Sand Consolidation By Adhesive Agent And Particulate Pack

Abstract

The flow of sand into a well is controlled by injecting into the producing zone a sand consolidation adhesive agent which will cause consolidation of the sand particles by sticking one to another, and forcing a particulate material into the producing zone after the injection of the sand consolidation adhesive agent, and producing through the consolidated sand and particulate material. A screen may be placed in the particulate material or above the particulate material to aid in mechanically supporting the particulate material and holding the particulate pack in place. The method for controlling the flow of sand into a well is especially suitable for a cased well which has been perforated and provides an essentially fail safe consolidation method.

Parent Case Text

This is a continuation of application Ser. No. 164,751, filed July 21, 1971, now abandoned.

Description

BACKGROUND OF THE INVENTION

1 . Field of the Invention

The present invention is directed to a method for controlling the flow of sand into a well. More particularly, the present invention is directed to a method of sand consolidation wherein a sand consolidation adhesive agent is injected into the producing zone of the well and followed by a particulate material being forced into the producing zone to form a particulate pack which is held mechanically in place preferably by a screen in the particulate material and in communication with the producing string.

2. Prior Art

U.S. Pat. No. 3,336,980

SUMMARY OF THE INVENTION

The flow of sand into a well is controlled by injecting into the well and into a producing zone a sand consolidation adhesive agent which will cause consolidation of the sand particles by sticking the particles one to another, forcing a particulate material into the producing zone after the injection of the sand consolidation adhesive agent, and then producing through the consolidated sand and the particulate material. The loose sand or unconsolidated sand in a well or surrounding a casing in a well in a producing zone is consolidated by a sand consolidation adhesive agent and then mechanically held in place by the particulate material which forms a particulate pack. It is preferred to force the particulate material into the producing zone at high pressures after the sand consolidation adhesive agent has already been injected into the zone at low pressures so that high permeability fingers of particulate material extend out into the consolidated zone and possibly into the unconsolidated producing zone. A screen is placed in the particulate material or above the particulate material to aid in mechanically holding the particulate pack in place.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an idealized gravel pack;

FIG. 2 is a schematic view depicting the actual results of a gravel pack;

FIG. 3 is a schematic view of an idealized plastic treatment for sand consolidation;

FIG. 4 is a schematic view depicting the actual results of a plastic treatment for sand consolidation;

FIG. 5 is a schematic view of an idealized resin-sand pack;

FIG. 6 is a schematic view depicting the actual results of a resin-sand pack;

FIG. 7 is a schematic view of a perforating gun for perforating the casing in a well;

FIG. 8 is a schematic view wherein a sand consolidation adhesive agent is injected into a producing zone of perforated casing in a typical well;

FIG. 9 is a schematic view of the forcing of a particulate material into a producing zone according to the present invention;

FIG. 10 is a schematic view of a well consolidated according to the present invention having a slotted screen in the casing;

FIG. 11 is a schematic view of a well consolidated according to the present invention wherein the particulate material has been forced into the producing zone at pressures high enough to cause fingers of particulate material to extend through the consolidated zone; and,

FIG. 12 is a schematic view of a multiple completion well employing the sand consolidation method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be best illustrated by comparison to some of the known industry methods for sand consolidation.

Referring to FIG. 1, an idealized gravel pack method for sand consolidation is disclosed. A well casing 10 which may or may not be cemented in place is positioned in producing zone 12. The well casing 10 is perforated and has perforations 13, 14, 15, 16, 17, and 18 as illustrated. A screen 19 is in communication with a producing string and has a plurality of slits 20 in the screen 19. Packed around the screen 19 is gravel 21. The gravel 21 is graded in size and is of a size larger than the fine unconsolidated sand in the production zone 12. A typical gravel 21 would be such that thirty percent would pass through 40 mesh screen, 40 percent through a 50 mesh screen, and about 30 percent through a 60 mesh screen.

As depicted in FIG. 2, the actual results of most industry gravel packs are in no way near that of the idealized gravel pack depicted in FIG. 1. A casing 10 which has been cemented in place by cement 11 is in a producing zone 12. The cemented casing 10 is then perforated with perforations 23, 24, 25, 26, 27, and 28. However, in any perforation operation, certain of the perforations are immediately plugged or become plugged. Perforations 24 and 26 are shown plugged by debris 29. The debris 29 may be portions of the casing 10 or the cement 11 or the perforating means whether it be a shaped charge, bullet projectile, or the like. Furthermore, a perforation may be plugged with solid particles from the fluid in the well when perforating, especially if that fluid is the filter-cake building mud used to drill the well; or a perforation may be plugged with fine particles from the wash water or workover water even used in the well after being perforated. These particles are shown as fines 30 in perforation 23. Production is thus limited to possibly one or several gravel packed fingers 31 extending into the producing formation 12 and maintaining flow through one or more perforations such as 25, 27 and 28. The producing channels 31, however, are of limited productivity since they are only of moderate permeability due to the nature of the gravel 21 used in a gravel pack. The inherent nature of a successful gravel pack requires graded sand fine enough to prevent the finer unconsolidated sand from the producing zone 12 flowing into the gravel pack and plugging the gravel pack. It must also keep sand out of the well and producing string in communication with the screen 19. The restricted productivity of the gravel-packed flow channels is most pronounced at the perforation of the casing and cement. In this portion of the perforation, there is usually a restricted area of one-quarter square inch or less through a length of about 2 inches, which is the length through the casing wall and cement sheath.

Referring to FIG. 3 is an idealized plastic treatment for sand consolidation. In a well 40 which may be cased and cemented (not shown) as desired in communication with a producing zone 42 are perforation fingers 43, 44, 45, 46, 47 and 48. The formation sand in the producing zone 42 is consolidated with a resin 49 pumped from the surface into the producing zone 42 through the perforations 43 - 48, inclusive.

The actual results of an industry plastic treatment is depicted in FIG. 4. The well 40 is in communication with a producing zone 42. The well casing or tubing or multiple completion equipment (not shown) in the well 40 is perforated at perforations 43, 44, 45, 46, 47, and 48 adjacent to the producing zone 42. The consolidation resin 49 is introduced through the perforations. However, debris usually plugs certain of the perforations, for example the debris 50 plugging the perforations 44 and 46. The extent to which the resin 49 extends out into the producing zone 42 and consolidates the loose sand will depend upon the permeability of the formation 42 adjacent each of the perforations as well as the condition of a certain perforation as to whether that perforation is free for resin 49 to flow through that certain perforation. The pressure differentials may be such that the resin 49 penetrates only a very short distance through a particular perforation and out into the formation. This is depicted in a shallow and weakly consolidated portion 51 through perforation 43. Upon attempting to produce from zone 42, there are several points of failure which may immediately fail. The debris 50 may flow into the well 40 or the weakly consolidated portion 51 may break due to its shallow penetration.

Still another approach to sand consolidation is depicted in FIG. 5 in the resin-sand pack. A casing 60 is cemented into place by cement 61 in a producing zone 62. The well casing 60 is perforated at the perforations 63, 64, 65, 66, 67, and 68. Introduced through the perforations 63 - 68, inclusive, and out into the producing zone 62 having fine, unconsolidated sand is a resin-coated large sand 69 which has been prepared at the surface and pumped into place.

However, the actual results of a resin-sand pack is depicted in FIG. 6. Here, the casing 60 cemented into place by cement 61 in the producing zone 62 has perforations 73, 74, 75, 76, 77, and 78, respectively. Perforations 74 and 76, however, are plugged with debris. Thus, when the resin coated sand 69 is pumped through the casing 60, the resin coated sand 69 may not be able to enter the producing formation 62 through perforations 74 or 76 at all. In other perforation the resin coated sand 69 may only enter the perforation, such as 73, and not enter the producing zone 62 at all. As to other perforations, the resin coated sand 69 flows out into the producing zone such as through the perforations 75, 77 and 78, respectively. Hence, the resin-sand pack has likely points of failure immediately, or after a small amount of production, at perforations 73, 74, or 76. Furthermore, during the injection process, formation sand becomes consolidated with the plastic leached out of the resin pack. Resin designed to consolidate large pack sand leaves a very low permeability at the inflow face 79, since this resin on fine formation sand leaves very little space remaining for producing fluids to flow.

According to the present invention, referring to FIG. 7 of the drawings, a well which may be cased by casing 110 and cemented into place by cement 111 is perforated in a producing zone 112. The perforations 113, 114, 115, 116, 117, and 118 are produced by a perforating means 119 being placed in the well adjacent the producing zone 112. As shown in FIG. 7, a varying amount of debris remains in each of the perforations 113 - 118, in the newly perforated tubing or casing 110. The debris in the perforations may be removed in part by a washing step wherein by circulation and reverse circulation sand and debris is washed out of the well.

Referring to FIG. 8, through a tubing 120 in the casing 110, a sand consolidation adhesive agent 121 is injected into the producing zone 112. The debris in some of the perforations and the permeability of the producing zone 112 behind the perforations makes the sand consolidation adhesive agent 121 flow out into the producing zone 112 in a manner other than that which is ideal. The sand consolidation adhesive agent 121 may be a thermoplastic resin which is injected in two steps, one being the resin per se and the other injecting stream being a catalyst or setting or curing agent to aid in the polymerization of the thermoplastic resin or the adhesive agent 121 may be injected so that the thermoplastic resin and setting agent are injected together initially followed by an after-flush stream for placement of the resin and/or to maintain the permeability within the producing zone 112. While thermosetting resins are preferred, any adhesive agent may be used which will consolidate the sand particles by sticking one to another. Phenol-formaldehyde and epoxy-type resins have been successfully used. Specific resins and their specific steps for injection are set forth in U.S. Pat. No. 3,336,980 and the patents referred to therein.

After injecting the sand consolidation adhesive agent 121, particulate material 122 is injected through the pipe 120, as shown in FIG. 9, and forced into the producing zone 112 after the sand consolidation adhesive agent 121 using pressures higher than those used in injecting the adhesive agent 121. The particulate material 122 is preferably a large gravel having a smooth surface to produce a high permeability mechanical support although other particulate material having sufficient strength to withstand the pressures and give mechanical support may be used. For example, a gravel wherein one hundred percent passes through a six mesh screen but essentially none will pass through a 12 mesh screen is preferred. The gravel 122 after being forced into the producing zone 112 thus mechanically supports the sand consolidation adhesive agent 121 and maintains it in place as well as mechanically supporting points of weakness where little or no adhesive agent has penetrated the producing zone 112. The gravel 122 may be introduced after both streams of the sand consolidation adhesive agent has been injected into the producing zone 112, or more preferably, the gravel 122 is injected into the second stream of the adhesive agent after an initial portion has been introduced, thus being in the latter portion of the catalyst or after-flush stream. Sufficient gravel 122 is introduced so that it extends about 20 to 60 feet above the top perforation in the casing 110.

Referring to FIG. 10, after the gravel 122 has been forced into the producing zone 112, a slotted screen 123 may be placed inside the casing 110 having a plurality of slots 124. The screen 123 aids in mechanically supporting the particulate material 122 and holding the particulate pack in place. Thus, the sand consolidation method of the present invention is fail-safe, in that a failure of the consolidation adhesive agent 121 to penetrate the unconsolidated sand does not produce points of failure. For example, in the plugged perforations 114 and 117, the particulate material 122 mechanically supports the debris in the plugged perforations such that it is unlikely that the debris will even be loosened during production. Even if loosened, it will compact at the inner face with the gravel 122 and plug the particulate material 122 in an area around that perforation without interfering with other perforations. Likewise, at a weakly consolidated perforation such as perforation 118, the mechanical support of the particulate pack will prevent failure due to the weak consolidation. Even if loose sand from the producing zone 112 does come into contact with the particulate material 122 the sand will plug that perforation without interfering with other perforations. Furthermore, according to the present invention, the sand consolidated by the sand consolidation adhesive agent 121 need not have nearly the strength necessary for sand control as when the adhesive agent 121 is used alone without the particulate pack since the consolidated sand is supported mechanically during production of the fluids in the producing zone 112 by the particulate material 122 and the screen 123. The limited productivity of gravel pack systems is eliminated by the use of coarse particulate matter, preferably gravel, for the particulate pack. The large size gravel also permits clean up of fines, mud particles and plugging material which would otherwise plug a gravel pack system. The limited productivity caused by a normal gravel pack being plugged with fine formation sand is eliminated by consolidating the formation sand out beyond the particulate pack interval with the sand consolidation adhesive agent 121. Furthermore, the sand consolidation method of the present invention leaves no opportunity for resin coated sand to accumulate inside the well bore, either during treatment or during the waiting time for the resin to set and consolidate the sand, thus eliminating any necessity for a difficult or expensive clean up job, or the potential complete loss of the well due to plugging of the well bore with undrillable material.

As shown in FIG. 11, it is preferred that the particulate material 122 or gravel be forced into the producing zone 12 under high pressures equivalent to 0.6 psi per foot of depth, or higher. The forcing of the particulate material 122 or gravel at high pressures produces a high permeability finger 125 extending out into the producing zone 112 and which may extend past the sand consolidation adhesive agent 121 in certain instances. The high permeability finger 125, if it so extends beyond the adhesive agent 121 will tend to plug with loose unconsolidated sand 126 at the outer tip while still maintaining the high permeability within the finger 125 adjacent to the consolidated sand.

While the present invention has been illustrated in a cased well, which has been described as duly perforated and consolidated in a continuous operation, the present invention is not so limited in that the injection of the particulate material may be carried out in a well which has been previously consolidated with a sand consolidation adhesive agent such as a thermoplastic resin and in which the sand consolidation adhesive agent has already hardened. Furthermore, the well treated according to the present invention may have already been on production and the injection of the sand consolidation adhesive agent and particulate material or the injection of the particulate material to an already consolidated formation may be done as a workover operation. Still further, the injection of the particulate material into a producing zone which has already had a sand consolidation adhesive agent injected thereinto may be into a producing zone which is below the casing.

Furthermore, rather than a simple cased well having only a single production zone, the present invention may be carried out in a multiple completion well, as illustrated in FIG. 12, having a casing 140 extending to producing zones 141 and 142. String 143 is in communication with the producing zone 142 whereas the string 144 is in communication with the producing zone 141. Suitable packers 145 and 146 separate the specific producing zone 141 wherein the sand consolidation method of the present invention may be carried out. After injection of the sand consolidation adhesive agent and the forcing of the particulate material into the producing zone 141, a screen 147 may be placed in the string 144 above the particulate material rather than being set in the particulate material or gravel within the casing 140. While the screen 147 is shown in the string 144 to illustrate another placement of the screen, it may be preferred to have a concentric screen (as illustrated in FIG. 10) extending down from the producing string 144 in a multiple completion well. In some instances a concentric screen and a screen in the producing string may be used in the particulate pack. Since a large size particulate material, such as three or four mesh gravel, may be used in the process of the present invention, productivity is reduced very little as a result of the gravel being packed between the casing wall and the screen, whether the screen is in the particulate pack or in the producing string.

The preferred embodiments having been described, it is to be understood that the present invention is not limited by the manner in which the sand consolidation adhesive agent is injected into the producing formation or to any specific procedure which may be used in injecting the adhesive agent into the formation. Therefore, the adhesive agent may be injected into the producing formation in the manner used in a resin-sand pack consolidation process wherein a particulate material is coated with the adhesive agent. Still further, the present invention may be carried out in a well wherein the steps of the present invention are preceded by the injection of acid, surfactant, a mutual solvent, a fracture treatment, or any combination of these. Furthermore, the present invention may be used to repair ruptured or damaged casing where the damage exists within the producing zone.

Claims

The nature and object of the present invention having been completely described and illustrated, and the best mode thereof contemplated set forth, what I wish to claim as new and useful, and secure by Letters Patent is:

1. A method for controlling the flow of sand into a well which comprises:

injecting into a producing zone a sand consolidation adhesive agent which will cause consolidation by the sand particles sticking one to another,

forcing a particulate material substantially free of sand consolidation adhesive agent into said producing zone after said sand consolidation adhesive agent, and

producing through said consolidated sand and particulate material.

2. A method according to claim 1 wherein said sand consolidation adhesive agent is injected in two sequential steps.

3. A method according to claim 2 wherein one component of said sand consolidation adhesive agent is injected in one step and a setting agent component is injected thereafter.

4. A method according to claim 3 wherein said particulate material is introduced into said producing zone with said setting agent component.

5. A method according to claim 2 wherein said sand consolidation adhesive agent is injected in one step and an after-flush stream is injected thereafter.

6. A method according to claim 5 wherein said particulate material is introduced into said producing zone in said after-flush stream.

7. A method according to claim 1 wherein said particulate material is forced into said producing zone at pressures equivalent to at least 0.6 psi per foot of depth.

8. A method according to claim 1 wherein a screen is placed in communication with a producing string after forcing said particulate material into said producing zone and before commencing producing.

9. A method according to claim 8 wherein said screen is within a casing and said particulate material surrounds said screen and extends into said producing zone.

10. A method according to claim 9 wherein said particulate material is gravel.

11. A method according to claim 1 wherein said particulate material is gravel.

12. A method according to claim 11 wherein said gravel is of substantially uniform size ranging from about 3 to 12 mesh.

13. In a method for controlling the flow of sand into a well wherein a sand consolidation adhesive agent has been introduced into a producing zone to consolidate the sand, the improvement which comprises:

forcing a particulate material substantially free of sand consolidation adhesive agent into said producing zone after said sand consolidation adhesive agent, and

maintaining said particulate material therein while producing through said consolidated sand and particulate material.

14. In a method according to claim 13 wherein said particulate material is forced into said producing zone at pressures equivalent to at least 0.6 psi per foot of depth.

15. In a method according to claim 13 wherein said particulate material is maintained in said producing zone by a screen.

16. In a method according to claim 15 wherein said screen is concentric with said well.

17. In a method according to claim 15 wherein said screen is above said particulate material and in communication with the producing string.

18. A method according to claim 15 wherein said screen is within a casing and said particulate material surrounds said screen and extends into said producing zone.

19. A method according to claim 18 wherein said particulate material is gravel.

20. A method according to claim 15 wherein said screen is within one of a multiple of producing strings and said particulate material contacts said screen and extends into said producing zone.

21. A method according to claim 20 wherein said particulate material is gravel.

22. In a method according to claim 13 wherein said sand consolidation adhesive agent is a thermosetting resin.

23. In a method according to claim 22 wherein said particulate material is gravel and is forced into said producing zone before said thermosetting resin has hardened whereby said particulate material provides a mechanical support while said thermosetting resin hardens.