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. 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.
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.
In general, the present invention provides a system and method for collecting formation fluids through a single packer having one or more sample collectors disposed along an expandable packer element. Additionally, an anti-expansion device is deployed along the expandable packer element to limit expansion in localized regions. Depending on the application, the localized regions may be proximate individual sample collectors to effectively provide space between each sample collector and a surrounding wellbore wall. The spacing helps maximize the production surface of the single packer. In some embodiments, the presence of more than one localized region enables performance of focused sampling.
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
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.
The present invention generally relates to a system and method for collecting formation fluids through an individual sample collector or a plurality of sample collectors disposed along an expandable packer element. The collected formation fluids are conveyed through tubes within the packer to a tool flow line and then directed to a desired collection location. Use of the single packer enables collection applications with 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 is a single packer, the expandable packer sealing element 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. Also, a plurality of sample collectors can be used to perform focused sampling with the single packer.
The single packer can be expanded across an expansion zone, and formation fluids are collected from the middle of the expansion zone, i.e. between axial ends of the outer sealing layer. The expansion ratio is limited at localized regions within the expansion zone between ends of the packer sealing element. For example, the expansion ratio can be limited in the one or more collecting zones in which fluid collectors are used to collect formation fluid. By restricting expansion of the packer at specific regions, the fluid collectors can be prevented from contacting the surrounding wellbore wall which, in turn, increases the production surface through which fluid samples are collected.
Referring generally to
Referring generally to
In the illustrated embodiment, anti-expansion device 40 comprises a plurality of reinforcement/anti-expansion rings 52 arranged to restrict expansion of expandable element 42 proximate sample collectors 48. The reinforcement rings 52 can be disposed around or within expandable element 42. For example, if expandable element 42 comprises an inflatable bladder, the reinforcement rings 52 can be disposed around or within the material used to form the inflatable bladder.
As further illustrated in
Referring again to
In the embodiment of
The anti-expansion rings 52 can be constructed in a variety of forms with a variety of materials, depending on the desired performance of each ring. Additionally, the anti-expansion rings 52 used with a given packer 26 can have differing sizes, constructions and materials. In one embodiment, the anti-expansion rings 52 are designed as non-expandable rings. For example, the rings 52 may be formed of high strength materials, such as steel, stainless steel, or other high strength, corrosion resistant materials. In other applications, the anti-expansion rings 52 can be designed to allow a certain level or degree of expansion in which the expansion rings allow expandable element 42 to expand a portion of the distance toward the surrounding wellbore wall 32.
In the latter example, anti-expansion rings 52 are formed from a material or a combination of materials that are strong while allowing some expansion. One approach to enabling a limited expansion is to form the anti-expansion rings 52 with folded synthetic fibers, as illustrated in
An alternate embodiment of anti-expansion device 40 is illustrated in
The packer reinforcement structure 72 is arranged to limit expansion in localized regions 58 via an angle variation of the packer reinforcement structure. If, for example, packer reinforcement structure 72 comprises a plurality of cables or fibers 74, the cables or fibers are positioned generally longitudinally through, or along, expandable element 42 at predetermined angles relative to a longitudinal packer axis 76. The predetermined angles are selected to restrict expansion of expandable element 42 at the desired localized regions 58, while allowing expansion of expandable element 42 at adjacent regions throughout expansion zone 30.
In one example, the packer reinforcement structure 72 comprises a series of segments labeled α1 and α2 in which the angle relative to packer axis 76 is selected to allow expansion (α1) or to restrict expansion (α2). Although different angles can be selected to control the degree of expansion, the angle in the α1 regions may be in the range between 10° and 20° relative to packer axis 76, which allows free expansion of the packer in these regions. The angle in the α2 regions is substantially larger such that during expansion of expandable element 42, the packer reinforcement structure 72 limits or prevents expansion in those particular regions. Accordingly, cables or fibers can be used to control the expansion of packer 26 in a manner that allows free expansion in certain predetermined regions while limiting or preventing expansion in other localized regions. The one or more localized regions of limited expansion facilitate focused sampling within the expansion zone of a single expandable packer. It should be noted that a variety of packer reinforcement structure angles can be selected pursuant to the desired control over single packer expansion.
The fluid samples drawn from surrounding formation 28 can be collected and handled by a variety of mechanisms and packer configurations. In
In operation, fluid samples are collected by drawing fluid from the surrounding formation 28 through a port 80 of each collector 48 by creating a pressure differential. The pressure differential can be created by pumps, such as a cleaning pump 82 and a sampling pump 84. In the illustrated example, cleaning pump 82 is connected to outlying collectors 48 via a flow tubing 86, and sampling pump 84 is connected to a middle collector 48 via a flow tubing 88. However, a variety of other arrangements of pumps, tubing, and collectors 48 can be used in other applications.
By placing flow tubing 86 and flow tubing 88 within mandrel 44, bending forces acting on the flow tubing are avoided. As a result, tubes 78 are designed to accommodate at least some expansion and contraction in localized regions 58 during expansion and contraction of packer 26. To the extent such expansion and contraction of the expandable packer element 42 occurs in the localized regions, the telescopic design of each tube 78 allows the entry port to move as needed in a radial direction.
An alternate embodiment is illustrated in
The overall well system 20 can be constructed in a variety of configurations for use in many environments and applications. Additionally, 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 restriction of expansion in one or more localized regions provides an increased production surface for drawing in fluid samples from the surrounding formation. The anti-expansion mechanisms used to restrict expansion at these localized regions, however, can be formed with various materials and configurations that are incorporated into expandable packer element 42 or used in cooperation with the expandable packer element. The collectors can be formed as one or more drains, windows, ports or other openings through which the formation fluid flows during collection. Additionally, the number and arrangement of collectors and corresponding flow tubes can vary from one application to another. For example, flow tubing 50, 86, 88 can be deployed within inner mandrel 44, along outer layer 54 or through various other sections of packer 26.
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 of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.