EA040552B1 - DIRECTIONAL DRILLING - Google Patents

Description

The field of technology to which the present invention relates

The present invention relates to directional well drilling. In particular, the present invention relates to the creation of a lateral wellbore that extends from the main wellbore.

In principle, the present invention can be used to drill wells for a variety of purposes. However, in the present document, the present invention is described in relation to drilling wells for the purpose of extracting core samples from underground formations.

Background of the Invention

Drilling is the most reliable and accurate way to perform 3D underground surveys. For example, exploratory diamond drilling techniques can be used to explore and define the boundaries of underground mineral deposits such as ore lenses.

During exploratory drilling, core samples are periodically taken from the well, which are documented and transferred to storage for further analysis. For example, core samples taken from a plurality of wells spaced transversely apart can be used to build geological profiles. Due to this, the continuity, extent of occurrence and composition of the underground resource is established, which helps to determine and calculate the available minerals.

Conventionally, drilling a well is done with a drilling rig located above or below ground that assembles and rotates a drill string that is lowered into the well. The drill string contains a plurality of drill pipes, which are joined together by means of threaded couplings.

The rig lowers the drill string into the well as the annular rock cutting tool containing the diamond drill bit or drill bit at the bottom of the rotating drill string passes through the subterranean formation. The rig builds up the drill string by successively adding additional drill pipes that are attached to the top of the drill string as it is lowered into the deepening hole. To cool the rock cutting tool and remove drilling cuttings, a drilling fluid is used, for example, based on water, which is pumped along the drill string.

The well may be conditionally vertical or it may be deliberately deviated from the vertical. The well may even extend substantially horizontally or be bent upwards at least partially. In either case, the standard borehole tends to bend slightly along its length as the drillstring trajectory is affected by underground conditions and gravity.

In relation to the exploration of mineral deposits, the well often goes underground in the direction of the target to a depth of 1 to 2 km or more. Therefore, it may take several hours to fully assemble the drill string and several additional hours to dismantle it, for example, to replace the rock cutting tool.

During operation, the rock cutting tool rotates and takes cylindrical core samples, which are fed into the hollow drill string. Sequentially selected core samples should be taken to the surface every few meters of penetration. To avoid delays in dismantling the drill string while it is being retrieved from the hole, the last core sample must be retrieved to the surface before the drill string is pulled out.

This principle is the basis of retractable core core drilling, in which the core sample enters the inner core tube, which is located concentrically inside the outer drill pipe at the bottom of the drill string. This bottommost drill pipe defines the outer core pipe, which carries the rock cutting tool. Periodically, a rope is connected to the core receiver, which is brought from the surface inside the well, so that it is possible to lift the inner core pipe with a core sample from it, telescopically pulling it out of the outer core pipe, which covers the inner core pipe.

Traditionally, delineation of underground mineral deposits has been accomplished by drilling multiple wells from the surface of the earth. However, area drilling occupies a large area of land, creates access problems, uses many pieces of valuable drilling equipment, and wastes too much time and money. Taking into account these shortcomings, directional drilling methods have been developed, which involve drilling from the surface of only one parent or main wellbore, which already branches underground into one or more secondary sidetracks. These lateral wellbores can themselves branch into one or more tertiary laterals, each of which, in principle, can also have additional branches.

Thus, directional drilling allows one main wellbore at the surface of the earth to interact with one or more of its branches underground. The lateral wellbores provide additional intersections with the underground target, with the required spacing between adjacent wellbores being, say, 40 m.

- 1 040552 area drilling from the surface of the earth for directional drilling requires a smaller area and fewer units of drilling equipment, which saves time and money. Indeed, each sidetrack typically saves four to five weeks of conventional core drilling to a comparable depth.

For ease of reference, the present description defines the nearest preceding branch as the main wellbore, and the immediately subsequent branch branching from that wellbore as the lateral wellbore, whether or not any additional branches precede the main wellbore.

According to one approach to mineral exploration, a vertical main wellbore can be drilled through the entire main stratigraphic section of the deposit in order to determine the geological conditions and the local structure of this deposit. Upon completion of drilling, the main wellbore is surveyed from its lower part to the ground surface. As a result, the three-dimensional position and shape of the main wellbore are accurately determined, which makes it possible to calculate the parameters of the sidetracks diverted from it.

Upon completion of drilling and shooting of the main wellbore and, if it is necessary to create a sidetrack, the first step is to determine the sidetracking point or KOR. The kickoff point is located at the depth at which the sidetrack must deviate from the longitudinal axis of the main wellbore. The kickoff point can be located, for example, above the bottomhole at a depth of, say, 900 m in the main wellbore with a depth of, say, 1500 m. its lateral surface to initiate a lateral wellbore.

Said wedge comprises an elongated, generally cylindrical body that fits exactly in size into the main wellbore at the sidetracking point. A shallow inclined section is cut in the body of the wedge, deviating from its central longitudinal axis, which defines a concave surface or face of the wedge tapering upwards. One well-known example of such a wedge is known in the drilling industry as a Hall Row wedge or whipstock.

The use of a deflector wedge is well known in the art. Typically, this wedge is connected to the milling head by a shear pin coupling, examples of which are disclosed in US 3,908,759; US 5647436; US20060037759; WO 02/02903; CN 105649564; ON 205477483 and ON 205477484.

Other prior art examples of directional slips are described in the following documents: WO 2017099780; SA 2475602; US 2445100; US 3029874; CN 202348244; CN 202544778; US 4182423; CN 203547610; CN 2753868; CN 2763455; EP664372; US 1608711; CN 205876188; US 9951573; GB 2304760; GB 727897; CN 202348191; US 2003/010533; US20130168151; DE 3832715; US 6003621; US 6360821; US 6092601; CN 202348191; US20070240876; CN 204139966; US20160326818; US20070221380; US 9617791; US 6076606; US20020170713; US 8245774; US 5871046; US 7124827; US20030196819; EN 2650163; S.U. 878894; S.U. 857416; US20030213599; US 6910538; US 6427777; WO 2011/150465; US 6899173; US 5785133; and CN 204960847.

Typically, placing a wedge in the main wellbore is a complex and time-consuming process requiring many trips to the drill string. In each such operation, the drill string is assembled to be lowered to the kickoff point and then disassembled to be lifted away from the kickoff point. For example, a standard wedge placement involves placing two plugs in series in the wellbore to hold the wedge that is then set. In turn, each plug, behind which the wedge is located, must be installed by lowering it to the sidetracking point also with the help of a drill string.

The first stopper is a mechanically expandable metal stopper, for example, marketed under the trade name Van Ruth. Such a plug may be driven into the wellbore and delivered to the kickoff point while attached to the bottom of the drill string, or it may be propelled by water pressure to move along the drill string and delivered to the kickoff point where the plug is exits the drill string and expands to engage with the surrounding wall of the wellbore. In both cases, to deliver the plug to the sidetracking point, the drill string must first be assembled and then disassembled.

The second stopper is a cylindrical wooden stopper. This plug is driven into the wellbore while attached to the bottom of the drill string and rests on the first plug that was installed earlier. The second plug is designed to slide into the wellbore with very little clearance and is typically made of soft wood to absorb moisture and swell at the site so that it engages with the surrounding wall of the wellbore. As in the previous cases, to install a second plug on top of the first plug, the drill string must first be assembled and then disassembled.

The second cork is usually left in place at least overnight to swell and take its final position. After that, a wedge is assembled, which is lowered into the wellbore,

- 2 040552 being attached to the bottom of another drill string. Once inserted into the wellbore, the wedge is lowered to a point just above the wood plug and leveled by rotating the drill string so that the wedge face is facing the desired azimuth. The azimuth can be determined relative to the direction of the north magnetic pole in essentially vertical shafts or relative to the center of gravity in inclined shafts.

Upon completion of the alignment of the wedge face according to the required azimuth, this wedge is securely fixed in its place by engaging it with a wooden plug. Typically, this process involves using a drill rig to lower the drill string, causing the sharp cutting edge at the bottom of the wedge to cut into the wood plug. The wedge may also be cemented in the main wellbore.

The wedge is now ready to deflect the drill string in order to initiate a lateral wellbore. The lateral wellbore will extend down and out of the main wellbore at approximately the desired azimuth, which was determined by the orientation of the wedge face. Of course, the beginning of the process of creating a lateral wellbore involves performing another tripping operation with disassembly of the drill string and reassembly of the drill string.

Once the wedge has been fixed in place, a few more meters can be drilled below the wedge by conventional drilling with a retrievable core tube in order to set up a lateral wellbore. At this stage, the magnetic influence of the wedge is eliminated, and due to this, the equipment for directional drilling with the help of a downhole motor can be correctly oriented in the lateral wellbore. Downhole motor drilling provides the required inclination and azimuth of the newly created lateral wellbore before resuming conventional core core drilling.

Thus, after the drilling of a new lateral wellbore on the other side of the plug is started, the drill string must be removed from the well using conventional core drilling with a removable core barrel. Next, the downhole motor directional drilling equipment must be assembled, which is lowered into the lateral wellbore while attached to the bottom of the drill string. After passing every few meters, the downhole motor drilling method should be checked for orientation, and if necessary, the orientation of the tool should be corrected. If drilling of the lateral wellbore is performed with the required inclination and azimuthal direction along the correct trajectory, then the downhole motor drilling stage is completed and the drill string with the downhole motor drilling equipment is retrieved to the surface.

Reaming equipment can then be lowered onto the drill string to expand the wellbore at its greatest bend near the sidetracking point, whereby the wellbore is flattened and enlarged in diameter, making it easier for the drill string to pass through this bend. Upon completion of the reaming, the drill pipe string with the reaming equipment is retrieved to the surface, after which the conventional core drilling of the lateral wellbore with a removable core receiver is resumed until the underground target is reached, accompanied by core sampling. During said last stage of RT core drilling, additional measurements may be taken periodically to check the wellbore trajectory to ensure that the target has been achieved and that no corrective directional drilling is necessary.

When drilling of the lateral wellbore is completed, its angle and azimuth are measured at specified intervals from below to above the wedge to provide accurate position data and facilitate calculations for any subsequent secondary or tertiary offshoots of the wellbore.

Each trip involving the assembly of a drill string or a drill string and its subsequent disassembly may take an entire shift, with two or more operators operating the drilling rig on the surface. It is obvious that the duration, and hence the associated costs associated with these repetitive trips, is a significant disadvantage.

Multiple trips also increase the risk that something may go wrong while lowering or retrieving the drill pipe or drill string. For example, the wall of the wellbore may collapse inward, or cuttings may accumulate on top of the plugs. It is even possible for drill pipes to fall into or out of the wellbore, potentially causing injury to operators and disrupting drilling operations.

Another problem with conventional wedge installation is that the engagement of the wooden plug with the cutting edge at the bottom of the wedge can be unreliable, particularly if slurry accumulates over the plug due to multiple trips. This can cause the wedge face to deviate from the required azimuth.

It is well known in the art to use both hydraulic and mechanical

- 3 040552 locks. Examples of hydraulic locking mechanisms are described in the following documents: US 9347268; US 7789134; RU 2472913; EN 2473768; EN 2469172; CA 2446947; U5 5163522; US 8919431; US 7448446 and DE 4395361. Examples of mechanical locking mechanisms are described in documents such as GB 2309721, US 5829531, AU 66732786 and US 10006264. Documents US 2006/0207771 and US 7963341 describe anchorage made with the possibility of activation by mechanical or hydraulic means.

Traditionally, the design of the rock cutting tool with a rounded end facilitates the supply of fluid to the rock bolt mechanism through a narrow channel in the rock cutting tool. Examples of such structures are described in the following documents: ZA 199008719; EN 107820U1; US 2013/0319653; and ZA 198900656.

It is also well known in the art to use pivoting devices to further facilitate alignment of the wedge mechanism. Examples of rotary devices are described in the following documents: US 4303299; US 4285399; US 2002/144815; US 2506799; WO 95/07404; US 6167961; US 6035939; US 1570518 and GB 2315506. Examples of prior art leveling shoes are disclosed in documents such as WO 99/49178, US 2013299160 and US 2007/0175629.

In addition, the prior art also describes the use of sensors to determine the orientation of the wedge. Examples of their implementation are disclosed in documents such as WO 2014078028, WO 85/01983 and US 5488989. A known way to determine the orientation of the wedge is also the use of control points. Examples of their implementation are described in documents such as WO 2016/024867 and US 6427777. Logging tools, where the direction of the north magnetic pole is used as a reference, are described in documents US 5467819 and WO 95/23274.

In order to reduce the amount of tripping required to set up the wedge, Groupe Fordia Inc. developed what is called the one-shot wedge. As its name suggests, this wedge can be set in just one return pass of the drill string. However, the use of the single entry definition in the name is erroneous, as the drill string must be retrieved and replaced by the drill string, requiring at least one more trip before drilling behind the slip so that a lateral wellbore can be started. . Other examples of disposable wedges are described in WO 1995/023273, US 2015/122495 and GB 22480679.

Fordia's one-shot wedge uses a two-stage locking device located under the body of the wedge. The first stage or stage involves locking the body of the wedge at the desired depth in the lateral wellbore. The second step or stage involves fixing the edge of the wedge in the direction required for the sidetrack or along the required azimuth.

The wedge is suspended from the drill pipe string with the help of a device for lowering the wedge into the well. After reaching the required depth, the drill pipe string is rotated cyclically, rotating a device in the sidetrack to lower the wedge into the well. This rotation relative to the surrounding wall of the wellbore initiates the spreading of the anchoring legs by the threaded mechanism of the locking device, as a result of which these legs abut against the wall of the wellbore, providing locking of the first stage. Further rotation of the drill string causes the soft copper pin located between the wedge body and the locking device to be sheared, allowing the wedge body to rotate freely relative to the locking device, which is now stationary. This makes it possible to orient the wedge edge by further turning the drill string.

Upon completion of the orientation of the wedge face with its installation in the required position, the drill string is lowered down, pressing the axially interlocking parts of the locking device, which fixes the wedge face in the required orientation. Further lowering of the drill string causes the soft copper rivets that connect the wedge body to the tool to run the wedge into the hole shear off. This releases the wedge tool which is lifted back to the surface, positioned at the lower end of the drill string.

While the Fordia One-Shot Wedge is not difficult in theory, it can be unreliable in practice. A plurality of exposed interacting parts must function properly even under challenging downhole conditions. In addition, the system relies heavily on operators on the ground to ensure that the locking operations are complete and correct in each of the two stages described. At the same time, there is no proper feedback from the operators to monitor the progress in the implementation of operations and the successful completion of each stage.

There is also a risk of premature or incomplete actuation of the locking device on which the Fordia single-entry wedge rests. For example, it seems obvious that the locking device can be securely fixed in the main wellbore to prevent its rotation, but in reality it may not be properly secured to prevent its longitudinal displacement in the wellbore. In such a case, the wedge may slip into the well to a level below the required sidetracking point.

- 4 040552

Another problem, common to all prior art slips, is the risk that the thin upper edge of the wedge face will protrude beyond the wall of the main wellbore. Theoretically, this could lead to blocking of the trajectory of the core core drilling equipment, downhole motor drilling equipment and reaming equipment necessary to start creating a lateral wellbore and move forward after setting the wedge in the main wellbore.

Brief summary of the present invention

In this regard, the present invention provides a directional drilling method. This method involves driving a wedge from the drilling rig to a sidetracking point in the main wellbore while holding the wedge distal to the tubular drill string. The wedge is held by a substantially rigid connecting link passing through the annular rock cutting tool along the central longitudinal axis to connect the wedge to the drill string.

The wedge can be easily oriented to the required azimuth by rotating the drill string about the central longitudinal axis in order to transmit torque to the wedge through the connecting link. Then the wedge is fixed at the sidetracking point in the main wellbore along the required azimuth, after which the connection established by the connecting link between the drill string and the fixed wedge is broken, for example, by lifting the drill string in the proximal direction. The drill string may then be extended to drill a sidetrack wellbore extending from the main wellbore in an azimuth given by the wedge. The forward-moving drill string can widen the joint between the main bore and the lateral bore.

Accordingly, the idea of the present invention encompasses a system for directional drilling, which system includes: a tubular drill string with an annular rock cutting tool located at its distal end; a wedge located distal to the rock cutting tool, said wedge comprising a distal locking mechanism for fixing the wedge in the wellbore, attached to the wedge body, which defines an inclined edge of the wedge; and a substantially rigid connecting link that connects the wedge to the drill string, the connecting link extending through the rock cutting tool along the central longitudinal axis.

Preferably, the wedge is held in the drill string by a lowering mechanism. Thus, the connecting link can rigidly connect the wedge to the drill string through the lowering mechanism. In this case, the lowering mechanism can be lifted into the drilling rig after said connection is broken, for example, using a wireline hoist system moving in the drill string. After that, the lowering mechanism can be replaced by an internal core tube that extends in the drill string before the drill string is fed in to drill out the sidetrack.

The idea of the present invention also covers the main parts of the system, both individually and in combination, for example, a wedge to start creating a lateral wellbore during directional drilling. This wedge contains: a distal locking mechanism for fixing the wedge in the main wellbore; the proximal body of the wedge, which defines the inclined face of the wedge; and a substantially rigid connecting part which cooperates with the locking mechanism and which extends from the face of the wedge in the proximal direction along the central longitudinal axis.

Accordingly, the idea of the present invention encompasses a lowering mechanism holding a wedge for use in directional drilling. The lowering mechanism comprises: a latch for engagement of the lowering mechanism in the outer core pipe of the drill string; a substantially rigid connecting portion distally extending along a central longitudinal axis at the distal end of the lowering mechanism; and a rope catcher assembly at the proximal end of the lowering mechanism. The latch, connecting link and rope catcher assembly are interlocked with each other to prevent relative angular displacement relative to the central longitudinal axis.

After breaking the connection, at least part of the connecting link can be removed through the rock cutting tool. For example, when the connection is broken, the connecting link may be destroyed, but its distal part will remain embedded in the wedge. It should be noted that in the prior art rounded end design, it is not possible to extract part of the connecting link through the rock cutting tool, even if it is provided with a narrow channel for the passage of water. Instead, a round-ended rock cutting tool typically cuts off the remainder of the connecting link that protrudes from the face of the wedge.

Preferably, locking energy in the form of excess hydraulic pressure is supplied through the link to the wedge locking mechanism, which is usually done by diverting the drilling fluid through the link to lock the wedge. For example, the link may be in fluid communication with a relief valve that includes a valve element movable to drain drilling fluid along the link. In a preferred embodiment, the valve element is movable to divert the drilling fluid along

- 5 040552 connecting link on the fact that the drilling fluid exceeds the threshold pressure.

An equalizing force may be applied to the wedge, preferably when the wedge is locked, to rotate the wedge around the pivot axis perpendicular to the central longitudinal axis. Due to this force, the proximal edge of the wedge can be pressed against the surrounding wall of the main wellbore. To achieve this goal, the wedge may include anchor shoes and a leveling shoe located proximal to the anchor shoes on the same side of the wedge as the face of the wedge.

Thus, the wedge according to the present invention may also be provided as a wedge to start creating a lateral wellbore during directional drilling, the wedge comprising: a distal locking mechanism for locking the wedge in the main wellbore; and the proximal body of the wedge, which is characterized by the presence of an inclined edge of the wedge on one of its sides; the locking mechanism comprises outwardly displaceable locking shoes, including anchor shoes and a leveling shoe, wherein the leveling shoe is located proximal to the anchor shoes and is movable outward on the side of the wedge where the edge of the wedge is located.

A suitable directional wedge setting method includes: extending the wedge from the drilling rig to a sidetracking point in the wellbore; fixing the wedge at the sidetracking point and applying an equalizing force to the wedge to rotate the wedge around the rotation axis perpendicular to the central longitudinal axis of the wellbore prior to drilling behind the wedge.

An elegant solution has been proposed whereby a rope catcher assembly at the proximal end of the lowering mechanism, such as a four-jaw Christensen type latch mechanism, can be configured to function as an orientation receiver. Such an embodiment of a rope catcher assembly may comprise a key structure with a proximally tapered key. In such a case, the logging tool may be configured to engage with the line catcher assembly in an orientation given by said key structure.

The locking mechanism may include: a hydraulic cylinder in fluid communication with the connecting link; and a rod extending distally from the piston in the cylinder and extending to the wedge locking shoes. Said rod is preferably limited in unidirectional distal movement within the wedge, for example by passing through a ratchet system. This provides the advantage that the pawl of the ratchet system prevents movement of the locking shoes until the mud pressure exceeds a threshold value.

The concept of the present invention also encompasses a method for determining the azimuth of a wedge for use in directional drilling, the method comprising: driving the wedge into the wellbore to a sidetracking point at which the wellbore deviates from vertical; determination of the upper or lower part of the wellbore at the point of sidetracking, taking into account the force of attraction; search for the previously taken azimuth and inclination of the wellbore at the kickoff point; and determining the azimuth of the wedge relative to the previously acquired azimuth and inclination of the wellbore using the top or bottom of the wellbore as input, for example using gridded control data.

Therefore, in summary, in preparation for directional drilling, a wedge held distally in front of the tubular drill string is fed along the lateral wellbore. The wedge is connected to the drill string by means of a rigid connecting link that passes through the annular rock cutting tool along the central longitudinal axis. The wedge can be connected to the drill string through an internal lowering mechanism which can be gripped by a wireline hoist system.

After fixing the wedge at the kickoff point in the wellbore along the required azimuth, the connection of the connecting link is broken. The lowering mechanism can then be removed and replaced with an internal core pipe without moving the drill string. Then, to drill a sidetrack extending from the main wellbore along the azimuth determined by the wedge, the drill string is advanced. This provides the advantage that there is no need to remove the drill string before drilling the lateral wellbore.

In general, the prior art, for example, a round end rock cutting tool, does not allow core sampling without replacing the rock cutting tool with a core bit. This necessitates at least one additional tripping operation, which is a disadvantage.

Brief description of the figures

For the purpose of facilitating the understanding of the present invention, the following description will be given in conjunction, by way of example only, with the accompanying drawings, in which:

in fig. 1 is a schematic side view of a drilling rig running a wedge system according to the present invention into a main borehole;

- 6 040552 in FIG. 2 shows a schematic side view of the outer core tube of the drill string containing the lowering mechanism of the wedge system;

in fig. 3 is a schematic side view illustrating the outer core tube, which is cut away so that the lowering mechanism can be seen; as well as illustrating the wedge of the wedge system;

in fig. 4-12 are a series of schematic side views illustrating the wedge system in operation in a wellbore;

in fig. 13-15 are a selection of selected perspective views of the wedge;

in fig. 16-18 are a series of perspective views illustrating the operation of the wedge locking mechanism;

in fig. 19 is a longitudinal sectional view of the ratchet lock system assembly;

in fig. 20 is an enlarged perspective view in longitudinal section illustrating the actuation of the leveling shoe of the locking mechanism;

in fig. 21 is an enlarged perspective view in longitudinal section illustrating the actuation of the anchor shoes of the locking mechanism;

in fig. 22 is an exploded perspective view of parts of the lowering mechanism other than the connection tube;

in fig. 23 is an enlarged perspective view of the fishing pipe at the proximal end of the wedge;

in fig. 24 is an enlarged schematic longitudinal sectional side view illustrating a fishing pipe in a connecting pipe at the distal end of the lowering mechanism;

In FIG. 25 is a schematic side view illustrating a connecting tube extending from the distal end of the outer core tube;

In FIG. 26 is a schematic side view illustrating a connecting tube engaged with a wedge pipe at the proximal end of the wedge;

in fig. 27 is an enlarged exploded perspective view of the lowering mechanism relief valve;

in fig. 28 shows an enlarged perspective image of the junction of the external core pipe with the lock of the lowering mechanism;

in fig. 29 is a perspective view of the picker guide system in the form of a four-jaw latch mechanism included in the lowering mechanism; and in FIG. 30 is a perspective view of a logging tool comprising a beveled landing shoe that is configured to engage with a picker guide system in the form of a four-jaw latch shown in FIG. 29.

Detailed disclosure of embodiments of the present invention

In the following description, the lower, descending or downwardly directed end or direction is referred to as distal or distally directed. Conversely, the top, ascending or upward end or direction is referred to as the proximal or proximally directed. This reflects the fact that the present invention can be used in wellbores that, under certain circumstances, can be drilled horizontally or upwards, and not only downwards.

Wedge system overview

Referring first to FIG. 1 of the drawings, which shows a wedge system 10 according to the present invention, which is suspended from a drill string 12 in the main borehole 14 of the well. The drill string 12 extends distally from a conventional drilling rig 16 located on the surface of the earth and enters the wellbore 14 .

The wedge system 10 includes a wedge 18 hanging from the lowering mechanism 20 at the depth of the desired cutoff point. The lowering mechanism 20, in turn, is suspended from the drill string 12.

As shown also in FIG. 2 and 3, the lowering mechanism 20 extends telescopically into the outer core tube 22 at the distal end of the drill string 12. The length of the outer core tube 22 is typically 4 m.

The lowering mechanism 20 is removably located inside the outer core pipe 22 and is engaged with it.

The engaged lowering mechanism 20 can rise proximally, but cannot move distally relative to the outer core pipe 22. Accordingly, the outer core pipe 22 and the rest of the drill string 12 bear the weight of the lowering mechanism 20 and wedge 18.

Wedge 18 shown in FIG. 3 includes a locking mechanism 24 that connects to the distal end of a proximally tapering wedge body 26. Although the locking mechanism 24 is connected to the wedge body 26 during operation, it can be separated from the wedge body 26 before use to

- 7 040552 ease of maintenance and transportation. The body 26 of the wedge is characterized by the presence of an inclined edge of the wedge, which during operation will guide the drill string 12 into the sidetrack extending from the main borehole 14 of the well. Thus, when the locking mechanism 24 is activated, it engages with the surrounding wall of the wellbore 14 to immobilize the wedge 18 in the wellbore 14.

In the preferred embodiment of the present invention, which is described below, an elegant solution is implemented, according to which the locking mechanism 24 is activated by drilling fluid, preferably water-based, which is pumped into the drill string 12. This eliminates the need for a separate hydraulic actuating system.

In principle, other actuating systems, such as electric or pneumatic systems, can also be used to activate the locking mechanism 24. However, the use of a drilling fluid, such as a water-based one, is much preferred due to the ease and efficiency of its use. For example, despite the high hydrostatic pressure in the wellbore 14 at depth, a relatively small increase in the pressure of the aqueous solution created at the surface is sufficient to activate the locking mechanism 24 and set the wedge 18.

To supply the necessary excess hydraulic pressure, a rigid wedge pipe 30 on the central longitudinal axis 32 passes through the edge 28 of the wedge, providing fluid communication with the locking mechanism 24. The wedge pipe 30 conducts the flow of the aqueous solution along the drill string 12 to distally apply an activating pressure to the locking mechanism 24 through the face 28 of the wedge.

The wedge tube 30 is provided with an external thread at its proximal end onto which a clamp nut 34 is screwed. The clamp nut 34 allows the wedge tube 30 to be fluidly or mechanically connected to a lowering mechanism 20 at the proximal end of the wedge 18 as will be described below.

In FIG. 4-6 show the wedge system 10 suspended from the outer core pipe 22 of the drill string 12 at the sidetracking point in the main borehole 14. In particular, in FIG. 4 shows the wedge system 10 being lowered towards the kickoff point. In FIG. 5 shows a logging tool 36 being lowered into a wellbore for engagement with a lowering mechanism 20. FIG. 6 shows the logging tool 36 already engaged with the lowering mechanism 20 to determine its azimuth and, accordingly, the azimuth of the wedge face 38.

Typically, after engaging with the lowering mechanism 20, the logging tool 36 is raised to the surface so that the measured azimuth can be read. If the measured azimuth differs from the desired azimuth, then the lowering mechanism 20 and wedge 18 can be rotated by rotating the drill string 12 so as to obtain the desired azimuth.

However, to confirm that the desired azimuth has been obtained, it is recommended to re-lower the logging tool 36 into the wellbore to engage the lowering mechanism 20, and then raise the logging tool 36 back to the surface.

When turning the drill string 12, including the outer core pipe 22, around its longitudinal axis 32, as shown in FIG. 6, the outer core tube 22 may also apply torque to rotate the lowering mechanism 20 and thus rotate the wedge 18 in the wellbore 14. This ensures that face 28 of wedge body 26 is positioned so that its orientation matches the azimuth required for the lateral wellbore.

In FIG. 7 shows the locking mechanism 24 already activated to finally set the wedge 18 at the required depth and with the required azimuth orientation. During activation, the anchor shoes 38 and the leveling shoe 40 move sideways from the locking mechanism 24 to engage the surrounding wall of the wellbore 14 . The process of orienting the locking mechanism 24 will be described in detail below in connection with FIG. 16-21.

Further, as shown in FIG. 8, the drill string 12, including the outer core tube 22, extends the lowering mechanism 20 proximally, breaking the connection between the lowering mechanism 20 and the installed wedge 18, which remains in a fixed position in the wellbore 14. This is achieved by breaking the wedge pipe 30 at a predetermined sidetracking point, which will be described below.

The lowering mechanism 20 can then be disengaged from the outer core tube 22 to be subsequently lifted proximally by a cable hoist system 42 relative to the outer core tube 22, as shown in FIG. 9. This allows the lowering mechanism 20 to be pulled to the surface using a wire rope after the wedge 18 is finally set and the lowering mechanism 20 is separated from the wedge 18. The outer core tube 22 remains in the wellbore 14 at the distal end of the drill string 12, as shown in fig. 10.

The inner core tube 44 can then be lowered into the outer core tube 22 and telescopically inserted to replace the lowering mechanism 20 as shown in FIG. 11 using conventional core core drilling techniques. After that

- 8 040552 the drill string 12 is ready to start drilling behind the wedge 18 to create a sidetrack 46 of the well, as shown in FIG. 12.

As can be seen, the outer core pipe 22, with the rock cutting tool 48 located at its distal end, is lowered into the wellbore 14 along with the wedge 18 and the lowering mechanism 20, remaining in the installed position directly above the wedge 18 in the proximal direction. As a consequence, the drill string 12 is positioned ready to drill behind the wedge 18 after it has been installed in the wellbore 14 . It is important to note that this eliminates the need to spend time on an additional operation to rise to the surface and back before drilling the sidetrack 46 of the well.

This provides the advantage that the outer core tube 22 can be an expanding core tube. The expanding core pipe is surrounded by circular expanding inserts 50 spaced at a certain distance from the rock cutting tool in the longitudinal direction near its distal end. The reamer inserts 50 widen the intersection of the main borehole 14 with the lateral borehole 46, which eliminates the need for additional reamer equipment to be lowered into the hole and thus avoids another tripping operation on the drill string.

Wedge

Referring now to FIG. 13-15 showing the wedge 18 separately. FIG. 14 and 15 wedge 18 is shown in longitudinal section in mutually orthogonal planes.

The locking mechanism 24 of the wedge 18 is connected to and distal to the proximally tapering body 26 of the wedge.

Partially cylindrical curved-curved edge 28 of the wedge is given by the taper of the body 26 of the wedge. The edge 28 of the wedge is gently inclined with respect to the central longitudinal axis 32 and ends with a thin curved-curved proximal edge 52. The radius of curvature of the edge 28 of the wedge and its proximal edge 52 approaches the radius of curvature of the main bore 14 of the well, into which the wedge 18 must be inserted.

As can be seen, once the wedge 18 has been placed in the main wellbore 14, its central longitudinal axis 32 substantially coincides with the central longitudinal axis 32 of the main wellbore 14.

The distal portion 54 of the wedge tube 30, which extends into the locking mechanism 24, is embedded in the body 26 of the wedge on the distal side of the edge 26 of the wedge. Conversely, the proximal portion 56 of the wedge tube 30 remains open on the proximal side of the face 26 of the wedge.

The wedge pipe 30 is characterized by the presence of a line 58 of least resistance on the distal side of the edge 28 of the wedge in the distal portion 54 mounted in the body 26 of the wedge. For example, the wedge pipe 30 may be characterized by the presence of a wall section locally thinned by an annular recess. This line 58 of least resistance causes the wedge pipe 30 to break when the tension exceeds a threshold value. The necessary tension is applied to the wedge 30 by the hydraulic retracting mechanism of the drilling rig 16, which raises the drill string 12. The wedge is then split into two separate parts, as shown in FIG. 8.

After the fracture and separation of the wedge pipe 30 as described, the lowering mechanism 20 can be removed from the wellbore 14, as shown in FIG. 9. This operation provides that the portion of the wedge tube 30 on the proximal side of the fracture remains attached to the lowering mechanism 20.

The reverse side 60 of the body 26 of the wedge, opposite the face 28 of the wedge, is partially cylindrical. Therefore, the body 26 of the wedge can be considered as a cylinder from which an inclined partly cylindrical part has been cut, the concave curvature of this cut part defining the edge 28 of the wedge.

The locking mechanism 24 is characterized by the presence of a cylindrical body 62, the radius of curvature of which coincides with the radius of curvature of the partially cylindrical reverse side 60 of the body 26 of the wedge. This radius is chosen such that it provides an accurate sliding fit in the wellbore 14 . The body 62 is characterized by having a tapered, rounded or semi-circular distal end 64 to facilitate distal movement of the wedge 18 along the wellbore 14 to the depth of the kickoff point.

Described below is the actuation of the locking mechanism 24 as disclosed in connection with FIG. 16-21.

Near its distal end, the housing 62 is provided with four holes equidistant from each other in the circumferential direction, into which the respective anchor shoes 38 enter, forming a cruciform configuration. Anchor shoes 38 can be displaced radially outward relative to the central longitudinal axis 32 in mutually orthogonal radial planes.

When moving in a radially outward direction in the main borehole 14, the anchor shoes 38 abut against the surrounding wall of the borehole 14, fixing the wedge 18 at the desired sidetracking point, as also shown in FIG. 7-12. To do this, the anchor shoes 38 are equipped with teeth that engage with the wall of the borehole 14. Conveniently, the single locking operation also sets the wedge face 28 at the desired azimuth, i.e. the required orientation angle relative to the central longitudinal axis 32 coincides with the required azimuthal direction of the lateral wellbore 46 extending from the sidetracking point.

The body 62 is provided with an additional sideways opening proximally spaced from the anchor shoes 38 closer to the body 26 of the wedge. This additional hole receives a single radially movable alignment shoe 40, which moves radially outward in the wellbore 14 at the same time as the anchor shoes 38.

The task of the leveling shoe 40 is to rest against the surrounding wall of the shaft 14 so that the wedge 18 rotates slightly relative to the horizontal center of rotation given by the anchor shoes 38. The direction of rotation should be such that the proximal edge 52 of the face 28 of the wedge is pressed tightly against the borehole wall 14 as shown in FIG. 7-12. This will assist in inserting the proximal end 52 into the wall of the wellbore 14, preventing the proximal end 52 from blocking the distal movement of the outer core tube 22 during subsequent drilling operations to begin creating the sidetrack 46 of the well.

Thus, the leveling shoe 40 moves in a direction that faces the same side as the edge 28 of the wedge with respect to the central longitudinal axis 32. In other words, the leveling shoe 40 moves in the direction opposite to the partially cylindrical side of the body 26 of the wedge on the reverse side of the edge 28 wedge.

In this example, the alignment shoe 40 moves in the same radial plane as the opposing pair of anchor shoes 38 near the distal end of the body 62. However, the alignment shoe 40 is designed to move in a different radial plane, provided that it pushes the proximal edge 52 of the facet 28 wedge in the required direction.

The locking mechanism 24 of the wedge 18 includes a hydraulic cylinder 66 at the proximal end, which is in fluid communication with the distal end of the wedge tube 30. The hydraulic cylinder 66 is provided with a piston 68, which can move in the distal direction by applying hydraulic pressure to the cylinder 66 through the wedge tube 30. The distal movement of the piston 68 initiates the distal movement of the longitudinally extended rod 70 connected to the piston 68. The rod 70 is supported by bearings 72 in the housing 62, which allows it to slide distally along the housing 62.

In FIG. 19 shows that the proximal portion of the stem 70 passes through a non-returning ratchet 74 which only allows the stem 70 to move in a distal direction. To this end, the ratchet mechanism 74 includes a longitudinal row of inward-facing and inwardly offset teeth 76 that can engage with a longitudinal row of outward-facing teeth 78 on the proximal portion of the shaft 70.

The present invention provides the advantage that each tooth 76 of the ratchet contains a number of relatively thin and independently moving blades 80. This reduces the clearance between the stem 70 and the ratchet 74 in that even slight movement of the stem 70 will engage the next blade. 80 instead of necessarily covering the entire longitudinal distance from one tooth 76 to another.

As best seen in FIG. 20 and 21, the distal portion of stem 70 is characterized by distally tapering portions defining inclined curved surfaces 82 and 84 that mate with anchor shoes 38 and alignment shoe 40, respectively. Through these curved surfaces 82 and 84, distal movement of stem 70 initiates movement anchor shoes 38 and leveling shoe 40 radially outward while fixing the wedge 18 in the wellbore 14.

To ensure that premature or accidental actuation of the locking mechanism 24 is prevented, the stem 70 is secured with a safety pin 86 shown in FIG. 21, which perpendicularly enters the rod from one of the bearings 72 in the housing 62 covering it.

The safety pin 86 is sheared to release the stem 70 so that it can move distally only when a threshold pressure is applied to the stem 70 through the piston 68 in the cylinder 66.

Lowering mechanism

As shown schematically in FIG. 3, the lowering mechanism 20 is an elongated assembly sized to fit telescopically into the outer core tube 22. In proximal order, the lowering mechanism 20 comprises a hollow rigid connecting tube 88 at the distal end, a relief valve 90, a retainer 92, and a guide system. 94 pickers at the proximal end.

In FIG. 22 does not show the connecting tube 88, but shows the remaining parts of the lowering mechanism 10, namely the relief valve 90, the retainer 92 and the picker guide system 94. These parts are described in more detail below in connection with FIG. 27-29.

- 10 040552

In FIG. 22 also shows a sleeve 96 forming part of the outer core tube 22 that cooperates with the retainer 92, as will be described in conjunction with FIG. 28. The logging tool shown schematically in FIG. 5 and 6 is also shown in FIG. 22, but it will be described in more detail in connection with FIG. thirty.

When the wedge system 10 is assembled on the surface, the wedge 18 is held by the rig clamp 16 and the lowering mechanism 20 is raised above the proximal end of the wedge 18. The lowering mechanism 20 and the wedge 18 are angularly aligned with the vertical axis. A connecting pipe 88 is then butt-to-butt connected to the wedge pipe 30, providing fluid communication between the connecting pipe 88 and the wedge pipe 30 to activate the locking mechanism 24 of the wedge 18.

Optionally, as best seen in FIG. 23, the wedge pipe 30 of the wedge 18 terminates in and is in fluid communication with a narrower fishing pipe 98 that extends proximally from the wedge pipe 30 beyond the clamp nut 34. The distal end of the fishing pipe 98 is provided with an external thread that can be screwed into a counter an internal thread at the proximal end of the wedge pipe 30. The fishing pipe 98 has a blind distal end, but the wall of the fishing pipe 98 has a plurality of side holes 100 near the distal end.

As shown in FIG. 24, the fishing pipe 98 at the proximal end of the wedge pipe 30 proximally enters the connecting pipe 88 of the lowering mechanism 20. Accordingly, the fishing pipe 98 and the connecting pipe 88 surrounding it will be connected to each other in a telescopic manner, leaving a narrow annular gap 102 between them.

Water flowing from the drill string 12 along the connecting pipe 88 enters the fishing pipe 98 through the side openings 100 near the distal end of the fishing pipe 98. As the water passes, the sand and sediment entrained in the water tend to settle out of the water stream under the force of gravity. in the distal direction and, accordingly, in the annular gap 102 between the fishing pipe 98 and the connecting pipe 88, where solids are captured. This significantly reduces the amount of particles that water brings into the locking mechanism 24 through the fishing pipe 98 and wedge pipe 30, which contributes to improving its reliability.

Once the lowering mechanism 20 has been placed in the outer core tube 22, the connecting tube 88 will protrude distally about half a meter beyond the rock cutting tool at the distal end of the outer core tube 22, as shown in FIG. 25. This will facilitate butt connection of the connecting pipe 88 with the wedge pipe 30 while being held by the drilling rig 16. To do this, the distal end of the connecting pipe 88 is provided with an external thread that engages with the aforementioned clamp nut 34 at the proximal end of the wedge pipe 30, as shown. in fig. 26.

The clamp nut 34 connects the connecting pipe 88 with the wedge pipe 30 not only fluidly, but also mechanically. Thus, both the connecting pipe 88 and the slip pipe 30 connected thereto can bear the axial weight load of the slip 18 when the slip system 10 is suspended from the drill string 12 in the wellbore 14. The connecting pipe 88 and the wedge pipe 30 connected to it are also interlocked with each other to counteract the relative angular displacement. Therefore, the connecting pipe 88 and slip pipe 30 can also transmit torque to rotate the wedge 18 when the drill string 12 and lowering mechanism 20 are rotated together in the wellbore 14 .

The picker guide system 94 is preferably hinged to the latch 92 so that the picker guide system 94 can rotate relative to the remainder of the otherwise rigid lowering mechanism 20. This facilitates lifting of the lowering mechanism 20 from a horizontal position on the surface to a vertical position on the rig. installation 16 for its introduction into the wellbore 14. However, all parts of the lowering mechanism 20 are interlocked with each other to resist relative angular displacement about its central longitudinal axis.

It follows that when in the wellbore 14, the angular orientation of the connecting tube 88 at the distal end of the lowering mechanism 20 must always follow the angular orientation of the picker guide system 94 at the proximal end of the lowering mechanism 20. Therefore, determining the angular orientation of the picker guide system 94 in wellbore 14 determines the angular orientation of the connecting pipe 88 in the wellbore 14 .

Further, since the connecting pipe 88 and the wedge pipe 30 connected thereto are engaged with each other to resist relative angular displacement, the angular orientation of the wedge 18 must always follow the angular orientation of the picker guide system 94 at the proximal end of the lowering mechanism 20. Accordingly, the determination of the angular orientation guide system 94 of the picker in the wellbore 14, which will be described below, determines the angular orientation of the wedge 18, which is fixed in an angular position with a known

- 11 040552 orientation relative to the connecting pipe 88. Therefore, this determines the azimuthal alignment of the edge 28 of the wedge in the borehole 14 of the well.

The proximal end of the connecting tube 88 is in fluid communication with a relief valve 90, shown separately in FIG. 27. Relief valve 90 equalizes the pressure of the aqueous solution inside and outside the drill string 12, allowing, in normal operation, the aqueous solution from the drill string 12 to pass through the lowering mechanism 20 in the outer core pipe 22 and flow around it with this aqueous solution.

Relief valve 90 includes a proximally biased pusher 104 that can counteract the bias of spring 106 by moving distally. The aqueous solution flowing distally down the drill string 12 passes through the central hole 108 of the pusher 104.

When the pusher 104 is in its normal proximal position, a portion of the aqueous solution passing through its central hole 108 exits through the holes 110 in the surrounding tubular wall of the relief valve 90. However, when the pressure of the aqueous solution pumped into the drill string 12 at the surface increases, the pusher 104 overcomes the compressive force of the spring by moving distally. This pusher 104 blocks holes 110, whereby substantially all of the flow of high pressure aqueous solution is directed into the connecting pipe 88, bypassing the relief valve 90. The high pressure aqueous solution discharged by the relief valve 90 is directed through the connecting pipe 88 to the wedge pipe 30, activating after its passage the locking mechanism 24 of the wedge 18 as described above.

The latch 92 at the proximal end of the relief valve 90 is illustrated in this case by a Boart Longyear latch-type locking inner tube 92, an enlarged view of which is shown in FIG. 28. The picker guide system 94 is illustrated here with a specially modified Christensen-type four-cam latch mechanism 94, an enlarged view of which is shown in FIG. 29. Both of these trademarks are used by the drilling industry to describe their respective products and have therefore become household names. Both of these pieces of equipment are individually familiar to those skilled in the art and therefore need not be further described here.

In preferred embodiments of the present invention, a Christensen-type four-jaw latch mechanism 94 is used to replace the proximally facing spear-end lifter of the Boart Longyear locking device 92. Thus, the use of a Christensen-type four-jaw latch mechanism 94 in combination with a Boart Longyear-type locking device 92 is a novel and advantageous aspect of the claimed invention. Therefore, according to the present invention, well-known equipment, compatible with existing drilling equipment, can be used in an innovative and beneficial manner.

The Boart Longyear latch latch 92 includes diametrically opposed retractable latch bolts 112, one of which is shown in FIG. 28. When lowering mechanism 20 is engaged with outer core tube 22 enclosing it during descent, latch latches 112 are longitudinally aligned with inner lug 114 on sleeve 96 of outer core tube 22. Latch lug 114 is also illustrated in FIG. 28.

After the lowering mechanism 20 is finally installed in the outer core tube 22, the latch latches 112 will protrude radially away from the tube. As a result, it is possible to engage the shoulder in the outer core pipe 22 to fix the lowering mechanism 20 in the axial direction in order to prevent its proximal displacement relative to the outer core pipe 22. position relative to the outer core pipe 22 and, respectively, relative to the drill string 12, from which the outer core pipe 22 is suspended. lowering mechanism 20 in the wellbore 14 .

When the four-jaw latch mechanism 94 is engaged by the rope hoist 42, as shown in FIG. 9, in order to retrieve the lowering mechanism 20 after the wedge 18 has reached its final position, the lifting system 42 bears the weight of the lowering mechanism 20. external core pipe 22 and removed to the surface. Thereafter, the standard inner core tube 44, which may be fitted with, for example, its own Boart Longyear latch lock, may be lowered to engage with the outer core.

- 12 040552 core pipe 22, as shown in Fig. 11, which makes it possible to start core drilling with a removable core receiver.

Four-jaw Christensen-type latch mechanisms are disclosed, for example, in US Pat. extracting the inner core pipe from the outer core pipe 22.

To accomplish the objectives of the present invention, the four-jaw latch mechanism 94 is secured not to the inner core tube, but to the remainder of the lowering mechanism 20 through the latch 92. In addition, the four-jaw latch mechanism 94 serves two functions. Its main function is to allow the azimuthal orientation of the lowering mechanism 20 and, accordingly, the face 28 of the wedge connected to the lowering mechanism 20 to be captured before the wedge 18 reaches its final position in the wellbore. Its second function is to allow the lowering mechanism 20 to be retrieved to the surface using the cable hoist system 42 after the wedge 18 has taken its final position in the wellbore. This second function corresponds to its normal function of extracting the inner core tube from the outer core tube 22, which is known to those skilled in the art, and therefore does not require further description here.

In order to perform its primary function of enabling surveying, the four-cam latch mechanism 94 of the present invention has been modified so that it can be coupled to a logging tool 36, schematically shown in FIG. 5 and 6 and an enlarged view in Figs. 30. The logging tool 36 is also configured to engage with a four-jaw latch mechanism 94. To this end, the four-jaw latch mechanism 94 and the logging tool 36 are provided with mating interlocking structures, which will be described below.

The logging tool 36 can be lowered into the drill string 12 on a wireline extended from the surface to a four-jaw latch mechanism 94, with which the logging tool 36 subsequently engages. An accurate azimuth determination requires that the logging tool 36 engage the four-jaw latch 94 in only one angular position relative to the four-jaw latch 94. In addition, it is an advantage that the logging tool 36 can assume such an angular position automatically during its engagement with the four-jaw latch mechanism 94.

In particular, a beveled landing shoe 118 of the logging tool 36 is provided for this purpose, protruding distally between four proximally extended cams 116 of a four-cam latch mechanism 94. The beveled landing shoe 118 is a distally elongated tube with an obliquely cut end to form a distally inclined end 120. From the proximal end of the end face 120 extends proximally the groove 122. In the groove 122 is the sensor 124 clamping.

Accordingly, in FIG. 29 shows that to the inside of one of the four cams 116 of the four cam latch mechanism 94 is added a key structure 126 with a proximally tapering inward-facing key. The shape and orientation of the key structure 126 allows it to fit into the slot 122 of the beveled landing shoe 118 while correctly aligning the logging tool 36 with the four-jaw latch mechanism 94. Thus, the key structure 126 modifies the four-jaw latch mechanism 94 into an integral orientation receiver.

Proper angular alignment of the logging tool 36 relative to the four-jaw latch mechanism 94 is provided by the inclined distal end 120 of the beveled landing shoe 118. The inclination of the distal end 120 interacts with the proximal taper of the key structure 126 so that the logging tool 36 rotates about the longitudinal axis 32 as the beveled landing shoe 118 moves distally.

This rotation of the logging tool 36 aligns the slot 122 with the key structure 126 as the bevelled landing shoe 118 slides distally along the key structure 126, passing between the enclosing cams 116. The clamp sensor 124 then confirms that the key structure 126 has entered the groove 124.

Optionally, to provide angular alignment between the logging tool 36 and the four-jaw latch mechanism 94, and to confirm that the logging tool 36 is properly engaged with the key structure 126 of the four-jaw latch mechanism 94, a distally facing camera provided in the logging tool will help. tool 36.

-

Claims (12)

Even with a slight deviation of the main wellbore 14 from the vertical, which is common in practice, even in a nominally vertical wellbore, the logging tool 36 can determine the azimuth of the wedge 18 and, accordingly, the lateral wellbore 46 of the well gravitationally in relation to the upper part and / or lower part wellbore 14. This is possible due to the fact that the local inclination and azimuth of the main borehole 14 at the depth of the sidetracking point is already known from a detailed survey of the borehole 14, which is normally carried out in advance. The top and/or bottom of the wellbore 14 can be determined by rotating the drill string 12 to rotate the lowering mechanism 20 about its longitudinal axis 32 in the wellbore 14. This will also change the orientation of the logging tool engaged with the four cam latch mechanism 94. Once the top and/or bottom of the wellbore 14 has been determined, a landmark or data point can be established for using gridded or GR positioning methods. This has the advantage of eliminating the need for non-magnetic drill pipes, which are very expensive and usually cannot be used in a drill string due to the excessive softness of the material from which they are made. However, in principle, the logging tool 38 may determine the bearing by other means, such as gyroscopic or magnetic, using the direction of the north magnetic pole as a reference. Slight deviations of the lateral wellbore 46 from the required angle of inclination and azimuth can be corrected at a subsequent stage of drilling with a downhole motor after completion of the initial core drilling with a removable core tube behind the wedge 18. A variety of changes can be made to the idea of the present invention. For example, a rigid connecting link containing a wedge pipe and a connecting pipe does not have to break or rise in the proximal direction to break. The component parts of the rigid connecting link can be separated from each other in other ways, for example by activating the release mechanism or by twisting the wedge pipe beyond the angular limit or screwing into a left-hand thread. CLAIM 1. Directional drilling method, and this method involves: supplying a wedge from the drilling rig to the sidetracking point in the main wellbore while holding the wedge distally relative to the tubular drill string using a substantially rigid connecting link passing through the annular rock cutting tool along the central longitudinal axis for connecting the wedge with the drill string; fixing the wedge at the kickoff point in the main wellbore according to the required azimuth; breaking the connection between the drill string and the fixed wedge, which is provided by the specified connecting link; extracting at least part of the connecting link through the rock cutting tool after breaking said connection; and extending the drill string to drill out a lateral wellbore extending from the main wellbore along an azimuth given by the wedge without pulling out the drill string. 2. The method according to claim 1, which involves orienting the wedge along the required azimuth by turning the drill string about the central longitudinal axis to apply torque to the wedge through the connecting link. 3. The method according to claim 1 or 2, providing for the removal of the connecting link to break the connection, in which the distal part of the connecting link remains embedded in the wedge. 4. A method according to any one of the preceding claims, comprising holding the wedge in the drill string by means of a lowering mechanism. 5. The method according to claim 4, providing for the removal of the lowering mechanism on the drilling rig after breaking the connection. 6. The method of claim 5, comprising engaging the lowering mechanism with a wireline hoist system that extends inside the drill string. 7. A method according to any one of the preceding claims 4 to 6, comprising replacing the lowering mechanism with an internal core pipe that extends inside the drill string prior to extending the drill string to drill out a lateral wellbore. 8. Method according to any one of the preceding claims, carried out without dismantling the drill string. 9. A method according to any one of the preceding claims, comprising transferring the locking energy to the wedge through the connecting link. 10. The method according to claim 9, which involves fixing the wedge by applying hydraulic pressure through the connecting link. 11. The method according to claim 9 or 10, which involves diverting the drilling fluid through the connecting link to fix the wedge. 12. The method according to claim 11, providing for the diversion of the drilling fluid by creating pressure, -