Abstract:
Porous objects, such as porous balls, may be employed within telescoping devices to control proppant flowback through a completed well during production. The telescoping devices may connect a reservoir face to a production liner without perforating. Acid-soluble plugs initially disposed within the telescoping devices may provide enough resistance to enable the telescoping devices to extend out from the production liner under hydraulic pressure. The plugs may then be dissolved in an acidic solution, which may also be used as the hydraulic extension fluid. After the plugs are substantially removed from the telescoping devices, the reservoir may be hydraulically fractured using standard fracturing processes. The porous balls may then be inserted into the telescoping devices to block proppant used in the fracturing process from flowing out of the reservoir with the production fluids.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Ser. No. 12/723,983, filed Mar. 15, 2010. 
    
    
     TECHNICAL FIELD 
     The present invention relates to methods and compositions for controlling proppant flow through a wellbore, and more particularly relates, in one embodiment, to methods and compositions for controlling proppant flow through a wellbore after proppant fracturing. 
     BACKGROUND 
     There are a number of procedures and applications that involve the formation of a temporary seal or plug while other steps or processes are performed, where the seal or plug must be later removed. Often such seals or plugs are provided to temporarily block a flow pathway or inhibit the movement of fluids or other materials, such as flowable particulates, in a particular direction for a short period of time, when later movement or flow is desirable. 
     The recovery of hydrocarbons from subterranean formations often involves applications and/or procedures employing coatings or plugs. In instances where operations must be conducted at remote locations, namely deep within the earth, equipment and materials can only be manipulated at a distance. One such operation concerns perforating and/or well completion operations incorporating filter cakes and the like as temporary coatings. 
     Generally, perforating a well involves a special gun that shoots several relatively small holes in the casing. The holes are formed in the side of the casing opposite the producing zone. These perforations, or communication tunnels, pierce the casing or liner and the cement around the casing or liner. The perforations go through the casing and the cement and a short distance into the producing formation. Formations fluids, which include oil and gas, flow through these perforations and into the well. 
     The most common perforating gun uses shaped charges, similar to those used in armor-piercing shells. A high-speed, high-pressure jet penetrates the steel casing, the cement, and the formation next to the cement. Other perforating methods include bullet perforating, abrasive jetting, or high-pressure fluid jetting. 
     The characteristics and placement of the communication tunnels can have significant influence on the productivity of the well. Technology has been developed which eliminates the need for perforating guns and enables significantly more controlled perforation through the use of fluid conduits installed within casings. These fluid conduits may be extended out from the casing to contact a formation wall, thereby forming “perforations” at desired locations along the length of the casing. Temporary plugs in the conduits form fluid barriers, and the conduits are pushed out from the casing via fluid pressure. The plugs may be made of a porous filter structure on which a degradable barrier material is coated. After the fluid conduits are extended, the degradable material may be removed, thereby allowing the flow of fluids through the filter structure. This technology, known as TELEPERF™ from Baker Hughes Inc, is described in more detail in U.S. Pat. Nos. 7,527,103 and 7,461,699, each incorporated by reference herein its entirety. 
     In some instances, it may be necessary or desirable to fracture a formation to enable or promote the flow of fluids therethrough. For example, in low-permeability reservoirs, it may be beneficial to fracture the well formation and inject proppants into the fractures to stimulate the flow of fluids (such as oil, gas, water, and the like) through the formation. When hydraulic fracturing is performed, the viscous fracturing fluids mixed with proppant are flowed into the formation through the casing and associated perforations. However, filters in the above-described TELEPERF™ devices may obstruct or impede the high-viscosity fluids and proppants utilized in hydraulic fracturing from entering the formation. 
     Accordingly, hydraulic fracturing may be accomplished in TELEPERF™ devices by temporarily plugging the telescoping conduits to inhibit the flow of fluid therethrough. Hydraulic pressure telescopes the flow conduits outward, and the temporary plugs may then be removed from the flow conduits via an acidic solution. High-viscosity fluids and proppants may then be injected to fracture the subterranean reservoir. This technology, known as TELEFRAC™ from Baker Hughes Inc, is described in more detail in U.S. patent application Ser. No. 12/723,983, which is herein incorporated by reference its entirety. 
     Although the TELEFRAC™ method described above enables proppant fracturing through the TELEPERF™ tunnels, the system does not provide for a filter structure through which the formation fluids may be returned to the well surface. It may be desirable to filter the formation fluids in order to control proppant flow back into the wellbore. Ensuring that the proppant remains in the fracture will increase the fracture integrity in the near wellbore region and maintain higher productivity that results from well fracturing. 
     SUMMARY 
     There is provided, in one non-limiting form, a method for extracting well fluids from a fractured hydrocarbon formation while controlling the flow of proppant back through the wellbore. The hydrocarbon formation has disposed within it a pipe having orifices through at least a region of its wall, and telescoping flow conduits, pathways, channels, passages, outlets, or the like situated within the orifices in a retracted position within the pipe. The telescoping flow conduits contain porous objects disposed within them to control the flow of proppant and sand from the formation. The hydraulic fracturing method includes extending the telescoping flow conduits radially outward from the pipe in the direction of the wellbore wall via an extension fluid. Hydraulic fracturing fluid may then be injected into the subterranean reservoir via the pipe and the telescoping flow conduits. The porous objects are then injected into the telescoping flow conduits to control the flow of proppant and formation sand into the wellbore during production of the formation. 
     In another non-limiting embodiment of the present disclosure, a system or apparatus may be provided for use in well completions. The system may include a pipe, such as a conductor pipe, a casing, a tubing, a liner, or the like. Through the wall of the pipe are disposed telescoping flow conduits made of at least two sleeves. In one exemplary embodiment, the first sleeve is attached to the pipe wall, and the second sleeve is disposed within the first sleeve and is moveable relative to the first sleeve. The second sleeve may contain an acid-soluble plug which temporarily blocks, inhibits, or prevents flow through the sleeve. The inhibited flow enables the second sleeve to be moved relative to the first sleeve via hydraulic pressure. After the plug is dissolved using an acidic solution, a porous ball may be inserted into the second sleeve to serve as a filter or a sand control screen during production of the well. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section schematic view of a wellbore having an oil well casing or tubing disposed therein which has a plurality of telescoping conduits therein, each in a retracted position in an orifice in the casing and having a dissolvable plug therein 
         FIG. 2  is a cross-section schematic view of the telescoping conduit of  FIG. 1 ; 
         FIG. 3  is a cross-section schematic view of the oil well casing of  FIG. 1  having a plurality of telescoping conduits therein, where the conduits have been extended or expanded in the direction of the wellbore wall; 
         FIG. 4  is a cross-section schematic view of the oil well casing of  FIG. 1  having a plurality of telescoping conduits therein, where the plugs in the conduits have been removed and porous objects have been introduced into the casing and the conduits; 
         FIG. 5  is a cross-section schematic view of the oil well casing of  FIG. 1  having a plurality of telescoping conduits therein, where the conduits have been fully extended and have the porous objects of  FIG. 4  disposed therein; 
         FIG. 6  is a cross-section schematic view of the telescoping conduit of  FIG. 1  in a fully extended position; and 
         FIG. 7  is a perspective view of a sleeve of the telescoping conduit of  FIG. 1  having collet fingers with tabs. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with a present embodiment, an oil well casing or liner may contain pre-formed perforations, or holes, therethrough. Further, installed in each perforation may be a moveable fluid conduit or pathway which enables fluid communication between the interior and the exterior of the casing or liner. For example, the fluid conduit may be several generally cylindrical conduits arranged coaxially with a limited range of motion relative to each other along the commonly shared axis, e.g. in a telescoping configuration. 
     The flow conduits or pathways may further contain temporary plugs which inhibit or prevent the flow of fluid through the conduits. The moveable flow conduits or pathways may be telescoped out from the casing or liner into the wellbore annulus via fluid pressure within the casing or liner. That is, as fluid is pumped into the casing, the temporary plugs inhibit the fluid from exiting the casing via the flow conduits. Rather, as the pressure inside the casing increases, the flow conduits are pushed outward from the casing. Optimally, the flow conduits contact the wellbore wall, thereby forming a flow pathway through the annulus from the interior of the casing to the formation. In this manner, the described structure may be used as a completion tubular to avoid using a cementing and perforation process. After the assembly is in place across the producing zone location, the temporary plugs may be dissolved using an acidic solution. 
     A hydraulic fracturing fluid may then be pumped through the casing, out the flow conduits, and into the formation. The fluid may fracture the formation, thereby increasing its permeability and stimulating production. In addition, proppants may be used in the fluid to keep the fracture open after the procedure has been completed. In an exemplary embodiment, porous media may then be disposed within the flow conduits to inhibit return of the proppants during production of the formation. 
     The well completion system will now be described more specifically with respect to the figures, where in  FIG. 1  there is shown a cross-section of a vertically oriented, cylindrical casing or liner  10  having a plurality of orifices  12  therethrough. The orifices  12  may be created by machining or other suitable technique. The casing  10  is placed in a borehole or wellbore  14  through a subterranean reservoir  16 . The subterranean reservoir  16  may be a flow source from which gas and/or oil is extracted or, alternatively, a flow target into which gas or water is injected. The wellbore  14  has a wall  18  coated with a filter cake  20  deposited by a drilling fluid or, more commonly, a drill-in fluid or completion fluid  22 . In some non-limiting embodiments, the filter cake  20  may be optional. The casing  10  and the wall  18  define an annulus  24  there between. 
     Flow conduits  26  such as that shown in  FIG. 2  may be disposed within the orifices  12 . The flow conduits  26  are shown in  FIG. 1  in a retracted position within the casing  10 . The flow conduit  26  may be a series of sleeves  28 - 31  open on opposing ends having an enveloping wall defining their shape. It should be understood that although the exemplary flow conduit  26  is made up of four sleeves  28 - 31 , any number of sleeves may be used in accordance with a present embodiment. In the exemplary embodiment, the sleeves  28 - 31  are generally cylindrical and have different internal diameters  34 - 37  and external diameters  38 - 41 . The sleeves  28 - 31  may be arranged concentrically with respect to one another along a common axis  44  such that the first sleeve  28  having internal diameter  34  and external diameter  38  is disposed within the second sleeve  29  having internal radius diameter  35  and external diameter  39 , which in turn is disposed within the third sleeve  30  having internal diameter  36  and external diameter  40 , which is further disposed within the fourth sleeve  31  having internal diameter  37  and external diameter  41 . Further, each sleeve  28 - 31  may be moveable with respect to the other sleeves  28 - 31  along the axis  44 . 
     The flow conduits  26  contain temporary plugs  46  made of a soluble substance having low permeability and high strength. For example, the plug  46  may be Indiana limestone having an acid solubility greater than 70% and permeability of less than 10 mD. Although the present disclosure refers to the soluble substance of the plugs  46  as limestone, it should be understood that other materials having similar solubility, permeability, and strength may be utilized in the disclosed methods and systems. In a non-limiting embodiment, the plug  46  may be pre-formed and secured within one or more of the sleeves  28 - 31 . For example, the plug  46  may be inserted into the sleeve  28  and abutted against the inside of a flange  48 . In other embodiments, the plug  46  may be force fit into one or more of the sleeves  28 - 31  or disposed at an end of one of the sleeves  28 - 31  via a threaded hollow cap. 
     Once the casing  10  is placed or positioned in the wellbore  14 , a fluid  50  may be pumped through the casing  10  and the conduits  26 , as shown in  FIG. 3 . As noted above, the plugs  46  within the conduits  26  have a very low permeability; accordingly, flow of the fluid  50  through the plugs may be substantially or completely inhibited. As the fluid  50  is pumped into the casing  10 , enough hydraulic pressure is built up to extend the flow conduits  26  radially outward from the casing  10  into the annulus  22 , such that the flow conduits  26  may be in contact with the producing formation  16 . That is, the conduits  26  may be extended out from the casing  10  in a direction generally perpendicular to a longitudinal axis  52  of the casing  10 . The hydraulic pressure of the fluid  50  typically causes the conduits  26  to extend to a position in which the conduits  26  touch or nearly touch the wall  18 . 
     An acidic solution, such as dicarboxylic acid, may then be pumped into the casing  10  to dissolve the plugs  46 , thereby forming flow paths  54  through the annulus  24  between the casing  10  and the formation  16 , as shown in  FIG. 3 . The acidic solution may also dissolve the portions of the filter cake  20  (if present) with which it comes into contact. Fracturing fluids containing proppants may then be flowed through the casing  10  at high pressure to fracture the formation  16  in accordance with techniques well known in the art. Because the limestone plugs  46  may be substantially removed and do not leave behind a porous substrate to act as a filter, the proppants, such as grains of sand or the like, are not hindered from flowing into the fractures (not shown) created in formation  16 . 
     In a non-limiting embodiment, the fluid  50  used to extend the conduits  26  may also be utilized to dissolve the plugs  46 . That is, the fluid  50  may be an acidic solution having a low enough chemical reaction rate with the limestone plugs  46  that the plugs  46  begin slowly dissolving while the hydraulic pressure of the extension fluid  50  pushes the conduits  26  outward toward the wellbore wall  18 . After the conduits  26  are extended out to touch the face of the reservoir  16 , the acidic fluid  50  may continue to be pumped into the casing  10  to substantially dissolve the plugs  46 . It should be understood that the method herein is considered successful if the plugs  46  dissolve sufficiently to open up the flow conduits  26  enough to enable flow of viscous fracturing fluids and proppants therethrough. 
     After the well is fractured, porous objects  56  may be introduced into the casing  10  and pumped into the fluid conduits  26  via a pressurized fluid flow, as illustrated in  FIG. 4 . After the porous objects  56  are propagated throughout the casing  10  into the fluid conduits  26 , the well may be produced. For instance, hydrocarbons may flow through the fluid conduits  26  from the formation  16  into the casing  10 , through the fluid conduits  26 , and into the formation  16 . 
     In an exemplary embodiment, the porous objects  56  may be generally spherical balls having a diameter approximately equivalent to that of the inner diameter  34  of the sleeve  28 . The balls may be composed of numerous beads (not shown) joined together to form the porous objects  56 . That is, high-strength beads (i.e., stainless steel, alloy, ceramic, and the like) may be bonded together via, for example, sintering or gluing, to form the generally spherical porous balls  56 . The beads may, in one embodiment, be from about 10 mesh (2000 μm) to about 100 mesh (149 μm). Additionally, the beads may be a generally uniform size or may be a variety of sizes. 
     In a non-limiting embodiment, the porous objects  56  may be carried into the extended flow conduits  26  via a flush fluid  58 , such as, for example, brine, potassium chloride solution, non-crosslinked polymer fluid, diesel, foam, or the like. The flush fluid  58  may be pumped through the casing  10  and into the flow conduits  26  with sufficient force to push the porous objects  56  into the fluid conduits  26 . The porous objects  56  may be blocked from escaping the flow conduits  26  by the flanges  48  in the sleeves  28 . 
     As the flush fluid  58  continues to flow into the casing  10  of  FIG. 4 , a high pressure differential may be generated within the casing  10  relative to the annulus  24 , thereby further extending the flow conduits  26  radially outward toward the formation  16 , as illustrated in  FIG. 5 . When the sleeve  28  moves relative to the sleeve  29 , collets  60  on the sleeve  28  may be actuated by contact with a flange  62  on the sleeve  29 . As better illustrated in  FIGS. 5 and 6 , tabs  64  on the collets  60  may abut the flange  62 . As the sleeve  28  moves radially outward from the casing  10  along the axis  44  relative to the sleeve  29 , an angled surface  66  on the flange  62  may come into contact with complimentarily angled surfaces  68  on the tabs  64 . With additional pressure inside the casing  10 , a sufficient force may be generated to push the sleeve  28  still farther out relative to the sleeve  29 . As the angled surface  66  of the flange  62  moves past the angled surface  68  of the tab  64 , the force exerted radially inward toward the axis  44  may be such that the collets  60  are bent inward. When the collets  60  bend inward, the porous objects  56  may become trapped within the sleeve  28  between the flange  48  and the collets  60 . 
     Further features of the sleeve  28  include one or more tabs  70  protruding radially outward from the exterior of the sleeve  28 . These tabs  70  cooperate with an internal surface  72  of a flange  74  protruding radially inward from the interior of the sleeve  29 . Abutment of the tabs  70  with the flange  74  limits movement of the sleeve  28  relative to the sleeve  29 . 
     In addition, concentric rings  76  protrude radially outward from the exterior of the sleeve  28 . These rings  76  may have a buttress-type profile wherein the leading edge of each ring  76  is beveled, for example, at about 30 degrees relative to the exterior of the sleeve  28 , and the trailing edge is generally perpendicular to the exterior of the sleeve  28 . When flow conduit  26  telescopes outward, the sleeve  28  moves along the axis  44  relative to the sleeve  29 , and the beveled edges of the rings  76  move past the internal surface  72  of the flange  74 . The perpendicular edge of the rings  76  then abuts an external surface  78  of the flange  74 , thereby blocking the sleeve  28  from moving the opposite direction along the axis  44  relative to the sleeve  29 . 
     The tabs  70  and rings  76  on the sleeve  28  cooperate with the flange  74  on the sleeve  29  to enable limited movement of the sleeve  28  relative to the sleeve  29  in only one direction along the axis  44 . That is, when the sleeve  28  is expanded outward from the sleeve  29  along the axis  44 , the flange  74  essentially locks the sleeve  28  in place by limiting movement in one direction via abutment with the tabs  70  and in the other direction via abutment with the trailing edge of the rings  76 . The sleeves  29 - 31  may include similar features to enable telescopic expansion and prevent collapse of the flow conduit  26 . 
     CONCLUSION 
     It will be evident that various modifications and changes may be made to the foregoing specification without departing from the broader spirit or scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific materials, fluids, acidic solutions, and combinations thereof falling within the claimed parameters, but not specifically identified or tried in a particular composition, are anticipated to be within the scope of this invention. Additionally, various components and methods not specifically described herein may still be encompassed by the following claims. 
     The words “comprising” and “comprises” as used throughout the claims is to be interpreted as “including but not limited to”. The present invention may suitably comprise, consist of, or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For example, in one non-limiting embodiment, a pipe used in well completions may consist of or alternatively consist essentially of an interior space, an outer surface, at least one flow conduit and a porous object disposed within the flow conduit, as described in the claims.