EP3436808A1

EP3436808A1 - Device for determining petrophysical parameters of an underground formation

Info

Publication number: EP3436808A1
Application number: EP17709699.7A
Authority: EP
Inventors: Adrian CEREPI; Hervé Deschamps; Bruno Garcia
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2016-04-01
Filing date: 2017-03-10
Publication date: 2019-02-06
Also published as: AU2017243937A1; FR3049711A1; MX2018011615A; US10816494B2; AU2017243937B2; BR112018068353A2; WO2017167567A1; US20190086350A1; FR3049711B1; CA3017522A1

Abstract

The invention relates to a device for determining petrophysical parameters of an underground formation, comprising at least two electrodes (EL), a means for emitting a frequency-variable electric current (MEC), and a means for measuring electrical resistivity (MRE) in terms of amplitude and phase, two of the electrodes (EL) cooperating with the emission means (MEC) and at least two of the electrodes (EL) cooperating with the means for measuring resistivity (MRE), a means for measuring a difference in electrical potential (MDP) cooperating with at least two of the electrodes (EL). The invention is particularly applicable to oil exploration and development.

Description

DEVICE FOR DETERMINING PETROPHYSICAL PARAMETERS OF A

UNDERGROUND TRAINING

The present invention relates to the field of exploration and exploitation of a fluid contained in an underground formation.

In particular, the present invention may relate to the exploration and exploitation of petroleum reservoirs, or geological gas storage sites, such as carbon dioxide (noted C0 ₂ thereafter) or methane.

Exploration and exploitation of oil deposits requires the acquisition of as precise a knowledge of underground geology as possible, in order to effectively provide a reserve assessment, a production modeling, or a pipeline management. exploitation. For example, the determination of the location of a production well or injection well within a hydrocarbon deposit, the formation of drilling mud, the completion characteristics, the choice of a process for the recovery of hydrocarbons (such as water injection for example) and the parameters necessary for the implementation of this process (such as the injection pressure, the production flow rate, etc.) need to be well known the deposit. A good knowledge of a deposit means a description as accurate as possible of the structure of the deposit studied, its petrophysical properties, or the properties of the fluids present in the deposit studied.

To acquire this knowledge, the oil industry combines measurements made in situ (during seismic surveys, measurements in wells, coring, etc.), measurements made in the laboratory (study of thin sections, permeability measurements, etc.), as well as that numerical simulations (realized by means of software, aimed at reproducing as precisely as possible the physical and / or chemical phenomena occurring in situ or at laboratory scale). This knowledge is generally formalized in the form of a mesh, known as the "geological model", each mesh comprising one or more petrophysical parameters (such as porosity, permeability, lithology). In order to reproduce or predict (ie "simulate") the actual hydrocarbon production, the tank engineering specialist implements a calculation software, called "tank simulator". The reservoir simulator is a flow simulator, which calculates the flows and pressure evolution within the reservoir represented by a "reservoir model". The results of these calculations make it possible in particular to predict and optimize exploitation schemes (definition the number of wells to be implanted, their position, the mode of assisted recovery, etc.) of the deposit studied in order to improve the flows and / or the quantities of recovered hydrocarbons.

Thus, the operation of the fluid present in an underground formation requires in particular a good knowledge of the underground formation in which the fluid of interest is trapped. The present invention aims at the determination of petrophysical parameters relating to the subterranean formation studied, at a given stage of its exploitation or throughout its exploitation, and this on the basis of electrical type measurements, preferably carried out at different scales (at the same time). laboratory scale and well scale).

State of the art

The following documents will be cited in the following description:

Binley, A., D.L., F. Fukes, M., Cassiani, G.I., 2005. The relationship between spectral induced polarization and hydraulic properties of saturated and unsaturated sandstone, Water Resources Research, Vol. 41, W12417, 2005.

Chilingar, G.V., Haroun, M., 2014. Electrokinetics for Petroleum and Environmental Engineers, book, ed. Wiley, ISBN: 978-1-1-18-84269-0, 264 pages, January 2015.

Cuevas, N., Rector, J.W., Moore, J.R., Glaser, S.D., 2009. Electrokinetic Coupling in Hydraulic Fracture Propagation, SEG International Exposition and Annual Meeting, 2009, p 1721-1725.

Daily, W., Ramirez, A., Binley, A., 2004, Remote Monitoring of Leaks in Storage Tanks Using Electrical Resistance Tomography: Application at the Hanford Site, Journal of Environmental and Engineering Geophysics, March-April 2004, Vol. 9, No. 1: pp. 1 1 -24.

Olhoeft, G. R. (1985), Low-frequency electrical properties; Geophysics, ca. 50, no. 12, pp. 2492-2503.

Onizawa, S., Matsushima, N., Ishido, T., Hase, H., Takakura, S., Nish, Y., 2009. Self-potential distribution on active volcano controlled by three-dimensional resistivity structure in Izu Oshima, Japan, Geop ys. J. Int. (2009) 178, 1,164-1,181.

Saunders, J., Jackson, M., and Pain, C. 2008. Fluid flow monitoring in oilfields using downhole measurements of electrokinetic potential, Geophysics, vol. 73, no. September 5 - October 2008, 10.1 190/1 .2959139.

Scott, JBD and Barker, RD, 2003. Determining pore-throat size in Permo-Triassic sandstones from low-frequency electrical spectroscopy, Geophysical Research Letters, Volume 30, Issue 9, May 2003. Electrical measurements of materials from underground formation are generally well known in the field of geosciences. These measures include Spontaneous Potential measurements and Induced Spectral Polarization measurements.

Spontaneous potential measurements (noted PS later) are used to improve the vision of the structure of objects in the near surface (from a few hundred meters to a few thousand meters deep) or the knowledge volumes of fluids present in an underground formation and the circulation of these fluids. For example, in the field of volcanology, the measurement of PS is used in order to highlight the presence of a rise of electrically charged hot fluids, inducing an electric signal by electrofiltration, and producing a negative PS anomaly.

In the petroleum sector, the use of PS measurements in the context of gas storage (of the natural gas and / or C0 _{2 type} ) or the production of conventional and unconventional hydrocarbons in primary production (determination water / oil / gas saturation), secondary (impact of seawater injection for example) or even tertiary (enhanced recovery oil recovery (EOR) in English, by injection of chemicals such as polymers / suffactants). For example, in the field of oil production, the document is known (Saunders et al., 2008), which models the behavior of the PS signal in a borehole during a pumping of hydrocarbons in a tank. These authors highlight the relevance of PS measurements for monitoring the propagation of the water / hydrocarbon interface with water injected during pumping. Still in the field of hydrocarbon production, the document (Chilingar and Haroun, 2014) discloses the use of electrokinetic current injection techniques to improve the assisted recovery process in tanks by injecting C0 ₂ .

Also known from the document (Cuevas et al., 2009) the use of the electrokinetic coupling coefficient in geomechanics, particularly for the monitoring of hydraulic fracturing processes. Indeed, in the oil field, the fracturing technique of the reservoir rock under the effect of the high hydraulic pressure exerted on the rock is widely used to improve the properties of a reservoir (in particular its permeability), thus allowing improve the recovery of oil in the tank. This hydraulic fracturing is accompanied by progressive openings of fractures and causes an increase in the density of the electrokinetic field and the spontaneous potential. Thus, the measurement and monitoring of this spontaneous potential PS allows to "monitor" (or monitor in real time) the opening of these fractures and to quantify the improvement of the permeability of the reservoir.

It can also be noted that there are, in the oil field, devices for Spontaneous Potential measurements at the well scale (logging measurements). We know, for example patents US 2713146 and EP 0426563 (US 5008625) which make it possible to perform Spontaneous Potential measurements in a well passing through a geological formation. Such devices are used in particular to evaluate the amount of clay in the sedimentary formations.

Induced spectral polarization (hereinafter referred to as PSI), also known as Spectral Induced Polarization (PPS), measures a complex resistivity spectrum (which can be represented by a real part R and an imaginary part X , or by an amplitude and a phase) in a given frequency range. This technique was used in mineral exploration by Conrad Schlumberger, who in 1912 observed a polarization effect on iron ore deposits. Then, its application extended to search for groundwater, saline fronts and clay lenses. It was not until the 1980s that research focused on the sensitivity of polarization to contaminants.

In particular, the document (Olhoeft, 1985) catalogs different effects of polarization of rocks (oxidation-reduction reactions, ion exchange and interaction between the organic solvent and clay) from measurements of complex electrical resistivity in the laboratory. These measurements were performed on unconsolidated samples (that is to say collected in the near surface) and under surface measurement conditions (atmospheric pressure and ambient temperature in particular). It then establishes a range of effective frequencies (that is to say, to observe the desired effects for the samples considered under the conditions considered) between 1 mHz and 10KHz. This range of frequencies is then used by different authors to carry out field measurements, especially for the detection of contaminants. Thus, following the protocol established in Olhoeft (1985), Daily et al. (2004) showed that hydrocarbon-contaminated areas could be identified by low phase values (less than 350 mrad) and amplitude and phase anomalies at frequencies between 0.01 and 100 Hz. Binley et al. (2005) show the contribution of the PSI measurement for the estimation of transport properties (ie permeability) and the determination of the water saturation state of aquifers in unsaturated zone and saturated. These authors have in particular established a 2D-3D image of PSI of the near surface and have transcribed this image into an image of permeability and water saturation of the medium. Scott and Barker (2003) have shown that the analysis of low frequency PSIs (below 100 Hz) makes it possible to directly determine the connection size of the pores in a given reservoir. Thus, these PSI measurements were in the past carried out in the field of low frequencies (maximum 10 kHz), only under surface conditions, and targeted measurements on portions of unconsolidated underground formations, c. that is to say, portions of subterranean formations of near surface. Note that there are so-called "resistivity" logging tools (for example patent EP 0384823 A1) which make it possible to measure the resistivity of an underground formation in a region around the well. However, the existing resistivity log tools measure the resistivity in single-frequency mode, the transmission frequency being for example equal to 500 Hz, or 1 kHz or 100 MHz depending on the tools used.

Thus, measurements of spontaneous potential and induced spectral polarization have already been implemented in the past. However, there is no known device or process incorporating these two types of measurements, either at the laboratory scale or at the well scale. In addition, there is no known method to date including a step of measuring the complex resistivity in a wide frequency band, and neither during laboratory measurements or during well measurements.

One of the objects of the present invention is a device integrating both a spontaneous potential measuring means and a means for measuring the complex electrical resistivity in a wide frequency band (for example between 10mHz and 30 MHz). Such an integrated device makes it possible to guarantee that the two types of measurement are made strictly under the same conditions, which increases the reliability of the measurement. This device can be declined both at the laboratory scale and at the well scale (it is a logging tool in this case). In addition, measurements made from the device according to the invention can be fully automated and / or collected and / or analyzed without human intervention.

One of the objects of the invention consists of a method implementing both the laboratory device and the well device thus described. In particular, this method can make it possible, by calibrating between the well measurements and the laboratory measurements, to quantify petrophysical parameters relating to the formation studied, such as relative permeability and water saturation. These petrophysical parameters are then useful for the determination of an optimal exploitation scheme of the formation.

The device according to the invention

In general, the subject of the invention relates to a device for the determination of petrophysical parameters of a portion of a subterranean formation comprising a fluid, said device comprising: at least two electrodes;

means for transmitting a frequency-variable electric current and means for measuring the amplitude and phase electrical resistivity, said two electrodes cooperating with said transmitting means and at least two of said electrodes co-operating with said means of transmission; measurement of resistivity;

means for measuring an electric potential difference cooperating with at least two of said electrodes;

means for automating the measurements made by said measuring means, and / or means for collecting said measurements and / or means for analyzing said measurements.

According to one embodiment of the invention, said frequencies may be in a frequency range whose lower limit is between 1 and 20 mHz, and the upper bound is between 28 and 32 MHz.

Advantageously, said electrodes may be of impolarisable metallic material.

Preferably, the number of said electrodes may be between 4 and 8, preferably 6.

According to one embodiment of the invention, a part of the electrodes may be distributed over a length of a support formed of an insulating material.

According to one embodiment of the invention, said device may be intended for laboratory measurements, said portion of said formation being a sample of said formation, for example taken by coring, and:

said support may be a flexible sleeve of substantially cylindrical shape intended to receive said sample;

said electrodes may be at least four in number and two of said electrodes are placed so as to be in contact with each of the free sections of said sample;

said length of said support may be oriented along the axis of revolution of said support. According to one embodiment of said device that may be intended for laboratory measurements, said sleeve may be a heat-shrinkable sheath and at least two of said electrodes may be stitched onto said sheath, so as to pass through said sheath.

According to an embodiment of said device that may be intended for laboratory measurements, said device may furthermore comprise means for injecting a working fluid into said sample and for regulating the flow rate of said working fluid, and means for measuring the fluid pressure in at least two locations of said sample.

According to an embodiment of said device that may be intended for laboratory measurements, said device may further comprise a hydraulic confinement cell and / or temperature control means.

According to one embodiment of said device that may be intended for laboratory measurements, said device may further comprise geochemical measurement means such as means for measuring the alkalinity, the conductivity, the major cation-anion contents, trace element contents, the dissolved gas content after sampling.

According to one embodiment of the invention, said device may be intended for measurements within at least one well drilled in said formation such as logging measurements, said portion of said formation being an area surrounding said well in which device is inserted, said device being of substantially cylindrical shape, said electrodes possibly being rings of diameter slightly greater than the diameter of said support and being able to be distributed along the axis of revolution of said cylinder.

According to an embodiment of said device that can be intended for measurements in at least one well drilled in said formation, said resistivity measuring means, said electrical potential difference measuring means, said means for measuring emission of an electric current may be intended to be placed on the surface of said formation and may cooperate with said electrodes by means of connection resistant to the pressure and temperature conditions inherent to measurements in wells. The invention also relates to a method of operating a subterranean formation comprising a fluid, from at least one sample of said formation, said formation being traversed by at least one well, said method possibly comprising at least the following steps :

i. for at least one measurement condition, at least spontaneous potential and induced spectral polarization measurements are performed on said sample by one of the embodiments of the device for laboratory measurements, and representative petrophysical parameters are determined said sample;

ii. spontaneous potential and induced spectral polarization measurements are carried out in said well by means of at least one device according to one of the embodiments of the device intended for measurements within a well;

iii. said measurements made in said well are calibrated using said measurements made on said sample and deduced petrophysical parameters representative of said formation;

iv. from said petrophysical parameters representative of said formation, an optimal exploitation scheme of said formation is defined and exploited from said diagram.

According to one embodiment of the method according to the invention, during step i), it is possible to measure:

a) a pressure gradient induced in said sample, by means of said means for measuring the fluid pressure;

b) an electric potential difference induced in said sample, by means of said means for measuring an electrical potential difference;

c) a spectral polarization induced within said sample, by means of said means for measuring the induced spectral polarization;

and said measurements a), b) and c) are repeated for different fluid flow rates and for different fluid saturations.

According to one embodiment of the method according to the invention, said measures a), b) and c) can be repeated for different confining pressures and / or different temperatures. According to one embodiment of the method according to the invention, said petrophysical parameters representative of said formation and / or of said sample may be relative permeability and / or saturation.

According to one embodiment of the method according to the invention, step ii) can be repeated as and when the said formation is used.

Other features and advantages of the method according to the invention will become apparent on reading the following description of nonlimiting examples of embodiments, with reference to the appended figures and described below.

Brief presentation of the figures - Figure 1 is an example of Spectral Polarization measurements

Induced by means of a variant of the device according to the invention, in the case of a Brauvilliers limestone sample and for different saturations S _w in brine of this sample.

Figure 2 shows an alternative embodiment of the device according to the invention for laboratory measurements.

Figure 3 shows an alternative embodiment of the device according to the invention for well measurements.

FIG. 4 shows an exemplary configuration intended for the permanent monitoring of a site for operating a fluid contained within a formation, comprising two devices according to the invention intended for well measurements.

Figure 5 shows the evolution of the electrical potential difference dV as a function of the fluid pressure variation dP for different samples from a subterranean formation.

Figure 6 shows the evolution of the relative electrokinetic coupling coefficient Cr as a function of the fluid saturation Sw, for different electrode positions illustrated in Figure 2, in the case of a Brauvilliers limestone.

Figure 7 shows the evolution of the phase angle P of the complex electrical resistivity as a function of the frequency F in the case of a Brauvilliers limestone, and for different saturations in brine Sw. Detailed description of the device

One of the objects of the invention relates to a device for an integrated measurement of the complex electrical resistivity and the spontaneous potential, with a view to determining petrophysical parameters relating to a portion of a subterranean formation comprising a fluid. These petrophysical parameters are particularly useful for defining an optimal exploitation scheme of the underground formation studied. A portion of the underground formation studied can be for example:

a sample of the formation, taken by coring, for example: in this case, the device according to the invention is intended for so-called "laboratory" measurements and is called "laboratory device according to the invention" thereafter;

an area surrounding a well drilled in the formation studied and in which the device is inserted; in this case, the device according to the invention is intended for so-called

"Logging" and is called "well device according to the invention" thereafter.

The device according to the invention comprises:

at least two electrodes;

means for transmitting a frequency-variable electric current connected to at least two electrodes;

a means for measuring the electrical resistivity in amplitude and in phase (or means for measuring complex electrical resistivity) connected to at least two other electrodes;

a means for measuring an electric potential difference, connected to at least two electrodes.

Thus, the device according to the invention makes it possible, in an integrated manner and in a single experiment, to perform at least two types of measurements: a measurement of spontaneous potential (by means of at least two of the electrodes and the means for measuring a difference of electric potential) and an induced spectral polarization measurement (by means of at least two of the electrodes, the means for transmitting a frequency-variable electric current, and the means for measuring the amplitude and phase electrical resistivity ).

Consequently, the device according to the invention makes it possible to guarantee that two types of measurements, namely measurements of Spontaneous Potential and Induced Spectral Polarization measurements, are carried out under the same experimental conditions (portion of the formation that is identical and not degraded by successive measures, positions strictly identical electrodes for both types of measurement, strictly identical pressure and temperature conditions, etc.), which increases the reliability of the measurement.

In addition, having a single integrated measurement device makes it possible, for an industrialist, to reduce the overall operating costs of the device (purchase and maintenance costs reduced to a single device, reducing the number of operations by the technician in charge of the experiments).

In addition, the combination of Spontaneous Potential measurements and Induced Spectral Polarization measurements gives access to essential petrophysical parameters for the characterization of the portion of the studied formation, and consequently for the definition of a diagram of optimal use of the training studied. This point will be more widely developed hereinafter in the description of the method according to the invention.

According to one implementation of the invention, the means for measuring the electrical resistivity in amplitude and in phase comprises a means for measuring the electrical potential difference and a means for processing the measurement of the electrical potential difference. The means for processing the electrical potential difference measurement makes it possible to determine the amplitude and the phase of the electrical potential difference measurement made for an electric current emitted at a given frequency by means of the means for emitting a current. variable frequency electric.

Furthermore, the device according to the invention comprises means for automating the measurements made by the device according to the invention, and / or a means for collecting and / or analyzing said measurements. In this way, via the automation means, the measurements to be made by the device according to the invention can be pre-programmed and do not require human intervention to manually change the measurement parameters (intensity of the injected current, sampled frequencies, etc. ) and / or the measurement conditions (surrounding pressure, temperature, fluid saturation, etc.). The means for collecting the measurements also makes it possible to collect, centralize and store all the measurements made by the device according to the invention, automatically via the means of automation, or with human intervention. Finally, the measurement analysis means, performed automatically or manually by a technician, collected by a collection means or manually by a technician, can be analyzed automatically and systematically by an analysis means. This analysis means may comprise a computer on which software is implemented to analyze the measurements from the device according to the invention. For example, this software can make it possible to draw a plurality of curves, representing the measured values as a function of different measurement parameters and / or measurement conditions, parameters and conditions which have been for example pre-programmed in advance by the specialist. . According to one embodiment of the invention, the frequencies emitted by the means for transmitting a frequency-variable electric current are between 1 μΗζ and 1 GHz. In this way, and using the means for measuring the electrical resistivity in amplitude and in phase according to the invention, it is possible to obtain an estimate of the induced spectral polarization (denoted by PSI later) in a wide range of frequencies. . FIG. 1 shows an example of a result of Induced Spectral Polarization measurements, in particular their real part R and their imaginary part X, for frequencies between 1 μΗζ and 1 GHz, the measurements having been carried out on a given sample of rock (limestone of Brauvilliers of "grainstone to oolite" type), and for different saturations S _w in brine (between 27% and 100%, the values increasing in the direction indicated by the arrow, a value of S _w = 100% corresponding to a total saturation in brine) and different types of brine (brine with 10g of NaCl and brine with 5g of NaCl in this case). We can distinguish in this figure three areas in which the PSI measurements have substantially different behaviors: that of low frequencies (D1 domain), that of medium frequencies (D2 domain), and that of high frequencies (D3 domain). So, in the field:

- low frequencies (D1 domain), that is to say for frequencies lower for example at 20 Hz (note that this frequency may be a function of materials), the PSI is particularly sensitive, in the case of a 100% brine saturation, the size of the polarizable grains, the specific surface area, the pore size, the permeability, and the Archie cementation factor, whereas in the case of a two-phase medium ( comprising water or brine, and another non-conductive fluid such as gas and / or oil), at the saturation percentage in brine S _w . It can be shown that the PSI can be characterized in the low frequency domain by two parameters: a relaxation time (also called a low frequency critical frequency) and a phase angle;

- Medium frequencies (D2 domain), that is to say for frequencies between, for example, between 20 Hz and 30 kHz, the variations of the PSI are in the form of a plateau and the PSI is sensitive in particular saturation of the medium, permeability, and specific surface;

high frequencies (domain D3), ie for frequencies greater than 0.03 MHz for example, the PSI variations are again very sensitive to frequency, which makes it possible to obtain information, in particular on the relative dielectric permittivity, saturation of the porous medium, porosity and cation exchange capacity. Preferably, the device according to the invention makes it possible to emit an electrical signal in a frequency range whose lower limit is between 1 and 20 mHz (and preferably equal to 10 mHz), and the upper bound is between 28 and 32. MHz (and preferably equal to 30 MHz), which limits the time allotted to the measurement, while allowing access to the aforementioned quantities. Indeed, as shown in FIG. 1, these limit values of the preferential frequency range are sufficient to "capture" the major trends in the variations of the complex electrical resistivity as a function of the frequency emitted, which will make it possible to deduce petrophysical parameters (such as saturation, permeability, porosity etc.) characteristics of the formation portion considered.

According to one embodiment of the invention, the Induced Spectral Polarization measurements are made for about fifty different frequency values and sampling, on a logarithmic scale, the frequency range chosen regularly.

According to one embodiment of the invention, the electrodes of the device according to the invention consist of a conductive material (such as metal) impolarisable (for example composed of silver or silver chloride). This embodiment makes it possible to carry out successive electrical measurements without having to wait for a return time of the electrodes to a neutral electrical state. Time savings on all the experiments to be performed, for a succession of frequencies within a given range and according to a given sampling step, are thus obtained.

According to one embodiment of the invention, the device comprises between four and eight electrodes, preferably six. The plurality of electrodes makes it possible to carry out measurements of electrical potential difference and / or electrical resistivity at different locations of the formation portion studied and thus to better characterize the formation portion.

Preferably, the device further comprises a support formed of an insulating material, at least a portion of the electrodes being distributed over a length of the support in question. The dimensions and the shape of the support are a function of the dimensions and the shape of the portion of the formation considered, so that the portion of the electrodes of the device distributed over a length of the support are in contact with the portion of the the training studied.

According to one embodiment of the invention in which the portion of the formation studied is a sample of the formation, taken for example by coring, the support may be a flexible sleeve, along which part of the electrodes are distributed, the dimensions of the support allowing the electrodes in question to be in contact with the sample studied when the latter is inserted into the sleeve. Since a sample taken from a subterranean formation is generally of substantially cylindrical shape, the sleeve is preferably also of substantially cylindrical shape; its circumference may be slightly greater than that of the sample, so that the sample can be inserted into the sleeve while being held.

According to one embodiment of the invention in which the portion of the formation is an area surrounding a well drilled in the formation studied, the support is substantially cylindrical in shape (a well having a very generally cylindrical shape). The electrodes are distributed along the axis of revolution of the support, and the circumference of the support is related to the circumference of said well so that the support can be inserted into the well and that the electrodes are in contact with the portion of the training to study. Advantageously, the electrodes are rings of diameter slightly greater than the diameter of the support, and fixed to said support. Reception and current emission is then possible radially in the formation studied.

First main mode of realization: device for laboratory measurements

According to an embodiment of the invention in which the device according to the invention is intended for laboratory measurements on a sample of the studied formation (said first main embodiment of the invention thereafter or else device for laboratory measurements according to the invention), two electrodes are arranged regularly along the axis of revolution of the sleeve and two other electrodes are free and may be placed so as to establish an electrical contact on each of the free sections of the Training sample inserted into the sleeve. The electrodes placed on the free sections are connected to the means for emitting the frequency-variable electric current, and the at least two other electrodes distributed on the sleeve are connected to the means for measuring the electrical resistivity in amplitude and in phase. Advantageously, all the electrodes are also connected to the electrical potential difference measurement means, for example via a multiplexer.

In a variant of this first main embodiment of the invention, the sleeve in question may comprise a heat-shrinkable sheath. This type of sheath is particularly resistant to high temperatures and high pressures while preserving the tightness of the sheath. This type of sheath is also more inert from a physicochemical point of view. Advantageously, two electrodes are stitched through the sheath (so as to pass through this sheath), and thus allow contact with the sample inserted into the sheath. These electrodes are electrically connected by means of measurements of the complex electrical resistivity, and preferably also by means of measuring the electrical potential. At least two other electrodes are in direct contact with the sample and are electrically connected to the emission means of a variable frequency electric current, and preferably also by means of electrical potential measurement.

In another variant of this first main mode of implementation of the invention, the device further comprises means for injecting a working fluid into the sample and for regulating the flow rate of said working fluid.

The means for injecting a working fluid into said sample and for regulating the flow rate of said working fluid can make it possible to carry out complex electrical resistivity measurements and spontaneous potential measurements for different types of fluids (water, oil, gas in particular) and for different respective saturation values of these fluids. This makes it possible to evaluate petrophysical parameters relating to a sample of an underground formation for different fluid saturation conditions (different fluids and for different saturations). These various measurements can in particular make it possible to draw abacuses which make it possible to inform the specialist of the petrophysical parameters expected for the formation considered, according to the various possible conditions of saturation.

A means for measuring the fluid pressure in at least two places in the sample will advantageously be combined with the means for injecting a working fluid into the sample and for regulating the flow rate of said working fluid. This measurement configuration makes it possible in particular to carry out measurements of electrokinetic coupling coefficient in a saturated medium.

Advantageously, the first main mode of implementation of the invention may further comprise a hydraulic confinement cell for receiving the sample. The confinement cell can make it possible to subject the sample of the formation in question to high pressures (for example of the order of 5 MPa). This makes it possible to simulate, in the context of a laboratory measurement, the existing pressure conditions in the underground formation, which can be of the order of 8 to 40 MPa. The measurements of spontaneous potential and electrical resistivity carried out under conditions approaching the conditions in situ (that is to say under the pressure conditions of the fluid reservoir studied), the petrophysical parameters that can be deduced from these Measurements are representative of the actual petrophysical parameters, in situ, in contrast to measurements that are performed under surface conditions (pressure of about 1 MPa).

Advantageously, the first main embodiment of the invention may further comprise a means for regulating the temperature, within said containment confinement cell, so as to simulate the temperature conditions within the studied formation (and which can reach 60 to 150 ° C). In addition, the first main mode of implementation of the invention may comprise geochemical measurement means such as means for measuring alkalinity, conductivity, major cation-anion contents, trace element contents. as well as the dissolved gas content after sampling. The specialist in the field of petroleum geochemistry has perfect knowledge of ways to carry out such measurements. These measurements make it possible to inform the specialist about the precise characteristics of the fluids and gases present, which can contribute to refine the optimal exploitation scheme targeted by the present invention.

Figure 2 shows a variant of the first main mode of implementation of the device according to the invention, the various elements of the device in question can be arranged differently. Thus, this figure describes a device comprising a support SU of cylindrical shape, 4 EL electrodes including two electrodes distributed along the support SU and two other electrodes EL free, intended to be placed on each of the free sections of the inserted training sample. in the SU holder. The electrodes EL to be placed on the free sections are connected to the means for transmitting the MEC frequency-variable electric current, and the two other electrodes EL distributed on the sleeve S S are connected to the means for measuring the electrical resistivity MRE in amplitude and frequency. phase. According to this nonlimiting embodiment of the invention, only two of the four electrodes A, D are connected to the electrical potential difference measuring means MDP, allowing measurements of spontaneous potential difference only between the electrodes A and D, but connections could be made between each of the electrodes A, B, C, D and the electrical potential difference measuring means MDP in order to allow a measurement of potential difference between the electrodes A and B, A and C, and A and D for example. Moreover, in this exemplary embodiment, the means for transmitting the frequency-variable electric current MEC, the means for measuring the electrical resistivity MRE in amplitude and in phase, and the means for measuring the electrical potential difference MDP are connected. an AUT automaton allowing the measurements to be made by the device according to the invention are pre-programmed, thus avoiding any human intervention to manually change the measurement parameters (intensity of the injected current, sampled frequencies etc).

Second main embodiment: device for logging measurements

According to an embodiment of the invention in which the device according to the invention is intended for measurements within at least one well drilled in the studied formation such as logging measurements (said second main embodiment of the invention). device according the invention, or device for well measurements thereafter), the means for measuring the complex resistivity, the electrical potential difference measuring means, the means for emitting an electric current are intended to be placed on the surface of said formation and are connected to said electrodes by connection means resistant to the pressure and temperature conditions inherent to measurements in wells.

This main embodiment of the device according to the invention allows, with a single logging tool, two types of measurement (electrical in this case), which is very advantageous from an operational point of view because the implementation Logging measurements are well known for being highly technical and costly. In addition, it is ensured in this way that the two measurements are perfectly performed at the same depth in the well and are representative of the same portion.

According to one embodiment of this second main embodiment of the invention, the electrodes are put in direct contact with the wall of the well and therefore with the geological formation. According to an embodiment of this second main embodiment of the invention, the dimensions of the device for well measurements are of the order of 2500 mm in length and 45 mm in diameter. Advantageously, the electrodes are distributed uniformly over a length of the support of 2100 mm, the distance between two consecutive electrodes being 30 mm.

Figure 3 shows a variant of the second main embodiment of the device according to the invention, for well measurements, the various elements of the device in question can be arranged differently. In the example presented, the support SU is a cylindrical tube placed in a well W drilled in a formation F, along which 7 annular electrodes EL are distributed, each electrode being connected to the means for measuring the spontaneous potential MDP and by means of measuring the complex electrical resistivity MRE, the electrodes at the two ends of the support being further connected to the means for transmitting the MEC frequency-variable electric current. In addition, the means for measuring the complex electrical resistivity MRE, the spontaneous potential MDP and the means for transmitting the frequency-variable electric current MEC are placed on the surface.

Method of operating an underground formation

In addition, the invention relates to a method of operating a subterranean formation comprising a fluid. This method requires at least one sample taken from the studied formation, the formation being traversed by at least one well, and comprises at least the following steps: Step 1: for at least one measurement condition, spontaneous potential and induced spectral polarization measurements are carried out on the sample in question by means of an embodiment of the device for laboratory measurements comprising means for injecting a sample. working fluid in the sample, means for regulating the flow of the working fluid, and a means for measuring the fluid pressure in at least two locations of said sample, and determining petrophysical parameters representative of said sample;

Step 2: Spontaneous potential and induced spectral polarization measurements are carried out in the well in question by means of at least one device according to any of the variants of the second main mode of implementation of the device according to the invention (FIG. that is, the embodiment for well measurements);

Step 3: the values of the measurements made in the well are compared with the measurements made on the said sample, and by calibration, representative of the petrophysical parameters representative of said formation are deduced;

Step 4: from said representative parameters of said formation, an optimal exploitation scheme of the fluid of the studied formation is defined and the fluid of the formation is exploited on the basis of said diagram.

Thus, the method according to the invention comprises the implementation of measurements of different types (PS and PSI at least) and at different scales (well scale and laboratory scale). We will hereinafter detail the various steps of the method according to the invention.

Step 1

During this step, the method according to the invention is implemented by means of a variant of the first main mode of implementation of the device according to the invention, comprising means for injecting a working fluid into said sample and for regulating the flow rate of said working fluid, as well as a means for measuring the fluid pressure in at least two places of said sample.

Measurements made using this device (hereinafter called "laboratory measurements") are performed for at least one measurement condition. "Measurement condition" means all the parameters according to which the measurement is carried out, such as, for example, the pressure, the temperature, the fluid or fluids present in the sample, the saturation of each of the fluids present in the sample. . Very preferably, the laboratory measurements are carried out under measurement conditions representative of the conditions (pressure, temperature, saturations of the fluids present) to which the studied formation is subjected, which will be called "conditions in situ" by the after. It should be noted that in situ conditions are not usually known but the specialist can have orders of magnitude or ranges of in situ conditions (ranges relating to pressures and / or temperatures and / or saturations of the fluids present). The laboratory measurements are advantageously carried out for a plurality of measurement conditions, in particular sampling the ranges of the presumed values of the conditions in situ.

From said laboratory measurements, petrophysical parameters relating to the sample considered for the measurement condition (s) under consideration (pressure and / or temperature and / or fluid saturation conditions) are determined. The specialist has perfect knowledge of methods for determining petrophysical parameters from measurements of PSI and PS. According to one embodiment of the invention, the petrophysical parameters representative of the sample are relative permeability and / or fluid saturation. When measurements have been made for a plurality of measurement conditions, the specialist can draw up an abacus representing the values of the measurements made, the petrophysical parameters deduced from these measurements, and this for each measurement condition.

According to one embodiment of the method according to the invention, for at least one predefined confining pressure, a temperature, a predetermined fluid saturation, a predefined fluid flow rate, and a given working fluid injection in said sample, we measure:

at. the pressure gradient induced in the sample, by means of the fluid pressure measurement means;

b. the electric potential difference induced in the sample, by means of the electric potential difference measuring means;

vs. the spectral polarization induced within said sample, by means of the means for measuring the induced spectral polarization;

and the measurements a), b) and c) are repeated for different fluid flow rates and / or for different fluid saturations and / or for different working fluids. The following nonlimiting methods for exploiting the measurements thus made to determine relative permeability and fluid saturation are described below.

Determination of petrophysical parameters

The spontaneous potential measurements make it possible to measure an electric potential difference (which will be noted dV thereafter). Combined with pressure gradient measurements (which will be noted dP later), an electrokinetic coupling coefficient C is obtained according to a formula of the type:

C = dV / dP, According to the embodiment described above, the measurements being made for different fluid saturation conditions, it is possible to define an electrokinetic coupling coefficient in saturated medium Csat and an electrokinetic coupling coefficient in unsaturated medium C (Sw < = l). We then define a relative electrokinetic coupling coefficient Cr, corresponding to the ratio between the electrokinetic coefficient in saturated medium Csat and the electrokinetic coefficient in unsaturated medium C (Sw <= 1). It is also possible to estimate a Celectw electroosmosis coefficient which quantifies the fluid pressure variation induced by an electric potential difference.

Moreover, the measurements of PSI carried out according to the implementation mode described above make it possible to measure the complex resistivity, in a saturated medium and in an unsaturated medium. From these measurements, it is possible to deduce for example the following parameters:

a phase angle Θ, from a formula of the type: tan Θ = X / R, where R is the real part of the resistivity and X is the imaginary part;

a relaxation time τ, a critical frequency Fc; a resistivity index I _R = -, where R _t and R ₀ are respectively the real part of the

R

resistivity in unsaturated medium and saturated medium;

a formation factor F = -, where Ro is the resistivity of the medium saturated at 100% with

R

brine, R _w is the resistivity of the R. brine

From the phase angle Θ, the formation factor F, the relaxation time x, and the critical frequency Fc, the specialist can deduce the fluid saturation Sw. The skilled person knows in particular the formula:

which makes it possible to deduce the saturation S _w from the formation factor F, the permeability K (which may be known elsewhere, from petrophysical measurements in the laboratory, such measurements being well known to the specialist), D _{+) is the diffusion coefficient (which can be known elsewhere, from petrophysical laboratory measurements by laboratory, such measurements being well known to the specialist or then determined by a formula).

Then, from the saturation in fluid S _w and knowing also that the index of resistivity can also be written I _R = S ^{~ n} , one deduces n, the saturation exponent of the law of Archie. The relative permeability can then be obtained according to a formula of the type: K _r = C _r S

Advantageously, the measures described above may be additionally repeated for different confining pressures and / or different temperatures. To do this, the device according to the first main mode of implementation of the device according to the invention may comprise a hydraulic containment cell and / or temperature control means. Thus, the invention makes it possible to perform laboratory measurements for different measurement conditions (pressure, temperature, fluid, and respective saturation of the fluids). In this way, the specialist can for example establish an abacus of the petrophysical parameters determined according to these measurement conditions.

2nd step

According to the method according to the invention, measurements of spontaneous potential and induced spectral polarization are also carried out in the well considered by means of the device according to any variant of the second main mode of implementation of the device according to the invention. invention. These measures will be called "well measurements" afterwards.

By comparing the values of the measurements made in the well with those made in the laboratory, the petrophysical parameters of the studied formation are determined according to the petrophysical parameters obtained by the laboratory measurements. This determination can take different forms: a direct attribution of the parameters obtained by laboratory measurements (especially if there is perfect correspondence between laboratory measurements and logging measurements), or else by interpolation of several parameters, by extrapolation, or by application of any ad hoc function. According to one embodiment of the invention, a scaling function of the measurements made in the laboratory is applied with respect to the measurements made in the well, so as to take into account the different scale factors between these two. types of measurement.

According to one embodiment of the invention, the measurements made in the laboratory are first scaled compared to the measurements made in the well, to take account of the different measurement conditions.

An example of an implementation variant of the method according to the invention is presented in FIG. 4. Thus, this variant comprises two well measurement devices, one placed in an injection well W1 and one placed in a WP production well. fluid contained in the formation studied, the two wells being spaced a hundred meters apart. For example, when the injected fluid is C0 ₂ , such a configuration can make it possible to investigate variations in Petrophysical parameters between the two wells and thus follow the front of C0 ₂ (via saturation) between the wells.

Step 3

From the petrophysical parameters thus determined for the studied formation, one can define an optimal exploitation scheme of the fluid contained in the formation studied, that is to say an exploitation diagram allowing an optimal exploitation of a fluid considered following technico-economic criteria predefined by the specialist. It can be a scenario with a high fluid recovery rate over a long operating life and requiring a limited number of wells. According to one embodiment of the invention, the optimal exploitation scheme can be defined by determining a fluid recovery process (primary, secondary or tertiary recovery process), as well as a number, an implantation and a geometry of injectors wells and / or producers to meet predefined technical and economic criteria. Different scenarios can be envisaged and their respective profitability approximated using a reservoir simulation. For example, the scenario offering the highest predicted profitability may be retained.

Step 4

Then, according to the invention, the fluid of the studied formation is exploited according to the exploitation scheme determined in step 3, best satisfying the technico-economic criteria predefined by the specialist.

The exploitation of the fluid of the studied formation can then consist of the drilling of the number and the implantation determined in step 3, some of these wells being intended to be injection wells and others well producing, injecting into the injection wells any fluids aimed at improving the recovery of fluids in place.

According to one embodiment of the invention in which the well measurements described in step 2 are repeated at different times during the operation of the fluid of the studied formation, the laboratory measurements having been carried out beforehand for various conditions From a number of measurements, the petrophysical parameters such as relative permeability and fluid saturation can be monitored in real time, as the fluid is produced. The operating scheme determined in step 3 can then be revised as exploitation of the formation fluid, and the recovery of fluid in step 4 improved. Example of realization

The characteristics and advantages of the method according to the invention will appear more clearly on reading the embodiment example below.

The exemplary embodiment in question was implemented with a device according to the first main mode of implementation of the invention (laboratory device) comprising the following elements:

Containment equipment

• A Coreflood containment cell (Vinci Technologies, France): this is an adjustable piston containment cell, with three inputs on an injection spiral, three outputs on an output spiral, and transparent to X-rays. Such a cell can make it possible to measure up to a hydraulic confining pressure of 50 bar in Marcol. The latter ensures the electrical isolation of the contacts.

• A heat-shrinkable Viton ® sheath (Hellermann-Tyton, France) equipped with 12 connections distributed along the generatrix of the sheath and making it possible to introduce the electrical contacts (2 diametrically opposite taps by electrical measurement).

Measuring and control equipment (P, T, flow)

• An ISCO 260 D type pump, with a remote pressure sensor, regulates the hydraulic pressure of the containment up to 50 bar as close as possible to the cell and absorbs pressure fluctuations related to temperature.

• Amersham / Bioscience P920 Liquid Injection Pump covers a flow rate range of 0.00 to 20.00 mL / min, and is used to inject brine into the porous media.

• A Pharmacia P500 1 - 499 mL / h liquid injection pump is used to top up the system volume following brine sampling and recirculation on the back side of the porous media, in order to maintain capillary contact and zero capillary pressure at the outlet.

A system of 3 outlet valves allows to purge the dead volumes of the cell in brine and to improve the determination of the pore volume.

• Two Keller PAA-33X pressure sensors (0-30 bar) measure the relative pressure upstream and downstream of the assembly. They also allow the control of the injection pressure at the top of the porous medium and the adjustment of the pore pressure. In addition, the downstream sensor makes it possible to balance the pressure of the sampling loop with the pore pressure after sampling, so as not to destabilize the pore pressure of the system. • A Keller PD39X pressure sensor measures the differential pressure generated by the flow in the porous medium.

• A Bronhkorst gas pressure regulator, type P702CV (Bronhkorst, France), allows to control the pore pressure up to 20 bar, by regulating the pressure of the gas fraction contained in the separator.

• A Bronkorst F-201 -CV (Bronhkorst, France) gas flow regulator, calibrated in N ₂ and C0 ₂ , covers a range of standardized pressure and temperature flow rates (P _atm and 0 ° C) of 1 at 310 mLn / min. It serves to inject the gas at the inlet of the porous medium and makes it possible to regulate the flow rate up to a pressure of 20 bar.

· A PT100 temperature sensor measures the temperature of the brine entering the porous medium. It makes it possible to correct the viscosity of the brine, the density and the resistances measured by the law of Arps.

• A brine / gas two-phase separator: placed downstream of the cell, it allows to reinject the collected brine having already passed through the porous medium. It also makes it possible to measure the volume variations resulting from the porous medium during the Kr experiment.

Equipment for measuring electrical resistivity and spontaneous potential

• A Solartron SH260: it is an impedance / Gain-Phase analyzer, allowing measurements of resistance and phase shift (R, X) in frequency sweep over a range of 1 mHz to 32 MHz, in adjustable steps. Measurements are made with the generator set to 1 Volt AC. The coupling with the Agilent multiplexer allows to work in measurement with 2 or 4 electrodes.

The Solartron also allows to inject a DC voltage from 0 to +/- 40 Volts to calculate the electro-osmosis coefficient of the system.

• An Agilent 34970A acquisition system equipped with a multiplexing board allows the acquisition of potentials between the selected sections of the porous medium.

• An acquisition unit retrieves all the measurements made on a PC, via the Labview acquisition system.

· 4 impolarisable electrodes arranged as shown in Figure 2.

Experimental protocol

Preparation and characteristics of the sample

The porous medium comes from a referenced career block. It is cored in diameter 40 mm and sawn with the saw with parallel face, under water. The samples are dried in an oven at 60 ° C. The sample is weighed dry. The geometric characteristics of the experimental sample are determined by vernier caliper: diameter and length. The sample is photographed and referenced. Setting up the sample in the cell

The sample is mounted in the Viton sheath, the electrodes are connected and the contacts checked using a multimeter. The sample and its sheath are mounted in the cell and placed under Marcol hydraulic confinement, at the chosen confining pressure (30 bar). The confining pressure is at least 15 bar greater than the pore pressure chosen for the experiment.

The sample is then placed under a primary vacuum. A brine of selected concentration is produced (here 10 g / l of NaCl), its conductivity is measured. The sample is saturated with the brine, at the pore pressure chosen for the experiment, using an Isco pump in pressure regulation.

Measurements made

The following measures are carried out:

1 - Successive measurements of spontaneous potential at each level of the sample, coupled with variations in dP (induced by a variation in flow) until the system is at a pseudo-equilibrium (ie say until the spontaneous potentials PS stabilize). This measurement makes it possible to determine the electrokinetic coupling coefficient.

2-spectral polarization measurements induced in frequency scanning, in the 100% saturated state in brine and under the flow of experimentation, with 4 electrodes (2 of injection and 2 of measurement), at 1 volt, on the range ranging from 1 mHz to 30 MHz. This measurement allows the measurement of the resistivity index (IR) when the measurement is repeated at different saturation states.

3- Spectral polarization induced spectral measurements, at 100% saturated in brine and under the flow of experimentation, with 4 electrodes, at 1 volt over the range from 1 mHz to 30 MHz. The purpose of this operation is to obtain a phase angle (phase shift between the "R" and "X"), a relaxation time, as well as a critical frequency for each section analyzed.

4- Measurements of pressure gradients at the input and output of the sample;

5- Induced potential measurements, in a range from 0 to +/- 40 volts, are performed on the entire porous medium and cause variations in dP. This type of measurement makes it possible to determine the coefficient of electro-osmosis. The first 4 previous steps were performed for different fluid saturations (drainage / imbibition steps).

The set of measurements carried out according to the experimental protocol defined below makes it possible to plot curves of variations of the measurements made as a function of the measurement conditions. Examples of such curves, also called charts are presented in Figures 5 to 7.

Thus, Figure 5 shows the variation curves of the electrical potential difference dV as a function of the fluid pressure variation dP for Brauvilliers (white rounds), Saint-Emilion limestone (black squares) type samples, and dolomites LS2 (cross). From the slopes of these curves, the electrokinetic coupling coefficient (in a saturated medium in the present case) is deduced respectively for each of the samples considered.

FIG. 6 shows the evolution of the relative electrokinetic coupling coefficient Cr as a function of the fluid saturation Sw, in the case of Brauvilliers limestone, and for different positions of the electrodes, the positions of the electrodes ABCD being presented in FIG. 2.

Figure 7 shows the evolution of the phase angle P of the complex electrical resistivity as a function of the frequency F in the case of Brauvilliers limestone, and for different saturations in brine Sw (between 27% and 100%, l increasing saturation values being represented by an arrow in Figure 7). As indicated in FIG. 7, for each saturation condition Sw, it is possible to deduce a value of the phase angle Θ (ordinate of the first peak formed by the curve), a relaxation time τ (abscissa of the first peak formed by the measurement curve) and a critical frequency Fc (abscissa of the first depression formed by the measurement curve).

Thus such curves, obtained in particular by measurements of both PS and PSI type, for different representative samples of the studied formation and for different measurement conditions, constitute abacuses, which allow the specialist, having in addition, at his disposal according to the method according to the invention, electrical measurements of the same type (that is to say type PS and PSI) carried out in the well, to make connections, between the values of the well measurements and the values of the laboratory measurements, and to deduce the petrophysical parameters in situ, such as relative permeability and fluid saturation. These petrophysical parameters are particularly useful to the specialist to define an optimal exploitation scheme of the training studied.

Claims

1. Device for the determination of petrophysical parameters of a portion of a subterranean formation comprising a fluid, characterized in that said device comprises:

at least two electrodes (EL);

means for transmitting a frequency-variable electric current (MEC) and means for measuring the amplitude and phase electrical resistivity (MRE), two of said electrodes (EL) cooperating with said emission means (MEC) ) and at least two of said electrodes (EL) cooperating with said resistivity measuring means (MRE);

means for measuring an electric potential difference (MDP) cooperating with at least two of said electrodes (EL);

means for automating (AUT) the measurements made by said measuring means, and / or a means for collecting said measurements and / or a means for analyzing said measurements.

2. Device according to claim 1, wherein said frequencies are within a frequency range whose lower limit is between 1 and 20 mHz, and the upper bound is between 28 and 32 MHz.

3. Device according to one of the preceding claims, wherein said electrodes (EL) are impolarisable metallic material.

4. Device according to one of the preceding claims, wherein the number of said electrodes (EL) is between 4 and 8, preferably 6.

5. Device according to one of the preceding claims, wherein a portion of the electrodes (EL) are distributed over a length of a support formed of an insulating material.

6. Device according to claim 5, wherein said device is intended for laboratory measurements and wherein said portion of said formation is a sample of said formation, for example taken by coring, characterized in that:

said support (SU) is a flexible sleeve of substantially cylindrical shape intended to receive said sample;

said electrodes (EL) are at least four in number and two of said electrodes (EL) are placed so as to be in contact with each of the free sections of said sample;

said length of said support (SU) is oriented along the axis of revolution of said support.

7. Device according to claim 6, wherein said sleeve is a heat-shrinkable sheath and at least two of said electrodes (EL) are stitched on said sheath, so as to pass through said sheath.

8. Device according to one of claims 6 to 7, wherein said device further comprises means for injecting a working fluid into said sample and to regulate the flow of said working fluid, and a means for measuring the fluid pressure. in at least two places of said sample.

9. Device according to one of claims 6 to 8, wherein said device further comprises a hydraulic containment cell and / or temperature control means.

10. Device according to one of claims 6 to 9, further comprising geochemical measuring means such as means for measuring alkalinity, conductivity, major cation-anion contents, trace element contents, the dissolved gas content after sampling.

1 1. Device according to claim 5, wherein said device is intended for measurements within at least one well drilled in said formation such as logging measurements, said portion of said formation being an area surrounding said well into which said device is inserted , characterized in that said support is of substantially cylindrical shape, and in that said electrodes (EL) are rings of diameter slightly greater than the diameter of said support (SU) and are distributed along the axis of revolution of said cylinder.

12. Device according to claim 1 1, wherein said resistivity measuring means (MRE), said electrical potential difference measuring means (MDP), said means for emitting an electric current (MEC) are intended to be placed on the surface of said formation and cooperate with said electrodes (EL) by connection means resistant to the pressure and temperature conditions inherent to measurements in wells.

13. A method of operating an underground formation comprising a fluid, characterized in that, from at least one sample of said formation, said formation being traversed by at least one well:

i. for at least one measurement condition, at least spontaneous potential and induced spectral polarization measurements are carried out on said sample by means of the device according to one of claims 8 to 10, and petrophysical parameters representative of said sample are determined; ii. spontaneous potential and induced spectral polarization measurements are made in said well by means of at least one device according to one of claims 1 1 to 12;

The method of claim 13, wherein in step i), measuring:

at. a pressure gradient induced in said sample, by means of said means for measuring the pressure of the fluid;

b. an electric potential difference induced in said sample, by means of said means for measuring an electrical potential difference;

vs. a spectral polarization induced within said sample, by means of said means for measuring the induced spectral polarization; and said measurements a), b) and c) are repeated for different fluid flow rates and for different fluid saturations.

The method of claim 14, wherein said measures a), b) and c) are repeated for different confining pressures and / or different temperatures.

16. Method according to one of claims 13 to 15, wherein said petrophysical parameters representative of said formation and / or said sample are relative permeability and / or saturation.

17. Method according to one of claims 13 to 16, wherein step ii) is repeated as the operation of said formation.