EP0695427A1 - Method and device for evaluating the permeability of a rock medium - Google Patents

Method and device for evaluating the permeability of a rock medium

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Publication number
EP0695427A1
EP0695427A1 EP95909840A EP95909840A EP0695427A1 EP 0695427 A1 EP0695427 A1 EP 0695427A1 EP 95909840 A EP95909840 A EP 95909840A EP 95909840 A EP95909840 A EP 95909840A EP 0695427 A1 EP0695427 A1 EP 0695427A1
Authority
EP
European Patent Office
Prior art keywords
magnetic field
rocky
permeability
medium
value
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP95909840A
Other languages
German (de)
French (fr)
Inventor
Jean-Pierre Pozzi
Jean-Pierre Martin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CGG SA
Original Assignee
Compagnie Generale de Geophysique SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Generale de Geophysique SA filed Critical Compagnie Generale de Geophysique SA
Publication of EP0695427A1 publication Critical patent/EP0695427A1/en
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
    • G01N15/082—Investigating permeability by forcing a fluid through a sample
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
    • G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
    • G01V3/265—Operating with fields produced by spontaneous potentials, e.g. electrochemicals or produced by telluric currents

Definitions

  • the present invention relates to methods and devices for evaluating the permeability of a rocky environment, finding a particularly advantageous application in the case of the in situ determination of the permeability of a geological formation, for example which surrounds a well of oil.
  • the process which is described in this document consists in positioning, in contact with the side wall of the well and substantially at a point situated at the level where the permeability must be measured, a source of excitation, in controlling this source so that it produce a transient electrokinetic potential in the rocky environment around the point of contact, measure the amplitude of this electrokinetic potential, determine a characteristic signal as a function of the response time of this electrokinetic potential created in the rocky environment, and determine the permeability of this rocky environment around the point of contact as a function of the characteristic signal.
  • the device which makes it possible to implement this process consists essentially of a tool capable of creating a transient electrokinetic potential in the rocky environment, means for positioning this tool in contact with the wall of the well substantially at a point located at the level of the environment. rocky where we want to measure permeability, means to control the tool so that it produces an excitation capable of effectively achieving the transient electrokinetic potential, at least two electrodes which are pressed against the wall of the well on the other from the excitation point to measure the electrokinetic potential, and means for processing the signal delivered by these electrodes in order to determine the permeability of the rocky medium at the excitation point.
  • This method and this device have the advantage of allowing the measurement of the permeability of geological formations, carried out in situ in wells made in these geological formations, but still have, in particular, the following drawbacks.
  • a generally significant spontaneous potential background noise surrounds the electrokinetic potential to be detected, while the latter is still very low.
  • the contact of the electrodes with the wall of the well must be constant and excellent, which is very difficult taking into account the geometry of a borehole, and the presence of mud in the well can create parasitic impedances between the electrodes and the wall. Consequently, even when it is theoretically possible, the measurement of the electrokinetic potential is not reliable and the test results supplied by the means for processing the signals delivered by the electrodes are falsified.
  • the present invention thus aims to implement a method for assessing in situ the permeability of a rocky environment, and to provide a device for implementing this method, which largely overcomes the drawbacks mentioned above.
  • the subject of the present invention is a method for evaluating the permeability of a rocky environment, characterized in that it consists:
  • the present invention also relates to a device for evaluating the permeability of a rocky medium containing a fluid in its interstices, characterized in that it comprises: - means for imparting to said interstitial fluid a relative movement with respect to said rocky medium ,
  • the single figure represents, in schematic form, an embodiment of a device according to the invention, making it possible to assess in situ the permeability of a rocky medium, in an application to a well in an oil or gas deposit natural.
  • the present invention relates to a method for evaluating the permeability of a rocky medium 100, for example a geological formation in which an oil well or the like 50 is produced.
  • the process consists first of all in filling the interstices which may be in the rocky medium, if they are not already naturally, with a given fluid, for example water or any other fluid commonly used in the wells of oil.
  • a given fluid for example water or any other fluid commonly used in the wells of oil.
  • this interstitial fluid is printed, by any means including those which are described below, a relative movement with respect to the rocky medium 100, essentially by pulses.
  • the interstitial fluid is set in motion, electric currents circulate and the circulation of these currents creates a magnetic field.
  • the method according to the invention then consists in measuring this magnetic field induced in the rocky environment by the relative displacement of the interstitial fluid with respect to the rocks of the geological formation tested.
  • the value of the measured magnetic field is preferably converted into another quantity which is proportional to it, for example an electrical signal, which can be more easily processed by various means such as memories, calculators, etc.
  • the permeability of the rocky medium is evaluated as a function of the magnetic field measured, for example by means of abacuses or using a computer whose calculation program has been developed from these abacuses. which are then essentially constituted by databases.
  • the method described above therefore makes it possible to evaluate the permeability of a rocky medium around the point where the interstitial fluid has been set in motion.
  • the method according to the invention is applied a plurality of times along this well.
  • the method consists in measuring the value of the parasitic magnetic field and the value of the total magnetic field at the location of the measurement during the excitation of the interstitial fluid, then in subtracting the value of the parasitic magnetic field, from that of the total magnetic field, to obtain the value of the induced magnetic field.
  • the invention also relates to a device for implementing the method described above, the single figure representing an embodiment of this device in the application to the measurement of the permeability of the rocky environment 100 of which, for the simplification of the description, the interstices are assumed to be already filled with the interstitial fluid mentioned in the description of the process.
  • the device comprises means 1 for imparting to the interstitial fluid a relative movement relative to the rocky environment 100, means 2 for measuring the magnetic field created by the circulation, in the rocky environment, of the electric currents produced by this movement relative of the interstitial fluid, and means 3 for determining the permeability of the rocky medium as a function of the value of the measured induced magnetic field.
  • the means 1 for imparting to the interstitial fluid a relative movement with respect to the rocky medium 100 can be constituted in different ways. In a preferred embodiment, they can be constituted by means 10 for effecting, substantially at a point 11 of the rocky medium, and more particularly of the wall 56 of the well 50, an excitation in a given direction 12 substantially perpendicular to this wall 56 and oriented towards the rocky environment.
  • these means 10 for carrying out an excitation on the interstitial fluid consist of means 13 for injecting an auxiliary pressurized fluid, such as water or the like, comprising a pump 15 controlled, for example cyclically at a given relatively low frequency, to send pulses of this auxiliary fluid into a pipe 16 which opens at point 11, in order to inject it into the rocky medium and thereby cause the relative displacement of the interstitial fluid described above.
  • an auxiliary pressurized fluid such as water or the like
  • the means 10 can be constituted by means of emission of compression waves 14 comprising a pressure chamber 17 separated from the wall 56 of the well 50, substantially at the point of excitation 11, by a flexible and elastic membrane 18, and, for example, the same pump 15 described above which sends the same pulses of fluid auxiliary under pressure, but in chamber 17. It is then the pressure created at the level of the membrane 18 which transmits the pulses.
  • This last embodiment has the advantage of separating the auxiliary fluid from the interstitial fluid and allows dynamic measurements to be made.
  • the means 2 for measuring the induced magnetic field produced by this relative movement of the fluid in the rocky environment are constituted by at least one magnetometer.
  • the device comprises two magnetometers schematically represented by two magnetic coils 21, 22 arranged substantially symmetrically with respect to a plane passing through the point 11, containing the direction 12 and substantially perpendicular to the wall 56.
  • the turns 23, 24 of the two coils are wound in the same direction with respect to the same frame of reference, so that the measurement of the magnetic field is as precise as possible. It is however clearly specified that this representation should not be taken for a limitation of the production of the means 2 to magnetic coils.
  • the device further comprises controllable means 51 , for example controllable telescopic arms or the like 53, 54, to maintain the two coils 21, 22 at a determined distance "h" from the point 1 1 defined above.
  • controllable means 51 for example controllable telescopic arms or the like 53, 54, to maintain the two coils 21, 22 at a determined distance "h" from the point 1 1 defined above.
  • the means 3 for determining the permeability of the rocky medium 100 at the excitation point 1 1 as a function of magnetic field measurement include a programmable processing unit 30 comprising at least two signal inputs 31, 32 and first 33 and second 34 means, such as differential amplifiers, for applying the signals obtained to the outputs 35, 36 of the two coils 21, 22, respectively to the two inputs 31, 32 of the processing unit 30.
  • the means 2 for measuring the value of the magnetic field defined above comprise means for measuring the value of the secondary magnetic field, means for measuring the value of the total magnetic field prevailing at point 11 during the excitation of the interstitial fluid, and means for subtracting the value of the secondary magnetic field from that of the total magnetic field.
  • the means for measuring the value of the secondary magnetic field can be of any type depending on the nature of this field and are mounted in cooperation with the means 3 so that the values which they deliver are continuously subtracted from those delivered by the means 2.
  • the value of this secondary magnetic field is known, it can be stored in the processing unit 30 and directly subtracted from the value delivered at the output of the measuring means 2.
  • This processing unit 30 is advantageously constituted, for example, by microcomputer or the like programmed to deliver at its output 37 a value representative of the measured permeability.
  • the program for this unit can be developed using deduced charts, for example, by experimentation.
  • the device comprises a tool 70 constituted, for example, by an enclosure 71 made of a preferably insulating material, capable of being lowered into the well by any means, in particular a cable 72 associated with a winch or the like situated on the surface of the ground in which this well is made.
  • This enclosure encloses all the means for carrying out, at the point 1 1, the excitation in a given direction 12 substantially perpendicular to the wall 56 of the well, all of these means being constituted by: the end of the pipe 16 or the chamber 17 with the membrane 1 8 which open on the side of the enclosure 71 by a window 74 made in the wall of this enclosure, the means 2 for measuring the magnetic field, in this case the two magnetic coils 21, 22, and the controllable means 51, for example the controllable telescopic arms or the like 53, 54, for holding the two coils 21, 22 at a determined distance "h" from point 1 1.
  • This enclosure 71 also encloses means 52 for controlling the controllable means 51, as well as means 73 which allow the enclosure to be pressed against the wall 56 so as to be able to cause optimal excitation of the interstitial fluid.
  • the means 73 which make it possible to position the enclosure in the well so that the window 74 is pressed against the wall 56 very schematically comprise a bearing 75 mounted at the end 76 of a telescopic arm 77 which passes through the wall of the enclosure 71 through an opening 78.
  • the other end 79 of this telescopic arm is for example mounted in association with a controllable gearbox 80 or the like secured to the enclosure 71.
  • the direction of this the telescopic arm 77 is substantially coincident with the excitation direction 12 defined above and the opening 78 is substantially opposite the window 74 which surrounds the excitation point 11.
  • the gearbox 80 is controlled, for example by means of an electric motor, to extend the telescopic arm 77 until the shoe 75 abuts against the wall portion 57 of the well opposite the wall portion on which the location of the excitation point is defined 1 1.
  • the shoe exerts a feedback force which makes it possible to firmly press the window 74 against the wall 56 around the excitation point 11.
  • the tool is then perfectly positioned and permeability measurement can be performed.
  • the means 52 for controlling the controllable means 51 can be advantageously coupled with these means 73, essentially at the level of the gearbox 80.
  • This box then has an outlet for each of the three telescopic arms 53, 54 and 77 which are, for example, of the "rack and pinion" type.
  • the gearbox is designed so that, by a reduction system, to an elongation of a first given value " ⁇ d "of the telescopic arm 77, corresponds to an elongation of a value equal to" 0.9 x ⁇ d "of the two telescopic arms 53, 54.
  • the distance separating the two magnetic coils 21, 22 from the excitation point 11 is thus automatically subject to the value of the diameter of the well at the level of the excitation point 11.

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  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Remote Sensing (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Biochemistry (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Electromagnetism (AREA)
  • General Health & Medical Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
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  • Geophysics And Detection Of Objects (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
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Abstract

The present description relates to methods and devices for evaluating and/or measuring the permeability of a rock medium. The method and the device of the invention are characterized essentially in that, when measuring the permeability of a rock medium (100) containing already in its interstices a fluid, means (1) are provided to confer to the fluid a motion relative to the rock medium (100), and in that the magnetic field created by the relative motion of the fluid in the rock medium is measured in order to deduce the permeability of the rock medium. The present invention finds application particularly to the in situ measurement of rock permeability, for example at the bottom of an oil well.

Description

PROCEDE ET DISPOSITIF PERMETTANT D'EVALUER LA PERMEABILITE METHOD AND DEVICE FOR ASSESSING PERMEABILITY
D'UN MILIEU ROCHEUXOF A ROCKY ENVIRONMENT
La présente invention concerne les procédés et les dispositifs permettant d'évaluer la perméabilité d'un milieu rocheux, trouvant une application particulièrement avantageuse dans le cas de la détermination in situ de la perméabilité d'une formation géologique, par exemple qui entoure un puits de pétrole.The present invention relates to methods and devices for evaluating the permeability of a rocky environment, finding a particularly advantageous application in the case of the in situ determination of the permeability of a geological formation, for example which surrounds a well of oil.
On sait que le pétrole est extrait à partir de puits réalisés dans les champs pétrolifères qui se trouvent dans de nombreux types de sols et sous-sols qui n'ont pas tous la même qualité de production. Cette qualité dépend essentiellement de la quantité de pétrole disponible, mais aussi récupérable, et donc, notamment mais non exclusivement, de la perméabilité du milieu rocheux dans lequel il se trouve emprisonné, c'est-à-dire la facilité avec laquelle le pétrole peut s'écouler jusqu'au puits pour être ensuite extrait par des techniques qui sont connues en elles-mêmes.We know that petroleum is extracted from wells made in oil fields which are found in many types of soils and subsoils which do not all have the same quality of production. This quality depends essentially on the quantity of oil available, but also recoverable, and therefore, in particular but not exclusively, on the permeability of the rocky environment in which it is trapped, that is to say the ease with which the oil can flow to the well and then be extracted by techniques which are known in themselves.
On conçoit alors l'importance qu'il y a à connaître ou à évaluer la perméabilité de toute formation géologique susceptible d'être le siège de l'exploitation d'un gisement d'un fluide, par exemple de pétrole ou de gaz naturel.We therefore understand the importance of knowing or assessing the permeability of any geological formation likely to be the site of the exploitation of a deposit of a fluid, for example petroleum or natural gas.
L'un des premiers procédés connus pour évaluer la perméabilité d'un milieu rocheux consistait à réaliser des carottes de ce milieu, puis à analyser ces carottes en laboratoire. Ce procédé présentait de nombreux inconvénients, en particulier le fait qu'il était très difficile de déduire la valeur réelle de la perméabilité du milieu rocheux à partir du résultat de mesures effectuées en laboratoire.One of the first known methods to assess the permeability of a rocky medium consisted in making cores from this medium, then in analyzing these cores in the laboratory. This process had many disadvantages, in particular the fact that it was very difficult to deduce the real value of the permeability of the rocky medium from the result of measurements carried out in the laboratory.
Pour pallier cet inconvénient, on a essayé de mettre en œuvre des procédés et de réaliser des dispositifs pour tenter d'effectuer in situ la mesure de la perméabilité d'un milieu rocheux. Du document constitué par le US-A-4 427 944, sont connus notamment un procédé et un dispositif qui permettent d'évaluer la perméabilité in situ d'un milieu rocheux, par exemple au fond d'un puits de pétrole. Le procédé qui est décrit dans ce document consiste à positionner, en contact avec la paroi latérale du puits et sensiblement en un point situé au niveau où la perméabilité doit être mesurée, une source d'excitation, à commander cette source de façon qu'elle produise un potentiel électrocinétique transitoire dans le milieu rocheux autour du point de contact, à mesurer l'amplitude de ce potentiel électrocinétique, à déterminer un signal caractéristique fonction du temps de réponse de ce potentiel électrocinétique créé dans le milieu rocheux, et à déterminer la perméabilité de ce milieu rocheux autour du point de contact en fonction du signal caractéristique. Le dispositif qui permet de mettre en œuvre ce procédé est essentiellement constitué par un outil capable de créer un potentiel électrocinétique transitoire dans le milieu rocheux, des moyens pour positionner cet outil au contact de la paroi du puits sensiblement en un point situé au niveau du milieu rocheux où l'on veut mesurer la perméabilité, des moyens pour commander l'outil afin qu'il produise un excitation capable de réaliser effectivement le potentiel électrocinétique transitoire, au moins deux électrodes qui sont plaquées contre la paroi du puits de part et d'autre du point d'excitation pour mesurer le potentiel électrocinétique, et des moyens pour traiter le signal délivré par ces électrodes afin de déterminer la perméabilité du milieu rocheux au niveau du point d'excitation.To overcome this drawback, attempts have been made to implement methods and to produce devices in an attempt to carry out in situ measurement of the permeability of a rocky environment. From the document constituted by US-A-4 427 944, a method and a device are known in particular which make it possible to evaluate the in situ permeability of a rocky medium, for example at the bottom of an oil well. The process which is described in this document consists in positioning, in contact with the side wall of the well and substantially at a point situated at the level where the permeability must be measured, a source of excitation, in controlling this source so that it produce a transient electrokinetic potential in the rocky environment around the point of contact, measure the amplitude of this electrokinetic potential, determine a characteristic signal as a function of the response time of this electrokinetic potential created in the rocky environment, and determine the permeability of this rocky environment around the point of contact as a function of the characteristic signal. The device which makes it possible to implement this process consists essentially of a tool capable of creating a transient electrokinetic potential in the rocky environment, means for positioning this tool in contact with the wall of the well substantially at a point located at the level of the environment. rocky where we want to measure permeability, means to control the tool so that it produces an excitation capable of effectively achieving the transient electrokinetic potential, at least two electrodes which are pressed against the wall of the well on the other from the excitation point to measure the electrokinetic potential, and means for processing the signal delivered by these electrodes in order to determine the permeability of the rocky medium at the excitation point.
Ce procédé et ce dispositif présentent l'avantage de permettre la mesure de la perméabilité des formations géologiques, effectuée in situ dans des puits réalisés dans ces formations géologiques, mais présentent encore, notamment, les inconvénients suivants. Un bruit de fond de potentiel spontané généralement important environne le potentiel électrocinétique à détecter, alors que ce dernier est toujours très faible. Le contact des électrodes avec la paroi du puits doit être constant et excellent, ce qui est très difficile compte tenu de la géométrie d'un forage, et la présence de boues dans le puits peut créer des impédances parasites entre les électrodes et la paroi. En conséquence, même lorsqu'elle est théoriquement possible, la mesure du potentiel électrocinétique n'est pas fiable et les résultats de test fournis par les moyens de traitement des signaux délivrés par les électrodes sont faussés.This method and this device have the advantage of allowing the measurement of the permeability of geological formations, carried out in situ in wells made in these geological formations, but still have, in particular, the following drawbacks. A generally significant spontaneous potential background noise surrounds the electrokinetic potential to be detected, while the latter is still very low. The contact of the electrodes with the wall of the well must be constant and excellent, which is very difficult taking into account the geometry of a borehole, and the presence of mud in the well can create parasitic impedances between the electrodes and the wall. Consequently, even when it is theoretically possible, the measurement of the electrokinetic potential is not reliable and the test results supplied by the means for processing the signals delivered by the electrodes are falsified.
La présente invention a ainsi pour but de mettre en œuvre un procédé pour évaluer in situ la perméabilité d'un milieu rocheux, et de réaliser un dispositif de mise en œuvre de ce procédé, qui pallient en grande partie les inconvénients mentionnés ci-dessus.The present invention thus aims to implement a method for assessing in situ the permeability of a rocky environment, and to provide a device for implementing this method, which largely overcomes the drawbacks mentioned above.
Plus précisément, la présente invention a pour objet un procédé pour évaluer la perméabilité d'un milieu rocheux, caractérisé par le fait qu'il consiste:More specifically, the subject of the present invention is a method for evaluating the permeability of a rocky environment, characterized in that it consists:
- à remplir les interstices pouvant se trouver dans ledit milieu rocheux avec un fluide donné,- filling the interstices which may be in said rocky medium with a given fluid,
- à imprimer audit fluide interstitiel un mouvement relatif par rapport audit milieu rocheux, - à mesurer le champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux, et- to impart to said interstitial fluid a relative movement with respect to said rocky medium, - to measure the magnetic field produced by the relative movement of said interstitial fluid in the rocky medium, and
- à déterminer la perméabilité dudit milieu rocheux en fonction dudit champ magnétique mesuré.- determine the permeability of said rocky environment as a function of said measured magnetic field.
La présente invention a aussi pour objet un dispositif pour évaluer la perméabilité d'un milieu rocheux contenant un fluide dans ses interstices, caractérisé par le fait qu'il comporte: - des moyens pour imprimer audit fluide interstitiel un mouvement relatif par rapport audit milieu rocheux,The present invention also relates to a device for evaluating the permeability of a rocky medium containing a fluid in its interstices, characterized in that it comprises: - means for imparting to said interstitial fluid a relative movement with respect to said rocky medium ,
- des moyens pour mesurer le champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux, etmeans for measuring the magnetic field produced by the relative movement of said interstitial fluid in the rocky environment, and
- des moyens pour déterminer la perméabilité dudit milieu rocheux en fonction de la mesure dudit champ magnétique mesuré.- Means for determining the permeability of said rocky medium as a function of the measurement of said measured magnetic field.
D'autres caractéristiques et avantages de la présente invention apparaîtront au cours de la description suivante donnée en regard des dessins annexés à titre illustratif, mais nullement limitatif, dans lesquels:Other characteristics and advantages of the present invention will appear during the following description given with reference to the drawings annexed by way of illustration, but in no way limiting, in which:
La figure unique représente, sous forme schématique, un mode de réalisation d'un dispositif selon l'invention, permettant d'évaluer in situ la perméabilité d'un milieu rocheux, dans une application à un puits dans un gisement de pétrole ou de gaz naturel.The single figure represents, in schematic form, an embodiment of a device according to the invention, making it possible to assess in situ the permeability of a rocky medium, in an application to a well in an oil or gas deposit natural.
La présente invention concerne un procédé pour évaluer l a perméabilité d'un milieu rocheux 100, par exemple une formation géologique dans laquelle est réalisé un puits de pétrole ou analogue 50.The present invention relates to a method for evaluating the permeability of a rocky medium 100, for example a geological formation in which an oil well or the like 50 is produced.
Le procédé consiste tout d'abord à remplir les interstices pouvant se trouver dans le milieu rocheux, s'ils ne le sont pas déjà naturellement, avec un fluide donné, par exemple de l'eau ou tout autre fluide couramment utilisé dans les puits de pétrole. Quand les interstices du milieu rocheux sont remplis d'un tel fluide, on imprime à ce fluide interstitiel, par tous moyens parmi lesquels ceux qui sont décrits ci-après, un mouvement relatif par rapport au milieu rocheux 100, essentiellement par impulsions. Quand le fluide interstitiel est mis en mouvement, des courants électriques circulent et la circulation de ces courants crée un champ magnétique. Le procédé selon l'invention consiste alors à mesurer ce champ magnétique induit dans le milieu rocheux par le déplacement relatif du fluide interstitiel par rapport aux roches de la formation géologique testée.The process consists first of all in filling the interstices which may be in the rocky medium, if they are not already naturally, with a given fluid, for example water or any other fluid commonly used in the wells of oil. When the interstices of the rocky medium are filled with such a fluid, this interstitial fluid is printed, by any means including those which are described below, a relative movement with respect to the rocky medium 100, essentially by pulses. When the interstitial fluid is set in motion, electric currents circulate and the circulation of these currents creates a magnetic field. The method according to the invention then consists in measuring this magnetic field induced in the rocky environment by the relative displacement of the interstitial fluid with respect to the rocks of the geological formation tested.
Pour faciliter l'évaluation de la perméabilité, la valeur du champ magnétique mesuré est préférentiellement convertie en une autre grandeur qui lui est proportionnelle, par exemple un signal électrique, qui puisse être plus facilement traitée par différents moyens comme des mémoires, des calculateurs, etc.To facilitate the evaluation of the permeability, the value of the measured magnetic field is preferably converted into another quantity which is proportional to it, for example an electrical signal, which can be more easily processed by various means such as memories, calculators, etc.
Dans la dernière étape du procédé, on évalue la perméabilité du milieu rocheux en fonction du champ magnétique mesuré, par exemple au moyen d'abaques ou à l'aide d'un ordinateur dont le programme de calcul a été élaboré à partir de ces abaques qui sont alors essentiellement constituées par des banques de données.In the last step of the method, the permeability of the rocky medium is evaluated as a function of the magnetic field measured, for example by means of abacuses or using a computer whose calculation program has been developed from these abacuses. which are then essentially constituted by databases.
Ces banques de données sont élaborées à partir par exemple d'expériences qui ont consisté à appliquer le procédé selon l'invention à des échantillons rocheux dont la perméabilité a été mesurée par des procédés antérieurs connus. Ces expériences établissent ainsi la correspondance entre des valeurs de champs magnétiques induits mesurés et celles de perméabilités connues, et leurs résultats sont enregistrés dans les mémoires des banques de données.These databases are developed from, for example, experiments which consisted in applying the method according to the invention to rock samples whose permeability has been measured by known prior methods. These experiments thus establish the correspondence between values of measured induced magnetic fields and those of known permeabilities, and their results are recorded in the memories of the data banks.
Lorsque l'on cherche à évaluer la perméabilité d'un milieu rocheux encore inconnue, il suffit ainsi de mesurer le champ magnétique induit dans ce milieu rocheux par la mise en œuvre du procédé selon l'invention décrit ci- dessus et d'interroger ces banques de données qui délivrent à leur sortie la valeur de la perméabilité qui correspond à la valeur du champ magnétique induit mesuré, la valeur de la perméabilité étant obtenue directement ou par extrapolation par rapport aux valeurs de perméabilité mémorisées.When one seeks to evaluate the permeability of a still unknown rocky environment, it suffices to measure the magnetic field induced in this rocky environment by implementing the method according to the invention described above and to question these databases which deliver at their output the value of the permeability which corresponds to the value of the induced magnetic field measured, the value of the permeability being obtained directly or by extrapolation with respect to the stored permeability values.
Le procédé décrit ci-dessus permet donc d'évaluer la perméabilité d'un milieu rocheux aux environs du point où le fluide interstitiel a été mis en mouvement. Pour évaluer la perméabilité du milieu rocheux dans son ensemble, par exemple le long d'un puits réalisé dans ce milieu rocheux, on applique une pluralité de fois le procédé selon l'invention le long de ce puits.The method described above therefore makes it possible to evaluate the permeability of a rocky medium around the point where the interstitial fluid has been set in motion. To assess the permeability of the rock environment as a whole, for example along a well made in this rock environment, the method according to the invention is applied a plurality of times along this well.
Dans ce cas cependant, il n'est pas nécessaire d'interroger les banques de données mentionnées ci-dessus après la mesure du champ magnétique induit en chaque point le long du puits. Il est en effet suffisant de connaître la valeur de la perméabilité en un seul point et de ne mesurer ensuite, en d'autres points le long du puits, que la valeur du champ magnétique induit car, comme l'expérience l'a démontré, la valeur de la perméabilité d'un milieu rocheux est proportionnelle à la valeur du champ magnétique induit mesuré. De même, s'il est suffisant de ne connaître que la variation de la perméabilité du milieu rocheux autour du puits, il suffira de mesurer la variation du champ magnétique induit mesuré le long du puits.In this case, however, it is not necessary to interrogate the databases mentioned above after measuring the magnetic field induced at each point along the well. It is indeed sufficient to know the value of the permeability at a single point and then to measure, at other points along the well, only the value of the induced magnetic field because, as experience has demonstrated, the value of the permeability of a rocky medium is proportional to the value of the measured induced magnetic field. Similarly, if it is sufficient to know only the variation in the permeability of the rocky environment around the well, it will suffice to measure the variation in the induced magnetic field measured along the well.
Il peut aussi arriver que, à l'endroit où l'on veut déterminer la perméabilité d'une formation géologique, il existe un champ magnétique secondaire considéré comme parasite par rapport au champ magnétique induit par le déplacement relatif du fluide interstitiel. Dans ce cas, le procédé consiste à mesurer la valeur du champ magnétique parasite et la valeur du champ magnétique total à l'endroit de la mesure pendant l'excitation du fluide interstitiel, puis à soustraire la valeur du champ magnétique parasite, de celle du champ magnétique total, pour obtenir la valeur du champ magnétique induit.It can also happen that, at the place where one wants to determine the permeability of a geological formation, there is a magnetic field secondary considered as parasitic compared to the magnetic field induced by the relative displacement of the interstitial fluid. In this case, the method consists in measuring the value of the parasitic magnetic field and the value of the total magnetic field at the location of the measurement during the excitation of the interstitial fluid, then in subtracting the value of the parasitic magnetic field, from that of the total magnetic field, to obtain the value of the induced magnetic field.
L'invention a également pour objet un dispositif permettant de mettre en oeuvre le procédé décrit ci-dessus, la figure unique représentant un mode de réalisation de ce dispositif dans l'application à la mesure de la perméabilité du milieu rocheux 100 dont, pour la simplification de la description, les interstices sont supposés déjà remplis du fluide interstitiel mentionné dans la description du procédé.The invention also relates to a device for implementing the method described above, the single figure representing an embodiment of this device in the application to the measurement of the permeability of the rocky environment 100 of which, for the simplification of the description, the interstices are assumed to be already filled with the interstitial fluid mentioned in the description of the process.
Ceci étant précisé, le dispositif comporte des moyens 1 pour imprimer au fluide interstitiel un mouvement relatif par rapport au milieu rocheux 100, des moyens 2 pour mesurer le champ magnétique créé par la circulation, dans le milieu rocheux, des courants électriques produit par ce mouvement relatif du fluide interstitiel, et des moyens 3 pour déterminer la perméabilité du milieu rocheux en fonction de la valeur du champ magnétique induit mesuré.This being specified, the device comprises means 1 for imparting to the interstitial fluid a relative movement relative to the rocky environment 100, means 2 for measuring the magnetic field created by the circulation, in the rocky environment, of the electric currents produced by this movement relative of the interstitial fluid, and means 3 for determining the permeability of the rocky medium as a function of the value of the measured induced magnetic field.
Les moyens 1 pour imprimer au fluide interstitiel un mouvement relatif par rapport au milieu rocheux 100 peuvent être constitués de différentes façons. Dans un mode de réalisation préférentiel, ils peuvent être constitués par des moyens 10 pour effectuer, sensiblement en un point 11 du milieu rocheux, et plus particulièrement de la paroi 56 du puits 50, une excitation suivant une direction donnée 12 sensiblement perpendiculaire à cette paroi 56 et orientée vers le milieu rocheux.The means 1 for imparting to the interstitial fluid a relative movement with respect to the rocky medium 100 can be constituted in different ways. In a preferred embodiment, they can be constituted by means 10 for effecting, substantially at a point 11 of the rocky medium, and more particularly of the wall 56 of the well 50, an excitation in a given direction 12 substantially perpendicular to this wall 56 and oriented towards the rocky environment.
Dans une réalisation possible, ces moyens 10 pour effectuer une excitation sur le fluide interstitiel sont constitués par des moyens d'injection 13 d'un fluide auxiliaire sous pression, comme de l'eau ou analogue, comportant une pompe 15 commandée, par exemple cycliquement à une fréquence donnée relativement faible, pour envoyer des impulsions de ce fluide auxiliaire dans une conduite 16 qui débouche au point 11, afin de l'injecter dans le milieu rocheux et provoquer de ce fait le déplacement relatif du fluide interstitiel décrit ci-avant.In one possible embodiment, these means 10 for carrying out an excitation on the interstitial fluid consist of means 13 for injecting an auxiliary pressurized fluid, such as water or the like, comprising a pump 15 controlled, for example cyclically at a given relatively low frequency, to send pulses of this auxiliary fluid into a pipe 16 which opens at point 11, in order to inject it into the rocky medium and thereby cause the relative displacement of the interstitial fluid described above.
Selon un autre mode de réalisation, les moyens 10 peuvent être constitués par des moyens d'émission d'ondes de compression 14 comportant une chambre de pression 17 séparée de la paroi 56 du puits 50, sensiblement au point d'excitation 11, par une membrane souple et élastique 18, et, par exemple, la même pompe 15 décrite ci-dessus qui envoie les mêmes impulsions de fluide auxiliaire sous pression, mais dans la chambre 17. C'est alors la pression créée au niveau de la membrane 18 qui transmet les impulsions. Cette dernière réalisation présente l'avantage de séparer le fluide auxiliaire du fluide interstitiel et permet d'effectuer des mesures en dynamique.According to another embodiment, the means 10 can be constituted by means of emission of compression waves 14 comprising a pressure chamber 17 separated from the wall 56 of the well 50, substantially at the point of excitation 11, by a flexible and elastic membrane 18, and, for example, the same pump 15 described above which sends the same pulses of fluid auxiliary under pressure, but in chamber 17. It is then the pressure created at the level of the membrane 18 which transmits the pulses. This last embodiment has the advantage of separating the auxiliary fluid from the interstitial fluid and allows dynamic measurements to be made.
Quel que soit le mode de réalisation des moyens 10 pour provoquer le déplacement relatif du fluide interstitiel par rapport au milieu rocheux, il est avantageux que les moyens 2 pour mesurer le champ magnétique induit produit par ce mouvement relatif du fluide dans le milieu rocheux soient constitués par au moins un magnétomètre.Whatever the embodiment of the means 10 for causing the relative displacement of the interstitial fluid with respect to the rocky environment, it is advantageous that the means 2 for measuring the induced magnetic field produced by this relative movement of the fluid in the rocky environment are constituted by at least one magnetometer.
Dans l'exemple illustré sur la figure unique, le dispositif comporte deux magnétomètres schématiquement représentés par deux bobines magnétiques 21, 22 disposées sensiblement symétriquement par rapport à un plan passant par le point 11, contenant la direction 12 et sensiblement perpendiculaire à la paroi 56. De façon avantageuse, les spires 23, 24 des deux bobines sont enroulées dans le même sens par rapport à un même référentiel, pour que la mesure du champ magnétique soit la plus précise possible. II est cependant bien précisé que cette représentation ne doit pas être prise pour une limitation de la réalisation des moyens 2 à des bobines magnétiques.In the example illustrated in the single figure, the device comprises two magnetometers schematically represented by two magnetic coils 21, 22 arranged substantially symmetrically with respect to a plane passing through the point 11, containing the direction 12 and substantially perpendicular to the wall 56. Advantageously, the turns 23, 24 of the two coils are wound in the same direction with respect to the same frame of reference, so that the measurement of the magnetic field is as precise as possible. It is however clearly specified that this representation should not be taken for a limitation of the production of the means 2 to magnetic coils.
Dans une réalisation plus spécialement adaptée à la mesure de la perméabilité in situ du milieu rocheux 100 que traverse un puits de forage 50 d'un diamètre d'une valeur par exemple désignée par "d", le dispositif comporte en outre des moyens commandables 51, par exemple des bras télescopiques commandables ou analogues 53, 54, pour maintenir les deux bobines 21, 22 à une distance déterminée "h" du point 1 1 défini ci-avant. Ces moyens permettent en outre de maintenir les deux bobines à une certaine distance de la paroi 56 du puits 50, ce qui leur évite d'être au contact de cette paroi.In an embodiment more specially adapted for measuring the in situ permeability of the rocky medium 100 through which a borehole 50 with a diameter of a value, for example designated by "d" passes, the device further comprises controllable means 51 , for example controllable telescopic arms or the like 53, 54, to maintain the two coils 21, 22 at a determined distance "h" from the point 1 1 defined above. These means also make it possible to maintain the two coils at a certain distance from the wall 56 of the well 50, which prevents them from being in contact with this wall.
11 est à noter que les Demandeurs ont trouvé que les signaux délivrés par les bobines ont une amplitude maximale lorsque "h" est sensiblement égale aux neuf dixièmes de "d" (h » 0,9 x d), et que les axes 25, 26 des deux bobines 21, 22 sont sensiblement parallèles entre eux et perpendiculaires à la direction 12. Dans un mode de réalisation préférentiel du dispositif, les moyens 3 pour déterminer la perméabilité du milieu rocheux 100 au niveau du point d'excitation 1 1 en fonction de la mesure du champ magnétique comprennent une unité de traitement programmable 30 comportant au moins deux entrées de signaux 31, 32 et des premier 33 et second 34 moyens, comme des amplificateurs différentiels, pour appliquer les signaux obtenus aux sorties 35, 36 des deux bobines 21, 22, respectivement aux deux entrées 31, 32 de l'unité de traitement 30.It should be noted that the Applicants have found that the signals delivered by the coils have a maximum amplitude when "h" is substantially equal to nine tenths of "d" (h "0.9 xd), and that the axes 25, 26 of the two coils 21, 22 are substantially parallel to each other and perpendicular to the direction 12. In a preferred embodiment of the device, the means 3 for determining the permeability of the rocky medium 100 at the excitation point 1 1 as a function of magnetic field measurement include a programmable processing unit 30 comprising at least two signal inputs 31, 32 and first 33 and second 34 means, such as differential amplifiers, for applying the signals obtained to the outputs 35, 36 of the two coils 21, 22, respectively to the two inputs 31, 32 of the processing unit 30.
Quand il existe, à l'endroit du point d'excitation 11, un champ magnétique secondaire, tel que le champ magnétique terrestre et/ou le champ magnétique rémanent des roches, considéré comme champ parasite par rapport au champ magnétique induit par le mouvement relatif du fluide interstitiel, les moyens de mesure 2 de la valeur du champ magnétique définis ci-dessus comportent des moyens pour mesurer la valeur du champ magnétique secondaire, des moyens pour mesurer la valeur du champ magnétique total régnant au niveau du point 11 pendant l'excitation du fluide interstitiel, et des moyens pour soustraire la valeur du champ magnétique secondaire, de celle du champ magnétique total.When there exists, at the location of the excitation point 11, a secondary magnetic field, such as the terrestrial magnetic field and / or the remanent magnetic field of rocks, considered as a parasitic field with respect to the magnetic field induced by relative motion of the interstitial fluid, the means 2 for measuring the value of the magnetic field defined above comprise means for measuring the value of the secondary magnetic field, means for measuring the value of the total magnetic field prevailing at point 11 during the excitation of the interstitial fluid, and means for subtracting the value of the secondary magnetic field from that of the total magnetic field.
Les moyens pour mesurer la valeur du champ magnétique secondaire peuvent être de tout type selon la nature de ce champ et sont montés en coopération avec les moyens 3 pour que les valeurs qu'ils délivrent soient soustraites en continu de celles délivrées par les moyens 2. Lorsque la valeur de ce champ magnétique secondaire est connue, elle peut être mise en mémoire dans l'unité de traitement 30 et directement soustraite de la valeur délivrée à la sortie des moyens de mesure 2.The means for measuring the value of the secondary magnetic field can be of any type depending on the nature of this field and are mounted in cooperation with the means 3 so that the values which they deliver are continuously subtracted from those delivered by the means 2. When the value of this secondary magnetic field is known, it can be stored in the processing unit 30 and directly subtracted from the value delivered at the output of the measuring means 2.
Cette unité de traitement 30 est avantageusement constituée, par exemple, par micro-ordinateur ou analogue programmé pour délivrer en sa sortie 37 une valeur représentative de la perméabilité mesurée. Le programme de cette unité peut être élaboré au moyen d'abaques déduites, par exemple, par expérimentation.This processing unit 30 is advantageously constituted, for example, by microcomputer or the like programmed to deliver at its output 37 a value representative of the measured permeability. The program for this unit can be developed using deduced charts, for example, by experimentation.
Dans l'application avantageuse de l'utilisation du dispositif selon l'invention, à la mesure de la perméabilité du milieu rocheux traversé par un puits de forage comme illustré sur la figure unique, le dispositif comporte un outil 70 constitué, par exemple, par une enceinte 71 en un matériau de préférence isolant, apte à être descendu dans le puits par tout moyen, notamment un câble 72 associé à un treuil ou analogue situé à la surface du sol dans lequel est réalisé ce puits. Cette enceinte enferme l'ensemble des moyens pour réaliser, au niveau du point 1 1, l'excitation suivant une direction donnée 12 sensiblement perpendiculaire à la paroi 56 du puits, l'ensemble de ces moyens étant constitué par: l'extrémité de la conduite 16 ou la chambre 17 avec la membrane 1 8 qui débouchent sur le côté de l'enceinte 71 par une fenêtre 74 réalisée dans la paroi de cette enceinte, les moyens 2 pour mesurer le champ magnétique, en l'occurrence les deux bobines magnétiques 21, 22, et les moyens commandables 51, par exemple les bras télescopiques commandables ou analogues 53, 54, pour maintenir les deux bobines 21, 22 à une distance déterminée "h" du point 1 1.In the advantageous application of the use of the device according to the invention, to measure the permeability of the rocky medium traversed by a wellbore as illustrated in the single figure, the device comprises a tool 70 constituted, for example, by an enclosure 71 made of a preferably insulating material, capable of being lowered into the well by any means, in particular a cable 72 associated with a winch or the like situated on the surface of the ground in which this well is made. This enclosure encloses all the means for carrying out, at the point 1 1, the excitation in a given direction 12 substantially perpendicular to the wall 56 of the well, all of these means being constituted by: the end of the pipe 16 or the chamber 17 with the membrane 1 8 which open on the side of the enclosure 71 by a window 74 made in the wall of this enclosure, the means 2 for measuring the magnetic field, in this case the two magnetic coils 21, 22, and the controllable means 51, for example the controllable telescopic arms or the like 53, 54, for holding the two coils 21, 22 at a determined distance "h" from point 1 1.
Celle enceinte 71 enferme aussi des moyens 52 pour commander les moyens commandables 51, ainsi que des moyens 73 qui permettent de plaquer celle enceinte contre la paroi 56 de façon à pouvoir provoquer une excitation optimale du fluide interstitiel.This enclosure 71 also encloses means 52 for controlling the controllable means 51, as well as means 73 which allow the enclosure to be pressed against the wall 56 so as to be able to cause optimal excitation of the interstitial fluid.
Dans une mode de réalisation avantageux, les moyens 73 qui permettent de positionner l'enceinte dans le puits de façon que la fenêtre 74 soit plaquée contre la paroi 56 comportent très schématiquement un palin 75 monté à l'extrémité 76 d'un bras télescopique 77 qui traverse la paroi de l'enceinte 71 par une ouverture 78. L'autre extrémité 79 de ce bras télescopique est par exemple montée en association avec une boîte d'engrenages commandable 80 ou analogue solidaire de l'enceinte 71. La direction de ce bras lélescopique 77 est sensiblement confondue avec la direction 12 d'excitation définie ci-avant et l'ouverture 78 est sensiblement opposée à la fenêtre 74 qui entoure le point d'excitation 11.In an advantageous embodiment, the means 73 which make it possible to position the enclosure in the well so that the window 74 is pressed against the wall 56 very schematically comprise a bearing 75 mounted at the end 76 of a telescopic arm 77 which passes through the wall of the enclosure 71 through an opening 78. The other end 79 of this telescopic arm is for example mounted in association with a controllable gearbox 80 or the like secured to the enclosure 71. The direction of this the telescopic arm 77 is substantially coincident with the excitation direction 12 defined above and the opening 78 is substantially opposite the window 74 which surrounds the excitation point 11.
De cette façon, lorsque l'enceinte est descendue en un point donné à l'intérieur du puits et que l'on veut effectuer une mesure de la perméabilité sensiblement au niveau de ce point, on commande la boîte d'engrenages 80, par exemple au moyen d'un moteur électrique, pour allonger le bras télescopique 77 jusqu'à ce que le patin 75 vienne buter contre la portion de paroi 57 du puits opposée à la portion de paroi sur laquelle est défini l'emplacement du point d'excitation 1 1. En s'appuyant sur cetle portion de paroi 57, le patin exerce une force de contre-réaction qui permet de plaquer fermement la fenêtre 74 contre la paroi 56 autour du point d'excitation 11. L'outil est alors parfaitement positionné et la mesure de la perméabilité peut être effectuée.In this way, when the enclosure is lowered to a given point inside the well and it is desired to make a measurement of the permeability substantially at this point, the gearbox 80 is controlled, for example by means of an electric motor, to extend the telescopic arm 77 until the shoe 75 abuts against the wall portion 57 of the well opposite the wall portion on which the location of the excitation point is defined 1 1. By resting on this wall portion 57, the shoe exerts a feedback force which makes it possible to firmly press the window 74 against the wall 56 around the excitation point 11. The tool is then perfectly positioned and permeability measurement can be performed.
Lorsque les moyens 73 sont réalisés comme décrit ci-dessus, les moyens 52 pour commander les moyens commandables 51 peuvent être avantageusement couplés avec ces moyens 73, essentiellement au niveau de la boîte d'engrenages 80.When the means 73 are produced as described above, the means 52 for controlling the controllable means 51 can be advantageously coupled with these means 73, essentially at the level of the gearbox 80.
Celle boîte comporte alors une sortie pour chacun des trois bras télescopiques 53, 54 et 77 qui sont par exemple du lype "à crémaillère". Dans le cas de l'application à la mesure de la perméabilité d'un milieu rocheux traversé par un puits de forage, la boîte d'engrenages est conçue de façon que, par un système de démultiplication, à un allongement d'une première valeur donnée "Δd" du bras télescopique 77, correspond un allongement d'une valeur égale à "0,9 x Δd" des deux bras télescopiques 53, 54. La distance séparant les deux bobines magnétiques 21, 22 du point d'excitation 11 est ainsi automatiquement asservie à la valeur du diamètre du puits au niveau du point d'excitation 11.This box then has an outlet for each of the three telescopic arms 53, 54 and 77 which are, for example, of the "rack and pinion" type. In the in the case of application to the measurement of the permeability of a rocky medium traversed by a wellbore, the gearbox is designed so that, by a reduction system, to an elongation of a first given value " Δd "of the telescopic arm 77, corresponds to an elongation of a value equal to" 0.9 x Δd "of the two telescopic arms 53, 54. The distance separating the two magnetic coils 21, 22 from the excitation point 11 is thus automatically subject to the value of the diameter of the well at the level of the excitation point 11.
Bien entendu, le mode de réalisation des moyens essentiellement constitués par les bras télescopiques 53, 54, 77 et la boîte 80 décrit ci-dessus n'est donné qu'à titre d'exemple et l'homme du métier connaissant les fonctions de ces moyens peut aisément en trouver d'autres.Of course, the embodiment of the means essentially constituted by the telescopic arms 53, 54, 77 and the box 80 described above is given only by way of example and the person skilled in the art knowing the functions of these means can easily find others.
Les Demandeurs ont trouvé que les mesures effectuées à l'aide du procédé et du dispositif décrits ci-dessus étaient plus représentatives de la perméabilité du volume des roches sollicitées par la source d'excitation que celles qui étaient obtenues à partir des procédés et dispositifs selon l'art antérieur, et donc beaucoup plus fiables. The Applicants have found that the measurements carried out using the method and the device described above were more representative of the permeability of the volume of the rocks solicited by the excitation source than those which were obtained from the methods and devices according to the prior art, and therefore much more reliable.

Claims

R E V E N D I C A T I O N S
1. Procédé pour évaluer la perméabilité d'un milieu rocheux ( 100), caractérisé par le fait qu'il consiste:1. Method for evaluating the permeability of a rocky medium (100), characterized in that it consists:
- à remplir les interstices pouvant se trouver dans ledit milieu rocheux avec un fluide donné,- filling the interstices which may be in said rocky medium with a given fluid,
- à imprimer audit fluide interstitiel un mouvement relatif par rapport audit milieu rocheux, - à mesurer le champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux, et- to impart to said interstitial fluid a relative movement with respect to said rocky medium, - to measure the magnetic field produced by the relative movement of said interstitial fluid in the rocky medium, and
- à déterminer la perméabilité dudit milieu rocheux en fonction dudit champ magnétique mesuré.- Determining the permeability of said rocky medium as a function of said measured magnetic field.
2. Procédé selon la revendication 1, caractérisé par le fait que, lorsqu'un champ magnétique secondaire règne dans le milieu rocheux, il consiste à mesurer la valeur du champ magnétique secondaire, à mesurer la valeur du champ magnétique total lorsque le fluide interstitiel est mis en mouvement relatif par rapport au milieu rocheux et à soustraire la valeur du champ magnétique secondaire, de celle du champ magnétique total. 2. Method according to claim 1, characterized in that, when a secondary magnetic field prevails in the rocky medium, it consists in measuring the value of the secondary magnetic field, in measuring the value of the total magnetic field when the interstitial fluid is set in relative motion with respect to the rocky environment and to subtract the value of the secondary magnetic field from that of the total magnetic field.
3. Dispositif pour évaluer la perméabilité d'un milieu rocheux ( 100) contenant un fluide dans ses interstices, caractérisé par le fait qu'il comporte:3. Device for evaluating the permeability of a rocky medium (100) containing a fluid in its interstices, characterized in that it comprises:
- des moyens ( 1 ) pour imprimer audit fluide interstitiel un mouvement relatif par rapport audit milieu rocheux (100),- means (1) for imparting to said interstitial fluid a relative movement with respect to said rocky medium (100),
- des moyens (2) pour mesurer le champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux, et- means (2) for measuring the magnetic field produced by the relative movement of said interstitial fluid in the rocky environment, and
- des moyens (3) pour déterminer la perméabilité dudit milieu rocheux en fonction de la mesure dudit champ magnétique mesuré.- Means (3) for determining the permeability of said rocky medium as a function of the measurement of said measured magnetic field.
4. Dispositif selon la revendication 3, caractérisé par le fait que les moyens ( 1) pour imprimer audit fluide interstitiel un mouvement relatif par rapport audit milieu rocheux (100) sont constitués par des moyens ( 10) pour effectuer, sensiblement en un point (11) dudit milieu rocheux, une excitation suivant une direction donnée (12), et que les moyens (2) pour mesurer le champ magnétique produit par le mouvement relatif du fluide interstitiel dans le milieu rocheux sont constitués par au moins une bobine magnétique (21 , 22).4. Device according to claim 3, characterized in that the means (1) for imparting to said interstitial fluid a relative movement relative to said rocky medium (100) are constituted by means (10) for effecting, substantially at a point ( 11) of said rocky medium, an excitation in a given direction (12), and that the means (2) for measuring the magnetic field produced by the relative movement of the interstitial fluid in the rocky medium consist of at least one magnetic coil (21 , 22).
5. Dispositif selon la revendication 4, caractérisé par le fait qu'il comporte au moins deux bobines magnétiques (21, 22) disposées sensiblement symétriquement par rapport à un plan passant par ledit point d'excitation ( 1 1) et contenant ladite direction ( 12), les deux bobines magnétiques comportant des spires (23, 24) enroulées dans le même sens par rapport à un même référentiel. 5. Device according to claim 4, characterized in that it comprises at least two magnetic coils (21, 22) arranged substantially symmetrically with respect to a plane passing through said excitation point (1 1) and containing said direction (12), the two magnetic coils comprising turns (23, 24) wound in the same direction with respect to the same frame of reference.
6. Dispositif selon la revendication 5, caractérisé par le fait que, lorsque la mesure de la perméabilité du milieu rocheux ( 100) est effectuée dans un puits de forage (50) d'un diamètre (d) donné, il comporte des moyens commandables (51) pour maintenir les deux dites bobines (21, 22) à une distance déterminée (h) dudit point ( 1 1) qui est fonction de la valeur du diamètre (d) dudit puits (50).6. Device according to claim 5, characterized in that, when the measurement of the permeability of the rocky medium (100) is carried out in a wellbore (50) of a given diameter (d), it comprises controllable means (51) to maintain the two said coils (21, 22) at a determined distance (h) from said point (1 1) which is a function of the value of the diameter (d) of said well (50).
7. Dispositif selon la revendication 6, caractérisé par le fait qu'il comporte des moyens (52) pour commander les moyens commandables (51) pour maintenir les deux dites bobines (21, 22) de façon que la distance (h) séparant chaque bobine (21, 22) du dit point (11) soit sensiblement égale aux neuf dixièmes de la valeur du diamètre (d) dudit puits (50).7. Device according to claim 6, characterized in that it comprises means (52) for controlling the controllable means (51) for holding the two said coils (21, 22) so that the distance (h) separating each coil (21, 22) of said point (11) is substantially equal to nine tenths of the value of the diameter (d) of said well (50).
8. Dispositif selon l'une des revendications 5 à 7, caractérisé par le fait que les axes (25, 26) des bobines sont sensiblement parallèles entre eux et perpendiculaires à ladite direction (12).8. Device according to one of claims 5 to 7, characterized in that the axes (25, 26) of the coils are substantially parallel to each other and perpendicular to said direction (12).
9. Dispositif selon l'une des revendications 4 à 8, caractérisé par le fait que les moyens ( 10) pour effectuer, sensiblement en un point (11) dudit milieu rocheux, une excitation suivant une direction donnée ( 12) sont constitués par des moyens d'injection (13) d'un fluide auxiliaire sous pression.9. Device according to one of claims 4 to 8, characterized in that the means (10) for effecting, substantially at a point (11) of said rocky medium, an excitation in a given direction (12) are constituted by means for injecting (13) an auxiliary fluid under pressure.
10. Dispositif selon l'une des revendications 4 à 8, caractérisé par le fait que les moyens (10) pour effectuer, sensiblement en un point (11) dudit milieu rocheux, une excitation suivant une direction donnée ( 12) sont constitués par des moyens d'émission d'ondes de compression (14).10. Device according to one of claims 4 to 8, characterized in that the means (10) for effecting, substantially at a point (11) of said rocky medium, an excitation in a given direction (12) are constituted by means for transmitting compression waves (14).
11. Dispositif selon l'une des revendications 3 à 10, caractérisé par le fait que les moyens (3) pour déterminer la perméabilité dudit milieu rocheux ( 100) en fonction de la mesure dudit champ magnétique comprennent une unité de traitement programmable (30) comportant au moins une entrée (31, 32) de signaux et des moyens (33, 34) pour appliquer les signaux obtenus à la sortie (35, 36) de ladite bobine (21, 22) à l'entrée (31, 32) de ladite unité de traitement (30).11. Device according to one of claims 3 to 10, characterized in that the means (3) for determining the permeability of said rocky medium (100) as a function of the measurement of said magnetic field comprise a programmable processing unit (30) comprising at least one signal input (31, 32) and means (33, 34) for applying the signals obtained at the output (35, 36) of said coil (21, 22) to the input (31, 32) of said processing unit (30).
12. Dispositif selon la revendication 3, caractérisé par le fait que les moyens (2) pour mesurer le champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux sont constitués par au moins l'un des moyens suivants: magnétomètre, bobine magnétique. 12. Device according to claim 3, characterized in that the means (2) for measuring the magnetic field produced by the relative movement of said interstitial fluid in the rocky medium consist of at least one of the following means: magnetometer, coil magnetic.
13. Dispositif selon l'une des revendications 3 à 12, caractérisé par le fait que, lorsqu'un champ magnétique secondaire règne dans le milieu rocheux, les moyens (2) pour mesurer la valeur du champ magnétique produit par le mouvement relatif dudit fluide interstitiel dans le milieu rocheux comportent des moyens pour mesurer la valeur du champ magnétique secondaire, des moyens pour mesurer la valeur du champ magnétique total et des moyens pour soustraire la valeur du champ magnétique secondaire, de celle du champ magnétique total. 13. Device according to one of claims 3 to 12, characterized in that, when a secondary magnetic field prevails in the rocky environment, the means (2) for measuring the value of the magnetic field produced by the relative movement of said fluid interstitial in the rocky environment include means for measuring the value of the secondary magnetic field, means for measuring the value of the total magnetic field and means for subtracting the value of the secondary magnetic field from that of the total magnetic field.
EP95909840A 1994-02-22 1995-02-17 Method and device for evaluating the permeability of a rock medium Ceased EP0695427A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9401965 1994-02-22
FR9401965A FR2716536B1 (en) 1994-02-22 1994-02-22 Method and device for measuring the permeability of a rock medium.
PCT/FR1995/000188 WO1995022809A1 (en) 1994-02-22 1995-02-17 Method and device for evaluating the permeability of a rock medium

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EP (1) EP0695427A1 (en)
JP (1) JPH07280947A (en)
CN (1) CN1123571A (en)
CA (1) CA2142928A1 (en)
FR (1) FR2716536B1 (en)
NO (1) NO950655L (en)
OA (1) OA10237A (en)
WO (1) WO1995022809A1 (en)

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JPH07280947A (en) 1995-10-27
CN1123571A (en) 1996-05-29
FR2716536B1 (en) 1996-04-26
FR2716536A1 (en) 1995-08-25
NO950655L (en) 1995-08-23
NO950655D0 (en) 1995-02-21
CA2142928A1 (en) 1995-08-23
US5519322A (en) 1996-05-21
OA10237A (en) 1997-10-07
WO1995022809A1 (en) 1995-08-24

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