Abstract:
A drop ball for use in wellbore activities, such as wellbores in oil and gas drilling, completion and/or production activities comprising a generally spherical body, the spherical body carrying at least one marker, which contains and/or can determine at least one parameter related to the drop ball, the wellbore and/or activities being conducted in the wellbore.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from application Ser. No. 61/122,866, filed Dec. 16, 2008, the disclosure of which is incorporated herein by reference for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to drop balls for use in wellbore activities, as for example, completion systems and more particularly to completion systems for accurate placement of stimulation treatments in multiple zone wells. 
       BACKGROUND OF THE INVENTION 
       [0003]    In typical wellbore operations, various treatment fluids may be pumped into the well and eventually into the formation to restore or enhance the productivity of the well. For example, a non-reactive “fracturing” fluid or “frac” fluid may be pumped into the wellbore to initiate and propagate fractures in the formation thus providing flow channels to facilitate movement of the hydrocarbons to the wellbore so that the hydrocarbons may be pumped from the well. In such fracturing operations, the fracturing fluid is hydraulically injected into a wellbore penetrating the subterranean formation and is forced against the formation strata by pressure. The formation strata is forced to crack and fracture and a proppant is placed in the fracture by movement of a viscous fluid containing proppant into the crack in the rock. The resulting fracture, with proppant in place, provides improved flow of the recoverable fluid, i.e., oil, gas or water, into the wellbore. In another example, a reactive stimulation fluid or “acid” may be injected into the formation. Acidizing treatments of the formation results in dissolving materials in the pore spaces of the formation to enhance production flow. 
         [0004]    Currently, in wells, especially horizontal or lateral wells, with multiple production zones, it may be necessary to treat various formations in a multi-stage operation requiring repeated trips downhole. Each trip generally consists of isolating a single production zone and then delivering the treatment fluid to the isolated zone. Since multiple trips downhole are required to isolate and treat each zone, the completion operation may be very time consuming and expensive. 
         [0005]    To overcome the above disadvantages with multi-trip zone isolation and treatment, as well as other problems, e.g. the viability of cement in long lateral wells, new techniques and apparatus have been developed which effectively provide a substantially intervention-free method and eliminates many of the disadvantages of prior methods. 
         [0006]    One such system makes use of a series of sleeves/valves and packers spaced along the length of the lateral well allowing the isolation of multiple zones and their selective fracturing in a continuous operation. Typically the sleeves/valves are selectively opened by dropping balls from the surface to land on approximately sized sleeves to operate or open each sleeve at the appropriate time. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0007]    A typical workstring used in techniques for multi-zone completions employs a float shoe and a landing collar assembly at the toe. This arrangement controls fluid through the ID of the workstring as it is being manipulated in the wellbore. Typically, positioned along the workstring as in the horizontal section of a well, are a series of sleeves/valves which can be manipulated/shifted by drop-ball technology. As noted, at the bottom of the completion string is the float shoe followed by a landing collar which is then followed by a hydraulically activated stimulation sleeve and laterally spaced along the workstring the desired number of packers and stimulation sleeves with ball seats installed. In the arrangement, the stimulation sleeves are positioned in order such that the ball seats are ordered from smallest to largest, the smallest seat being closest to the toe of the well. Once the completion string has been positioned such that the stimulation sleeves are located adjacent the zones to be treated, after a series of steps well known to those skilled in the art, the stimulation method can be commenced. For example, after treatment of the first zone, i.e., the zone closest to the toe of the well, a first ball is dropped at the beginning of the pad of the next zone&#39;s treatment and is pumped down to land on the corresponding ball seat. When the ball lands, the zone that was just treated is now isolated, the stimulation sleeve is opened and the treatment of the next zone started. The process continues, dropping the next sized ball for each stage, until all desired zones have been treated. Lastly, the balls are returned back to the surface by flowing into the well. If for some reason the balls do not return or if full ID access is desired, the ball/ball seats that are attached to the stimulation sleeves can be drilled or milled. 
         [0008]    As noted above, in using the ball drop technology, the balls are of different sizes and it is important that the balls be dropped in the appropriate order. 
         [0009]    Typically, the balls used in the drop ball techniques are made of plastics, such as phenolics, but can be made of composite materials. 
         [0010]    In one aspect of the present invention, there is provided a drop ball for use in wellbore activities, comprising a generally spherical body, the spherical body carrying at least one identifier that has and/or can acquire information that can be accessed to determine at least one parameter related to the ball, a portion of the ball and/or at least one condition related to said wellbore. 
         [0011]    According to another aspect of the present invention, there are provided drop balls which contain, carry or include tags, markers, or identifiers, each of which in a given ball has a unique identifier that can be scanned, read or otherwise determined using various techniques; e.g., various mobile devices permitting users to retrieve or leave digital information related to the drop ball and/or wellbore condition. For example, there exists tags or markers that can contain multiple layers of information in very small particles, e.g. smaller than the diameter of a human hair. These types of markers, identifiers, etc., can be incorporated into the drop balls of the present invention and, since they contain information related to various parameters of the drop ball and/or can “read,” “determine” or “identify” at least one downhole condition, are ideally suited to be “read,” “identified,” or “detected” by devices; e.g., mobile devices, such as handheld scanners which can be electronic, optical, etc. 
         [0012]    According to a specific aspect of the present invention, there are provided drop balls which contain one or more RFID readable chips embedded therein. The RFID chips, which can be active or passive, can contain information such as the size of the ball and other information which is important to both inject the balls during the procedure as well as determine the status of conditions downhole as the drop ball(s) or cuttings therefrom return. 
         [0013]    In one embodiment, it is contemplated that the drop balls of the present invention containing the RFID chips would generally have a plurality of such chips containing the same information such that if one of the chips of a given ball were destroyed, the information needed would still be available on one of the other chips in that ball or fragments of the ball. While active RFID chips could be employed, generally speaking, the RFID chips contemplated by the present invention would be passive, i.e. while not containing a battery the chips will be charged with enough energy to communicate with an RFID reader and provide the reader with the data stored on the tag. 
         [0014]    The use of RFID chips as described above is desirable for many reasons, not the least of which being that because of the properties of radio frequency propagation, the RFID chips or tags do not need to be at line-of-sight with the reader. 
         [0015]    As noted above, the tags or markers contained in the drop balls of the present invention can contain in transcript, digitized information such as the size of the ball, temperature and pressure limitations on the use of the ball, downhole conditions, etc. Indeed, it is contemplated that the tags or markers could be encrypted or encoded to detect or determine certain conditions in the subsurface and/or downhole environment and store that data such that when the drop ball or any portion thereof was returned to the surface, that data could be employed to advise the operators of corrective actions that may be necessary. 
         [0016]    It is further contemplated that the tags or markers, including the RFID tags, would be dispersed throughout the drop balls such that in cases when it was necessary to mill or drill out the drop balls subsurface, one or more returning fragments from the ball would still contain all of the information stored on the marker, originally, or acquired in the downhole environment. It is contemplated that as technology advances, the tags or markers for use in the drop balls of the present invention may ultimately be nano particles facilitating their uniform incorporation into the drop balls. 
         [0017]    The drop balls of the present invention can be made of any number of materials. In the case of the use of RFID chips, the limitation on the compositional makeup of the body of the ball is that the material is radio frequency transparent such that the RFID chip can be easily read. Accordingly, plastic such as phenolics, nylon, polyurethane, etc., could be employed. Additionally, composites could be employed to make the body of the drop ball, such composites including materials such as plastics reinforced with fiberglass, carbon fibers, metallic fibers, etc. It is also contemplated that the drop balls could be made entirely of metallic materials and the RFID encased in radio frequency transparent materials which could then be secured into recesses extending from the surface of the ball.