In recent technology related to downhole drilling and completion, fracturing has become more prevalent. Fractures are created mostly from pressure, however sometimes there will be proppant in the slurry used to pressurize the well and that proppant flows into the fractures once open to maintain the fractures in an open condition. Conventionally, hydraulic-set or swelling packers have been used to divert such proppant, however these can be complicated and subject to failure. Since causing and maintaining fractures to be preferentially in zones of interest is desirable, the art is always receptive to new concepts related thereto.
An apparatus positionable along a downhole string, the apparatus includes a flexible structure retained on a surface of the string in a first condition, the flexible structure movable by a flow to substantially fill an annular space between the string and a radially positioned structure in a second condition.
A method of diverting fracturing treatments in a wellbore, the method includes positioning a downhole apparatus along a string in a wellbore, the apparatus including a flexible structure retained on an outer surface of the string in a first condition; introducing a flow into the wellbore and towards the structure; at least partially swabbing off the structure by the flow; and, moving the flexible structure by the flow and substantially filling an annular space between the pipe string and the wellbore in a second condition.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
With reference to
In one exemplary embodiment, a hydraulic fracture diverter apparatus 10 includes a substantially flexible cylindrical or tubular element 12. The element 12 includes a first end 14 adjacent a first end face 16 and a second end 18 adjacent a second end face 20. The first end 14 may be an upstream end where the first end face 16 faces the flow 64 and the second end 18 may be a downstream end. In one exemplary embodiment, the element 12 may be reversibly positioned on the pipe string 52. In another exemplary embodiment, the upstream and downstream ends may be different such that the element 12 may not be reversibly oriented for proper use. The element 12 also includes an inner surface 22, which may be substantially tubular shaped, and an outer surface 24, which may also be substantially tubular shaped, where the outer surface 24 has a larger outer radius than an inner radius at the inner surface 22. A thickness t of the element 12 may be a difference between the outer radius and the inner radius. In one exemplary embodiment, the thickness t may be constant throughout a length L of the tubular element 12, however in another exemplary embodiment, the thickness t may be different in one section of the tubular element 12 than in another section of the tubular element 12 for controlling liftoff behavior, such as the thickness near the upstream end being thinner than the thickness near the downstream end.
The element 12 is retained on the outer surface 48 of a portion of the pipe string 52, adjacent a zone of interest 60 within the wellbore 54 where fractures are to be maintained and/or diversion of fracturing treatments is desired. The pipe string 52, flexible element 12, first annulus 56, and the formation face 58 of the wellbore 54 are substantially concentrically arranged about a longitudinal axis 66. While the element 12 fills a portion of the first annulus 56, a second annulus 68 remains between the outer surface 24 of the element 12 and the formation face 58 of the wellbore 54. The second annulus 68 is thinner than the first annulus 56 by the thickness t of the element 12. A flow 64 is capable of passing through the wellbore 54 via the second annulus 68 in an initial state or first condition, or at a first flow velocity, because the wellbore 54 is not plugged in this initial state in the vicinity of the element 12.
In an exemplary embodiment, and in the first condition, the element 12 may be retained on the pipe string 52 by elasticity, such that an inner diameter of the inner surface 22 of the element 12 may be less than an outer diameter of the outer surface 48 of the pipe string 52 prior to installation of the element 12 upon the pipe string 52. In another exemplary embodiment, a portion of the element 12 may be retained on the pipe string 52 by adhesive or other securement devices. In an exemplary embodiment employing an adhesive, the adhesive may be applied between the outer surface 48 of the pipe string 52 and the inner surface 22 of the element 12 along an entire length L of the element 12, in one exemplary embodiment, or along a first section, such as between points A and B, in another exemplary embodiment, where point A indicates a point where the element 12 is encouraged to remain on the pipe string 52 and swab off is discouraged. Similarly, a securement device may be positioned at point A to encourage the element 12 to remain on the pipe string 52 at point A and swab off is discouraged.
Turning now to
As shown in
How quickly fracturing treatment is diverted to the area of interest 60 will depend on how quickly the first annulus 56 is plugged by the element 12. If the diversion of fracturing treatment is to be delayed for a certain time period, then the flow 64 past the element 12 can be relatively slow enough not to immediately lift off the element 12 from the pipe string 52, or the element 12 may be sufficiently retained, adhered, or secured to the pipe string 52 so as not to be readily swabbed off, or a combination of a slower flow 64 and an adequately retained element 12 may be employed. On the other hand, if the diversion of fracturing treatment is desired to occur as quickly as possible, then the flow 70 may be hastened towards and past the element 12 to quickly initiate liftoff, or the element 12 may be designed so as not to cling too tightly to the pipe string 52, or a combination of a quicker flow and a relatively loosely fitted element 12 may be employed.
The element 12 on the outer surface 48 of the pipe string 52 may be constructed in a variety of ways to achieve the desired liftoff behavior. It can be fully or partially bonded to encourage liftoff above a certain flow regime, and its stiffness can be varied axially to the same effect. The design and retention of the element 12 will dictate the repeatability and effectiveness of the “swab off” behavior as a fracturing diverter. Any of the above described or below mentioned techniques or combinations thereof are within the scope of these embodiments. In exemplary embodiments, the element 12 may be constructed from an elastomer and a thickness, length, and stretch over the outer surface 48 of the pipe string 52 may be selected so that low flow rates allow it to remain in place, but higher flow rates cause “liftoff”. In other exemplary embodiments, the elastomeric properties along the length of the element 12 may be varied to encourage liftoff at the desired rate. In yet other exemplary embodiments, reinforcing materials may be embedded in the element 12 to further control the liftoff behavior. In still other exemplary embodiments, the element 12 may be bonded or partially bonded to control the liftoff and post-liftoff behavior (encourage folding, for example). In still other exemplary embodiments, a portion of the element 12 may be mechanically retained to control liftoff and post-liftoff shape (clamps, bands, interference fits, etc.) And in yet other exemplary embodiments, an upset or a plurality of upsets may be placed in the first annulus 56 downstream of the element 12 to act as backup or to encourage a specific post liftoff shape.
An element has been described wherein flow changes the position and/or the shape of the element so that the element in a first condition allows the flow to pass and in a second condition acts as a restrictor to the flow. Although the element has been described as blocking the flow within a wellbore, it should be understood that the element may function regardless of what annulus it is positioned in, including a casing that is within a wellbore, or within an inner diameter of a string which could cause an automatic restriction if fluid flow velocity exceeded a threshold velocity, or be used in other downhole endeavors such as CO2 sequestration for example. Also, while the element has been described primarily as a tubular member, in other exemplary embodiments, the element may not be tubular for various applications such as when flow is to be directed at one portion of the annulus for example, or the element may be one of a number of parts that together form the annular restriction when lifted off the string.
While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
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Number | Date | Country | |
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20120234547 A1 | Sep 2012 | US |