Information
-
Patent Grant
-
6533036
-
Patent Number
6,533,036
-
Date Filed
Monday, July 31, 200024 years ago
-
Date Issued
Tuesday, March 18, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Bagnell; David
- Stephenson; Daniel
Agents
- Schlather; Stephen
- Menes; Catherine
- Jeffery; Brigitte
-
CPC
-
US Classifications
Field of Search
US
- 166 268
- 166 290
- 166 666
- 166 667
- 405 249
-
International Classifications
-
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)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0722037 |
Jul 1996 |
EP |
0777018 |
Jun 1997 |
EP |