Abstract:
A multilateral injection/production/storage completion system. In a described embodiment, a method of completing a well having a first wellbore intersecting each of second, third and fourth wellbores includes the steps of: injecting a first fluid into a first zone intersected by the second wellbore; receiving a second fluid into the third wellbore in response to the first fluid injecting step; flowing the second fluid from the third wellbore to the fourth wellbore; storing the second fluid in a second zone intersected by the fourth wellbore; and then producing the second fluid from the second zone to a remote location.

Description:
BACKGROUND 
   The present invention relates generally to operations performed and equipment utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides multilateral well completion systems and methods. 
   A typical multilateral well includes multiple lateral or branch wellbores. The multiple branch wellbores could be used for variously injecting, transferring, storing and producing fluids in these wells. However, at present no satisfactory systems and methods are commercially available for accomplishing these functions conveniently, cost effectively and reliably in multilateral wells. 
   Furthermore, it is difficult if not impossible to change a typical multilateral completion system without pulling the system from the well. Thus, if well conditions change, for example, if it is desired to inject or store fluids in a zone which was formerly produced, typical multilateral completion systems must be pulled from the well and be reconfigured or replaced to conform to the new well conditions. 
   Therefore, it is well known by those skilled in the art that improved systems and methods are needed for multilateral well completions. Preferably, such improved multilateral well completion systems and methods should be adaptable to changing well conditions and configurable to suit a variety of situations. 
   SUMMARY 
   In carrying out the principles of the present invention, in accordance with an embodiment thereof, a well completion system is provided which includes the capability of performing a variety of functions with convenience and economy. Associated methods are also provided. 
   In one aspect of the invention, a system for completing a well having a first wellbore intersecting each of second, third and fourth wellbores is provided. The system includes a casing string positioned in the first wellbore. A first fluid is injected into the second wellbore. A second fluid is received into the third wellbore. The second fluid may be flowed into the third wellbore in response to the first fluid flowing into the second wellbore. 
   The second fluid is transferred from the third wellbore to the fourth wellbore for storage therein and later production. The transfer of the second fluid is accomplished by way of a passage in the first wellbore isolated from the casing string. 
   In another aspect of the invention, a method of completing a well having a first wellbore intersecting each of second, third and fourth wellbores is provided. The method includes the steps of: injecting a first fluid into a first zone intersected by the second wellbore; receiving a second fluid into the third wellbore in response to the first fluid injecting step; flowing the second fluid from the third wellbore to the fourth wellbore; storing the second fluid in a second zone intersected by the fourth wellbore; and then producing the second fluid from the second zone to a remote location. 
   In yet another aspect of the invention, another method of completing a well having a first wellbore intersecting each of second, third and fourth wellbores is provided. The method includes the steps of: interconnecting first, second and third apparatuses in a casing string, each of the apparatuses having a first passage forming a part of a longitudinal flow passage of the casing string, and a second passage intersecting the first passage; positioning the casing string in the first wellbore; injecting a first fluid through the first apparatus second passage into the second wellbore; receiving a second fluid from the third wellbore into the second apparatus second passage; flowing the second fluid from the second apparatus to the third apparatus; and storing the second fluid in a zone intersected by the fourth wellbore. 
   These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic cross-sectional view of a first system and method embodying principles of the present invention, shown in an injection/storage configuration; 
       FIG. 2  is a schematic cross-sectional view of the first system and method, shown in a production configuration; 
       FIG. 3  is a schematic cross-sectional view of the first system and method, shown in an alternate production configuration; 
       FIG. 4  is a schematic cross-sectional view of the first system and method, shown in a shut-in configuration; 
       FIG. 5  is an enlarged scale cross-sectional view of the first system and method, taken along line  5 — 5  of  FIG. 1 ; 
       FIG. 6  is a cross-sectional view of a first alternate mandrel and passage configuration; 
       FIG. 7  is a cross-sectional view of a second alternate mandrel and passage configuration; and 
       FIG. 8  is a schematic cross-sectional view of a second system and method embodying principles of the present invention. 
   

   DETAILED DESCRIPTION 
   Representatively illustrated in  FIG. 1  is a system  10  which embodies principles of the present invention. In the following description of the system  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used only for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. 
   The incorporated copending applications describe how an apparatus, such as the apparatus  12  depicted in  FIG. 1 , is interconnected in a casing string  14 , positioned in a parent or main wellbore, cemented in the parent wellbore, and is used to drill a branch wellbore  16 . In  FIG. 1 , three of the apparatuses  12 ,  18 ,  20  are used to drill three corresponding branch wellbores  16 ,  22 ,  24 . The parent wellbore is not shown in  FIG. 1  for illustrative clarity. 
   The incorporated copending applications also describe how fluid communication may be provided between apparatuses interconnected in a casing string using passages formed in the apparatuses and selectively isolated from an internal flow passage of the casing string. In the system  10 , the upper two apparatuses  12 ,  18  are in fluid communication via a passage  26  formed in each of the apparatuses. The passage  26  is visible in  FIG. 5 , which is a cross-sectional view of the upper apparatus  12 , taken along line  5 — 5  of FIG.  1 . The middle apparatus  18  has a similar cross-section in the system  10  as depicted in FIG.  1 . 
   Each of the apparatuses  12 ,  18 ,  20  has a passage  28  formed longitudinally therethrough which is a part of an internal longitudinal flow passage  30  of the casing string  14 . Each of the apparatuses  12 ,  18 ,  20  also has a passage  32  which intersects and extends laterally relative to the passage  28 . The branch wellbores  16 ,  22 ,  24  are drilled by deflecting cutting tools from the passage  28  through the passage  32  of the corresponding one of the apparatuses  12 ,  18 ,  20 . 
   The upper apparatus  12  includes a flow control device  34  which controls flow between the passage  32  and the passage  26 , and which also controls flow between the passages  32 ,  28  of the apparatus  12 . The flow control device  34  is depicted in  FIG. 1  as including a sliding sleeve  36 , however, any type of flow control device, such as a ball valve, a flapper-type valve, a choke, etc., may be used for the flow control device  34 . Although not illustrated in  FIG. 1 , the flow control device  34  preferably also includes an actuator remotely controllable via lines  38  (such as hydraulic, electric or fiber optic lines) extending to a remote location (such as the earth&#39;s surface or another location in the well). The flow control device  34  may also, or alternatively, be controlled by telemetry (such as electromagnetic, pressure pulse or acoustic telemetry). The flow control device  34  may include a control module to permit communication with the remote location, decode telemetry signals, etc. 
   The middle apparatus  18  also includes a flow control device  40  which is similar to the flow control device  34  described above. The flow control device  40  also controls flow between the passages  26 ,  32  and between the passages  28 ,  32  in the apparatus  18 . 
   The lower apparatus  20  also includes a flow control device  42  which is similar in many respects to the flow control devices  34 ,  40 . However, the lower apparatus  20  does not have the passage  26  formed therein, so the flow control device  42  only controls flow between the passages  28 ,  32  in the lower apparatus. 
   In each of the apparatuses  12 ,  18 ,  20 , a plug  44  is installed after the corresponding one of the branch wellbores  16 ,  22 ,  24  is drilled. The plug  44  prevents direct flow between the passages  28 ,  32  in each of the apparatuses  12 ,  18 ,  20 . 
   As depicted in  FIG. 1 , the system  10  is configured for an injection/storage operation in the well. The flow control device  34  is configured to permit flow between the passages  26 ,  32  and prevent flow between the passages  28 ,  32 . The flow control device  40  is configured to permit flow between the passages  26 ,  32  and prevent flow between the passages  28 ,  32 . The flow control device  42  is configured to permit flow between the passages  28 ,  32 . 
   Fluid (indicated by arrows  46 ), such as water or steam, is flowed down through the casing string  14  into the passage  28  of the lower apparatus  20 . The fluid  46  flows through the flow control device  42  and through the passage  32  into the branch wellbore  24 . The fluid  46  then flows outward into a formation or zone  48  intersected by the branch wellbore  24 . 
   This flow of the fluid  46  into the zone  48  causes or at least enhances the flow of another fluid (indicated by arrows  50 ), such as oil or gas, into the branch wellbore  22 . Preferably, the branch wellbore  22  intersects the same zone  48  as intersected by the branch wellbore  24 . It will be readily appreciated by one skilled in the art how flowing a relatively dense fluid, such as water, into a zone will force a relatively less dense fluid, such as oil or gas to rise in a zone. In this situation, the fluid  46  is injected into a lower portion of the zone  48 , and the hydrocarbon bearing fluid  50  is flowed out of an upper portion of the zone  48 . 
   However, it should be understood that these fluids and relative positions are not necessary in keeping with the principles of the invention. For example, a relatively less dense fluid, such as gas, could be injected into an upper portion of a zone, while a relatively more dense fluid, such as oil is flowed from a lower portion of a zone. 
   In this situation, the apparatuses  18 ,  20  could be in reversed positions as compared to the configuration shown in FIG.  1 . If the apparatus  20  is interconnected in the casing string  14  between the apparatuses  12 ,  18 , then the apparatus  20  could have a cross-section as depicted in FIG.  6 . This alternative cross-section provides the passage  26  through the apparatus  20  for fluid communication between the flow control devices  34 ,  40  of the apparatuses  12 ,  18 . 
   As another alternative, the apparatus  20  could be configured similar to the other apparatuses  12 ,  18 , wherein the flow control device  42  is also capable of controlling flow between the passages  26 ,  32 . Thus, it will be appreciated that many different configurations are possible, and the apparatuses  12 ,  18 ,  20  may have different relative positions, without departing from the principles of the invention. 
   The fluid  50  received into the branch wellbore  22  is flowed through the flow control device  40  and into the passage  26  in the middle apparatus  18 . The fluid  50  then flows from the passage  26 , through the flow control device  34  and into the passage  32  in the upper apparatus  12 . The fluid  50  then flows into the branch wellbore  16  and outward into a formation or zone  52  intersected by the branch wellbore  16 . The zone  52  may or may not be the same as the zone  48  into which the fluid  46  is injected. 
   If the fluid  50  is gas, or at least less dense than the fluid  46 , then the zone  52  could be an upper portion of the zone  48 . For gas or oil storage, the zone  52  could also be completely isolated from the zone  48 . Note that the injected fluid  46  could be gas, in which case the fluid  50  could be stored in the zone  52  which could be a lower portion of the zone  48 , in which case the apparatus  12  would be switched with the apparatus  20  in the casing string  14 . 
   Thus, as depicted in  FIG. 1 , the fluid  46  is injected into the zone  48  through the apparatus  20 , and in response the fluid  50  is received into the branch wellbore  22 . The fluid  50  flows through the passage  26  between the apparatuses  12 ,  18 . The fluid  50  then flows through the apparatus  12  and into the zone  52  for storage therein. 
   Referring additionally now to  FIG. 2 , the system  10  is depicted in a configuration in which the previously stored fluid  50  is produced from the zone  52  in which it was stored. In this configuration, the flow control device  34  in the upper apparatus  12  permits flow between the passages  28 ,  32  in the apparatus. The flow control device  40  in the middle apparatus  18  prevents flow between the passages  28 ,  32 , and prevents flow between the passages  26 ,  32 . The flow control device  42  in the lower apparatus  20  prevents flow between the passages  28 ,  32 . 
   The fluid  50  flows out of the zone  52  and into the branch wellbore  16 . The fluid  50  then flows into the passage  32 , through the flow control device  34  and into the passage  28 . The fluid  50  may then flow through the casing string passage  30  to a remote location, such as the earth&#39;s surface. 
   Referring additionally now to  FIG. 3 , the system  10  is depicted in a configuration in which the fluid  50  is produced from the branch wellbore  22  without being stored in the zone  52 . Instead, the fluid  50  flows into the passage  32 , through the flow control device  40  and into the passage  28  in the middle apparatus  18 . The fluid  50  may then be produced through the casing string passage  30  to the remote location. 
   In this configuration, the flow control device  40  permits flow between the passages  28 ,  32 , but prevents flow between the passages  26 ,  32 , in the middle apparatus  18 . The flow control device  34  prevents flow between the passages  26 ,  32  and between the passages  28 ,  32  in the upper apparatus  12 . The flow control device  42  prevents flow between the passages  28 ,  32  in the lower apparatus  20 . 
   Referring additionally now to  FIG. 4 , the system  10  is depicted in a configuration in which each of the three branch wellbores  16 ,  22 ,  24  is shut-in. The flow control device  34  prevents flow between the passages  26 ,  32  and between the passages  28 ,  32  in the upper apparatus  12 . The flow control device  40  prevents flow between the passages  28 ,  32  and between the passages  26 ,  32 , in the middle apparatus  18 . The flow control device  42  prevents flow between the passages  28 ,  32  in the lower apparatus  20 . 
   This configuration may be used, for example, when an emergency situation occurs. Each of the flow control devices  34 ,  40 ,  42  may perform the function of a safety valve to shut in the corresponding one of the branch wellbores  16 ,  22 ,  24 . The flow control devices  34 ,  40 ,  42  may respond to a signal transmitted from a remote location (e.g., via telemetry or via the lines  38 ), or they may respond to conditions sensed downhole, to close off flow therethrough. 
   It may now be fully appreciated how the system  10  provides enhanced functionality, convenience and versatility in multilateral completions. Although only three apparatuses  12 ,  18 ,  20  are illustrated in  FIGS. 1-4 , any number of apparatuses may be used in the system  10 , for example, another apparatus may be included in the casing string  14  for producing fluid from another zone intersected by the well, for injecting fluid into another zone, or for storing fluid in another zone. Additional apparatuses may be interconnected at virtually any desired position in the casing string  14 . 
   Note that it is not necessary for the system  10  to be configured as depicted in  FIGS. 1-4 . Any of the zones  48 ,  52  could be otherwise positioned, and otherwise positioned relative to the other zone(s). The apparatuses  12 ,  18 ,  20  could be otherwise positioned, and otherwise positioned relative to the other apparatuses. Any of the branch wellbores  16 ,  22 ,  24  could be an extension of the parent wellbore, and the branch wellbores are not necessarily drilled through the apparatuses  12 ,  18 ,  20 . 
   Referring additionally now to  FIG. 8 , another system  60  embodying principles of the invention is schematically and representatively illustrated. The system  6 o is similar in many respects to the system  10  described above. Elements which are similar to those previously described are indicated in  FIG. 8  using the same reference numbers. 
   The system  60  uses three apparatuses  62 ,  64 ,  66  interconnected in a casing string  14  and cemented within a parent wellbore  67 , as in the system  10 . The branch wellbores  16 ,  22 ,  24  are drilled through the passages  32  of the corresponding one of the apparatuses  62 ,  64 ,  66 . A plug  44  is installed after drilling to prevent direct flow between the passages  28 ,  32  in each of the apparatuses  62 ,  64 ,  66 . 
   However, in the system  60  the apparatuses  62 ,  64 ,  66  are identical to each other. Each of the apparatuses  62 ,  64 ,  66  has two passages  68 ,  70  formed therethrough and a flow control device  72  for controlling flow between the passage  32  and each of the passages  28 ,  68 ,  70 . That is, the flow control device  72  selectively permits and prevents flow between the passage  32  and each of the passages  28 ,  68 ,  70  in each of the apparatuses  62 ,  64 ,  66 . 
   A cross-sectional view of the apparatus  62  is depicted in  FIG. 7 , taken along line  7 — 7  of FIG.  8 . In this view the arrangement of the passages  28 ,  68 ,  70  may be clearly seen. The passages  68 ,  70  are depicted side-by-side in  FIG. 8  for clarity of illustration and description. 
   To control flow between the passages  28 ,  32 ,  68 ,  70 , the flow control device  72  is preferably of the type known to those skilled in the art as a “four way” valve. However, it should be understood that other numbers of flow control devices and other types of flow control devices could be used in keeping with the principles of the invention. For example, a separate valve could be used for controlling flow between the passage  32  and each one of the other passages  28 ,  68 , 70 . 
   The passages  68 ,  70  are provided in the apparatuses  62 ,  64 ,  66  in order to isolate injection and transfer flows from the casing string flow passage  30 . This configuration may be desired in situations in which fluid (indicated by arrows  74 ) is to be produced through the casing string flow passage  30  while fluid is being injected into one branch wellbore and fluid is being transferred between branch wellbores through the other passages  68 ,  70 . 
   A fluid (indicated by arrows  76 ), such as gas, may be injected from the passage  68 , through the flow control device  72  and into the passage  32  in the upper apparatus  62 . The fluid  76  would then flow into the branch wellbore  16  and outward into a formation or zone  78  intersected by the branch wellbore. The flow control device  72  in the upper apparatus  62  would permit flow between the passages  32 ,  68 , but prevent flow between the passages  32 ,  70  and between the passages  28 ,  32 . 
   Flow of the fluid  76  into the zone  78  would cause, or at least enhance, flow of another fluid (indicated by arrows  80 ), such as oil, into the branch wellbore  22 . The fluid  80  would then flow into the passage  32 , through the flow control device  72  and into the passage  70  in the middle apparatus  64 . The flow control device  72  would permit flow between the passages  32 ,  70 , but would prevent flow between the passages  28 ,  32  and between the passages  32 ,  68 . The fluid  80  would flow from the middle apparatus  64  to the lower apparatus  66  through the passage  70 . 
   In the lower apparatus  66 , the fluid  80  would flow from the passage  70 , through the flow control device  72  and into the passage  32 . The fluid  80  would then flow into the branch wellbore  24  and outward into a formation or zone  82  intersected by the branch wellbore. The flow control device  72  in the lower apparatus  66  could permit flow between the passages  32 ,  70 , but would prevent flow between the passages  28 ,  32  and between the passages  32 ,  68 . 
   The fluid  80  would be stored in the zone  82 . The zone  82  could be a lower portion of the zone  78 , or it could be completely isolated from the zone  78 . The fluid  80  could be produced from the zone  82  by actuating the flow control device  72  in the lower apparatus  66  to permit flow between the passages  28 ,  32 , but prevent flow between the passages  32 ,  68  and between the passages  32 ,  70 . 
   It will be readily appreciated that any number of the apparatuses  62 ,  64 ,  66  could be interconnected in the casing string  14  to inject fluid into, transfer fluid between, or produce fluid from any number of branch wellbores. For example, the fluid  74  could be produced through another apparatus interconnected below the lower apparatus  66 . Furthermore, the apparatuses  62 ,  64 ,  66  may have any relative position with respect to the other apparatuses, and the apparatuses may be similarly or differently configured. 
   Instead of injecting the fluid  76  through the casing string flow passage  30 , in the system  60  the fluid is received into the upper apparatus  62  from a tubular string  84  extending to a remote location. The passage  68  extends through the tubular string  84 . 
   The tubular string  84  is external to the casing string  14  in the parent wellbore  67  and is isolated from the casing string flow passage  30 . This permits injection of the fluid  76  while the fluid  74  is produced through the casing string flow passage  30 . 
   Another tubular string  86  could be connected to the upper apparatus  62 , if desired, to convey the fluid  80  to a remote location. In that case, the passage  70  would extend through the tubular string  86 , permitting the fluid  80  to flow through the tubular string  86  to the remote location, for example, for testing or for production separate from the fluid  74  produced through the casing string  14  in situations where commingling of the fluids  74 ,  80  is not desired, or is not permitted. 
   The system  60  demonstrates the wide range of multilateral well completions which may be accomplished using the principles of the invention. Fluid may be injected into any branch wellbore  16 ,  22 ,  24  by merely permitting flow between the passages  32 ,  68  in the associated one of the apparatuses  62 ,  64 ,  66 . Fluid may be transferred between any of the apparatuses  62 ,  64 ,  66  by merely permitting flow between the passages  32 ,  70  in each of the apparatuses. Fluid may be produced from any of the branch wellbores  16 ,  22 ,  24  by merely permitting flow between the passages  28 ,  32  in the associated one of the apparatuses  62 ,  64 ,  66 . 
   Fluid may be injected into multiple branch wellbores, transferred between more than two branch wellbores, stored in multiple branch wellbores, and produced from multiple branch wellbores simultaneously. Additional apparatuses may be interconnected in the casing string  14  to permit these operations to be performed in additional branch wellbores. 
   Since each apparatus has injection, fluid transfer and production capabilities (due to the passages  28 ,  68 ,  70  being formed in each apparatus), any of these operations may be performed in any of the apparatuses at any time. For example, the upper branch wellbore  16  could have produced oil when the well was initially completed. Later, after much of the oil is depleted from the upper portion of the zone  78 , the branch wellbore  16  may be used to inject gas into the zone to enhance oil recovery from the lower portion of the zone via the branch wellbore  22 . The gas injected into the zone  78  could be separated from the fluid  80  produced from the zone  78 , or from another zone. 
   Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are contemplated by the principles of the present invention. For example, in either of the systems  10 ,  60 , any of the branch wellbores  16 ,  22 ,  24  could be an extension or another portion of the parent wellbore  67 , the plug  44  could be replaced by packers straddling the passage  32  in the passage  28 , it is not necessary for the branch wellbores  16 ,  22 ,  24  to be drilled through the apparatuses, etc. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.