Well slotter

Nov. 7, 1939.

2,178,554

C. P. BOWIE

WELL SLOTTER

Filed Jan. 26, 1938

<img file="US2178554A_D0001.tif" />

Patented Nov. 7, 1939

2,178,554

UNITED STATES PATENT OFFICE

2,178,554

WELL SLOTTER Clifford P. Bowie, Berkeley, Calif.

Application January 26, 1938, Serial No. 187,021

Claims.

This invention relates to apparatus for increasing the effective producing area of a drilled well, and constitutes an improvement upon the invention disclosed and claimed in my applica5 tion Serial No. 142,953, filed May 17, 1937.

More specifically, the invention relates to an apparatus which is capable of being lowered into 'a drilled well, and which can be operated from the surface, to cut slots in the formation into or 10 through which the well has been drilled. The slots are vertical and extend out radially from the well, and there may be as many slots cut, one at a time, as is desired. Each slot greatly increases the exposed area of the formation, from 15 which the fluid may exude. Some wells which, when drilled in the ordinary way as cylindrical holes, produce comparatively little fluid because of certain adverse conditions of underground structure or pressure, can be greatly improved by 20 increasing their effective area and thereby securing greater production. By cutting a plurality of narrow slots in the formation, instead of reaming it out into an enlarged cylindrical chamber, the exposed area is greatly increased, with25 out the danger of destructive caving.

The principal objects of this invention are to provide an apparatus for the purpose described above which is simple and rugged in construction and easy to operate, and in which fluid pressure 30 means are provided for operating and controlling the feed of the cutter. Other objects and advantages of the invention will be apparent from the following description, which should be read with the understanding that changes, within the 35 scope of the claims hereto appended, may be made in the form, construction and arrangement of the several parts herein shown and described.

A preferred embodiment of the invention is illustrated in the accompanying drawing, in which 40 Fig. 1 is a vertical section showing the device in position in the well.

Fig. 2 is a vertical section taken at right angles to the plane of Fig. 1.

Fig. 3 is a vertical section, enlarged, of a modi45 fled form of fluid pressure operated feed mechanism.

The apparatus requires suitable means for locating or orienting it in the well and holding it securely in position, and suitable driving means 50 for supplying the cutting and feeding power. These holding and driving means may be located either in the well in proximity to the apparatus itself, or at the surface and connected with the apparatus by strings of tubing. The latter arrangement is shown in the drawing, the ref(CI. 255—1) erence numeral 11 indicating a string of tubing to which the apparatus is attached and by which it is lowered or raised and held in position, and 12 indicating a smaller string of either tubing or rods which are rotated to provide the power for 5 operating the cutter. The means at the surface for holding the string 11 and rotating the string 12 are not shown.

The drive tubing 12 has a bevel pinion 13 secured to its lower end, which meshes with a gear 1C 14 secured upon a horizontal shaft 15 mounted in the supporting tubing II. Chains 16 connect said shaft 15 with a second horizontal shaft 17, on which is a sprocket 18. Suitable support must be provided for the bevel pinion 13, such as a IS spider 19 which provides a journal for the lower end of the tubing 12.

The diameter of the supporting tubing II is reduced below the shaft 17, said reduced portion forming a shell Ila having a cylinder 20 in 20 which operates a piston 21 and a piston rod 22. Piston rod 20 is prevented from rotating by a guide pin 23 and slot 24. The lower end of said piston rod is enlarged, flattened and slotted, as shown at 25, and carries a horizontal spindle 26 25 upon which an idler sprocket 27 is mounted in the slot of said end 25. The spindle 26 also serves as a pivot for the forked upper end 20 of an arm 29, said arm extending downward and having an idler sprocket 30 mounted in its forked lower 30 end 31.

An endless, flexible cutter in the form of a chain 32, having spaced projecting teeth 33 operates over the sprockets 10, 27, and 30. Projecting teeth 33 may be of any desired shape, al- 35 though I prefer the bucket type. When the drive tubing 12 is rotated in such a direction as to cause the left hand run of the chain 32 to move upward, the pull of said chain will swing the arm 29¹ to the left Fig. 1. The teeth 33 will, 40 therefore, come against the left hand side of the well. A bearing plate 34 is provided upon the back of the fork 25, to keep the right hand run of the chain from rubbing against the side of the well. 45

The pull of the upwardly moving run of the chain 32 is not sufficient to feed the cutter teeth 33 into the wall of the well with the force necessary to cause them to cut a slot therein, especially in hard formation. Therefore, to provide addi- 50 tional feeding force, fluid under pressure is introduced into cylinder 20, exerting a downward pressure on piston 21 and piston rod 22, swinging the lower end of arm 29 forcibly to the left and causing teeth 33 to dig into the left hand side 55

2,178,654 of the well, cutting a narrow slot into the formation. This cutting continues (until arm 29 reaches a horizontal position) as long as the drive tubing 12 is rotated and fluid pressure is _ supplied to the cylinder 20; the chain pulling up on the lower sprocket 30 and the downward pressure on piston rod 22 swinging the arm 29 more and more to the left as the cutting progresses. The chain is kept tight by the downward pressure of the fluid in cylinder 20 acting on piston 21 and rod 22. A strong spring 35, interposed between the bottom 36 of the shell I la and a pin 31 secured to the piston rod 22, holds said rod at the upper limit of its travel, so that the arm 25 29 normally hangs vertical, as shown in full lines in the drawing. Pressure fluid is supplied to the cylinder 20 through a pipe 39, which may extend to the surface within the tubing 11, or which may be connected, by a suitable rotatable 20 coupling not shown, with the tubing 12, in which case said tubing 12 serves as the conduit for the pressure fluid.

When the device .has reached the position shown in broken lines in Fig. 1, the slot in the 25 formation will have the shape shown by the line 39, and that slot will have been completed. Fluid pressure in cylinder 20 is released and spring 35 returns the apparatus to the vertical position shown in full lines. As the pressure in cylinder 30 20 is released, rotation of the drive tubing 12 may be continued if desired. Spring 35 also serves to hold arm 29 in a vertical position when the machine is being lowered into or raised out of the well or when it is being oriented from one cutting 35 position to another. When one slot has been cut, the machine is rotated to a new position, by turning the tubing 11, and a new slot is cut. This process can be repeated as many times as desired, to cut a series of slots radiating outwardly from 40 the well, thereby greatly increasing the exposed surface of the formation.

The spring 35 may be eliminated, and both upward and downward movement of the piston rod 22 and arm 29 effected entirely by fluid pres45 sure, by the apparatus shown in Fig. 3, which takes the place of that portion of Fig. 2 encompassed within the bracket 3. The lower end of the shell I la supports a cylinder 40 in which is a piston 41 fixed to the upper end of the piston ro rod 22. The lower end of said cylinder has a ^J closed head 42, and its upper end is formed by a head 43 having apertures 44 and downwardly extending lugs 45 in which are horizontally slidable pins 46 having rounded ends. The piston 41 is 55 hollow, and has a rounded interior flange 47 at its upper end, which engages the outer ends of the pins 46 as shown.

Two cylinders 48 and 49, of different diameters, are formed in the shell I la above the head 43 80 of the cylinder 40. Connected pistons 50 and 51 operate in said cylinders 48 and 49 respectively. A stop lug 52 extends downwardly from the piston 51, and a central pin 53 extends still further down, through the head 43 and engaging the inβ5 ner ends of the horizontal pins 46. An eye bolt 54 extends upwardly from the piston 50 through an apertured diaphragm 55, and a spring 56 below said diaphragm normally retains pistons 50 and 51 in their lower positions. A pipe 57 leads from 70 cylinder 49 below piston 51 to the surface. Cylinder 40 may be opened to the interior of the well by any suitable means indicated diagrammatically by pipe 58 and valve 59, and said cylinder 40 may also be supplied with fluid under pressure 75 as indicated by pipe 60 controlled by valve 61.

Before the apparatus is lowered into the well, the control pistons 50 and 51 are first raised, by inserting a bar into eye-bolt 54 through a slot 62 in shell Ila, thereby raising pin 53 and permitting pins 46 to move inwardly to free the 5 flange 47. Piston 41 and rod 22 are then raised to top position, as shown, and pistons 50 and 51 are allowed to drop, forcing pins 46 outwardly beneath flange 47 to hold piston 41 and rod 22 in elevated position. The parts are now in the posi- 10 tion shown, with rod 22 locked in its upper position so that the arm 29 and the cutter chain 32 hang vertically. The device is then lowered into the well.

If the well is empty, i. e., contains no fluid 15 under pressure, the valve 59 is closed and the valve 61 is opened before the apparatus is lowered. Then when the desired depth is reached, fluid under pressure is admitted through the pipe 60 to the cylinder 40 below the piston 41, said pres- 20 sure being sufficient to support the weight of the piston 41, rod 22, and arm 29. Fluid under pressure is then also admitted through the pipe 57 to the cylinder 49 below the piston 51. This pressure raises the piston 51 and its pin 53, freeing 25 the locking pins 46. The apparatus is now in position to begin slotting, and as the cutter chain moves and pulls the arm 29 out of line, the pressure in cylinder 40 is decreased and that in cylinder 49 increased, the latter pressure operating 30 above piston-41 through ports 44. Thus piston 41 and rod 22 are forced down to feed the cutter into the formation. When the slot is completed, pressure is increased in cylinder 40 and decreased in cylinder 49, thereby lifting piston 35 41 and rod 22 until arm 29 and chain 32 hang vertically again, whereupon pressure in cylinder 49 is relieved entirely, allowing piston 51 and pin 53 to descend and lock piston 41 by means of pins 46. Pressure in cylinder 40 can then be relieved 40 and the apparatus pulled up or turned to a new position.

If the well contains fluid under pressure, valve 59 is opened and valve 61 closed before the apparatus is lowered, and pipe 60 need not be con- _4gnected to the surface. When the proper depth is reached, the well fluid pressure which has entered cylinder 40 through pipe 58, supports piston 41 and rod 22. Fluid under pressure from the surface is admitted through pipe 57 to cylinder ₅₀49 to raise piston 51 and release locking pins 46. This pressure in cylinder 49 is then increased above well pressure, to force piston 41 and rod 22 down to effect feeding of the cutter. Upon completion of the cut, pressure in cylinder 49 is 55 reduced slightly below well pressure to permit piston 41 to rise while still holding piston 51 up. When piston 41 is in its top position, pressure in cylinder 49 is reduced further, allowing piston 51 to drop and effect locking of piston 41 through 60 pins 46. Well pressure also acts on top of piston 50, and therefore opposes pressure in cylinder 49, but as piston 50 is smaller than pistons 51 and 41, pressure in cylinder 49 will raise piston 51 before it affects piston 41. 65

The machine is illustrated as operating below the bottom of the well casing, which is shown at 63. It is entirely possible, however, that with cutters 33 of the proper material, the slots could be cut through the casing. Thus the machine _7(lcan be operated at any point in the depth of the well.

It will be seen that, when the device is in inoperative position, the cutter chain forms an elongated loop with substantially vertical parallel 75

2,178,664 side runs, and the three supporting sprockets IS, 27 and 30 are substantially in vertical alignment, thus enabling the machine to be lowered into the well. During the cutting movement of _ the chain, however, said supporting sprockets are ⁸ shifted out of alignment, so that the side runs of the chain are spread apart into the form of a triangular loop, one of said side runs being forced against the side wall of the well to cut a slot therein.

¹⁰ The initial feeding movement, shifting the three sprockets out of line, is caused by the pull of the cutter chain. Thereafter the downward fluid pressure on the rod 22 forces the arm 29 to swing still farther to the side, feeding the chain ⁰ into the formation with greater force. If desired, the axes of the three sprockets can be positioned slightly out of line initially, so that downward pressure on the rod 22 will forcibly 2θ shift the arm 29 even before the cutter chain is started.

It is to be noted that no turning or twisting moment is applied to the pivot 26 or to the forks 26 and 28 centered about said pivot. The rod 22 25 and arm 29 are subjected only to longitudinal compression, and therefore can be much lighter than if they were required to resist bending stresses as well. The tension in the triangular cutter chain balances the compression forces in ₃₀ said rod 22 and arm 29. The reaction of the feeding force is carried by the tension in the chain and the compression in the rod 22 and arm 29 directly to the bearing plate 34 which abuts against the side of the well opposite the cut. The ₃₃ pivot 26 is subjected only to shearing stress. This ⁰ balanced arrangement of forces permits a lighter structure and greatly reduces friction of the moving parts.