example, if ordinary water is not input into the first stage 502 (i.e., only heavy water is input), only fully deuterated alkanes (e.g., CD4 and C2D6) will be produced from the second stage 504. The ratio of ordinary water input into the first stage 502 determines the ratio of deuterated alkanes produced in the second stage 504.

[0044] In certain examples, 99% pure heavy water may be introduced into the first stage 502 at a rate of 305 mL / day. Separated oxygen is a byproduct and is produced from the first stage 502 at a rate of, for example, 15.7 cubic feet / day. In some examples, carbon monoxide may be supplied from a gas cylinder and introduced into the second stage 504 at a continuous rate of approximately 8.7 cubic feet / day. In this example, C2D6 is produced from the separator at a rate of approximately 5 cubic feet / day. Produced at a rate of 5 cubic feet / day, C2D6 can be used to label 100 million cubic feet of dry natural gas at a concentration of 50 ppbv. The two-stage process can be operated at low pressure (e.g., 20 psig or less) to efficiently produce C2D6.

[0045] In one example, other isotopic species of ethane can be produced using the same two-step reaction as in Method 200, except that the heavy water introduced into the first step is replaced with a mixture of heavy water and ordinary water (H2O). The mixture of heavy water and ordinary water yields a mixture of methane, ethane, and their isotopic species, including, for example, C2D6 and C2H2D4, which are produced by the two-step reaction. The ratio of heavy water to ordinary water can be varied to vary the statistical mixture of isotopic species in the product. The ratio of heavy water to ordinary water can be selected so that the product from a given reaction yields an intrinsically identifiable mixture of isotopic species that can be used as a marker or modified to be used as a marker. Different ethane isotopic species can be separated and used as individual markers or combined with each other in intrinsically identifiable ratios as described above. In either case, the markers produced may be compressed in a cylinder for transport to a suitable marker input station 110.

[0046] Similar techniques can be used to marker other fluids such as carbon dioxide (CO2), crude oil, and water. In one example, an isotopic molecular species of methane (e.g., CD4) can be used as a chemical marker for carbon dioxide. Other examples of molecules that can be used alone or in combination as markers for carbon dioxide are listed in the table below. [Table 4-1] [Table 4-2]

[0047] In the example where the fluid to be labeled is crude oil, exemplary molecules to be used in the marker include hydrocarbons in the C8-C14 range (8-14 carbon atoms), including both straight-chain and branched-chain hydrocarbons and / or molecules containing fluorine or chlorine. Isotope-labeled paraffins and alcohols can be used as labels for water or crude oil. In another example, isotopic molecular species of one or more aromatic compounds are used as markers for crude oil. The proposed reaction process described above for deuterated ethane can also be adapted to synthesize long-chain isotope-labeled paraffins and alcohols for labeling liquid products such as crude oil and water.

[0048] The two-step reaction in any of the above methods may use a catalyst-filled, temperature- and pressure-controlled stainless steel tubular reactor. The two steps may be carried out at the same or different pressures, for example, in the range of 1 to 50 bar, more preferably 1 to 20 bar, or most preferably 1 to 5 bar. In one example, the first step is carried out at a pressure of less than about 3 bar, and the second step is carried out at a pressure of more than about 3 bar. In another example, the second step is maintained at a temperature between about 100 and 1200 degrees Celsius, for example, between about 200 and 400 degrees Celsius. The temperature can be controlled by an electric heater and a control system that monitors the temperature at multiple locations. The reactor length and diameter are sized to match the design flow rate, along with the amount of catalyst.

[0049] Markers produced by any of the methods described herein may be compressed and then injected into a desired fluid or stored in a cylinder for transport or later use. The present invention provides, for example, the following items: (Item 1) Dry natural gas comprising a first isotopic molecular species of a first hydrocarbon at a concentration of at least 1 ppbv, wherein the first isotopic molecular species has at least three deuterium atoms. (Item 2) The dry natural gas described in item 1, wherein the first hydrocarbon is an alkane. (Item 3) The dry natural gas described in item 2, wherein the alkane is ethane. (Item 4) The first isotopic molecular species is C 2 D 6 This refers to dry natural gas as described in item 3. (Item 5) Dry natural gas according to any one of items 1 to 4, comprising at least 1 ppbv of a second isotopic molecular species of a second hydrocarbon other than methane, wherein the second isotopic molecular species has at least three deuterium atoms and is different from the first isotopic molecular species. (Item 6) The dry natural gas described in item 5, wherein the second hydrocarbon is an alkane. (Item 7) The dry natural gas described in item 6, wherein the alkane is one of ethane or propane. (Item 8) The second isotopic molecular species is C 2 H 2 D 4 or C 3 D 8 One of them is dry natural gas, as described in item 7. (Item 9) The second isotopic molecular species is per deuterated propane (C 3 D 9 ) Dry natural gas as described in item 5. (Item 10) A method comprising the step of adding a first isotopic molecular species in an amount of at least 1 ppbv to dry natural gas, wherein the first isotopic molecular species has at least 3 deuterium atoms. (Item 11) The method according to item 1, wherein the first hydrocarbon is an alkane. (Item 12) The method according to item 2, wherein the alkane is ethane. (Item 13) The first isotopic molecular species is C 2 D 6 The method described in item 3. (Item 14) A method according to any one of items 10 to 13, comprising the step of adding at least 1 ppbv of a second isotopic molecular species of a second hydrocarbon other than methane to the dry natural gas, wherein the second isotopic molecular species has at least three deuterium atoms and is different from the first isotopic molecular species. (Item 15) The method according to item 14, wherein the second hydrocarbon is an alkane. (Item 16) The method according to item 15, wherein the alkane is one of ethane or propane. (Item 17) The second isotopic molecular species is C 2 H 2 D 4 or C 3 D 8 One of them is the method described in item 16. (Item 18) The second isotopic molecular species is per deuterated propane (C 3 D 9 The method described in item 14. (Item 19) Steps to accept wet natural gas; The steps include: processing the wet natural gas to produce the dry natural gas; The method according to any one of items 10 to 18, comprising the step of supplying the dry natural gas to a first storage facility, wherein the first storage facility includes a pipeline for transporting dry natural gas from a plurality of processing plants or a container for receiving dry natural gas from a plurality of processing plants, wherein the step of adding at least 1 ppb of a first isotopic molecular species includes the step of adding the at least 1 ppb before supplying the dry natural gas to the first storage facility. (Item 20) A step of analyzing dry natural gas by a combination of gas chromatography and mass spectrometry, wherein the analysis is performed downstream of the location where at least 1 ppb of the first isotopic molecular species was added; The steps include determining, based on the analysis, whether the first isotopic molecular species is present in the analyzed dry natural gas, and The method described in item 19, including the method described in item 19. (Item 21) The method according to item 20, wherein the determination step includes deconvolving the results from the analysis to identify a plurality of unique chemical markers having a predetermined ratio of at least two different molecules. (Item 22) Heavy water (D 2 The steps include: continuously supplying O) to the first reactor; The steps include: electrolyzing the heavy water to produce deuterium and dioxygen; The steps include: continuously supplying the deuterium from the first reactor to the second reactor; The steps include: continuously supplying carbon monoxide (CO) to the second reactor; The deuterium and carbon monoxide are passed over the catalyst C 2 D 6 A step of obtaining a continuous product including; From the other components of the product of the second reactor described above, C 2 D 6 The step of separating and C 2 D 6 A method for manufacturing. (Item 23) The method according to item 22, wherein the catalyst is platinum, cobalt, nickel, ruthenium, or a mixture thereof. (Item 24) The method according to either item 22 or 23, further comprising the step of separating heavy water from the product of the second reactor and using the separated heavy water in the first reactor.

Claims

1. A natural gas comprising at least 1 ppbv of a first isotopic molecular species of a first hydrocarbon other than methane, wherein the first isotopic molecular species has at least three deuterium atoms.

2. The natural gas according to claim 1, wherein the first hydrocarbon is an alkane.

3. The natural gas according to claim 2, wherein the alkane is ethane.

4. A natural gas according to claim 1, comprising at least 1 ppbv of a second isotopic molecular species of a second hydrocarbon other than methane, wherein the second isotopic molecular species has at least three deuterium atoms and is different from the first isotopic molecular species.

5. The natural gas according to claim 4, wherein the first hydrocarbon is a first alkane and the second hydrocarbon is a second alkane.

6. The natural gas according to claim 5, wherein the first alkane is ethane and the second alkane is one of ethane or propane.

7. A method comprising the step of adding a first isotopic molecular species of a first hydrocarbon other than methane in an amount of at least 1 ppbv to natural gas, wherein the first isotopic molecular species has at least three deuterium atoms.

8. The method according to claim 7, wherein the first hydrocarbon is an alkane.

9. The method according to claim 8, wherein the alkane is ethane.

10. The method according to claim 7, comprising the step of adding at least 1 ppbv of a second isotopic molecular species of a second hydrocarbon other than methane to the natural gas, wherein the second isotopic molecular species has at least three deuterium atoms and is different from the first isotopic molecular species.

11. The method according to claim 10, wherein the first hydrocarbon is a first alkane and the second hydrocarbon is a second alkane.

12. The method according to claim 11, wherein the first alkane is ethane and the second alkane is one of ethane or propane.

13. Steps to accept wet natural gas; The steps include: processing the aforementioned wet natural gas to produce dry natural gas; The method according to claim 7, comprising the step of supplying the dry natural gas to a first storage facility, wherein the first storage facility includes a pipeline for transporting dry natural gas from a plurality of processing plants or a container for receiving dry natural gas from a plurality of processing plants, the step of adding at least 1 ppbv of a first isotopic molecular species, the step of adding the at least 1 ppbv before supplying the dry natural gas to the first storage facility.

14. The steps include analyzing natural gas using a combination of gas chromatography and mass spectrometry; The method according to claim 7, comprising the step of determining, based on the analysis, whether the analyzed natural gas contains at least 1 ppbv of a first isotopic molecular species of a first hydrocarbon other than methane, wherein the first isotopic molecular species has at least three deuterium atoms.

15. The method according to claim 14, wherein the determination step includes deconvolving the results from the analysis to identify a plurality of unique chemical markers having a specified ratio of at least two different molecules.

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