Abstract:
Of the many assemblies and methods provided herein, one assembly includes a conduit adapted for installation in a well bore in a subterranean formation; one or more fluid jet forming nozzles disposed about the conduit; and one or more windows formed in the conduit and adapted to selectively allow a flow of a fluid through at least one of the one or more fluid jet forming nozzles. Another assembly provided herein includes a conduit adapted for installation in a well bore in a subterranean formation; one or more fluid jet forming nozzles disposed about the conduit; a fluid delivery tool disposed within the conduit, wherein the fluid delivery tool is operable to move along the conduit; a straddle assembly operable to substantially isolate the fluid delivery tool from an annulus formed between the fluid delivery tool and the conduit; and wherein the conduit comprises one or more permeable liners.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to subterranean treatment operations, and more particularly to methods of isolating local areas of interest for subterranean treatment operations. 
         [0002]    In some wells, it may be desirable to individually and selectively create multiple fractures along a well bore at a distance apart from each other. The multiple fractures should have adequate conductivity, so that the greatest possible quantity of hydrocarbons in an oil and gas reservoir can be drained/produced into the well bore. When stimulating a reservoir from a well bore, especially those well bores that are highly deviated or horizontal, it may be difficult to control the creation of multi-zone fractures along the well bore without cementing a liner to the well bore and mechanically isolating the subterranean formation being fractured from previously-fractured formations, or formations that have not yet been fractured. 
         [0003]    One conventional method for fracturing a subterranean formation penetrated by a well bore has involved cementing a solid liner in the lateral section of the well bore, performing a conventional explosive perforating step, and then performing fracturing stages along the well bore. Another conventional method has involved cementing a liner and significantly limiting the number of perforations, often using tightly-grouped sets of perforations, with the number of total perforations intended to create a flow restriction giving a back-pressure of about 100 psi or more; in some instances, the back-pressure may approach about 1000 psi flow resistance. This technology generally is referred to as “limited-entry” perforating technology. 
         [0004]    In one conventional method of fracturing, a first region of a formation is perforated and fractured, and a sand plug then is installed in the well bore at some point above the fracture, e.g., toward the heel. The sand plug may restrict any meaningful flow to the first region of the formation, and thereby may limit the loss of fluid into the formation, while a second, upper portion of a formation is perforated and fracture-stimulated. Coiled tubing may be used to deploy explosive perforating guns to perforate subsequent treatment intervals while maintaining well control and sand-plug integrity. Conventionally, the coiled tubing and perforating guns are removed from the well before subsequent fracturing stages are performed. Each fracturing stage may end with the development of a sand plug across the perforations by increasing the sand concentration and simultaneously reducing pumping rates until a bridge is formed. Increased sand plug integrity may be obtained by performing what is commonly known in the cementing services industry as a “hesitation squeeze” technique. A drawback of this technique, however, is that it requires multiple trips to carry out the various stimulation and isolation steps. 
         [0005]    The pressure required to continue propagation of a fracture present in a subterranean formation may be referred to as the “fracture propagation pressure.” Conventional perforating operations and subsequent fracturing operations undesirably may cause the pressure to which the subterranean formation is exposed to fall below the fracture propagation pressure for a period of time. In certain embodiments of conventional perforating and fracturing operations, the formation may be exposed to pressures that oscillate above and below the fracture propagation pressure. For example, if a hydrajetting operation is halted temporarily, e.g., in order to remove the hydrajetting tool, or to remove formation cuttings from the well bore before continuing to pump the fracturing fluid, then the formation may experience a pressure cycle. 
         [0006]    Pressure cycling may be problematic in sensitive formations. For example, certain subterranean formations may shatter upon exposure to pressure cycling during a fracturing operation, which may result in the creation of numerous undesirable microfractures, rather than one dominant fracture. Still further, certain conventional perforation operations (e.g., perforations performed using wireline tools) often may damage a sensitive formation, shattering it in the area of the perforation so as to reduce the likelihood that subsequent fracturing operations may succeed in establishing a single, dominant fracture. 
       SUMMARY 
       [0007]    The present invention relates generally to subterranean treatment operations, and more particularly to methods of isolating local areas of interest for subterranean treatment operations. 
         [0008]    In one embodiment, the present invention provides a bottomhole completion assembly comprising: a conduit adapted for installation in a well bore in a subterranean formation; one or more fluid jet forming nozzles disposed about the conduit; and one or more windows formed in the conduit and adapted to selectively allow a flow of a fluid through at least one of the one or more fluid jet forming nozzles. 
         [0009]    In another embodiment, the present invention provides a bottomhole completion assembly comprising: a conduit adapted for installation in a well bore in a subterranean formation; one or more fluid jet forming nozzles disposed about the conduit; a fluid delivery tool disposed within the conduit, wherein the fluid delivery tool is operable to move along the conduit; a straddle assembly operable to substantially isolate the fluid delivery tool from an annulus formed between the fluid delivery tool and the conduit; and wherein the conduit comprises one or more permeable liners. 
         [0010]    In another embodiment, the present invention provides a method of bottomhole completion in a subterranean formation comprising: providing a conduit adapted for installation in a well bore in a subterranean formation; providing one or more fluid jet forming nozzles disposed about the conduit; providing one or more windows adapted to selectively allow a flow of a fluid through the one or more fluid jet forming nozzles; and conducting a well completion operation. 
         [0011]    In another embodiment, the present invention provides a method of bottomhole completion in a subterranean formation comprising: providing a conduit adapted for installation in a well bore in a subterranean formation; providing one or more fluid jet forming nozzles disposed about the conduit; providing a fluid delivery tool disposed within the conduit, wherein the fluid delivery tool is operable to move along the conduit; providing a straddle assembly operable to substantially isolate the fluid delivery tool from an annulus formed between the fluid delivery tool and the conduit, wherein the conduit comprises one or more permeable liners; and conducting a well completion operation. 
         [0012]    The features and advantages of the present invention will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic cross-sectional view of an illustrative well completion assembly illustrating the perforation of a subterranean formation. 
           [0014]      FIGS. 2A and 2B  are schematic cross-sectional views showing an illustrative window casing assembly according to the present invention.  FIG. 2A  depicts the illustrative window casing in a closed position.  FIG. 2B  depicts the illustrative window casing in an open position. 
           [0015]      FIGS. 3A-3D  are schematic cross-sectional views illustrating various placements of fluid jet forming nozzles in the embodiment illustrated in  FIGS. 2A and 2B . 
           [0016]      FIGS. 4A and 4B  are schematic cross sectional views of an illustrative well completion assembly constructed in accordance with the embodiment depicted in  FIGS. 2A and 2B .  FIG. 4A  depicts the perforation and fracture of a subterranean formation.  FIG. 4B  depicts production from a subterranean formation. 
           [0017]      FIG. 5  is a schematic cross-sectional view of an illustrative well completion assembly according to one embodiment of the present invention. Inset  5 A shows an embodiment of the fluid jet forming nozzles described herein. 
           [0018]      FIGS. 5B and 5C  illustrate the use of the embodiment illustrated in  FIG. 5  in well completion operations.  FIG. 5B  depicts the perforation and fracture of a subterranean formation.  FIG. 5C  depicts production from a subterranean formation. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring now to  FIG. 1 , an illustrative completion assembly  100  includes a well bore  102  coupled to the surface  104  and extending down through a subterranean formation  106 . Well bore  102  may drilled into subterranean formation  106  using conventional (or future) drilling techniques and may extend substantially vertically away from surface  104  or may deviate at any angle from the surface  104 . In some instances, all or portions of well bore  102  may be vertical, deviated, horizontal, and/or curved. 
         [0020]    Conduit  108  may extend through at least a portion of well bore  102 . In some embodiments, conduit  108  may be part of a casing string coupled to the surface  104 . In some embodiments conduit  108  may be a liner that is coupled to a previous casing string. Conduit  108  may or may not be cemented to subterranean formation  106 . When uncemented, conduit  108  may contain one or more permeable liners, or it may be a solid liner. As used herein, the term “permeable liner” includes, but is not limited to, screens, slots and preperforations. Those of ordinary skill in the art, with the benefit of this disclosure, will recognize whether conduit  108  should be cemented or uncemented and whether conduit  108  should be contain one or more permeable liners. 
         [0021]    Conduit  108  includes one or more fluid jet forming nozzles  110 . As used herein, the term “fluid jet forming nozzle” refers to any fixture that may be coupled to an aperture so as to allow the communication of a fluid therethrough such that the fluid velocity exiting the jet is higher than the fluid velocity at the entrance of the jet. In some embodiments, fluid jet forming nozzles  110  may be longitudinally spaced along conduit  108  such that when conduit  108  is inserted into well bore  102 , fluid jet forming nozzles  110  will be adjacent to a local area of interest, e.g., zones  112  in subterranean formation  106 . As used herein, the term “zone” simply refers to a portion of the formation and does not imply a particular geological strata or composition. As will be recognized by those of ordinary skill in the art, with the benefit of this disclosure, conduit  108  may have any number of fluid jet forming nozzles, configured in a variety of combinations along and around conduit  108 . 
         [0022]    Once well bore  102  has been drilled and, if deemed necessary, cased, a fluid  114  may be pumped into conduit  108  and through fluid jet forming nozzles  110  to form fluid jets  116 . In one embodiment, fluid  114  is pumped through fluid jet forming nozzles  110  at a velocity sufficient for fluid jets  116  to form perforation tunnels  118 . In one embodiment, after perforation tunnels  118  are formed, fluid  114  is pumped into conduit  108  and through fluid jet forming nozzles  110  at a pressure sufficient to form cracks or fractures  120  along perforation tunnels  118 . 
         [0023]    As will be recognized by those of ordinary skill in the art, with the benefit of this disclosure, the composition of fluid  114  may be changed to enhance properties desirous for a given function, i.e., the composition of fluid  114  used during fracturing may be different than that used during perforating. In certain embodiments of the present invention, an acidizing fluid may be injected into formation  106  through conduit  108  after perforation tunnels  118  have been created, and shortly before (or during) the initiation of cracks or fractures  120 . The acidizing fluid may etch formation  106  along cracks or fractures  120 , thereby widening them. In certain embodiments, the acidizing fluid may dissolve fines, which further may facilitate flow into cracks or fractures  120 . In another embodiment of the present invention, a proppant may be included in fluid  114  being flowed into cracks or fractures  120 , which proppant may prevent subsequent closure of cracks or fractures  120 . 
         [0024]    For embodiments wherein conduit  108  is not cemented to subterranean formation  106 , annulus  122  may be used in conjunction with conduit  108  to pump fluid  114  into subterranean formation  106 . Annulus  122  may also be used to take returns of fluid  114  during the formation of perforation tunnels  118 . Annulus  122  may also be closed by any suitable means (e.g., by closing a valve, (not shown) at surface  104 ). Furthermore, those of ordinary skill in the art, with the benefit of this disclosure, will recognize whether annulus  122  should be closed. 
         [0025]    Referring now to  FIGS. 2A and 2B , an illustrative window casing assembly  200  is shown as adapted for use in the present invention. As used herein, the term “window casing” refers to a section of casing configured to enable selective access to one or more specified zones of an adjacent subterranean formation. As will be recognized by one of ordinary skill in the art, with the benefit of this disclosure, a window casing has a window that may be selectively opened and closed by an operator, for example, movable sleeve member  204 . As will be recognized by one of ordinary skill in the art, with the benefit of this disclosure, window casing assembly  200  can have numerous configurations and can employ a variety of mechanisms to selectively access one or more specified zones of an adjacent subterranean formation. Illustrative window casing  200  includes a substantially cylindrical outer casing  202  that receives a movable sleeve member  204 . Outer casing  202  includes one or more apertures  206  to allow the communication of a fluid from the interior of outer casing  202  into an adjacent subterranean formation (not shown). Apertures  206  are configured such that fluid jet forming nozzles  208  may be coupled thereto. In some embodiments, e.g. illustrative window casing assembly  200 , fluid jet forming nozzles  208  may be threadably inserted into apertures  206 . Fluid jet forming nozzles  208  may be isolated from the annulus  210  (formed between outer casing  202  and movable sleeve member  204 ) by coupling seals or pressure barriers  212  to outer casing  202 . 
         [0026]    Movable sleeve member  204  includes one or more apertures  214  configured such that, as shown in  FIG. 2A , apertures  214  may be selectively misaligned with apertures  206  so as to prevent the communication of a fluid from the interior of movable sleeve member  204  into an adjacent subterranean formation (not shown). Movable sleeve member  204  may be shifted axially, rotatably, or by a combination thereof such that, as shown in  FIG. 2B , apertures  214  selectively align with apertures  206  so as to allow the communication of a fluid from the interior of movable sleeve member  204  into an adjacent subterranean formation. Movable sleeve member  204  may be shifted via the use of a shifting tool, a hydraulic activated mechanism, or a ball drop mechanism. 
         [0027]    Referring now to  FIGS. 3A-3D , a window casing assembly adapted for use in the present invention, e.g., illustrative window casing assembly  200  depicted in  FIGS. 2A and 2B , may include fluid jet forming nozzles  300  in a variety of configurations.  FIG. 3A  shows fluid jet forming nozzles  300  coupled to apertures  302  via the interior surface  304  of outer casing  306 .  FIG. 3B  shows fluid jet forming nozzles  300  coupled to apertures  302  via the exterior surface  308  of outer casing  306 .  FIG. 3C  shows fluid jet forming nozzles  300  coupled to apertures  310  via the exterior surface  312  of movable sleeve member  314 .  FIG. 3D  shows fluid jet forming nozzles  300  coupled to apertures  310  via the interior surface  316  of movable sleeve member  314 . 
         [0028]    Referring now to  FIG. 4A , an illustrative well completion assembly  400  includes open window casing  402  and closed window casing  404  formed in conduit  406 . Alternatively, illustrative well completion assembly  400  may be selectively configured such that window casing  404  is open and window casing  402  is closed, such that window casings  402  and  404  are both open, or such that window casings  402  and  404  are both closed. 
         [0029]    A fluid  408  may be pumped down conduit  406  and be communicated through fluid jet forming nozzles  410  of open window casing  402  against the surface of well bore  412  in zone  414  of subterranean formation  416 . Fluid  408  would not be communicated through fluid jet forming nozzles  418  of closed window casing  404 , thereby isolating zone  420  of subterranean formation  416  from any well completion operations being conducted through open window casing  402  involving zone  414 . 
         [0030]    In one embodiment, fluid  408  is pumped through fluid jet forming nozzles  410  at a velocity sufficient for fluid jets  422  to form perforation tunnels  424 . In one embodiment, after perforation tunnels  424  are formed, fluid  408  is pumped into conduit  406  and through fluid jet forming nozzles  410  at a pressure sufficient to form cracks or fractures  426  along perforation tunnels  424 . 
         [0031]    In some embodiments, the fluid jet forming nozzles  410  may be formed of a composition selected to gradually deteriorate during the communication of fluid  408  from conduit  406  into subterranean formation  416 . As used herein, the term “deteriorate” includes any mechanism that causes fluid jet forming nozzles to erode, dissolve, diminish, or otherwise degrade. For example, fluid jet forming nozzles  410  may be composed of a material that will degrade during perforation, fracture, acidizing, or stimulation, thereby allowing production fluid  428 , shown in  FIG. 4B , to flow from subterranean formation  416 , through apertures  430 , and up conduit  406  to the surface  432 . By way of example, and not of limitation, some embodiments may utilize abrasive components in fluid  408  to cut the adjacent formation. In such embodiments, fluid jet forming nozzles  410  may be composed of soft materials such as common steel; such that the abrasive components of fluid  408  may erode fluid jet forming nozzles  410 . Some embodiments may incorporate an acid into fluid  408 . In such embodiments, fluid jet forming nozzles  410  may be composed of an acid soluble material such as aluminum. Other suitably acid prone materials may include ceramic materials, such as alumina, depending on the structure and/or binders of the ceramic materials. A person of ordinary skill in the art, with the benefit of this disclosure, will be aware of additional combinations of materials to form fluid jet forming nozzles  410  and compositions of fluid  408 , such that fluid jet forming nozzles  410  will deteriorate when subject to the communication of fluid  408  therethrough. Thus an operator may engage in stimulation and production activities with regard to zones  414  and  420  both selectively and jointly. 
         [0032]    Referring now to  FIG. 5 , an illustrative completion assembly  500  includes a well bore  502  coupled to the surface  504  and extending down through a subterranean formation  506 . Well bore  502  may be drilled into subterranean formation  506  using conventional (or future) drilling techniques and may extend substantially vertically away from surface  504  or may deviate at any angle from the surface  504 . In some instances, all or portions of well bore  502  may be vertical, deviated, horizontal, and/or curved. 
         [0033]    Conduit  508  may extend through at least a portion of well bore  502 . In some embodiments, conduit  508  may be part of a casing string coupled to the surface  504 . In some embodiments conduit  508  may be a liner that is coupled to a previous casing string. Conduit  508  may or may not be secured in well bore  502 . When secured, conduit  508  may be secured by casing packers  510 , or it may be cemented to subterranean formation  506 . When cemented, conduit  508  may be secured to subterranean formation  506  using an acid soluble cement. When uncemented, conduit  508  may be a solid liner or it may be a liner that includes one or more permeable liners  512 . Those of ordinary skill in the art, with the benefit of this disclosure, will recognize whether and how conduit  508  should be secured to well bore  502  and whether conduit  508  should include one or more permeable liners. 
         [0034]    Conduit  508  includes one or more fluid jet forming nozzles  514 . In some embodiments, fluid jet forming nozzles  514  may be longitudinally spaced along conduit  508  such that when conduit  508  is inserted into well bore  502 , fluid jet forming nozzles  514  will be adjacent to zones  516  and  518  in subterranean formation  506 . As will be recognized by those of ordinary skill in the art, with the benefit of this disclosure, conduit  508  may have any number of fluid jet forming nozzles, configured in a variety of combinations along and around conduit  508 . Optionally, fluid jet forming nozzles  514  may be coupled to check valves  520  (shown in Inset  5 A) so as to limit the flow of a fluid (not shown) through fluid jet forming nozzles  514  to a single direction. Optionally, conduit  508  may include one or more window casing assemblies, such as for example illustrative window casing assembly  200  (not shown), adapted so as to selectively allow the communication of a fluid through fluid jet forming nozzles  514 . 
         [0035]    Illustrative well completion assembly  500  may include a fluid delivery tool  522  disposed therein. Fluid delivery tool  522  may include injection hole  524  and may be connected to the surface  504  via workstring  526 . Fluid delivery tool  522  may be secured in conduit  508  with a straddle assembly  528 , such that injection hole  524  is isolated from the annulus  530  formed between conduit  508  and workstring  526 . Straddle assembly  528  generally should not prevent fluid delivery tool  520  from moving longitudinally in conduit  508 . 
         [0036]    Referring now to  FIG. 5B , illustrative well completion assembly  500  is configured to stimulate zone  516 . Fluid delivery tool  522  is aligned with fluid jet forming nozzles  514  such that a fluid  532  may be pumped down workstring coil  526 , through injection hole  524 , and through fluid jet forming nozzles  514  to form fluid jets  534 . Returns of fluid  532  may be taken through annulus  530 . In one embodiment, fluid  532  is pumped through fluid jet forming nozzles  514  at a velocity sufficient for fluid jets  534  to form perforation tunnels  536 . In one embodiment, after perforation tunnels  536  are formed, fluid  532  is pumped into conduit  508  and through fluid jet forming nozzles  514  at a pressure sufficient to form cracks or fractures  538  along perforation tunnels  536 . 
         [0037]    Optionally, once perforation tunnels  536  have been formed in zone  516 , annulus  530  may be closed by any suitable means (e.g., by closing a valve (not shown) through which returns taken through annulus  530  have been discharged at the surface). Closure of annulus  530  may increase the pressure in well bore  502 , and in subterranean formation  506 , and thereby assist in creating, and extending, cracks or fractures  538  in zone  516 . Closure of annulus  530  after the formation of perforation tunnels  536 , and continuation of flow exiting fluid jet forming nozzles  514 , also may ensure that the well bore pressure will not fall below the fracture closure pressure (e.g., the pressure necessary to maintain the cracks or fractures  538  within subterranean formation  506  in an open position). Generally, upon the initiation of the fracture, the pressure in well bore  502  may decrease briefly (which may signify that a fissure has formed in subterranean formation  506 ), but will not fall below the fracture propagation pressure. Among other things, flowing fluid through both annulus  530  and through fluid delivery tool  522  may provide the largest possible flow path for the fluid, thereby increasing the rate at which the fluid may be forced into subterranean formation  506 . 
         [0038]    In some embodiments, the fluid jet forming nozzles  514  may be formed of a composition selected to gradually deteriorate during the flow of fluid  532  from conduit  508  into subterranean formation  506 . For example, fluid jet forming nozzles  514  may be composed of a material that will degrade during perforation, fracture, acidizing, or stimulation, thereby allowing production fluid  540 , shown in  FIG. 5C , to flow from subterranean formation  506 , through apertures  542 , and up conduit  508  to the surface  504 . Production fluid  540  may also enter annulus  530  through permeable liner  512  and be returned to the surface  504 . 
         [0039]    Fluid delivery tool  522  may be moved longitudinally within conduit  508 , such that injection hole  524  aligns with fluid jet forming nozzles adjacent to zone  518  (not shown). Completion operations, including perforation, fracture, stimulation, and production, may thus be carried out in zone  518  in isolation from zone  516 . 
         [0040]    Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.