EP3298100A1

EP3298100A1 - Method for exploitation of a subterranean formation by injection of a fluid comprising an additive tagged by a luminescent semiconductor nanocrystal

Info

Publication number: EP3298100A1
Application number: EP16717662.7A
Authority: EP
Inventors: Eric Lecolier; Patrick Gateau
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2015-05-21
Filing date: 2016-04-22
Publication date: 2018-03-28
Also published as: FR3036403B1; US20180283173A1; FR3036403A1; US10738601B2; WO2016184640A1

Abstract

The present invention relates to a method for exploitation of a subterranean formation, into which at least one fluid is injected. According to the invention, the fluid comprises at least one additive, the additive being tagged by at least one luminescent (fluorescent or phosphorescent) semiconductor nanocrystal. In this way, and by optical analysis of the presence of luminescent semiconductor nanocrystal in a fluid recovered from the subterranean formation, it is possible to determine the presence and/or the amount of additive in the fluid recovered. Given that the semiconductor nanocrystal is either phosphorescent or fluorescent, the additive is rendered easily detectable and quantitatively assayable in the fluids recovered from the subterranean formation.

Description

The present invention relates to the field of exploration and the exploitation of a subterranean formation. The invention relates more particularly to the determination of properties of a subterranean formation and the detection and analysis of the composition of a fluid recovered from the subterranean formation.

The invention relates in particular to the field of enhanced oil recovery (EOR), the field of production water treatment, the field of oil drilling, the field of oil production and / or of source rock gas, the field of treatment of underground formations, ...

Methods have been developed to determine the properties of an underground formation, such as the petrophysical properties (permeability, porosity), the identification of preferential paths, or of preferential connections ... The knowledge of these properties makes it possible in particular to adapt methods of operating the underground formation such as enhanced recovery processes, and oil and / or parent-rock gas production processes. These methods are essentially based on the injection of elements, for example radioactive elements, into the underground formation and observation of their behavior (adsorption, paths traveled, travel time, ...). However, these methods do not give the information sought reliably, because the elements introduced do not have the same behavior as the fluid with additive which is subsequently injected into the subterranean formation. In particular, by their distinct chemical form, their adsorption and their speed differ. In addition, the use of radioactive elements entails important constraints for these methods.

For the exploration and exploitation of an underground formation, it is common to inject a fluid into the underground formation in order to increase the efficiency of the processes. To optimize these processes, it is customary to include at least one additive in the injected fluid. This additive can take the form of organic molecules, such as polymers, copolymers and / or surfactants ... It can also take the form of inorganic molecules such as minerals (clays, barite, etc.). oxides (titanium oxides, iron oxides, ...) ... Although the method is improved, the addition of additive (s) poses certain problems related in particular to the pollution by the additive of the underground formation, to the pollution by the additive of the water contained in the underground formation, to the pollution of the water

FIRE I LLE OF REM PLACEM ENT (RULE 26) and / or hydrocarbons produced by the additive ... It is therefore necessary to monitor the behavior of the additive in the subterranean formation.

For the enhanced recovery of hydrocarbons, it is interesting to know if the additive used, in general polymers, copolymers and surfactants, is found in the water produced, and if so, to know its concentration, in order to perform a proper water treatment.

For the drilling of a well, a fluid is injected which fulfills four functions which are: the raising of the rock cuttings, the maintenance in suspension of the cuttings during stops of circulation, the maintenance of the pore pressure at the right of the training as well as the cooling and lubrication of the drill tool. The drilling fluid contains several additives to fulfill these four functions such as viscosifiers, lubricants, defoamers, filtrate reducers, and the like. The dosage of each of the additives of the formulation of the drilling fluid is optimized so that this formulation has the desired properties. The additives can be either organic molecules, such as polymers, copolymers, associative polymers, surfactants, or inorganic particles (clays, barite, etc.). However, a variation in the concentration of additive (s) results in the drilling fluid no longer fulfilling the functions mentioned above. On the drilling platform, a person is responsible for constantly checking that the properties of the drilling fluid are in accordance with the initial specifications. For this purpose, it may be advantageous to have a method for dosing instantly or online concentration of certain additives contained in the drilling fluid once raised to the surface. The knowledge of this information then makes it possible to adjust in real time the concentration of the additives in the formulation of the drilling fluid: it is then of constant composition and therefore has permanently the desired properties for drilling in progress. This practice can help to ensure safety during drilling, and make it more economical (always being in the best drilling conditions).

In addition, for the production of oil and / or source rock gas, it may be of particular interest to verify that the additives (for example polymers) of the fracturing fluid are not found in one or more aquifers (s). ), groundwater above the exploited subterranean formation. In order to control and monitor fracturing operations, it may be interesting to determine the amount of certain additives used in fracturing fluids left in fractures generated in bedrock: for this, it may be useful to measure the concentration of additives of the fracturing fluids before fracturing and their concentration after fracturing (once they are reproduced).

Another desirable application is the monitoring of the injection of anti-hydrate additives, or anti-deposits, or anticorrosion. No current method allows effective monitoring, simple to implement, the injection of additive (s) into the underground formation. In fact, the additives used are not easily and rapidly detectable in the fluids recovered from the underground formation. Also, it is not possible to use the additive or additives present in the fluids as tracers and thus allow monitoring and monitoring of the injection of fluids into the underground formation. Similarly, the detection and the determination of additive (s) in fluids produced on the surface (production water, hydrocarbons, drilling fluids, fracturing fluids, EOR fluids, ...) is long and complex because of the multiple interference due to the presence of numerous compounds present in the fluids recovered at the surface. To arrive at measuring the concentration of additive (s) in the fluids produced on the surface, it is necessary to use several steps to separate, extract the desired additive (s); however this process is very long and does not achieve the desired result.

To solve these problems, the present invention relates to a method of operating a subterranean formation, in which at least one fluid is injected. According to the invention, the fluid comprises at least one additive, the additive being marked by at least one nano-semiconductor crystal luminescent (fluorescent or phosphorescent). In this way, and by optical analysis of the presence of luminescent nano-crystalline semiconductor in a fluid recovered from the subterranean formation, it is possible to determine the presence and / or the amount of additive in the recovered fluid. Since the nano-crystal semiconductor is either phosphorescent or fluorescent, the additive is made easily detectable and quantitatively measurable (especially when the additive is labeled with at least one nano-crystal semiconductor fluorescent) in the recovered fluids underground formation.

The process according to the invention

The invention relates to a method of operating a subterranean formation, in which at least one fluid is injected into said subterranean formation, said injected fluid comprising at least one additive. For the process, the following steps are carried out:

a) at least one additive is marked with a nano-crystalline semiconductor light-emitting device; b) injecting said fluid comprising said labeled additive into said subterranean formation;

c) recovering at least one fluid from said subterranean formation; and

d) optically analyzing the presence and / or amount of said additive labeled by said nano-crystalline semiconductor luminescent in said recovered fluid. According to the invention, said additive is marked by said nano-crystalline semiconductor light by grafting said luminescent nanoconductor crystal on said additive, or by incorporating said nano-crystalline semiconductor luminescent into the structure of said additive, or coating said additive with said luminescent nanoconductor crystal in a coating layer.

According to one embodiment of the invention, said luminescent nano-crystalline semiconductor comprises a material chosen from zinc sulphide (ZnS), zinc oxide (ZnO), cadmium sulphide (CdS), selenide zinc (ZnSe), cadmium sulphide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), lead sulphide (PbS), lead telluride (PbTe), lead selenide (PbSe), CulnSe ₂ , CulnS ₂ , CdSeTe, CdHgTe, and ZnS / Zn ^ Cd _x S _, zinc sulfide with manganese (ZnS: Mn), zinc sulfide doped with europium (ZnS: Eu), calcium sulphide doped with europium (CaS: Eu), strontium sulphide doped with europium (SrS: Eu), strontium sulphide doped with europium and dysprosium (SrS: Eu, Dy), strontium sulfide doped with europium and copper (SrS: Eu, Cu)

According to an alternative embodiment, said nano-crystalline semiconductor light is in the form of a semiconductor core embedded in at least one semiconductor shell.

Advantageously, said nano-semiconductor crystal luminescent is in the form of a nano-crystal multihull whose composition is selected from CdSe / CdS / ZnS, CdSe / ZnSe / ZnS and InP / ZnS.

According to one characteristic of the invention, said luminescent semiconductor nanocrystal is composed of three atomic elements belonging to columns I, III, and VI of the periodic table.

Preferably, said luminescent semiconductor nanocrystal whose composition is chosen from zinc sulfide doped with manganese (ZnS: Mn), zinc sulphide doped with europium (ZnS: Eu)

Advantageously, said luminescent semiconductor nanocrystal has substantially a spherical, nano-cylinder, or nano-wafer shape.

According to an alternative embodiment, said additive is an organic compound such as a polymer, a copolymer, or a surfactant.

Alternatively, said additive is an inorganic compound such as a clay mineral, barite, or a metal oxide.

According to an alternative, said additive is an anti-deposition additive, or an anti-corrosion additive or an anti-hydrate additive.

According to one embodiment, said recovered fluid is a production effluent of said subterranean formation comprising hydrocarbons. Alternatively, said recovered fluid is a fluid taken from an aquifer of said subterranean formation.

According to a variant, said recovered fluid is a drilling fluid.

Advantageously, at least one fluid is injected with an additive into a subterranean formation by means of at least two wells, and in which, for each well, said additive used is labeled with a nano-crystalline semiconductor light emitting in a distinct wavelength, to determine the source of the additive present in said recovered fluid. In addition, the invention relates to a method for determining at least one property of a subterranean formation, in which the operating method according to one of the preceding features is used to determine said property of the subterranean formation at means of said analysis.

Advantageously, the operating method is an enhanced hydrocarbon recovery process or a process for producing oil and / or parent rock gas.

Preferably, said property of the subterranean formation is chosen from a petrophysical property, an identification of preferential paths, an identification of preferential connections between wells of said subterranean formation, the detection of a leak during an exploitation of oils and / or source rock gas.

In addition, the invention relates to a method for optimizing the operation of an underground formation, for which the operating method according to one of the preceding features is used to detect and / or quantify the presence of additive in said recovered fluid, said method comprising a step of adapting said injected fluid and / or a step of treating said recovered fluid as a function of the presence and / or amount of additive in said recovered fluid.

According to one embodiment of the invention, the treatment step is a step of treating the water produced by an enhanced hydrocarbon recovery process depending on the amount of additive present in the produced water.

According to an alternative embodiment, the adaptation step is a step of adjusting the additives in a drilling fluid injected into said subterranean formation, the adjustment being a function of the amount of additive present in the surface fluid raised to area.

According to one characteristic of the invention, the adaptation step is a step of adjusting the additives in a fracturing fluid injected into said subterranean formation, the adjustment being a function of the amount of additive present in the fluid produced. . Advantageously, the adaptation step is a step of adjusting the anti-deposit and / or anti-hydrate and / or anti-corrosion additives in an injected fluid, the adjustment being a function of the amount of additive present in the fluid produced.

Preferably, the adaptation step is a step of adjusting the additives in an enhanced hydrocarbon recovery fluid, the adjustment being a function of the amount of additive present in the fluid produced.

Detailed description of the invention

The present invention relates to a method for operating an underground formation, in which at least one fluid is injected, the fluid comprising at least one additive. For the process according to the invention, the following steps are carried out:

1) Marking of the additive

2) Injection of the fluid

3) Recovery of a fluid from the underground formation

4) Optical analysis

The injected fluid may be an aqueous fluid or an organic solvent. It can be a drilling fluid, water, a fracturing fluid, a hydrocarbon-assisted recovery fluid, etc.

The additive of the injected fluid can take the form of organic molecules, such as polymers, copolymers (for example a polyacrylamide) and / or surfactants ... It can also take the form of inorganic compounds such as minerals (clays , barite, ...) or oxides (titanium oxides, iron oxides, ...) ...

Recovered fluid is understood to mean complex fluids comprising alone or in mixture production water, hydrocarbons, drilling fluids, fracturing fluids, waters of geological formations ... The term fluid product denotes a complex fluid comprising alone or in combination with the production water and hydrocarbons, which can be recovered by a producing well. 1) Marking of the additive

During this step, the additive is marked by a nano-crystalline semiconductor luminescent (fluorescent or phosphorescent). A nano-crystal semiconductor is also called quantum dot or quantum dot, and is also known by its English name of quantum dot. A nano-crystal semiconductor is a nanostructure of semiconductor material (s). Because of its size and characteristics, it behaves like a potential well that confines electrons (and holes), in three dimensions of space, in a region of a size of the order of the electron wavelength (De Broglie wavelength), or a few tens of nanometers in a semiconductor. The nano-crystals (or nano-particles) semiconductors are objects whose size is typically between 2 and 20 nm; these nanoparticles comprise from about 100 to 10,000 atoms. Due to their small sizes, the semiconductor nano-crystals have very specific optical properties because of the atypical behavior of the electrons due to their confinement in these nano-semiconductor crystals. Thus, the quantum boxes are known and known to be luminescent. Some semiconductor nano-crystals fluoresce with a very narrow wavelength (the half-height width of the emission peak is typically 30 nm). Other semiconductor nano-crystals are known to be phosphorescent. The quantum boxes can emit in the ultraviolet, the visible, the near infrared and the infrared. In addition, their absorption spectrum is very wide: we can therefore excite them with radiation of different wavelengths. Luminescent quantum nano-crystals have the advantage of being very bright when they emit light: they can therefore be used in small quantities, unlike organic fluorophores, which have a lower light intensity.

Thus, the fluorescence and phosphorescence characteristics of the semiconductor nano-crystals allow their use as tracers because they can be easily detected.

In addition, the other fluorescent organic molecules used in particular in the field of medical imaging (such as, for example, fluorescein isothiocyanate) lose their fluorescence property under excitation over time: this phenomenon is called photobleaching (photobleaching in English). ). This rapid decrease in the fluorescence of organic fluorophores over time is too important a limitation to consider their use in the field of the invention. On the contrary, luminescent semiconductor nanocrystals are extremely resistant to photobleaching.

The interest of quantum dots also lies in the fact that it is possible to control their optical properties by modifying their sizes, their shapes, their chemical compositions (for example, by incorporating them specific atomic elements that are generally called dopants ), their surface properties. For example, non-spherical quantum boxes, ie which are either cylindrical or platelet-shaped, have the advantage over spherical quantum boxes of emitting polarized light: this property may be an additional advantage for detecting and identify more easily the additives (organic, inorganic molecules) that one wishes to detect in the operating method according to the invention. There are different types of luminescent semiconductor nano-crystals, in particular (this list is not exhaustive):

1. Fluorescent semiconductor nanocrystals (which emit a light signal when illuminated by electromagnetic radiation) are distinguished. As examples, the following fluorescent semiconductor nanocrystals may be mentioned:

Fluorescent semiconductor nanocrystals may exist in the form of pure fluorescent semiconductor nanocrystals and consist of a single atomic element belonging to column IV of the periodic table (such as silicon or germanium).

Type II-VI semiconductor nano-crystals (because of their electronic structure) are interesting from the point of view of their optical properties and in particular of fluorescence. Among these semiconductors (which associate one or more anions with one or more cations), there are:

o Zinc sulphide (ZnS), zinc oxide (ZnO) emitting in the ultraviolet, as well as cadmium sulphide (CdS).

o Zinc selenide (ZnSe), cadmium sulphide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), lead sulphide (PbS) that emit in the ultraviolet spectrum to the infrared through the visible.

o lead telluride (PbTe), lead selenide (PbSe) for infra-red.

Fluorescent semiconductor nanocrystals may also be in the form of a semiconductor core embedded in a shell itself semiconductor. This shell makes it possible to protect the core (for example from the oxidation, and / or the leaching generated by the fluids in which the semiconducting nano-crystals are caused to circulate or to reside) and to improve the quantum yields ( ie the quality of the fluorescence). Among these monohull semiconductor nanocrystals, we find mainly:

o a cadmium selenide core (CdSe) embedded in a shell of zinc (Zn) and sulfur (S): CdSe / ZnS

o other possible examples: CdSe / ZnSe, CdSe / CdS, InP / ZnS, ... o Fluorescent semiconductor nanocrystals also exist in the form of a core coated with several shells: we speak of quantum multihull boxes. These quantum boxes have the advantages of having a lower fragility of the shell (and therefore a better protection of the heart) and to have the highest quantum yields (of the order of 80 to 90%). Examples of such quantum boxes are for example:

o CdSe / CdS / Zns

o CdSe / ZnSe / Zns

Fluorescent semiconductor nanocrystals may also be composed of three atomic elements belonging to columns I, III and VI of the periodic table. Examples of such nano-semiconductor crystals are:

o CulTe ₂

o CulnS ₂

o CdSeTe

o CdHgTe

o ZnS / Zn _1-x Cd _x S

2. There are also phosphorescent semiconductor nanocrystals (which emit a light signal for a certain period of time after having been illuminated by electromagnetic radiation). Examples that may be mentioned are the following nano-crystalline crystals:

o Zinc sulphide doped with manganese (ZnS: Mn)

o Zinc sulphide doped with europium (ZnS: Eu)

o Calcium sulphide doped with europium (CaS: Eu)

o Strontium sulphide doped with europium (SrS: Eu)

o Strontium sulphide doped with europium and dysprosium (SrS: Eu, Dy)

o Strontium sulphide doped with europium and copper (SrS: Eu, Cu)

According to one embodiment of the invention, the phosphorescent semiconductor nanocrystals can be used for their detection. In addition, luminescent nano-crystals can be used for their detection and quantitative measurement.

Luminescent semiconductor nanocrystals do not exist only in spherical form. It is possible to synthesize nano-crystals semiconductors in the form of nano-cylinders, composed for example of CdSe or luminescent nano-platelets. For example, certain compounds of the family of lanthanide oxysulfides, ie of the general formula Ln ₂ 0 ₂ S where Ln represents an element of the family of lanthanides (such as, for example, lanthanum (La), gadolinium (Gd), etc.) . Compounds of general formula Ln ₂ 0 ₂ S have a lamellar structure. Thus, it is possible to synthesize fluorescent nano-platelets having compositions such as, for example, (Na, La) ₂ O ₂ S: Tb where the lanthanide used is Terbium (the percentage being 1%), or ( Na, La) ₂ 0 ₂ S: Eu where the lanthanide used is Europium (the percentage being 4%). In each of these examples, the lanthanide oxysulfide is doped with sodium (Na).

For the process according to the invention, all families of luminescent semiconductor nanocrystals described above are suitable.

Preferably, for the process according to the invention, semiconductor nanocrystals with the best quantum efficiencies are used, such as the CdSe / CdS / Zns or CdSe / ZnSe / Zns multi-shell quantum dots and the quantum dots with hulls. ) not incorporating toxic elements (cadmium) such as InP / ZnS quantum dots.

This step of the process according to the invention consists in marking at least one additive with at least one luminescent nano-crystalline semiconductor, the additives being those used in the petroleum industry and which may be of various chemical natures. This marking can be carried out either by (chemical) grafting on the additives (for example in the case of polymers, copolymers, surfactants -monocatenaries, double-strands-, polymers or surfactants or any organic molecule grafted itself on a clay or other mineral), or by incorporation directly into the structure of the additives (for example in the case of inorganic additives such as silica, proppants, baryte, etc.) coating the additives and semiconductor nanocrystals with another material (for example, coating solid charges and semiconducting nano-crystals with a silica layer, or a layer of latex).

There are different possibilities for labeling additives with luminescent semiconductor nanocrystals. These different marking techniques (described in the literature) and adapted to the process according to the invention are listed below in a non-exhaustive manner:

- coupling by an electrostatic attraction,

- coupling by bi-functionalizing the additive (polymer, surfactant, ...) and the quantum dot (QD). For example: QD-S-CH 2 -CO-NH-Additive,

- hydrophobic attraction coupling between hydrophobic groups of the additive and hydrophobic groups on the surface of the quantum dots,

coupling by oxidation reaction between two M-OH groups, one present on the surface of a quantum dot (QD) and the other being present on the additive to be labeled, where M is a metal

(for example, Al, Si, ...):

O S-OHQD + Si-OHadditive ^→ SlQD-O-Siadditive o AI-OHQ _D + AI-OH _ADDITIVE → AI _QD -0-Al _additive

- Olation reaction coupling, which can occur when a water molecule exists on a complex surface group of either the quantum dot or the additive:

o MQ -OH _D + M i _Add _1IF ₂ -OH → Mao-OH-Madditi, + H ₂ 0

_additive -OH + M _QD -OH ₂ → M _QD -OH-M _additive + H ₂ 0

M denotes a metal (for example, Al, Si, ...)

- coupling by alkoxylation reaction,

oligomer coupling of polysialates whose chemical formulas are presented below. These oligomers of polysialates serve as a bridge between one or more quantum dots and the additives to be labeled. -O-

Poly (sialate) Poly (sialate-siloxo) Poly (sialate-disiloxo)

Coupling by the last three reactions described above are particularly useful for grafting quantum dots onto minerals such as clays which are alumino-silicates of colloidal size and which are known to have Al-OH groups and / or Si-OH at the periphery of the particles.

To "hang" quantum boxes on additives, we note that the most efficient methods described above involve functionalizing the quantum boxes; Functionalization consists of modifying the surface state of the quantum boxes by grafting chemical groups which will make it possible to establish a link with the chemical groups of the additive to be labeled. Functionalization methods have been well known since the late 1990s. The following articles describe these methods:

- Brush Jr. M., Moronne M., Gin P., Weiss S., Alivisatos A.P., 1998, Semiconductor nanocrystals as fluorescent biological labels, Science.

- Chan W.C.W., S. Nie, 1998, Quantum dot bioconjugates for ultrasensitive nonisotopic detection, Science.

The functionalization can consist of a grafting of organic ligands on the surface of the quantum dots, or a coating by a shell of a polymer (or copolymer) having the desired properties (for example, hydrophilic for uses in aqueous media, or, on the contrary, hydrophobic for uses in organic solvents). By way of example, the ligands may be amino, carboxyl, amide or thiol groups, etc.

In addition, the document: Bach LG, Islam MD R., Hong SS, KT Lim, 2013, A simple preparation of a stable CdS-polyacrylamide nanocomposite: Structure, thermal and optical properties, J. Nanosci. Nanotechnol, describes a method for grafting a quantum dot onto a polyacrylamide.

Furthermore, the document: Jeong J., Kwon E.-K., Cheong T.-C, Park H., Cho N.-H., Kim W., 2014, Synthesis of multifunctional Fe3O4-CdSe / ZnS nanoclusters coated with lipid; In the case of dendritic cell-based immunotherapy, Applied Materials and Interfaces shows that it is possible to attach quantum dots to compounds other than organic compounds, for example nano-particles of iron oxide.

Fluorescent semiconductor nanocrystals exhibit excellent fluorescence emission: the quantum yield (which is equal to the ratio of the number of photons emitted to the number of photons absorbed) is large and higher than the already known fluorescent organic molecules. Also, semiconductor nano-crystal concentrations as low as a few parts per billion (ppb) are sufficient to measure a fluorescence signal. The measurements will be all the more reliable for concentrations exceeding a few parts per million (ppm). The number of nano-crystals grafted onto the additive depends on several parameters such as the chemical nature of the additive (polymer, clay, etc.), the concentration of additive in the injected fluid, the properties of the fluids injected or the effluents. Also, depending on the intended application, the number of fluorescent nano-crystals can be grafted onto the additives to be detected in such a way that the final concentration of nano-crystals is correct in order to be able to measure a fluorescence signal, and to quantify the content. as an additive in the controlled complex fluid. In the case where it is only desired to detect the presence of an additive labeled with at least one phosphorescent semiconductor nanocrystalline crystal, the level of concentration required follows the same reasoning as that mentioned for semiconductor nano-crystals. fluorescent.

The injected fluid may comprise a single additive, which is then labeled. Alternatively, the injected fluid may comprise a plurality of additives, for which only one additive is marked, for example the additive which is the most polluting and which must be monitored, or the additive which may end up in the recovered fluid. first. For the case where the behavior of several additives in the underground formation has to be analyzed, several additives can be marked. The marking of these various additives can be carried out by grafting fluorescent semiconductor nanocrystals of different sizes which fluoresce at different wavelengths emitted, so as to distinguish the different additives during the optical analysis, and / or by grafting phosphorescent semiconductor nanocrystals. 2) Injection of the fluid

The fluid prepared with the labeled additive is injected into the subterranean formation. The injection of a fluid into an underground formation can be carried out by any method known in the field of the petroleum industry. This may include an injection of a fluid into an injector well by means of a pumping system.

3) Recovery of a fluid

This step consists in recovering a fluid, called recovered fluid, from the subterranean formation, which is used during the next analysis step. The recovered fluid comprises complex fluids comprising alone or in mixture at least one of the hydrocarbons produced by a producing well, or the water produced by a producing well, or the water taken from the underground formation, in particular the water taken from a well. aquifer of the underground formation, or a drilling fluid raised to the surface during the drilling operation ... 4) Optical Analysis

During this step, the recovered fluid is analyzed in order to determine the presence

(or lack thereof) and / or the amount of luminescent semiconductor nanocrystals in the recovered fluid. The presence, absence and / or quantity of the semiconductor nanocrystals in the recovered fluid makes it possible to determine the presence, the absence and / or the quantity of the additives in the recovered fluid. Indeed, the additives are easily detectable by virtue of the fluorescence and / or phosphorescence properties of the luminescent semiconductor nanocrystals marking the additive.

According to one embodiment of the invention, the detection of the presence of additives can be implemented by means of phosphorescent semiconductor nanocrystals.

According to one embodiment of the invention, the detection of the presence of additives and the measurement of the amount of additives can be implemented by means of luminescent semiconductor nanocrystals.

The analysis of the recovered fluid may consist of an optical analysis, such as fluorescence spectroscopy, which measures the length emitted by the semiconductor nanocrystals when they have been excited by incident radiation, or any apparatus making it possible to measure and quantify the fluorescence. From this wavelength, it can be deduced the additive present in the effluent.

The analysis of the recovered fluid may also consist in the detection of the phosphorescence of the phosphorescent semiconductor nanocrystals after they have been illuminated by electromagnetic radiation. The phosphorescence can be analyzed by a spectrofluorimeter. According to one embodiment of the invention, the optical analysis can be implemented by means of illumination (excitation by light radiation) and detection of the wavelengths emitted by illuminated recovered fluid.

With this analysis, it is possible to determine continuously and in real time the presence and / or amount of additive (s) in the recovered fluids.

According to one embodiment of the invention, the method of operation comprises injecting at least one fluid with an additive into an underground formation by means of at least two wells. For each well, the additive used is marked by a luminescent semiconductor nanocrystal emitting in a distinct wavelength, to determine the source of the additive present in the recovered fluid. Thus, in an assisted recovery method, according to an exemplary embodiment of the invention, it is possible to determine which is the most direct path between an injector well and a producing well. In a process for producing oil and / or parent-rock gas, according to an exemplary embodiment of the invention, it is possible to determine which injector well is responsible for a leak in a aquifer.

Process applications

The method of operating a subterranean formation according to the invention can be applied to all processes for which a fluid, which comprises additives, is injected into an underground formation, in particular for the processes of exploration and exploitation of an underground formation. In particular, the exploitation method according to the invention can be used in an enhanced hydrocarbon recovery process, a process for treating the water produced, a drilling method, a method for producing oils and / or bedrock gas ...

Before describing two applications of the method according to the invention, the various processes for exploring and exploiting an underground formation are briefly described. However, the method according to the invention is not limited to the applications described. Enhanced Hydrocarbon Recovery (EOR) Process

At the beginning of the operation of an oil reservoir, the pressure prevailing in the deposit is sufficient to produce the hydrocarbons in place. However, over time, the pressure in the reservoir drops and is no longer sufficient to expel the oil from the reservoir rock. After this primary recovery, it becomes necessary to compensate for this pressure drop by injecting either water or gas into the tank. This stage of production is called secondary recovery, but the rate of recovery of hydrocarbons in place is 30%. The oil industry has developed recovery techniques improved oil (EOR). These so-called tertiary recovery techniques aim to modify the mobility and / or saturation of the oil in place in the reservoir rock. Among these improved recovery techniques, we distinguish the EOR-CO2 which consists of the injection of CO2 in the reservoir, and the chemical EOR which consists of injecting solutions of surfactants, microemulsions, or solutions aqueous polymers, such as polyacrylamide, xanthan (the injection of these polymer solutions is called "polymer flooding").

One of the problems is the optimization of the EOR operations in order to produce a maximum of oil in place in the tank.

Water treatment on fields with chemical EOR

When hydrocarbons are recovered, water is also produced, either that which was initially present in the subterranean formation or that which was injected. The recovered water can be polluted by the various additives injected. As a result, this water may be unsuitable for reuse or discharge into the environment in a natural water reserve. This is why water treatment operations are planned to clean up the water produced. These operations are complex and expensive.

Process for producing oil and gas from parent rocks

The production of these unconventional oils requires the fracturing of bedrock. The most commonly used technique is hydraulic fracturing. Hydraulic fracturing involves pumping under a very high pressure a fluid containing various additives (solid particles called propellants, polymers-polyacrylamide, ... -, clays, ...) so as to crack the rock. During poorly controlled hydraulic fracturing operations, it is possible that upwellings of the fluids used for fracturing occur and cause pollution.

Well drilling method

For the drilling of a well, a fluid is injected which fulfills four functions which are: the raising of the rock cuttings, the maintenance in suspension of the cuttings during stops of circulation, the maintenance of the pore pressure at the right of the training as well as the cooling and lubrication of the drill tool. The drilling fluid contains several additives to fulfill these four functions such as viscosifiers, lubricants, defoamers, filtrate reducers, and the like. The dosage of each of the additives of the formulation of the drilling fluid is optimized so that this formulation has the desired properties. The additives can be either organic molecules, such as polymers, copolymers, associative polymers, surfactants or particles inorganic (clays, barite, etc.). However, a variation in the concentration of additive (s) results in the drilling fluid no longer fulfilling the functions mentioned above. On the drilling platform, a person is responsible for constantly checking that the properties of the drilling fluid are in accordance with the initial specifications. For this purpose, it may be advantageous to have a method for instantaneously and online dosing the concentration of certain additives contained in the drilling fluid once raised to the surface.

Method of maintaining the flow (in English flow assurance)

Such a method makes it possible to maintain the flow of hydrocarbons in the subterranean formation, by injecting a fluid comprising flow-enhancing additives, for example anti-scale additives, anti-corrosion additives, and anti-hydrate additives. Examples of anti-deposition additives are polymers (polyacrylates, polycarboxylates, etc.).

A) First application - Determination of a property of the underground formation According to a first application of the operating method according to the invention, the additive (s) labeled with at least one nano-crystalline semiconductor light emitting can be used as tracer (s) for monitoring the injection of a fluid into a subterranean formation in order to deduce the properties of this porous geological formation (in terms of permeability for example) for the purpose of optimize its operation. Thus, the optical analysis performed makes it possible to determine at least one property of the subterranean formation. The properties determined are chosen in particular from the petrophysical properties (permeability, porosity), the identification of preferential paths, or preferential connections ... The knowledge of these properties makes it possible in particular to adapt the methods of exploitation of the underground formation such as as assisted recovery processes, and oil and / or parent-gas production processes.

According to a first example, in the context of enhanced hydrocarbon recovery, the injection of additives (in particular polymers) grafted luminescent quantum boxes which serve as tracers makes it possible to know the paths taken by the polymer solutions in the tank. This makes it possible to know, for example, whether the injection into such well is effective or not, when they are detected on the surface (during their back-production). The information provided by these additives marked by luminescent quantum dots also makes it possible to optimize the fluid injection operations: for example by modifying the injection pressures, by transforming an injector well into a producing well or vice versa, etc. more, this information on the The productivity of the different wells can be used to update and recalibrate the reservoir models so as to optimize the rate of recovery of the fields in production by means of tank simulations. According to a second example, the method for determining a property of the underground formation is adapted to a process for producing oil and rock-rock gas, in which the operating method with injection of a fracturing fluid. In the process according to the invention, a recovered fluid is recovered and analyzed in an aquifer of the subterranean formation. Thus, the presence and / or amount of additive contaminating the aquifer can be determined. Indeed, in the formulation of fracturing fluids, the use of additives labeled with luminescent semiconductor nanocrystals allows easy detection of the presence of these additives in aquifers. Thus, it is possible to monitor the quality of the aquifers and their possible pollution.

For the production of oil and gas from parent rocks, the invention also makes it possible to identify the well or wells responsible for a leak by injecting labeled additives with luminescent semiconductor nano-crystals emitting at a length of the characteristic wave of each well, or even with a color code specific to each well by grafting luminescent semiconductor nanocrystals of different sizes.

For example, it can be imagined to identify which operator is at the origin of an injection leak of graft additives of semiconducting nano-crystals with a color code specific to each operator.

In addition, as a means of monitoring the integrity of aquifers and groundwater above a reservoir of source rock hydrocarbons, the monitoring authorities may, by the method of the invention, the use of fracturing fluids comprising at least one additive (ideally several additives of different chemical natures) labeled with luminescent semiconductor nanocrystals so as to be able to detect pollution quickly by identifying the well (and therefore the operator) responsible for the leak.

Advantageously, it is also conceivable to include in the formulation of fracturing fluids compounds labeled with luminescent semiconductor nanocrystals, which are known to diffuse faster or as quickly as the other components: such compounds will allow to detect an early leak, and to highlight a break in the integrity of the field.

Another advantage of the use of additives comprising luminescent semiconductor nanocrystals lies in the fact that these additives can be detected in situ by sensors installed in the aquifers, groundwater to be monitored: these sensors use the fact that semiconductor nano-crystals fluoresce or phosphoresce when excited by radiation.

B) Second application - Optimization of the exploitation

According to a second application of the operating method according to the invention, the additive (s) labeled with at least one nano-crystalline semiconductor light is / are used (s) to optimize the exploitation of an underground formation. The analysis of the semiconductor nanocrystals makes it possible to detect and / or quantify the presence of additive in the recovered fluid. Then, the application for optimizing the operation has at least one additional step that can be:

a step of adaptation of the injected fluid, in particular by adjusting the composition and / or concentration and / or the type and / or the nature and / or the flow rate, for example as an additive, of the fluid injected in time; real, and / or

a step of treating the recovered fluid, which may be a step of treating the water produced.

This additional step is performed depending on the presence and / or the amount of luminescent semiconductor nanocrystals in the recovered fluid.

According to an exemplary embodiment of the invention, the present invention can be applied to a method of enhanced hydrocarbon recovery, implementing the operating method as described above to determine the presence of additive in the produced water, and implementing a water treatment step when the additive is present in the produced water. Thus, it is possible to implement the water treatment techniques best suited to ensure that treated water meets environmental standards, thereby reducing water treatment costs and controlling the quality of the water. water treatment. In addition, it allows to detect, identify and dose the additives in the treated water to adapt the water treatment techniques used, and thus avoid implementing techniques that are too expensive and unnecessary from one point. technical and / or environmental point of view.

According to an exemplary embodiment relating to an enhanced hydrocarbon recovery process, the optimization method according to the invention can make it possible to adjust, in real time, the quantity, the nature ... of the additives (polymers, surfactants, etc.). .) in the assisted recovery fluid. Indeed, depending on the presence and / or amount of additives in the recovered fluid, it is possible to determine the conditions of the enhanced recovery so as to optimize the production of hydrocarbons. According to an exemplary embodiment relating to the drilling of a well in an underground formation, the optimization method according to the invention can make it possible to adjust in real time the quantity, the nature, of the additives in the drilling fluid. . Indeed, for the well drilling method, a drilling fluid comprising at least one additive, in particular viscosifiers, filtrate reducers, is injected. For example, the additives may be polymers (in particular a partially hydrolysed polyacrylamide). , noted HPAM), surfactants, molecules of organophilic clays, clay particles (bentonite) .... During drilling, it is important to readjust the concentrations of additives to have the good properties of drilling fluids . The drilling method according to the invention implements the operating method as described above. The method of operating the injection makes it possible to determine the concentration of the additive after returning to the surface of the drilling fluid. Thus, the method according to the invention makes it possible to determine the concentration of the additives of the drilling fluid and to readjust the concentration of these additives in the drilling fluid. In addition, according to an exemplary embodiment relating to the production of oil and / or rock gas, it is possible to recover and analyze the fluid produced in the producing well. Indeed, after hydraulic fracturing, during the production of the well, part of the fracturing fluid is reproduced. The use of additives labeled with fluorescent semiconductor nano-crystals, in particular viscosifying polymers (Hydroxypropylguar HPG or Carboxymethyl-hydroxypropyl-guar CMHPG), makes it possible to assay them easily in the water reproduced. In addition, the invention can make it possible to monitor the quality of the water of underground formations above the exploited bedrock. For this purpose, additives labeled with luminescent semiconductor nanocrystals can be incorporated into the fluids used (such as fracturing fluids). The use of such additives makes it possible to determine the presence and / or quantity of additives in underground formations (aquifers, groundwater) in which these additives are not supposed to be present. The invention then makes it possible to detect leaks generated during hydraulic fracturing of the parent rock. According to an example relating to the method of maintaining the flow, by injecting a fluid with an additive into the subterranean formation, the present invention makes it possible to determine the presence and / or the quantity of these additives in the effluent produced. This determination then makes it possible to adjust in real time the quantity, the nature, of the added additives in the injected fluid.

Claims

claims

1) A method of operating an underground formation, in which at least one fluid is injected into said subterranean formation, said injected fluid comprising at least one additive, characterized in that the following steps are carried out:

c) recovering at least one fluid from said subterranean formation; and

d) optically analyzing the presence and / or the amount of said additive labeled by said nano-crystalline semiconductor light in said recovered fluid.

2) Process according to claim 1, wherein said additive is marked by said luminescent nanoconductor crystal by grafting said luminescent nanoconductor crystal on said additive, or by incorporating said nano-crystalline semiconductor light in the structure of said additive, or by coating said additive with said luminescent semiconductor nanocrystalline in a coating layer.

3) Method according to one of the preceding claims, wherein said nano-semiconductor crystal luminescent comprises a material selected from zinc sulfide (ZnS), zinc oxide (ZnO), cadmium sulphide (CdS), zinc selenide (ZnSe), cadmium sulphide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), lead sulphide (PbS), lead telluride (PbTe), selenide lead (PbSe), the CulnSe _2, the CulnS _2, the CdSeTe, CdHgTe, and ZnS / Zni _-x Cd _x S, zinc sulfide doped with manganese (ZnS: Mn), zinc sulfide doped with of europium (ZnS: Eu), calcium sulphide doped with europium (CaS: Eu), strontium sulphide doped with europium (SrS: Eu), strontium sulphide doped with europium europium and dysprosium (SrS: Eu, Dy), strontium sulfide doped with europium and copper (SrS: Eu, Cu) 4) Method according to one of the preceding claims, wherein said nano-crystal semiconductor luminescent is in the form of a semiconductor core embedded in at least one semiconductor shell.

5) Process according to claim 4, wherein said nano-crystalline semiconductor light is in the form of a nano-crystal multihull whose composition is selected from CdSe / CdS / ZnS, CdSe / ZnSe / ZnS and InP / ZnS. 6) Method according to one of the preceding claims, wherein said nano-semiconductor crystal luminescent is composed of three atomic elements belonging to columns I, III, and VI of the periodic table. 7) Method according to one of the preceding claims, wherein said nano-semiconductor crystal luminescent whose composition is selected from zinc sulfide doped with manganese (ZnS: Mn), zinc sulphide doped with europium ( ZnS: Eu)

8) Method according to one of the preceding claims, wherein said nano-crystal luminescent semiconductor substantially has a spherical shape, nano-cylinder, or nano-wafer.

9) Method according to one of the preceding claims, wherein said additive is an organic compound such as a polymer, a copolymer, or a surfactant.

10) Method according to one of claims 1 to 8, wherein said additive is an inorganic compound such as a clay mineral, barite, or a metal oxide.

1 1) Method according to one of claims 1 to 8, wherein said additive is an anti-deposition additive, or an anticorrosive additive or an anti-hydrate additive.

12) Method according to one of the preceding claims, wherein said recovered fluid is a production effluent of said subsurface formation comprising hydrocarbons. 13) Method according to one of claims 1 to 1 1, wherein said recovered fluid is a fluid taken from an aquifer of said subterranean formation.

14) Method according to one of claims 1 to 1 1, wherein said recovered fluid is a drilling fluid.

15) A method of operating a subterranean formation according to one of the preceding claims, wherein is injected at least one fluid with an additive in a subterranean formation by means of at least two wells, and wherein for each well said additive used is labeled with a nanoscale luminescent semiconductor crystal emitting in a distinct wavelength to determine the source of the additive present in said recovered fluid. 16) A method for determining at least one property of a subterranean formation, wherein the operating method according to one of the preceding claims is implemented and said property of the subterranean formation is determined by means of said analysis.

17) The method of claim 16, wherein the operating method is an enhanced hydrocarbon recovery process or a process for producing oil and / or parent rock gas. 18) Method according to one of claims 16 or 17, wherein said property of the subterranean formation is selected from a petrophysical property, an identification of preferential paths, an identification of preferential connections between wells of said subterranean formation, the detection of leakage during exploitation of oil and / or parent rock gas.

19) Process for optimizing the operation of an underground formation, for which the operating method according to one of Claims 1 to 15 is used to detect and / or quantify the presence of additive in said fluid. recovered, said method comprising a step of adaptation of said injected fluid and / or a step of treating said recovered fluid as a function of the presence and / or amount of additive in said recovered fluid.

20) The method of claim 19, wherein the treatment step is a step of treating the water produced by an enhanced hydrocarbon recovery process depending on the amount of additive present in the produced water.

21) The method of claim 19, wherein the adaptation step is a step of adjusting the additives in a drilling fluid injected into said subterranean formation, the adjustment being a function of the amount of additive present in the fluid surfaced surface.

22) The method of claim 19, wherein the adaptation step is a step of adjusting the additives in a fracturing fluid injected into said subterranean formation, the adjustment being a function of the amount of additive present in the fluid product. 23) The method of claim 19, wherein the adaptation step is a step of adjusting the anti-deposit and / or anti-hydrate and / or anti-corrosion additives in an injected fluid, the adjustment being a function of the quantity additive present in the fluid produced.

24. The method of claim 19, wherein the adaptation step is a step of adjusting the additives in a hydrocarbon enhanced recovery fluid, the adjustment being a function of the amount of additive present in the fluid produced.