US2775304A

US2775304A - Apparatus for providing ducts between borehole wall and casing

Info

Publication number: US2775304A
Application number: US355770A
Authority: US
Inventors: Zandmer Solis Myron
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-05-18
Filing date: 1953-05-18
Publication date: 1956-12-25
Anticipated expiration: 1973-12-25

Description

Dec. 25, 1956 s. M. ZANDMER 2,775,3 4

APPARATUS FOR PROVIDING DUCTS BETWEEN BOREHOLE WALL AND CASING Filed May 18, 1953 /Nl/fN TOR 5on5 Mme/v ZANDMER AT'T'GRNE Y.

United States Patent .0

APPARATUS FOR PROVIDING DUCTS BETWEEN BOREHOLE WALL AND CASING Solis Myron Zandmer, Calgary, Alberta, Canada Application May 18, 1953, Serial No. 355,770

2 Claims. (Cl. 166-100) This invention relates to a novel apparatus for providing ducts for the flow of fluids between selected earth strata and the interior of a bore hole casing or liner.

Heretofore, bore hole casings have been set in drilled boreholes by a cementing process in which fluidcement is forced down through the casing and then upwardly around the outside of the lower portion of the casing to fill the space between the outside of the casing and the surrounding earth. It has then been customary to perforate the casing and the surrounding cement at the levels of producing strata by means of horizontal drilling or by means of gun-type perforators which fire a projectile through the casing and cement to form passageways therethrough. Said known methods and apparatus have created various difficulties such as a shattering of the cement, destruction of the sealing bond between the casing or liner and the cement, and the formation of cracks in the cement making said cement subject to destructive attack by acids subsequently introduced to acidize and improve the flow of fluids from productive strata.

A novel apparatus for establishing communication between producing strata and the interior of a cemented bore hole casing or liner is shown in my joint application with one, Albert Joseph Jacobs, Serial No. 285,201, filed April 30, 1952, nowPatent No. 2,707,997. Also shown in my copending application Serial No. 294,251, filed June 18, 1952, now patent No. 2,708,000, is improved apparatus for so establishing communication between producing strata and the interior of a cemented bore hole casing or liner.

It is an object of this invention to provide an apparatus for establishing communication between producing strata and the interior of a sealed bore hole casing or liner.

It is another object of this invention to provide ducts between producing strata and a bore hole casing or liner which do not damage in any manner the effectiveness of the seal between the casing or liner and the surrounding earth formations.

it is a further object of this invention to avoid puncturing or perforating a casing or liner after it has been sealed and hence avoid damaging the sealing material or the bond between the material and the bore hole casing or liner and/or the bond between the material and the bore hole wall.

It is a further object of this invention to provide a bore hole casing or liner with a plurality of laterial ductforming devices at various levels operable by pressure within the casing or liner to establish or position the ducts between the casing or liner and different strata of the surrounding limestone formations without damaging the seal between the casing or liner and the surrounding formation and between the various levels or strata.

It is a still further object of the invention to provide duct-forming devices to be attached to a bore hole casing or liner adapted effectively to be moved outwardly by pressure to engage the wall of the bore hole and form cores between the casing or liner and the wall of the bore 2,775,304 Patented Dec. 25, 1956 'ice.

hole for a sealing material to be applied therebetween, parts of the devices being made of a material which is dissolved in acid so that the cores may at least in part be removed to provide ducts or passages affording communication between the interior of the casing and the wall of the bore hole.

Other objects and advantages of this invention will become readily apparent from the following detailed description of a preferred arrangement of apparatus and its method of use.

According to the invention, plungers movably supported in bushings fixed in holes through the casing are moved outwardly to engage the wall of the bore hole and provide cores surrounded by the sealing material when applied, and after the material has set, the cores are removed to provide passages through the sealing material and the bushings, thus affording communication between the wall of the bore hole and the interior of the casing.

in the accompanying drawing forming a part hereof:

Figure 1 is a vertical section view partly cut away and partly diagrammatic of a bore hole provided with a casing sealed in accordance with this invention;

Figure 2 is a horizontal section view through the casing and through a duct-forming device, the device being shown in its initial position, before projection into engagement with a producing stratum;

Figure 3 is a view similar to Figure 2, on a reduced scale, but showing the duct-forming device in its extended form; and

Figure 4 shows the duct-forming device in its final form, after parts have been dissolved to provide communication between the interior of the casing and the wall of the bore-hole.

Referring now to the drawing, a bore hole 10 is drilled in the earth and limestone by any conventional apparatus. In boring wells through limestone formations, for example, the bore hole may be approximately nine inches in diameter and usually has a substantially smooth and regular surface.

A bore hole casing or liner 12 is positioned in the bore hole, and may be formed of steel or aluminum tubing of about seven inches outside diameter. This provides an annular space of about one inch across between the outer surface of the casing 12 and the wall of the bore hole; the annular space is filled with a sealing material layer 13 which is bonded to the wall of the bore hole and to the casing.

The sealing material comprises a suitable plastic, cement, or other such material as will not be dissolved by the acids used to acidize or treat the well, or by the oil, gas, or other input materials used to increase the productivity of oil or gas bearing strata.

For limestone, the acidizing agent currently used for increased productivity is hydrochloric acid. For the purpose of this invention, hydrochloric acid may be used for acidizing; and the sealing material 13 may be a phenol resin type plastic such as is not attacked by the acid.

Earth formations usually have a plurality of oil or gas producing bands or strata, indicated in the drawing by the numerals 11. Some of the strata may be more porous than other adjacent strata. The porosity of the individual strata may be determined by analysis of specimen cores or by electrical testing apparatus, and the, permeability of each porous band of formation or stratum is expressed in terms of millidarcies. Where a bore hole traverses several strata of different porosities and permeabilities, and the strata are to be treated by acids or other chemicals, it is desirable that the seal 13 between various strata be maintained unbroken so that upon application of acids under pressure there will be no leakage outside of the casing 12 from one stratum 11 to another, stratum of greater porosity or permeability. In actual practice the strata may be found to be of small thickness and possibly spaced only a few feet apart.

The section of well casing or liner 12 adjacent the strata 11 is provided before its introduction into the bore hole with aplurality of duct-forming devises mounted in thewall of thecasing 12 at levels to correspond with the indicated levels of the'strata 11 to be tapped.

One such duct-forming device will now be described first with reference to its original position as shown in Figure 2. The device 15 comprises a bushing 16 mounted in an opening in the casing 12 as by threads 1]. The outer end of the bushing may be provided with recesses 18 to permit application of a spanner wrench to screw the bushing into the threaded opening of the casing 12. The bushing is such that, when applied, it does not project into the casing, but projects outwardly.

The bushing 16 is counter-bored as at 2 9 to define a shoulder or stop 19 rearwardly of the forward end of the bushing. Threaded into the counter-bore of the bushing is a tubular insert 21. The insert is preferably made of two parts, 21A and 21B. The part 21A may be made of steel, and the part 2113 is made of a die-casting formed of pot metal containing zinc or of any other metal or substance easily dissolved by conventional acids used in acidizing, for example, hydrochloric acid. The part 21A of the insert is preferably locked to the bushing by a steel pin 34.

Slidable in the insert 21 is a member or plunger 22. The rearward end of the plunger is formed with an annular enlarged portion or shoulder 23. The plunger is in sealed sliding engagement with the bushing 16, forwardly of the shoulder 19, a conventional 0 ring seal 24 being provided for that purpose. The plunger 22 may be made of pot metal containing zinc or of any other metal or substance easily dissolved in the conventional acid used. The plunger 22 is releasably held or locked in the bushing 16 by shear pins 25. The pins are chosen to shear, and release the plunger 22 for outward movement, upon a predetermined pressure being applied to the inner end of the plunger.

Means are provided to prevent movement of the plunger 22 rearwardly in the bushing 16 after the shear pins 25 have been severed by pressure and the plunger has been moved forwardly to engage the wall of the bore hole. Thus, a wedging device is shown, comprising a plurality of balls 26 held in engagement with a ramp 27 formed on the insert 21A, by a steel washer 28 urged toward the balls by a spring ring or Washer 29 tensioned between the washer 28 and the shoulder 19. The arrangement is-such that the balls are always in contact with the ramp 27 and in contact with the plunger 22, so that the plunger is incapable of movement toward the casing 12 away from the wall of the bore hole 11, but is capable of movement outwardly from the casing 12.

A vent or bleed port 36 is provided through the insert 21, the vent opening at one end into the annular space between the insert 21 and the plunger 22. The outer end of the plunger 22 may be provided with a ring 31 of resilient material, for instance rubber or Neoprene, adapted to engage the wall of the bore hole. Obviously, it is desirable that the outer end of the plunger 22 should engage the wall of the bore hole as tightly or intimately as possible. The wall is not always smooth, even if the hole is diamond-drilled, so that a resilient washer will best serve to provide a good seal between the plunger and the wall of the bore hole. If the plunger 22 is hollow, as shown, a hole or passage 35 is preferably provided at the inner end.

The plunger 22 is adapted to be moved by fluid pressure between its initial position within the casing 12, as shown in Figure 2, and its extended position, in contact with the wall of the bore hole, as shown in Figure 3. The length of the plunger is so. chosen that its outer end, more particularly the rubber ring31, will engage the wall of the bore hole before the shoulder or stop 23 engages the balls 26. Should the wall of the bore hole, facing the outer end of the plunger be not smooth, that is, if it is locally recessed because of parts of the formation being chipped off, the efifective length of the plunger might not be sufficient to enable its to engage the wall of the bore hole when fully moved outwardly. The presence of the shoulder 23, therefore, will prevent the plunger from being forced out of the bushing entirely.

The bottom of the casing 12 being closed by a releasable valve or plate 29, a predetermined fluid pressure applied within the casing acts on the plungers 22 to sever the shear pins 25 and push the plungers outwardly toward the wall of the bore hole to engage the same. The pressure required for this action depends on the shearing strength of the shear pins 25.

it is also possible that the plunger 22 may be made of a hard wax or some other material which could be melted by heat or be easily dissolved by oil or by acids.

The method of operation of the apparatus illustrated and described will now be explained. The bore hole drilled in the limestone 11 is surveyed by conventional methods to determine both the porosity and permeability and actual level of the several porous strata 11 above the bottom of the hole 10. The casing 12 is then prepared with the duct-forming devices 15 secured therein at the levels corresponding to the levels of the several strata to be tapped. The casing, with attached duct-forming devices, is then lowered into the bore hole until it engages the bottom, presenting the devices 15 to the several strata to be tapped. Fluid under pressure is then pumped into the casing until the pressure is sufiicient to cause the outward forces to shear the pins 25 and push the plungers 22 outwardly so that they, more particularly the resilient rings 31, tightly engage the wall of the bore hole. The locking device, balls 26, prevents the plungers 22 from subsequent return movement back toward the casing 12. Next, a sealing material, under a greater fluid pressure, is forced into the casing so as to open or force downwardly the releasable bottom closure 29 from its initial position, shown as 29a, to a position below the lateral passages or ports 30 through the casing, the fluid sealing material then passing through the passages and upwardly, filling the annular space between the outer surface of the casing and the wall of the bore hole to the level required. The duct-forming devices 15 are thus surrounded by the sealing material and they thus provide cores or ducts through the layer or wall of sealing material.

After the sealing material has finally set and has become bonded to the outer surface of the casing, to the wall of the bore hole, and to the bushing and to that part of the plunger 22 which projects out of the bushing, acid, such as hydrochloric acid, is pumped into the casing 12. The acid dissolves the plunger 22, and the part 21B of the insert, and a passage shown as in Figure 4 through both the bushing 16 and the layer 13 of sealing material is formed, thereby alfording communication between the inside of the casing 12 and the wall of the bore hole. As a possible alternative, an acid jet gun may be lowered opposite each band of plungers 22 and acid sprayed on the plungers. If the plungers are made of a hard wax, hot oil or other solvents may be spread against them to melt or dissolve the same.

It may be found possible to apply the sealing material before the plungers are moved outwardly to engage the wall of the bore hole, but there appears to be no advantage to be gained by so doing; only experience would show whether it would be possible, or desirable.

It is desirable to make the bushing 16 of steel rather than of pot metal, as steel is harder and is better able to withstand deformation or wear as when the casing is being lowered into the hole. Moreover, the effective passage through the layer of the sealing material is determined by'theiuside diameter of the rubber ring, so that no useful purpose would be served by dissolving the bushing.

What I claim is:

1. In apparatus for use in a bore hole traversing a porous stratum to be tapped, a duct-forming device adapted to be supported by a bore hole casing of smaller diameter than that of the bore hole to provide an annular space between said casing and the wall of the bore hole adapted to receive a sealing material; said device comprising, an open-ended tubular bushing mountable in a hole through the wall of said casing, a plunger mounted in said bushing for outward movement to engage the wall of the bore hole to provide with said bushing a core to be surrounded by the sealing material, means releasably locking said plunger against outward movement in said bushing, and means constraining said plunger to an outward movement, said plunger being of a material dissolvable in acid whereby said plunger may be dissolved to provide a passage between the interior of said casing and the wall of the bore hole.

2. In apparatus for use in a bore hole traversing a porous stratum to be tapped, a casing of smaller diameter than that of the bore hole to provide an annular space between said casing and the wall of the bore hole adapted to receive a sealing material, and a duct-forming device supported by said casing; said duct-forming device comprising, an open-ended bushing mounted in a hole in the wall of said casing and projecting outwardly therefrom, a

tubular insert in said bushing projecting into said casing and defining with said bushing a bore, a plunger mounted in said bore for outward movement to engage the wall of the bore hole to provide with said b ushing a core to be surrounded by the sealing material, means releasably locking said plunger against outward movement, and means constraining the movement of said plunger to an outward movement, said plunger and at least part of said insert being of a material dissolvable in acid, and said plunger when dissolved providing a passage afiording communication between the interior of the casing and the wall of the bore hole.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,393 Kurtz et al. July 24, 1951 2,033,562 Wells Mar. 10, 1936 2,186,349 Simmons Jan. 9, 1940 2,196,652 Baker Apr. 9, 1940 2,236,836 Prutton Apr. 1, 1941 2,330,144 Powers Sept. 21, 1943 2,540,123 Kinley Feb. 6, 1951 2,546,669 Kirby Mar. 27, 1951 2,563,284 Seay Aug. 7, 1951 2,707,997 Zandmer et al May 10, 1955 2,708,000 Zandmer May 10, 1955