Method and a tool for treating the wall of a critical zone in a borehole

Information

  • Patent Grant
  • 6533036
  • Patent Number
    6,533,036
  • Date Filed
    Monday, July 31, 2000
    24 years ago
  • Date Issued
    Tuesday, March 18, 2003
    21 years ago
Abstract
The invention relates to a method and to a tool for treating at least one wall in a critical zone of a borehole, in particular a borehole for development of a hydrocarbon, water, gas or analogous field, the method consisting in reinforcing the wall of the critical zone by a coating obtained from a base fluid which is pumped from the surface to a tool (1) to be projected against the wall of the critical zone where it forms the coating once it has set, the method being characterized in that it consists in storing at least one additive or activator in liquid form in a reservoir (R) of the tool (1), and in projecting the additive simultaneously with the base fluid against the wall of the critical zone via at least one injector (I) in order to activate setting of the base fluid.
Description




The present invention relates to a method and a tool for treating at least the wall of a critical zone in a borehole, in particular a borehole for developing a hydrocarbon, gas, water, or analogous field.




A hydrocarbon, water, or gas field is generally developed using a drilling tool such as a drill bit which is rotatably driven from the surface, with transmission being via a drill pipe, or by a motor which is located at drilling tool level and which is mounted at the end of a drill pipe or a coiled tubing.




During the entire drilling operation, a drilling fluid—commonly known as “mud”—is pumped into the hole through the drilling tool. The mud cools the drilling tool and keeps the drilling debris in suspension to enable it to be evacuated to the surface. Another essential function of the mud is to ensure the safety of the well by providing hydrostatic pressure which is higher than the pore pressure of the formation, thus preventing any inadvertent upflow of gas or other fluids. However, the hydrostatic pressure must not exceed the fracture pressure of the rock.




Depending on the depth and type of formations encountered, that balance requires the use of muds of different densities which are incompatible with zones which have already been drilled at lesser depths. As a result, drilling has to be interrupted to position a casing to protect the zones which have already been drilled. Each interruption in drilling then corresponds to a reduction in hole diameter. If a number of critical zones are passed through, the well may have to be abandoned.




It would thus be desirable to have techniques available for at least temporarily treating such critical zones to limit the duration and cost of interruptions to drilling, and to do so with no substantial reduction in the hole diameter.




European patent EP-A-0,777,018 describes a technique for cementing a foundation shaft in the civil engineering industry.




In that document, a shaft is dug that is not necessarily of constant diameter because of the different hardnesses of the rocks through which the bit passes. In order to obtain a foundation shaft of substantially constant diameter, the wall of the shaft is cemented using a tool which is mounted above the bit. Thus, once the shaft is dug, the tool is activated to project a cement slurry against the wall of the shaft as the bit is raised, the body of the tool smoothing the slurry. In practice, the slurry must have a relatively fast setting time, and thus use is made of a Portland cement to which an activator, such as a silicate, has been added to increase the setting speed of the slurry which is pumped from the surface and guided by tubes which open laterally into the tool body.




Defining the composition of a cement slurry is a very complex problem which is difficult to master, in particular as regards selecting which additive(s) to add to the slurry to retard or activate setting, and in what proportion(s).




Such a problem can be solved without too much difficulty for cementing a foundation shaft which is only a few meters deep, as envisaged in the document cited above. The slurry which is pumped from the surface rapidly reaches the tool which projects it against the wall of the shaft.




In contrast, the problem becomes more difficult in the field of drilling to develop hydrocarbon, water, or gas wells which can be very deep, of the order of several hundreds of meters.




A critical zone which must be treated in a borehole may be located at any depth, and so a cement slurry must be controlled to set at the depth at which the critical zone is located, since the slurry must remain fluid until the critical zone is reached. Further, temperature is a parameter which influences slurry setting time, and must be taken into account since temperature increases with borehole depth.




In general, the invention consists both in a method which can control setting of a base fluid used to form a protective coating in a critical zone in a borehole whatever the depth at which the critical zone is located, and in a tool for carrying out this method.




The invention thus provides a method of treating at least the wall of a critical zone in a borehole, in particular a hole for developing a hydrocarbon, water, or analogous field, the method consisting in reinforcing the wall of the critical zone with a coating obtained from a base fluid which is pumped from the surface to a tool to be projected against the wall of the critical zone where it forms said coating once it has set, the method being characterized in that it consists in storing at least one additive or activator in liquid form in a reservoir of the tool, and in projecting the additive simultaneously with the base fluid against the wall of the critical zone to activate setting of the base fluid.




According to another feature, the method consists in raising the tool along the critical zone, while simultaneously projecting the base fluid and the additive by means of at least one injector, and in providing the tool with slip formwork located beneath the injector to keep the base fluid on the wall of the critical zone for a time equal to that required for the base fluid to set.




The invention also provides a tool for carrying out the method, the tool being mounted at the end of tubing to receive a base fluid which is pumped from the surface through the tubing and to project it against the wall of a critical zone detected in a borehole at any depth, the tool being characterized in that it comprises at least:




a reservoir in which an activator is stored to activate setting of the base fluid pumped from the surface and guided to the tool;




injectors to project both the base fluid and the activator simultaneously against the wall of the critical zone; and




a control means activated from the surface to control the operation of the injectors.




As an example, the tool is constituted by at least:




a connection module for connecting the tool to the tubing;




an injection module which comprises at least one reservoir containing an additive or activator in liquid form, and at least one injector to project both the base fluid and the activator simultaneously against the wall of the critical zone; and




a module forming slip formwork located beneath the injector to keep the projected base fluid on the wall in the critical zone for a time equal to that required for the base fluid to set, while the tool is being raised.




A number of embodiments of the tool can be envisaged. The tool can be used alone or in combination with a drilling tool.




When the wall of a critical zone is protected by a cement coating, the base fluid pumped from the surface is advantageously that described in the patent application filed on the same day by the Applicant, entitled “Controlling setting of a high-alumina cement” (inventor: Michel MICHAUX).











Further characteristics, advantages and details of the invention become apparent from the description below, made with reference to the accompanying drawings which are given solely by way of example and in which:





FIGS. 1



a


and


1




b


schematically illustrate the principle of treating a critical zone in a borehole using the method of the invention;





FIG. 2

is a partial cross section of an embodiment of a tool for carrying out the method of the invention, the tool comprising a connection module, an injection module, and a module forming slip formwork;





FIG. 3

is an enlarged view along arrow III in

FIG. 2

to illustrate the connection module of the tool;





FIG. 3



a


is a detail view along arrow IIIa of

FIG. 3

;





FIG. 4

is an enlarged view along arrow IV in

FIG. 2

to illustrate the upper portion of the injection module of the tool;





FIG. 5

is a schematic diagram of an injector of the injection module of the tool;





FIG. 6

is an enlarged view along arrow VI in

FIG. 2

to illustrate the lower portion of the injection module of the tool;





FIGS. 7 and 8

are views similar to

FIG. 6

to illustrate the operation of the tool;





FIG. 9

is a schematic cross section of a preferred embodiment of the tool of the invention; and





FIGS. 10



a


and


10




b


are simplified views to illustrate the principle on which the shutters of the slip formwork of the tool are controlled.











When drilling a section of a hole or well to develop a hydrocarbon field, for example, the drilling tool passes through various formations which have different mechanical properties which are not always compatible with the density of the drilling mud used. This results in the appearance of critical zones, the walls of which must be reinforced before drilling can be continued, for the reasons given above.





FIGS. 1



a


and


1




b


schematically illustrate a section of a borehole in which a critical zone Zc has been detected. With the drilling operation temporarily suspended, this critical zone Zc is treated to form a reinforcing or protective coating


2


on the wall of the critical zone Zc using the method and tool


1


of the invention.




In general, this treatment consists of pumping a base fluid from the surface and projecting it against the wall of the critical zone Zc. However, since a coating is only obtained once the base fluid has set, at least one additive or activator is also projected to activate and accelerate setting of the base fluid.




The method of the invention consists in storing the activator in liquid form in a reservoir disposed in the tool, in projecting it simultaneously with the base fluid against the wall of critical zone Zc using at least one injector I, and while tool


1


is being raised along the critical zone Zc, in using slip formwork C located below injector I to hold the projected base fluid on the wall for a period of time which is equal to that required for the fluid to set.




In order to obtain a coating with substantially constant internal diameter over the entire length of critical zone Zc, the method of the invention also comprises regulating the rate at which the tools is raised as a function of the resistance provided by the base fluid while it is setting and bearing against the top of slip formwork C.




To show the principle of the method schematically illustrated in

FIGS. 1



a


and


1




b


, tool


1


is considered as being used on its own by being mounted at the end of tubing T. This assumes that the drilling tool has been lifted to the surface to allow tool


1


to be lowered.




However, the method of the invention can also be carried out using a tool


1


in combination with a drilling tool.




Such a combination is shown in a preferred embodiment of the method which is described below with reference to the other figures.




The tool illustrated in

FIG. 2

comprises three successive modules M


1


, M


2


, and M


3


in axial alignment, namely: a connection module M


1


, an injection module M


2


, and a module M


3


forming slip formwork.




To facilitate the following description, tool


1


is considered to be in a vertical position so that the adjectives “upper” and “top” correspond to the portion of the tool nearest the surface, and the adjectives “lower” and “bottom” correspond to the portion of the tool nearest the bottom of the well.




Connection module M


1


connects injection module M


2


to the end of tubing T. Module M


1


illustrated in

FIG. 3

comprises axially aligned upper and lower tubular elements


3


and


5


, which are partially inserted one inside the other and connected together by means of a nut


6


, so that lower element


5


can he axially displaced in translation relative to upper element


3


.




Upper element


3


is connected to the tubing T by a screw-and-nut type fastening. The top end of a central channel


7


which passes through upper element


3


opens out to form a threaded annular frustoconical female endpiece


9


to receive a threaded annular male endpiece


10


of complementary shape provided at the bottom end of tubing T. Towards its bottom end, the outside diameter of upper element


3


is reduced to define an annular shoulder


12


. Beyond this shoulder


12


, the outer wall of upper element


3


includes fluting


14


(

FIG. 3



a


) which extends parallel to the axis of upper element


3


and which is open at its bottom end, while the inside wall of central channel


7


is threaded to screw onto the threaded top end of a central liner


15


which penetrates into the inside of an injection module M


2


as is described below.




The top end of lower element


5


of connection module M


1


has a collar


17


which defines an annular shoulder


19


with the body of lower element


5


. A central channel


20


passes through lower element


5


, and the inner wall of the upper portion of this channel


20


has fluting


22


(

FIG. 3



a


) which is complementary in shape to the fluting


14


of upper element


3


. Towards its bottom end, the diameter of the inner wall of channel


20


is reduced to define an annular shoulder


24


.




During assembly, the upper and lower elements


3


and


5


are inserted one inside the other via their respective fluting


14


and


22


. The two ends of a spring


25


mounted inside central channel


20


of lower element


5


bear respectively on shoulder


24


of lower element


5


and on the face of the bottom end of upper element


3


. Nut


6


is slidably mounted around lower element


5


and only its screws onto the outer threaded wall of upper element


3


. The bottom end of nut


6


has an inwardly-directed rim


29


on which shoulder


17


of lower element


5


bears under the action of spring


25


urging upper element


3


away from lower element


5


.




However close or far apart the upper and lower elements


3


and


5


may be, connection module M


1


always ensures fluid communication between tubing T and injection module M


2


through central channel


7


of connection module M


1


, which is axially aligned with central liner


15


. Upper and lower elements


3


and


5


are advantageously dimensioned so that the fluid flow section corresponds to the inside diameter of central liner


15


.




Injection module M


2


(

FIG. 3

) is mounted in line with connection module M


1


and comprises a tubular body


30


having its top end fixed to the bottom end of lower element


5


of connection module M


1


by a screw-and-nut type fastening. The inside wall of the top end of a central channel


32


of body


30


is tapered and threaded to form an annular frustoconical female endpiece


34


which screws onto threaded annular frustoconical male endpiece


36


of complementary shape provided at the bottom end of lower element


5


of connection module Ml.




Referring to

FIG. 4

, central liner


15


is freely mounted inside channel


32


of body


30


, with interposition of an upper guide sleeve


38


mounted in the upper portion of channel


32


and a lower guide sleeve


39


mounted in the lower portion of channel


32


. Sleeves


38


and


39


are integral with body


30


and include inner and outer grooves


38




a


and


39




a


in which O-rings (not shown) are mounted to ensure sealing.




Injection module M


2


projects base fluid pumped from the surface through tubing T and connection module M


2


. Projection against the wall of critical zone Zc is effected by at least one injector I which also simultaneously projects an activator to activate and accelerate setting of the base fluid to form the coating.




The activator is stored in a reservoir R located in injection module M


2


. As an example, an enclosure


40


is provided in the upper portion of body


30


of injection module M


2


. This enclosure


40


is constituted by a cylindrical wall


42


coaxially mounted around body


30


and closed by annular upper and lower caps


44


and


45


fixed to body


30


. The inside volume of enclosure


40


is separated into two parts by a pressure and volume compensating means


47


constituted by an elastically deformable element such as a rubber membrane M. Membrane M is cylindrical and its two ends are fixed to body


32


by means of the caps


44


and


45


.




Thus the inside of enclosure


40


is subdivided into an inner annular chamber


48


and an outer annular chamber


50


which forms reservoir R for the activator. Fluid circulation in chamber


48


is ensured by central liner


15


. The upper portion of chamber


48


can communicate with the inside of central liner


15


via a radial channel


52


passing through body


30


, a lateral opening


54


passing through upper sleeve


38


, and a lateral opening


55


passing through central liner


15


. In analogous fashion, the lower portion of chamber


48


can communicate with the inside of central liner


15


via a radial channel


56


passing through body


30


, a lateral opening


58


passing through lower sleeve


39


, and a lateral opening


59


passing through the wall of central liner


15


.




Elastically deformable toroidal flanges L are mounted around the outer wall


42


of enclosure


40


. The outside diameter of the regularly spaced flanges L is advantageously greater than the enlarged diameter of the critical zone to be treated. These flanges L center tool


1


during its displacement and also separate the fluids.




Body


30


of injection module M


2


carries


3


injectors I, for example, which are mounted in body


30


and located beneath enclosure


40


containing reservoir R.




Each injector I (

FIG. 6

) is mounted in a bush


60


fixed and sealed in a lateral opening


62


passing through body


30


of injection module M


2


. Each injector I (

FIG. 5

) comprises a piston


64


with a main central channel


65


passing through its body to eject and project base fluid pumped through central liner


15


against the wall of the critical zone. The fluid flow section of the central channel


65


is not uniform but has two opposed truncated cone shapes in order to produce the known Venturi effect.




Piston


64


is in slidable and sealed contact with bush


60


by means of front


66


and rear


68


collars. Front collar


66


, which corresponds to the outlet from central channel


65


, has a secondary channel


70


passing through it axially for ejecting activator stored in reservoir R. Rear collar


68


is formed by an annular cap which screws onto the piston body


64


.




The front


66


and rear


68


collars define an annular space


72


. An annular rib


74


projecting from the internal wall of bush


60


penetrates into this annular space


72


. The two ends of a spring


76


lodged in this space


72


and mounted around piston


64


bear on the rib


74


and on the rear collar


68


of piston


64


respectively. In secondary channel


70


, an elongate finger or needle


80


carried by rib


74


engages the activator outlet.




The annular space


72


is in permanent communication with reservoir R. Rib


74


and bush


60


have a channel


82


passing through them radially and communicating with a peripheral groove


84


provided in the outer wall of bush


60


. A channel


86


passes through body


30


of injection module M


2


and through lower cap


45


to provide a fluid connection between groove


84


and reservoir R.




The main base fluid outlet channel


65


can communicate with the interior of central liner


15


via an opening


88


passing through lower sleeve


39


and an opening


90


passing through the wall of central liner


15


.




Piston body


66


of each injector I can take up two positions. In a first “retracted” position, rear collar


68


is in contact with the lower sleeve


39


by the action of return spring


76


, such that needle


80


passes through the whole of secondary channel


70


and blocks its fluid flow section. In the second position, part of piston


64


projects beyond bush


60


and compresses spring


76


to partially disengage needle


80


to free the fluid flow section of secondary outlet channel


70


. A cylindrical part


92


mounted coaxially around piston body


66


limits the stroke of injector I as it moves to its second position.




Advantageously, at least one guide means


94


centers and guides piston


64


of injector I. This guide means


94


is constituted by a second finger or needle


96


carried by rib


74


which engages in a blind hole


98


formed in front collar


69


.




The position of piston


64


of injectors I is defined by a control means


100


described below with reference to

FIGS. 6 and 7

.




Central liner


15


extends inside body


30


of injection module M


2


beyond lower sleeve


39


. The bottom of central liner


15


is at least partially blocked and its bottom end is pierced by a plurality of openings


102


. These openings


102


ensure fluid communication between central liner


15


and the central channel


32


of body


30


the diameter of which has been enlarged down to its bottom end.




Control means


100


(

FIG. 7

) comprises a projectile such as a spike or dart


105


which is dropped from the surface into tubing T. A retaining means


107


is provided in the central liner


15


to temporarily block dart


105


before it drops to the bottom of central liner


15


. Retaining means


107


is mounted above openings


102


of central liner


15


and at a level which is located just before the bottom end of lower sleeve


39


of body


30


. Retaining means


107


comprises retractable fingers


110


which are lodged in openings


112


formed around central liner


15


and located at the same level. These fingers


110


bear on the outer wall of lower sleeve


39


to project slightly inside central liner


15


to stop dart


105


which automatically activates injectors I as described below.




The periphery of dart


105


is advantageously equipped with elastically deformable flanges, made of rubber for example. During its fall, dart


105


separates the fluids, namely drilling mud already contained in tubing T and base fluid pumped behind dart


105


. Once stopped in central liner


15


, dart


105


acts as a seal to force the base fluid to be directed towards injectors I.




As tool


1


rises, volume compensation inside and outside tool


1


must be ensured. Fluid communication is ensured by at least one duct


115


which passes through reservoir R. This duct


115


opens to the outside through upper cap


44


of chamber


40


and inside channel


32


of the injection module at a level located below retaining means


107


for projectile


105


. An anti-return valve


117


is lodged in duct


115


, for example at the level of upper cap


44


of enclosure


40


. This valve


117


establishes fluid circulation in one direction only, namely from top to bottom i.e., from the outside to the inside of tool


1


.




Module M


3


forms slip formwork C which is mounted in the extension of injection module M


2


. Slip formwork C keeps the base fluid on the wall in critical zone Zc for a time equal to that required for the fluid to set as tool


1


rises along the critical zone Zc.




Module M


3


(

FIG. 9

) comprises a tubular body


120


which defines a central channel


122


located in an extension of central channel


32


of body


30


of injection module M


2


. The top end of body


120


is arranged so as to form a threaded annular truncated cone-shaped female endpiece


123


which screws onto a threaded annular truncated cone-shaped male endpiece


124


provided at the bottom end of body


30


of injection module M


2


.




Slip formwork C is constituted by three extensible shutters


125


mounted around body


120


to form a substantially cylindrical envelope around which an elastic membrane


127


, made of rubber for example, is mounted to ensure continuity of the envelope between the deployed and retracted positions of shutters


125


.





FIGS. 10



a


and


10




b


illustrate the control of shutters


125


in a deployed position (FUG.


10




a


) and in a retracted position (

FIG. 10



b


), the direction of fluid circulation being indicated by arrows.




Each shutter


125


is controlled by an upper set of rods


130


associated with an upper piston


132


and by a lower set of rods


130


associated with a lower piston


134


. Each set of rods comprises a rod


130




a


, one end of which is hinged to a fixed point P


1


on body


120


, and a rod


130




b


one end of which is hinged to the free end of a shaft


136


which extends the associated piston


132


or


134


. The two free ends of the two rods


130




a


and


130




b


are hinged to shutter


125


at a point P


2


through a slot


138


(

FIG. 9

) passing through body


120


.




The two pistons


132


and


134


are hollow, and the shaft


136


of each piston is constituted by a sleeve. The two pistons


132


and


134


are in axial alignment and are mounted in a recess in the body


120


of module M


3


. A return spring


140


is mounted around each shaft or sleeve


136


and its two ends bear respectively on piston


132


or


134


and on a fixed point formed by a shoulder


142


of body


120


.




In general, the rod mechanisms


130


are designed so that a force exerted downwards on the shutters


125


tends to deploy them, while a force exerted upwards tends to retract them against body


120


. The two pistons


132


and


134


are kept away from each other by the action of return springs


140


such that deformation of the rods


130


causes retraction or deployment of the shutters


125


. The maximum diameter of the envelope defined by shutters


125


is always less than the diameter of the borehole so as to leave an annular space, for example of the order of a few millimeters.




The upper and lower portions of shutters


125


are conical in shape


145


to provide lower resistance during displacement of tool


1


and also to measure the resistance provided by the base fluid (FIGS.


2


and


9


).




Module M


3


, which carries the slip formwork C, is axially connected to a drilling tool


150


via a screw type fastening lug


152


(FIG.


9


).




In the embodiment shown in

FIG. 9

, flanges L which surround enclosure


40


of injection module M


2


are advantageously mounted obliquely to facilitate circulation of drilling fluid and the upflow of debris when drilling tool


150


is in action.




The general operation of tool


1


is now described.




The well drilling operation is interrupted when the drilling tool


150


has passed through a critical zone Zc which is detected at the surface. Tool


1


is then used to treat the wall of critical zone Zc without needing to lift drilling tool


150


to the surface.




Drilling tool


150


can advantageously be used to carry out a prior treatment which consists of enlarging the diameter of critical zone Zc so that the thickness of the protective coating which will be formed on the wall does not reduce the diameter of the borehole substantially. The resistance provided by the rock to the drilling tool


150


generates a reaction which is applied upwards to the tool


1


. This reaction force is transmitted to lower element


5


of connection module M


1


which moves in translation towards the upper element


3


of module M


1


and compresses return spring


25


mounted between the upper and lower elements


3


and


5


. Connection module MI is thus compressed. However, central liner


15


cannot undergo this displacement as it is integral with the upper fixed element


3


of the connection module Ml. This thus causes injection module M


2


to move relative to liner


15


, which isolates injector I following axial displacement of opening


90


of liner


15


. This opening


90


no longer faces opening


88


in lower sleeve


39


which ensures fluid communication between the inside of liner


15


and the main channel


65


of each injector I.




During this preliminary treatment, drilling mud is pumped inside tubing T. This mud passes freely through tool


1


, in particular injection module M


2


, but cannot pass through the injectors I.




Once the critical zone diameter enlarging operation has been completed, no further reaction force is exerted on drilling tool


150


. Return spring


25


can relax to force apart the upper and lower elements


3


and


5


of connection module M


1


which is no longer under compression.




Dart


105


is dropped inside tubing T and pushed by the base fluid which is pumped behind it. When dart


105


reaches central liner


15


of injection module M


2


, its fall is stopped by retaining fingers


110


. Central liner


15


is thus blocked by dart


105


which forms a sealed cap to force base fluid to flow through the injectors I.




In this situation, illustrated in

FIG. 7

, the pressure in central liner


15


increases, and creates a pressure differential at the terminals of piston


64


of injectors I. The pressure of the base fluid acting on collar


68


located at the rear of piston


64


causes the piston


64


to move axially which partially disengages needle


80


to open secondary channel


70


and the activator stored in reservoir R can then be ejected simultaneously with the base fluid which is being ejected by the central channel of injectors I.




An increase in the pressure in the liner causes base fluid to flow from chamber


48


in enclosure


40


which tends to deform membrane M towards reservoir R while there is no pressure equilibrium between chamber


48


and reservoir R and to compensate for the volume of activator which is forced from reservoir R. Membrane M acts as a piston.




Injectors I thus simultaneously project the base fluid and its activator against the wall of the critical zone as tool


1


rises. Given that there is no further continuous circulation of fluid inside the tool because of the presence of dart


105


in central liner


15


, the shutters


125


are automatically deployed by the action of springs


140


. The base fluid ejected by injectors I sets due to the action of the activator and starts to bear on the upper conical portion of shutters


125


. The base fluid creates resistance which tends to oppose the tool


1


being raised. The upward speed of tool


1


is advantageously regulated as a function of this resistance to obtain a coating of substantially constant diameter over the entire length of the critical zone. The more the resistance increases due to an increase in the level of base fluid and/or the rate of setting of the base fluid, the higher must be the speed of tool


1


. Conversely, the lower the resistance, i.e., when the base fluid is still liquid, the lower must be the upward speed of the tool


1


.




A sufficient quantity of base fluid is pumped to treat all of the critical zone, and then mud is pumped to clean injectors I to remove all traces of base fluid.




After this cleaning operation, pumping is stopped and tool


1


is lowered into the borehole so that the end of drilling tool


150


comes into contact with the bottom of the hole. This contact causes a reaction force which, as explained above when the critical zone was enlarged, causes connection module M


1


to compress. Injection module M


2


is then displaced with respect to central liner


15


by a height which is sufficient to move retaining fingers


110


apart and to allow dart


105


to be pumped to the bottom of central liner


15


to re-establish circulation of drilling mud through the well. Once dart


105


has been freed, drilling tool


150


is disengaged from the hole bottom to re-establish circulation of fluid through tool


1


, which removes the pressure differential in the terminals of injectors I, and return spring


76


returns the piston


64


to its initial position where the needle


80


again blocks outlet channel


70


through which activator was ejected (FIG.


8


).




The control means for injectors I can be reactivated by dropping a new dart


105


, in particular when the treatment is carried out in several successive stages.




In general, tool


1


can extend over a length of the order of 15 meters, for example.




It should be noted that the tool control means uses only hydraulic and/or mechanical means, i.e., there is no need for additional means, such as electrical cables and/or additional ducts, which would inevitably make the structure of the tool more complex.




The method and the tool of the invention can treat the entire length of a critical zone in a borehole continuously when the tool is connected to a coiled tubing. In contrast, this treatment is carried out in successive steps when the tool is connected to a drill pipe and when the length of the critical zone is longer than one component module of the drill pipe which corresponds substantially to the height of the well rig.




Variations can, of course, be made to the tool described above. In particular, its slip formwork C can be formed from a sealed envelope which is extensible and filled with, a fluid which would be controlled in analogous fashion to the shutters.



Claims
  • 1. A method of treating the wall of a critical zone in a borehole, the method consisting in reinforcing the wall of the critical zone with a coating obtained from a base fluid which is pumped from the surface to a tool to be projected from an injector against the wall of the critical zone where it forms said coating once it has set, the method being characterized in that it consists in storing at least one additive or activator in liquid form in a reservoir of the tool, and in pumping the base fluid through tubing to a channel which passes through the tool and creating a pressure differential in the terminals of the injector by at least temporarily obstructing the channel of the tool by dropping a projectile from the surface in the tubing and pushing it with base fluid pumped through the tubing to reach the channel of the tool, and stopping the projectile with a retractable retaining means so as to increase the pressure inside the channel of the tool to automatically control the injector and to cause the base fluid and its additive to be projected simultaneously against the wall of the critical zone.
  • 2. A method according to claim 1, characterized in that it consists in lifting the tool through the length of the critical zone, simultaneously projecting the base fluid and the additive by means of at least one injector, and providing the tool with slip formwork located beneath the injector to maintain the base fluid on the wall of the critical zone for a time equal to that required for the base fluid to set.
  • 3. The method according to claim 2, characterized in that it consists in using the resistance provided by the base fluid during setting, which resistance is exerted on the upper portion of the slip formwork and tends to oppose the upwards movement of the tool, to obtain a coating with an inside diameter which is substantially constant along the entire length of the critical zone.
  • 4. A method according to claim 3, characterized in that it consists in measuring the force of this resistance provided by the base fluid during setting to regulate the rate at which the tool is raised along the critical zone.
  • 5. The method according to claim 2, characterized in that it consists in providing the slip formwork with an overall cylindrical shape the diameter of which can be regulated and providing the upper portion of the slip formwork with a conical shape.
  • 6. A method according to claim 2, characterized in that it consists in providing the slip formwork with a length which is calculated to allow the base fluid to set during the upward movement of the tool along the critical zone.
  • 7. A method according to claim 1, characterized in that it consists, from the surface, in causing the base fluid to be projected against the wall of the critical zone simultaneously with its additive.
  • 8. The method according to claim 1, characterized in that it consists in stopping simultaneous projection of the base fluid and its additive by freeing the projectile from the tool channel, and in that it comprises freeing the projectile by exerting a mechanical force on the retaining means to retract it and re-establish fluid circulation through the tool channel.
  • 9. A method according to claim 1, characterized in that it consists of enlarging the diameter of the critical zone prior to simultaneous projection of the base fluid and its activator.
  • 10. A tool for treating at least the wall of a critical zone in a borehole, the tool being mounted at the end of tubing to receive a base fluid which is pumped from the surface through the tubing and to project it against the wall of a critical zone detected in a borehole at any depth, the tool being characterized in that it comprises at leasta reservoir in which an activator is stored to activate setting of the base fluid pumped from the surface and guided to the tool; at least one injector to project both the base fluid and the activator simultaneously against the wall of the critical zone, the injector including an annular space that permanently communicates with the reservoir; and a control means activated from the surface to control the operation of the injector.
  • 11. A tool according to claim 10, characterized in that it is constituted by at least:a connection module for connecting the tool to the tubing; an injection module which comprises at least one reservoir containing an additive or activator in liquid form, and at least one injector to project both the base fluid and the activator simultaneously against the wall of the critical zone; and a module forming slip formwork located beneath the injector to keep the projected base fluid on the wall in the critical zone for a time equal to that required for the base fluid to set, while the tool is being raised.
  • 12. A tool according to claim 11, characterized in that the injection module comprises a movable or deformable means for compensating for the pressure and volume in the reservoir during simultaneous projection of the base fluid and activator, the movable or deformable means being automatically controlled by the fluid pumped through the tool.
  • 13. The tool according to claim 12, characterized in that the pressure and volume compensating means is constituted by an elastically deformable element such as a rubber membran.
  • 14. The tool according to claim 12, characterized in that the injection module comprises an enclosure the volume of which is separated into two portions by the pressure and volume compensating means, namely into a first chamber in which fluid pumped through tool is circulated, and a second chamber. forming the reservoir which is in communication with the injector.
  • 15. A tool according to claim 14, characterized in that the enclosure is constituted by a cylindrical wall mounted coaxially around the body of the injection module and closed by an annular upper cap and by an annular lower cap fixed on the body.
  • 16. The tool according to claim 14, characterized in that the injection module comprises a central liner in communication with the tubing through the connection module, and in that the central liner communicates with the chamber via an upper radial channel passing through the body and a lateral opening passing through the central liner, and via a lower radial channel passing through the body and a lower lateral opening passing through the central liner to ensure circulation of fluid in the chamber from the fluid pumped through the central liner.
  • 17. The tool according to claim 16, characterized in that the injector is controlled from the surface by a control means actuated from the surface.
  • 18. The tool according to claim 17, characterized in that the control means is constituted by a projectile such as a spike or dart which is dropped from the surface in the tubing and in that it comprises a retractable retaining means lodged in the central liner to stop the descent of the projectile, the retaining means being located beneath the injector.
  • 19. A tool according to claim 18, characterized in that the retaining means is constituted by retractable fingers lodged at the same level in lateral openings passing through the central liner.
  • 20. A tool according to claim 18, characterized in that fluid communication is ensured by at least one duct which passes through reservoir, one end of which opens near the top at the exterior of the tool and the other end of which opens near the bottom into the inside of the tool at a level located beneath the retaining means and projectile.
  • 21. The tool according to claim 16, characterized in that the connection module comprises two elements, upper element and lower element, partially inserted one inside the other by means of respective grooves, and held apart from each other by a spring, and in that the central liner is integral with the upper element.
  • 22. The tool according to claim 11, characterized in that injector is movable between two positions and comprises a piston slidably mounted in a fixed bush mounted in a lateral opening of body of injection module, and in that the piston has a main central channel passing therethrough to eject base fluid and at least one secondary channel to simultaneously eject the activator contained in the reservoir.
  • 23. A tool according to claim 22, characterized in that the piston is mounted in sliding and sealed contact with the bush by means of a front collar and a rear collar, and in that the front collar has the secondary channel passing axially therethrough.
  • 24. A tool according to claim 23, characterized in that between them the front and rear collars :define an annular space, in that an annular rib projecting from the internal wall of the bush penetrates into this annular space, and in that the two ends of a spring lodged in this space and mounted around the piston bear respectively on the rib and the rear collar of the piston.
  • 25. A tool according to claim 24, characterized in that an elongate finger or needle carried by the rib engages in the secondary channel to obstruct or partially free the fluid flow section of this channel.
  • 26. A tool according to claim 22, characterized in that a channel passes radially through the rib and the bush and communicates with a peripheral groove provided in the outer wall of the bush, and in that a channel passes through the body of the injection module and through the lower cap of the vessel to put the reservoir into communication with the secondary channel for ejecting the activator.
  • 27. A tool according to claim 11, characterized in that the slip formwork is constituted by shutters which form an overall cylindrical envelope covered by an elastic membrane, and in that each shutter has a conical portion near each of its ends.
  • 28. A tool according to claim 10, characterized in that fluid communication is ensured between the outside and inside of the tool for volume compensation while the tool is rising along the critical zone.
Priority Claims (1)
Number Date Country Kind
97 16500 Dec 1997 FR
PCT Information
Filing Document Filing Date Country Kind
PCT/EP98/08536 WO 00
Publishing Document Publishing Date Country Kind
WO99/34093 7/8/1999 WO A
US Referenced Citations (8)
Number Name Date Kind
2965171 Howard et al. Dec 1960 A
3108024 Battle Oct 1963 A
3977360 Mihaly Aug 1976 A
4055958 Hanson Nov 1977 A
4784223 Worrall et al. Nov 1988 A
4867240 Colla Sep 1989 A
5533570 Streich et al. Jul 1996 A
5718287 Streich et al. Feb 1998 A
Foreign Referenced Citations (2)
Number Date Country
0722037 Jul 1996 EP
0777018 Jun 1997 EP