US 2754910 A
Description (OCR text may contain errors)
2 Sheets-Sheet l BALLS` mTRooucLo HERE J. V. DERRICK ETAL METHOD 0F TEMPORARILY CLOSING PERFORATIONS 1N THE CASING Filed April 27. 1955 July 17, 1956 147/1 l l y BYMM-MMLM lll/11 METHOD OF TEMPORARILY CLOSING PERFORATIONS IN THE CASING 2 Sheets-Sheet 2 Filed April 27, 1955 TO PUMP SKR R C E 0mm. TRE N E B o 3 www. G EK t M. A uw ,M .J Y O 5 l L a@ BALLS INTRODUCED HERE TO PUMP United States Patent C) METHOD F TEMPORARILY CLOSING PERFORA- TIONS 1N THE CASING James V. Derrick and Lloyd H. Kaltenberger, Breckenridge, Tex., assignors to The Chemical Process Company, Breckenridge, Tex.
Application April 27, 1955, Serial No. 504,212
8 Claims. (Cl. 166-1) This invention relates to oil and gas' well treating and more in particular to a method of temporarily closing perforations in the casing.
Heretofore it has been a practice in completing the oil and gas wells to set the casing, cement the same and then perforate the casing either by jet or bullet perforations opposite the producing formations. These openings in the well casing are of various sizes depending upon the method of perforating used.
In completing new oil or gas wells or recompleting old oil or gas wells it is often necessary to open new drainage channels in the producing formation to provide commercial production. In many cases casing has been set through the formation and the casing is perforated opposite the formation to allow oil or gas to come into the casing from the formation. The well may be treated either by acid treatment or hydraulic fracturing or by numerous other methods embodying the injecting of iluids or solids into the formation.
The material being injected into the casing and through the perforations in the casing does not distribute itself equally through all of the perforations and it has been found desirable to close those perforations through which the treating material is moving in order to force the treating material through other perforations thereby creating new drainage channels in the producing formation.
Heretofore there have been no known methods of temporarily closing these perforations selectively during the treating operation. v
It is an object of this invention to close the perforations in the casing in such a manner that only those perforations are closed through which the fluids forced down the casing are being injected into the formation.
It is also an object of this invention to have these closure means operated so that they may be readily removed.
This invention provides a method by which some of the perforations can be temporarily plugged during an injection of fluids or materials so that such fluids or materials are forced into the formation through other perforations which remain open, thus creating several new drainage channels in the formation.
These and other objects of this invention will become apparent from the preferred embodiment of the invention which is described hereinafter with particular reference to the drawings wherein:
Fig. l is a diagrammatic sectional view of a perforated oil Well.
Fig. 2 is a diagrammatic sectional view of an oil well with a packer set near the end of the tubing.
Fig. 3 is a diagrammatic sectional view of an oil well with the tubing in place.
Fig. 4 is a plan View, partially in section of a coated spherical plug.
Fig. 5 is a plan view in section of a hollow spherical plug.
Fig. 6 is a plan View of a double conical plug.
Fig. 7 is a plan view of a flat plate plug.
Fig. 8 is an edge view of Fig. 7.
In the preferred embodiment of the invention shown in Fig. l, the casing 10 is run to the bottom of the well and cemented around the outside, at least to a distance above the producing strata, as shown. The casing and the cement 11, are then perforated by any one of various means. If the well does not immediately come into production it is then common practice to treat the well in such a manner as to open up the producing formation to allow a ready passage for the oil to flow into the well. This is accomplished by treating by acidizing, hydraulic fracturing or other methods which comprise forcing a treating material 12 down the casing 10 and into the producing formation through the perforations 13, 13 in the casing. Exceedingly high pressures are sometimes used in this operation, in the neighborhood of 10,000 lbs. per square inch, is not unusual, and it is recognized that the material will flow through certain of the perforations more readily than it will flow through others. It is apparent then that only that part of the formation which is adjacent to these perforations is being subjected to the treatment. It therefore becomes desirable to close off these perforations during the treating operation selectively, that is, those perforations through which the liquid is flowing should be closed so that the liquid will act on the formation adjacent to the other perforations.
In order to accomplish this, balls 14, 14 are introduced into the material moving in the casing 10 and are carried by this material down to the point where the material flows through the perforations 13. The balls are then held by the uid pressure in the casing, which is greater than the pressure in the formation, against the perforations in the casing, thereby effectively closing these perforations until such a time as the pressure differen` tial is reversed and the pressure in the formation becomes greater or equal to that in the casing, at which time the balls are forced free of the perforations and drop to the bottom of the well and remain there, as shown at 15, 15 in Fig. l. This preferential closing of the perforations in the casing allows equal treatment of the strata through the entire distance of the perforations, for example, the perforations in the lower part may be closed rst, and then progressively those other perforations carrying most of the treating material from the casing.
It has been found that plugs having a density greater than the treating material being injected into the producing formation are most satisfactory, so that when the flow is reversed and the plugs fall to the bottom, due to their greater density, they remain there, but plugs of a density less than the material in the casing may be used and these plugs will rise with the ow from the well and be removed at the well head.
' Where balls have been used in the preferred embodiment of this invention other shapes may also be used Y satisfactorily. Solids having conoidal shapes other than spherical (show-n in Figs. 4 and 5), such as elliptical, or a double conical (shown in Fig. 6) may also be used. Flat plates (shown in Figs. 7 and 8) which will deform to take the curvature of the casing under the pressures exerted at the bottom of the well also have been found to be satisfactory. it is therefore apparent to one skilled in the art, that plugs of many different shapes may be used.
These plugs must be of such a nature and such a size that they will not go through the perforations and that they may be readily removed from the perforations by the release of pressure in the casing. They must be made of a material that will not deform to an extent so as to become permanently lodged in the perforations. It is necessary in all of these modifications that the materials used in making the plugs be of such a nature as not to be attacked appreciably by the treating material. That is, if hydrochloric acid is being used, aluminum or magnesium plugs are not satisfactory, as they will be subject to attack by the acid. In the hydraulic fracturing treatment using an oil base to suspend the sand, plugs of magnesium or aluminum alloys can be used. It has been found most satisfactory to use an aluminum alloy, steel, bronze, 'laminated plastic, or hard rubber etc. These plugs may be so-lid or they may be constructed in two halves so as to form a hollow center (shown in Fig. principally to control the apparent density of the plugs when suspended in the treating material. The plugs may also be treated on the surface with an inert deformable material (shown in Fig. 4) such as neoprene latex which would act as a gasket when the plugs are brought into contact with casing perforations. Also hard metal plugs 16 (shown in Fig. 4), may be coated with a softer metal 17 which would deform under extreme pressure experienced in the casing to assist in plugging the perforation.
Plugs may be introduced into the bottom of the well suspended on a wire line and attached thereto by an easily broken means. The uid may then be pumped down the casing and when it is desired to close off the perforations opposite the more ,permeable part of the formation, the wire line is raised allowing the plugs to be carried by the uid stream against the perforations in the casing and thereby effectively closing the same. They are held in place as pointed out above by lthe difference in pressure inside and outside the casing.
The well in addition to the casing may have therein a string of open ended tubing 18 terminating in the neighborhood of the perforated area, as shown in Figs. 2 and 3 and may have a packer 19 sealing off the annulus between the tubing and the casing above the perforations as shown in Fig. 2. The treating material 12 is pumped down the tubing and ilows through the perforations into the adjacent formation. The plugs are admitted through the lubricator 20 and are allowed to move down the tubing 18 with the treating material where they are forced selectively against those perforations 13 through which the treating material is moving as shown at 21, leaving open those perforations through which the treating material is not being injected. These plugs seal off the said perforations just so long as the pressure within the tubing and the casing is greater than the pressure in the formation. When the pressure is released at the top of the tubing the plugs will be released from the perforations andthe ow will be established.
The method shown in Figs. 1, 2 and 3, all represent modifications of this invention, which comprises basically the introduction of plugs into a casing during treatment of the producing formation to selectively close the perforations in the casing, closing off those perforations through which the treating `material is most rapidly 'being injected. The invention is not limited by he type of plug but comprises basically the selective closing of -such `perforatio-ns. This closing is `of na temporary nature yand only is maintained vduring the injecting of the treating material into the permeable formation, and when the pressure is released the plugs are self-acting and drop clear of the perforations so as to allow flow from the producing zone or formation. The methods shown in Figs. l, 2 and 3 are all similar insofar as the plugs are pumped down the well with the treating material into the general proximity of the perforations in the casing and seal olf those perforations through which the material is being injected most rapidly into the adjacent formation. The plugs are carried by the uid stream to the particular perforation through which the treating material is entering the formation and the sealing action can be determined readily by the increase in pressure at the well head. The plugs can be admitted or introduced as desired and move readily with the material traveling at a rate such that it can be easily determined when they will arrive at the sealing position and the plugs can be admitted one or two or as many at a time as needed according to the pressure rise and fall within the casing. During the pumping of treating material the pressure will constantly rise until such time as the material is injected into the formation. It will then probably drop, indicating that the formation has broken and at this time plugs will be introduced into the fluid stream to plug the perforations opposite the existing permeability.When this occurs the pressure will again rise, indicating that the pressure is being exerted against another part ofthe formation where little or no permeability exists. When this part at the formation breaks, the pressure may again drop, at which time more plugs will be admitted to plug those perforations -through which iiuid is now moving. This procedure can be followed until as many formation breaks are obtained as desired, or until all of the perforations are plugged. This allows, for the first time, control of the fluid entry into the formation of a treating material by the sealing off of perforations adjacent to the more permeable part of the producing formation.
Heretofore the only means of plugging the perforations in the casing consisted of a cementing operation which -was of a permanent nature. The sealing means introduced by the method disclosed herein is of such a nature that it can be readily removed without expense or without introducing any undesirable materials into the permeable formation.
While certain arrangements and specific details have been set forth in this specification to illustrate the invention it is clear that one skilled in the art may vary the specific details without departing from the spirit of the invention which is only limited by the claims attached hereto, wherein:
What is claimed is:
l. A method of temporarily plugging the perforations in a casing which has been set in a bore hole, which comprises: injecting a tiuid under pressure into the casing to cause a ilow of iiuid through those perforations which are adjacent portions of a formation in which Kthe back pressure is less than the pressure of the stream, adding plugging elements which are larger than the perforations in the casing to the stream while maintaining the pressure on the stream whereby certain of the plugs will be caused by the flow of iiuid to lodge against said perforations through which the liquid has been passing and seal the same.
2. A method of treating a formation in which a casing has been set and perforated, the formation having such characteristics that a liquid will pass through only certain of the lperforations into the formation to treat the formations opposite said perforations, which comprises: introducing into the well a formation treating material containing plugging elements which are larger than the perforations and which will seat themselves only against the above mentioned certain perforations through which the treating material is passing to essentially seal said perforations in the'casing and cause said stream of treating material yto pass through other perforations which have not been sealed off, by raising the pressure on said Stream until said treating fluid has been forced through all of the perforations. v
3. A method as claimed in claim 2, wherein said plugging elements are spherical.
4. A method as claimed in claim 2, wherein said plugging elements are spherical and formed of a hard material having a thin coating of softer material on the surface thereof.
5. A method as claimed in claim 2, wherein said plugging elements are made from a light metal alloy.
6. A method as claimed in claim 2, wherein said plugging elements are hollow steel balls.
7. A method as claimed in claim 2, wherein said plugging elements are made from a plastic substance selected from the group consisting of thermo-plastic and thermosetting resins. g
8. A method as claimed in claim 2, wherein said ele= ments are polygonal in shape and insoluble in the treating material.
References Cited in the file of this patent UNITED STATES PATENTS 2,699,212 Dismukes Ian. 11, 1955