FR2677402A1 - METHOD FOR DRILLING A BLIND WELL, IN PARTICULAR A LARGE DIAMETER AND DRILLING TOOL FOR IMPLEMENTING IT. - Google Patents

Abstract

In the context of the present invention, a bottom-up drilling method and a tool 2 suitable for its implementation are presented. A main operation of this process is in fact to widen a pre-existing well. The corresponding tool 2 is provided with arms 22 adapted to be, firstly, folded so that the tool 2 passes within the pre-existing well to be lowered to the bottom 15 of the latter, then secondly. , to be deployed while teeth 23 attack the ground 12, the tool 2 being rotated and pulled by a motor 31 supported by a mast 3 at the surface 11. It is then often advantageous to widen a pilot well in this way, then to repeat the main operation on the resulting well and so on. Despite the number of passes that must therefore be carried out to obtain the well 1 of the desired large diameter, the speed of progression of the tool 2 at each successive widening can in fact be so great that in total, the well 1 is dug much faster and its cost is reduced compared to the usual methods.

Description

The present invention relates to a method for drilling a blind well

especially

  large diameter It also relates to a tool for implementing this method.

  Subterranean cavities are sometimes used to store large quantities of liquid or gaseous products, like hydrocarbons In order to realize them, then to exploit them as reserves, an access well is first dug Its diameter is most often understood between one and a few meters so as to allow the passage

  personnel and digging equipment as well as that of excavated material.

  It is possible to distinguish today two kinds of methods to achieve such an access well especially when it crosses a relatively soft ground The first implements civil engineering techniques, comparable to those used to tunnel Machines as well as workers to drive them work then at the bottom of the well being excavated In case of particularly unstable layers (typically cohesive soils), this often requires freezing the soil beforehand Therefore, the cost of the well penalizes this type of

storage.

  The second method is in turn similar to oil drilling techniques A drilling tool is lowered into the well and is operated from the surface i has the advantage of being able to work while it is immersed in a mud adapted to support the However, given the large diameter of the wells considered, it is necessary to considerably increase the drill string that carries the tool so that the tool exerts on the bottom of the well a sufficient pressure to ensure the attack of the ground. "mass-rods" which are then used, are few

  manageable; Here again, the cost of the work is encumbered.

  Thus, the object of the present invention is to provide a method for producing a well which will be used in particular for access wells to a storage cavity, this method being feasible, particularly in the case of soft ground, more quickly and at a lower cost. by

  compared to conventional methods.

  This object is achieved by a method, a main operation of which according to the present invention is to enlarge a pre-existing well filled with a retaining sludge starting from the bottom to rise towards the surface.

  mouth of the blind well to achieve.

  More specifically, the main operation comprises the steps of: lowering into a pre-existing well a drilling tool having a body adapted to rotate about the well axis and arms provided with elements for attacking the ground by releasing cut and adapted to be deployed to protrude on the body, the tool being lowered while the arms are folded, rotate the body of the drill bit while deploying his arms so that the elements to attack the ground create a shoulder at the well wall that defines the transition between the widening well and the pre-existing well, pull the body so that the elements to attack the ground attack the shoulder and advance it towards the surface of the well. mouth, circulating the mud around the tool so as to drive the majority of the cuttings to the mouth surface, traction and rotation of the tool as well as the circulation of the sludge being maintained until the well has been widened over its entire height. Advantageously, the bottom of the pre-existing well is below the bottom of the blind well to be drilled so as to allow the descent of the tool so that its arms

present at this background.

  Advantageously, the step of lowering the tool is performed by adding rods to a drill string at the lower end of which the tool is suspended. In this case, the steps of rotating and pulling the tool are preferably carried out

  passing the upper end of the drill string into a device of the type "power-

  swivel ", rods being removed from the drill string as the tool is pulled towards the well mouth surface. For example, the power-swivel type apparatus is mounted in a superstructure disposed above the mouth surface of the

well.

  Advantageously, the sludge is circulated by continuously introducing the sludge into the well from its mouth surface and by sucking it under the tool into a tubing to bring it through the well to its mouth surface. Advantageously, a widening factor defined by the ratio of the diameter of the well resulting from the main operation to the diameter of the pre-existing well is chosen in particular according to the mechanical strength of the drilling tool and the drilling tool.

  being pulled and rotated by a motor, depending on the torque that the engine can deliver.

  The enlargement factor is preferably between 1.15 and 1.30.

  Advantageously, a preliminary operation of the method consists in drilling a pilot well, the main operation being conducted a first time while the pre-existing well is the pilot well, then the main operation being repeated while the pre-existing well is the well resulting from the previous iteration, and this until the diameter of the blind well to be drilled is reached, a final operation is finally to coat the well and remove the sludge For example, the enlargement factor is the same at least for a series of consecutive iterations But also, the factor

  at least for a series of consecutive iterations.

  According to a complementary aspect of the present invention, an enlargement factor defined by the ratio of the diameter of the well resulting from the main operation to the diameter of the pre-existing well is chosen in particular according to the mechanical strength of the drilling tool and, drilling tool being pulled and rotated by a motor, depending on the torque that the engine can deliver This factor is preferably

between 1.15 and 1.30.

  Therefore, a preliminary operation of the method consists in drilling a pilot well, main operation being conducted a first time while the pre-existing well is the pilot well, then the main operation being repeated while the pre-existing well is the well resulting from the previous iteration, and this until the diameter of the blind well to be drilled is reached, a final operation finally consisting in coating the well and in

remove the mud.

  The enlargement factor defined above can then, according to the convenience, be the same at least for a series of consecutive iterations or be decreased for

this series.

  The present invention also relates to a drilling tool for carrying out this method. For this purpose, it comprises a body adapted to rotate around the axis of the well as well as arms provided with elements to attack the ground and adapted to pass through. from a folded position on the body to an extended position to protrude from the

body.

  Advantageously, the arms are secured to the body by means of a cam, rack or hydraulic system adapted to move the arms from their folded position to their deployed position and vice versa. However, they can also be secured to the body by a pivotal connection. adapted to put the arms of their

  position folded to their deployed position.

  Advantageously, the arms are adapted to be mounted on a series of bodies

  each having a different diameter.

  Advantageously, the body has a lower extension adapted to allow the mud to pass as well as cuttings In this case, the extension is preferably provided below with an umbrella-shaped deflector so that most of the

  cuttings are guided towards the extension.

  The method according to the invention which has just been summarized is often particularly interesting. For example, the drilling method which consists in widening a pre-existing well starting from the bottom, involves pulling the drill bit. Well this advantage is known in relation to the mining techniques However, the latter provide for the application of the method (then called "raising-boring") only when

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  the bottom of the well communicates with a gallery This configuration indeed allows the evacuation of cuttings (also called in the profession "cuttings") by the gallery o

  they accumulate by simple gravity It is therefore not a question of practicing the "raising-

  boring "in areas that need temporary support such as mud.

  The present process may therefore be regarded as a new application of "raise-boring" in the case of soft terrain and to drill wells without a lower gallery, that is,

  blind She enjoys all the qualities of "raiseboring".

  The additional aspect of the present process highlighted above in connection with a limited enlargement factor also guarantees in certain cases increased performance compared to the usual methods of drilling Suppose in fact that the tool used in the occurrence develops an effort identical to the tool used to traditionally drill the well from top to bottom and all at once As the surface to be attacked at each "pass" represents only a fraction of the total section of the final well , the pressure exerted on the level of the elements which attack the ground, is indeed multiplied It follows a very important speed of advance And as long as the nature of the ground lends itself to it, it exceeds the speed of advancement in drilling traditional in such proportions that the entire well is drilled faster

  despite making several passes.

  Other factors can also save time On one side, the speed with which the tool turns on itself is likely to be increased since we no longer need masses that create a significant rotation reactive inertia The same is true of the force exerted on the tool These parameters are in fact related to the engine employed and in particular to the torque that it is able to develop The resistance offered by a small surface of ground to attack being clearly reduced, this couple remains in each limited pass The superstructure that supports it (and which therefore resumes its torque) can consequently be much lighter than similar devices used in traditional drilling Since the handling of the equipment becomes easier and is carried out As a result, all these factors are more or less complementary to one another, they often guarantee a saving of time and therefore of money justifying the multiplicati It is sufficient for this purpose to optimize, where possible, their number in relation to the properties

  terrain as well as digging equipment.

  As for the present tool, its deployable arms allow its use in blind wells Certainly, in mining technique, different machines have been developed for the implementation of "raise-boring" However the teeth, wheels, etc. that allow them to attack the ground, are not carried by moving arms In practice, they are assembled in the gallery at the bottom of the well where there is enough room for

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  This tool passes on the contrary into the pre-existing well, which allows

a surface assembly.

  Meanwhile in the oil field were developed drilling tools

  equipped with deployable arms These, often called by specialists' under-

  reamers ", must necessarily have a small diameter body, which consequently limits the overall section of the well to be digged As, moreover, the tool works in a conventional manner downwards, the arms and the joints of the arms are particularly stressed and thus know frequent breaks These wideners

  Mobile arms are therefore not suitable for drilling large diameter wells.

  Although the present tool can borrow from the "under-reamers" their technology (for the articulations of the arms in particular), the breaks are much less to fear In relation to the complementary aspect of the present process, the elements to attack the ground that the arms carry, indeed have to apply on a very small surface compared to the complete section of the well Also for a given pressure

  of these elements in the field, the tensile force to be transmitted to the body of the tool does not

  it does not need to be very high This helps to make the connections of the arms made

fragile by their mobility.

  For this purpose again, it is conceivable to develop arms that are adaptable to several bodies. Thus, as the well is enlarged, is the body changed and, with each time a body of diameter greater than the previous one, reaches -we have

  maintain a low rate of stress on the joints of the arms.

  The invention will be better understood on reading the detailed description which follows and

  on examining the attached drawing which represents, by way of non-limiting example, an embodiment of the invention In this drawing: the single figure is a block diagram of the main step of the present method It shows in particular a section of a well being drilled according to this method while a drilling tool adapted to its implementation is meanwhile

  shown in side view within the well.

  According to the single figure, the present method consists first of all in

  Drill a pilot well 1 of small diameter Its diameter can vary between 50 cm and 1 m.

  According to the usual practice in the profession, it is usually measured in inches so that diameters of 26 or 36 inches for example are considered. These values are in fact associated with traditional drilling methods such as those

  using a process called "rotary" very well known in the profession.

  This pilot well 1 is also filled with mud 16 to provide temporary support for its wall 13. In the context of the present method, it is also preferable

  that its bottom is a little below the final bottom of the well to dig.

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  As will be better understood on reading the following paragraphs, the difference in the depth of the bottom of the wells is, in truth, a function of the drilling tool 2 which is

  then descended into the pilot well 1 according to the invention.

  This tool 2 is in fact made up of a body 21 adapted to pass into the pilot well 1 It comprises elements intended to attack the ground, teeth 23 in particular, which are in turn carried by mobile arms 22 These are subjected to the body 21 so as to be folded when in particular, the tool 2 is lowered along the pilot shaft 1 And it is only once the tool 2 reached the bottom of the

  well 1 that the arms 22 are deployed.

  Various mechanical systems can be devised for securing the arms 22 to the body 21. For example, a link involving a cam so that a relative angular position of the arm 22 relative to the body 21 corresponds to the folding of the arm and another position corresponds to the deployment of the arm Let's still quote

  a rack system or a hydraulic system.

  That is, in the main step of the present method, it is expected to rotate the tool 2 about a vertical axis This coincides with the truth of the well The rotation movement is transmitted by a train of rods 34 at the lower end of which the tool 2 is rigidly connected In order to go down or up

  the tool 2, the rods 34 are depending on the case added to the drill string or removed from it.

  Such maneuvers involve routine operations in the profession The rods 34 each have for example a length of 9 m They are maintained

  one after the other for example by means of coupling sleeves.

  The upper end of the drill string 34 advantageously passes into an apparatus known in the art under the name of "power-swivel" 31 that can be translated by motorized injection head. The latter is provided in particular with a motor for printing a motor. relatively fast rotational movement to the drill string 34 At the same time, it exerts on a traction The traction thus developed can

including reaching 200 tons.

  The "power-swivel" 31 is supported, meanwhile, by a metal superstructure disposed on the surface above the well 1 In the context of this perfectly conventional configuration, this superstructure is rather called "mast" 3 It extends in effect well above the "power-swivel" 31 to allow the maneuvers of the rods 34 mentioned above From this point of view, heights of 40 m hook are perfectly conceivable so that a "triple work" "(addition or withdrawal of the rods three by three) is made possible The mast 3 comprises at this

  effect an elevation system illustrated in the figure by a pulley 32 and a cable 33.

  This is how the main step of the present process begins while the tool 2 is lowered to the bottom of the pilot well 1 The "powerswivel" 31 then makes the tool 2 turn around the axis of the well In a first step, the arms 22 of the tool 2 are always folded Provided that their teeth 23 are properly oriented, they then dig a housing in the wall 13 of the well 1 which allows a beginning of deployment for the arms 22 The process continues so far to the complete deployment of the arms 22 Therefore the wall 13 of the well 1 has a

  shoulder 14 at the passage of the housing to the rest of the well 1 located above.

  Its dimension corresponds to the depth of the bottom 15 of the final well, this bottom 15 being separated from the bottom of the pilot well 1 of the distance between the base of the tool 2 and the end

upper arm 22.

  Then, the "power-swivel" 31 begins to exert moreover on the tool 2 a traction It ensures the application of the teeth 23 of the arms 22 deployed against the shoulder 14 As soon as the corresponding pressure becomes sufficient (especially by exceeding a threshold depending on the nature of the ground), it follows the continuation of the digging of the housing And a widening of the well is obtained which, from the bottom, progresses towards the surface as the tool 2 This progression results in fact from the attack of the ground by the teeth 23 of the tool 2 at the level of the shoulder 14, the latter being in a way "machined". This is accompanied by the detachment of matter, grains and larger blocks of land traditionally called "cuttings" 17 And if we were not careful, these cuttings

  would fall to the bottom of the well and accumulate there.

  To limit this inconvenience, the present invention provides for circulating the sludge in which the tool 2 is immersed. Arrows in the figure show a first way to make it flow from the surface 11 of the soil where the sludge 16 is introduced continuously into the well 1 It is then brought to pass along the shoulder 14 during drilling The mud can be activated by a system

  (not shown) pumps or "air-lift" (discharge with pressurized air).

  Thus it is sucked at an extension 25 of the tool 2 If it is clear that the extension 25 must imperatively be fixed under the body 21 to collect the "cuttings" 17, its structure remains a matter of designer's choice The figure fixes the ideas by giving it the simple shape of a tube provided with openings for the passage of the "cuttings" 17 They are in fact discharged with the mud sucked towards the surface 11 while going up inside the string of rods 34 or a sheath provided for this purpose (not shown). Complementary installations can make it possible to separate the cuttings 17 recovered on the surface of the sludge 16 with a view to reintroducing it into the well 1, thus creating a closed-loop flow. It is noted that, compared to comparable drilling methods, the flow of the draining liquid of the "cuttings" 17 occurs here in the opposite direction. This has the particular advantage of guaranteeing a particularly high rate of rise of the sludge, the passage section in the

  stem string 34 or the sheath being significantly weaker than that of the well.

  it is assured to exceed the sedimentation speed of the "cuttings" 17 and therefore of the

train properly.

  However a mud flow in the other direction (normal direction compared to traditional methods) is possible even with relatively low flow rates In this case, the mud descends through the train of rods 34 for example and goes back through the well 1 However, it approaches this last circulation zone at the end of the widened section of the well so that it also sees its speed increase after having loaded with cuttings It is then enough to adapt its rheological characteristics, in particular its viscosity (in particular increasing it) so that the speed of ascent in the part of the well not yet enlarged is

  higher than the sedimentation rate of cuttings.

  In order to ensure a better recovery of the "cuttings" 17 in reverse circulation in particular, the present invention contemplates the advantageous use of a deflector 24 disposed at the lower end of the extension 25, for example a metal part having the shape This deflector 24 then acts as a guide against the flow of the sludge, which thus more effectively drives the "cuttings" 17 towards the extension. The loss of certain debris at the bottom of the well However, this seems inevitable. This is not a problem since they

  can be removed by mud circulation, or even mechanically.

  In accordance with a further aspect of the present invention, the pilot well 1 is thus only partly enlarged. Its new diameter does not exceed its previous diameter by more than a ratio of 1.5 or 2. The enlargement is between 1.15 and 1.30 times its initial diameter. It is from a technological point of view that it is better to limit the area of application of tool 2 to the ground, that is to say ie the shoulder 14 which is "machined" as described above It follows indeed a significant increase in the pressure of the teeth 23 in the field 12 and the speed of progression of the tool 2 is therefore

  generally increased in considerable proportions.

  Thus, to pass from the pilot well 1 to the final well, the present method provides for repeating the main operation that has just been described using the figure And it is in the well just being widened as the tool 2 is lowered, arms 22 folded, that the drill string 34 prints the tool 2 the rotational movement to dig the first housing allowing the progressive deployment of the arms 22, then him

  also transmits the traction so as to widen the well a little more.

  If this new pass involves a series of maneuvers identical to those performed during the first, it is necessary to change the geometry of the tool 2 from one time to the other. The teeth 23 must indeed follow the shoulder 14 which has an average diameter of larger and wider This can be achieved by changing tool each pass More advantageously, using a body 21 whose diameter is adapted to that of the pre-existing well Plus section of the latter is important and the chosen body 21 is massive So the same arms 22 can they

  serve each pass (subject of course to be removable).

  Depending on the equipment available, the operator will be interested in playing on two parameters in particular to establish his enlargement plan. For example, he may choose to widen the well in the same ratio for each pass (constant expansion factor). then, the traction to be developed on the drill string and thus the torque received by the mast 3 increase pass passes in passing with the surface of the shoulder 14 Also, to use from one end to the other the same mast 3, the operator is likely to prefer to maintain a constant torque The enlargement is done in a report

more and more weak.

  When the well has reached the desired final diameter, the present method provides for

  coat it in the usual way, with the retaining sludge removed from the well.

  It can in particular be equipped with a cemented casing.

  The method just described is applicable not only to the digging of access pits to storage cavities in accordance with the stated purpose of starting, but also to the drilling of oil wells. It could be a substitute for the processes currently used and which have been previously mentioned in relation to "under-reamers".

Claims (14)

claims:   A method for drilling a blind well (1) in particular of large diameter and having an axis of revolution, a wall (13), a bottom (15) and a mouth surface (11), characterized in that The main operation of the method consists in widening a pre-existing well filled with a mud (16) of support starting from the bottom (15) to go up to the mouth surface (11) of the well (1) blind to be drilled. 2 Method according to claim 1, characterized in that the main operation comprises the steps of: lowering into the pre-existing well a drilling tool (2) having a body (21) adapted to rotate about the axis of the well ( 1) as well as arms (22) provided with elements (23) to attack the ground by releasing cuttings (17) and adapted to be deployed to project on the body (21), the tool (2) being lowered while the arms (22) are folded, rotating the body (21) of the drill tool (2) while deploying its arms (22) so that the elements (23) to attack the ground create a shoulder (14) at the wall (13) of the well (1) which defines the transition between the widening well and the pre-existing well, pull the body (21) so that the elements (23) to attack the ground attack the shoulder (14) and advance it towards the mouth surface (11), the mud (16) being circulation around the tool (2) so as to drive the majority of the cuttings (17) to the mouth surface (11), the traction and rotation of the tool (2) as well as the circulation of the mud (16) being maintained up to   that the well (1) has been widened over its entire height.   3 Method according to claim 2, characterized in that the bottom of the pre-existing well is below the bottom (15) of the well (1) blind to drill so as to allow the descent of the tool (2) so that its arm (22) occur at the level from this bottom (15).   4 Method according to claim 2 or claim 3, characterized in that the step of lowering the tool (2) is performed by adding rods (34) to a train of   rods (34) at the lower end of which is suspended the tool (2).   Method according to claim 4, characterized in that the steps of rotating and pulling the tool (2) are carried out by passing the upper end of the drill string into a device (31) of the "power-swivel" type with the rods being removed from the drill string (34) as the tool (2) is pulled toward the mouth surface (11) of the well (1).   Process according to claim 5, characterized in that the device (31) of the "power-swivel" type is mounted in a superstructure (3) disposed above the   surface (11) of mouth of the well (1).   Method according to any one of Claims 2 to 6, characterized in that   the sludge (16) is circulated by continuously introducing mud into the well (1) from its mouth surface (11) and sucking it under the tool (2) into a tubing (25, 34) to bring it through the well (1) to its mouth surface (11).   Process according to one of Claims 1 to 7, characterized in that   that a widening factor defined by the ratio of the diameter of the well resulting from the main operation to the diameter of the pre-existing well is chosen in particular according to the mechanical strength of the tool (2) of drilling and, routine (2) of drilling being pulled out and put into   rotation by a motor, depending on the torque that the engine can deliver.   Process according to claim 8, characterized in that the factor   widening is between 1.15 and 1.30.   Method according to claim 8 or claim 9, characterized in that a preliminary operation of the method consists in drilling a pilot well, the main operation being carried out a first time while the pre-existing well is the pilot well, and then the operation principal being reiterated while the pre-existing well is the well resulting from the previous iteration, and this until the diameter of the well (1) blind to drill is reached, a final operation finally consisting in coating the well (1) and removing the sludge (16).   Method according to claim 10, characterized in that the factor   is the same at least for a series of consecutive iterations.   Method according to claim 10, characterized in that the factor   at least for a series of consecutive iterations.   13 Drilling tool for carrying out a method according to any one   of the preceding claims, characterized in that it comprises a body (21) adapted to   rotate around the axis of the well (1) and arms (22) provided with elements (23) to attack the ground and adapted to move from a folded position on the body (21) to a   deployed position to project on the body (21).   14 Tool according to claim 13, characterized in that the arms (22) are secured to the body (21) via a rack cam or hydraulic system, adapted to move the arms (22) from their folded position to their position deployed and vice versa.   Tool according to claim 13, characterized in that the arms (22) are secured to the body (21) by a pivoting connection adapted to pass the arms (22) of   their folded position to their deployed position.   Tool according to one of claims 13 to 15, characterized in that   that the arms (22) are adapted to be mounted on a series of bodies (21) presenting each a different diameter.   Tool according to one of Claims 13 to 16, characterized in that   that the body (21) has a lower extension (25) adapted to allow the   mud (16) as well as cuttings (17).   Tool according to claim 17, characterized in that the extension (25) is provided below with a baffle (24) in the form of an umbrella so that   most of the cuttings (17) are guided towards the extension (25).