EP0429078A1 - Method and apparatus for measuring ground permeability - Google Patents

Method and apparatus for measuring ground permeability Download PDF

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Publication number
EP0429078A1
EP0429078A1 EP90122300A EP90122300A EP0429078A1 EP 0429078 A1 EP0429078 A1 EP 0429078A1 EP 90122300 A EP90122300 A EP 90122300A EP 90122300 A EP90122300 A EP 90122300A EP 0429078 A1 EP0429078 A1 EP 0429078A1
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Prior art keywords
borehole
pressure
drilling
flow
head
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EP90122300A
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German (de)
French (fr)
Inventor
Gérard Evers
Jean-Pierre Hamelin
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Soletanche SA
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Soletanche SA
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Priority claimed from FR8606992A external-priority patent/FR2598806B1/en
Application filed by Soletanche SA filed Critical Soletanche SA
Priority to EP90122300A priority Critical patent/EP0429078A1/en
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • E21B49/008—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor

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  • the present invention relates to a method and a device for measuring the permeability of a ground, sufficiently coherent so that one can carry out a drilling therein without supporting its walls.
  • the present invention aims to overcome these drawbacks by providing a method and a device for measuring the permeability of a ground which give results in real time, which are easy to implement, which do not require the extraction of the train. rods at each pass, and which can be automated to a large extent.
  • the subject of the invention is a method for measuring the permeability of a homogeneous section of a site, characterized in that, in a first step, drilling is carried out in said site until the start of said homogeneous section, and in said drilling a flow of liquid is caused by noting, at the head of the drilling, the variation in the flow rate as a function of the pressure, that, in a second step, said drilling is continued until the end of said homogeneous section, and a new flow of liquid is caused in the borehole by again taking note, at the head of the borehole, of the variation in the flow rate as a function of the pressure, and that the permeability of the said two curves thus obtained is deduced slice of land.
  • the drilling head is connected to a data acquisition and control system. pressure or flow, and causing the liquid flows from said system.
  • the flow rate Q S can be measured by any suitable means such as a flow meter placed at the head of the borehole, but it can also be deduced from the variation as a function of time, of the pressure in a pressurized tank connected to the head of the borehole.
  • pressurized reservoir is understood here to mean a sealed reservoir provided with a liquid inlet and partially filled with liquid and partially with a gaseous fluid under pressure. Furthermore, when it is a question of a flow of liquid "from” this reservoir, this may as well correspond to an arrival of liquid in the reservoir, which is the case of pumping with a positive flow rate, that an exit of the liquid towards the drilling, which is the case of the injection with a negative flow.
  • the flow of liquid in the borehole takes place in one direction or the other depending on the pressure at the head of the borehole. It is therefore possible to choose this direction of flow, in particular as a function of the water pressure in the ground.
  • the tests will preferably be carried out by pumping, so as to avoid clogging of the wall of the borehole, which generally occurs during injection, and which leads to underestimating the permeability of the ground.
  • the line obtained during the first step is "subtracted" from the line obtained during the second step, that is to say the line is constructed each point has an ordinate equal to the difference of the corresponding ordinates of the first two lines.
  • the slope of the straight line obtained is then measured and the permeability of the terrain is deduced from said slope, in the simplest case by multiplying this slope by a constant.
  • the present invention also relates to a device for measuring the permeability of a ground, characterized in that it comprises a drilling apparatus comprising a drill string supporting at its end a drilling tool for carrying out a delimiting drilling an annular space between the drill string and the wall of the borehole, a flow or pressure control system, a conduit allowing the annular space to communicate with said system, means for measuring at least the pressure or the flow at the head of the borehole and an electronic computer arranged to receive as input the signals from said measurement means and to deduce the permeability of the ground.
  • a drilling apparatus comprising a drill string supporting at its end a drilling tool for carrying out a delimiting drilling an annular space between the drill string and the wall of the borehole, a flow or pressure control system, a conduit allowing the annular space to communicate with said system, means for measuring at least the pressure or the flow at the head of the borehole and an electronic computer arranged to receive as input the signals from said measurement means and to deduce the permeability of the ground.
  • the method described above can therefore be implemented with this device without it being necessary to remove the drill string, the flow of liquid taking place towards the head of the borehole in the annular space formed between the train of rods and the wall of the borehole.
  • We can therefore proceed step by step, and perform for example a measurement during each addition of rod to the drill string, and therefore without any loss of time.
  • the device may also include an anchoring front tube sealed to the ground and concentric with said drill string, to take up the hydrostatic thrust of the liquid.
  • An inflatable stuffing box can be provided between the drill string and the anchoring pre-tube, this stuffing box being deflated during drilling and inflated during the measurements.
  • a non-return valve is preferably provided at the end of the drill string, so as to be able to inject a drilling liquid from the interior of the drill string during drilling.
  • Said control system may comprise, in a first embodiment, a pressurized tank which may include a vent valve and a drain valve, the latter preferably being at adjustable level.
  • control system comprises a valve controlled by the pressure or the flow rate measured at the drilling head.
  • valve it is then possible to slave the valve either so as to simulate the first embodiment, or so as to obtain any desired variation in flow rate or pressure. It may then be necessary to add to the system a possibly regulated injection pump.
  • the device can also also include a set of measurement of drilling parameters making it possible to determine automatically homogeneous sections of land for each of which a permeability test must be carried out.
  • the device of FIG. 1 comprises a drilling apparatus shown diagrammatically at 1 capable of interning a drill string 2 to carry out a drilling 3 in a terrain 4 of which it is desired to know the permeability at the various points of the drilling.
  • the rod 2 carries at its end a drilling tool 5 with a diameter greater than that of the rod so as to form an annular space 7 between the wall 8 of the borehole and the rod 2.
  • the hydrostatic pressure, which is exerted during of the test, at the head of the borehole, is taken up by a pre-anchoring tube 9 sealed to the ground 4 and concentric to the drill string 2.
  • the drill string 2 crosses the front tube 9 at its rear part by means of a seal 10 constituted for example by a hydraulic cable gland.
  • the rod train 2 forms an internal conduit 11 for the passage of a drilling fluid, and a non-return valve 12 at the end of the drill string makes it possible, during the measurements, to avoid reverse flow.
  • a hole 13 is drilled in the front tube 9 to allow the annular space 7 to be connected to a discharge duct 14 which, during drilling, is connected, via an open valve 15, to a pump 16.
  • the pump 16 makes it possible to create a depression in the front tube 9 making it possible to drill with the deflated cable gland 10.
  • the conduit 14 is also connected via a valve 17 to the lower part of a sealed reservoir 18.
  • the reservoir 18 also includes at its upper part a vent 19 capable of being closed by a valve 20 and , at its lower part, a drain pipe 21 closed by a valve 22.
  • the pipe 21 is adjustable in height so as to adjust the drain level.
  • the reservoir 18 is equipped at its upper part with a visual pressure gauge 23 and with a pressure sensor 24 whose output signal is applied via a line 25 to a computer 26.
  • FIG 3 is similar to Figure 1, but for the sake of simplicity, the drilling apparatus and the drill string have not been shown.
  • an impermeable zone 27 has been shown which may correspond either to the impermeable zone of the fore-tube, or to a zone of ground which is naturally impermeable or impermeable during an earlier phase.
  • the drilling is carried out by successive passes or sections of land, a measurement being carried out between each pass.
  • valve 17 At the start of each pass, the valve 17 being closed, the valves 20 and 22 are opened so as to empty the reservoir 18.
  • the duct 21 is adjusted so that after the emptying the reservoir contains an amount of air such that, during the test which will follow, the pressure varies significantly in the time desired for the duration of the test.
  • the drilling rig 1 is stopped as well as the pump 16, the cable gland 10 is inflated, the valve 15 is closed as are the valves 20 and 22, and the valve 17 is open.
  • the pressure in the reservoir 18 is lower than the pressure P o of the water table in the ground 4, the water then begins to flow in the borehole, and from the head of the borehole to the reservoir 18 in which the liquid level rises.
  • FIG. 3 shows the radial drainage which takes place in the terrain 4 between the dimension planes z and z + dz. At this level, the water which filters into the ground penetrates with the speed u z into the borehole at a point where the pressure is equal to P z and the axial flow speed V z .
  • the computer 26 records for each pass, via the pressure sensor 24, the change in pressure P S (n) in the tank 18 as a function of time, and deduces therefrom the curve representing the flow rate Q S (n) as a function of P S (n) .
  • the computer 26 is programmed so as to establish the diagram of FIG. 4 representing the variation of Arctg as a function of W S with the definitions given above of Q S and W S.
  • the line corresponding to the first pass has the slope w (1) l (1) and that, for step n, the line 30 obtained by difference between the ordinates of the line constructed in step n and the ordinates of the straight line constructed in step n-1 have slope w (n) l (n) .
  • the computer 26 then deduces the permeability of the slice corresponding to step n of the following formula:
  • the invention therefore makes it possible to determine step by step the permeability of the ground crossed by the borehole 7.
  • the conduit 14 is connected to the pump 16 via a flow meter 40, a pressure sensor 41, and a slave valve 42.
  • the data captured by the flow meter 40 and the sensor pressure 41 are transmitted to the computer 26 which in turn controls the valve 42.
  • FIG. 2 also shows an assembly 43 for measuring the drilling parameters which, during the drilling phases, transmit to the computer 26 the data such as the speed of rotation of the train of the rod, the reaction exerted on the latter and forward speed.
  • the computer 26 can be programmed to automatically determine the homogeneous slices of land and therefore the locations where a new permeability measurement must be made.
  • the computer 26 can for example control the valve 42 so as to simulate the test carried out with the device in FIG. 1.
  • FIGS. 5b and 5c show characteristic curves of a laminar flow with clogging at high pressure and unclogging respectively.
  • the curve of FIG. 5d is obtained in a terrain exhibiting clogging characteristics at low pressure while FIG. 5e is obtained with a terrain exhibiting clogging characteristics at low pressure and also at high pressure.
  • FIG. 5f represents a clogging at low pressure and an unclogging at high pressure.
  • Figure 5g is characteristic of a turbulent flow and finally Figure 5h represents a progressive unclogging.

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

The measuring system uses a borehole drilled in the ground up to the base of the selected soil section, within which a given liq. is filled. The loss of liq. is a function of the pressure being measured. The process is repeated with a borehole depth which corresp. to the top of the same soil section and the two characteristic curves obtained are used to evaluate the ground permeability. Pref., the loss of liq. is determined by using a pressurised reservoir coupled to the head of the borehole. @(13pp Dwg.No.1/5)@

Description

Procédé pour la mesure de la perméabilité d'un terrainMethod for measuring the permeability of a ground

La présente invention concerne un procédé et un dispositif pour la mesure de la perméabilité d'un terrain, suffisamment cohérent pour que l'on puisse y effectuer un forage sans soutènement de ses parois.The present invention relates to a method and a device for measuring the permeability of a ground, sufficiently coherent so that one can carry out a drilling therein without supporting its walls.

On rappellera tout d'abord que la perméabilité d'un terrain est définie à partir de la loi de Darcy, comme le rapport au gradient de pression, du débit traversant une tranche de ce terrain, de surface et d'épaisseur unité.It will be recalled first of all that the permeability of a ground is defined starting from the law of Darcy, like the relation to the gradient of pressure, of the flow crossing a section of this ground, of surface and thickness unit.

La connaissance de la perméabilité d'un terrain est essentielle pour la réalisation de nombreux ouvrages de génie civil, et notamment à chaque fois que l'on souhaite imperméabiliser ce terrain à l'aide d'injections.Knowledge of the permeability of a site is essential for the realization of many civil engineering works, and in particular each time that one wishes to waterproof this site using injections.

Ceci est le cas par exemple lorsque l'on souhaite réaliser un voile étanche sous l'assise d'un barrage.This is the case for example when it is desired to produce a waterproof veil under the seat of a dam.

On rencontre également ce problème lors du creusement à sec de tunnels. Dans ce dernier cas, on procède souvent à des injections en avant du front de taille pour étanchéifier la paroi de ce dernier.This problem is also encountered during the dry digging of tunnels. In the latter case, injections are often carried out in front of the face to seal the wall of the latter.

Jusqu'à présent, pour connaître la perméabilité d'une tranche de terrain située à une distance comprise entre L et L + l de la surface, on procède à un forage jusqu 'à la distance L + l, on retire partiellement ou complètement le train de tiges, on équipe le forage avec des tiges d'injection d'eau munies d'un obturateur que l'on positionne à la distance L, on injecte de l'eau sous une pression donnée en mesurant le débit correspondant, on extrait l'équipement d'essai, on remet en place le train de tiges de forage, et on procède au forage de la passe suivante. Un tel procédé est décrit dans le document US-A-3771360.Up to now, to find out the permeability of a section of land located at a distance between L and L + l from the surface, we drill to the distance L + l, we partially or completely remove the drill string, we equip the drilling with water injection rods fitted with a shutter that is positioned at distance L, we inject water under a given pressure by measuring the corresponding flow rate, we extract test equipment, replace the drill string, and drill the next pass. Such a method is described in document US-A-3771360.

Une telle procédure ne peut pas être automatisée et exige beaucoup de temps pendant lequel l'outil de production, par exemple le tunnelier, est a' l'arrêt. De ce fait, on limite souvent le nombre des essais un strict minimun, ce qui conduit à une connaissance imparfaite de la perméabilité avec les risques ou inconvénients que cela comporte.Such a procedure cannot be automated and requires a lot of time during which the production tool, for example the tunneling machine, is stopped. As a result, the number of trials is often limited a strict minimum, which leads to an imperfect knowledge of permeability with the risks or disadvantages that this involves.

La présente invention vise à pallier ces inconvénients en fournissant un procédé et un dispositif pour la mesure de la perméabilité d'un terrain qui donnent des résultats en temps réel, qui soient faciles à mettre en oeuvre, qui ne nécessitent pas l'extraction du train de tiges à chaque passe, et qui puissent être automatisés dans une large mesure.The present invention aims to overcome these drawbacks by providing a method and a device for measuring the permeability of a ground which give results in real time, which are easy to implement, which do not require the extraction of the train. rods at each pass, and which can be automated to a large extent.

A cet effet, l'invention a pour objet un procédé pour la mesure de la perméabilité d'une tranche homogène d'un terrain, caractérisé par le fait que, dans une première étape, on effectue un forage dans ledit terrain jusqu'au début de ladite tranche homogène, et on provoque dans ledit forage un écoulement de liquide en relevant, en tête du forage, la variation du débit en fonction de la pression, que, dans une deuxième étape, on poursuit ledit forage jusqu'à la fin de ladite tranche homogène, et on provoque un nouvel écoulement de liquide dans le forage en relevant de nouveau, en tête du forage, la variation du débit en fonction de la pression, et que l'on déduit des deux courbes ainsi obtenues la perméabilité de ladite tranche de terrain.To this end, the subject of the invention is a method for measuring the permeability of a homogeneous section of a site, characterized in that, in a first step, drilling is carried out in said site until the start of said homogeneous section, and in said drilling a flow of liquid is caused by noting, at the head of the drilling, the variation in the flow rate as a function of the pressure, that, in a second step, said drilling is continued until the end of said homogeneous section, and a new flow of liquid is caused in the borehole by again taking note, at the head of the borehole, of the variation in the flow rate as a function of the pressure, and that the permeability of the said two curves thus obtained is deduced slice of land.

De préférence, après avoir effectué ledit forage jusqu'au début de la tranche homogène, et après avoir poursuivi ledit forage jusqu'à la fin de la tranche homogène, on relie la tête du forage à un système d'acquisition de données et de contrôle de la pression ou du débit, et on provoque les écoulements de liquide à partir dudit système.Preferably, after having carried out said drilling until the start of the homogeneous section, and after having continued said drilling until the end of the homogeneous section, the drilling head is connected to a data acquisition and control system. pressure or flow, and causing the liquid flows from said system.

On verra ci-après que la courbe du débit QS en tête du forage en fonction de la pression PS en tête de forage caractérise la perméabilité du terrain traversé par le forage.It will be seen below that the curve of the flow rate Q S at the head of the borehole as a function of the pressure P S at the head of the borehole characterizes the permeability of the ground crossed by the borehole.

Le débit QS peut être mesuré par tout moyen convenable tel qu'un débimètre placé en tête du forage, mais on peut aussi le déduire de la variation en fonction du temps, de la pression dans un réservoir pressurisé relié à la tête du forage.The flow rate Q S can be measured by any suitable means such as a flow meter placed at the head of the borehole, but it can also be deduced from the variation as a function of time, of the pressure in a pressurized tank connected to the head of the borehole.

On entend ici par réservoir pressurisé, un réservoir étanche muni d'une arrivée de liquide et rempli partiellement de liquide et partiellement d'un fluide gazeux sous pression. Par ailleurs, lorsqu'il est question d'un écoulement de liquide "à partir" de ce réservoir, ceci peut aussi bien correspondre à une arrivée de liquide dans le réservoir, ce qui est le cas d'un pompage avec un débit positif, qu'une sortie du liquide vers le forage, ce qui est le cas de l'injection avec un débit négatif.The term “pressurized reservoir” is understood here to mean a sealed reservoir provided with a liquid inlet and partially filled with liquid and partially with a gaseous fluid under pressure. Furthermore, when it is a question of a flow of liquid "from" this reservoir, this may as well correspond to an arrival of liquid in the reservoir, which is the case of pumping with a positive flow rate, that an exit of the liquid towards the drilling, which is the case of the injection with a negative flow.

On comprend que, suivant la pression qui règne dans le réservoir, l'écoulement s'effectuera dans un sens ou dans l'autre de manière à tendre à équilibrer la pression dans le réservoir et dans le forage.It is understood that, depending on the pressure prevailing in the reservoir, the flow will take place in one direction or the other so as to tend to balance the pressure in the reservoir and in the borehole.

Par conséquent, dans le cas de l'utilisation d'un tel réservoir, on conçoit que, connaissant la quantité de gaz contenue dans le réservoir et sa pression, il est facile d'en déduire son volume et ainsi, le volume du liquide contenu dans ce même réservoir. Le débit volumique du liquide dans le réservoir n'est autre que la variation en fonction du temps de ce volume, sous réserve de l'hypothèse de l'incompressibilité du liquide qui peut, bien entendu, être admise dans le cas présent.Consequently, in the case of the use of such a tank, it is understood that, knowing the quantity of gas contained in the tank and its pressure, it is easy to deduce its volume and thus, the volume of the liquid contained. in this same tank. The volume flow rate of the liquid in the reservoir is none other than the variation as a function of time of this volume, subject to the assumption of the incompressibility of the liquid which can, of course, be accepted in the present case.

On peut donc ainsi mesurer la perméabilité du terrain en relevant uniquement la pression dans le réservoir pressurisé en fonction du temps.We can thus measure the permeability of the ground by only reading the pressure in the pressurized tank as a function of time.

L'écoulement du liquide dans le forage s'effectue dans un sens ou dans l'autre en fonction de la pression en tête du forage. Il est donc possible de choisir ce sens d'écoulement, en particulier en fonction de la pression d'eau dans le terrain. Toutefois, les essais s'effectueront de préférence en pompage, de manière à éviter le colmatage de la paroi du forage qui se produit généralement en injection, et qui conduit à sous-estimer la perméabilité du terrain.The flow of liquid in the borehole takes place in one direction or the other depending on the pressure at the head of the borehole. It is therefore possible to choose this direction of flow, in particular as a function of the water pressure in the ground. However, the tests will preferably be carried out by pumping, so as to avoid clogging of the wall of the borehole, which generally occurs during injection, and which leads to underestimating the permeability of the ground.

Dans le cas du pompage, c'est-à-dire lorsque l'on provoque l'écoulement du liquide du fond du forage vers la tête du forage, on peut avantageusenent représenter la variation du débit en fonction de la pression en tracant la droite obtenue en portant les couples (QS,PS) dans le plan

Figure imgb0001
Po étant la pression de la nappe d'eau au niveau où est effectuée la mesure, dw étant la densité de l'eau, s étant la section libre en tête du forage, et S la section libre du forage.In the case of pumping, that is to say when the liquid from the bottom of the borehole is caused to flow towards the head of the borehole, it is advantageous to represent the variation of the flow rate as a function of the pressure by plotting the line obtained by carrying the couples (Q S , P S ) in the plane
Figure imgb0001
 P o being the pressure of the water table at the level where the measurement is made, d w being the density of the water, s being the free section at the head of the borehole, and S the free section of the borehole.

Lorsqu'au contraire on provoque l'écoulement du liquide de la tête du forage vers le fond du forage, on représente avantageusement la variation du débit en fonction de la pression en tracant la droite obtenue en portant les couples

Figure imgb0002
When, on the contrary, the liquid from the drilling head is caused to flow towards the bottom of the drilling, the variation of the flow rate as a function of the pressure is advantageously represented by plotting the straight line obtained by carrying the torques
Figure imgb0002

En toute rigueur, la courbe ainsi obtenue n'est une droite que sous les hypothèses suivantes, généralement admises en matière d'interprétation d'essais d'eau :
- L'eau est supposée incompressible et de densité dw.
- L'écoulement autour du forage entraîne uniquement un drainage radial, c'est-à-dire perpendiculaire à l'axe du forage, et vérifie la loi de Darcy. On remarquera que le fait de supposer le drainage radial revient à négliger les cheminements d'eau qui ont lieu à partir du fond du forage, ce qui conduit, dans le cas d'un pompage, à sous-estimer très légèrement le débit.
- Les rayons d'actions R du drainage sont suffisamment faibles par rapport à la profondeur à laquelle est effectuée la mesure pour que la pression de l'eau à la distance R du forage soit indépendante de la direction dans laquelle on la mesure.
- Les lignes de courant dans le forage sont toutes parallèles à l'axe du forage et la vitesse de l'écoulement dans chaque section est uniforme et égale à V z. La pression correspondante Pz est également uniforme dans toute la section du forage. Cette hypothèse conduit toujours dans le cas du pompage, à surestimer les débits. En particulier, l'aspect laminaire de l'écoulement dans le forage est négligé, le liquide étant supposé non visqueux.
- L'écoulement dans le terrain et dans le forage est supposé quasi permanent. Autrement dit, aucune des grandeurs physiques concernées ne dépend du temps.Strictly speaking, the curve thus obtained is a straight line only under the following hypotheses, generally accepted in terms of interpretation of water tests:
- Water is assumed to be incompressible and of density d w .
- The flow around the borehole only causes radial drainage, that is to say perpendicular to the axis of the borehole, and verifies Darcy's law. Note that assuming radial drainage is equivalent to neglecting the water paths that take place at from the bottom of the borehole, which leads, in the case of pumping, to slightly underestimate the flow rate.
- The radii of action R of the drainage are sufficiently small compared to the depth at which the measurement is made so that the water pressure at the distance R of the borehole is independent of the direction in which it is measured.
- The current lines in the borehole are all parallel to the axis of the borehole and the speed of flow in each section is uniform and equal to V z . The corresponding pressure P z is also uniform throughout the drilling section. This assumption always leads in the case of pumping, to overestimate the flow rates. In particular, the laminar aspect of the flow in the borehole is neglected, the liquid being assumed to be non-viscous.
- The flow in the ground and in the drilling is assumed to be almost permanent. In other words, none of the physical quantities concerned depends on time.

De toutes manières, un calibrage des appareils utilisés permet de corriger les résultats obtenus lorsque les hypothèses ci-dessus ne sont pas admissibles.In any case, a calibration of the devices used makes it possible to correct the results obtained when the above hypotheses are not admissible.

De même, ce qui précède suppose un écoulement dans le forage sans perte de charge. Un étalonnage est en outre également nécessaire dans le cas d'un forage incliné ou vertical.Likewise, the above assumes a flow in the borehole without pressure drop. In addition, calibration is also necessary in the case of inclined or vertical drilling.

Dans le cas où les hypothèses ci-dessus sont satisfaites, on "soustrait" la droite obtenue lors de la première étape de la droite obtenue lors de la deuxième étape, c'est-à-dire que l'on construit la droite dont chaque point a une ordonnée égale à la différence des ordonnées correspondantes des deux premières droites.If the above hypotheses are satisfied, the line obtained during the first step is "subtracted" from the line obtained during the second step, that is to say the line is constructed each point has an ordinate equal to the difference of the corresponding ordinates of the first two lines.

On mesure alors la pente de la droite obtenue et on déduit la perméabilité du terrain de ladite pente, dans le cas le plus simple en multipliant cette pente par une constante.The slope of the straight line obtained is then measured and the permeability of the terrain is deduced from said slope, in the simplest case by multiplying this slope by a constant.

Si l'on néglige la viscosité du liquide, cette constante est, sous réserve d'étalonnage, égale à :

Figure imgb0003
où R est le rayen d'action de l'écoulement dans le terrain, ro est le rayon du forage, g est l'attraction de la pesafnteur, et l est l'épaisseur de la tranche de terrain dans laquelle on mesure la perméabilité.If the viscosity of the liquid is neglected, this constant is, subject to calibration, equal to:
Figure imgb0003
 where R is the radius of action of the flow in the ground, r o is the radius of the borehole, g is the attraction of the gravity, and l is the thickness of the slice of ground in which the permeability is measured .

En fait, ce qui précède peut s'écrire :
ω l = p
où p est la pente de la droite, et

Figure imgb0004
k étant la perméabilité cherchée.In fact, the above can be written:
ω l = p
where p is the slope of the line, and
Figure imgb0004
 k being the permeability sought.

Dans le cas où la viscosité du liquide ne pourra être négligée, on procèdera de façon similaire en remplaçant ω par :

Figure imgb0005
où y est la viscosité cinématique du fluide.If the viscosity of the liquid cannot be neglected, we will proceed in a similar way, replacing ω by:
Figure imgb0005
 where y is the kinematic viscosity of the fluid.

La présente invention a également pour objet un dispositif pour la mesure de la perméabilité d'un terrain, caractérisé par le fait qu'il comprend un appareil de forage comportant un train de tiges supportant à son extrémité un outil de forage pour réaliser un forage délimitant un espace annulaire entre le train de tiges et la paroi du forage, un système de contrôle de débit ou de pression, un conduit permettant de mettre en communication l'espace annulaire et ledit système, des moyens pour mesurer au moins la pression ou le débit en tête du forage et un calculateur électronique agencé pour recevoir en entrée les signaux issus desdits moyens de mesure et pour en déduire la perméabilité du terrain.The present invention also relates to a device for measuring the permeability of a ground, characterized in that it comprises a drilling apparatus comprising a drill string supporting at its end a drilling tool for carrying out a delimiting drilling an annular space between the drill string and the wall of the borehole, a flow or pressure control system, a conduit allowing the annular space to communicate with said system, means for measuring at least the pressure or the flow at the head of the borehole and an electronic computer arranged to receive as input the signals from said measurement means and to deduce the permeability of the ground.

Le procédé décrit ci-dessus peut donc être mis en oeuvre avec ce dispositif sans qu'il soit nécessaire de retirer le train de tiges, l'écoulement de liquide s'effectuant vers la tête du forage dans l'espace annulaire formé entre le train de tiges et la paroi du forage. On peut donc procéder pas à pas, et effectuer par exemple une mesure lors de chaque ajout de tige au train de tiges, et donc sans aucune perte de temps.The method described above can therefore be implemented with this device without it being necessary to remove the drill string, the flow of liquid taking place towards the head of the borehole in the annular space formed between the train of rods and the wall of the borehole. We can therefore proceed step by step, and perform for example a measurement during each addition of rod to the drill string, and therefore without any loss of time.

Le dispositif peut en outre comprendre un avant-tube d'ancrage scellé au terrain et concentrique audit train de tiges, pour reprendre la poussée hydrostatique du liquide.The device may also include an anchoring front tube sealed to the ground and concentric with said drill string, to take up the hydrostatic thrust of the liquid.

Un presse-étoupe gonflable peut être prévu entre le train de tiges et l'avant-tube d'ancrage, ce presse-étoupe étant dégonflé pendant le forage et gonflé pendant les mesures.An inflatable stuffing box can be provided between the drill string and the anchoring pre-tube, this stuffing box being deflated during drilling and inflated during the measurements.

Un clapet anti-retour est de préférence prévu à l'extrémité du train de tiges, de manière à pouvoir injecter un liquide de forage par l'intérieur du train de tiges pendant le forage.A non-return valve is preferably provided at the end of the drill string, so as to be able to inject a drilling liquid from the interior of the drill string during drilling.

Ledit système de contrôle peut comprendre, dans un premier mode de réalisation un réservoir pressurisé pouvant comporter une vanne de mise à l'air libre et une vanne de vidange, cette dernière étant de préférence à niveau réglable.Said control system may comprise, in a first embodiment, a pressurized tank which may include a vent valve and a drain valve, the latter preferably being at adjustable level.

Dans un second mode de réalisation, le système de contrôle comprend une vanne asservie sur la pression ou le débit mesuré en tête de forage.In a second embodiment, the control system comprises a valve controlled by the pressure or the flow rate measured at the drilling head.

Il est alors possible d'asservir la vanne soit de façon à simuler le premier mode de réalisation, soit de façon à obtenir toute variation souhaitée du débit ou de la pression. On peut alors être amené à ajouter au systeme une pompe d'injection éventuellement régulée.It is then possible to slave the valve either so as to simulate the first embodiment, or so as to obtain any desired variation in flow rate or pressure. It may then be necessary to add to the system a possibly regulated injection pump.

Le dispositif peut en outre également comprendre un ensemble de mesure des paramètres de forage permettant de déterminer automatiquement les tranches homogènes de terrain pour chacune desquelles un essai de perméabilité doit être réalisé.The device can also also include a set of measurement of drilling parameters making it possible to determine automatically homogeneous sections of land for each of which a permeability test must be carried out.

On décrira maintenant un mode de réalisation particulier de l'invention en référence aux dessins annexés dans lesquels :

  • - la figure 1 est une représentation schématique d'un dispositif selon un premier mode de réalisation de l'invention,
  • - la figure 2 est une représentation schématique d'un dispositif selon un deuxième mode de réalisation de l'invention.
  • - la figure 3 est un diagramme d'un forage effectué conformément à l'invention,
  • - la figure 4 représente un tracé de courbes conforme à un procédé selon l'invention, et
  • - les figures 5a à 5h sont des courbes de pression en fonction du débit obtenues avec le dispositif selon le deuxième mode de réalisation, pour différents types d'écoulements.
A particular embodiment of the invention will now be described with reference to the accompanying drawings in which:
  • FIG. 1 is a schematic representation of a device according to a first embodiment of the invention,
  • - Figure 2 is a schematic representation of a device according to a second embodiment of the invention.
  • FIG. 3 is a diagram of a borehole carried out in accordance with the invention,
  • FIG. 4 represents a plot of curves in accordance with a method according to the invention, and
  • - Figures 5a to 5h are pressure curves as a function of the flow rate obtained with the device according to the second embodiment, for different types of flows.

Le dispositif de la figure 1 comporte un appareil de forage schématisé en 1 susceptible d'entralner un train de tiges 2 pour réaliser un forage 3 dans un terrain 4 dont on souhaite connaitre la perméabilité aux différents points du forage.The device of FIG. 1 comprises a drilling apparatus shown diagrammatically at 1 capable of interning a drill string 2 to carry out a drilling 3 in a terrain 4 of which it is desired to know the permeability at the various points of the drilling.

La tige 2 porte à son extrémité un outil de forage 5 d'un diamètre supérieur à celui de la tige de manière à former un espace annulaire 7 entre la paroi 8 du forage et la tige 2. La pression hydrostatique, qui s'exerce lors de l'essai, en tête de forage, est reprise par un avant-tube d'ancrage 9 scellé au terrain 4 et concentrique au train de tiges 2.The rod 2 carries at its end a drilling tool 5 with a diameter greater than that of the rod so as to form an annular space 7 between the wall 8 of the borehole and the rod 2. The hydrostatic pressure, which is exerted during of the test, at the head of the borehole, is taken up by a pre-anchoring tube 9 sealed to the ground 4 and concentric to the drill string 2.

Le train de tiges 2 traverse l'avant-tube 9 à sa partie postérieure par l'intermédiaire d'un joint 10 constitué par exemple par un presse-étoupe hydraulique.The drill string 2 crosses the front tube 9 at its rear part by means of a seal 10 constituted for example by a hydraulic cable gland.

Le train de tige 2 forme un conduit intérieur 11 pour le passage d'un fluide de forage, et un clapet anti-retour 12 à l'extrémité du train de tiges permet, lors des mesures, d'éviter un écoulement inverse.The rod train 2 forms an internal conduit 11 for the passage of a drilling fluid, and a non-return valve 12 at the end of the drill string makes it possible, during the measurements, to avoid reverse flow.

Un trou 13 est percé dans l'avant-tube 9 pour permettre de relier l'espace annulaire 7 à un conduit d'évacuation 14 qui, pendant le forage, est relié, par l'intermédiaire d'une vanne ouverte 15, à une pompe 16. La pompe 16 permet de créer une dépression dans l'avant-tube 9 permettant de forer avec le presse-étoupe 10 dégonflé.A hole 13 is drilled in the front tube 9 to allow the annular space 7 to be connected to a discharge duct 14 which, during drilling, is connected, via an open valve 15, to a pump 16. The pump 16 makes it possible to create a depression in the front tube 9 making it possible to drill with the deflated cable gland 10.

Le conduit 14 est par ailleurs relié par l'intermédiaire d'une vanne 17, à la partie inférieure d'un réservoir étanche 18. Le réservoir 18 comprend également à sa partie supérieure un évent 19 susceptible d'être fermé par une vanne 20 et, à sa partie inférieure, un conduit de vidange 21 fermé par une vanne 22. Le conduit 21 est réglable en hauteur de manière à régler le niveau de vidange.The conduit 14 is also connected via a valve 17 to the lower part of a sealed reservoir 18. The reservoir 18 also includes at its upper part a vent 19 capable of being closed by a valve 20 and , at its lower part, a drain pipe 21 closed by a valve 22. The pipe 21 is adjustable in height so as to adjust the drain level.

Le réservoir 18 est équipé à sa partie supérieure d'un manomètre visuel 23 et d'un capteur de pression 24 dont le signal de sortie est appliqué par l'intermédiaire d'une ligne 25 à un calculateur 26.The reservoir 18 is equipped at its upper part with a visual pressure gauge 23 and with a pressure sensor 24 whose output signal is applied via a line 25 to a computer 26.

La figure 3 est similaire à la figure 1, mais par souci de simplification, on n'a pas représenté l'appareil de forage et le train de tiges. Par contre, on a montré une zone imperméable 27 qui peut correspondre soit à la zone imperméable de l'avant-tube, soit à une zone de terrain imperméable naturellement ou imperméabilisée lors d'une phase antérieure.Figure 3 is similar to Figure 1, but for the sake of simplicity, the drilling apparatus and the drill string have not been shown. On the other hand, an impermeable zone 27 has been shown which may correspond either to the impermeable zone of the fore-tube, or to a zone of ground which is naturally impermeable or impermeable during an earlier phase.

Le dispositif qui vient d'être décrit est utilisé de la manière suivante.The device which has just been described is used in the following manner.

Le forage s'effectue par passes ou tranches de terrain successives, une mesure étant effectué entre chaque passe.The drilling is carried out by successive passes or sections of land, a measurement being carried out between each pass.

Au début de chaque passe, la vanne 17 étant fermée, on ouvre les vannes 20 et 22 de manière à vidanger le réservoir 18. Le conduit 21 est réglé de manière qu'après la vidange le réservoir contienne une quantité d'air telle que, au cours de l'essai qui suivra, la pression varie de manière significative dans le temps souhaité pour la durée de l'essai.At the start of each pass, the valve 17 being closed, the valves 20 and 22 are opened so as to empty the reservoir 18. The duct 21 is adjusted so that after the emptying the reservoir contains an amount of air such that, during the test which will follow, the pressure varies significantly in the time desired for the duration of the test.

A la fin de chaque passe, par exemple de la passe n à la figure 3, l'appareil de forage 1 est arrêté ainsi que la pompe 16, le presse-étoupe 10 est gonflé, la vanne 15 est fermée de même que les vannes 20 et 22, et la vanne 17 est ouverte.At the end of each pass, for example from pass n in FIG. 3, the drilling rig 1 is stopped as well as the pump 16, the cable gland 10 is inflated, the valve 15 is closed as are the valves 20 and 22, and the valve 17 is open.

Si la pression dans le réservoir 18 est inférieure à la pression Po de la nappe d'eau dans le terrain 4, l'eau commence alors à s'écouler dans le forage, et de la tête du forage vers le réservoir 18 dans lequel le niveau de liquide monte.If the pressure in the reservoir 18 is lower than the pressure P o of the water table in the ground 4, the water then begins to flow in the borehole, and from the head of the borehole to the reservoir 18 in which the liquid level rises.

La figure 3 montre le drainage radial qui s'effectue dans le terrain 4 entre les plans de cotes z et z+dz. A ce niveau, l'eau qui filtre dans le terrain pénètre avec la vitesse uz dans le forage en un point où la pression est égale à Pz et la vitesse d'écoulement axiale Vz.FIG. 3 shows the radial drainage which takes place in the terrain 4 between the dimension planes z and z + dz. At this level, the water which filters into the ground penetrates with the speed u z into the borehole at a point where the pressure is equal to P z and the axial flow speed V z .

Le calculateur 26 enregistre pour chaque passe, par l'intermédiaire du capteur de pression 24, l'évolution de la pression PS(n) dans le réservoir 18 en fonction du temps, et en déduit de façon évidente la courbe representant le débit QS (n) en fonction de PS (n).The computer 26 records for each pass, via the pressure sensor 24, the change in pressure P S (n) in the tank 18 as a function of time, and deduces therefrom the curve representing the flow rate Q S (n) as a function of P S (n) .

Le calculateur 26 est programmé de manière à établir le diagramme de la figure 4 représentant la variation de Arctg

Figure imgb0006
en fonction de WS avec les définitions données ci-dessus de QS et WS.The computer 26 is programmed so as to establish the diagram of FIG. 4 representing the variation of Arctg
Figure imgb0006
 as a function of W S with the definitions given above of Q S and W S.

On peut alors montrer que, sous réserve des hypothèses énoncées ci-dessus, et notamment de la non viscosité de l'eau, ces courbes sont des droites passant par l'origine des axes.We can then show that, subject to the hypotheses stated above, and in particular the non-viscosity of water, these curves are straight lines passing through the origin of the axes.

On peut également montrer que :

Figure imgb0007
où l est la longueur de la passe n, où les exposant (n) indiquent que les quantités se rapportent à la passe n, et où les exposants (n-1) indiquent que les quantités se rapportent à la passe n-1.We can also show that:
Figure imgb0007
 where l is the length of the pass n, where the exponents (n) indicate that the quantities relate to the pass n, and where the exponents (n-1) indicate that the quantities relate to the pass n-1.

On peut également montrer que pour la première passe :

Figure imgb0008
We can also show that for the first pass:
Figure imgb0008

On en déduit que la droite correspondante à la première passe a pour pente w(1)l(1) et que, pour l'étape n, la droite 30 obtenue par différence entre les ordonnées de la droite construite à l'étape n et les ordonnées de la droite construites à l'étape n-1 a pour pente w(n)l(n).We deduce that the line corresponding to the first pass has the slope w (1) l (1) and that, for step n, the line 30 obtained by difference between the ordinates of the line constructed in step n and the ordinates of the straight line constructed in step n-1 have slope w (n) l (n) .

Le calculateur 26 déduit alors la perméabilité de la tranche correspondante à l'étape n de la formule suivante :

Figure imgb0009
The computer 26 then deduces the permeability of the slice corresponding to step n of the following formula:
Figure imgb0009

L'invention permet par conséquent de déterminer pas à pas la perméabilité du terrain traversé par le forage 7.The invention therefore makes it possible to determine step by step the permeability of the ground crossed by the borehole 7.

Si l'on se réfère maintenant à la figure 2 on voit que les mêmes éléments que ceux de la figure 1 ont reçu les mêmes références.If we now refer to Figure 2 we see that the same elements as those of Figure 1 have been given the same references.

Dans ce cas toutefois le conduit 14 est relié à la pompe 16 par l'intermédiaire d'un débitmètre 40, d'un capteur de pression 41, et d'une vanne asservie 42. Les données captées par le débitmètre 40 et le capteur de pression 41 sont transmises au calculateur 26 qui à son tour commande la vanne 42.In this case, however, the conduit 14 is connected to the pump 16 via a flow meter 40, a pressure sensor 41, and a slave valve 42. The data captured by the flow meter 40 and the sensor pressure 41 are transmitted to the computer 26 which in turn controls the valve 42.

On a en outre représenté sur la figure 2 un ensemble 43 de mesure des paramètres de forage qui, pendant les phases de forage, transmettent au calculateur 26 les données telles que la vitesse de rotation du train du tige, la réaction exercée sur ce dernier et la vitesse d'avancement.FIG. 2 also shows an assembly 43 for measuring the drilling parameters which, during the drilling phases, transmit to the computer 26 the data such as the speed of rotation of the train of the rod, the reaction exerted on the latter and forward speed.

Le calculateur 26 peut être programmé pour déterminer automatiquement les tranches homogènes de terrain et par conséquent les emplacements où une nouvelle mesure de perméabilité doit être effectuée.The computer 26 can be programmed to automatically determine the homogeneous slices of land and therefore the locations where a new permeability measurement must be made.

Le calculateur 26 peut par exemple commander la vanne 42 de manière à simuler l'essai réalisé avec le dispositif de la figure 1.The computer 26 can for example control the valve 42 so as to simulate the test carried out with the device in FIG. 1.

Il est également possible, grâce à la vanne asservie 42, d'effectuer des essais complets incluant des paliers de débit ou de pression. L'asservissement est alors destiné à faire varier dans un cas le débit pour obtenir une pression donnée, ou la pression pour obtenir un débit donné. Les paliers de débit ou de pression permettent donc d'obtenir des valeurs de QS et PS stabilisées et d'éliminer ainsi les phénomènes transitoires de l'écoulement.It is also possible, thanks to the slave valve 42, to carry out complete tests including flow or pressure levels. The control is then intended to vary in a case the flow rate to obtain a given pressure, or the pressure to obtain a given flow rate. The flow or pressure stages therefore make it possible to obtain stabilized Q S and P S values and thus to eliminate transient flow phenomena.

Quel que soit le programme utilisé, les valeurs de QS et PS sont exploitées comme décrit précédemment en référence aux figures 3 et 4.Whatever the program used, the values of Q S and P S are used as described above with reference to FIGS. 3 and 4.

Il est également possible de programmer l'asservissement de manière à former un cycle, ce qui permet, outre la détermination de la perméabilité du terrain, l'analyse des phénomènes de colmatage et décolmatage du terrain ou de la nature laminaire ou turbulente de l'écoulement.It is also possible to program the servo so as to form a cycle, which allows, in addition to determining the permeability of the terrain, the analysis of clogging and unclogging phenomena of the terrain or of the laminar or turbulent nature of the flow.

La figure 5a représente la courbe PS = f (QS) obtenue pour un écoulement laminaire sans colmatage.FIG. 5a represents the curve P S = f (Q S ) obtained for a laminar flow without clogging.

Au contraire, les figures 5b et 5c montrent des courbes caractéristiques d'un écoulement laminaire avec respectivement colmatage à haute pression et décolmatage.On the contrary, FIGS. 5b and 5c show characteristic curves of a laminar flow with clogging at high pressure and unclogging respectively.

La courbe de la figure 5d est obtenue dans un terrain présentant des caractéristiques de colmatage à basse pression tandis que la figure 5e est obtenue avec un terrain présentant des caractéristiques de colmatage à basse pression et également à haute pression.The curve of FIG. 5d is obtained in a terrain exhibiting clogging characteristics at low pressure while FIG. 5e is obtained with a terrain exhibiting clogging characteristics at low pressure and also at high pressure.

La figure 5f représente un colmatage à basse pression et un décolmatage à haute pression.FIG. 5f represents a clogging at low pressure and an unclogging at high pressure.

La figure 5g est caractéristique d'un écoulement turbulent et enfin la figure 5h représente un décolmatage progressif.Figure 5g is characteristic of a turbulent flow and finally Figure 5h represents a progressive unclogging.

Diverses variantes et modifications peuvent bien entendu être apportées à la description qui précède sans sortir pour autant du cadre ni de l'esprit de l'invention.Various variants and modifications can of course be made to the above description without departing from the scope or the spirit of the invention.

Claims (9)

1. Procédé pour la mesure de la perméabilité d'une tranche homogène d'un terrain, caractérisé par le fait que, dans une première étape, on effectue un forage dans ledit terrain jusqu'au début de ladite tranche homogène, et l'on provoque dans ledit forage ùn écoulement de liquide en relevant, en tête de forage, la variation du débit en fonction de la pression, que, dans une deuxième étape, on poursuit ledit forage jusqu'à la fin de ladite tranche homogène, et l'on provoque un nouvel écoulement de liquide dans le forage, en relevant de nouveau, en tête de forage, la variation du débit en fonction de la pression, et que l'on déduit, des deux courbes ainsi obtenues, la perméabilité de ladite tranche de terrain.1. A method for measuring the permeability of a homogeneous section of a site, characterized in that, in a first step, drilling is carried out in said site until the start of said homogeneous section, and causes in said drilling a flow of liquid by taking note, at the drilling head, of the variation in the flow rate as a function of the pressure, that, in a second step, said drilling is continued until the end of said homogeneous section, and the a new flow of liquid is caused in the borehole, again taking note, at the head of the borehole, of the variation in the flow rate as a function of the pressure, and which is deduced from the two curves thus obtained, the permeability of said slice of ground. 2. Procédé selon la revendication 1, caractérisé par le fait qu'après avoir effectué ledit forage jusqu'au début de la tranche homogène, et après avoir poursuivi ledit forage jusqu'à la fin de la tranche homogène, on relie la tête du forage à un système d'acquisition et de contrôle de la pression ou du débit et on provoque les écoulements de liquidé à partir dudit système.2. Method according to claim 1, characterized in that after having carried out said drilling until the start of the homogeneous section, and after having continued said drilling until the end of the homogeneous section, the drilling head is connected to a pressure or flow acquisition and control system and the liquid flows from said system are caused. 3. Procédé selon l'une quelconque des revendications 1 et 2, caractérisé par le fait que l'on déduit ledit débit en tête du forage de la variation, en fonction du temps, de la pression dans un réservoir pressurisé relié à la tête du forage.3. Method according to any one of claims 1 and 2, characterized in that one deduces said flow rate at the head of the drilling from the variation, as a function of time, of the pressure in a pressurized tank connected to the head of the drilling. 4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé par le fait que l'on provoque l'écoulement du liquide du fond du forage vers la tête du forage, et que, pour relever la variation du débit en fonction de la pression, on trace une droite en portant les couples
Figure imgb0010
 Po étant la pression de la nappe d'eau au niveau où est effectuée la mesure, dw étant la densité de l'eau, s étant la section libre en tête du forage, et S la section libre du forage.4. Method according to any one of claims 1 to 3, characterized in that one causes the flow of the liquid from the bottom of the borehole towards the head of the borehole, and that, to raise the variation of the flow according to the pressure, we draw a straight line by carrying the torques
Figure imgb0010
 P o being the pressure of the water table at the level where the measurement is made, d w being the density of the water, s being the free section at the head of the borehole, and S the free section of the borehole. 5. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé par le fait que l'on provoque l'écoulement du liquide de la tête du forage vers le fond du forage, et que pour relever la variation du débit en fonction de la pression, on trace une droite en portant les couples (QS,PS) dans le plan WS,
Figure imgb0011
Figure imgb0012
 Po étant la pression de la nappe d'eau au niveau où est effectuée la mesure, dw étant la densité de l'eau, s étant la section libre en tête du forage, et 5 la section libre du forage.5. Method according to any one of claims 1 to 3, characterized in that one causes the flow of the liquid from the head of the borehole towards the bottom of the borehole, and that to note the variation in the flow rate as a function of pressure, we draw a line by carrying the couples (Q S , P S ) in the plane W S ,
Figure imgb0011
Figure imgb0012
 P o being the pressure of the water table at the level where the measurement is made, d w being the density of the water, s being the free section at the head of the borehole, and 5 the free section of the borehole. 6. Procédé selon l'une des revendications 4 et 5, caractérisé par le fait que l'on soustrait la droite obtenue lors de la première étape de la droite obtenue lors de la deuxième étape.6. Method according to one of claims 4 and 5, characterized in that the line obtained during the first step is subtracted from the line obtained during the second step. 7. Procédé selon l'une quelconque des revendications 4 à 6, caractérisé par le fait que l'on mesure la pente de la droite ainsi obtenue et que l'on déduit la perméabilité de ladite pente.7. Method according to any one of claims 4 to 6, characterized in that the slope of the straight line thus obtained is measured and that the permeability of said slope is deduced. 8. Procédé selon la revendication 7, caractérisé par le fait que l'on déduit la perméabilité de ladite pente par multiplication par une constante.8. Method according to claim 7, characterized in that the permeability of said slope is deduced by multiplication by a constant. 9. Procédé selon la revendication 8, caractérisé par le fait que ladite constante est :
Figure imgb0013
 où R est le rayon d'action de l'écoulement dans le terrain, ro est le rayon du forage, g est l'attraction de la pesanteur, et l est l'êpaisseur de la tranche de terrain dans laquelle on mesure la perméabilité.9. Method according to claim 8, characterized in that the said constant is:
Figure imgb0013
 where R is the radius of action of the flow in the ground, r o is the radius of the borehole, g is the attraction of gravity, and l is the thickness of the slice of ground in which the permeability is measured .
EP90122300A 1986-05-15 1987-05-15 Method and apparatus for measuring ground permeability Withdrawn EP0429078A1 (en)

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FR8606992A FR2598806B1 (en) 1986-05-15 1986-05-15 METHOD AND DEVICE FOR MEASURING THE PERMEABILITY OF A LAND
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US20180252629A1 (en) * 2015-10-19 2018-09-06 Hz-Dr. Hans Jürgen Hahn Und Dr. Thomas Zumbroich Gbr Substrate permeability measuring device
CN113959924A (en) * 2021-10-27 2022-01-21 中铁二十局集团第一工程有限公司 Slurry horizontal permeability test device and method considering overburden load on stratum

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CN113959924A (en) * 2021-10-27 2022-01-21 中铁二十局集团第一工程有限公司 Slurry horizontal permeability test device and method considering overburden load on stratum
CN113959924B (en) * 2021-10-27 2023-05-30 中铁二十局集团第一工程有限公司 Mud horizontal penetration test device and method considering stratum overburden load

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