US3007523A - Method and apparatus for treating wells - Google Patents

Description

Nov. 7, 1961 CRUSS R. P. VINCENT METHOD AND APPARATUS FOR TREATING WELLS Filed 001;. 8, 1958 FIG. 2

RENIC P. VlNCENT INVENTOR.

A r mm Y Uted States Patent 3,001,523 METHOD AND APPARATUS ron TREATING WELLS This invention relates to a method and apparatus for treating wells. More specifically, this invention pertains to a packer which is particularly adapted for use in welltreating processes in which fluids are injected into uncased oil and gas wells or into the open hole below casing in such wells.

Many deep wells, particularly oil and gas wells, are completed with the producing formation uncased. In these so-called open-hole completion wells, a production casing string is typically set through the formations overlying the producing formation and' cemented in place. The well is then completed by lowering the drill through the casing and drilling into the producing formation. After such wells are drilled, it is often desirable, either on initial completion or on recompletion, to treat selected elevations or zones in the producing formations to increase their productivity, to plug or partially plug certain strata penetrated by the open hole, or'the like. In most of these selective treatments in open hole, it is necessary to isolate a section of the hole at the elevation of the selected zone or formation by the use of one or more packers. Earth-wall packers, i.e., packers that seat against the well wall, which packers are often referred to as formation packers, normally do not hold any appreciable pressure because of unevenness or roughness of the well wall, hole oversize, or for any of a number of other reasons. Typically, the hole diameter variation over which a formation packer will hold pressure is so small that in most formations, particularly the relatively soft formations, formation packers do not hold and are not relied upon to any extent. Processes such as formation fracturing, acidizing, oil squeezing, and the like, in which isolation of a section of an uncased well has been necessary, are therefore seldom used. Instead, many of these formations which are penetrated by the open hole are merely treated by down-the-hole treatments wherein the whole open-hole section is exposed to the treating fluid and it is injected into the formation having the highest permeability. The other formations, typically the formations needing the treatment, thus remain untreated or the wells are initially completed at much greater expense by running the casing or a liner through such formations.

It is an object of this invention to provide an improved method of treating a well. It is a more specific object of this invention to provide an improved well packer and a method of utilizing the same to treat producing formations at the bottom of a well. A still more specific object of this invention is to provide a formation packer capable of being set in a well any number of times without being removed from the well, either in casing, perforated casing or in an open-hole section of a formation to permit treatment of a formation or several formations penetrated by the well at any of a number of selected zones or elevations. Other objects of this 3,007,523 Patented Nov. 7, 1961 invention will become apparent from the following deseription in which:

FIGURE 1 is a cross-sectional view of a preferred embodiment of a formation packer in a set condition in a well; and

FIGURE 2 is a cross-sectional view of a modification of the packer shown in FIGURE 1 showing the apparatus in an unset condition.

In brief, this invention may be described as a tubing anchor or well packer which employs a granular material as the anchoring material or sealant so that it may be set in either a cased or an uncased hole. It may also be described as a method of utilizing this packer to treat a well.

The invention in greater detail will now be described by reference first to FIGURE 1 of the drawings. In this description reference will generally be made to the use of the apparatus as a packer in a formation fracturing process. However, its adaptation to other well-treating processes will be apparent.

In this process a fracturing fluid is injected into a formation 9 penetrated by the well 10. A quantity of granular material 11 is first injected into the hole and this material is allowed to settle to the bottom of the well. The quantity of granular material is great enough to fill'the well to a point some 2-10 feet or more above the formation or zone in a formation which is to be treated. When more than one formation or zone in a well is to be treated, enough granular material is deposited in the well to cover at least all of the formations which are to be treated.

The granular material or sealant is preferably sand and, for best results, the sand is not spherical. Roundness of less than about 0.6 on the Krumbein scale is preferred. Particles of any irregular, rough, or flat shape are generally suitable sealants. These particles may be in a gradation of particle sizes over a relatively wide range. Smaller particles are preferred. For example, it is desirable that at least about half of the particles have a particle size in the range of -100 mesh U.S. sieve or even smaller. The remainder can be larger, but preferably all of the particles are smaller than about 40 mesh U.S. sieve. While sand is preferred, other relatively strong solids, such as crushed rock, metal shot, ground nutshells, finely divided coal, and the like, which are dense enough to sink to the bottom of the well, may be employed.

After the finely divided particles have been disposed in the well, a well conduit such as a drill pipe or tubing 12 is lowered into the well. It has a wedge such as a wedge-shaped or tapered enlargement or constriction, e.g., a bell-shaped wedge or cone 13 near the lower end. This wedge tapers from a small diameter at the top to a large diameter at the bottom and is, therefore, in the preferred embodiment frustro-conical with the base on the bottom and the apex connected to the tubing 12. It will be apparent that the wedge is not necessarily round in cross section. It may, for example, have any conoidal shape or be a square or hexagonal pyramid, or the like, preferably coaxial with the tubing. In the preferred embodiment, however, this wedge is frustro-conical, as indicated, and will generally for brevity be referred to'hereinafter as a cone. This cone has a maximum diameter at the base 14 slightly less than the diameter of the well 10 so that the cone not only passes easily through the well, but the space between the base of the cone and the well wall when the cone is centered in the well rs great enough to pass the larger particles of granular material so that the cone can be lowered through these particles in the well. Typically, the base of the cone is in the range of about xi-l inch smaller m diameter than the diameter of the well. The ratio of the radius of the cone base to the axial length of the cone, i.e., the slope of the cone is not particularly critical, but a slope in the range of about -40, typically about 20-30, is preferred. One or more radial openings through the cone which form wash-fluid jets or conduits between the inside of the tubing 12 and the outside of the cone desirably terminate near the base and on the periphery of the cone for releasing or unseating the packer to move the tubing in or remove it from the well. These washfluid conduits are normally closed by a sleeve valve 16. O- ring seals 17 and 18 above and below the wash-fluid conduits, respectively, seal the space between this sleeve valve and the inside of the cone. This sleeve valve may be opened and closed by use of a wire line or by any of a number of other means. .In a preferred embodiment a compression spring19 holds the valve resiliently in a closed position so that normally fluid flowing in the tubing cannot flow through the wash-fluid conduits. This valve has a constriction 21 of smaller diameter than the inside diameter of tubing 12 so that, as indicated in FIG- URE 2, when a ball 22 is dropped into the tubing, the ball is restrained by this constriction and fluid pressure above the ball forces the sleeve valve 16 down against the force of spring 19. With this sleeve valve in the lower position, the ports 23 in the valve are in alignment with the wash-fluid conduits 15 and fluid flowing down the tubing is diverted into the annulus 24 between the tubing and the well wall 25. Since this wash-fluid conduit terminates at or near the base of the cone and therefore at the point where the annulus 24 has a minimum cross-sectional area, the granular material above the base of the cone is easily entrained in and displaced upwardly by a wash fluid injected down the tubing.

Insomecases asecond cone 26 havingabaseincommon with the base 14 of the upper cone 13 isconnected either to the upper cone or to the tubing below the up-. per eone as a guide and, with the well wall 25, forms a similar but oppositely disposed annular wedge for the granular "material below the common base 14. The dimensions of the lower cone may be and preferably are substantially equal to the dimensions of the upper cone. A short nipple 27, open at the bottom and threaded at the upper end into the lower end of the bottom cone, serves as a base on which the compression spring 19 rests. In some cases, a tubing centralizer 28 is attached to the tubing near or adjacent to one or both of the cones to center the tubing and cones in the hole and provide a uniform annular space between the base of cones 14 and the well wall 25. A circulation joint 29, having internal ports 30 which are rotated by the upper end 12' of the tubing into alignment with external ports 31 on the lower end 12" of the tubing to provide a fluid bypass as described hereinafter, may be installed in the tubing above the anchor or tubing centralizer 28. This circulation joint is typically installed in the tubing string at a position such that when the tubing is at its maximum depth in the well, the circulation joint will be above the granular sealant and within the casing.

In operation, the cone or cones are first set in the bed of granular material 11 either by first depositing the granular material in the well and then jetting the lower end of the tubing into the bed, or by first lowering the tubing into the well until the lower end is located at the desired elevation and then depositing the sealant in the annulus 24 around the tubing. In the latter procedure the granular material may be allowed to bridge above the upper cone and leave an open hole below the packer or the tubing may be rotated as the particles of sealant settle through any liquid or other fluid in the well to prevent bridging of the particles and fill the well with the sealant from the bottom to the desired elevation. Where, as is the usual case, the formations penetrated by the well are to be treated at more than one elevation, the tubing is desirably first lowered into the well by either method so that the lower end of the tubing, particularly nipple 27, is at the elevation of the lowest zone to be treated. After locating or spotting the tubing at the desired elevation and then allowing the sealant particles to settle so that they are compact around the upper cone, the granular material is wedged in the annulus 24 between the cone or cones and the well wall. This is accomplished preferably by lifting the tubing to compact the particles opposite the upper cone above base 14. The granular sealant may also be wedged between the cone l3 and the well wall 25 by injecting a non-penetrating liquid down the annulus 24 and by other means. This non-penetrating liquid, which in the hydraulic fracturing process may be part of the fracturing fluid itself, is preferably a viscous liquid like drilling fluid having practically no fluid loss through the bed of granular material. Where the ratio of small particles in the bed of sealant is low, bridging agents may be included in this non-penetrating liquid to assist in building up a filter cake. With the upper cone wedged in the well, the non-penetrating liquid is displaced out the lower end of the tubing to form a filter cake in and compact the sealant particles round the tubing outlet. As pressure on this non-penetrating liquid rises, the particles above the base 14 between the upper cone and the well wall are further compacted anchoring the tubing so that it cannot be lifted out of the well by the application of fluid pressure below the packer. When the tubing is thus anchored and the annulus sealed, the fracturing fluid, which may as indicated be the same or similar to the non-penetrating liquid, is injected into the tubing and displaced out the lower end thereof. The circulation joint 29 may also be opened by rotating the tubing so that the treating fluid may be pumped down both the tubing and the annulus. It builds up a high pressure below the packer in the isolated section and eventually, when the formation fracturing pressure is reached, a fracture 33 is produced in the formation 9 typically along a horizontal plane at about the elevation of the lower end of nipple 27. Any amount of the formation treating fluid may then be injected into the fracture depending upon the length of fracture or the extent of any other treatment desired.

When the first fracture has thus been completed, a plug, such as a hard rubber ball 22, is dropped into the tubing and pumped to the bottom with either the fracturing fluid or a follower liquid therefor. This ball strikes the constriction 21, forcing the sleeve valve down so that the openings 23 register with the wash-fluid conduits 15. The liquid flowing in the tubing is then diverted into the annulus 24 in the constricted area at the base 14 of the upper cone, thereby fluidizing the granular material in the annulus above the base of the cone. With this granular material fluidized, the tubing may be raised to any position at which its bottom outlet is at another desired elevation.

When the tubing has thus been raised to the desired location, the ball 22 holding the valve open is removed either by fast pumping to build a high pressure which discharges it through the constriction or by reverse circulation of the fluid; that is, by injecting fluid down the annular space and circulating it around the bottom of the tubing and up through the tubing to lift the ball to the surface. After the ball is removed from the tubing by reverse circulation, direct circulation is commenced again to displace the slurry of granular material out of the lower end of the tubing. The granular material is then again permitted to settle through the liquid around the upper cone preferably while the tubing is rotated. The

packer is again anchored in the well as by lifting the tubing and then the annular space surrounding the cones is again sealed as described above. A second fracture can then be initiated at the new location of the end of the tubing by injecting fracturing fluid into a section of the hole isolated on the bottom by the body of granular material and on the top by the packer seal. Any number of additional fractures or other well treatments can then be performed at spaced intervals in the same well by first releasing the tubing anchor or packer and then reseating it as previously described at any other desired location in the well.

From the foregoing it can be seen that various modifications in the above-described method and apparatus can be made without departing from the spirit of this invention. The invention should, therefore, be construed to be limited not by the above description, but only by the scope of the appended claims.

- Iclaim:

1. An apparatus for temporarily plugging an annulus between first and second conduits with granular material comprising a wedge on one of said first and second conduits, a constriction'in said annulus at the lower end first and second conduits forming an annular wedgeshaped opening for the deposition of a quantity of said granular material between said first and second conduits, a construction in said annulus at the lower end of said wedge, and a wash-fluid conduit terminating in said annulus adjacent said constriction for flushing said granular material from said annular wedge/shaped open ing.

2. An apparatus according to claim 1 including a quantity of said granular material in said annular wedgeshaped opening.

3. An apparatus for temporarily plugging an annulus between a well conduit and a well wall with granular material comprising a cone on and substantially coaxial with said conduit, the base of said cone forming an annular constriction with said well wall and the surface of said cone forming with said well wall an annular wedge-shaped opening for the deposition of a quantity of granular material, and a wash-fluid jet terminating in said annulus adjacent said constriction for flushing said granular material from said annular wedge-shaped opening.

4. A bridging plug for temporarily plugging the annulus between a first and a second conduit comprising a wedge On one of said first and second conduits in said annulus, said wedge and the other of said first and second conduits forming a constriction in said annulus, granular material in said annulus between said wedge and said other of said first and second conduits, and a wash-fluid conduit terminating in said annulus adjacent said constriction for flushing said granular material from said annulus.

5. A bridging tool for use in temporarily plugging the annular space between a well conduit and the wall of a well comprising a cone connected to the lower end of said well conduit, the base of said cone being larger than said conduit and forming an annular constriction in said annular space between said conduit and said wall, a wash-fluid conduit between said well conduit and the periphery of said cone at the base of said cone, a valve for closing said wash-fluid conduit, and means to open said valve and close the end of said well conduit for selectively injecting wash fluid through said wash-fluid conduit to remove granular material deposited around said cone.

6. A bridging tool for use in temporarily plugging the annulus between a well tubing and the wall of a well with granular material comprising a first cone connected at the apex end to said tubing, a second cone connected at the base end to the base of said first cone, an axial opening through said first and said second cones, wash-fluid conduits extending from said axial opening through one of said first cone and said second cone and terminating advalve means to close said wash-fluid conduits, and'means to open said valve and simultaneously close said axial opening so that wash fluid is selectively injected into said annulus through said wash-fluid conduits for fluidizing said granular material and unplugging said annulus.

7. A method of treating a formation penetrated by a well comprising first depositing a quantity of granular. material in said well, then jetting a conduit having a wedge-shaped enlargement on the outside thereofinto said granular material to produce a wedge of said granular material in the annulus between said wedge-shaped enlargement and the wall of said well, thereafter injecting a treating fluid into said formation, then flushing said wedge of said granular material from said annulus between said wedge-shaped enlargement and said wall of said well and finally removing said conduit from said well.

8. A method of treating a formation penetrated by a well comprising first depositing a quantity of granular material in said well, then jetting a conduit having a downwardly flaring wedge-shaped enlargement on the outside thereof into said granular material to produce a wedge of said granular material with a constriction at its lower end in the annulus between said wedge-shaped enlargement and the wall of said well, subsequently lifting said conduit to cause said bridging material in said wedge to bridge in said annulus, thereafter injecting a treating fluid through said conduit into said formation, then injecting a fluid into said annulus at said constriction to flush said wedge of said granular material from said annulus between said enlargement and said wall of said well and finally removing said conduit from said well.

9. A method of fracturing an open formation penetrated by a well at a multiplicity of locations comprising first depositing a quantity of granular material in said well to a depth above the top of said formation, then jetting a conduit having a downwardly flaring enlargement on the outside thereof into said granular material at a lower position while allowing said granular material to settle around said enlargement and produce a first wedge of said granular material with a constriction at its lower end in the annulus between said enlargement and the wall of said well, then lifting said conduit to cause said bridging material in said wedge to bridge in said annulus, thereafter injecting a first quantity of a fracturing fluid through said conduit into said formation below said first wedge at a rate suflicient to produce a first fracture in said formation, then injecting a fluid into said annulus at said constriction to fluidize said granular material above said constriction and flush said first wedge of said granular material from said annulus, subsequently raising the lower end of said conduit in said well to an upper position in said granular material, then allowing said granular material to again settle around said enlargement, after said granular material has settled, again raising said conduit to cause said bridging material to bridge in said annulus and produce a second wedge, thereafter injecting a second quantity of' fracturing fluid into said formation below said second wedge at a rate sufficient to produce a second fracture in said formation, then injecting a fluid into said annulus at said constriction to again fluidize said granular material above said constriction and flush said second wedge of granular material from said annulus, and flushing said granular material from said well.

10. A method of fracturing a formation penetrated by a well at a multiplicity of locations comprising depositing a quantity of granular material in said well to a depth above the top of said formation, jetting a conduit, having two oppositely disposed wedge-shaped surfaces with a common base thereon, into said granular material so that the bottom end is at a first location to produce wedges of said granular material in the annulus between said wedgeshaped surface and the wall of said well, lifting said conduit to cause said granular material in one of said wedges to bridge in said annulus, injecting a first quantity of a low-fluid-loss fracturing fluid through said conduit and jacent the base of said first cone and said second cone, 7 into said formation at said first location, closing the end of said conduit and injecting fluid into said annulus at tlon, and circulating fil1ld in said well to flush said granuthe constriction in said annulus between said base of said la! m terial from 581d well. wedge-shaped surfaces and said well wall to fluldlze said References Cited in the file of this patent granular material and release said conduit, raising said 6 UNITED STATES PATENTS conduit in said well while said granular material is fluidized so that the bottom end of said conduit is at a second 587'779 Bi T 1897 location in said well below said dc ni, allowing said fluidg a1 6: 5- 13;: ized granular material to again settle around said w g "5' 2,224,538 Eckel etal Dec. 10, 1940 shaped surfaces, lifting said conduit to cause said bridging 1o 2 356 769 Layne Apr 29 1944 material in said wedge to again bridge in said annulus, 2:651:369 Aha Sci- 8" 1953 injecting a second quantity of i fracturing fluid through 2,769,497 Reistle Nov. 6, 1956 said conduit and into said formation at said econd l ca- 2,774,431 Sherborne Dec. 18, 1956 UNITED STATES PATENT OFFICE I CERTIFICATE OF CURRECTION Patent No,-3;OO7,523 November 7, l96l I Renic Pi Vincent It is hereby certiiied that error appears in the above numbered patent requiring correction'and that the said Letters Patent shouldread as corrected below.

Column 4, line 29, for "round" read around column 5, line 23, strike out "a constriction in said annulus at the lower end" and insert in said annulus,.said wedge and the other of said line 27, for "construction" read constriction Y Signed and sealed this 10th day of April 19620 (SEAL) fittest:

ERNEST w. SWIDER V DAVID L. LADD Attesting Officer Commissioner of Patents UNITE-D STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Paieni; N01,, sgoo7 s2s November 7 1961 Column l line 29 for "round" 5,, line 23 strike out "a constriction in said annulus ai; the lower end" and inseri in said annulus said wedge and the Miner of said line 27 for "construction" read conswiction Signed and sealed this 10th day of April 1962,

(-QEAL) Atesi:

ERNEST W, SWIDER Aiiesting Officer DAVID L, LADD Commissioner of Patents

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