Abstract:
A system and method for detecting screen-out using a fracturing valve for mitigation is disclosed herein. The fracture method can comprise fracturing a well using a fracturing valve, while a downhole pressure is less than a predetermined threshold. The method can also comprise actuating by automated process the fracturing valve from a fracturing position to a nonfracturing position upon detecting by a pressure sensor in the wellbore that the downhole pressure has reached said predetermined threshold.

Description:
PRIORITY 
       [0001]    This application is a continuation application of utility application Ser. No. 13/624,981 filed Sep. 24, 2012. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to a system and method for detecting screen-out using a fracturing valve for mitigation. 
         [0003]    Over the years, hydraulic fracturing with multiple fractures has been a popular method in producing gas and oil from a horizontal wells. Hydraulic fracturing involves injecting a highly pressurized fracturing fluid through a wellbore, which causes rock layers to fracture. Once cracks are formed, proppants are introduced to the injected fluid to prevent fractures from closing. The proppants use particulates, such as grains of sands or ceramics, which are permeable enough to allow formation fluid to flow to the channels or wells. 
         [0004]    However, during a fracturing operation, major problems, such as screen-outs, can occur. Screen-outs happen when a continued injection of fluid into the fracture requires pressure beyond the safe limitations of the wellbore and surface equipment. This condition takes place due to high fluid leakage, excessive concentration of proppants, and an insufficient pad size that blocks the flow of proppants. As a result, pressure rapidly builds up. Screen-out can disrupt a fracturing operation and require cleaning of the wellbore before resuming operations. A delay in one fracturing operation can cause disruption on the completion and production of subsequent fractures. 
         [0005]    The consequences of screen-out can depend on the type of completion used in fracturing. One of the common completions used for horizontal well is open hole liner completion. This involves running the casing directly into the formation so that no casing or liner is placed across the production zone. This method for fracturing can be quick and inexpensive. Open hole liner completion can also include the use of a ball-actuated sliding sleeve system, commonly used for multistage fracturing. However, if screen-out occurs near the toe of a horizontal wellbore, the small openings of the ball seats can make it difficult to use a coiled tubing or a workover string to wash the proppants out. One initial solution can include opening the well and waiting for the fracturing fluid to flow back. However, if the flow back does not occur, the only solution left is to mill out the completion and apply a different completion scheme to the wellbore. As a result, the entire operation can cause delays and higher expenses. 
         [0006]    Another known completion method is a plug-and-perforate system, which is closely similar to the open hole liner system. This method involves cementing the liner of the horizontal wellbore and is often performed at a given horizontal location near the toe of the well. The plug and perforate method involves the repetitive process of perforating multiple clusters in different treatment intervals, pulling them out of a hole, pumping a high rate stimulation treatment, and setting a plug to isolate the interval, until all intervals are stimulated. The consequences of screen-out in this method may not be as severe compared to the ball-actuated sliding sleeve system, since the well can be accessed with coiled tubing to wash the proppants out. 
         [0007]    Yet, another method used has included cemented liner completions with restricted entry. Cemented liner completions with restricted entry involve controlling fluid entry into a wellbore. This method provides a cemented liner or casing comprising a cluster of limited openings that can allow fluid communication between a region of a wellbore and the formation. However, a poor connection between the well and the formation often results in screen-out. Thus, screen out encountered in each completion method adds costs and causes disruption in fracturing operations and production. 
         [0008]    As such, it would be useful to have an improved system and method for detecting screen-out using a fracturing valve for mitigation. 
       SUMMARY 
       [0009]    This disclosure relates to a system and method for detecting screen-out using a fracturing valve for mitigation. The fracture method can comprise fracturing a well using a fracturing valve, while a downhole pressure is less than a predetermined threshold. The method can also comprise actuating by automated process the fracturing valve from a fracturing position to a non-fracturing position upon detecting by a pressure sensor in the wellbore that the downhole pressure has reached said predetermined threshold. 
         [0010]    The fracturing valve system can comprises a base pipe comprising an insert port capable of housing a stop ball, as the stop ball can be insertable partially within the chamber of the base pipe. Additionally, the system can comprise a sliding sleeve comprising a first sleeve with an inner surface having an angular void and a large void. The first sleeve can be maneuverable into multiple positions, In a first position, an angular voidcan rest over the insert port, preventing the stop ball from exiting the chamber of the base pipe. In a second position, where the large void rests over the insert port, the stop ball can be capable of exiting the chamber of the base pipe to enter the large void. 
         [0011]    Additionally, a method of detecting screen out using a fracturing valve is disclosed. Specifically, the method can comprise injecting a fracturing fluid into said fracturing valve, which comprises a base pipe and a sliding sleeve. The base pipe can comprise one or more insert ports each capable of housing a stop ball. The sliding sleeve can comprise an inner surface with an angular void and a large void, as the sliding sleeve initially in a first position, where the angular void rests over said insert port. The method can further comprise applying a first force on the frac ball by the fracturing fluid, applying a second force on one or more stop balls by the frac ball, and applying a third force against the angular void by the stop balls. Furthermore, the method can comprise biasing the sliding sleeve, at least in part by a third force, toward a second position, where a large void rests over the insert port. Thus, the stop ball can be capable of exiting the chamber of the base pipe to enter the large void. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  illustrates a side view of a base pipe. 
           [0013]      FIG. 1B  illustrates a front view of a base pipe. 
           [0014]      FIG. 1C  illustrates a cross sectional view of a base pipe. 
           [0015]      FIG. 2A  illustrates a sliding sleeve. 
           [0016]      FIG. 2B  illustrates a front view of a sliding sleeve. 
           [0017]      FIG. 2C  illustrates a cross sectional view of a sliding sleeve. 
           [0018]      FIG. 2D  illustrates a cross sectional view of a sliding sleeve that further comprises a fixed sleeve, and an actuator. 
           [0019]      FIG. 3A  illustrates a peripheral view of outer ring. 
           [0020]      FIG. 3B  illustrates a front view of an outer ring. 
           [0021]      FIG. 4A  illustrates a valve casing. 
           [0022]      FIG. 4B  illustrates a fracturing port of a valve casing. 
           [0023]      FIG. 4C  illustrates a production slot of a valve casing. 
           [0024]      FIG. 5  illustrates a fracturing valve in fracturing mode. 
           [0025]      FIG. 6A  illustrates an embodiment of an impedance device. 
           [0026]      FIG. 6B  illustrates another embodiment of an impedance device. 
           [0027]      FIG. 7  illustrates fracturing valve in production mode. 
           [0028]      FIG. 8A  illustrates a graph showing a breakage point of a string. 
           [0029]      FIG. 8B  illustrates a close up view of a fracturing valve in a fracturing mode. 
           [0030]      FIG. 8C  illustrates a graph showing a breakage point of a segmented embodiment of an impedance device. 
           [0031]      FIG. 8D  illustrates another embodiment of fracturing valve in fracturing mode. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Described herein is a system and method for detecting screen-out using a fracturing valve for mitigation. The following description is presented to enable any person skilled in the art to make and use the invention as claimed and is provided in the context of the particular examples discussed below, variations of which will be readily apparent to those skilled in the art. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual implementation (as in any development project), design decisions must be made to achieve the designers&#39; specific goals (e.g., compliance with system- and business-related constraints), and that these goals will vary from one implementation to another. It will also be appreciated that such development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the field of the appropriate art having the benefit of this disclosure. Accordingly, the claims appended hereto are not intended to be limited by the disclosed embodiments, but are to be accorded their widest scope consistent with the principles and features disclosed herein. 
         [0033]      FIG. 1A  illustrates a side view of a base pipe  100 . Base pipe  100  can be connected as a portion of a pipe string. In one embodiment, base pipe  100  can comprise cylindrical material with different wall openings and/or slots. Base pipe  100  wall openings can comprise an insert port  101 , a fracturing port  102 , and/or a production port  103 . Insert port  101  can be made of one or more small openings in a base pipe  100 . Fracturing port  102  can also comprise one or more openings. Furthermore, production port  103  can be a plurality of openings in base pipe  100 . 
         [0034]      FIG. 1B  illustrates a front view of base pipe  100 . Base pipe  100  can further comprise a chamber  104 . Chamber  104  can be a cylindrical opening or a space created inside base pipe  100 . Chamber  104  can allow material, such as fracturing fluid or hydrocarbons, to pass through.  FIG. 1C  illustrates a cross-sectional view of a base pipe  100 . Each wall opening discussed above can be circularly placed around base pipe  100 . 
         [0035]      FIG. 2A  illustrates a sliding sleeve  200 . Sliding sleeve  200  can be connected to a fixed sleeve  205  by an actuator  206 , while sliding sleeve  200  can be in line with an outer ring  207 . In one embodiment, sliding sleeve  200  can be a cylindrical tube that can comprise fracturing port  102 . Thus, fracturing port can have a first portion within base pipe  100  and a second portion within sliding sleeve  200 . 
         [0036]      FIG. 2B  illustrates a front view of a sliding sleeve  200 . Sliding sleeve  200  can further comprise an outer chamber  201 . In one embodiment, outer chamber  201  can be an opening larger than chamber  104 . As such, chamber  201  can be large enough to house base pipe  100 . 
         [0037]      FIG. 2C  illustrates a cross-sectional view of a sliding sleeve  200 . Sliding sleeve  200  can comprise a first sleeve  202  and a second sleeve  203 . First sleeve  202  and second sleeve  203  can be attached through one or more curved sheets  204 , as the spaces between each curved sheet  204  can define a portion of fracturing port  102 . Inner surface of first sleeve  202  can have void  208  comprising an angular void  208   a    208   a  within the inner surface created by a gradually thinning wall of first sleeve  202 , and a large void  208   b . In one embodiment, void  208  can extend radially around the complete inner diameter of base pipe  100 , partially around inner diameter. In another embodiment, voids  208  can exist only at discrete positions around the inner radius of first sleeve  202 . If completely around inner diameter, the ends of inner surface can have a smaller diameter than the void  208 . Angular void  208   as    208   a  can each be above insert port  101  when sliding sleeve is in fracturing mode. 
         [0038]      FIG. 2D  illustrates a cross sectional view of a sliding sleeve  200  that further comprises a fixed sleeve  205 , and an actuator  206 . In one embodiment, actuator  206 , can be a biasing device. In such embodiment, biasing device can be a spring. In another embodiment, actuator can be bidirectional and/or motorized. In one embodiment, second sleeve  203  of sliding sleeve  200  can be attached to fixed sleeve  205  using actuator  206 . In one embodiment, sliding sleeve  200  can be pulled towards fixed sleeve  205 , thus compressing load actuator  206  with potential energy. Later, actuator  206  can be released, or otherwise instigated, by pushing sliding sleeve  200  away from fixed sleeve  205 . 
         [0039]      FIG. 3A  illustrates a peripheral view of outer ring  207 .  FIG. 3B  illustrates a front view of an outer ring  207 . In one embodiment, outer ring  207  can be a solid cylindrical tube forming a ring chamber  301 , as seen in  FIG. 3B . In one embodiment, outer ring  207  can be an enclosed solid material forming a cylindrical shape. Ring chamber  301  can be the space formed inside outer ring  207 . Furthermore, ring chamber  301  can be large enough to slide over base pipe  100 . 
         [0040]      FIG. 4A  illustrates a valve casing  400 . In one embodiment, valve casing  400  can be a cylindrical material, which can comprise fracturing port  102 , and production port  103 .  FIG. 4B  illustrates a fracturing port of a valve casing. In one embodiment, fracturing port  102  can be a plurality of openings circularly placed around valve casing  400 , as seen in  FIG. 4B .  FIG. 4C  illustrates a production slot of a valve casing. Furthermore, production port  103  can be one or more openings placed around valve casing  400 , as seen in  FIG. 4C . 
         [0041]      FIG. 5  illustrates a fracturing valve  500  in fracturing mode. In one embodiment, fracturing valve  500  can comprise base pipe  100 , sliding sleeve  200 , outer ring  207 , and/or valve casing  400 . In such embodiment, base pipe  100  can be an innermost layer of fracturing valve  500 . A middle layer around base pipe  100  can comprise outer ring  207  fixed to base pipe  100  and sliding sleeve  200 , in which fixed sleeve  205  is fixed to base pipe  100 . Fracturing valve  500  can comprise valve casing  400  as an outer later. Valve casing  400  can, in one embodiment, connect to outer ring  207  and fixed sleeve  205 . In a fracturing position, fracturing port  102  can be aligned and open, due to the relative position of base pipe  100  and sliding sleeve  200 . 
         [0042]    Fracturing valve  500  can further comprise a frac ball  501  and one or more stop balls  502 . For purposes of this disclosure, stop ball  501  can be any shaped object capable of residing in fracturing valve  500  that can substantially prevent frac ball  501  from passing. Further frac ball  501  can be any shaped object capable of navigating at least a portion of base pipe  100  and, while being held in place by stop balls  502 , restricting flow. In one embodiment, stop ball  502  can rest in insert port  101 . At a fracturing state, actuator  206  can be in a closed state, pushing stop ball  502  partially into chamber  104 . In such state, frac ball  501  can be released from the surface and down the well. Frac ball  501  can be halted at insert port  101  by any protruding stop balls  502 , while fracturing valve  500  is in a fracturing mode. As such, the protruding portion of stop ball  502  can halt frac ball  501 . In this state, fracturing port  102  will be open, allowing flow of proppants from chamber  104  through fracturing port  102  and into a formation which allows fracturing to take place. 
         [0043]      FIG. 6A  illustrates an embodiment of an impedance device. Impedence device can counteract actuator  206 , in an embodiment where actuator  206  is a biasing device, such as spring. In one embodiment, an erosion device in the form of a string  601  can be an impedance device. In such embodiment, string  601  can be made of material that can break, erode, or dissolve, for example, when it is exposed to a strong force, or eroding or corrosive substance. A string holder  602  can be a material, such as a hook or an eye, attached onto sliding sleeve  200  and base pipe  100 . String  601  can connect sliding sleeve  200  with base pipe  100  through string holder  602 . While intact, string can prevent actuator  206  from releasing. Once the string is broken, broken, actuator  206  can push sliding sleeve  601 . One method of breaking string  601  can comprise pushing a corrosive material reactive with string through fracturing port, deteriorating string  601  until actuator  206  can overcome its impedance. 
         [0044]      FIG. 6B  illustrates another embodiment of an impedance device. In such embodiment, string  601  can comprise a first segment  601   a  and a second segment  601   b . String holder  602  can connect first segment  601   a  with base pipe  100 , while second segment  601   b  can attach to string holder  602  that connects with sliding sleeve  200 . In such embodiment, any axial force applied, to sliding sleeve can put a tensile force on the impedence device. First segment  601   a  can be made of material that can be immune to a corrosive or eroding substance, but designed to fail at a particular tensile force, while second segment  601   b  can be made of material reactive to corrosive or erodable substance, that will fail at an increasingly lower tensile force. Such failure force gradient of second segment can be initially be higher than a failure force related to first segment  601   a , but eventually decrease below it over time. As such, first segment  601   a  can be a portion of impedance device that can break when exposed to failure force, regardless of the extent to which second segment  601   b  has been dissolved. 
         [0045]      FIG. 7  illustrates fracturing valve  500  in production mode. As sliding sleeve  200  is pushed towards outer ring  207  by actuator  206 , fracturing port  102  can close, and production port  103  can open. Concurrently, second force by frac ball  501  can push stop balls  502  back into the inner end of first sleeve  202 , which can further allow frac ball  501  to slide through base pipe  100  to another fracturing valve  500 . Once production port  103  is opened, extraction of oil and gas can start. In one embodiment, production ports can have a check valve to allow fracturing to continue downstream without pushing fracturing fluid through the production port. 
         [0046]      FIG. 8A  illustrates a graph  800  showing a breakage point  801  of string  601 . As mentioned in the discussion of  FIG. 6A , string  601  can be made to dissolve over the course of the fracturing. In graph  800 , x-axis can signify time, while y-axis can signify force. Graph  800  displays a line graph for a string strength line  802  and a string tensile force line  803 . String strength line  802  can represent force required to break string  601  over time. String strength line  802  can be a straight line that starts high but decreases over time. The string strength line  802  indicates that string  601  can slowly dissolve or erode, as it gets thinner from the injected corrosive material in fracturing valve  500 . Thus, the amount of force required to break string  601  can decrease over time. String tensile force line  803  can be the tensile force on string  601 . The tensile force can be the force of the actuator  206  and the axial force of stop balls  501  related to the pressure of the well. When in fracturing state, a highly pressurized fracturing fluid can be injected into the fracturing port  102  and into a formation. Once the formation fractures, the pressure on frac ball  501  can level or drop off. Thus, more fracturing fluid can be injected into the formation with little change in pressure. After a period of time, the formation can fill up and no longer take fracturing fluid. At that point, pressure begins increasing again as more fluid is pushed into wellbore. The changes in pressure in the wellbore directly affect the tension on the line, as shown in string tensile force line  803 . The point where string strength line  802  and string tensile force line  803  meet is a breakage point  801  for string  601 . 
         [0047]    To prevent screen-out, in one embodiment, a pressure sensor can be placed down well. Pressure sensor can be capable of reading pressure or determining when pressure reaches a threshold. Once threshold point is reached, pressure sensor can send signal to a computer, which can control sliding sleeve  200  by actuator  206 . As a result, computer can cause sliding sleeve  200  to actuate as a result of commands to actuator  206 . In one embodiment, actuator  206  can comprise a motor, which can generate the necessary force to move sliding sleeve  200  from a fracturing position to a production position. 
         [0048]      FIG. 8B  illustrates a close up view of fracturing valve  500  in fracturing mode. Wellbore pressure will push frac ball  501  down into chamber  104  by a first force  804 . As frac ball  501  rests against stop ball  502 , the pressure on frac ball  501  can cause stop ball  502  to push towards sliding sleeve  200 . Frac ball  501  can push stop ball  502  with a second force  805 , causing stop ball  502  to go into the angular inner wall of sliding sleeve  202 . A third force  806  of stop ball  502  can build up against the wall of angular void  208   a . The result is a radial force  808  in the radial direction of sliding sleeve  202 , and an axial force  807  in an axial direction of base pipe  100 , toward outer ring  207 . The force in either direction depends on the angle of the angular void  208   a . A greater angle produces more force in the axial direction. 
         [0049]    As the force on actuator  206  and the axial force  807  that ultimately results from the pressure on frac ball  501  is building, the axial force needed to break string  601  decreases due to string deterioration. As such, the point where string strength line  802  and string tensile force line  803  cross is breakage point  801 . At breakage point  801 , string  601  finally gives in to the tensile force and breaks. When over insert port, angular void  208   a    208   a  can prevent stop balls from exiting chamber  104 . When large void  208   b  is over insert port, it can allow stop balls to exit chamber  104 . 
         [0050]      FIG. 8C  illustrates a graph  804  showing breakage point  801  for a segmented embodiment of string  601 . As discussed in  FIG. 6B , string  601  can break at a required force or through exposure to corrosive substance. In graph  804 , string strength line  802  can start with a flat horizontal line that eventually or gradually decreases over time. First segment  601  a can be represented with the flat string strength line  802  that shows first segment  601   a  is breakable when a certain amount of force is applied. A decrease in strength of string  601  in strength line  802  can relate to second segment  601   b  of string  601  dissolving to a point where it eventually becomes weaker than first segment. When in fracturing mode, the increase and decrease in pressure can also affect the tension on string  601 . As such, breakage point  801  is where string strength line  802  and string tensile force line  803  meets. 
         [0051]      FIG. 8D  illustrates another embodiment of fracturing valve  500  in fracturing mode. In such embodiment, inner surface of first sleeve  202  can have a curved void  208  within the inner surface, radially creating an exterior curvature of first sleeve  202 . In fracturing mode, curved void  208  can be above insert port  101 . The slope within the inner surface of first sleeve  202  can cause stop ball  502  to overcome the force on string  601  easier. A steep angle creates more force in the axial direction. As such, frac ball  501  can require less force to push stop ball  502  into the curved inner wall of sliding sleeve  202 . 
         [0052]    Various changes in the details of the illustrated operational methods are possible without departing from the scope of the following claims. Some embodiments may combine the activities described herein as being separate steps. Similarly, one or more of the described steps may be omitted, depending upon the specific operational environment the method is being implemented in. It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”