US3002559A - Propellant set bridging plug - Google Patents

Description

Oct. 3, 1961 v. D. HANEs PROPELLANT SET BRIDGING PLUG 5 Sheets-Sheet 1 Filed July 22, 1957 ff/0,0 0Q2/50000 INVENTOR. VAUGHAN DEAN HANES TOHNE;a

v. DQ HANEs PROPELLANT SET BRIDGING PLUG Oct. 3, 1961 '5 Sheets-Sheet 2 Filed July 22, 1957 1N VENTOR. VAUG/-WV DEA/V HA/VES ATTOPNE'Y Oct. 3, 1961 v. D. HANEs 3,002,559 PROPELLANT SET BRIDGING PLUG Filed July 22. 1957 3 Sheets-Sheet 3 INVENToR. nmz/@HAN 05M Hawes ATTORNEY `nited States This invention relates to oil well bridging plugs of the type which are run into a well on a wire line and are se (locked in position and expanded) by means of high pressure gas generated by the burning of propellants in a closed chamber. Such devices are Well known in the art.

The invention described herein is a modification of the inventions described and illustrated in my copending patent applications led simultaneously herewith Serial Nos. 673,340, 673,260 and 673,339.

Heretofore it has been attempted to set bridging plugs of the foregoing type in either of two ways: (rl) by the sudden application of pressure generated by the rapid burning of gun powder or other explosive material, as described in U.S. Patent No. 2,189,937 issued February 13, 1940, to O. T. Broyles, or (2) by slower application of pressure generated Vby the relatively slow burning of propellants suchfas the rocket fuels described in U.S. Patent No. 2,640,547 issued .Tune 2, 1953, to R. C. Baker and Thomas M. Ragan.

Both of the foregoing methods are subject to operating disadvantages. vWith fast burning propellants of the gun powder type, the mechanical parts of the packer expanding assembly may be lactuated so rapidly that the packer elements with the result that the packer will not seal against a differential pressure across the packer element. With slow burning propellants of the rocket fuel type, the burning rate is sometimes so slow that, due to heat dissipation within the tool, insuflicient pressure is generated to set the tool. This latter trouble occurs particularly when the back pressure in the well, against which the tool is operating, is low as would be the case in shallow wells or in wells having a low iluid level.

The terms slow-burning and fast-burning as applied to propellants of the type in question usually refer to burning rates expressed in inches per second at atmospheric pressure (14.7 p.s.i.) or at some designated pressure such las 1000 p.s.i. The burning rates for propellants usu-ally increase as the pressure in the combustion chamber increases. lAt extremely high chamber pressures, on the order of 20,000 p.s.i. to 50,000 p.s.i., the burning rates `for most slow-burning propellants may become Vso rapid as to approach a detonation. Thus it may be said that there are no slow-burning propellant at such high chamber pressures. It has been found that some propellants which burn slowly at low pressures (for example: 0.08 inch pergsecond at 1000 p.s.i.) burn so slowly at atmospheric pressure that they merely smolder. The rate o f dissipation of heat from such propellants, when burned in a conventional chamber, is so rapid as to prevent apressure build up suiciently to maintain an adequate burning rate, that is, a burning rate which will maintain 4a gas pressure in the chamber suflicient to operate the device in question. In some instances the propellant may become extinguished. `Slow-burning propellants of the type in question are disclosed in patent application Serial No. `109,409 assigned to the same assignee as the present application.

In the operation of a piston-actuated wire-line bridging plug of the general type Vto' which this invention relates, it is` desirable that the operating cycle extend over a period ottime of several seconds, preferably on the order to seconds to 30 seconds, or more. Propellants are not properly expanded and locked, e

atent asses Patented Ust. 3, i961 of the gun powder type are consumed in considerably less than one second and are not suitable for use Without modification. Propellants of the slow-burning type, on the other hand, burn too slowly at pressures below the required operating pressure, which may be on the order of 10,000 to 50,000 p.s.i.

Since the propellants which may be used to raise the initial pressure and temperature in the combustion chamber are of the extremely rapid burning type, being entirey consumed in less than one second, and since it may require several seconds to establish a satisfactory burning rate for the slow-burning propellant, it is obvious that a sudden pressure drop, following the consumption of the rapid-burning propellant, may result in extinction of the slow-burning propellant before it has reached a satisfactory self-sustaining burning rate.

In order to prevent the extinction of the slow-burning propellant, or slowing down its burning rate below a useful rate, it is desirable to establish an initial pressure in the combustion chamber which is substantially higher vthan the normal burning pressure and higher than the nal operating pressure. This arrangement permits the use of a minimum amount of propellant for operating the tool, in which space is at a premium. By raising the initial pressure well above the operating pressure, the slow-burning propellant is caused to start burning at an initially high rate, so that the subsequent loss of heat (due to the reduced burning time) is held to a minimum. Thus a minimum amount of propellant will be required in order to produce the gas volume needed to perform 4the work in question.

A combined statement of Charles and Boyles Law, while derived for an'ideal gas, is suiiciently accurate with regard to actual gases for most engineering purposes, and may be expressed as:

p, is the pressure at nal temperature. v, is the volume at the iinal temperature. p0 is the pressure at 0 C.

v0 is volume at 0 C.

t is the final temperature in C.

It is an object of the present invention to provide a bridging plug design and a propellant yformulation which will permit the use of slow-burning propellants under various conditions of use.

Another object of the invention is to provide an arrangement whereby `fast-burning propellants are employed to raise the chamber pressure above the pressure at which the slow-burning propellants will burn at their desired rate for proper actuation of a bridging plug.

Another object is to provide, in the propellant cornbustion chamber, an initial pressure above the normal burning pressure for the slo -burning propellant in less than one second.

Another object is to provide, in less than one second, an initial pressure which is higher than the pressure de- Veloped by the slow-burning propellant.

Other objects and advantages of the invention will be apparent from the following description and drawings illustrating one embodiment of the invention.

FGURE l is an elevation, in cross section, illustrating one embodiment of the invention in the running-in posi tion within well casing.

FIGURE 2 is elevation, in cross section, of the device shown in FIGURE l, in the set position.

FIGURE 3 is a pressure-time chart showing a possible pressure curve over a period of time.

Referring to FIGURES 1 and 2, the numeral 1 indi cates a well casing. Disposed within the well casing 1 and supported by a wire line 2 is bridging plug 3 in the running-in position. The bridging plug 3 comprises six major parts which are movable relative to each other. These parts are: a cylinder 4, and a piston 5, providing a telescopic housing carrying wedge slips 6, oating body 7, wedge body S, and a compressible packer sleeve 9.

The piston 5 is provided at its upper end with an Venlarged head 1t) forming a downwardly facing annular shoulder 11, `a tubular body 12 having a downwardly depending tubular shank 13 of still further reduced diameter, to which is connected, as by threads 14, an enlarged tubular combustion chamber piston member 15.

The cylinder 4 is slidably mountedv on the shank 13 and piston member 15. To this end, the cylinder 4 is provided with a tubular upper portion 16Y which slidably engages the outer surface of the piston member and has an inwardly turned flange 17 at its upper end, slidably engaging the exterior surface of the tubular shank 1 A suitable sealing means, such as an Q-ringv 18, is mounted in the flange 17 in sealing relation with the exterior surface of the shank 13. The lower portion-of the cylinder 4 is enlarged as indicated at 19 .to provide an upwardly facing annular shoulder 20 which supports the lower wedge slips 6 when in their retracted position, asl shown in FIGURE l. The interior of the cylinder 4, below the ange 17 is enlarged (to slidably engage the exterior surface of the piston 5 and) to form a combustion chamber 21 and a pressure chamber 22. Sealing means, such as the O rings 23, is positioned in the exterior surface of the piston member 15 in sealing engagement between the walls of the cylinder 4 land the member 15.

The support plate 24 is positioned between the lower end of shank 13 and a thin disc 25. The disc 25 is supported on an annular inwardly projecting ledge 26 of the member 15. The plate 24 and disc 25 are retained in place by means of the thread 14, the lower surface 27 of the shank 13 and the ledge 26 of member 15.

The pressure chamber 22 communicates with the combustion chamber 21, by means of the ports 28 formed in the wall of the member 15.

As shown in FIGURE 1, a charge of gas-generating propellant 29 is positioned within the combustion chamber 21. An electric igniter 30 is positioned in the upper end of the propellant grain 29. The shank 13 is provided with an axial passageway affording an expansion chamber 31. The upper end of passageway 31 is closed by a valve member in the form of a smallpiston 32, slidable in the pasageway 31. The piston 32 carries sealing means such as the O-ring 33, to seal the upper interior end of the passageway 31. The piston 32 has an axial hole 34 with an enlarged upper` end hole 35. The packing sleeve 36 is positioned within the upper end hole 35 and retained in place by means of the packing gland 37 and the threads 38. The upper end of piston 32 is provided with threads 39 to receive wire line head 40 to which is attached by any suitable means, the electric wire line cable 2. The insulated extension electric wire 41 of cable 2 passes through the head 40, gland 37, packing 35, axial hole 34, passageway 31, support plate 24, disc and connects to electric igniter 31B. The electric igniter is provided with the ground connection 42. The packing 35 provides, by means of the packing gland 37 and threads 38, a method of pressure sealing the upper end of the hole 34 and the passageway 31. Within the tubular body 12 is the upwardly extending tubular body 43 forming an extension of the shank 13 and the passageway 31. Transverse holes 44 are provided in the tubular body 43 to receive the piston 32 retaining shear pins 45. The shank 13, may be provided with the vent hole 46, communicating between the passageway 31 and the pressure chamber 22.

The floating wedge body 8 is tubular in form with its interior surfaces 47 in slidable engagement with the exterior surface of the cylinder 4. The lower portion of the wedge body S is tapered downwardly and inwardly to form a conical seat 48 for the lower wedge slips 6. The lower wedge slips 6 are normally held in their retracted position, resting upon the shoulder 20, by any suitable means, such as shear pins 49 attached to the cylinder 4.

The upper end of the wedge body 8 terminates in an upwardly facing annular shoulder seat S11 which serves as a seat for the lower end of the cylindrical, resilient Vpacker sleeve 9.

The floating body 7 is tubular in form with its interior surface 51 in slidable engagement with the exterior surface of the tubular body 12 `and its interior surface 52 in slidable engagement with the exterior sur-face of the cylinder 4. The upper portion of the oatin-g body 7 is tapered upwardly and inwardly to form a conical seat 52A for the upper wedge slips 6. The upper wedge slips 6 are normally held in their retracted position, against shoulder 11, by any suitable means, such as shear pins 53 attached to the piston 5.

The lower end of the floating body 7 terminates in a downwardly facing annular shoulder seat 54 which serves as a sea-t for the upper end of cylindrical, resilient packer sleeve 9.

In order to lock the cylinder 4 and piston 5 in the set position, the outer surface of piston member 15 is providedV with a series of vertically spaced, upwardly facing teeth 55. The teeth 55 are adapted to engage a series of vertically spaced, downwardly facing teeth 56 formed on the innerv face of wedge locks 57 mounted in recess 5S formed in the lower end of the cylinder 4. The bearing wall 59 ofthe recess 58 is tapered upwardly and inwardly. A compression body, of any suitable material such as an O ring 6i), is mounted in the recess 55 between the lower surface of the wedge locks 57 andV the upper surface of a retainer plate 61. rThe retainer plate is attached to thecylinder 4, by any suit-able means, such asthe screws 62.

The cylindrical, resilient packer sleeve 9 is mounted between the shoulder seat 54 and 50 and has its interior surface in slidable engagement with the exterior surface of the cylinder 4.

Any suitable electrical' means, such as a wire line service unit, may be used to initiate combustion of the propellant gnain 29 by tiring the electric igniter 30. Other means, not described, can be used to ignite the propellant grain 29.

The propellant grain 29 consists of a small amount of fast burning propellant 62A inserted into the upper end of a cylindrical slower burning propellant 63. A small quantity of igniter material 64, such as a mixture ofv black powder andmagnesium, is placed between the electric igniter 30 and the fast burning propellant 62A to assistV in ignition of the propellant grain 29. The propellant grain 29 is provided with the external covering or restriction 65 to give an end burning slow burning propellant 63.

FIGURE 2 illustrates the device of FIGURE 1 in set position in the well casing L Upon application of electrical current, from any suitable source, such as a wire line service unit, the electric'squib 30 is red, igniting the igniter material 64 and initiating the burning of the propellants 62A and 63.

High pressure gas is generatedby the burning, in less than one second, of all of the fastfburning propellant 62A and the initial burning of the slow burning propellantV 63. The thin disc 25 is provided with an oriice hole 66V to restrict the flow of high pressure' gas into the passageway 31 and to provide a high pressure gas chamber inthe combustion chamber 21 andthe pressure chamber 22. The burning of the fast. burning propellant 62A rapidly increases the pressure and: temperature in the combustionk chamber 21Y and the;v pressure chamber 22. The maximum gas pressurefisV reached in less than onesecond, due to combustionY oftall of the fast burning propellant 62A, in'lessV thanroner second. The pressure immediately beginsto drop due to escapingthrough the orice 66 into the passageway 31 and due to the reduced gas supplied by the burning of the slow burning propellant 63. The pressure continues to drop until the pressure is equalized throughout the volume contained in passageway 31, combustion chamber 21 and pressure chamber 22.

The thin disc 25 may be made of fusible material to enlarge the oriii'ce hole 66 as the combustion chamber temperature increases to allow for more rapid equalization of the gas pressure throughout the chambers. Further, the thin disc 25 may be designed to shear or rupture out to the diameter of the hole 67, provided in support plate Z4, when the maximum gas pressure is reached. This enlarged opening is shown in FIGURE 2.

The Vent hole 46, in shank 13, may or may not be provided to help in equalization of gas pressure.

The gas pressure generated by the burning of the propellant grain Z9 passes outwardly through ports 28 and into the pressure chamber 2-2 formed between the 0 ring seals 18 and 23. The cylinder 4 moves upwardly on the shank 13 of the piston 5, and in so doing may be considered for all practical purposes to simultaneously shear the pins 49 and 53, releasing the upper and lower wedge slips 6. Continued upward movement of the cylinder 4 with respect to the piston 5 pushes the iloating body 7 and wedge body 8 upwardly thereby simultaneously causing the compressible packer sleeve 9, which is restrained between the shoulders 50 and 54, to be compressed and expanded laterally, and putting into motion the upper and lower Wedge slips 6, due to movement on conical seats 48 and 5-2, whereby the packer sleeve 9 and Wedge slips 6 are caused to be tightly engaged ywith the inner wall of the well casing 1. Also, at the same time, upward movement of the cylinder 4 in respect to the piston causes the teeth 56 of the wedge lock 57 to engage the teeth 55 on the piston 5, to lock the cylinder 4 against any subsequent downward movement, and thus maintaining the packer sleeve 9 in seal-ing engagement with the well casing 1. Continued build-up of pressure, after pressure equalization described above, in the chambers 21, 22 and passageway 31 will cause the retaining shear pins 45 to shear, releasing piston 32 and thereby releasing the pressure.

The retaining shear pins are sheared out at a much lower pressure than that developed in the chambers 21 and 22 during the combustion of the fast burning propellant 62A. The thin disc 25, by means of the other methods described, allows the gas to expand slowly into the passageway 31 and the pressure then equalizes at a pressure lower than the shearing strength of the pins 45.

The expanded packer sleeve 9 together with the expanded upper and lower wedge slips 6 will enable the bridging plug 3 to withstand high dilierenti-al pressures of several thousands of pounds per square inch in either direction.

The shearing of the retaining shear pins 45 releases the wire line 2 and the wire line head 4@ from the bridging plug 3. The wire lin-e and head may be removed from the well.

FIGURE 3 illustrates a chart that could be produced by the burning of the propellant grain 29 in the bridging plug 3. The pressure lines of the chart are indicated by the capital letter P with subscript numbers. The pressure increases as the subscript numbers increase. The time lines of the chart are indicated by the capital letter T with subscript numbers and subscript number plus x. The time interval x has been cut out of the chart. The time interval increases in seconds as the subscript numbers increase.

Referring to FIGURE 3 the point 68, on the chart, is the ignition point or time of the propellants grain Z9. The point 69 is the time and pressure point where the fast burning propellant 62A and slow burning propellant 63 is ignited. The curve developed between points 68 and 69 may be produced by the igniter 30 and the igniter material 64. 'The point 70, is the time and pressure point, -wherethe maximum pressure is reached due to the burning of the fast-burning propellant 62A in less than one second. The curve developed between points 69 and 70 is produced by the burning of the fast burning propellant y62A and a small amount of the slow burning propellant 63. The pressure -begins to immediately fall lafter point 70 is reached due to expansion into the passageway 31 and chamber 22 of FIGURES 1 and 2. The point 71 is the time and pressure point, where the pressure equalizes in the combustion chamber 21, passageway 31 and pressure chamber 22 of FIGURES 1 and 2. The curve developed between points 70 and 71 is produced by the equalization of the gas pressure into the passageway 31, the chamber 22 and the burning of a small amount of the slow burning propellant 63. The point 72, is the time and pressure point, where the pressure developed, bythe slow burning propellant 63, becomes high enough lto shear the retaining shear pins 45 and release the pressure from the chamber of the bridging plug 3 into the casing 1. 'Ihe curve, developed between points 71 and 72, is produced by the burning of the slow burning propellant 63 over a time interval ending at Tl2-l-x. This time interval can, however, be any time greater than one second. The curve developed, beyond the point 72, is produced by the gas escaping into the well casing. Y

The foregoing description is illustrative only of one embodiment of the invention which is not to be limited thereto but is of the scope dened by the appended claims.

I claimt:

1. A device adapted for use in 4a well casing comprising: a piston closed at Vone end and having a cavity therein, a cylinder receiving said pistonv in telescopic relation, a tirst combustible gas producing material having a slow burning rate arranged within said piston cavity, a second combustible gas producing material having a' burning rate faster ,thanv said rst gas producing material arranged contiguously within said piston cavity, means tor igniting said second gas producing material arranged in said piston cavity, said cylinder having a longitudinal axis and an enlarged portion extending radially outwardly arranged coaxially with said axis, a rst and a second wedge slip, a means .for supporting said trst wedge slip `attached to the piston and arranged coaxially with said cylinder enlarged portion, said slip supporting means having an expansion chamber therein lthat is in communication with said piston cavity, a means for regulating the ow rate of a iiuid interposed between Said retention means expansion chamber and said piston cavity, said piston having a passageway arranged between the external surface into said piston cavity, said piston passageway arranged between said flow rate regulating means and said gas producing materia said rst wedge slip encompassing and abutting said slip supporting means, said second wedge slip encompassing and abutting said cylinder enlarged portion, a radially expandable sleeve member arranged around said cyllnder and between said rst and said second slips, and a plurality of means for expanding said rst and second said wedge slips positioned between said sleeve member and said slips.

2. A device Iadapted for use in a well ing: a piston having a cavity therein, a cylinder receiving said piston in telescoping relation, a combustible gas-producing material arranged within said piston cavity, means for igniting said gas producing material arranged in said piston cavity, said cylinder having a longitudinal axis and an enlarged portion arranged coaxially with said Aaxis and extending radi-ally outwardly, a iirst and a second wedge sli a means for supporting said flrst wedge slip attached to the piston and arranged coaxially with said cylinder enlarged portion, said slip supporting means having au expansion chamber therein casing compristhat is in communication with said piston'cavity, a means for regulating the ow rate of a iiuid interposed between said retention means expansion chamber andvsaid piston cavity, said piston having a port arranged tbetween the external surface and said piston cavity, said piston port arranged between said flow rate regulating means and said gas producing material, said irst wedge slip encompassing and abutting said slip supporting means, said second Wedge slip encompassing and abutting said cylinder enlarged portion, a radially expandable sleeve member arranged around said cylinder and between said rst and said second slips, and a plurality of means for expanding said irst and second wedge slips positioned between said sleeve member and said slips.

3. Apparatus according to claim 2 and in addition, a means for locking attached to said piston and said cylinder to prevent movement in a direction reverse to that desired.

4. A device as in claim 2 wherein said ilow rate regulating means comprises a disc having a restricted ow orifice.

5. A device as in claim 2 wherein said ow r-ate regulating means comprises a rupturable disc.

6. A device as in claim 2 wherein said iiow rate regulating means comprises a thin disc Vfabricated of fusible material surrounding a central oriiice.

7. A device as in claim 2 whereinsaid gas producing combustible material is a material having a characteristic of achieving its normal burning pressure in a substantially closed chamber environment in not less than one second.

8. A device as in claim 2 wherein said ignition means comprise a gas producing combustible material characterized by a normal burning pressure greater than that of said gas producing material and achieving its normal burning pressure in a substantially closed chamber environment in less than one second.

9. A well packing apparatus dor use in a well casing comprising: a piston and cylinder slidably mounted in telescoping relationship to each other to `form an expansion chamber; said piston having a combustion chamber adapted to receive solid propellant materials therein; means for initiating combustion of said solid propellant materials within said combustion chamber; said piston having an enlarged `head extending through said cylinder; a plurality of slips encompassing and engaging said piston enlarged head and said cylinder members movably positioned on said piston enlarged head and said cylinder adapted to radially expand; a packer sleeve mounted on said cylinder between said members; means affording communication between said combustion chamber and said expansion chamber in operation', and means regulating the volumetric iiow rate of gaseous products of propellant combustion imposed in said piston combustion chambers; whereby the resulting longitudinal telescoping movement of the piston and cylinder relative to each other forces said members to move toward each other compressing said packer sleeve and expanding said Wedge slips into engagement with said well casing.

10. Apparatus according to claim 9 wherein locking means are provided on said piston and said cylinder to prevent further movement of either with respect to the other after displacement of said members has been achieved in operation.

References Cited in the iile of this patent UNITED STATES PATENTS OTHER REFERENCES Chemical Engineers Handbook, 1950, p. 290, York, N.Y. (Available Div. 49.)

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