GB2164372A

GB2164372A - Drill string stabilizer

Info

Publication number: GB2164372A
Application number: GB08430029A
Authority: GB
Inventors: Allen Kent Rives
Original assignee: METAL X CORP OF TEXAS
Current assignee: METAL X CORP OF TEXAS
Priority date: 1984-09-13
Filing date: 1984-11-28
Publication date: 1986-03-19
Also published as: SE8405774D0; GB8430029D0; SE8405774L; NL8403510A; DE3442045A1; AU3548584A; BR8405867A; FR2573124A1; NO844544L

Abstract

A drill string stabilizer includes an elongated tubular body (T) having a circumferential, radially extending enlargement (E) between the ends thereof. First and second groove means (20, 21) are provided in the enlargement with the first groove means (20) inclined in one direction and the second groove means (21) inclined in the other whereby the first and second groove means intersect to form opposed fluid flow paths in the well bore adjacent the stabilizer to assist in maintaining the drill string on course. <IMAGE>

Description

SPECIFICATION Drill string stabilizer This invention relates generally to drill pipe or drill string stabilizers which are adapted to be secured to rotary drill strings for engagement with the wall of a well to assist in stabilizing the drill string in the well bore.

Various types of drill string stabilizers have been proposed and are in use. Generally speaking, all provide some type of enlargement on a tubular body with longitudinal or spiral grooves formed in the enlargement for fluid flow between the drill string and the wall of the well bore. In those stabilizers in which spirals are provided in the enlargement, there may be some tendency to increase hole drag which in turn causes more erosion and wear on the stabilizer. Also, the present use of spiral ribs in a drill string stabilizer may not enable proper surface contact between the stabilizer and the well bore wall at all times.

Further, in drilling some wells, such as thermal wells or high pressure gas wells, the use of heretofore well known and common spiral stabilizers in a drill string may cause the drill string to tend to spin out of the well bore. Also, when a spiral bladed or spiral groove stabilizer is employed in a well string, the resulting manner or direction of circulation of fluid between the drill string and the well bore wall may cause the stabilizer to move to one side of the well bore, thus creating an auger effect which "walks" or moves the drill string to one side of the well bore during drilling operations.

The present invention provides an opposed spiral arrangement in a drill string stabilizer which provides an opposed fluid flow path in the stabilizer enlargement to assist in inhibiting the drill string in which the stabilizer is employed from spinning out of a thermal well being drilled.

Yet another object of the present invention is to provide a dual spiral arrangement in an enlargement on a tubular body forming a stabilizer for a drill string to provide a dispersed surface arrangement on the stabilizer which maintains surface contact with the well bore wall at all times.

Still another object of the present invention is provide a stabilizer employing opposed spirals for opposed fluid flow adjacent the enlargement to assist in reducing, if not substantially eliminating walking of the drill string to "auger" or "drill" the well bore off course during use.

Another object of the present invention is to provide a stabilizer for a drill string with maximum flow paths while providing maximum circumferential surface for stabilizing contact with the well bore wall.

Other objects and advantages of the present invention will become more readily apparent from a consideration of the following drawings and description.

Figure 1 is a side view of the stabilizer of the present invention and one arrangement of the opposed groove means in the enlargement on the stabilizer body; Figure 2 is a view similar to Figure 1, showing the stabilizer rotated 60 about its longitudinal axis to provide a different view of the surface means for contacting the well bore wall and the opposed groove means for circulating fluid through the dual, opposed spiral grooves in the enlargement on the body; Figure 3 is an end view on the line 3-3 of Figure 1; Figure 4 is sectional view on the line 4-4 of Figure 1 illustrating further details of the stabilizer of the present invention;; Figure 5 is a longitudinal elevation of a stabilizer having a longer enlargement than that shown in Figures 1 and 2 and rotated 30 about its longitudinal axis to provide a different view of the grooves and annular surface of the enlargement. The grooves are also of a slightly different shape. Since the enlargement E is of a longer extent on the stabilizer body, the opposed grooves therein intersect between their ends at more than one interval along the enlargement; and Figure 6 is a sectional view on the line 6-6 of Figure 5.

Attention is first directed to Figure 1 of the drawings wherein the stabilizer of the present ivention is referred to generally by the letter S. It includes an elongated tubular body T having threaded means represented by the dotted line 7 at one end and shown in solid line at the other end at 8 respectively of the tubular body T for connecting the body in a drill string. A circumferentially extending enlargement referred to generally by the letter E is provided on said body T between the ends thereof, extends radially of the body and is of a larger diameter than the tubular body T to provide an outer annular surface 12 on the enlargement E as illustrated in the drawings. The ends 15 and 16 of the enlargement E are suitably tapered, beveled or concaved as desired to connect the surface 18 of the tubular body T and the annular surface 12 of the enlargement E as shown.The enlargement E is preferably integral with the body E so that the device of the present invention may be formed byforging, if desired, although it may be welded to the body. Also, the body may be formed in sections formed generally by the configuration defined by the grooves or recesses as shown in the drawings and the sections welded together and to the body to form enlargement E.

First groove means 20 are formed in the annular surface 12 of the enlargement E and the first groove means 20 is inclined at an angle in one direction relative to the longitudinal axis of the body T and enlargement E and extends spirally about and throughout the longitudinal extent of the enlargement E. Second groove means 21 are provided in the annular surface and are inclined in a direction opposite to the angle of inclination of the first groove means 20 as shown in the drawings. The second groove means 21 extends spirally about and throughout the longitudinal extent of enlargement E.

The first groove means 20 and second groove means 21 each include a plurality of grooves circumferentially spaced about and inclined relative to the longitudinal axis of the tubular body T and enlargement E as shown in the drawings. One groove 20a of the first groove means 20 intersects one groove 21a of the second groove means 21 to form a pair P of grooves which intersects between the ends of the annular surface 12, one form of such intersection being more clearly demonstrated in Figure 1 of the drawings as being adjacent the central portion of each first and second groove means 20, 21 and which intersection is represented generally by the letters IM.

The width and depth of the first and second groove means 20, 21 is such that the grooves 20a and 21 a of each pair P terminate at their end portions 22 and 23 at each end of the enlargement E in a plane adjacent the surface 18 of the body T whereby fluid in the well bore and around the tubular body T may be readily communicated into the first and second groove means 20, 21 and thus through the enlargement E without any substantial restriction.

In the embodiment illustrated in Figures 1 and 2 where the grooves 20, 21 intersect only once in the enlargement E as well as in the embodiment of Figures 5 and 6 where the grooves 20, 21 intersect more than once on an enlargement, the angle of inclination of the first and second groove means 20, 21 relative to each other and to the longitudinal axis of the body T is such that each pair P of grooves preferably intersects adjacent their end portions at each end of the enlargement E as represented generally by the letters IE as well as adjacent the mid portion of each pair of grooves as illustrated and represented by the letters IM. This will be described more fully.Where the groove means 20, 21 intersect only one time on the enlargement E as demonstrated by the embodiment shown in Figures 1 and 2, the intersection of the first and second groove means 20 and 21 as represented by the vertical line 26 and horizontal line 27 adjacent the mid portion of the enlargement E as well as the vertical lines 28 and 29 at the intersection of the ends of adjacent pairs P of grooves of groove means 20, 21 at each end of the enlargement E demonstrate that the total lengths of intersection of the first and second groove means 20 and 21 on the enlargement E relative to the total length of enlargement E preferably extends over at least approximately 50% of the total length of the enlargement E.This is also true where the enlargement E is longer as shown in Figure 5 so that the first and second groove means 20, 21 intersect at a plurality of intervals along the longitudinal extent of enlargement E as shown in Figures 5 and 6. Thus, substantial intersection of the first and second groove means 20 and 2, is provided in the enlargement E to accommodate unrestricted fluid flow in the well bore as it is circulated upwardly through the enlargement E from the drilling bit on the lower end ofthe drill string to the earth's surface in a manner well known in the art.

However, notwithstanding the intersection of the oppositely inclined and intersecting first and second groove means 20, 21 over a substantial longitudinal extent of enlargement E, the angle of inclination of the first and second groove means 20, 21 and their angle of inclination is such that surfaces 1 2a of substantial extent are provided in the ungrooved portion of the annular surface 12 of the enlargement E for engagement with the well bore wall during drilling operations to assist in maintaining the drill string centered in the well bore while accommodating unrestricted fluid flow therearound. If desired, surface areas 12a may have hard surfacing applied thereto.

More particularly, with stabilizers heretofore used, such as a single spiral bladed stabilizer, the surface on the spiral may, under some circumstances, increase hole drag and may cause more erosion on the stabilizer, thus requiring removal of the drill string from the well bore for replacement of the stabilizer, which operation is expensive and time consuming. Further, in some types of well such as thermal wells, the present invention tends to prevent the drill string from spinning out of the hole due to the pressures encountered.The opposed spiral arrangement of the first and second groove means 20,21 creates an opposed flow of fluid around the stabilizer S of the present invention which inhibits any spiraling effect of the drill string with the stabilizer of the present invention therein, which spiraling might otherwise be present in the prior art spiral groove stabilizers to cause the drill string to tend to spin out of the well bore under pressure.

Also, the dual opposed spiral arrangement and intersecting fluid flow path of the present invention assists in inhibiting walking of the drill string to one side of the well bore which may cause the drill string to move offcourse during drilling operations.

In addition, the circulating fluids in the well bore create a high pressure point of fluid contact in the general region represented by the letter D at the mid-intersection of the first groove means 20 and second groove means 21, and this conjunction of fluid contact further tends to assist in centering the stabilizer of the presert invention in the well bore.

Any suitable number of grooves or milled slots may be employed to form the first groove means 20, and typically two to four milled slots with a righthand spiral as illustrated by the numeral 20 representing the first groove means relative to the longitudinal axis of the stabilizer S may be employed. Similarly, a like number of milled slots forming the second groove means 21 and with a left-hand spiral relative to the longitudinal axis of the stabilizer S may be employed as shown.

As noted, one right-hand groove 20 of the first groove means cooperates with one left-hand groove of the second groove means 21 to form a pair P of intersecting first and second groove means as more clearly demonstrated in Figure 1 of the drawings.

Similarly, each remaining right-hand spiral groove of the groove means 20 on the enlargement E intersects a left-hand groove of the second groove means 21 to form additional pairs P of intersecting first and second groove means on enlargement E.

Each pair Pofintersecting grooves of the first and second groove means 20, 21 is adjacent another pair P of first and second intersecting grooves of groove means 20, 21 on the enlargement.

In the embodiment illustrated in the drawings, the enlargement E is of sufficient longitudinal extent so that the ends of each right-hand spiral groove of the first groove means 20 intersects the end of the left-hand spiral groove of the second groove means 21 of the next adjacent pair P as illustrated in the drawings. This intersecting arrangement of the pairs of grooves of each the first and second groove means 20, 21 forms a plurality of circumferentially spaced, generally diamond shaped portions 30 in the outer annular surface 12 between the ends of the enlargement E. Such diamond shaped portions 30 are formed between adjacent pairs P of intersecting first and second groove means 20, 21.Also, this arrangement of intersecting grooves on the enlargement E forms a plurality of circumferentially spaced, triangular surfaces 35 in the outer annular surface 12 between the ends of each adjacent pair P of first and second groove means 20, 21 adjacent each end of the enlargement E.

Thus, although the first and second groove means 20, 21 intersect over a substantial portion of the surface 12 of the enlargement Eto provide opposed fluid conducting paths wihich intersect to accomplish the desired results of the invention, the invention also provides an outer surface arrangement by means of the surfaces 12a on the enlargement E so that at least some portion of the outer annular surface 12 of the enlargement E will always be positioned to contact the well bore wall to assist in maintaining the drill string properly positioned therein during drilling operations. It will be noted that the ungrooved surface portions 12a on annular surface 12 are dispersed about surface 12.Also, the surfaces 12a, by reason of the intersecting groove means 20, 21, provide a configuration for surface portions 1 2a which has substantial annular extent between its ends which decreases in extent towards at least one end, as well as having substantial longitudinal extent for stabilizing effect while maintaining the groove size so as not to interfere with fluid flow.

In prior art spiral bladed and straight bladed stabilizers, the ungrooved surfaces are of substan tiallythe same size or width throughout their longitudinal extent.

Figures 5 and 6 illustrate an alternate form of the invention wherein the enlargement E is of greater longitudinal extent than that shown in Figures 1 and 2. The same numbers employed in Figures 1 and 2 are used to represent similar parts in Figures 5 and 6.

This provides a groove arrangement wherein the grooves 20a, 21a of the first and second groove means 20, 21 which intersect at a plurality of intervals intermediate the ends of the enlargement E as represented by the letters 11 and 12. It can be appreciated that the enlargement E can be of any desired longitudinal extent on bodyTwhiletermi- nating in spaced relation to the ends to provide surface area for receiving tongs.

While the angle of inclination of the first and second groove means 20, 21 is shown as being substantially the same and opposed, it can be appreciated that the angle of inclination of the first and second groove means 20, 21 need not be substantially the same so long as the groove means 20, 21 intersect to form surface portions 1 2a to accomplish the desired results of the present invention.

In use of the present invention, fluid is circulated from the earth's surface down through the bore 40 of the stabilizer and discharged through the drill bit at the lower end of the drill string (not shown) in a manner well known in the art. It is then circulated upwardly around the drill string in the annulus of the well bore, that is, between the well bore and the drill string to be communicated to the groove means 20 and 21 in the enlargement E of the stabilizer S which intersect or communicate over a substantial part of their extent. Since the groove means 20 and 21 are formed in opposite directions on the enlargement and intersect in the manner as described hereinabove, the fluid flowing in the paths formed by the grooves or milled slots 20, 21 impinges as it circulates through the grooves and discharges from the grooves 20, 21 in the enlargement E. The direction of fluid flow in the plurality of grooves 20 formed in the surface 12 of the enlargement E being in a direction opposite to the fluid flow in the plurality of groove means 21 tends to negate any tendency of the drill string to walk or move from one side or the other in the well bore as may encountered where a plurality of spiraled slots is formed in a stabilizer in one direction, such as is common with the prior art.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction may be made may be made without departing from the spirit of the invention.

Claims

1. A drill string stabilizer including an elongated tubular body having threaded means at each end for connecting said body in a drill string; a circumferentially extending enlargement on said body between the ends thereof to provide an outer annular surface thereon of larger diameter than said tubular body; first groove means in the annular surface inclined in one direction relative to the longitudinal axis of said body, and extending from one end of the enlargement to the other; second groove means in the annular surface inclined in the opposite direction relative to said first groove means; and said first and second groove means intersecting between the ends of the annular surface to provide converging fluid flow paths through said enlargement.

2. The invention of claim 1 wherein the first and second groove means each has a width, depth and angle of inclination relative to the longitudinal axis of the enlargement such that their intersection in said enlargement extends over at least approximately 50% of the total length of said enlargement.

3. The invention of claim 1 wherein the first and second groove means each has a depth whereby fluid may be readily communicated from around the tubular body into the first and second groove means and through the enlargement.

4. The invention of claim 1 wherein the first and second groove means each has a width, depth and angle of inclination relative to the longitudinal axis of said enlargement whereby their intersection be tween the ends of said enlargement forms at least one generally diamond shaped portion in the annu larsurface between adjacent pairs of first and second groove means.

5. The invention of claim 1 wherein said first groove means comprises a plurality of grooves circumferentially spaced about the enlargement and inclined on said enlargement in the same direction relative to the longitudinal axis of said body and wherein the second groove means comprises a plurality of grooves circumferentially spaced about the enlargement and inclined on said enlargement in the opposite direction to said first groove means so that at least one groove of said first groove means and at least one groove of said second groove means intersects between the ends of the enlargement.

6. The invention of claim 1 wherein said first groove means comprises a plurality of right-hand grooves circumferentially spaced on said en large- ment and wherein said second groove means comprises a plurality of left-hand grooves circumferentially spaced on said enlargement.

7. The invention of claim 6 wherein said first and second groove means is arranged on the enlargement so that each right-hand groove of the first groove means intersects a left-hand groove of the second groove means to form adjacent pairs of intersecting grooves which intersect between their ends on the enlargement.

8. The invention of claim 7 wherein the adjacent pairs of intersecting grooves form a generally diamond shaped portion on the outer annular surface between each adjacent pair of intersecting grooves whereby a plurality of circumferentially spaced generally diamond shaped portions is provided on the enlargement.

9. The invention of claim 8 wherein the righthand grooves of adjacent pairs intersect the lefthand grooves of adjacent pairs adjacent the ends of the enlargement whereby a plurality of circumferentially spaced, triangular surfaces is formed on said outer surface by each pair of first and second groove means adjacent each end of the enlargement.

10. The invention of claim 9 wherein the ends of the grooves of adjacent pairs communicate with the surface of the tubular body on which the enlargement is formed.

11. The invention of claims 1,2,3,4,5 or 6 wherein said first and second groove means intersect at only one position along their lengths and between their end portions on said enlargement.

12. The invention of claims 1,2,3,4,5 or 6 wherein said first and second groove means intersect at a plurality of positions along their lengths and between their end portions on said enlargement.

13. The invention of claims 1,2,3,4,5 or 6 wherein the angle of inclination of said first and second groove means is substantially equal and opposite on said body.

14. The invention of claim 7 wherein the adjacent pairs of intersecting grooves form a portion on the annular surface which is of smaller circumferential extent adjacent the ends thereof than it is intermediate its ends.

15. Adrill string stabilizer substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings, or in such drawings as amended in accordance with Figures 5 and 6.