Abstract:
A field development system and associated methods provide for cost effective development of a field by minimizing the number of required production facilities and preventing damage to wellbores due to drilling lateral wellbores therefrom. In a described embodiment, a field development system includes a main wellbore intersecting a formation and having fractures extending outwardly into the formation. Multiple additional wellbores intersect the fractures to thereby improve drainage of the formation without the need of drilling lateral wellbores from the main wellbore and without the need of providing additional production facilities for the additional wellbores.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit of the filing date of U.S. provisional application serial no. 60/189,172, filed Mar. 14, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to production of, and injection into, subterranean wells and, in an embodiment described herein, more particularly provides a field development system and methods associated therewith.  
           [0003]    To improve drainage of a formation, it has become quite common to drill one or more lateral wellbores extending outwardly from a parent wellbore and into the formation. An alternative is to drill numerous wellbores into the formation, but this generally requires additional production facilities for the additional wells. Such production facilities are very costly, so the choice is typically made to drill lateral wellbores where conditions warrant.  
           [0004]    However, drilling lateral wellbores has its disadvantages as well. For example, a large amount of casing wear is usually experienced in drilling lateral wellbores. As another example, forming a pressure tight junction between the parent and lateral wellbores is a problem.  
           [0005]    From the foregoing, it can be seen that it would be quite desirable to provide a field development system which enhances the drainage of a formation without requiring the drilling of lateral wellbores from a main producing wellbore, and without requiring numerous production facilities for numerous wellbores.  
         SUMMARY OF THE INVENTION  
         [0006]    In carrying out the principles of the present invention, in accordance with an embodiment thereof, a field development system is provided in which a main producing wellbore is placed in fluid communication with one or more additional wellbores extending within a formation. Associated methods are also provided.  
           [0007]    In broad terms, a method is provided which includes the steps of drilling a second wellbore to intersect a fracture extending outward from a first wellbore and flowing fluid between the first and second wellbores through the fracture. Both the first and second wellbores may intersect a formation into which the fracture extends, in which case the second wellbore effectively extends the drainage of the formation by the first wellbore, without the need of drilling a lateral wellbore from the first wellbore. Alternatively, the second wellbore may intersect a formation which is not intersected by the first wellbore, in which case the second wellbore provides a conduit by which the formation may be drained by the first wellbore.  
           [0008]    The second wellbore may be equipped with a fluid property sensor, which may be in communication with a receiver in the first wellbore for transmission of fluid property indications to the surface. The sensor may be utilized to detect when water enters the second wellbore. Several of the second wellbores with sensors therein may be arranged in an array about the first wellbore, in which case an advancing sweep of water may be detected in two or more dimensions.  
           [0009]    The advantages of the present invention may also be used in water flood or steam injection applications. For example, an injection well may be placed in fluid communication with additional wellbores drilled in a formation via fractures which extend outward from the injection well and intersect the additional wellbores.  
           [0010]    In another aspect of the present invention, drainage wellbores which are drilled to intersect fractures extending outward from a main wellbore are plugged between the formation and the earth&#39;s surface. Thus, no additional production facilities are utilized to produce fluids from the drainage wellbores.  
           [0011]    In yet another aspect of the present invention, the drainage wellbores may be drilled as lateral wellbores extending outward from a parent wellbore. The drainage wellbores may be drilled in more than one formation also intersected by the main production wellbore. Alternatively, the main production wellbore may not intersect one or more of the formations in which the drainage wellbores are drilled.  
           [0012]    In still another aspect of the present invention, flow between a drainage wellbore and the main production wellbore may be prevented by releasing a flow blocking substance in the drainage wellbore. This may be useful, for example, to prevent water encroachment from the drainage wellbore to the main production wellbore. The flow blocking substance may be released by flowing a particular fluid, such as acid, from the main production wellbore into the drainage wellbore via a fracture.  
           [0013]    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  
       [0014]    [0014]FIG. 1 is a schematic partially cross-sectional view of a first method and system embodying principles of the present invention;  
         [0015]    [0015]FIG. 2 is an enlarged scale cross-sectional view of a flow blocking apparatus usable in the first method and system of FIG. 1;  
         [0016]    [0016]FIG. 3 is a top plan view of the first method and system of FIG. 1 showing an alternate configuration thereof;  
         [0017]    [0017]FIG. 4 is a schematic cross-sectional view of a second method and system embodying principles of the present invention;  
         [0018]    [0018]FIG. 5 is a schematic partially cross-sectional view of a third method and system embodying principles of the present invention; and  
         [0019]    [0019]FIG. 6 is a schematic partially cross-sectional view of a fourth method and system embodying principles of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Representatively illustrated in FIG. 1 is a method  10  which embodies principles of the present invention. In the following description of the method  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used 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., without departing from the principles of the present invention.  
         [0021]    In the method  10 , a main production wellbore  12  is drilled so that it intersects one or more earth formations  14 ,  16  from which it is desired to produce fluids to the earth&#39;s surface. As used herein, the term “formation” is used to describe a formation or zone, or a portion thereof. Thus, the formations  14 ,  16  depicted in FIG. 1 may be different zones of a single formation, separate formations, etc. Of course, it is not necessary in the method  10  for the wellbore  12  to intersect more than one formation. Note that the wellbore  12  and other wellbores described herein may be cased or uncased, without departing from the principles of the present invention.  
         [0022]    Fractures  18 ,  20  are formed extending outward from the wellbore  12  into the formation  14 , and fractures  22 ,  24  are formed extending outward from the wellbore into the formation  16 . A tubular string  26 , which includes production valves  28 ,  30  and packers  32 ,  34 , is installed in the wellbore  12  to control production from the formations  14 ,  16  and to provide a conduit for such production.  
         [0023]    To enhance drainage of fluids from the formation  14 , another wellbore  36  is drilled into the formation so that it intersects the fracture  20 . Thus, fluids from the formation  14  can flow into the wellbore  36 , which may extend hundreds or thousands of feet in the formation, and through the fracture  20  into the main wellbore  12 . The wellbore  36  preferably intersects the fracture  20  at an acute angle, or an angle other than ninety degrees, to maximize the area of intersection between the wellbore  36  and the fracture  20 .  
         [0024]    A filtering device, such as a slotted liner  38 , may be positioned within the wellbore  36  to filter the fluid flowing from the formation  14  into the wellbore. A plug  40  prevents flow of the fluids from the formation  14  upwardly through the wellbore  36  above the formation. Note that fluids produced from the formation  14  are flowed into the wellbore  36 , but are produced through the main wellbore  12 .  
         [0025]    The wellbore  36  is shown as being a single wellbore drilled into the formation  14 . However, FIG. 1 also depicts a method in which multiple wellbores may be drilled into multiple formations intersected by the main wellbore  12  and placed in fluid communication therewith. A parent wellbore  42  is drilled and then lateral or branch wellbores  44 ,  46  are drilled extending outward from the parent wellbore. The wellbore  44  is drilled into the formation  14  so that it intersects the fracture  18 , and the wellbore  46  is drilled into the formation  16  so that it intersects the fracture  22 . Preferably, the wellbores  44 ,  46  intersect the fractures  18 ,  22 , respectively, at angles other than ninety degrees to enhance the area of intersection therebetween.  
         [0026]    Fluid filtering devices, such as well screen  48  and slotted liner  50 , may be used to filter the fluids flowing from the formations  14 ,  16  into the wellbores  44 ,  46 , respectively. Plugs  52 ,  54  prevent upward flow of the fluids in the wellbores  44 ,  46 , respectively, produced from the formations  14 ,  16 .  
         [0027]    A fluid property sensor  56 , such as a pressure, temperature, resistivity, density, flow rate and/or other type of sensor, may be positioned in the wellbore  36  (and/or in any of the other drainage wellbores  44 ,  46 ). The sensor  56  may transmit fluid property indications to a receiver and/or transmitter  58  in the main wellbore  12 . For example, the receiver  58  may receive and store the fluid property indications transmitted from the sensor/transmitter  56  for later retrieval by a conventional tool such as a wet connect conveyed on wireline or coiled tubing, or the receiver  58  may transmit the fluid property indications to the earth&#39;s surface or another remote location via electromagnetic waves, acoustic waves, pressure pulses, or other means. In this manner, an operator may be able to identify the specific fluids entering the wellbore  36  from the formation  14  and/or the rate at which the fluids are flowing.  
         [0028]    Eventually, it may be desired to prevent fluid flow between the wellbores  12 ,  36 . For example, the wellbore  36  may begin producing water. To prevent fluid flow in the wellbore  36 , a flow blocking apparatus  60  is positioned therein. The flow blocking apparatus  60  is shown representatively and schematically in an enlarged cross-sectional view in FIG. 2, but it is to be clearly understood that other types of flow blocking apparatus may be used in the method  10 , without departing from the principles of the present invention.  
         [0029]    The apparatus  60  includes a generally tubular outer housing  62  and a generally tubular perforated inner sleeve  64 . A flow blocking substance  66 , such as fines, coagulant, clay, resin, etc., in one or more capsules or other enclosures  68  is contained between the housing  62  and the sleeve  64 . To release the flow blocking substance  66 , a fluid which will weaken or dissolve the capsules  68  is flowed from the main wellbore  12  and into the wellbore  36  via the fracture  20 . For example, the capsules  68  may be acid soluble and an acid may be flowed from the main wellbore  12 , through the fracture  20 , and into the wellbore  36  to dissolve the capsules  68  and release the flow blocking substance  66  therefrom.  
         [0030]    If it is desired to block fluid from flowing from the wellbore  36  to the wellbore  12  via the fracture  20 , such fluid flow may be used to convey the flow blocking substance  66  to the fracture, where it will plug the intersection between the wellbore  36  and the fracture and block subsequent flow therethrough. If it is desired to block fluid from flowing from the wellbore  36  to the formation  14 , such fluid flow may be used to convey the flow blocking substance  66  to the wall of the formation  14  surrounding the wellbore  36 . Note that the outer housing  62  of the apparatus  60  may be perforated in addition to, or as an alternative to, perforation of the inner sleeve  64 .  
         [0031]    Referring additionally now to FIG. 3, the method  10  is depicted schematically from a top view. Note that additional wellbores  70 ,  72  are shown as having been drilled into the formation  14  (not shown in FIG. 3), so that the wellbores  36 ,  44 ,  70 ,  72  are arrayed about the main wellbore  12 . The wellbores  70 ,  72  also intersect fractures extending outward from the main wellbore  12 , but these fractures and the fractures  18 ,  20  are not shown in FIG. 3 for illustrative clarity.  
         [0032]    A sensor/transmitter  56  is positioned in each of the wellbores  36 ,  44 ,  70 ,  72  and is in communication with the receiver/transmitter  58  in the main wellbore  12 . In this manner, the sensor/transmitters  56  form an array about the main wellbore  12  and may be used to present a two dimensional view of the properties of fluids flowing from the formation  14  via the wellbores  36 ,  44 ,  70 ,  72  into the main wellbore. For example, an encroaching “sweep” of water  74  may be indicated by sensors  56  in the wellbores  36 ,  70 . It will be readily appreciated that a three dimensional view of the properties of fluids flowing from the formation  14  via the wellbores  36 ,  44 ,  70 ,  72  into the main wellbore  12  may be accomplished by positioning the sensor/transmitters  56  at different depths in the formation  14 , such as by drilling the wellbores  36 ,  44 ,  70 ,  72  at different depths, or positioning the sensor/transmitters  56  at different depths in their respective wellbores.  
         [0033]    Referring additionally now to FIG. 4, another method  80  embodying principles of the present invention is representatively and schematically illustrated. In the method  80 , a main wellbore  82  is drilled into a formation  84 . The wellbore  82  may extend generally horizontally in the formation  84  as depicted in FIG. 4, but such is not necessary in keeping with the principles of the present invention. Fractures  86 ,  88  are formed extending outward from the wellbore  82  into the formation  84 . Alternatively, the fractures  86 ,  88  may be portions of a single fracture extending outward from the wellbore  82 .  
         [0034]    Another wellbore  90  is drilled into the formation  84  so that it intersects the fracture  88 . Preferably, the wellbore  90  intersects the fracture at an angle other than ninety degrees. A plug  92  is installed in the wellbore  90  to prevent fluid flow from the formation  84  upwardly through the wellbore  90 .  
         [0035]    A branch or lateral wellbore  94  is drilled outward from the parent wellbore  90 . The wellbore  94  is drilled into the formation  84  so that it intersects the fracture  86 , preferably at an angle other than ninety degrees. A plug  96  is installed in the wellbore  94  to prevent fluid flow from the formation  84  upwardly through the wellbore  94 .  
         [0036]    Note that the wellbores  90 ,  94  are downwardly inclined in the formation  84  and are downwardly inclined at their intersections with the fractures  86 ,  88 , respectively. This downward inclination is not necessary in keeping with the principles of the present invention, but it may provide gravity drainage of fluid from the wellbores  94 ,  90  to the wellbore  82 . The wellbores  90 ,  94  may also have filtering devices, such as slotted liners, well screens, etc., installed therein to filter fluid flow from the formation  84  into the respective wellbores.  
         [0037]    Referring additionally now to FIG. 5, another method  100  embodying principles of the present invention is representatively and schematically illustrated. The method  100  is similar in many respects to the method  80  described above, but differs in at least one significant respect in that an injection operation is performed. A main wellbore  102  is drilled, and then a production wellbore  104  and an injection wellbore  106  are drilled extending outwardly from the main wellbore and into a formation  108 . Of course, the wellbores  104 ,  106  could be branches of the main wellbore  102 , the wellbore  106  could be a branch of the wellbore  104 , or the wellbores could be drilled in any other manner, without departing from the principles of the present invention.  
         [0038]    Fractures  110 ,  112  are formed extending outward from the wellbore  104  and fractures  114 ,  116  are formed extending outward from the wellbore  106 . The fractures  110 ,  112 ,  114 ,  116  are intersected by wellbores  118 ,  120 ,  122 ,  124 , respectively, drilled into the formation  108 . It will be readily appreciated that a fluid (indicated in FIG. 5 by arrow  126 ), such as liquid water, steam, etc., may be injected into the formation  108  from the wellbore  106  via the fractures  114 ,  116  and the wellbores  122 ,  124 . Fluid (indicated in FIG. 5 by arrow  128 ), such as hydrocarbons, etc., may in response be produced through the wellbore  104  from the wellbores  118 ,  120  and fractures  110 ,  112 .  
         [0039]    Referring additionally now to FIG. 6, another method  140  embodying principles of the present invention is representatively and schematically illustrated. In the method  140 , a production wellbore  142  is drilled, but it may not intersect a formation  144  from which it is desired to produce fluids. Instead, a second wellbore  146  is drilled into the formation  144  and then drilled to intersect a fracture  148  extending outward from the wellbore  142 .  
         [0040]    Preferably, the wellbore  146  intersects the fracture  148  at an angle other than ninety degrees, such as an acute angle. To aid in guiding the wellbore  146  to intersect the fracture  148 , a radioactive source  150  may be deposited in the fracture. For example, the radioactive source  150  may be mixed with proppant and flowed into the fracture  148  when it is created in a fracturing operation in the wellbore  142 . Thus, the wellbore  146  may be drilled toward the radioactive source  150 , thereby guiding the wellbore to intersect the fracture  148 .  
         [0041]    It may now be fully appreciated that the method  140  provides a way to produce fluids from the formation  144  through the wellbore  142 , even though the wellbore may not intersect the formation. This may be beneficial in situations where production via the wellbore  146  to the earth&#39;s surface is hazardous or uneconomical, such as when an area of subsidence  152  overlies the formation  144 .  
         [0042]    Note that, in the method  140 , as well as any of the other methods described above, the formation  144  may also be fractured from the drainage wellbore  146  to improve fluid flow between the formation and the wellbore.  
         [0043]    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. 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.