METHODS AND DEVICES FOR DETECTING MERCURY ISOTOPES IN OIL-GAS SOURCES

• US 20200132649A1
• Filed: 04/24/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Petrochina Company Limited (China National Petroleum Corporation)
• Original Assignee: Petrochina Company Limited (China National Petroleum Corporation)
• Inventors: ZHU, Guangyou, TANG, Shunlin
• Granted Patent: US 11,119,085 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 21/6404 Atomic fluorescence
• CPC Class Codes: G01N 33/0045 Hg
• CPC Class Codes: G01N 33/225 Gaseous fuels, e.g. natural gas
• CPC Class Codes: G01N 33/2835 Specific substances contained in the oils or fuels

Abstract

The invention relates to a method and a device for detecting mercury isotopes in an oil-gas source. The device includes at least one enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, an enrichment-absorption system for mercury in natural gas and at least one secondary purification-enrichment system for mercury; the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock comprises three air-absorption bottles, a pyrolysis/cracking system, five impact samplers, and a vacuum pump, which are connected in series by pipe lines; and the enrichment-absorption system for mercury in natural gas includes five impact samplers connected in series, wherein the first impact sampler is connected to the natural gas outlet from the natural gas well and the last impact sampler is connected to the cumulative gas flow meter.

Claims

1. A device for detecting mercury isotopes in an oil-gas source, comprising:

at least one enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, an enrichment-absorption system for mercury in natural gas and at least one secondary purification-enrichment system for mercury;

the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock comprises three air-absorption bottles, a pyrolysis/cracking system, five impact samplers, and a vacuum pump, which are connected in series by pipe lines;

the enrichment-absorption system for mercury in natural gas comprises five impact samplers connected in series, wherein the first impact sampler is connected to the natural gas outlet from the natural gas well and the last impact sampler is connected to the cumulative gas flow meter;

the secondary purification-enrichment system for mercury comprises a nitrogen-gas cylinder, a collection bottle with potassium permanganate absorption liquid in which mercury isotope is absorbed, and a secondary enrichment-absorption bottle containing an acidic aqueous potassium permanganate solution, which are connected in series by pipe lines, wherein the secondary purification-enrichment system further comprises a stannous-chloride storage bottle, which is connected to a pipe line between the nitrogen-gas cylinder and the collection bottle with potassium-permanganate absorption liquid via a peristaltic pump and through a pipe line.

2. The device according to claim 1, wherein the five impact samplers in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock are, in the connection order, respectively a first impact sampler containing a stannous chloride solution, an empty impact sampler, a third impact sampler containing an acidic potassium permanganate solution, a fourth impact sampler containing an aqueous sodium hydroxide solution and an fifth impact sampler containing a silica gel, wherein the first impact sampler is connected via a pipe line to the pyrolysis/cracking system;

and

the five impact samplers in the enrichment-absorption system for mercury in natural gas are, in the connection order, respectively an empty sixth impact sampler and a seventh impact sampler containing an acidic aqueous potassium permanganate solution, an eighth impact sampler containing an acidic aqueous potassium permanganate solution, a ninth impact sampler containing an acidic aqueous potassium permanganate solution, and a tenth impact sampler containing a silica gel;

wherein the three air-absorption bottles in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock are, in the connection order, respectively a first air-absorption bottle containing aqua regia, a second air-absorption bottle containing aqua regia and a third air-absorption bottle containing an aqueous sodium hydroxide solution, and the pyrolysis/cracking system is connected to the third air-absorption bottle through a pipe line.

3. The device according to claim 1, wherein the pyrolysis/cracking system comprises a pyrolysis chamber and a cracking chamber connected in series with pipe lines;

said pyrolysis chamber is connected via a pipe line to the last air-absorption bottle in the connection order in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, and the cracking chamber is connected via a pipe line to the first impact sampler in the connection order in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock.

4. The device according to claim 1, wherein each of the three air-absorption bottles and five impact samplers in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, and the five impact samplers in the enrichment-absorption system for mercury in natural gas is a borosilicate glass bottle and is provided with a gas inlet and a gas outlet at the respective top thereof, wherein the gas inlet communicates with the inner space of the bottle through a glass tube which is provided inside the bottle and extends to the lower part of the bottle.

5. The device according to claim 4, wherein,

in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, three air-absorption bottles are connected in series, with the gas outlet of the former air-absorption bottle connected to the gas inlet of the latter air-absorption bottle via a pipe line, the gas inlet of the first air-absorption bottle communicating with air, and the gas outlet of the last air-absorption bottle connected to the pyrolysis/cracking system by a pipe line;

the five impact samplers are connected in series, with the gas outlet of the former impact sampler connected to the gas inlet of the latter impact sampler by a pipe line, the gas inlet of the first impact sampler connected via a pipe line to the pyrolysis/cracking system, and the gas outlet of the last impact sampler connected to the vacuum pump by a pipe line;

in the enrichment-absorption system for mercury in natural gas, the five impact samplers are connected in series, with the gas outlet of the former impact sampler connected to the gas inlet of the latter impact sampler by a pipe line, the gas inlet of the first impact sampler connected to the natural gas outlet of the natural gas well by a pipe line, and the gas outlet of the last impact sampler connected to the cumulative gas flow meter by a pipe line.

6. The device according to claim 1, wherein the secondary purification-enrichment system further comprises a mercury-trapping gold tube which is disposed on a pipe line connecting the nitrogen-gas cylinder and the collection bottle with potassium permanganate absorption liquid, and approximates to the gas outlet of the nitrogen-gas cylinder.

7. The device according to claim 2, wherein the acidic aqueous potassium permanganate solutions in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock and the enrichment-absorption system for mercury in natural gas have a potassium permanganate concentration of 1 w/v %, and an acid concentration of 10 v/v %, the acid is sulfuric acid;

and the acidic aqueous potassium permanganate solutions in the secondary purification-enrichment system for mercury have a potassium permanganate concentration of 4 w/v %, and an acid concentration of 10 v/v %, the acid is sulfuric acid;

wherein each of the stannous chloride solution in the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock and the secondary purification-enrichment system independently has a concentration of 15 to 25 w/v %; and

the aqueous sodium hydroxide solution in the fourth impact sampler has a concentration of 30 w/v %.

wherein the aqueous sodium hydroxide solution in the third air-absorption bottle has a concentration of 30 w/v %

8. The device according to claim 1, further comprising a detector for detecting the total mercury content of the mercury enriched in the secondary enrichment-absorption bottle and a detector for detecting the composition of stable isotopes of the mercury enriched in the secondary enrichment-absorption bottle.

9. The device according to claim 8, wherein the detector for detecting the total mercury content of the mercury enriched in the secondary enrichment-absorption bottle is a cold atomic fluorescence mercury detector, and the detector for detecting the composition of stable isotopes of the mercury enriched in the secondary enrichment-absorption bottle is a multi-collector inductively-coupled plasma mass spectrometer.

10. The device according to claim 1, comprising two enrichment-absorption systems for mercury in crude oil/hydrocarbon source rock, and three secondary purification-enrichment systems for mercury, wherein the two enrichment-absorption systems for mercury in crude oil/hydrocarbon source rock are respectively used for the enrichment and absorption for mercury in the crude oil and the enrichment and absorption for mercury in the hydrocarbon source rock, and the three secondary purification-enrichment systems for mercury are respectively used for the secondary purification and enrichment for mercury in crude oil, the secondary purification and enrichment for mercury in hydrocarbon source rock, and the secondary purification and enrichment for mercury in natural gas.

11. A method for detecting mercury isotopes in an oil-gas source, comprising the steps of:

(1-a) primary enrichment for mercury isotopes in crude oil;

heating a crude oil sample to perform pyrolysis and cracking until the crude oil sample is completely cracked, absorbing the gas released by heating the crude oil sample with an acidic aqueous potassium permanganate solution to enrich the mercury element in the crude oil sample, and collecting all of the acidic potassium permanganate solutions in which the mercury element is enriched in step (1-a);

(1-b) purification and enrichment for mercury isotopes in crude oil;

reducing the mercury absorbed in the step (1-a) to mercury vapor with a stannous chloride solution, and then purifying and enriching the mercury vapor by using an acidic aqueous potassium permanganate solution;

(1-c) detection for mercury isotopes in crude oil;

detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (1-b) to determine the total mercury content and the composition/content of stable mercury isotopes therein;

(2-a) primary enrichment for mercury isotopes in hydrocarbon source rock;

pulverizing a hydrocarbon source rock sample to 200 mesh, heating to 600°

C., subjecting to pyrolysis and cracking until the petroleum in the hydrocarbon source rock sample is completely cracked, absorbing the gas released by heating the petroleum with an acidic aqueous potassium permanganate solution to enrich the mercury element from petroleum in the hydrocarbon source rock sample, and collecting all of the acidic potassium permanganate solutions in which the mercury element is enriched in step (2-a);

(2-b) purification and enrichment for mercury isotopes in hydrocarbon source rock;

reducing the mercury absorbed in the step (2-a) to mercury vapor with a stannous chloride solution, and then purifying and enriching the mercury vapor by using an acidic aqueous potassium permanganate solution;

(2-c) collecting mercury isotopes in the hydrocarbon source rock by acid digestion;

(2-d) detection for mercury isotopes in crude oil;

detecting the acidic potassium permanganate solutions in which the mercury vapor is enriched in steps (2-b) and (2-c) to determine the total mercury content and the composition/content of stable mercury isotopes therein;

(3-a) primary enrichment for mercury isotopes in natural gas;

subjecting natural gas to a three-stage cascading absorption with acidic aqueous potassium permanganate solutions, and collecting all of the acidic aqueous potassium permanganate solutions in which natural gas is absorbed in step (3-a);

(3-b) mercury purification and enrichment;

reducing the mercury absorbed in the step (3-a) to mercury vapor with a stannous chloride solution, and then purifying and enriching the mercury vapor by using an acidic potassium permanganate aqueous solution;

(3-c) detecting the acidic potassium permanganate solutions in which the mercury vapor is enriched in step (3-b) to determine the total mercury content and the composition/content of stable mercury isotopes therein.

12. The method according to claim 11, wherein the step (1-a) comprises heating the crude oil sample to the boiling point of the light hydrocarbon and holding the temperature until the light hydrocarbon volatilizes completely, and then gradually increasing the temperature at an interval of 80 to 120°

C., with each temperature gradient maintained for 20 to 40 minutes until the crude oil sample becomes a solid residue, after that subjecting the solid residue to further cracking by increasing the temperature until the cracking is complete.

13. The method according to claim 11, wherein step (1-a) further comprises sequentially absorbing the gas product released by heating the crude oil sample with a stannous chloride solution and with an acidic potassium permanganate solution, and passing the residual gas product after the absorption into a container containing a silica gel, and the stannous chloride solution in step (1-a) has a concentration of 15 to 25 w/v %.

14. The method according to claim 11, wherein each of the stannous chloride solutions in step (1-b), step (2-b) and step (3-b) independently has a concentration of 15 to 25 w/v %;

wherein each of the acidic aqueous potassium permanganate solutions in step (1-a), step (2-a) and step (3-a) has an acid concentration of 10% and a potassium permanganate concentration of 4%, independently;

each of the acidic aqueous potassium permanganate solutions in step (1-b), step (2-b) and step (3-b) has an acid concentration of 10% and a potassium permanganate concentration of 1%, independently, wherein the acid is sulfuric acid.

15. The method according to claim 11, wherein each of step (1-b), step (2-b) and step (3-b) comprises, independently, pumping a stannous chloride solution into the acidic potassium permanganate solution in which a crude oil is absorbed as collected in step (1-a), the acidic potassium permanganate solution in which a hydrocarbon source rock is absorbed as collected in step (2-a) and the acidic potassium permanganate solution in which a natural gas is absorbed as collected in step (3-a), using nitrogen gas as a carry gas, so as to reduce mercury to mercury vapor, and feeding the mercury vapor into the acidic aqueous potassium permanganate solution with nitrogen gas to purify and enrich the mercury vapor;

wherein the nitrogen gas used as a carry gas in each of step (1-b), step (2-b) and step (3-b) is subjected to mercury trapping treatment respectively, prior to contacting the acidic potassium permanganate solution collected in step (1-a), step (2-a) and step (3-a).

16. The method according to claim 11, wherein each of step (1-c), step (2-d) and step (3-c) comprises detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in each of step (1-b), step (2-b) and step (3-b) with a cold atomic fluorescence mercury detector and a multi-collector inductively coupled plasma mass spectrometer, respectively.

17. The method according to claim 11, wherein step (3-a) further comprises passing the natural gas firstly into the empty impact sampler and then passing the natural gas out from the empty impact sampler into three cascading acidic-potassium-permanganate absorption bottles to perform the three-stage cascading absorption, and passing the residual natural gas after absorption into a silica-gel impact sampler;

wherein step (3-a) further comprises controlling the time for three-stage cascading absorption for natural gas in step (3-a), so that the collected acidic potassium permanganate solution has a mercury content of equal to or greater than 1.0 ng/ml

wherein the natural gas in step (3-a) has a flow rate of 0.5 to 0.7 L/h.

18. The method according to claim 11, wherein step (2-c) comprises dry-pulverizing a hydrocarbon source rock sample and then adding the sample into aqua regia, heating for 2 hours at 95°

C. for digestion, thereafter adding BrCl thereto, continuing to digest at 95°

C. for 30 minutes, then standing for at least 24 hours and adding NH₂OH.HCl thereto to reduce excessive BrCl, left standing and taking a supernatant for detection.

19. The method according to claim 11, further comprising step (4) of:

based on the detection results in step (1-c), step (2-d) and step (3-c), establishing the value range and the critical parameters regarding the mercury isotope ratio in different genetic types of oil-gas, summarizing the mercury information characteristics in mass fractionation and mass-independent fractionation in different genetic types of oil-gas, and establishing an indicator chart for identification, so as to determine the oil-gas source and genesis and guide the exploration deployment.

20. The method according to claim 11, wherein the method performs the detection by using a device comprising:

at least one enrichment-absorption system for mercury in crude oil/hydrocarbon source rock, an enrichment-absorption system for mercury in natural gas and at least one secondary purification-enrichment system for mercury;

the enrichment-absorption system for mercury in crude oil/hydrocarbon source rock comprises three air-absorption bottles, a pyrolysis/cracking system, five impact samplers, and a vacuum pump, which are connected in series by pipe lines;

the enrichment-absorption system for mercury in natural gas comprises five impact samplers connected in series, wherein the first impact sampler is connected to the natural gas outlet from the natural gas well and the last impact sampler is connected to the cumulative gas flow meter;

the secondary purification-enrichment system for mercury comprises a nitrogen-gas cylinder, a collection bottle with potassium permanganate absorption liquid in which mercury isotope is absorbed, and a secondary enrichment-absorption bottle containing an acidic aqueous potassium permanganate solution, which are connected in series by pipe lines, wherein the secondary purification-enrichment system further comprises a stannous-chloride storage bottle, which is connected to a pipe line between the nitrogen-gas cylinder and the collection bottle with potassium-permanganate absorption liquid via a peristaltic pump and through a pipe line.