GB2085055A

GB2085055A - Crank Connectors for Directional Drilling

Info

Publication number: GB2085055A
Application number: GB8130840A
Authority: GB
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1980-10-13
Filing date: 1981-10-13
Publication date: 1982-04-21
Also published as: JPS6337239B2; DE3140646C2; DE3140646A1; FR2491989B2; CA1177055A; FR2491989A2; NL192002B; JPS57100290A; NL8104632A; GB2085055B; NL192002C

Abstract

A crank connector for directional drilling whose angle can be varied by remote control, comprises two tubular members (1,2) interconnected by a rotary fitting (2a) which forms an axis ( DELTA ) of rotation different from the respective axes of the two members (1, 2) and is traversed by a shaft (20) slidable in both the tubular members (1, 2) while being constrained to rotate with a first of these members. The shaft (20) has a locking position in which it also becomes rotatably secured to the second member. A remotely controlled axial displacement of the shaft (20) from its locking position is transformed into a rotation of the second tubular member about the axis ( DELTA ) of rotation of the rotary fitting (2a). Auxiliary locking means comprising radially retractable locking fingers (100) prevents any undesired relative rotation of the two tubular members (1,2) when the shaft (20) is rotatably disengaged from the second tubular member. <IMAGE>

Description

SPECIFICATION Crank Connectors for Directional Drilling The present invention relates to devices of the type generally known as crank connectors for directional drilling and which may be positioned between a drill string and a downhole motor rotating a drill bit and permit adjustment of the orientation of the drilling path.

Various methods and devices have been proposed for carrying out directional drilling.

According to U.S. Patent No. 3 365 007, the action of a suitably directed fluid jet is used for locally destroying ground formations so as to create a recess into which a drill bit will be diverted. An obvious disadvantage of such a device is its lack of accuracy because the action of the fluid jet and, thus, the resulting bit deflection, will be substantially dependent on the hardness of the geological formations. Another disadvantage is that it becomes necessary to use a specially designed drill bit provided with a nozzle for discharging the fluid jet.

Another method, described for example in UK Patent No. 139 908, U.S. Patents Nos.

'3593810,3888319and4040494andin French Patent No. 2 297 989, uses a deflecting device surrounding the lower part of a section of a drill string, usually in the vicinity of the drill bit. The deflecting device is provided with a plurality of fingers which are radially displaceable with respect to the drill string axis. By suitably displacing these fingers so that they bear on the wall of the drill borehole, it becomes possible to offset the drill bit axis with respect to the borehole axis, thereby causing a deflection of the drilling direction. When using such devices, a drilling operation is discontinuous in that drilling is performed in successive runs or trips between which drilling is stopped to permit the displacement of the deflecting device.This results in a considerable amount of time lost, which increases the cost of each drilling operation.

In drilling devices which make use of a down hole motor, it has been proposed to locate a crank connector of selected angle between the lower part of the drill string and the so-called drill head (i.e., the assembly of the drill bit and the downhole motor). However, every time the drilling direction is to be changed it is necessary to raise the whole drill string to the surface and to change the crank connector for another one whose angle is selected in accordance with the desired deflection.

New so-called hinge crank connectors of the type mentioned in French Patent No. 2 175 620 have been proposed. These connectors usually comprise two tubular parts which are hinged to each other and which can only adopt two relative positions. In a first position, the two parts of the connector are aligned (the angle of the connector is equal to zero), while in the second position the two parts form a preselected angle therebetween.

As with the previously described crank connectors, it is necessary that at least one element of the connector be raised to the surface when the desired drilling deflection is not compatible with the angle between the two parts of the connector.

To obviate these drawbacks there has been proposed means for varying the angle of the crank connector without the need of raising the crank connector to the surface. Control means for such a connector are described in published French Patent Application No. 2 1 77 920 and in UK Patent No. 1 494 273.

Published French Patent Application No.

2 432 079 and Certificates of Addition Nos 2 453 265 and 2 453 269 thereto describe a crank connector constituted by two tubular members which form therebetween an angle which is remotely adjustable. This crank connector, whose angle is adjustable by remote control from the surface, essentially comprises first and second tubular members which are secured to each other, the second member being rotatable about an axis which forms an angle with the axis of the first member, means constraining the tubular members to rotate with each other, and remote control means for stepwise adjustment of the angular position of the second tubular member relative to the first tubular member.

In order to control rotation of the second tubular member and to prevent any undesired relative rotation of the tubular members after adjustment of their angular position, auxiliary locking means are desirable.

A preferred embodiment of the present invention described below has such an auxiliary locking means which is of reduced size so as to permit the construction of a crank connector of small bulk.

According to the present invention there is provided a crank connector for directional drilling, the connector comprising a first tubular member to be secured at the lower end of a drill string, a second tubular member to be connected to a downhole motor for rotating a drill bit, the two tubular members being connected to each other, the axis of said second tubular member being rotatable about an axis of rotation which is at an acute angle to the axis of the first tubular member, and said axis of rotation and the axes of the two tubular members being distinct from each other and converging substantially at one and the same point, remote control means for varying at will the angular position of the second tubular member with respect to the first tubular member by pivoting the axis of the second tubular member about said axis of rotation, means for maintaining the tubular members in a selected relative angular position with respect to each other, a rotary fitting which connects the tubular members and whose axis forms said axis of rotation, said fitting being traversed by a connecting shaft connecting the tubular members, the shaft being slidable in the tubular members while being constrained to rotate with one of said tubular members, and the shaft having a locking position in which it also becomes constrained to rotate with the other tubular member and from which the shaft can be disengaged by axial displacement, remote control means for axially displacing the connecting shaft, driving means by means of which an axial displacement of the shaft from its locking position is transformed into a rotation of the second tubular member about said axis of rotation, and auxiliary locking means for preventing undesired rotation of the tubular members after adjustment of their relative angular position, the auxiliary locking means comprising at least one radially retractable locking finger, axially extending grooves, and means providing for cooperation between the retractable locking finger and the grooves after the shaft has caused a desired rotation of the second tubular member when rotatably disengaged from the second tubular member, said co-operation between the finger and the grooves being maintained until the shaft has returned to its locking position.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, wherein: Figure 1 diagrammatically illustrates the basic concept of a variable angle crank connector; Figures 2A and 2B are diagrammatic crosssections showing main components of the crank connector and locking means Figure 3 is a perspective view of a portion of a guide groove; and Figure 4 is a developed view of a portion of the guide groove.

Figure 1 diagrammatically illustrates the basic concept of a variable angle crank connector. The connector includes two tubular members 1 and 2 connected to each other by a fitting element 2a which has an axis A and which is, for example fixedly secured to the member 2. The tubular member 1 has an axis X'X and the tubular member 2 has an axis Y'Y, both of which axes converge with the axis A at one and the same point 0.

The angles (A,X'X) and (AY'Y) formed by the various axes have the same value . By continuously rotating the element 2 about the axis A, the angle defined by the axes X'X and Y'Y can be varied between a minimum value of zero (the position of the member 2 indicated by dotted line in Figure 1) and a maximum value 2 a (the position of the member 2 shown by solid lines in Figure 1).

Figures 2A and 2B diagrammatically show major or primary elements of the crank connector, i.e. the upper tubular member 1, the lower tubular member 2 and a connecting shaft 20 in a position where the angle between the upper and lower members of the crank connector is equal to zero.

The upper member 1 is connected to the lower end of a drill string (not shown) while the lower element 2 is secured to a downhole motor (not shown). For the sake of simplicity of the drawing, each of the tubular members 1 and 2 has been shown as a single-piece element; however, they may be made up of a plurality of elements secured to one another to facilitate machining and assembling of the connector.

The member 1 includes a bore 11 at its lower end, the bore having the axis A. A lower face 12 of the member 1 extends in a plane perpendicular to the axis A, the plane in which this face is contained passing through the point of convergence of the axes X'X and A.

The upper end of the member 2 carries a fitting portion or element 2a which is complementary to the bore 11 and whose axis forms the angle a with the axis Y'Y of the member 2. The member 2 includes a shoulder 13 which is perpendicular to the axis of the fitting element 2a and is contained in a plane passing through the intersection of the axis Y'Y and the axis of the fitting element 2a.

The tubular members 1 and 2 are maintained interlocked by an abutment 14 capable of withstanding the axial stresses applied to the connector when in operation. Centering of the element 2a in the bore 11 is ensured by roller bearings, such as those diagrammatically shown at 1 5, 16 and 17, which permit relative rotation of the tubular members 1 and 2. Gaskets 18 and 19 ensure sealing between the tubular members 1 and 2.

The shaft 20 is hollow and is positioned inside the tubular members 1 and 2 coaxially of the element 2a and the bore 11, i.e., coaxially of the axis A. The shaft 20 and the member 1 are rotatably secured to each other, i.e. constrained to rotate with one another. This is obtained by the co-operation of a groove bore 21, located in the upper member 1, with complementary grooves 22 located in the shaft 20. The shaft 20 also includes grooves 23 which are co-operative with a grooved bore 24 of the lower member 2 when the shaft 20 is displaced as a result of the action of a spring 25 to the position illustrated on the right hand side of Figures 2A and 2B. In this position, the member 2 and the shaft 20 are rotatably secured to each other. The shaft 20, which is axially displaceable within the tubular members 1 and 2, includes on its outer wall a profiled guide groove 28 which co-operates with at least one guide finger 26, integral with the member 2, for rotating the member 2 about the axis A when the shaft 20 is axially displaced from its position illustrated on the right hand side of Figures 2A and 2B. The profiled guide groove 28, shown in perspective in Figure 3, permits step-bystep rotation of the tubular member 2 about the axis A.

The lower part of the shaft 20 can include, for example, control means (not shown) of the type described in the above-mentioned French Certificate of Addition.

The crank connector includes a locking device which comprises at least one radially retractable finger 100 biassed radially outwardly by the force of a spring 101. The finger 100 is located in a housing defined by an opening 102 provided in the shaft 20. A collar or sleeve 103, slidable on the shaft 20 on which it is rotatably secured, maintains the finger 100 inside its housing when the shaft 20 is rotatably secured to the tubular members 1 and 2, i.e. when the shaft is in the position shown on the right-hand side of Figures 2A and 2B and during the relative rotation of the tubular members 1 and 2. In this position, the collar 103 is maintained axially secured to the shaft 20 by means of balls 104 which co-operate with slots 105 in the collar 103. The collar 103 also includes orifices 106, the function of which will be made apparent in the following part of this description.

Grooves 107 are machined on the interior of the tubular member 2 parallel to the axis thereof and corresponding substantially to the profile of the guide groove 28.

The operation of the above-described crank connector is as follows. Assume that the crank connector is in the position shown on the righthand side of Figures 2A and 2B, the axes of the tubular members 1 and 2 are aligned and the drilling has reached a desired depth at which the angle of drilling is to be changed.

The shaft 20 is displaced axially and downwardly as shown on the left-hand side of Figures 2A and 2B against the action of the spring 25. The finger 26, which was in a position 26a (Figure 4), moves to a position 26b. In the position 26b, the grooves 23 of the shaft 20, and the grooved bore 24 of the tubular member 2, are disengaged from one another, allowing free rotation of the shaft 20 with respect to the tubular member 2. The axial movement of the shaft 20 continues and the finger 26 reaches a position 26c, causing rotation of the tubular member 2 about the axis A through an angle of 8=2/n (n is a whole number). The tubular members 1 and 2 of the crank connector form therebetween a preselected angle in the range of from 0 to 2 a.

Simultaneously, an end of the collar 103 contacts the fingers 26, which prevents additional axial displacement of the collar 103. As the axial displacement of the shaft 20 continues, the finger 26 causes the collar 103 to separate from the shaft, allowing the retractable fingers 100 to enter the housings 106 of the collar 103. As a result of the action of the springs 101 , the fingers 100 extend from their housings and their ends enter the grooves 107 to rotatably secure the shaft 20 to the tubular member 2. As shown on the left-hand side of Figures 2A and 2B, the fingers 26 are now in a position 26d (Figure 5).

As the shaft 20 is subjected to the sole action of the spring 25, the shaft 20 is forced back axially and upwardly to the position shown on the right-hand side of Figures 2A and 2B. As a result of the co-operation of the fingers 100 with the grooves 107, the finger 26 is displaced axially from the position 26dto a position 26e (Figure 4), i.e. without any relative rotation of the two tubular members 1 and 2.

At this moment, the collar 103 contacts an abutment 108 of the tubular member 1 which secures it against axial motion. Additional movement of the hollow shaft 20 causes displacement of the fingers 26 from the position 26e to a position 26f(Figure 4) such that the fingers 100 are forced back into their housings 102 by means of an inclined ramp 111, and the collar 103 is locked to the shaft 20. The assembly thus returns to the position shown on the righthand side of Figures 2A and 2B.

A further rotation of the tubular member 2 through the angle S can be achieved by repeating the above-described operation.

Various modifications can be made to the above-described crank connector without departing from the scope of the invention. For example, control means can be provided for ensuring that, after displacement, the shaft 20 is returned to its original position. To accomplish this, a magnetic detector 109, permanently attached to the shaft 20, and a detector 110 such as that commercially available from Radio Technique under the reference 'R22', can be used.

The detector 110 can be fixed to the tubular member 1 and connected to an electrical circuit (not shown). Actuation of the detector 110 by the magnetic element 109 permits the detection of full axial displacement of the shaft 20.

In the above-described example, the retractable fingers 100 are located in the shaft 20 and the axial grooves 107 in the tubular member 2. It is however also possible to provide the axial groove in the shaft 20, the retractable fingers then being carried by the lower tubular member 2.

Claims

1. A crank connector for directional drilling, the connector comprising a first tubular member to be secured at the lower end of a drill string, a second tubular member to be connected to a downhole motor for rotating a drill bit, the two tubular members being connected to each other, the axis of said second tubular member being rotatable about an axis of rotation which is at an acute angle to the axis of the first tubular members being distinct from each other and converging substantially at one and the same point, remote control means for varying at will the angular position of the second tubular member with respect to the first tubular member by pivoting the axis of the second tubular member about said axis of rotation, means for maintaining the tubular members in a selected relative angular position with respect to each other, a rotary fitting which connects the tubular members and whose axis forms said axis of rotation, said fitting being traversed by a connecting shaft connecting the tubular members, the shaft being slidable in the tubular members while being constrained to rotate with one of said tubular members, and the shaft having a locking position in which it also becomes constrained to rotate with the other tubular member and from which the shaft can be disengaged by axial displacement, remote control means for axially displacing the connecting shaft, driving means of which an axial displacement of the shaft from its locking position is transformed into a rotation of the second tubular member about said axis of rotation, and auxiliary locking means for preventing undesired rotation of the tubular members after adjustment of their relative angular position, the auxiliary locking means comprising at least one radially retractable locking finger, axially extending grooves, and means providing for cooperation between the retractable locking finger and the grooves after the shaft has caused a desired rotation of the second tubular member when rotatably disengaged from the second tubular member, said co-operation between the finger and the grooves being maintained until the shaft has returned to its locking position.

2. A crank connector according to claim 1, wherein the retractable finger is carried by the shaft and the grooves are provided in the second tubular member.

3. A crank connector according to claim 1, wherein the retractable finger is carried by the second tubular member and the grooves are provided in the shaft.

4. A crank connector according to claim 1, claim 2 or claim 3, comprising means for detecting the return of the shaft to its locking position.

5. A crank connector substantially as herein described with reference to the accompanying drawings.