DK2823140T3 - Method of zone isolation in an underground well - Google Patents

Description

DESCRIPTION

[0001] The invention relates to a method for zone isolation in a subterranean producing well. More specifically, the invention relates to a method in which a balanced plug is established over a longitudinal section and in the entire cross section of the well to prevent undesired production from a reservoir.

[0002] Isolation between zones in different production intervals is essential to be able to control and optimize the production from a subterranean well, such as a petroleum well or a geothermal well. As a reservoir is being emptied and/or existing barriers for isolation between different zones are becoming weaker, the fluid flows within the reservoir may change so that the production decreases or, at worst, comes to a halt. For example, when a production interval is emptied of oil, the interface between water and oil may gradually be draw upwards and enter the producing zone, so-called coning, so that a flow of water completely or partially replaces the flow of hydrocarbons into the production string of the well. Gas coning may also occur. Barriers intended to prevent undesired fluid flows between different zones of a reservoir are subjected to great strains, in the form of powerful pressures and temperature differences among other things, hence intense tension and stress forces. It is known that this may result in damage to a cement barrier so that the integrity of the barrier is ruined. This may result in undesired fluid production behind casing and casing liners, among other things, and could further reduce or, at worst, make further production from the well impossible.

[0003] The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art, or at least to provide a useful alternative to the prior art.

[0004] The object is achieved through features specified in the description below and in the claims that follow.

[0005] A method for zone isolation in a subterranean producing well is disclosed, the method preventing fluid flow between a formation zone, from which undesired fluids are entering and flowing in the well, and a production zone located at a distance from said formation zone, the well being provided with a pipe body, at least in a portion of the well, the method including the following steps: (A) providing a plug over a longitudinal section of the well located between said formation zone and said production zone, the plug covering substantially the entire cross section of the well at least in a portion of the longitudinal section, so that the plug fills the inside of the pipe body and an annulus between the outside of the pipe body and a surrounding well body, wherein step (A) also includes the following sub-steps: (A1) lowering a perforation tool into the pipe body to the longitudinal section where the plug is to be set; (A2) forming perforations in the pipe body along the longitudinal section by means of the perforation tool; (A3) by means of a washing tool which is attached to a string allowing through-flow and which is lowered to the longitudinal section, pumping a washing fluid down the string and out into the pipe body via the washing tool; (A4) by means of a directional-control means connected to the washing tool, directing the washing fluid into the annulus between the outside of the pipe body and the surrounding well body; and (A5) pumping a fluidized plugging material down the string and out into the pipe body, and thereby also into the annulus via the perforations in the pipe body.

[0006] The pipe body may be, for example, a casing or a casing liner of types known per se and the pipe body may be part of a longer pipe string.

[0007] The surrounding well body may be another pipe body, or it may be the formation itself.

[0008] It is also known that a well plug may be established by means of a method and devices as proposed in Norwegian patent application 20111641 entitled "Method for combined cleaning and plugging in a well, washing tool for directional washing in a well, and use of the washing tool", and by means of Norwegian patent application 20120099 entitled "Apparatus and method for positioning of a fluidized plugging material in an oil well or gas well", both filed in the name of the present applicant.

[0009] Further details about the sub-steps A1-A5 and also about said washing tool can be found in the above-mentioned Norwegian patent application 20111641. This application, however, does not disclose plugging in conjunction with zone isolation in a producing well, which is the concern of the present method.

[0010] Norwegian patent application 20111641 is also disclosed as international publication WO 2012/096580 A1. The method and washing tool disclosed in these publications were also disclosed to some extent in a presentation held by Arne G. Larsen in a "P&A Forum Workshop" at Sola, Norway on 9th June 2011. This presentation was titled "HydraWash™ - a new approach to get cement behind casing without milling". This new approach is also referred to as the HydraWash system in the industry.

[0011] The noted method and washing tool were also disclosed to some extent in a presentation held at the "SPE Arctic and Extreme Environments Conference & Exhibition" in Moscow, Russia on 18th October 2011. The presentation was also prepared as SPE paper 148640 titled "Novel Approach to More Effective Plug and Abandonment Cementing Techniques". This novel approach is referred to as the Perforate, Wash and Cement (PWC) system in SPE 148640, but also in the industry.

[0012] Further, the perforation tool may be a perforation gun of a type known perse.

[0013] This may be appropriate in order to ensure good circulation of a plugging material from the inside of the pipe body out into the annulus on the outside of the pipe body. The perforation may be carried out in an undamaged/un-perforated portion of the pipe body or in an already perforated portion of the pipe body if the number, distribution and design of the perforations are not sufficient to ensure good circulation for subsequent washing and plugging. A preferred distribution of the perforations in the pipe body may be in the order of 40 perforations per meter (12 perforations per foot) in a 135/45 degrees' phase within said longitudinal section.

[0014] In one embodiment, the method includes providing one or more new perforations in a portion of the pipe body located outside the longitudinal section in which the plug has been set, thereby allowing production from said production zone. This may be necessary if, for example, existing production perforations have been blocked or closed off from the rest of the well in connection with the zone isolation. For example, the longitudinal section may be located opposite said formation zone, from which undesired fluids are entering and flowing in the well.

[0015] In one variant of the preceding embodiment, said production zone is located below said formation zone, from which undesired fluids are entering and flowing in the well, wherein the method, after step (A), includes a step of: (B) drilling out a central, through-going portion of the plug, so that there is at least a cross-sectional section of the plug left on the outside of the pipe body; and • providing said one or more new perforations in a portion of the pipe body located below the longitudinal section, thereby allowing production from the lower production zone whilst preventing flow of undesired fluids in said annulus outside the pipe body.

In another embodiment of the method, and before step (A) thereof, said production zone is producing into the well via perforations in the pipe body; • wherein said formation zone, from which undesired fluids are entering and flowing in the well, is located below said production zone; • wherein said undesired fluids are flowing from the lower formation zone onto the upper production zone via said annulus of the well; and • wherein the method, in step (A), includes providing the plug between said lower formation zone and said upper production zone, thereby isolating the annulus and the flow of undesired fluids therein.

[0016] In the latter embodiment of the method, the plug remains set in the entire cross section of the well. This may be advantageous in, for example, a case in which a barrier element set earlier has lost its integrity and there is undesired fluid production behind a casing or a casing liner, and from a part of the formation below. Thus, a plug covering the entire cross section could isolate the formation, from which the undesired fluid production is coming, from the rest of the well.

[0017] Further, the method is suitable for use in a situation wherein said subterranean well is a petroleum well; • wherein said production zone produces hydrocarbon fluids; and • wherein said undesired fluids are water.

[0018] Yet further, a displacement member may be used in the method to further displace and distribute the fluidized plugging material in the pipe body and further into the annulus. Thus, it may be an advantage if a displacement member in the form of a pressure apparatus, as described in Norwegian patent application 20120099 mentioned above, is used to further displace and distribute the fluidized plugging material in the casing and further out into the annulus.

[0019] In one embodiment of the method, the steps of perforation (A2) and washing (A3, A4) may be carried out in separate trips down into the well.

[0020] In another embodiment of the method, the steps of perforation (A2) and washing (A3, A4) may be carried out in one and the same trip down into the well. A combined perforation and washing apparatus is described in Norwegian patent application 20111641 mentioned above. The perforation tool and the washing tool may be releasable in combination or individually from the string.

[0021] In one embodiment, the method may further include leaving the perforation tool in the well. This may be practical to save operation time if the perforation tool can be "hidden" in the well and/or if the perforation tool is a drillable one.

[0022] As an alternative or addition, the method may further include leaving the washing tool in the well. This may be advantageous in order to save operation time and/or to use the washing tool as a base for the plug that is to be established. It may be advantageous if the washing tool is a drillable one.

[0023] Further, the fluidized plugging material may include cement slurry for the formation of a cement plug. As an alternative or addition, the fluidized plugging material may include unconsolidated mass for the formation of an unconsolidated-mass plug.

[0024] In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings, in which:

Figures 1-8 show, in side views, simplified schematic sections of a well in different stages in accordance with a first embodiment of the method of the present invention; and Figures 9-10 show, in side views, simplified schematic sections of a well in different stages in accordance with a second embodiment of the method of the present invention.

[0025] In what follows, the reference numeral 1 indicates a subterranean well as used in the method of the present invention. The well 1 has been drawn in a schematic and greatly simplified manner, and well elements not being central to the invention may have been left out of the drawings. Well fluids and cement barriers already established and known to a person skilled in the art, are not shown in the figures. A casing 21 extends down into the well 1, forming a radial boundary between a well path 2 and a surrounding formation 7. A pipe body 211 in the form of a casing liner is hung from the lower portion of the casing 21, extending down into a producing part of the well 1. The casing liner 211 is formed with perforations 212, through which fluids may flow from the formation 7 into the well 1. A connection pipe 210 and the casing liner 211 together form a pipe string which extends throughout the length of the well 1. In the exemplary embodiment shown, the pipe string is formed with one and the same inner diameter. The purpose of the method of the present invention is to isolate formation zones, from which undesired fluids are entering the well 1, from the rest of the well 1, whether it be undesired fluid flow through producing perforations 212, as shown in the figures 1-8, or undesired fluid flow behind casing 21 or casing liners 211, as shown in the figures 9-10.

[0026] Figure 1 shows a producing well 1. An interface between water and oil has been drawn upwards and into the producing zone of the formation 7, so that an undesired flow of water, indicated by arrows in towards the perforations 212, has completely or partially replaced the flow of hydrocarbons into the well 1. To remove or at least reduce the undesired water flow into the well 1, there is a wish to isolate the zone, from which the undesired production is coming, from the rest of the well 1. The reference numeral 221 indicates a safety/production valve of a type known per se.

[0027] Figure 2 shows the well 1 after a perforation tool 33 has been lowered into the casing liner 211 and placed along a longitudinal section L1 opposite the perforations 212. The perforation tool 33 may be a perforation gun of a type known perse. The perforation tool 33 is used to form new perforations 213 in the casing liner 211, as shown in figure 3, the perforations of which are to be used in subsequent washing and plugging. In a case in which the existing perforations 212 satisfy the requirements for design, position and density, as required in the subsequent washing and plugging operations as described above, it will not be necessary to form new perforations 213. Figure 3 shows the well 1 after the string 3 with the perforation tool 33 has been pulled out and new perforations 213 have been formed in the casing liner 211.

[0028] A combined washing and plugging tool 35 is then lowered into the well 1 within the casing liner 211, as shown in figure 4. Perforation and cleaning and plugging may be carried out in the same trip or in separate trips down the well 1. A washing fluid (not shown) is carried through the string 3, into the casing liner 211 and further out into an annulus 5 via the perforations 213. It may be an advantage if the washing fluid is directed substantially radially into the annulus 5 by means of a directional-control means 351, as described in the Norwegian patent application 20111641. A washing fluid at great velocity may remove various particles, deposits and remains from earlier downhole operations, so that a fluidized plugging material, which is subsequently to be carried into the annulus 5, may flow freely and be adhered in a better way. Then the fluidized plugging material is pumped through the string 3 and out into the casing liner 211, and thereby also into the annulus 5 via the perforations 213 in the casing liner 211, so that a plug 25 is formed over the longitudinal section L1, as shown in figure 5. At least in a portion within the longitudinal section L1, the plug 25 of cured plugging material extends over the entire cross section T1 of the well 1. It may be an advantage if an apparatus, as described in Norwegian patent application 20120099, is used in order to further displace and distribute the fluidized plugging material in the casing liner 211 and out into the annulus 5. The latter apparatus is not shown in the figures connected to the present document.

[0029] Figure 6 shows the well 1 after a central through-going portion of the plug 25 has been drilled away by means of a drilling tool 31. A cross-sectional section T3 of the plug 25 outside the casing liner 211 is left inside the longitudinal section L1. The remaining cross-sectional section T3 of the plug 25 outside the casing liner 211 forms a barrier 51 in the annulus 5 between the casing liner 211 and the formation 7, thereby isolating the well 1 from the reservoir zone from which the undesired water production was coming.

[0030] Figure 7 shows the well 1 after it has been fully isolated for the above-mentioned purposes, whereas figure 8 shows the well 1 after new perforations 214 have been formed in the casing liner 211 at a distance from the longitudinal section L1, so that there may be production from another zone without undesired water drive. The distance between the longitudinal section L1 and the new perforations 214 may be very large, maybe in the order of kilometres.

[0031] Figure 9 shows a well 1 in which an undesired water flow, indicated by arrows, is coming from a formation zone below the production zone and is flowing in behind the casing liner 211, i.e. undesired water is flowing in the annulus 5. This may quite possibly be a result of an earlier poor and/or difficult cementation job. There is therefore a need for new zone isolation. A plug is set in the entire cross section of the well, as shown in figure 10, and in a portion below perforations 212 already producing, by means of steps indicated in the figures 2- 5. The plug 25 isolates the well 1 from the zone from which the undesired water production was coming, and the production may be resumed via the perforations 212 existing already.

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description • NQ2Q120099 Γ00081 [00181 [00281 • VVO2012096580A1 |Q0101

Non-patent literature cited in the description . ARNE G. LARSENP&A Forum Workshop, 2011, Γ0010Ί • SPE Arctic and Extreme Environments Conference & Exhibition, 2011, [00111

Claims (13)

1. Fremgangsmåde til zoneisolation i en underjordisk produktionsbrønd (1), fremgangsmåden forhindrer fluidstrømning mellem en dannelseszone, hvorfra uønskede fluider kommer ind i og strømmer i brønden (1), og en produktionszone, der er placeret i afstand fra nævnte dannelseszone, brønden (1) er forsynet med et rørelement (211), i det mindste i en del af brønden (1), hvilken fremgangsmåde inkluderer de følgende trin: (A) tilvejebringe en prop (25) over en langsgående sektion (LI) af brønden (1) placeret mellem nævnte dannelseszone og nævnte produktionszone, proppen (25) dækker i det væsentlige hele brøndens (1) tværsnit (TI) i det mindste i en del af den langsgående sektion (LI) , således at proppen (25) fylder indersiden af rørelementet (211) og et ringvolumen (5) mellem rørelementets (211) yderside og et omgivende brøndelement (7), hvori trin (A) også inkluderer følgende undertrin: (Al) sænke et perforeringsværktøj (33) ned i rørelementet (211) ned til den langsgående sektion (LI), hvor proppen (25) skal sættes; (A2) danne perforeringer (213) i rørelementet (211) langs den langsgående sektion (LI) ved hjælp af perforeringsværktøjet (33); (A3) ved hjælp af et vaskeværktøj (35), som er fastgjort til en streng (3), der tillader gennemstrømning, og som er nedsænket til den langsgående sektion (LI), pumpe et vaskefluid ned gennem strengen (3) og ud i rørelementet (211) via vaskeværktøjet (35); (A4) ved hjælp af et retningskontrolmiddel, der er forbundet med vaskeværktøjet (35), lede vaskefluidet ind i ringvolumenet (5) mellem rørelementets (211) yderside og det omgivende brøndelement (7); og (A5) pumpe et fluidiseret tilpropningsmateriale ned gennem strengen (3) og ud i rørelementet (211) og derved også ind i ringvolumenet (5) via perforeringerne (213) i rørelementet (211).A method for zone isolation in an underground production well (1), the method prevents fluid flow between a formation zone from which undesirable fluids enter and flow into the well (1) and a production zone spaced from said formation zone, the well (1). ) is provided with a pipe element (211), at least in a portion of the well (1), which method comprises the following steps: (A) providing a plug (25) over a longitudinal section (LI) of the well (1) located between said formation zone and said production zone, the stopper (25) covers substantially all of the cross-section (T1) of the well (1) at least in a portion of the longitudinal section (LI) so that the stopper (25) fills the inside of the tubular member ( 211) and a ring volume (5) between the outside of the tube member (211) and a surrounding well member (7), wherein step (A) also includes the following sub-steps: (A1) lowering a perforating tool (33) down the tube member (211) down to the longitudinal section (LI) where the plug (25) is to be inserted; (A2) forming perforations (213) in the tube member (211) along the longitudinal section (L1) by the perforating tool (33); (A3) by means of a washing tool (35) attached to a flow (3) allowing flow and submerged to the longitudinal section (LI), pumps a washing fluid down the string (3) and into the pipe element (211) via the washing tool (35); (A4), by means of a directional control means connected to the washing tool (35), guides the washing fluid into the annulus (5) between the outside of the pipe element (211) and the surrounding well element (7); and (A5) pumping a fluidized plug material down through the string (3) and out into the tube member (211) and thereby also into the ring volume (5) via the perforations (213) in the tube member (211). 2. Fremgangsmåde ifølge krav 1, hvori fremgangsmåden inkluderer, at der i en del af rørelementet (211) tilvejebringes en eller flere nye perforeringer (214), som er placeret uden for den langsgående sektion (LI), hvori proppen (25) er blevet sat, hvorved der tillades produktion fra nævnte produktionszone.The method of claim 1, wherein the method includes providing in one part of the tube member (211) one or more new perforations (214) located outside the longitudinal section (LI) wherein the plug (25) has been set, thereby allowing production from said production zone. 3. Fremgangsmåde ifølge krav 2, hvori den langsgående sektion (LI) er placeret modsat nævnte dannelseszone, hvorfra uønskede fluider kommer ind i og strømmer i brønden (1).The method of claim 2, wherein the longitudinal section (LI) is located opposite said formation zone from which unwanted fluids enter and flow into the well (1). 4. Fremgangsmåde ifølge krav 2 eller 3, hvori nævnte produktionszone er placeret under nævnte dannelseszone, hvorfra uønskede fluider kommer ind i og strømmer i brønden (1) , og hvor fremgangsmåden efter trin (A) inkluderer et trin (B) hvor en central gennemgående del af proppen (25) udbores, således at der i det mindste er et tværsnitsafsnit (T3) af proppen (25) tilbage på rørelementets (211) yderside; og tilvejebringe nævnte en eller flere nye perforeringer (214) i en del af rørelementet (211), som er placeret under den langsgående sektion (LI), for derved at tillade produktion fra den nedre produktionszone, medens strømning af uønskede fluider i ringvolumenet (5) uden for rørelementet (211) forhindres.The method of claim 2 or 3, wherein said production zone is located below said formation zone from which undesirable fluids enter and flow into the well (1), and the method of step (A) includes a step (B) wherein a central passageway portion of the plug (25) is drilled so that there is at least one cross-sectional portion (T3) of the plug (25) remaining on the outside of the tube member (211); and providing said one or more new perforations (214) in a portion of the tube member (211) located below the longitudinal section (LI), thereby allowing production from the lower production zone while flowing unwanted fluids into the ring volume (5). ) outside the pipe element (211) is prevented. 5. Fremgangsmåde ifølge krav 1, hvori nævnte produktionszone, før fremgangsmådens trin (A) , producerer i brønden (1) via perforeringer (212) i rørelementet (211). hvori nævnte dannelseszone, hvorfra uønskede fluider kommer ind i og strømmer i brønden (1), er placeret under produktionszonen; hvori nævnte uønskede fluider strømmer fra den nedre dannelseszone til den øvre produktionszone via brøndens (1) nævnte ringvolumen (5); og hvor fremgangsmåden i trin (A) inkluderer, at proppen (25) tilvejebringes mellem nævnte nedre dannelseszone og nævnte øvre produktionszone, for derved at isolere ringvolumenet (5) og strømmen af uønskede fluider deri.The method of claim 1, wherein said production zone, prior to step (A) of the method, produces in the well (1) via perforations (212) in the tube member (211). wherein said formation zone from which undesirable fluids enter and flow into the well (1) is located below the production zone; wherein said unwanted fluids flow from the lower formation zone to the upper production zone via the annular volume (5) of the well (1); and wherein the method of step (A) includes providing the plug (25) between said lower formation zone and said upper production zone, thereby isolating the ring volume (5) and the flow of unwanted fluids therein. 6. Fremgangsmåde ifølge et hvilket som helst af kravene 1-5, hvori nævnte underjordiske brønd er en oliebrønd; hvori nævnte produktionszone producerer carbonhydridfluider; og hvori nævnte uønskede fluider er vand.The method of any one of claims 1-5, wherein said underground well is an oil well; wherein said production zone produces hydrocarbon fluids; and wherein said unwanted fluids are water. 7. Fremgangsmåde ifølge et hvilket som helst af kravene 1-6, hvori et forskydningselement anvendes til yderligere at forskyde og fordele det fluidiserede tilpropningsmateriale i rørelementet (211) og videre ud i ringvolumenet (5).A method according to any one of claims 1-6, wherein a shear element is used to further displace and distribute the fluidized plug material in the tube element (211) and further out in the annulus volume (5). 8. Fremgangsmåde ifølge et hvilket som helst af kravene 1-7, hvori perforerings- (A2) og vasketrinnene (A3, A4) udføres i separate ture ned i brønden (1).A method according to any of claims 1-7, wherein the perforation (A2) and the washing steps (A3, A4) are carried out in separate trips down the well (1). 9. Fremgangsmåde ifølge et hvilket som helst af kravene 1-7, hvori perforerings- (A2) og vasketrinnene (A3, A4) udføres i én og samme tur ned i brønden (1).A method according to any one of claims 1-7, wherein the perforation (A2) and the washing steps (A3, A4) are carried out in the same well down the well (1). 10. Fremgangsmåde ifølge et hvilket som helst af kravene 1-9, hvori fremgangsmåden endvidere inkluderer, at perforeringsværktøjet (33) efterlades i brønden (1).The method of any one of claims 1-9, wherein the method further includes leaving the perforation tool (33) in the well (1). 11. Fremgangsmåde ifølge et hvilket som helst af kravene 1-10, hvor fremgangsmåden endvidere inkluderer, at vaskeværktøjet (35) efterlades i brønden (1).A method according to any one of claims 1-10, wherein the method further includes leaving the washing tool (35) in the well (1). 12. Fremgangsmåde ifølge et hvilket som helst af kravene 1-11, hvori det fluidiserede tilpropningsmateriale inkluderer cementopslæmning til dannelse af en cementprop (25).A method according to any one of claims 1-11, wherein the fluidized plug material includes cement slurry to form a cement plug (25). 13. Fremgangsmåde ifølge et hvilket som helst af kravene 1-12, hvori det fluidiserede tilpropningsmateriale inkluderer en ukonsolideret masse til dannelsen af en prop (25) af en ukonsolideret masseA method according to any one of claims 1-12, wherein the fluidized plug material includes an unconsolidated mass for forming a plug (25) of an unconsolidated mass