REAL SUBSOIL

BACKGROUND OF THE INVENTION

The present invention relates to determination of native di-hydrogen gas sources location or less specifically, of an exploration or exploitation scheme for a real subsoil.

The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. Furthermore, all embodiments are not necessarily intended to solve all or even any of the problems brought forward in this section.

Hydrogen is the lightest element on the periodic table. In the form of a gas, the di hydrogen (or simply hydrogen gas) is a zero-emission fuel when burned with oxygen. It can be used in electrochemical cells or internal combustion engines to power vehicles or electric devices.

Hydrogen may be used in various fields such as fuel for cars, propulsion of spacecraft, production of ammonia, coolant, semiconductor industries, etc.

Therefore, there is a need for generating/collecting hydrogen at an industrial scale. In the past, the generation of hydrogen has been preferred as no natural hydrogen deposit is known. The main reason is that no mineralogical material/rock is able to retain di-hydrogen: due to the size of the molecules of di-hydrogen, this gas is able to pass through any material/rock in the subsoil (within few dozens of years). Therefore, we suppose that no large natural hydrogen reservoir (versus petroleum reservoir) may exist on earth.

Today, the generation of hydrogen may be steam-reforming, partial oxidation, plasma reforming, electrolysis, photo biological water splitting, fermentative hydrogen production, etc. Nevertheless, native hydrogen sources (that continuously generates di-hydrogen) may exist and can be exploited at an industrial scale.

Therefore, there is a need to have a method to determine their locations according to accurate criteria.

If native hydrogen sources does not exist and cannot be exploited at an industrial scale, it is still possible to use the previous determination for determining if the subsoil is adapted to abiotic methane production or to trap carbon dioxide.

SUMMARY OF THE INVENTION

The invention relates to a method for determining of an exploration or exploitation scheme for a real subsoil, this method comprising:

- determining a first scoring value based on a determined geometry of the subsoil, said first scoring value represents the ability of the subsoil to guide native H2 to a ground location;

- determining a second scoring value based on a determined volume of serpentine in the subsoil, said determined volume of serpentine in the subsoil may be oxidized;

- determining a third scoring value based on a porosity value or a permeability value of rock in the subsoil,

- determining a fourth scoring value based on presence of ultrabasic rock in the subsoil or presence of plate margin or plate boundary ;

- determining an exploration or exploitation scheme based on the first scoring value, the second scoring value, the third scoring value and fourth scoring value.

The determining of an exploration or exploitation scheme for a real subsoil may be a determining of native di-hydrogen gas sources location for industrial exploitation as said ground source. The determining of an exploration or exploitation scheme for a real subsoil may be a determining of the ability of the subsoil to trap carbon dioxide gas.

The determining of an exploration or exploitation scheme for a real subsoil may be a determining of abiotic methane gas sources location for industrial exploitation as said ground source.

For instance, determining native di-hydrogen gas sources location for industrial exploitation as said ground source may be further based on a fifth scoring value based on presence of catalyzer of serpentinization in the subsoil.

In addition, determining of an exploration or exploitation scheme may be further based on a sixth scoring value based on present uplift of the subsoil.

In a possible embodiment, determining of an exploration or exploitation scheme is further based on a seventh scoring value based on presence of gravity anomalies or magnetic anomalies in the subsoil.

Furthermore, determining of an exploration or exploitation scheme may be further based on an eighth scoring value based on electric resistivity variation in the subsoil.

Determining of an exploration or exploitation scheme may be further based on a ninth scoring value based on seismic activity of the subsoil.

Also, determining of an exploration or exploitation scheme may be further based on a tenth scoring value based on presence of abiotic methane in the subsoil.

Other features and advantages of the method and apparatus disclosed herein will become apparent from the following description of non-limiting embodiments, with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitations, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which:

- Figure 1 a is a schematic diagram to illustrate the scale of investigation in order to determine the native di-hydrogen gas sources locations.

- Figure 1 b is a diagram to illustrate the various determinations that could be useful for the native di-hydrogen gas sources location determination.

- Figures 2a, 2b, 2c are side views of geological formation adapted to guide hydrogen gas to collecting facilities (industrial plants), including faults if applicable;

- Figure 2d is a side view of geological formation which is not adapted to guide hydrogen gas to collecting facilities (industrial plants).

DESCRIPTION OF PREFERRED EMBODIMENTS

Serpentinization is a process whereby rock (usually ultramafic) is changed, with the addition of water into the crystal structure of the minerals found within the rock. A common example is the serpentinization of peridotite (or dunite) into serpentinite (the metamorphic equivalent).

2FeO +H20 Fe203 + H2

Serpentinization leads to the formation of di-hydrogen (H2) due to the oxidation of Iron.

Serpentinization may occur in various situations: mid-ocean ridges, fore-arc systems, terrestrial ophiolites, subduction or obduction zones, piedmont of mountain chains, etc. Figure 1 a is a schematic diagram to illustrate the scale of investigation in order to determine the native di-hydrogen gas sources locations.

At first (element 101 ), the analysis / determination is quite coarse (approx. 1000 km in radius).

In this step, it is determined (step 1 10 of figure 1 b) if subsoil of a coarse region has ultrabasic rocks (UBR). This determination may be performed thanks to drilling of wells or by the mapping of outcrops. This determination may be performed specifically to determine the native di-hydrogen gas sources locations but it can be done thanks to bibliographic synthetic report (i.e. based on previous subsoil analysis). This determination could be done onshore using geological maps. If no ultra-basic rock is present in the subsoil, the probability (or any scoring value) P1 that H2 sources are present (adequate for industrial purpose) are quite low.

This criterion may be replaced by the determination that this coarse region comprises plate margins or plate boundary.

Then, if the probability (or any scoring value) P1 is higher than a predetermined threshold T1 , a finer analysis (element 102) may be performed (e.g. approx. 100 km in radius).

The following determinations may be performed at this latter scale.

For instance, it is possible to determine (step 1 1 1 of figure 1 b) gravity or magnetic anomalies. A gravity anomaly (Bouguer Anomaly) is the difference between the observed acceleration of free fall, or gravity, on a planet's surface, and the corresponding value predicted from a model of the planet's gravity field.

A magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks.

These anomalies are of interest as serpentinization is often linked with low density rocks and ferromagnetic rocks (the more serpentinized, the less dense, and the more magnetic). Thanks to the determination of these anomalies, a probability (or any scoring value) P2 of presence of serpentinization (presence of H2 sources) is determined. If no anomaly is detected, P2 is determined as low.

The determination of these anomalies may be replaced or combined with geological studies to determine (step 1 12 of figure 1 b) the composition of the subsoil (e.g. presence of serpentine).

Thanks to the determination of the composition of the subsoil, a probability (or any scoring value) P3 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no serpentine is detected P3 is determined as low.

In addition, the analysis (step 1 13 of figure 1 b) of the actual vertical movement (uplift) may be particularly accurate as the creation of serpentine is often linked to a subduction zone. Therefore, if the actual vertical movement is important, serpentinization may be in progress in said subsoil (renewing mineral reactions).

Thanks to the determination of the actual vertical movement, a probability (or any scoring value) P4 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no actual vertical movement is detected P4 is determined as low.

It is noted that, mineralogy analysis and hydrothermal source composition chemical and geochemical analysis (chemical composition, isotopic analysis...) may determine (or has determined) (step 114 of figure 1 b) that the subsoil contains serpentinization catalyzer (e.g. Aluminum, Boron, Bromine, Iron, Nickel, etc.) if serpentinization process may be accelerated.

Thanks to the determination of the serpentinization catalyzer, a probability (or any scoring value) P5 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no serpentinization catalyzer is detected P5 is determined as low.

It may also be useful to analyze (step 1 15 of figure 1 b) the methane gas (CH4) that is collected from the subsoil. If the methane has an abiotic origin, serpentinization may be in progress in the subsoil.

Thanks to the determination of the abiotic origin of the methane gas, a probability (or any scoring value) P6 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no CH4 has an abiotic origin P6 is determined as low.

It is noted that if abiotic gas is collected from the subsoil, if said collection is adapted for industrial purpose but if the H2 production is not adapted for industrial purpose (this exclusion is optional), one may decide that an abiotic methane production is adapted for industrial exploitation. Then, if P2.P3.P4.P5.P6 is higher than a predetermined threshold T2, a finer analysis (element 103) may be performed (e.g. approx. 50 km in radius). It is noted that the product P2.P3.P4.P5.P6 may be replaced by any weighted product or any function of P2, P3, P4, P5 and/or P6 that is an increasing function with said parameters. Otherwise, the process may be ended.

The following determinations may be performed at this latter scale.

For instance, the analysis (step 1 16 of figure 1 b) of the seismic activity (e.g. in gravity/magnetic anomaly zones) may be particularly accurate as the creation of serpentine induces an increase of the volume of the rock and then the increase of the stress / shear in the subsoil. Therefore, if the seismic activity is important or more frequent than expected, serpentinization may be in progress in said subsoil (for buried confined serpentinization processes)

Thanks to the determination of the seismic activity, a probability (or any scoring value) P7 of presence of serpentinization (presence of H2 sources) is determined. For instance, except for outcropping serpentinization, if no seismic activity is detected P7 is determined as low... In the case of outcropping serpentinization, no related seismic activity is expected.

It may also be useful to determine (step 1 17 of figure 1 b) electric resistivity variation (Magnetotelluric or electric acquisition) as serpentinization induces changes in subsoil resistivity. Therefore, if the electric resistivity variation is important, serpentinization may be in progress in said subsoil.

Thanks to the determination of the electric resistivity variation, a probability (or any scoring value) P8 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no variation is detected P8 is determined as low. Then, if the product P7.P8 is higher than a predetermined threshold T3, a finer analysis (element 104) may be performed (e.g. approx. 10 km in radius). It is noted that the product P7.P8 may be replaced by any weighted product or any function of P7 and/or P8 that is an increasing function with said parameters. Otherwise, the process may be ended. The following determinations may be performed at this latter scale.

It is useful to determine (step 1 18 of figure 1 b) at the ground level, in said area, the H2 seepage. This can be done thanks to predetermined H2 concentration map or thanks to local measurements.

Thanks to the determination of H2 concentration at the ground level, a probability (or any scoring value) P9 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no H2 concentration at the ground level is detected P9 is determined as low.

It is also useful to determine (step 1 17 of figure 1 b) at the ground level, in said area, the H2 flux from the subsoil. Thanks to the determination of H2 flux, a probability (or any scoring value) P10 of presence of serpentinization (presence of H2 sources) is determined. For instance, if no flux is detected P10 is determined as low.

Then, if the product P9.P10 is higher than a predetermined threshold T4, a finer analysis (element 105) may be performed (e.g. approx. 1 km in radius). It is noted that the product P9.P10 may be replaced by any weighted product or any function of P9 and/or P10 that is an increasing function with said parameters. Otherwise, the process may be ended.

The following determinations may be performed at this latter scale. It may be useful to determine to ability of the subsoil to meet the industrial requirements for exploitation of H2 sources.

For instance, said ability to meet the industrial requirements may be an estimation of the subsoil volume that can still be subject to serpentinization (i.e. related to the expected volume of H2 to be produced) or the geometry of the subsoil.

For instance, in reference of Figures 2a, 2b and 2c, the geometry of the subsoil may be favorable: an industrial plant 205 installed on the ground 251 may adequately collect hydrogen produced by serpentinization in zone 203 (or along the fault 213) if geobodies 201 , 204 and 202 are able to guide (fetch area) the hydrogen towards the plant 205 (e.g. clay).

In reference of Figure 2d, the geometry of the subsoil may be non-favorable: geobodies 21 1 , 213 and 212 does not form a funnel to guide the hydrogen towards the plant 205.

In addition, or in alternative, it is possible to determine permeability and/or porosity of the subsoil (in particular in zone 203). High permeability and/or porosity may lead to proper drainage of H2. In particular if the ratio porosity over permeability is low, a proper drainage of H2 is possible

If it is determined that it is possible to meet the industrial requirements, an industrial plant may be installed in order to collect the hydrogen produced by serpentinization.

Otherwise, the process may be ended.

All the above-mentioned determinations (which lead to probability (or any scoring value) Px assessment with x any integer greater than or equal to 1 and lower than or equal to 10) is optional and may be used in combination or alternatively. If a determination is not performed, the associated probability (or any scoring value) is set to a predetermined value (e.g. Px=1 or Px=0.8 with x any integer greater than or equal to 1 and lower than or equal to 10) or simply ignored in the calculation.

It is noted that if the previous process is ended, and if the subsoil contains an important volume of serpentine, it is possible to determine that said volume may be adapted to store/trap C02 by carbonation.

Expressions such as "comprise", "include", "incorporate", "contain", "is" and "have" are to be construed in a non-exclusive manner when interpreting the description and its associated claims, namely construed to allow for other items or components which are not explicitly defined also to be present. Reference to the singular is also to be construed as to be a reference to the plural and vice versa.

A person skilled in the art will readily appreciate that various parameters disclosed in the description may be modified and that various embodiments disclosed may be combined without departing from the scope of the invention.

For instance, when the above application relates to probability, one may understand that any scoring value may also be used (e.g. integer, letters, scale, etc.). In addition, the probabilities (or the scoring values) determined for assessing the native di-hydrogen gas sources location may be any set or subset of probabilities mentioned above.