Abstract:
A method of curing an inflatable packing is provided that includes providing a packer assembly having an inflatable packer around a mandrel; a polyamide bandage around the inflatable packer; and a sealing layer around both the polyamide bandage and the inflatable packer to from an airtight seal about the inflatable packer, wherein the method further includes curing the assembled packer assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present document is a continuation-in-part of prior co-pending U.S. patent application Ser. No. 12/134,562, filed on Jun. 6, 2008; which in turn is entitled to the benefit of, and claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/075,391, filed on Jun. 25, 2008, the entire disclosures of each of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a process for curing an inflatable packer in a pressurized air autoclave. 
       BACKGROUND 
       [0003]    A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a conveyance and expanded against the surrounding wellbore wall to isolate a region of the wellbore. Often, two or more packers can be used to isolate one or more regions in a variety of well related applications, including production applications, service applications and testing applications. 
         [0004]    In some applications, packers are used to isolate regions for collection of formation fluids. For example, a straddle packer can be used to isolate a specific region of the wellbore to allow collection of fluids. A straddle packer uses a dual packer configuration in which fluids are collected between two separate packers. The dual packer configuration, however, is susceptible to mechanical stresses which limit the expansion ratio and the drawdown pressure differential that can be employed. 
         [0005]    An addition problem with inflatable packers in general, is that they are typically cured in an air autoclave. Prior to curing, a polyamide bandage is typically wrapped around the inflatable packer at a given tension, to apply a pressure on the outside diameter of the inflatable packer. This polyamide bandage is then removed after curing. This process has several weaknesses. For example, the polyamide bandage doesn&#39;t seal the inflatable packer against exposure to air. As such, the rubber of the inflatable packer is exposed to high pressure air in the autoclave. This introduction of air into the rubber can significantly reduce the quality of the rubber due to oxidation. In addition, this air can migrate through the rubber, creating some high pressure bubbles. These bubbles can “explode” when the air pressure is released, greatly reducing the quality of the rubber. Also, the polyamide bandage itself is exposed to pressurized air in the autoclave, risking oxidation to the polyamide bandage and resulting property losses in the polyamide bandage. As such, a need for a new inflatable packer curing process exists. 
       SUMMARY OF THE INVENTION 
       [0006]    In one embodiment, the present invention provides a system and method for collecting formation fluids through a single packer having at least one window or drain located within the single packer. The single packer is designed with an outer layer that expands across an expansion zone to create a seal with a surrounding wellbore wall. The drain is located in the outer layer between its axial ends for collecting formation fluid. The collected fluid is routed from the drain to an axial end of the outer layer via a fluid flow passage. Additionally, mechanical fittings are mounted at the axial ends of the outer layer, and at least one of the mechanical fittings comprises one or more flow members coupled to the flow passage to direct the collected fluid from the packer. The one or more flow members are designed to move in a manner that freely allows radial expansion and contraction of the outer layer. 
         [0007]    In another embodiment, the present invention includes curing an inflatable packer in a manner that protects the inflatable packer from oxidation. For example, in one embodiment a sealing layer is disposed around a polyamide bandage, which in turn is disposed about an inflatable packer, such that during a curing process the sealing layer protects the polyamide bandage and the inflatable packer from oxidation. 
         [0008]    In yet another embodiment, a polyamide bandage having an anti-oxidation layer is disposed about an inflatable packer, such that during a curing process the polyamide bandage protects the inflatable packer from oxidation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
           [0010]      FIG. 1  is a schematic front elevation view of a well system having a single packer through which formation fluids can be collected, according to an embodiment of the present invention; 
           [0011]      FIG. 2  is an orthogonal view of one example of the single packer illustrated in  FIG. 1 , according to an embodiment of the present invention; 
           [0012]      FIG. 3  is an orthogonal view of one example of an outer layer that can be used with the single packer, according to an embodiment of the present invention; 
           [0013]      FIG. 4  is a view similar to that of  FIG. 3  but showing internal components of the outer layer, according to an embodiment of the present invention; 
           [0014]      FIG. 5  is an orthogonal view of one example of an inflatable bladder that can be used with the single packer, according to an embodiment of the present invention; 
           [0015]      FIG. 6  is a cross-sectional view of a portion of the inflatable bladder illustrated in  FIG. 5 , according to an embodiment of the present invention; 
           [0016]      FIG. 7  is an orthogonal view of one example of a mandrel that can be positioned within the inflatable bladder, according to an embodiment of the present invention; 
           [0017]      FIG. 8  is an orthogonal view of one example of the combined inflatable bladder and inner mandrel with the inflatable bladder in a contracted configuration, according to an embodiment of the present invention; 
           [0018]      FIG. 9  is a view similar to that of  FIG. 8  but showing the inflatable bladder in an inflated configuration, according to an embodiment of the present invention; 
           [0019]      FIG. 10  is an orthogonal view of one example of mechanical fittings that can be used with the single packer, according to an embodiment of the present invention; 
           [0020]      FIG. 11  is an exploded view of one example of the single packer illustrated in  FIG. 1 , according to an embodiment of the present invention; 
           [0021]      FIG. 12  is an orthogonal view of one example of the single packer with the outer layer shown as partially cut away, according to an embodiment of the present invention; 
           [0022]      FIG. 13  is a schematic cross-sectional view illustrating movable flow members of a mechanical fitting, according to an embodiment of the present invention; 
           [0023]      FIG. 14  is a front view of the single packer in a contracted configuration, according to an embodiment of the present invention; 
           [0024]      FIG. 15  is a cross-sectional view of the single packer of  FIG. 14  illustrating the flow members positioned in a radially inward configuration, according to an embodiment of the present invention; 
           [0025]      FIG. 16  is a front view of the single packer in an expanded configuration, according to an embodiment of the present invention; 
           [0026]      FIG. 17  is a cross-sectional view of the single packer of  FIG. 16  illustrating the flow members pivoted to a radially outward configuration, according to an embodiment of the present invention; 
           [0027]      FIG. 18  is a partially cut away view of the single packer illustrating possible flow patterns of the collected formation fluids, according to an embodiment of the present invention; and 
           [0028]      FIG. 19  illustrates the single packer deployed in a wellbore and expanded against the surrounding wellbore wall for the collection of formation fluids through a plurality of separate windows or drains, according to an embodiment of the present invention. 
           [0029]      FIG. 20  illustrates an assembly for protecting an inflatable packer against oxidation during a curing procedure, according to an embodiment of the present invention. 
           [0030]      FIG. 21  illustrates an assembly for protecting an inflatable packer against oxidation during a curing procedure, according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
         [0032]    The present invention generally relates in one embodiment to a system and method for collecting formation fluids through a window or drain in the middle of a single packer. The collected formation fluids are conveyed along an outer layer of the packer to a tool flow line and then directed to a desired collection location. Use of the single packer enables the use of larger expansion ratios and higher drawdown pressure differentials. Additionally, the single packer configuration reduces the stresses otherwise incurred by the packer tool mandrel due to the differential pressures. Because the packer uses a single expandable sealing element, the packer is better able to support the formation in a produced zone at which formation fluids are collected. This quality facilitates relatively large amplitude draw-downs even in weak, unconsolidated formations. 
         [0033]    The single packer expands across an expansion zone, and formation fluids can be collected from the middle of the expansion zone, i.e. between axial ends of the outer sealing layer. The formation fluid collected is directed along flow lines, e.g. along flow tubes, having sufficient inner diameter to allow operations in relatively heavy mud. Formation fluid can be collected through one or more windows/drains. For example, separate drains can be disposed along the length of the packer to establish collection intervals or zones that enable focused sampling at a plurality of collecting intervals, e.g. two or three collecting intervals. Separate flowlines can be connected to different drains to enable the collection of unique formation fluid samples. In other applications, normal sampling can be conducted by using a single drain placed between axial ends of the packer sealing element. 
         [0034]    Referring generally to  FIG. 1 , one embodiment of a well system  20  is illustrated as deployed in a wellbore  22 . The well system  20  comprises a conveyance  24  employed to deliver at least one packer  26  downhole. In many applications, packer  26  is used on a modular dynamics formation tester (MDT) tool deployed by conveyance  24  in the form of a wireline. However, conveyance  24  may have other forms, including tubing strings, for other applications. In the embodiment illustrated, packer  26  is a single packer configuration used to collect formation fluids from a surrounding formation  28 . The packer  26  is selectively expanded in a radially outward direction to seal across an expansion zone  30  with a surrounding wellbore wall  32 , such as a surrounding casing or open wellbore wall. When packer  26  is expanded to seal against wellbore wall  32 , formation fluids can be flowed into packer  26 , as indicated by arrows  34 . The formation fluids are then directed to a tool flow line, as represented by arrows  36 , and produced to a collection location, such as a location at a well site surface  38 . 
         [0035]    Referring generally to  FIG. 2 , one embodiment of single packer  26  is illustrated. In this embodiment, packer  26  comprises an outer layer  40  that is expandable in a wellbore to form a seal with surrounding wellbore wall  32  across expansion zone  30 . The packer  26  further comprises an inner, inflatable bladder  42  disposed within an interior of outer layer  40 . In one example, the inner bladder  42  is selectively expanded by fluid delivered via an inner mandrel  44 . Furthermore, packer  26  comprises a pair of mechanical fittings  46  that are mounted around inner mandrel  44  and engaged with axial ends  48  of outer layer  40 . 
         [0036]    With additional reference to  FIG. 3 , outer layer  40  may comprise one or more windows or drains  50  through which formation fluid is collected when outer layer  40  is expanded against surrounding wellbore wall  32 . Drains  50  may be embedded radially into a sealing element  52  of outer layer  40 . By way of example, sealing element  52  may be cylindrical and formed of an elastomeric material selected for hydrocarbon based applications, such as nitrile rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and fluorocarbon rubber (FKM). A plurality of tubular members or tubes  54  can be operatively coupled with drains  50  for directing the collected formation fluid in an axial direction to one or both of the mechanical fittings  46 . In one example, alternating tubes  54  are connected either to an individual central drain or to two drains located equidistant from an axial center region of the outer layer  40 , respectively. As further illustrated in  FIG. 4 , tubes  54  can be aligned generally parallel with a packer axis  56  that extends through the axial ends of outer layer  40 . In the example illustrated, the tubes  54  are at least partially embedded in the material of sealing element  52  and thus move radially outward and radially inward during expansion and contraction of outer layer  40 . 
         [0037]    Referring generally to  FIG. 5 , one embodiment of inflatable bladder  42  is illustrated. In this embodiment, inflatable bladder  42  comprises an inflatable membrane  58  held between membrane fittings  60  located at each of its axial ends. By way of example, each membrane fitting  60  may comprise a nipple region  62  and a skirt  64 . The membrane fittings  60  are used to connect the inflatable bladder  42  to inner mandrel  44 . In some applications, fittings  60  also can be used to securely retain a mechanical structure  66  of inflatable membrane  58 , as illustrated in  FIG. 6 . 
         [0038]    In  FIG. 6 , one embodiment of inflatable membrane  58  is illustrated as comprising an inner elastomeric, e.g. rubber, layer  68  surrounded by mechanical structure  66 . The mechanical structure  66  may comprise stiff, elongate support members  70  which may be in the form of metallic members, such as steel cables or metallic slats. An elastomeric, e.g. rubber, outer layer or cover  72  can be positioned around mechanical structure  66  to protect the mechanical structure from the well fluid and potential corrosion as well as from migration of sand or mud through the structure. Furthermore, the material of outer cover  72  can be selected to reduce friction between inflatable membrane  58  and the surrounding outer layer  40  during expansion. For example, outer cover  72  can be formed using a different compound relative to the compound used for outer layer  40 . Additionally, certain fillers can be added to the materials to minimize the friction coefficient. In one specific example, outer cover  72  can be formed from FKM filled with a nano polytetrafluoroethylene (PTFE), and outer layer  40  can be formed with HNBR. It should be noted, however, that some applications may require relatively low levels of pressure to expand outer layer  40  which allows the use of other materials and simpler construction, e.g. a folded bag construction, with respect to inflatable membrane  58 . 
         [0039]    Referring generally to  FIG. 7 , one example of inner mandrel  44  is illustrated. Inner mandrel  44  may be constructed in a variety of configurations useful for delivering fluid to expand inflatable membrane  58  via appropriate passages (not shown). As illustrated, inner mandrel  44  comprises one or more tubular sections  74  through which fluid may be pumped into inflatable bladder  42 . The tubular sections  74  are sized to fit securely within membrane fittings  60  of inflatable bladder  42 . By way of example, inner mandrel  44  may be part of an MDT tool connected to a wireline conveyance  24 . MDT tools typically comprise associated pumps, filters and electronics for conducting testing/sampling procedures. 
         [0040]    In  FIG. 8 , the inner mandrel  44  is illustrated as engaged within inflatable bladder  42 , while inflatable bladder  42  is in a contracted configuration prior to inflation. Fluid may be pumped down through inner mandrel  44  and displaced into an interior of inflatable membrane  58  through appropriate passages or openings. The continued supply of fluid under pressure fills the inflatable membrane  58  and causes it to expand radially, as illustrated in  FIG. 9 . 
         [0041]    Referring generally to  FIG. 10 , one embodiment of mechanical fittings  46  is illustrated. In this embodiment, each mechanical fitting  46  comprises a collector portion  76  having an inner sleeve  78  and an outer sleeve  80  that are sealed together. Each collector portion  76  can be ported as desired to deliver fluid collected from the surrounding formation to the established flow line  36  (see  FIG. 1 ). One or more movable members  82  are movably coupled to each collector portion  76 , and at least some of the movable members  82  are used to transfer collected fluid from tubes  54 , into the collector portion  76 , and into flow line  36 . By way of example, each movable member  82  may be pivotably coupled to its corresponding collector portion  76  for pivotable movement about an axis generally parallel with packer axis  56 . 
         [0042]    In the embodiment illustrated, a plurality of movable members  82  are pivotably mounted to each collector portion  76 . The movable members  82  may comprise one or more flow members  84  movably, e.g. pivotably, coupled to one or more of the collector portions  76 . Each flow member  84  is hollow and defines a flow path for conducting fluid from the tube  54  to which it is connected. The movable members  82  also may comprise one or more non-flow members  86  that also are coupled to corresponding tubes  54 . However, because members  86  do not allow flow, the fluid is forced through corresponding flow members  84  at the opposite mechanical fitting  46 . For the sake of example,  FIG. 10  illustrates four flow members  84  alternating with four non-flow members  86  at each mechanical fitting  46 . In this example, flow members  84  and non-flow members  86  are generally S-shaped and designed for pivotable connection with both the corresponding collector portion  76  and the corresponding tubes  54 . 
         [0043]    During assembly, inner mandrel  44  is inserted into inflatable bladder  42 , and one of the mechanical fittings  46  is slid over inner mandrel  44  against an axial end of the inflatable bladder  42 , as illustrated in  FIG. 11 . The outer layer  40  can then be slid over membrane  58  of inflatable bladder  42 , and the second mechanical fitting  46  is moved into engagement with the outer layer  40  so that outer layer  40  is trapped between the mechanical fittings  46 . Once properly aligned, the movable members  82  of each mechanical fitting  46  are coupled with corresponding tubes  54  of outer layer  40 , as illustrated in  FIG. 12 . It should be noted that  FIG. 12  does not illustrate sealing element  52  to better display the orientation of outer layer tubes  54  and the corresponding movable members  82 . 
         [0044]    As illustrated in  FIG. 13 , flow members  84  may be designed with a generally curvilinear shape oriented to curve around the axial ends of inflatable bladder  42 . Each flow member  84  has an attachment end  88 , with a flow passage  90 , designed for pivoting connection to a corresponding tube  54 . Each flow member  84  also curves through a predetermined rotational angle  92 , e.g. 102°, before being pivotably coupled to the collector portion  76  via a connection nipple  94  or other suitable, movable connection. The predetermined rotational angle  92  can vary and may be selected according to various factors, such as packer size and predetermined expansion ratio. The design and orientation of members  84  and  86  enable their radial movement, e.g. pivoting, during expansion of outer layer  40  without bending or otherwise stressing tubes  54 . 
         [0045]    Once the single packer  26  is assembled, it can be moved to a desired fluid collection region of wellbore  22  in a contracted configuration, as illustrated in  FIG. 14 . In this configuration, movable members  82  are pivoted to a contracted or radially inward position along the axial ends of inflatable bladder  42 , as illustrated in  FIG. 15 . At the desired location within wellbore  22 , expansion fluid is pumped down through inner mandrel  44  to inflate bladder  42  which, in turn, expands outer layer  40  in a radially outward direction throughout expansion zone  30 , as illustrated in  FIG. 16 . Expansion of outer layer  40  causes movable members  82  to pivot in a radially outward direction, as illustrated best in  FIG. 17 . It should be noted that the pivoting of movable members  82  also causes collector portions  76  to rotate about mandrel  44  a certain degree of rotation, as represented by arrow  96 . The movement of members  82  and collector portions  76  enables expansion of outer layer  40  without affecting the angular position of tubes  54  and without deforming or stressing the tubes  54 . 
         [0046]    One example of a fluid sampling technique can be described with reference to  FIG. 18 . In this example, individual drains  50  are disposed in a generally central zone or interval  98  and connected with corresponding individual tubes  54 . Formation fluid collected through the individual drains  50  in central interval  98  flows through the corresponding tubes  54 , into the corresponding flow members  84 , and through the collection portion  76 , as represented by arrows  100 . Alternating tubes  54  comprise pairs of drains  50  with each drain of the pair being located in an outlying zone or interval  102  or  104 . Interval  98  is positioned axially between intervals  102  and  104 . Formation fluid collected through the drains  50  in axially outlying intervals  102 ,  104  flows through the corresponding tubes  54 , into the corresponding flow members  84 , and through the collection portion  76  located at the opposite end of packer  26 , as represented by arrows  106 . 
         [0047]    Accordingly, formation fluid is collected through three different intervals. The fluid collected through the center interval  98  is routed in one direction through packer  26  to flow line  36 , and fluid collected through the outlying intervals  102 ,  104  is routed in another direction. It should be noted, however, that packer  26  can be designed with a greater number or lesser number of collection intervals, including single collection intervals, depending and the desired fluid sampling for a given while application. 
         [0048]    In  FIG. 19 , a three collection zone example of packer  26  is illustrated as expanded in wellbore  22 . The single packer  26  expands outer layer  40  and sealing element  52  against the surrounding wellbore wall  32  to form a seal across the entire expansion zone  30 . Formation fluid is collected through internal drains positioned to extend radially into outer layer  40 . The use of three intervals  98 ,  102  and  104  allows the axially outlying drains  50  to be used for protecting the drains  50  located in center interval  98  from contamination. 
         [0049]    During initial retrieval of fluid from formation  28 , contaminated fluid is sometimes absorbed through all of the drains  50 . As the sampling phase is continued, the contamination level of the sampled fluid decreases, particularly in the fluid flowing into the drains  50  of center interval  98 . Eventually, the drains  50  of center interval  98  absorb primarily clean fluid, while contaminated fluid is routed separately via axially outlying drains  50  and the corresponding flow tubes  54  of outlying intervals  102 ,  104 . This type of sampling can be referred to as focused sampling, however other applications can utilize normal sampling in which formation fluid is collected through a single zone/interval. 
         [0050]    As described above, well system  20  can be constructed in a variety of configurations for use in many environments and applications. The single packer  26  can be constructed from a variety of materials and components for collection of formation fluids from single or multiple intervals within a single expansion zone. The ability to expand a sealing element across the entire expansion zone enables use of packer  26  in a wide variety of well in environments, including those having weak unconsolidated formations. The movable members  82  can be designed to pivot about an axis generally parallel with a longitudinal axis of the packer or to pivot about other axes to accommodate movement of flow tubes  54  without stressing, bending, or otherwise changing the orientation of the flow tubes. The movable members  82  also can be connected to flow tubes  54  and to collector portions  76  by other mechanisms that afford members  82  the desired mobility to accommodate radial movement of flow tubes  54 . Additionally, the number of drains and corresponding flow tubes can vary from one application to another, and the location of the flow tubes relative to the outer layer can be changed as desired for specific well applications. 
         [0051]      FIG. 21  shows a method of curing a packer assembly  110  according to one embodiment of the present invention. Note that the packer assembly  110  may include any of the embodiments described above and may be used for any of the purposes/wellbore operations described above. In the depicted embodiment, the packer assembly  110  is of a single packer configuration. However, in other embodiments the packer assembly  110  may have a dual packer configuration or any other appropriate configuration. In addition, the curing method described herein is not limited to any particular packer configuration or to any particular wellbore operation in which the packer assembly  110  is ultimately used. 
         [0052]    As shown in  FIG. 20 , the packer assembly  110  includes an inflatable packer  126 , composed of a rubber material, that is placed on a mandrel  144 . This inflatable packer  126  may include an inner inflatable bladder (such as that described above with respect to reference numeral  42 ); and an outer layer (such as that described above with respect to reference numeral  40 ). In addition, the mandrel  144  may include openings or passages for directing fluid to the inner inflatable bladder during an inflation thereof. A polyamide bandage  120  is wrapped around the exposed rubber of the inflatable packer  126  to compact it during a curing operation. 
         [0053]    To protect the rubber of the inflatable packer  126  and the polyamide bandage  120  from oxidization, a sealing layer  130 , such as an additional rubber layer, is disposed around the inflatable packer  126  and the polyamide bandage  120 , to seal these layers  126  and  120  from exposure to air. This sealing layer  130  may also be compacted by wrapping it in an additional or outer polyamide bandage  140 . 
         [0054]    In one embodiment, the sealing layer  140  may be composed of any material able to seal and protect the rubber of the inflatable packer  126  from being exposed to air. Such materials include a polymeric material such as a rubber material, a silicone material, or a polyamide film, among other appropriate materials. 
         [0055]    The entire packer assembly  126  may then be cured in a pressurized air autoclave, such as a 6 bar air autoclave. During this curing, only the outer polyamide bandage  140  and the sealing layer  130  are exposed to the high pressure air. Although, the outer polyamide bandage  140  and the sealing layer  130  will oxidize during curing, the inner polyamide bandage  120  and the rubber of the inflatable packer  126  are protected against oxidation, resulting in a cured inflatable packer with improved rubber quality. 
         [0056]    In one embodiment, the quality of the cured rubber of the inflatable packer  126  may be further enhanced by performing a vacuum operation between the sealing layer  130  and the inflatable packer  126 . 
         [0057]    In another embodiment according to the present invention, as shown in  FIG. 21 , a packer assembly  210  includes an inflatable packer  226 , composed of a rubber material, that is placed on a mandrel  244 . A polyamide bandage  220  is then wrapped around the exposed rubber of the inflatable packer  226  to compact it during a curing operation. In this embodiment, the polyamide bandage  220  includes an anti-oxidation layer which protects the underlying rubber of the inflatable packer  226  from exposure to air. 
         [0058]    The entire packer assembly  210  may then be cured in a pressurized air autoclave, such as a 6 bar air autoclave. During this curing, the anti-oxidation layer within the polyamide bandage  220  protects the rubber of the inflatable packer  226  against oxidation, resulting in a cured inflatable packer with improved rubber quality. 
         [0059]    Note that any of the polyamide bandages (i.e. layers  120 ,  140  and/or  220  discussed above) may be coated with a non-sealing anti-oxidant, or include an oxidation inhibiting additive. This coating or additive will protect the polyamide bandage to which it is applied, but will not necessarily protect any underlying layers. 
         [0060]    The preceding description has been presented with references to certain exemplary embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings. Instead, the scope of the application is to be defined by the appended claims, and equivalents thereof.