Abstract:
A completion assembly for use in a lateral well bore has a base pipe with a plurality of holes through the sidewall of the base pipe. Flow through the holes is regulated to produce an influx difference between the ends of the base pipe. Flow can be regulated by variably spacing or sizing the holes. Flow can also be regulated by selectively inserting a rod between adjacent splines located on the base pipe to cover and block the flow through certain holes in the base pipe. Flow can also be regulated using a rotatable sleeve adjacent to the base pipe such that rotation of the sleeve brings the holes and openings in the pipe and sleeve, respectively, into and out of alignment. A filter can be used to filter sand and other particulates. An erosion inhibitor can be used to extend the useful life of the assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/263,369, filed Jan. 23, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Invention  
           [0003]    This invention relates generally to flow control in downhole completions. Specifically, this invention relates to the control of flow along the length of a horizontal downhole completion.  
           [0004]    2. Related Art  
           [0005]    Within the oil and gas industry, it is now fairly common to include lateral well bores that extend at an angle from a main vertical well bore. In some cases, the lateral well bores extend in a substantially horizontal direction from the main well bore.  
           [0006]    A completion is typically deployed within such lateral well bores. The completion may include sliding sleeves, packers, and sand control equipment. Essentially, hydrocarbons flow from the formation intersected by the lateral well bore, into the lateral well bore, into the completion, and to the surface through the completion and associated tubing string.  
           [0007]    However, in lateral well bores, specially those extending in a substantially horizontal direction, the flow rate into the completion is not equal along the length of the completion. Instead, due to the flow friction along the length of the completion, a higher flow rate tends to exist at the near end or “heel” of the lateral completion, and a lower flow rate tends to exist at the far end or “toe” of the lateral completion. The disparity in flow rate from the “toe” to the “heel” of the lateral completion, in turn, may lead to premature gas or water coning at the area of higher flow rate and/or may also decrease the total amount of hydrocarbons extracted from the relevant formation.  
           [0008]    The prior art would therefore benefit from a system and method for equalizing the flow rate along a lateral completion.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention uses an innovative design for a completion assembly for use in a lateral well bore having a base pipe with a plurality of holes through the sidewall of the base pipe. Flow through the holes is regulated to produce an influx difference between the ends of the base pipe. Flow can be regulated by variably spacing or sizing the holes. Flow can also be regulated by selectively inserting a rod between adjacent splines located on the base pipe to cover and block the flow through certain holes in the base pipe. Flow can also be regulated using a rotatable sleeve circumferentially adjacent to the base pipe such that rotation of the sleeve brings the holes and openings in the pipe and sleeve, respectively, into and out of alignment. A filter can be used to filter sand and other particulates. An erosion inhibitor can be used to extend the useful life of the assembly. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an elevation view of a lateral well bore extending from a main well bore, with a completion deployed therein, and generally utilizing the invention.  
         [0011]    [0011]FIG. 2 is a partial cross-sectional view of a completion section that illustrates the first embodiment of this invention.  
         [0012]    [0012]FIG. 3 is a partial cross-sectional view of another completion section that illustrates the first embodiment of this invention.  
         [0013]    [0013]FIG. 4 is a partial cross-sectional view of another completion section that illustrates the first embodiment of this invention.  
         [0014]    [0014]FIG. 5 is a partial cross-sectional view of another completion section that illustrates the first embodiment of this invention.  
         [0015]    [0015]FIG. 6 is a partial cut-away view of a completion section that illustrates the second embodiment of this invention.  
         [0016]    [0016]FIG. 7 is a more detailed partial cut-away view of a completion section that illustrates the second embodiment of this invention.  
         [0017]    [0017]FIG. 8 is a partial cut-away view of a completion section that illustrates the third embodiment of this invention.  
         [0018]    [0018]FIG. 9 is a cross-sectional view of a completion section that illustrates the third embodiment of this invention.  
         [0019]    [0019]FIG. 10 is a more detailed cross-sectional view of one end of the completion section that illustrates the third embodiment of this invention.  
         [0020]    [0020]FIG. 11 is an isometric, cut-away view of an insert that can be included in the holes that extend through the completion sections of this invention.  
         [0021]    [0021]FIG. 12 is an isometric, cut-away view of a completion section including one embodiment of an erosion barrier.  
         [0022]    [0022]FIG. 13 is a cross-sectional view of a completion section including another embodiment of an erosion barrier.  
     
    
     DETAILED DESCRIPTION  
       [0023]    [0023]FIG. 1 generally illustrates a main well bore  10  extending from the surface  12  downwardly. A lateral well bore  14  extends from the main well bore  10  and intersects a hydrocarbon formation  16 . A completion  18  extends within the lateral well bore  14  and includes a “toe”  24  at the far end of the completion  18  and a “heel”  22  at the near end of the completion  18 . The completion  18  is connected to, for instance, tubing string  20  that extends within the main well bore  10  to the surface  12 .  
         [0024]    As previously discussed, without incorporating additional elements, due to the flow friction along the length of the completion  18 , the flow rate into the lateral completion  18  at the heel  22  of the completion  18  is greater than the flow rate at the toe  24  of the completion  18 . This invention evenly distributes the flow rate into the completion  18  by controlling the pressure drop into the completion  18  along the length of the lateral completion  18 . This is achieved by varying the effective area of fluid communication between the completion  18  and the formation  16  (hereinafter referred to as the “Effective Area of Fluid Communication”) along the length of the completion  18 . In principle and all variables being equal, a completion section with a larger Effective Area of Fluid Communication will have a higher flow rate than a completion section with a smaller Effective Area of Fluid Communication. It is noted that a decrease in the Effective Area of Fluid Communication for a completion section results in an increase in pressure drop across such completion section, and vice-versa.  
         [0025]    Essentially, the completion  18  is divided into sections  26 ( a - g ) from the heel  22  to the toe  24 , and the sections  26  are constructed so that the Effective Area of Fluid Communication for each section  26  increases from the section  26   a  closest to the heel  22  to the section  26   g  closest to the toe  24 . Once calculated correctly, an increase of the Effective Area of Fluid Communication from the heel  22  to the toe  24  offsets (compensates for) the disparity in flow rate previously discussed, thereby evenly distributing the flow rate along the length of the completion  18 . In one embodiment, such increase is a gradual increase. Three embodiments for the present invention are set forth herein.  
       First Embodiment  
       [0026]    FIGS.  2 - 5  show the first embodiment of the invention. In this embodiment, each section  26  includes a base pipe  28  that has holes  30  extending therethrough. Each section  26  may also include a filter  32 , such as a sand screen  34 . Sections  26  may be coupled to each other by threaded couplings  36 , for example. Hydrocarbon from the formation  16  typically flows from the formation  16 , into the lateral well bore  14  (through perforations if included), through the filter  32  (if included), into the annular region  29  formed between the filter  32  and the base pipe  28 , through the holes  30 , into the central bore  31  of the lateral completion  18 , and up to the surface  12  through the tubing string  20 .  
         [0027]    This embodiment comprises varying the number and/or size of the holes  30  for each section  26  so that an increase (a gradual increase in one embodiment) in the Effective Area of Fluid Communication (through the holes  30 ) can be achieved from the heel  22  to the toe  24  of the completion  18 . Thus, the aggregate hole  30  area for each section  26  increases from the heel  22  to the toe  24  of the completion  18 .  
         [0028]    [0028]FIG. 2 shows a section  26  with a certain number of holes  30 . FIGS.  3 - 5 , comparatively, include sections  26  with a lesser number of holes  30  than shown in FIG.  2 . Between FIGS.  3 - 5 , it is noted that the size of the holes  30  of FIG. 3 are smaller than the size of the holes  30  of FIG. 4 and that the size of the holes of FIG. 5 increases from left to right.  
         [0029]    The sections  26  shown in FIGS.  2 - 5  can be arranged in a variety of ways to achieve the objective of providing a gradual increase in the Effective Area of Fluid Communication from heel  22  to the toe  24  of completion  18 . For instance, the sections  26  can be arranged so that section  26   a  has less holes  30  than section  26   g  and so that the number of holes  30  for each adjacent section  26 ( a - g ) increases from section  26   a  to section  26   g.  Or, the sections  26  can be arranged so that the holes  30  of section  26   a  are smaller than the holes  30  of section  26   g  and so that the size of the holes  30  for each adjacent section  26 ( a - g ) increases from section  26   a  to section  26   g.  Or, several sections  26  as shown in FIG. 5 may be used, wherein the sizes of the holes  30  not only increase from heel  22  to toe  24  from section  26  to section  26 , but also increase within each section  26 . The sections  26  can also be arranged so that the number as well as the size of the holes  30  increase from heel  22  to toe  24 .  
       Second Embodiment  
       [0030]    A second embodiment of the invention is shown in FIGS. 6 and 7, which for purposes of clarity are cut away views and do not show the entire section  26 . In this embodiment, each section  26  also includes a base pipe  28  that has holes  30  extending therethrough. Each section  26  may also include a filter  32 , such as a sand screen  34 . Sections  26  may be coupled to each other by threaded couplings  36 , for example. As is known in the art, a plurality of splines  38  typically provide support between the sand screen  34  and the base pipe  28 . The splines  38  normally extend longitudinally along the length of the base pipe  28  and are spaced apart about the circumference of the base pipe  28 . The holes  30  provide fluid communication from the area between the splines  38  to the central bore  31  of the base pipe  28 . Thus, hydrocarbon from the formation  16  typically flows from the formation  16 , into the lateral well bore  14  (through perforations if included), through the filter  32  (if included), into the annular region  29  formed between the filter  32  and the base pipe  28 , through the holes  30 , into the central bore  31  of the lateral completion  18 , and up to the surface  12  through the tubing string  20 .  
         [0031]    In this embodiment, however, the number of holes  30  that provide such fluid communication can be modified by inserting a bar  40  between adjacent splines  38  so that such bar  40  covers the holes  30  located between such adjacent splines  38 . Thus, the insertion of a bar  40  changes the number of holes  30  that provide fluid communication (thus changing the Effective Area of Fluid Communication through such section  26 ), thereby enabling an operator to change the pressure drop (and therefore flow rate) across each section  26 . Of course, more than one bar  40  can be inserted in each section  26 , each being inserted between different pairs of adjacent splines  38 .  
         [0032]    The bars  40  can be machined to a close tolerance to snugly fit between adjacent splines  38 . Bars  40  can also be different lengths, thereby covering different numbers of holes  30 . Bars  40  are constructed so that flow through a rod-covered hole  30  is severely restricted or altogether blocked.  
         [0033]    The bars  40  can be inserted between the splines  38  either at the assembly facility or at the rig floor. To allow for simple insertion and removal at either site, each section  26  includes at least one end cap  42  that is easily selectively removed from the remainder of the section  26  thereby allowing access to the bars  40  and splines  38 . Such end caps  42  may be attached to the base pipe  28  by mechanisms such as threading or clamping.  
         [0034]    In use, bars  40  can be selectively inserted between adjacent splines  38  of the sections  26 ( a - g ) so that the Effective Area of Fluid Communication (the aggregate hole  30  area) for each section  26  is controlled by the operator. In this manner, an operator can arrange the sections  26 ( a - g ) to achieve the objective of providing an increase (a gradual increase in one embodiment) in the Effective Area of Fluid Communication from the heel  22  to the toe  24  of completion  18 . For instance, given the same pattern, number, and size of holes  30  for each section  26 , a decrease in the number of bars  40  used from section  26   a  to section  26   g  results in an increase in the Effective Area of Fluid Communication from the heel  22  to the toe  24  of completion  18 .  
         [0035]    It is noted that the bars  40  are not restricted to be used with only wire wrapped sand control screens. Their use can also be implemented with any screen that has an annular space between the base pipe and filter (screen).  
       Third Embodiment  
       [0036]    A third embodiment of the invention is shown in FIGS.  8 - 10 , which for purposes of clarity are cut-away and cross-sectional views and do not show the entire section  26 . In this embodiment, each section  26  also includes a base pipe  28  that has holes  30  extending therethrough. Each section  26  may also include a filter  32 , such as a sand screen  34 . Sections  26  may be coupled to each other by threaded couplings  36 , for example. As is known in the art, a plurality of splines  38  typically provide support between the sand screen  34  and the base pipe  28 . The splines  38  normally extend longitudinally along the length of the base pipe  28  and are spaced apart about the circumference of the base pipe  28 . The holes  30  provide fluid communication from the area between the splines  38  to the central bore  31  of the base pipe  28 . Thus, hydrocarbon from the formation  16  typically flows from the formation  16 , into the lateral well bore  14  (through perforations if included), through the filter  32  (if included), into the annular region  29  formed between the filter  32  and the base pipe  28 , through the holes  30 , into the central bore  31  of the lateral completion  18 , and up to the surface  12  through the tubing string  20 .  
         [0037]    In this embodiment, however, the number and/or area of holes  30  that provide such fluid communication can be modified by rotation of a sleeve  44 . The sleeve  44  can be located internally of the base pipe  28 . The sleeve  44  includes openings  48  therethrough (which may be in the form of slots  46 —see FIG. 8) that, depending on the position of the sleeve  44 , line up with the holes  30  of the base pipe  28 . The sleeve  44  can be rotated so that alignment of the openings  48  and the holes  30  can be varied, thereby modifying the Effective Area of Fluid Communication through each section  26 .  
         [0038]    To enable the rotational movement of the sleeve  44  within the base pipe  28 , the outer surface  50  of the sleeve  44  is rotatably connected to the inner surface  52  of the base pipe  28 . In one embodiment as shown in FIG. 10, the sleeve  44  is rotatably connected to the base pipe  28  by way of mating threads  54 . Mating threads  54  can be included on one end of the sleeve  44  (as shown in FIG. 10), on both ends of sleeve  44 , or along a large portion or the entirety of the outer surface  50  of sleeve  44 . In another embodiment as shown in FIG. 9, the sleeve  44  may be slip-fitted within the base pipe  28  to allow their relative rotation. In this embodiment, axial movement of the sleeve  44  may be prevented by stops  400  protruding from the inner surface  52  of the base pipe  28 . As shown in FIG. 9 on one of the ends of section  26 , the stops  400  may comprise a threaded connector  401  used to connect two sections  26  together.  
         [0039]    The sleeve  44  includes a selective locking mechanism  56  that enables the sleeve  44  to be locked (not rotatable) at different positions, each position allowing a different Effective Area of Fluid Communication through each section  26  (as previously discussed). The locking mechanism  56  can comprise, for example, set screws  402  threaded through set screw holes  403  of the base pipe  28  against the sleeve  44  to thereby prevent rotation of the sleeve  44 . In another embodiment (not shown), the locking mechanism  56  can comprise an indexing ratchet mechanism.  
         [0040]    The sleeve  44  can be rotated between positions at the assembly facility or at the rig floor. Once the section  26  is assembled, rotation of the sleeve  44  can be accomplished by the insertion of another tool  58  into the central bore  31 . The tool  58  extends to the exterior of the section  26  so that the tool  58  can be easily manipulated by an operator. The tool  58  is selectively attached to the inner surface  60  of the sleeve  44 , such as by mating threads or a mating profile (not shown). Once attached to the sleeve  44 , the tool  58  is rotated by the operator to achieve the desired position between the openings  48  and the holes  30 .  
         [0041]    In use, the sleeves  44  can be rotated within the base pipes  28  of sections  26 ( a - g ) so that the Effective Area of Fluid Communication (the aggregate hole  30  area) for each section  26  is controlled by the operator. In this manner, an operator can arrange the sections  26 ( a - g ) to achieve the objective of providing an increase (a gradual increase in one embodiment) of the Effective Area of Fluid Communication from the heel  22  to the toe  24  of completion  18 . For instance, the sleeve  44  of each section  26  can be positioned so that the Effective Area of Fluid Communication for the sections  26  ( a - g ) increases from the heel  22  (section  26   a ) to the toe  24  (section  26   g ) of completion  18 .  
       Combination of Embodiments  
       [0042]    It is noted that the three embodiments previously described may be combined in the same completion  18 . For instance, in the same section  26 , the holes  30  can be varied in size and/or number (first embodiment) in combination with the use of the bars  40  (second embodiment) or the sleeve  44  (third embodiment). In addition, each section  26 ( a - g ) may also comprise a different one of the of the three embodiments so that, for instance, the first embodiment is used in section  26   a,  the second embodiment is used in section  26   b,  and the third embodiment is used in section  26   c.    
       Additional Optional Elements  
       [0043]    FIGS.  11 - 13  show different embodiments of erosion inhibitors  200  that may be used with any of the embodiments previously described. It is noted that increasing the pressure differential across the base pipe holes  30  (by decreasing the Effective Area of Fluid Communication) leads to increased fluid velocity through the remaining holes  30 . In turn, an increase in fluid velocity through base pipe holes  30  has been shown to erode the walls of the holes  30 , which is of course undesirable. Moreover, an increase in fluid velocity may also erode the filter  32  or screen  34  through which such fluid is passing.  
         [0044]    Turning to FIG. 11, to prevent such erosion on the walls of the holes  30 , the erosion inhibitor  200  can comprise a hardened insert  50  that can be inserted in each hole  30 . The insert  50  can be made of carbide, for example, or any other sufficiently hard and long-lived material. Each insert  50  is generally disc shaped to enable the fluid communication of hydrocarbons therethrough and is secured within its relevant hole  30  by means known in the art, such as welding, brazing, gluing, threading, or mechanical interference fit.  
         [0045]    It is noted that the insert  50  shown in FIG. 11 includes a shoulder portion  52 . Instead of shoulder portion  52 , some inserts  50  may be flush with the base pipe  28  inner and outer surfaces.  
         [0046]    [0046]FIG. 12 illustrates an erosion inhibitor  200  that helps to prevent erosion of the filter  32  (screen  34 ) and the walls of the holes  30 . The erosion inhibitor  200  comprises a shield  202  attached to the exterior of the filter  32 , such as by latching or welding. In one embodiment, the shield  202  surrounds the holes  30 . The shield  202  prevents the fluid from flowing directly across the filter  32  and though the holes  30  (see dashed flow path  204 ), which can lead to erosion of either/both due to the high velocity of the fluid. Instead, the fluid must flow around the shield  202 , through the filter  32 , and through the holes  30  (see flow path  206 ). The path taken by the fluid around the shield  202  lowers the velocity of the fluid and thus aids in preventing erosion. Of course, more than one shield  202  can be included on each completion section  26 .  
         [0047]    [0047]FIG. 13 illustrates another embodiment of an erosion inhibitor  200  that helps to prevent erosion of the filter  32  (screen  34 ) and the walls of the holes  30 . The erosion inhibitor  200  can comprise a specially designed screen  300  that includes a non-permeable screen section  210  and normal screen sections  212 . In one embodiment, non-permeable screen section  210  surrounds the holes  30 . Non-permeable section  210  does not include gaps and therefore prevents fluid from flowing therethrough. Normal sections  212  include the typical gaps  208  in such filters which allow fluid flow therethrough. The screen  300  (non-permeable section  210 ) prevents the fluid from flowing directly across the filter  32  and though the holes  30  (see dashed flow path  214 ), which can lead to erosion of either/both due to the high velocity of the fluid. Instead, the fluid must flow around the non-permeable section  210 , through the gaps  208  of the normal sections  212 , and through the holes  30  (see flow path  216 ). The path taken by the fluid around the non-permeable section  210  lowers the velocity of the fluid and thus aids in preventing erosion. Of course, more than one non-permeable section  210  can be included on each completion section  26   
         [0048]    It is noted that the different embodiments of the erosion inhibitor  200  can be combined. Thus, inserts  50  can be used on the same section  26  (or completion  18 ) as the shield  202  or special screen  300 . Moreover, the shield  202  and the special screen  300  can be used on the same section  26  (or completion  18 ).  
         [0049]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.