A METHOD AND ARRANGEMENT FOR CONNECTING DRILL PIPES/DRILL PIPE STANDS
This invention regards a method for connecting drill pipes and of the type specified in the preamble of Claim 1, to which reference is herewith made.
Likewise, the invention regards an arrangement for use in connecting two drill pipe stands of a standard length, which arrangement is of the type specified in the preamble of the independent Claim 5.
The connecting of drill pipes in accordance with the present invention with which the below description is concerned, is a joining of drill pipes/drill pipe stands to form pipe lengths/stands that are twice (or three/four times) as long, which joining precedes and is completely independent of the screwing together of drill pipes that follows naturally from the successive build-up of the drill string when this is extended as the drilling depth increases, and which is carried out with the drill pipe length that is at hand. As will be apparent from the following description, it will upon
the drill string being extended successively with increasing drilling depth, be an obvious advantage to be able to use drill pipe stands of as long a length as may be handled onboard e.g. a standard offshore platform with a rig structure and derrick included therein, with no particular problems .
The joining of drill pipes to form compound drill pipe stands of a doubled, tripled etc. axial longitudinal extent will by the invention take place in pipe connecting operations that occur prior to (concurrently with) and independently of drilling/drill string extensions. In this pipe connecting operation, compound pipes of a length from which it is desired that the drill string be made up are prepared, and until that time stored in a position where they are ready to be transferred and screwed onto a drill string that is in operation and is in a state of being assembled/extended. Thus the preparation of these drill string stands consisting of compound drill pipes is completely independent of drilling/drill string extensions.
When drilling a well in connection with oil and/or gas production, a string of compound drill pipes has normally been used in order to drive a rotatable drill bit mounted at the outer end of the drill string. A drill string of a known, common type is through screwing assembled from approximately ten metre long drill pipes, which may be called "standard" drill pipes.
As the drill bit works its way down into the ground and the bore hole length increases, the drill string is each time extended by adding a new drill string stand to the upper end of the drill string.
An obvious disadvantage of joining drill pipes to form a drill string during drilling is that each time a new drill pipe/drill pipe stand is to be screwed onto the upper end of the drill string, the ongoing drilling operation must be interrupted. Naturally, such interruptions in drilling on connecting new drill pipes/drill pipe stands will reduce the drilling efficiency, and it is common knowledge among those skilled in the art that if each drill pipe stand was twice the length, i.e. around 20 metres, the number of drilling o interruptions would be halved.
Traditionally however, it has not been practical to use drill pipe stands that are any longer than these standard drill pipes of 10 metres each, as it has been necessary to join a hexagonal or octagonal kelly to the top of the drill string s in order to impart torque to the drill string and thereby the drill bit, for the purpose of rotation.
However this kelly had to be detached every time a new drill pipe or a new drill pipe stand were to be joined to the drill string in order to extend this, in order then to fit the o kelly to the upper portion of the extended drill string, following the connection of said new drill pipe/pipe stand to the upper free end of the drill string temporarily freed of the kelly.
Such kellys with a polygonal cross-sectional circumference 5 must be of the same length as each of the drill pipes/drill pipe stands from which the drill string is successively assembled for the purpose of extension. Consequently, if this drill pipe length were to be given a general increase from ten to twenty metres, the kelly length would have to be given o a corresponding increase in length.
In the case of twenty metre long drill pipe stands, the total pipe length to be handled in the derrick, i.e. one such drill pipe stand plus a corresponding kelly, would be forty metres. In practice however, compound pipe stands of this length are difficult to handle. Besides, the handling of approximately ten metre long drill pipe stands represents a well established practice when it comes to drilling with a drill string that is assembled successively by means of drill pipe stands added from above one by one. Drill pipe stands with a longitudinal dimension that significantly exceeds approximately ten metres are also difficult to transport, lift and handle.
When using a top drive in the derrick, with no requirement for said kelly, extending the drill string by one "standard", approximately ten metre long drill pipe/drill pipe stand at a time does not make efficient use of the capacity of a normal derrick. On the other hand, assembling normal service stands in pairs in situ (on the drilling platform) to form double drill pipe stands will halve the time lost during each interruption of the drilling operation, i.e. during the connecting of a new drill pipe stand at the top of the drill string, while allowing work such as transport and other operations to be carried out with normal drill pipe stands .
The advantages of using long drill pipe stands for assembly of a drill string have long been known. Thus it has been common practice to divide the drill string into three very long drill pipe stands when the drill string is to be pulled out of the borehole, e.g. to change the drill bit. By disassembling a 30 metre long drill pipe stand comprising three connected, normal (standard) stands during each drill string shortening operation, the number of disassembly
operations is reduced to a third, and such so-called triple stands are easily handled in a normal derrick.
From US patent publication no. 4 850 439 there is known a method and a drilling platform with a rig for drilling of a well. This patent publication concerns equipment for preparation of long drill pipe stands at a preparation port formed through the drill floor at a distance from the drilling centre, concurrently with but independently of the drilling, so as to achieve said time savings. While drilling is carried out, standard drill pipe stands are connected, e.g. two at a time, to form double drill pipe stands that are set aside in the derrick until they are required. Subsequently, each time the drill string is to be extended, a pre-prepared double drill pipe stand is added to the top of the drill string. As a normal derrick such as mentioned above is constructed and dimensioned to handle said triple drill pipe stands, further savings on time may be achieved by pre- preparing such drill pipe stands as comprise three joined-up standard drill pipe stands.
The preparation of these double or triple drill pipe stands is in accordance with this US patent publication effected by a first standard drill pipe stand being introduced into a tubular well that communicates with above-mentioned preparation port in the drill floor, and suspended there. A second standard drill pipe stand is then joined to the top of the first drill pipe stand. If drill pipe stands corresponding to double standard drill pipe stands are used with this known connecting method, the prepared double drill pipe stand is pulled out of the tubular well and set aside on the drill floor, ready to be joined to the top of the drill string as soon as there is a requirement for this to be
extended, while a new first standard pipe stand is lowered through the preparation or joining port by means of a separate elevator provided in the top of the derrick, and suspended at this port, which is horizontally spaced from the mouse hole.
This known method of joining drill pipes is obviously inspired by the well established connecting of drill pipes that takes place when a new, from above descending drill pipe stand is joined with the top of an operating drill string, thus extending this. Screwing equipment for adjacent pipe ends may when joining two, three or possibly more standard drill pipe stands for pre-drilling preparation of long drill pipe stands, employ the same or similar well established equipment for drill string assembly from drill floor level.
If a triple or greater length of drill pipe stand is to be prepared according to the known method of joining drill pipes, the upper of the two joined drill pipe stands is disconnected, and together these are lowered further into the annular well, so as to allow a new, third drill pipe stand to be added to the top of the upper drill pipe. When the desired length has been attained, the compound pipe stand is pulled up from the annular well and set aside on the drill floor, preferably at a temporary storage station near the mouse hole and the drill string that is under successive extension.
Thus by this known solution to the problem caused by frequent interruptions in the drilling operation during the extension of a drill string by intermittent connecting of drill pipe stands to the top of the drill string one by one, and where the solution entails a reduction of the frequency of interruptions in the drilling operation relative to a given
additional length of drill string, significant savings on time and labour are achieved.
Still there is a major disadvantage associated with the solution according to US 4 850 439, that is the necessity of lowering at least the first standard drill pipe stand down through said preparation port to a position underneath the drill floor, as this lowering of a drill pipe at a horizontal distance from the drill string creates a need to move other equipment located in the same place (within the lowering area) underneath the drill floor.
Thus the object of the present invention has been to provide a method and an apparatus/arrangement wherein said disadvantage is avoided while maintaining the general advantages of the known solution, i.e. especially the time savings achieved by using long, pre-prepared drill pipe stands when drilling with a drill string by successive extension by means of such long drill pipe stands, e.g. corresponding to two or three times the length of a "standard" drill pipe stand (approximately 10 metres).
In order to realise this object an approach in accordance with the operational steps stated in the characterising part of Claim 1 is proposed, based on a method of the type given in the preamble of Claim 1. Advantageous, though not critical steps of the method appear from the additional characteristics stated in Claims 2-4.
A rationally operating arrangement that for one thing is suited for expedient implementation of this method and which may also result in other, related advantages, distinguishes i + oαl f V tr ι-<πτrιT->ι Λ+- i on e; nf rnn q rnn-H i nna l de a i ls that a re i n
accordance with Claim 5. Claim 6 provides practical, but relative to Claim 5 secondary constructional details.
In accordance with the present invention, a drill pipe stand that, relative to a traditional drill pipe stand, is extended to at least twice the length of said traditional drill pipe stand (about 10 metres), is prepared by guiding a first standard drill pipe stand to the drill floor and then to a vertically oriented position, whereupon this drill pipe stand is lifted until its lower end is located at a distance above the drill floor corresponding to or exceeding the length of one standard drill pipe stand.
By the method according to the invention, a second standard drill pipe stand is then guided into abutment against the drill floor at a point of projection from the overlying drill pipe stand suspended in a vertical position, and then into a vertical position, finally to be raised slightly in order for its upper connecting end (having a female thread socket or a male thread end pin) to engage with the lower connecting end, so as to allow joining of adjacent pipe stand ends to be carried out through screwing, in a manner that is known per se.
This screwing operation will, with a little tolerance, take place in one and the same spatial location, that is with its vertical and horizontal positions determined by the position of the end of said lower drill pipe stand.
Thus it is easy to place a fixed (possibly with a certain elevational and lateral adjustability) motorised pipe connector of a type that is known per se up in the derrick, namely at a level corresponding to or slightly exceeding a
standard drill pipe stand (approximately 10 metres), and projecting sideways so as to leave the operative parts of the connector in the area that encircles the projection of said lower end.
The handling of pipe stands on the drill floor and hoisting of one drill pipe stand in the derrick is carried out using a relatively simple arrangement comprising safely operating devices and means with simple displacement paths and opening and closing movements.
A vertical rail may be provided in the derrick for a plurality of upward and downward motorised carriages (elevators, slides), each of which is equipped with gripping means designed to releasably grip a (standard) drill pipe stand that has been brought to a vertically oriented position, resting on the drill floor by its lower end.
Preferably, said gripping means, which in the simplest form consist of a pair of mutually swivelling or otherwise reciprocally moveable gripping means in the form of e.g. clamps, are designed to grip such a vertical drill pipe stand in a manner such that the grip resists forces arising from the weight of the drill pipe stand upon it being lifted off the drill floor and into a freely suspended position.
A high-up pipe connector (e.g. at a level located approximately 12-14 metres above the drill floor) in the derrick represents significant technical advantages compared with prior art, as the inventive positioning of the pipe connector that is known per se, frees up space on the drill floor itself.
Details of an arrangement designed with a view to facilitating rational implementation of the method according to the invention appear from the dependent subclaims associated with the first apparatus claim, and from the following specifying part of the description.
The following explains the invention in connection with an embodiment example with reference to the accompanying drawings, in which:
Figure 1 is a schematic view of a common, fixed vertical travelling way constructed for upward and downward travelling carriages, which travelling way is formed by a truss rail that in practice will be constructed in connection with the schematically indicated derrick and supported relative to this, a pipe connector on a platform at a distance above the drill floor being made to assume an active (extended) operating position relative to a first drill pipe stand raised to-the connecting position, which pipe stand is to be connected to an identical, second underlying drill pipe stand here positioned in an intermediate, oblique position on its way up to be pulled up to said connecting position for connecting with the above, vertically suspended first drill pipe stand by means of threaded end portions that engage when in the connecting position; these standard drill pipes/drill pipe stands being taken one by one from a pipe rack for horizontal storage of these pipes, which rack is located just above the drill floor in the immediate vicinity of the derrick, and which is known per se;
Figure 2 is a schematic side view of the arrangement of Figure 1, but with the pipe connector shown in a retracted, inactive standby position and the pipe hoisting carriages
shown without a pipe stand (the vertical axis A indicates the joint pipe orientation axis upon connection/screwing together; axis B indicates the longitudinal axis of symmetry of the derrick);
Figure 3 is an analogous view, but here the pipe connector has been made to move horizontally into the area of the end connection means of the vertical coaxial drill pipe stands in order to join these; and
Figure 4 is an analogous view, but here a long, joint pipe comprising two pipe stands has been left suspended from an upper carriage that by means of an articulation has helped move this long, joint pipe some distance away from the vertical truss rail, while the lower carriage has released the long pipe that has been taken over by a pipe handling device having an upper and a lower gripping/holding and carrying means for pipes assembled from at least two pipe stands; which pipe handling device is of a type that is known per se.
In the drawings, reference number 1 denotes a vertical truss rail that is supported on a drilling floor 2 and also on a derrick 16 and is constructed with a common travelling way for a first, upper carriage 3 and a second, lower carriage 4, both of which are designed to be made to travel upwards or downwards along the travelling way of rail 1.
Each carriage 3, 4 is associated with a winch 5, 6 connected via wires 7, 8 to separate carriages 3, 4, so that each carriage 3, 4 may independently of the other carriage be run up along the rail 1 and lowered along the same.
By the upper end of the truss rail 1 are two freely rotatably supported pulleys 9 and 10 with a common rotational axis, one for the passage of each wire 7, 8 over the top of the rail, so that one pulley 9 hides the other pulley 10 in the side 5 views shown.
A relatively small cantilever platform 11 laterally oriented relative to the rail 1 is mounted at a certain distance, e.g. 10-12 metres, above the drill floor 2. The platform 11 supports a pipe connector 12 that is known per se, which may o in a known manner be moved horizontally between an operating position, Figs. 1 and 3, and an inactive standby position, Fig. 2.
A first standard drill pipe stand 13 (approximately 10 metres ) , located for instance in a horizontal storage s position on the drill floor 2 near the truss rail 1 and the derrick 16, e.g. in a carriage or a fixed rack such as indicated in Figure 1, is by its upper end-to-be brought into engagement with the releasable pipe end gripping means 3a of the first, upper carriage 3 in a manner not shown in any o greater detail (e.g. by means of a special hoisting/lifting arrangement), which pipe end gripping means are coupled to the actual carriage member via an articulation with a horizontal axis.
This carriage 3 is designed to be run/hoisted up and thus be 5 lifted along the rail 1 by means of the winch 5 via the wire 7 until the first drill pipe stand 13 has been brought to a vertical position suspended from the gripping means 3a of the carriage 3 and is then pulled straight up until its lower end is positioned at the working level of the pipe connector 12, o Fig. 3, ready by means of the pipe connector to be screwed
together with the other drill pipe stand 14 brought in from below (via carriage 4), the one upper end-to-be of which is correspondingly brought into temporary engagement with the releasable gripping means 4a of the lower carriage 4.
Said second drill pipe stand 14, which at one end is releasably attached to the gripping means 4a of said lower carriage 4, is via wire 8 lifted with the carriage by means of said second winch 6; first during the swing of the drill pipe stand 14 from an assumed horizontal storage position at drill floor level to a vertical position, and then by a linear lifting motion, clear of the drill floor 2, up into the connection area for the ends of the coaxially suspended drill pipe stands 13, 14 (Fig. 3), with said ends positioned at the working level of the pipe connector 12.
When the joining operation through screwing has been carried out by means of the pipe connector 12, the compound drill pipe stand in question has achieved a length of approximately 20 metres, which corresponds to the double length of a "standard" drill pipe length.
If it is desirable to work with even longer compound drill pipe stands, e.g. with an individual length of 30 or 40 metres, the compound drill pipe stand is hoisted further up along the common travelling way of the carriages 3, 4 along the rail 1, each time corresponding to one standard drill pipe stand, one single drill pipe stand at a time being added from below. The truss rail and the travelling ways of the carriages 3, 4 along it will then have a greater height than that shown in Figs. 1-4, adapted to the intended final length of pipe stand.
It is assumed that these long, compound drill pipe stands (generally a double or triple construction relative to the standard length) are prepared at an appropriate time before being put in for successive drill string extension during drilling.. This preparation may be carried out prior to and/or during drilling.
Before the individual, prepared compound drill pipe stands (for instance 13 + 14) are to be connected one by one to the top of the operating drill string (not shown), it is expedient to store them, preferably in a space-saving upright position near the through drill floor hole for the drill string. It is assumed that for this purpose, i.e. the associated handling operations both prior and subsequent to the hoisting and connecting operation of the drill pipe stands in the trussed structure, it may be carried out by means of ordinary pipe handling devices 15, e.g.. of the type shown in Figure 4, and which may be connected to the derrick 16 or be more or less free running on the drill floor 2. Such pipe handling equipment 15 may if required be modified with regards to size, in order to allow easier and safer handling of the long, compound drill pipe stands. A pipe handling device 15 of the type shown comprises a mandrel construction with an upper gripping device 15b having pipe gripping means 15b' and a lower/intermediate gripping device 15a having pipe gripping means 15a' . The upper gripping means may include telescopic tube means, while the lower/intermediate gripping device 15a comprises an articulated arm mechanism and at least one piston cylinder, Fig. 4.
In order for the shown, known pipe handling device 15, which should not require any special explanation, to be able to pull the compound pipe stand 13,14, having a length of
approximately 20 metres, straight out so as to leave it vertical at all times and thus displace it parallel to this orientation, the gripping means 3a of the upper carriage 3 may be connected to the actual carriage member via an articulated stay 3b, the ends of which are hinged to gripping means 3a and carriage member 3, see Fig. 4.
The pipe rack 18 in Fig. 1 may be replaced by another storage arrangement for drill pipes (13 and 14). The pipe rack 18 shown with drill pipes/drill pipe stands stored in a horizontal, laid down position is of a known type, and hence should not require any special explanation.
An apparatus/arrangement according to the present invention may be subjected to modifications in the details of the components, thus the construction of the carriages 3, 4 and their moving grippers and associated guides, and controls, centring elements, securing and locking mechanism, as well as releasing means. If the (standard) drill pipe stand end couplings (sockets/pins) that are to be joined/screwed together are fixed and form part of the individual drill pipes, said grippers and adjacent, possibly co-operating parts/portions will be forced to allow one drill pipe stand to be rotated while being retained and supported by such a gripper. Such a device may presumably be realised in several different ways.