Patent Publication Number: US-9428987-B2

Title: Single packer with a sealing layer shape enhanced for fluid performance

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     None. 
     FIELD OF THE INVENTION 
     The present disclosure generally relates to evaluation of a subterranean formation. More specifically, the present disclosure relates to a packer tool with a sealing layer. 
     BACKGROUND INFORMATION 
     For oil and gas exploration, information about subsurface formations that are penetrated by a wellbore is necessary. Measurements are essential to predicting production capacity and production lifetime of a subsurface formation. Collection and sampling of underground fluids contained in subterranean formations are well known. Moreover, testing of a formation may provide valuable information regarding the properties of the formation and/or the hydrocarbons associated therewith. In the petroleum exploration and recovery industries, for example, samples of formation fluids are collected and analyzed for various purposes, such as to determine the existence, composition and producibility of subterranean hydrocarbon fluid reservoirs. This aspect of the exploration and recovery process is crucial to develop exploitation strategies and impacts significant financial expenditures and savings. 
     A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a tubing string, and a packer sealing element is expanded against the surrounding wellbore wall to isolate a region of the wellbore. The sealing layer of the sealing element is typically a uniformly-surface, cylindrical layer of rubber/elastomer. Often, two or more packers may be used to isolate several regions in a variety of well related applications, including production applications, service applications and testing applications. 
     Isolating a particular section of a wellbore typically involves deploying a dual packer system. Deploying a dual packer system is more involved than deploying a single packer since a greater likelihood that one packer may fail exists. Therefore, a single packer is desired which may be deployed in a formation to isolate a portion of the wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  generally illustrate a typical packer system of the prior art. 
         FIG. 3  generally illustrates an example of a packer with expansion rings in accordance with one or more aspects of the present disclosure. 
         FIG. 4  shows an example of a well system in which one or more embodiments of the present disclosure may be used. 
         FIG. 5  generally illustrates an example of a packer with a composite outer layer in accordance with one or more aspects of the present disclosure. 
         FIG. 6  generally illustrates an example of a packer with an irregular outer layer in accordance with one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness. 
     Aspects generally relate to a system and method for collecting formation fluids using a single packer with rings and/or an irregular sealing layer. Use of the single packer with rings enables 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. In at least some embodiments, the single packer may support the formation in hydrocarbon-yielding zone at which formation fluids are collected. The single packer configuration facilitates relatively large amplitude draw-downs even in weak, unconsolidated formations. 
     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 single packer. The formation fluid is collected and directed along flow lines, e.g. along flow tubes, from the one or more 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 bowlines can be connected to different drains, e.g. sampling drains and guard drains, to enable the collection of unique formation fluid samples. 
     The single packer provides a simplified packer structure that facilitates, for example, focused sampling. The outer flexible layer may also be used to contain drains, such as groups of drains in which a middle group has sampling drains and two axially outer groups have guard drains. The drains may be coupled to the bowlines in a manner that facilitates expansion and contraction of the single packer. 
     Referring now to  FIG. 1 , one embodiment of a typical packer assembly  20  of the prior art is illustrated as deployed in a wellbore  22 . In this embodiment, the packer assembly  20  has an inflatable single packer  24  having an outer flexible skin  26  formed of expandable material, e.g. a rubber material, which allows for inflation of the packer  24 . The outer flexible skin  26  is mounted around a packer mandrel  28  and has openings for receiving drains  30 . By way of example, the drains  30  may have one or more sampling drains  32  positioned between guard drains  34 . The drains  30  are connected to corresponding flow lines  36  for transferring fluid received through the corresponding drains  30 . The flow lines  36  connected to the guard drains  34  may be separated from the flow lines  36  connected to the sample drains  32 . 
     The packer  24  is a single packer having an outer layer formed of an outer flexible skin  26  made from an elastic material, e.g. rubber. The outer flexible skin  26  is expandable in a wellbore to seal with a surrounding wellbore wall. The single packer  24  has an inner inflatable bladder  148  disposed within the outer flexible skin  26 . By way of example, the inner bladder  148  may be selectively expanded by introducing fluid via the interior packer mandrel  28 . Additionally, the packer  24  has a pair of mechanical fittings  150  that may have fluid collectors  152  coupled with the flow lines  36 . The mechanical fittings  150  are mounted around the inner mandrel  28  and engaged with axial ends of the outer flexible skin  26 . 
     Referring to  FIG. 1 , the outer flexible skin  26  has openings for receiving the drains  30  through which formation fluid is collected when the outer flexible skin is expanded against a surrounding wellbore wall. The drains  30  may be embedded radially into the outer flexible skin  26 . A plurality of the flow lines  36  may be operatively coupled with the drains  30  for directing the collected formation fluid in an axial direction to one or both of the mechanical fittings  150 . In an embodiment, the flow lines  36  are in the form of tubes, and the tubes are connected to the guard drains  34  and the sample drains  32  disposed between the guard drains  34 . The tubes maintain separation between the fluids flowing into the guard drains  34  and the sample drains  32 , respectively. 
     As illustrated in  FIG. 2 , the flow lines  36  may be tubes/conduits oriented generally axially along the packer  24 . The flow lines  36  extend through the axial ends of the outer flexible skin  26 . By way of example, the flow line  36  may be at least partially embedded in the flexible material of the outer flexible skin  26 . Consequently, the portions of the flow lines  36  extending along the outer flexible skin  26  move radially outward and radially inward during expansion and contraction of the packer  24 . One or more mechanical fittings  150  may have collector portions  152  coupled with a plurality of movable members  154 . The movable members  154  are pivotably coupled to each of the collector portions  152  via pivot links for pivotable motion about an axis generally parallel with the packer axis. At least some of the movable members  154  are designed as tubes to transfer fluid received from the flow lines  36 , extending along outer flexible skin  26 , to collector portions  152 . From the collector portions  152 , the collected fluids may be transferred/directed to desired collection/testing locations. The pivotable motion of the movable members  154  enable transition of the packer  24  between a contracted state and an expanded state. The movable members  154  may be designed generally as S-shaped members pivotably connected between flow lines in the outer flexible skin  26  and the collector portions  152 . 
     As described above, the packer assembly  20  may be constructed in a variety of configurations for use in many environments and applications. The packer  24  may be constructed from different types of materials and components for collection of formation fluids from single or multiple intervals within a single expansion zone. The flexibility of the outer flexible skin  26  enables use of the packer  24  in many well environments. Furthermore, the various packer components can be constructed from a variety of materials and in a variety of configurations as desired for specific applications and environments. 
       FIG. 3  illustrates a packer  100  with expansion rings  40 ,  42  in accordance with one or more aspects of the present disclosure. As illustrated, the rings  40 ,  42  may be formed of thick portions of rubber. The rings  40 ,  42  may be composed of the same material used to form the outer flexible skin  126 . Depending on the application, the packer  100  may have one or more of the rings  40 ,  42 . In the illustrated example, the packer  100  has two of the rings  40  to isolate the sample drains  132 . Further, the packer  100  has two of the rings  42  to isolate the guard drains  134 . 
     The rings  40 ,  42  may isolate different portions of the wellbore during testing. Thus, the rings  40 ,  42  may be used for focused sampling of specific portions of a wellbore. That is, the packer  100  may be disposed in a wellbore at any depth to test a particular section of that wellbore. Moreover, the rings  40 ,  42  may enable sampling across a larger surface area. For example, the rings  40 ,  42  may isolate an entire section of the wellbore. Fluid drawn into the sample drains  32  may be extracted from the entire isolated portion. Thus, the rings  40 ,  42  enable any size or type of drain to be used. For example, if a small drain is used, a sufficient amount of fluid may be sampled due to the isolation of an entire section of the wellbore using the rings  40 ,  42 . 
     Further, the rings  40 ,  42  may improve fluid sampling in tight formations. The rings  40 ,  42  may create an air-tight seal in the isolated portion of the wellbore. Thus, the packer  100  may create a larger pressure differential to draw fluid from the tight formation. The outer rings  42  isolating the guard drains  134  may focus contaminated fluid into the guard drains  134 . Thus, the segregation of non-contaminated fluid and contaminated fluid may be more effectively implemented. 
     The rings  40 ,  42  may be provided with the packer  100  and/or may be retrofitted to the packer  100 . The rings  40 ,  42  may be installed and/or removed depending on the formation and/or the desired sampling method. The rings  40 ,  42  may be permanently affixed to the packer  100  by welding, fasteners, and/or cement. The placement of the rings  40 ,  42  may also be customized depending on a desired application. For example, in a formation with increased contaminants in the fluid, a larger guard drain section may be desired. 
     In the illustrated embodiment, the packer  100  has four rings: two inner rings  40  and two outer rings  42 . The rings  40 ,  42  define three contiguous sections  51 ,  52 ,  53 . The first section  51  and the third section  53  may contain guard drains  134 . The second section  52  may contain sample drains  132 . 
       FIG. 4  shows an example of a well system  20  in which one or more embodiments of the present disclosure may be used. In this example, the well system  20  has a rig  22  used to deliver a tool  21  downhole into a wellbore  19 . The rig  22  is positioned at a surface location  18 , such as a land surface location, from which the wellbore  19  is drilled. Depending on the specific application, the tool  21  may have various components and/or assemblies used in a variety of well related operations. One of the components may be a packer assembly  100  according to one or more embodiments of the present disclosure. As illustrated, the packer assembly  100  is delivered downhole via a well string  31 , e.g. a tubing string, to a desired location in the wellbore  19 . After lowering the well string  31  into the wellbore  19 , the packer assembly  100  is inflated until the outer sealing layer  126  abuts a wall  17  of the wellbore  19 . The rings  40 ,  42  isolate portions of the wellbore  19 . Sampling of formation fluid  23  is carried out via the drains  132 ,  134  of the packer assembly  100 . 
     When deployed and expanded in a wellbore  19 , the three sections  51 ,  52 ,  53  may enclose three corresponding sections of the wellbore. The rings  40 ,  42  create a temporary seal between the packer  100  and walls  17  of the wellbore. A pressure differential may be initiated in the packer  100  to draw fluid from the formation  23  into the drains  132 ,  134 . 
       FIG. 5  illustrates the packer  100  with an irregular sealing layer  45  in accordance with one or more embodiments. The irregular sealing layer  45  may form grooves in the rubber of the outer diameter of the packer  100 . The grooves  44  may create a leak path between the drains  32 ,  34  of the packer  100 . Moreover, when used in embodiments of the packer  100  with the expansion rings  40 ,  42 , the grooves  44  may guide sample fluid into the drains  132 ,  134  from a sealed portion of the wellbore  19 . Thus, in the embodiment with the expansion rings  40 ,  42 , the grooves  44  effectively create one large sampling inlet between each pair of the rings  40 ,  42 . The irregular sealing layer may be used in combination with or without the expansion rings  40 ,  42 . 
     In practice, when the packer  100  is expanded to abut the walls  17  of the wellbore  19 , the outer diameter of the packer  100  is flush against the wall of the wellbore  19 . Without the grooves  44 , fluid may only be drawn into the drains  132 ,  134  from that portion of the wall  17  that is directly abutted to the drain  132 ,  134 . However, the grooves  44  create leak paths through which sample fluid may flow. The leak paths formed by the grooves  44  may carry fluid to one or more of the drains  132 ,  134 . 
     In  FIG. 6 , the irregular sealing layer  45  may be a composite material  46  composed of technical fibers/textiles and/or plastic. The technical fibers may be a non-aesthetic textile material used to increase strength and provide certain properties depending on the application. Permeable technical fibers, such as geo-textiles, may be used in embodiments. The composite material  46  may be semi-permeable such that fluid may flow through the material, but solids may not flow through the material. Thus, the composite material  46  may prevent contamination of samples. The composite material  46  may also facilitate fluid flow when the outer diameter of the packer  100  is abutted to a formation wall  17 . 
     In the embodiments described above where a component is described as formed of rubber or comprising rubber, the rubber may include an oil resistant rubber, such as NBR (Nitrile Butadiene Rubber), HNBR (Hydrogenated Nitrile Butadiene Rubber) and/or FKM (Fluoroelastomers). In a specific example, the rubber may be a high percentage acrylonytrile HNBR rubber, such as an HNBR rubber having a percentage of acrylonytrile in the range of approximately 21% to approximately 49%. Components suitable for the rubbers described in this paragraph include, but are not limited to, the outer flexible skin  26  and the inflatable bladder  148 . 
     In one embodiment a system for collecting fluid in a wellbore is disclosed comprising an outer flexible skin having an outer diameter, a plurality of rings disposed around the outer diameter, a plurality of drains coupled to the outer flexible skin, and a mandrel positioned within the outer flexible skin. In another embodiment, a method is disclosed comprising deploying a packer assembly into a wellbore wherein the packer assembly inflates toward a wall of the wellbore and has an opening connected to a flow line for receiving fluid and two exterior rings extending around a circumference of the packer assembly; expanding the packer assembly such that the exterior rings abut the wall of the wellbore; isolating a section of the wellbore by creating a seal between the wellbore wall and the exterior rings and obtaining fluid through the opening. In still another embodiment, a sampling tool is disclosed comprising an outer sealing layer having irregularities, a plurality of drains coupled to the outer sealing layer, a flow line connected to an opening for moving the fluid into the packer assembly, and a mandrel positioned within the outer flexible skin. 
     Although exemplary systems and methods are described in language specific to structural features and/or methodological acts, the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claimed systems, methods, and structures. Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings above.