EP2823140B1

EP2823140B1 - Method for zone isolation in a subterranean well

Info

Publication number: EP2823140B1
Application number: EP13757768.0A
Authority: EP
Inventors: Arne Gunnar Larsen; Patrick ANDERSEN; Roy Inge JENSEN; Arnt Olav DAHL; Morten Myhre
Original assignee: Hydra Systems AS
Current assignee: Hydra Systems AS
Priority date: 2012-03-09
Filing date: 2013-03-06
Publication date: 2017-11-15
Anticipated expiration: 2033-03-06
Also published as: AU2013228114A1; DK2823140T3; AU2013228114B2; EP2823140A1; NO336527B1; CA2897621A1; NO20120275A1; EP2823140A4; CA2897621C; WO2013133720A1; US20150027705A1

Description

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

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.
The surrounding well body may be another pipe body, or it may be the formation itself.
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.
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.
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.
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.
Further, the perforation tool may be a perforation gun of a type known per se.
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.
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.
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.

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.
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.

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.
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.
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.
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.
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.
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.
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.

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.
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.
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 per se. 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.
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.
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.
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.
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.

Claims

A method for zone isolation in a subterranean producing well (1), the method preventing fluid flow between a formation zone, from which undesired fluids are entering and flowing in the well (1), and a production zone located at a distance from said formation zone, the well (1) being provided with a pipe body (211), at least in a portion of the well (1), the method including the following steps:
(A) providing a plug (25) over a longitudinal section (L1) of the well (1) located between said formation zone and said production zone, the plug (25) covering substantially the entire cross section (T1) of the well (1) at least in a portion of the longitudinal section (L1), so that the plug (1) fills the inside of the pipe body (211) and an annulus (5) between the outside of the pipe body (211) and a surrounding well body (7), wherein step (A) also includes the following sub-steps:
(A1) lowering a perforation tool (33) into the pipe body (211) to the longitudinal section (L1) where the plug (25) is to be set;

(A2) forming perforations (213) in the pipe body (211) along the longitudinal section (L1) by means of the perforation tool (33);

(A3) by means of a washing tool (35) which is attached to a string (3) allowing through-flow and which is lowered to the longitudinal section (L1),

pumping a washing fluid down the string (3) and out into the pipe body (211) via the washing tool (35);

(A4) by means of a directional-control means connected to the washing tool (35), directing the washing fluid into the annulus (5) between the outside of the pipe body (211) and the surrounding well body (7); and

(A5) pumping a fluidized plugging material down the string (3) and out into the pipe body (211), and thereby also into the annulus (5) via the perforations (213) in the pipe body (211).
The method in accordance with claim 1, wherein the method includes providing one or more new perforations (214) in a portion of the pipe body (211) located outside the longitudinal section (L1) in which the plug (25) has been set, thereby allowing production from said production zone.
The method in accordance with claim 2, wherein the longitudinal section (L1) is located opposite said formation zone, from which undesired fluids are entering and flowing in the well (1).
The method in accordance with claim 2 or 3, wherein said production zone is located below said formation zone, from which undesired fluids are entering and flowing in the well (1), and wherein the method, after step (A), includes a step of:
(B) drilling out a central, through-going portion of the plug (25), so that there is at least a cross-sectional section (T3) of the plug (25) left on the outside of the pipe body (211); and
- providing said one or more new perforations (214) in a portion of the pipe body (211) located below the longitudinal section (L1), thereby allowing production from the lower production zone whilst preventing flow of undesired fluids in said annulus (5) outside the pipe body (211).
The method in accordance with claim 1, wherein before step (A) of the method, said production zone is producing into the well (1) via perforations (212) in the pipe body (211);
- wherein said formation zone, from which undesired fluids are entering and flowing in the well (1), 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 (5) of the well (1); and

- wherein the method, in step (A), includes providing the plug (25) between said lower formation zone and said upper production zone, thereby isolating the annulus (5) and the flow of undesired fluids therein.
The method in accordance with any one of claims 1-5, wherein said subterranean well is a petroleum well;
- wherein said production zone produces hydrocarbon fluids; and

- wherein said undesired fluids are water.
The method in accordance with any one of claims 1-6, wherein a displacement member is used to further displace and distribute the fluidized plugging material in the pipe body (211) and further out into the annulus (5).
The method in accordance with any one of claims 1-7, wherein the steps of perforation (A2) and washing (A3, A4) are performed in separate trips down into the well (1).
The method in accordance with any one of claims 1-7, wherein the steps of perforation (A2) and washing (A3, A4) are performed in one and the same trip down into the well (1).
The method in accordance with any one of claims 1-9, wherein the method further includes leaving the perforation tool (33) in the well (1).
The method in accordance with any one of claims 1-10, wherein the method further includes leaving the washing tool (35) in the well (1).
The method in accordance with any one of claims 1-11, wherein the fluidized plugging material includes cement slurry for the formation of a cement plug (25).
The method in accordance with any one of claims 1-12, wherein the fluidized plugging material includes unconsolidated mass for the formation of an unconsolidated-mass plug (25).