METHOD FOR QUANTIFICATION OF THE PRODUCTION POTENTIAL OF NATURAL HYDROGEN FROM A ROCK SAMPLE

Description

[0001] The present invention relates to a method and device for continuous analysis of a hydrogen flow generated by chemical interaction between a water-charged carrier gas and a mineral rock sample.

[0002] In general, the invention aims to determine the amount of hydrogen generated by a rock sample during a water reduction reaction at high temperature and in the presence of that sample. The invention also aims to analyze the kinetics of the reduction reaction as a function of temperature and the amount of water.

[0003] Due to the decline in hydrocarbon resources and growing global energy needs, and the search for a less carbon-intensive energy mix, the production and use of hydrogen worldwide have become major issues.

[0004] Besides being a raw material for the chemical industry, particularly for fertilizer production, hydrogen is also a fuel. The low greenhouse gas emissions produced by hydrogen combustion make it a good candidate as an environmentally friendly resource in the context of global warming.

[0005] However, current hydrogen production remains heavily dependent on fossil fuels. Indeed, approximately 60% of the hydrogen produced comes from the high-temperature steam reforming of methane (or natural gas), itself most often generated using fossil fuels. Around 20% comes from coal gasification, and the remainder from liquid hydrocarbons. Less than 5% is produced by electrolysis, a process that is very energy-intensive, while this energy is most often generated by hydrocarbon or coal-fired power plants.

[0006] The main challenge posed by hydrogen as a clean energy source, or raw material, is its production. Therefore, the exploration of natural hydrogen sources becomes crucial. Although still in the prospective stage, understanding natural hydrogen generation systems should allow us to harness this natural hydrogen in the future without resorting to fossil fuels. It is in this context that the invention provides solutions for simulating, in the laboratory, the natural conditions of hydrogen production in geological formations.

[0007] The applications targeted by the invention are primarily in the field of exploring natural hydrogen sources worldwide. More specifically, the invention is mainly (but not exclusively) concerned with a particular method of generating hydrogen from mineral rocks. This method of generation results from the interaction between water, which is abundant in all deep geological environments, and the iron minerals present in certain types of rocks. This generation occurs naturally in various specific geological environments, such as mid-ocean ridges, obduction zones, subduction zones, and certain Archean and Neoproterozoic cratons. These environments are subjected to high temperatures ranging from 100°C to 400°C (and sometimes higher), thus favoring a redox reaction.

[0008] Several chemical reactions allow for the natural generation of hydrogen. The best known is the serpentinization reaction, which characterizes the hydration of olivine into serpentine. This reaction generates hydrogen as a byproduct. More precisely, water causes the oxidation of iron contained in fayalite (the iron-rich end-member of olivine, representing approximately 10% of olivine) according to the following reaction: 2H₂O + 3Fe₂SiO₄ = 2Fe₃O₄ + 3SiO₂ + 2H₂ (g)

[0009] A similar reaction capable of producing hydrogen also occurs during the hydration of orthopyroxene. In cratons, iron-rich rocks, particularly banded iron formations (BIFs), oxidize, with the iron changing from ferrous (Fe²⁺) to ferric (Fe³⁺). This same reaction can occur in the presence of amphiboles, found in granites, which are also iron-rich. US 2016039669A1 discloses such a hydrogen production process.

[0010] Just as in the early days of oil exploration, the first signs of hydrogen generation underground were found on the surface. Indeed, some places in the world are known for their natural hydrogen emissions, such as the Yanartas fires in Turkey, which have been burning for over 2,500 years. Other hydrogen emissions have also been detected on the surface, associated with a unique geomorphology of circular depressions measuring from a few meters to several kilometers, known as "fairy rings," and characterized by distinct vegetation.

[0011] Furthermore, an onshore natural hydrogen deposit was discovered by chance and has been under development in Mali by the company Petroma (now Hydroma) since 2010. This shallow well supplies a turbine that generates electricity for a village of 1,500 inhabitants. Since then, numerous exploration permits have been requested worldwide, including in the United States, France, and Australia.

[0012] On the offshore side, certain geological environments have been identified as capable of generating natural hydrogen. This is the case for all mid-ocean ridges, but also for the Mariana Trench, in which several serpentinized mud volcanoes produce a gas mixing hydrogen and methane.

[0013] In this context, the invention consists of a method and a device capable of rapidly and automatically analyzing rock samples in the laboratory to determine the amount of hydrogen generated during a water reduction reaction in the presence of that sample. The invention thus makes it possible to deduce the residual potential for natural hydrogen production from the rocks from which the sample originates.

[0014] This goal is achieved according to a first aspect of the invention by means of an automatic method for quantifying the dihydrogen generated by a sample of mineral source rock containing a ferrous metallic compound, characterized in that a water reduction reaction is carried out in the presence of said sample and water vapor from 300°C up to a temperature of about 1200°C and the quantity of said dihydrogen generated by said sample during this reaction is determined in order to qualify said source rock as a potential source of natural hydrogen.

[0015] One of the parameters sought by the process according to the invention is the temperature (TmH2) corresponding to the generation of a maximum quantity of hydrogen and allowing the determination of the generation kinetics of said hydrogen.

[0016] Another parameter sought by the process of the invention is the molar yield (η n H2) and / or the mass yield (η m H2) of the water reduction reaction characterized by the ratio between the molar quantity of hydrogen produced (nH2) and the molar quantity of the rock sample containing iron (n reactant) or its mass in the case of mass yield, and which is defined according to the following formulas: η n H 2 = nH 2 prod n r é actif × 100 et η m H 2 = mH 2 prod m r é actif × 100

[0017] The process of the invention thus uses the quantity of hydrogen generated relative to the mass of sample used during the analysis to calculate the useful molar and mass yields (N n H2 and N m H2) and to determine the hydrogen potential as well as the maturity of the source rock.

[0018] According to an advantageous implementation feature of this process, water is brought into contact with the rock sample by means of an inert carrier gas transporting water vapor.

[0019] The initial temperature of the reactor is between 200°C and 400°C and the final temperature of the reduction reaction is between 600°C and 1200°C.

[0020] Preferably, the temperature rise gradient is between 0.1 and 50°C / min.

[0021] The carrier gas flow rate is between 0 and 500mL / min and its water content is controlled via the temperature rise of a liquid water reservoir or by vaporizing liquid water in a hot gas stream.

[0022] At the reactor outlet, the gaseous effluents from the water reduction reaction are separated to ensure the condensation of the water and the drying of the gaseous fraction of the effluents.

[0023] Next, this gaseous fraction is analyzed to determine the amount of hydrogen produced by the sample.

[0024] Another object of the invention is a device for implementing the process described above for the continuous quantification of hydrogen emitted by a sample of mineral or sedimentary source rock, characterized in that it comprises a reactor intended to receive said sample, said reactor being provided with a carrier gas injection tube supplied by a balloon containing water heated between 0 and 100°C and provided with a temperature maintenance line, heating means ensuring temperature rises from 0 to 1200°C inside the reactor, a separator collecting the gaseous effluents from the reactor and ensuring the condensation of the water and the exhaust of the gaseous fraction of the effluents to a drying means and a hydrogen detector analyzing the dried gaseous fraction.

[0025] According to an advantageous feature of the invention, the device includes a piston ensuring the introduction of the sample into the reactor.

[0026] In addition, the device includes thermocouples for controlling the temperatures of the tank and the line for maintaining the temperature of the injected carrier gas, as well as a flow meter ensuring control of the flow of the injected carrier gas.

[0027] Preferably, the device of the invention includes an injection nozzle controlling the quantity of water injected into the reactor and a hygrometer or dew point detector for controlling the water content of the injected carrier gas.

[0028] The invention makes it possible to provide precise and reliable information to companies exploring for naturally occurring hydrogen from simple samples of source rock taken from the subsoil. In particular, this information ensures good visibility regarding the potential of a geological area for hydrogen production.

[0029] The implementation of the quantification process can be carried out in the laboratory using a simple and easy-to-implement device, including in a mobile and / or remote manner.

[0030] The invention thus allows the analysis of the hydrogen generation potential of a rock sample in less than an hour, whereas similar analyses in autoclaves, for example, can take weeks.

[0031] Other features and advantages of the invention will become apparent from the description that follows, with reference to the attached figures which are detailed below.

[0032] [ Fig. 1 ] represents an embodiment of the device of the invention with the path of the carrier gas during the implementation of the process.

[0033] [ Fig. 2 ] is a graph representing hydrogen generation as a function of temperature from a siderite sample.

[0034] [ Fig. 3 ] is a graph representing hydrogen generation as a function of temperature from an olivine sample.

[0035] For clarity, identical or similar elements are identified by identical reference symbols in the description and on the figures.

[0036] Naturally, the methods of implementing the invention and of constructing the associated device, schematically illustrated in the figures above and described below, are given only as non-limiting examples. It is explicitly provided for in the scope of the invention that different methods can be proposed and combined to create others.

[0037] In general, the invention relates to the field of prospecting for natural hydrogen sources through the laboratory analysis of hydrogen-bearing source rocks. More specifically, the method of the invention consists of automatically quantifying the dihydrogen generated by a sample of mineral or sedimentary rock containing a ferrous metallic compound during a water reduction reaction up to a temperature of 1200°C. Determining the quantity of dihydrogen generated by this sample thus allows the source rock to be classified as a potential source of natural hydrogen using the parameters ηH2 and TmH2.

[0038] To this end, water in vapor form is introduced into the rock sample in a reactor 1 by means of an inert carrier gas (for example nitrogen N2), as illustrated by the figure 1 The gaseous effluents from the high-temperature water reduction reaction are conveyed and separated to allow for water condensation and drying of the gaseous fraction. This dried gaseous fraction is then analyzed at the end of the process to determine the amount of hydrogen initially present in the sample.

[0039] The initial temperature of the water in vapor form injected into reactor 1 is between 200°C and 400°C and the final temperature of the reduction reaction is between 600°C and 1200°C.

[0040] Preferably, the temperature rise gradient in reactor 1 is between 0.1 and 50°C / min to allow for the study of hydrogen generation kinetics. The flow rate of the carrier gas injected into the reactor is between 0 and 500 mL / min, and the water content of the carrier gas is controlled by heating a liquid water reservoir.

[0041] Preferably, the temperature cycle integrated into the process starts at 300°C and has a 3-minute plateau. Then, a temperature increase is carried out at a rate of 25°C / min up to a final temperature of 1200°C.

[0042] One embodiment of the device for implementing this process is shown on the figure 1 This device comprises a ceramic reactor 1 fed by a tube 21 that continuously injects an inert carrier gas. This reactor is designed to withstand temperatures up to 1200°C, achieved through a heating wire winding with carefully distributed turns to obtain a homogeneous and precise temperature at the sample level. The rock sample(s) are introduced into reactor 1 via an automatic sampler system that deposits the samples onto a piston 11, ensuring their translational movement within reactor 1 and its sealing once closed.

[0043] The carrier gas is pre-charged with water using a hydration / humidification system. For this purpose, the carrier gas injection tube 21 is connected to a flask 2 containing water heated to between 0 and 100°C. Thus, according to the implementation method of the process and using the device illustrated by the figure 1 The carrier gas injected into reactor 1 allows a quantity of water to be carried along which is intended to react in reactor 1 with the mineral phase of the rock sample.

[0044] The carrier gas hydration system includes a flask 2 containing distilled water, positioned upstream of the pyrolysis reactor 1, in which the carrier gas bubbles. A gas humidity control device can also be optionally added to test different humidification levels. This flask 2 is equipped with heating elements 20 (such as Joule heating elements) to heat the water from 0 to 100°C, thus ensuring its transition from the liquid to the vapor phase.

[0045] The gas line 21, running from the flask 2 to the inlet of the reactor 1, is itself maintained at a suitable temperature by means of a line 22 that ensures temperature maintenance and thus prevents any condensation before chemical interaction with the rock sample. The device of the invention further includes a system of solenoid valves (not shown) whose automatic activation allows selection of the humidification mode bypass.

[0046] The flow rate of the carrier gas can be controlled using mass flow meters (not shown) capable of performing flow rate variations from 0 to 500 mL / min.

[0047] In addition, the device includes thermocouples 23 for controlling the temperatures of the balloon 2, the tubing 21 of the injected carrier gas and the reactor 1 (located below the sample and on the wall of said reactor) as well as a flow meter (not shown) ensuring control of the flow of the injected carrier gas.

[0048] Preferably, the device of the invention includes an injection nozzle (not shown) controlling the parameters of the carrier gas and a hygrometer and / or a dew point detector (not shown) intended to control the water content of the injected carrier gas.

[0049] At the outlet of reactor 1, the device includes a system 3 ensuring the separation between the gaseous effluents from the pyrolyzed sample and the liquid fraction. These effluents then pass through a drying means such as a desiccant 4 in order to eliminate any residual water.

[0050] A hydrogen detector 6 performs the final analysis of the dried gaseous fraction and determines the initial amount of hydrogen present in the sample. Depending on the type of hydrogen detector 6 used at the end of the line, a series of traps 5 can be added to remove elements that could interfere with the measurement.

[0051] Examples of implementation of the process of the invention will now be described in detail below, being applied to two different rock samples but under identical experimental conditions.

[0052] In these examples, the temperature of the balloon 2 is maintained at 90°C, as is that of the injection tube 21. The carrier gas circulating in the water balloon has a flow rate of 100 mL / min. The temperature cycle used starts at 300°C with a temperature plateau of 3 minutes and ends at 1000°C. The temperature gradient used is 20°C / min.

[0053] The two samples analyzed are, respectively, siderite (iron carbonate - figure 2 ) and olivine (the main mineral constituent of the Earth's mantle - figure 3 Siderite, with the formula FeCO3, is synthetic and 100% pure, with an iron content of approximately 48%. Olivine is a natural forsterite with an iron content of approximately 3.8%.

[0054] When analyzing 120 mg of siderite, a significant hydrogen peak is generated between 350°C and 500°C, corresponding to the decarbonation range of this mineral ( figure 2 Integrating this curve allows us to estimate the production at approximately 0.16 mg, or 0.08 moles of hydrogen per 1 mole of siderite analyzed, representing a yield of 8%. Hydrogen production then drops to zero. In this example, the temperature (TmH2) is 452°C.

[0055] Analysis of 120 mg of forsterite produces less hydrogen, which is expected since this rock contains twelve times less iron than siderite. The molar yield is 0.6% this time. Hydrogen production begins at 600°C, but the peak production is observed between 800°C and 1000°C. figure 3 ). In this example, the temperature (TmH2) is equal to 890°C.

Claims

1. Method for automatically quantifying the dihydrogen generated by a sample of mineral or sedimentary parent rock containing an iron-containing metal compound, wherein a water reduction reaction is carried out in the presence of said sample and water vapor, the temperature of which is rised to approximately 1200 °C, and the amount of said dihydrogen generated by said sample during this reaction is determined in order to qualify said parent rock as a potential source of natural hydrogen.

2. Method according to claim 1, characterized in that the water is brought into contact with the rock sample by means of an inert carrier gas carrying water vapor.

3. Method according to either of the preceding claims, characterized in that the gaseous effluents from the water reduction reaction are separated to ensure condensation of the water and drying of the gaseous fraction of said effluents.

4. Method according to the preceding claim, characterized in that the dried gaseous fraction is analyzed in order to determine the amount of hydrogen initially present in the sample.

5. Method according to any one of the preceding claims, characterized in that the initial temperature of the water vapor prior to the temperature rise is between 200 °C and 400 °C.

6. Method according to any one of the preceding claims, characterized in that the final temperature of the water vapor at the end of the temperature rise during the reduction reaction is between 600 °C and 1200 °C.

7. Method according to any one of the preceding claims, characterized in that the gradient of the temperature increase is between 0.1 and 50 °C / min.

8. Method according to any one of the preceding claims, characterized in that the carrier gas flow rate is between 0 and 500 mL / min.

9. Method according to any one of the preceding claims, characterized in that the water content of the carrier gas is monitored by increasing the temperature of a water reserve or by vaporizing liquid water in a hot gas flow.

10. Method according to any one of the preceding claims, characterized in that the temperature (TmH2) corresponding to the generation of a maximum amount of hydrogen is determined, and the kinetics of the generation of said hydrogen is deduced therefrom.

11. Method according to any one of the preceding claims, characterized in that the quantity of hydrogen generated by the sample is used to calculate the useful molar and mass yields (ηnH2 and ηmH2) and to determine the potential amount of hydrogen in the parent rock, as well as the maturity of the parent rock from which said sample was taken.

12. Device for continuously quantifying the hydrogen emitted by a sample of mineral or sedimentary parent rock, characterized in that it comprises a reactor (1) intended to receive said sample, said reactor being provided with a carrier gas injection tube (21) fed by a tank (2) containing water heated to between 0 and 100 °C and provided with a line (22) for maintaining the temperature, a reactor with a winding of heating wires ensuring temperature rises from 0 to 1200 °C inside said reactor, a separator (3) collecting the gaseous effluents from the reactor and ensuring the condensation of the water and exhaust of the gaseous fraction of the effluents to a drying means (4) and a hydrogen detector (6) analyzing the dried gaseous fraction.

13. Device according to claim 12, characterized in that it comprises a piston (11) ensuring the introduction of the sample into the reactor (1).

14. Device according to any one of claims 12 or 13, characterized in that it comprises thermocouples (23) intended for monitoring the temperatures of the tank (2) and the line (22) for maintaining the temperature of the injected carrier gas.

15. Device according to any one of claims 12 to 14, characterized in that it comprises a flowmeter for monitoring the flow rate of the injected carrier gas.

16. Device according to any one of claims 12 to 15, characterized in that it comprises an injection nozzle controlling the amount of water injected into the reactor (1).

17. Device according to any one of claims 12 to 16, characterized in that it comprises a hygrometer or dew point detector intended for monitoring the water content of the injected carrier gas.